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DESIGN OF SOLAR POWERED ABSORPTION AIR-CONDITIONING SYSTEM.-....r
A DISSERTATION
Submitted in partial fulfilment of the requirements for the award of the degree
of
MASTER OF ENGINEERING,- ` '" •;; 1 t o ~2~6436' ,~,
in tic y
MECHANICAL ENGINEERING `, a f
(With Specialization in Thermal Engineering)' •* ~~~~,~g ~
by
• RAJIV KAY. 'd"l.1 TSity of Roo 1, oe Roc 1_ Ccrtjfjo i;.
i;11y f SO:
- s ..-.... ... ,.....,, - i
No. f ' / `5 (D-:':::
DEPARTMENT OF MECHANICAL 'AND- DUSTRIAL- ENGINEERING UNIVERSITY OF ROORKEE ROORKEE-247667(INDIA)
JANUARY, 1994
CANDIDATE'S DECLARATION
I.h t by certify that the work which i h@ :ink pr-@®@nt@d in
this thesis titled "DESIGN OF SOLAR POWERED ABSORPTION AIR
CONDITIONING SYSTEM" in the partial fulfilment of the
requirement for the award of degree of Master of Engineering in
MECHANICAL AND INDUSTRIAL ENGINEERING DEPARTMENT with
specialization in Thermal Engineering, submitted in the
Department of Mechanical & Industrial Engineering, University of
Roorkee, Roorkee, India, is an authentic record of my own work
carried out for a period of about 8 months during the period
between June. 93 to Jan. 94, under the supervision of
Dr.Bhupinder Singh, Reader, Department of Mechanical and
Industrial Engineering, University. of Roorkee, Roorkee,
India.The matter embodied in this thesis has not been submitted
by me for the award of any other degree or diploma.
Date: 31st January 1994
(RAJIV KAUL)
Certificate
This is to certify that the above statement made by the
candidate is correct to the best of my knowledge.
( .BHUPI77N)Ri SINGH) Ph.D.
Reader Mech. & Ind. Engg. Dept.
Date: UOR,ROORKEE-247 667
T
ABSTRACT
Due to energy saving consciousness and to reduce the
risk of ecological balance, now-a-days there is considerable
interest in the development of Absorption air conditioning system
powered by renewable energy resources. Also, in india there are
many,backward areas which unfortunately even today have no proper
electric supply but Air conditioning requirements exist in these
region for Hospitals, and for storing medicines, perishable such
as milk and other products.
This necessitates the development- of vapour absorption
air conditioning system. Vapour Absorption system is heat
operated system. The heat may be supplied by Biogas, LPG or Solar
Energy. In the present work, a design and performance of a solar
power air conditioning system is reported. This is a design
study on the Vapour Absorption system. Parameters like generator
temperature, condenser, Absorption and Evaporator temperature are
varied and effect of these variations on the performance of the
system is studied. Effect of one parameter on other for the
maximum value of COP is also studied. On the basis of above study
it is found that generator temperature for acceptable performance
increases within the increase of condenser and Absorber
temperature. For high temperature regions generator temperature
should be around 100°C, so for these regions solar powered
Absorption system is most suitable. COP is taken as the
optimization criterion, an the basis of above study, optimum
L
design conditions are selected.
The following are the specifications of the solar
powered vapour Absorption system.
System : Aqua -Ammonia Absorption System.(continuous)
Space size -- 25 x 16 x 5 m
cooling capacity - 20 TR
Evaporator Temperature - -2°C
Required Cabin condition - 26.7°C & 559: RH,
No. of person in space - 30.
Condenser Temperature - 40°C
Absorber Temperature - 300C
Generator Temperature - 95°C
Generation period - 2, hours
Operating period - B hours
Energy Input - 282.9 kW
COP - 0.278
Circulation of Ammonia - 4.3 kg/min
Evaporator capacity - 70.33 kW
Alternative, heating source - LPG/Biogas
Condenser capacity - 97.6 kW
Type of Generator - Solar heated
Type of Condenser - shell and tube type
Type of Rectifier - air cooled cuperative type
Reliability - Excellent
Life of unit - 20 yrs
Economic Viability
With the present investment, cast and energy prices,
solar powered vapour Absorption air conditioning system is
economically viable in remote areas. However, with reduction in
maintenance cost and reliable operation for long period, the
system can be designed for automatic operation, without requiring
any attention from the user of the system.
5
ACVNOWLEDGEMENTS
Thanks are expressed sincerely to Dr. Bhupinder Singh,
Reader, Department of Mechanical and Industrial. Engineering, for
suggesting the topic, invaluable guidance, and inspiration at
various stges of work. His keen interest and effect in planning
the work in this form is gratefully acknowledged as he devoted
his valuable time in discussions and in critical analysis of this
work.
Thanks are also due to my friends who, directly or
indirectly helped me in the preparation and presentation of this
work.
Dated
(RAJ I V KAUL )
Page No.
Certificate I
Abstract II
Ac know1odg©mont6 V
Contents VI
List of Figures IX
List of Tables XI
Acronym and Nomenclature XII
Chapter - 1 INTRODUCTION 1
1.1 objectives 1
1.2 nnpiiy i.i of t:1►e Problem 1
J..3 1nu►,C►,1. Vnj.nmr nhani.p ion 1iywI.ain a
1.4 logic Op L'aL1,,IJ Uy010 '!
1.5 Choice and ProporLios of Abnorpti.on-
Refrigerant Combination 10
1.6 Operating Variable Affecting Selection
of Combination 12
1.1 Factors Affecting Selection of a Refrigerant 14
1.8 Layout of the Solar Powered air Conditioning
System 16
1.9 Basic Sub-systems 17
1.10 Vapour Absorption Air Conditioning
SynLem (Juinhi►nenh.i 111
VI 4
2.1 Literature Survey & Review 21
2.2 Investigation of Workable System 21
2.3 Refrigerant Absorbent Combination 23
Chapter - 3 DESIGN OF THE SYSTEM 26
3.1 Design of the Vapour Absorption Air
Conditioning System 26
3.2 Problems in the Design of Absorption
Air Conditioning System 26
3.3 Basic Scheme for the Design of the System 27
3.4 Design Conditions 28
3.5 Stream Design 30
3.6 Design of Different Units 33
3.6.2 Ahpni:hoi• Daf4fr l 1Fi
3.6.3 Condemner Design 41
3.6.4 Evaporator Design 44
3.6.5 Design of heat Exchnngor for Weak
and strong Aqua-Ammonia Solution 47
3.6.6 Air, to Water hunt Exchancror. Design 49
3.6.7 Design of rectifier as heat exchanger 53
3.6.6 • dooling Tower Deai jn 55
3.6.9 9ol.nr Insol.ation 57
3.6,10 Snlnation of Expansion Value, Air and
Water Moving dev,I.cnf1, WnL n: pall€ work 5H
VII
4.1 Economic Analysis and Evaluation 61
4.2 The Performance of the System 61
4.3 Elements of Owning Costs 62
4.4 9@r'VjLP life and Amgrtt atton period 63
4.5 Economic Analysis 64
4.6 Annual Operating Coot 67
4.7 Economically Viability 68
4.8 Insulation 68
4.9 Future aspects 69
4.10 Charging the System 70
Chapter - 5. RESULTS AND DISCUSSIONS 71
5.1 General Discussions 71
[5.2 Absorption 8ynt., om P rfornifinc tlt;ucly '11
5.3 Effect of Generator Temperature on the
poefut'm8►nca or Hen lyel.aui '12
51 4# Eff@et of Abootb@r T@mp@Lalur@ 73
5.5 Eff®et of Cont1@n r T@nip®raLur@ 74
5.6 Effect of Evaporator Temperature 75
5.7 Economic Evaluation 78
Flow Chart and Computer Program
REFERENCES
VIII
LIST OF FIGURES
Page No.
Fig 1.1 Aqua-Ammonia Absorption System.
Fig 1.2 Energy Flow in a Simple Absorption System.
Fig 1.3 Complete Lay Out of Vapour Absorption Air Conditioning System
Fig 1.4 Solar Powered Vapour Absorption System
Fig.3.i Flow Diagram of Vapour Absorprion Air.-
Candtioning System
Fig 3.2 Solar powered Vapour Absorption Air- Conditioning System
Fig 3.3 Generator System
Fig 3.4 Absorption Phenomenon
Fig 3.5 Absorber System
Fig 3.6 Shell and Tube Type Condenser
Fig 3.7 Flooded Shell and Tube Type Evaporator
Fig 3.8 Water Air Cross Flow Type Heat Exchanger
Fig 3.9 Heat Exchanger for Weak And Strong Aqua-Ammonia solution
Fig 3.10 Cooling Tower
Fig.3.t2 Float valve
Fig.3.12 Representation of vapour absorption air conditioning system on Psychrometric chart
Fig.3.13 Optimum thickness of insulation
Fig.4.2 Generator Temperature vs COP
Fig.4.2 Generator Temperature vs COP
Fig.4.3 Absorber Temperature vs COP
IX
Fig.4.4 Absorber Temperature vs Ammonia
Distilled/kg water
Fig.4.5 Effect of Absorber Temp. for maximum COP
Fig.4.6 Absorber Temp. vs Initial Concentration
of Ammonia in Aqua Solution
Fig.4.7 Condenser Temp. vs COP
Fig.4.8 Condenser Temp. vs COP
Fig.4.9 Effect of Condenser Temp. on Final Conc. of Aqua-Ammonia Solution
Fig.4.1O Effect of Condenser Temp. for max. COP
Fig.4.11 Evaporator Temp. vs COP
Fig.4.12 Effect of Evaportor Temp.
Fig.4.13 Evaporator Temp. vs Amonia Distilled/kg water
Fig.4.14 Combined Effect of All the Temperatures
N
LIST OF TABLES
Page No
2.1 Refrigerant-Absorbent Combination
3.1 Calculation of TU for Cooling Tower
3.2 Water pipe sizing chart
4.1 Effect of Generator Temperature on the COP of Absorption System
4.2 Effector of Absorber Temperature on Generator Temperature for Maximum COP
4.3 Effect of Condenser Temperature on Generator Temperature for Maximum COP
4.4 Effect of Evaporator Temperature an Generator Temperature for Maximum COP
4.5 Combined Effect of All the Temperature
5.1 Thermophysical Properties of Aqua-ammonia System
5.1(a) Thermal Conductivity of Aqua-€mmonia Solution
5.1(b) Viscosity of Aqua-Ammonia Solution.
5.1(c) Specific heat of Aqua-Ammonia Solution
5.2{d? Specific Volume of Aqua-Ammonia Solution.
ACROtS AND NOMENCLATURE
A/C
AAS
COP
ID
LPG
OD
NTU
LMTD
Air Conditioning
Aqua-Ammonia Solution
Coefficient of Performance
Inner Diameter
Liquefied Petroleum Gas
Outer Diameter
Number of Transfer Unit
Long Mean Temperature Difference
NOMENCLATURE
A
B
C
Cp
d 0
D e
9
G
Sr
h
h 1 ,h 2 K
L
m
Surface Area
Baffle Spacing
Breadth
Specific Heat
Outer Diameter
Equivalent; Diameter
Gravitational Acceleration
Mass Velocity
Greashaff No.
Heat Transfer Coefficient
Enthalpy at Point 1,2
Thermal Conductivity
Length
mass flow rate
2 m
mm
mm
kJ / kg-oK
mm
mm
m/2
kg/s-m2
W/m2-°K
kJ/kg
kJ/kg.oK
m
kg/s
ME
Nu NusseltNo.
P Pressure - Pa.
• P Prandtl No. -r
Q Heat Transfer rate W
• Fie Rognold. Na,-
T Temperature nC-
U Overall heat transfer coefficient W/m2-°K
v Specific volume m3/kg
X Concentration of NH3 in AAS -kg/kg solution
AT Temperature difference • °C
Volume Expansion Criefficient
Efficiaricy
'p density kg/m3
• Dynamic Viscosity • Pa-s
CHAPTER-I
1.2 OBJECTIVE :
All the major possibilities of producing cooing effect
by means of solar energy have been investigated and affectively
demonstrated. There are hardly any technological barriers, but
the economic aspects need further attention. Most of the earlier
investigators` have gone into the basic research to demonstrate
the cooling effect generated by solar energy. The basic
possibilities probed are outlined herein :
1. Vapour absorption system powered by steam generated by steam
boilers with concentrating collectors.
2. Vapour absorption system powered by hot water heated by
concentrating collectors or flat plate collectors.
3. Vapour absorption system powered directly by. solar energy
heating the refrigerant-absorbent solution by solar heated
watert.
1.2 ANALYSIS OF THE PROBLEM :
The main objective of the present study is to design a
solar powered, air-conditioningsystem which should be able to meet
the requirements of a typical. commercial computer centers etc
located in the remote regions of India, where the conventional
cooling systems can't be run due to non-availability of electric
supplies or due to its unreliable transmission and distribution.
The system shoult have favourable on the basis of. life cycle
costs.
Limitations
The basic limitations in the development of the solar
powered air conditioning are common, to the solar powered devices.
The inherent difficulties of the varying nature of the solar
radiations, non-availability on cloudy days pose challenges to
the system designer. These limitations can be stated as follows
1. The periodic. availability of the'solar radiations in a cycle
of 24 hours demands' that solar powered air conditioning
system should be provided with energy storage facility which.
is an uneconomic proposition.
2. The days when the solar energy is altogether non-available
due to rains or a cloudy sky, the system etc. further
requires to be provided with stand by energy supplies to
improve upon the reliability of the system. This limitation
has been overcome by the provision of agrowaste heater and
biogas fired heater.
3. The 'solar powered air conditioning requires manual operation
of the valves etc. as compared to conventional air
conditioning which hardly require, any attention due - to
automatic control equipment. The system design should be
such that only nominal attentions is required for this
purpose. But with the persent day technology of valve
2
manufacture, it will take some time before cheap good
quality automatic valves are available commercially in
India.
4.
The solar powered air conditioning will find applications
only if it is -economically viable, as such there should be
stress on the utilization of materials and techniques which
are the most effective and least costly. This aspect has
been specially kept in view while designing the solar
powered air conditioning system.
1.3 AMMONIA VAPOUR ABSORPTION SYSTEM :
This is one of the oldest absorption combination
successfully employed in industrial air conditioning. Ammonia
possesses very desirable properties as a refrigerant, in that it
has a.high latent heat of vaporization (1394 kJ/kg at 10°C).
Water is a very good absorbent for this material; it reduces the
partial vapour pressure of the refrigerant to about one third.
However, the partial vapour pressure of water at the
temperature and the concentration of the generator is
sufficiently high so that some. water vaporizses along with the
refrigerant. This requires removal of water from the vapour by
the counter current contact with strong ammonia, and a rectifier
section to further- reduce the water content of the vapour. In the
latest modifications, bubble cap columns have been used in which
liquid is refluxed from the condenser to the top of column,
onia Vapour H,,3-,r onia Liquid'1HU3 rcssy~+r h Aqua k Aqua ~kW1&UV ling Water ©M,s~ am C] d C. re
K
K' A ;c
a : Heating Steam Inlet A : Heating System
b : Condensate Exit B : Vapour Separating Drum
c : Down Pipe C : Rectifier
d : Mixing Jet D : Condenser
e : Bypass Connection E : Ammonia Receiver
f : Aqua Regulating Valve F : Evaporator
g : Liquid Ammonia Level Gauge G : Cascade Absorber
h,i: Shut Off Valve for Rich Aqua H : Aqua Reservoir
k : Cooling Water Inlet J : Aqua Pump
1 : Cooling Water Outlet -_ K Heat Exchanger
L : Float Valve for Regulation
M : Electric Motor for Aqua Pump
Fig.1.1 .: AMMONIA ABSORPTION REFRIGERATOR
yielding nearly pure Ammonia vapour. However, provision is still
required to remove any water which may accoumulate -fromt he
condenser and evaporation.
Adaptation of the bubble cap column are likely to raise
the COP to O.6.This coefficient is also increased when weak
aqua-ammonia solution is passed over coaling coils in the
absorber so that heat of absorption is immediately removed and a
low temperature is maintained in the absorber.
The absorption cycle uses two . fluid streams in a
totally enclosed system. One is the refrigerant, which provides
the cooling effect, the other is the absorbent, which conveys the
refrigerant through the cycle. The major components of the system
are a generator, condenser, evaporator and liquid toliquid heat
exchanger. The refrigerant passes through all units; the
absorbent is confined to move through the generator, heat
exchanger and absorber.
In operation, a mixture of absorbent and refrigerant
is heated in the generator to distil off most or all of the
refrigerant, which rises as vapour to condenser. The generator
and condenser operate at relatively high pressure depending upon
temperature of cooling water, so the condensing temperature of
the refrigerant is sufficiently high to permit rejecting the
latent heat to outside air or cooling water. The liquid
refrigerant is throttled to lower pressure so it will boil a
relatively low temperature in the evaporator and thus absorb the•
heat from the air to be cooled. The vaporized refrigerant passed
to the absorber, where it dissolves in cool 'absorbent solution
which has come to the absorber form the generator outlet: via the
heat exchanger. The cool solution, now rich in. refrigerant, is
pumped back to the generator.
A pump is required for the system to tranfer the weak
solution is returned to the generator. The thermal energy can
enter or leave the system by temperature dif- ferencethe flow of
heat. In the- absorption process the refrigerant is liquified and
vaporized twice during the cycle, as compared with only once
inmechanical comperssion.
The additional vaporization and condensation are
necessary to substitute compression processes for- the mechanical
compressor. The generator and absorber perform the same function
as the compressor by taking low-pressure refrigerant vapour from
the evaporator and delivering high. pressure vapour to the
condenser. .
There are four fundamental processes which take place
during the cycle of operation.
(a) Distillation of the refrigerant ammonia from the rich
aqua-ammonia solution by trnasfer of heat energy to the
generator.
(b) Condensation of ammonia vapour distiled from the generator
by removal of heat of condensation at the condenser.
(c) Evaporation of Ammonia liquid in the evaporator by transfer
of heat from the cooled space or chamber.
(d) Absorption of ammonia vapour coming from the evaporator in
the weak aqua-ammonia solution coming from generator while
the heat of absorption is removed by cooling media.
Two devices are commonly used to reduce the amount of
water vapour reaching the condenser and evaporator in the actual
ammonia absorption cycle. These are the. analyzer and the
rectifier. The analyzer is generally an integral part of the
generator. it consists of a chamber, through which the vapours
leaving the generator pass in counterflow contact with the strong
aqua-ammmonia solution from the absorber and the aqua-ammmonia
solution farm the rectifier, as both of these are introduced at
the top and flow downward usually over trays in the analyzer
column. In this way considerable liquid surface is exposed to the
distilled vapour coming from the generator. The vapour is cooled
and most of the water vapour condenses, so that almost pure
ammonia vapours leave the top of the analyzer and also less heat
is required in the generator.
The vapour flows from the analyzer into the .rectifier.
Its purpose is to cool further, the vapours leaving the analyzer
so that remaining water vapours are condensed, leaving only
relatively dry or pure ammonia vapours to flow on to the:
condenser. It is a heat exchanger. set before the condenser:
arranged in a manner to enable its condensate to drain to the
analyzer of generator.
Further, to improve the operating efficiency of the
cycle, heat exchangers between weak and strong aqua-ammonia are
used. It is universal practice to conserve heat in the cycle.. by
the use of heat exchanger which uses hot weak solution from the.
generator to perheat the strong aqua-ammonia solution from the
absorber'. This improves the cycle efficiency by reducing the heat
input required. Still further improvments in the efficiency of
the cycle may be obtained by subcooling the liquid ammonia from
the condenser with the cool.
1.4 BASIC OPERATING CYCLE
The process undergone by the cooling and absorbent
solution during various periods of cycle basically consists of
ammonia generation and condensation at pressure correponding to
the condensing temperature and after that evaporation and
absorption at constant absorption temperature. Considering 1 kg
of aqua-ammonig solution of concentration X at the beginning of a
the generation process, the state of aqua-ammonia solution can be
shown by the point 'a' identified by the pressure Pa, temperature
to and the concentration Xa. When heat is applied to aqua-ammonis
7
P
P
TE T - Tern p.
_r~8C1.2a> [ P -T -X Dice..'
solution, the solution is first heated at constant concentration
and its temperature and pressure rise, till state paint 'b' is
reached. From 'b' to 'c' the distillation starts and the pressure
is governed by condensing temperature and remains constant. The
vapours of ammonia and water pass an to the rectifier, where
water vapours are separated by preliminary cooling by ambient air
and the ammonia vapours pass on to the condenser for
condensation. The concentration of aqua-ammonia solution falls
from Xa to Xe and the process is carried on till the highest
temperature is achieved at 'c'. The aqua-ammonia solution left in
the generator is equal to
x (1 - X ) 1 - ){a - e a kg.
(l - X ) c
and is cooled to the ambient temperature to state 'd'. The
ammonia condensed in the condenser gets accumulated in the
reci'ved and it is aiso cooled down to the ambient temperature
during the same period. At the state point 'd' the following
information can be obtained.
mass of the aqua-ammonia solution in the collector = and
temperature of the aqua-ammonia solution = td
pressure of the aqua-ammonia solution = Pd
Concentration X = X d e
At this stage the pressure in the receiver section. due
to liquid ammonia will be higher than the equilibrium pressure of
aqua-ammonia solution. Therefore the ammonia can move over to the
collector cum generator and absorber section. The vapour can be„,
percolated through the weak aqua-ammonia solution.. A valve
isolate the receiver and evaporator is operated so that the
evaportor is flooded and vapour starts moving to the aqua-ammonia
solution in the absorber. The temperature in the absorber is.
maintained constants as the vapour percolating through the weak
ammonia solution is simultaneously cooled by cooling water. The
aqua ammonia solution point 'd is brought back to point a
when the pressure on both sides is equalised. The cooling
produced by evaporating ammonia can be used for chilling the
water. The lowest ',temperature achieved is dependent on the
equilibrium pressure of the aqua-ammonia solution in the absorber
a.t the begining of the absorption process while the treminal
temperature in the evaporator is dependent on the final
equilibrium pressure when the concentration of aqua-ammonia
solution is again X. a
In actual practice there are deviations from the
theoretical cycle and the temperature during ..absorption is
usually varying. To stablize the temperature, the heat exchanger.
provided on the rise pipe can be cooled by water for dissipation
of heat during absorption.
9
4= STRONG AQUA SOLUTION
Fig: 1.2 ENERGY FLOW IN A SIMPLE ABSORPTION CYCLE
1.5 CHOICE AND PROPERTIES OF ABSORBENT-REFRIGERANT COMBINATION
While the effiency of an ideal absorption system is
dependent on only the temperature of fluid in absorber, generator
evaporator and condense, it is not possible in practice to obtain
an arbitrary combination of operating temperatures for these
units. If the vapour pressure of the absorbent is negligible, the
partial pressure of the refrigerant in the absorber determines
the operating temperature of the evaporator. The absorber vapour
pressure is determined. by -the P - T - X concentration relations
of the _absorbent-refrigerant. combination. The condenser
temperature likewise depends upon partial pressure of the
refrigrant. over the solution in the generator. Thus fixing the
operating temperature and concentrations of the absorbent
solution in the obsorber and generator fixed the temperature of
the evaporator and condenser.
The choice of the refrigrant and the absorbent is an-
important decision. Some investigations have reserarched on the
performance of several type of refrigrant and absorbent
combination. Ammonia-water, ammonia-sodium thiocyanate, ammonia
and lithium nitrate, ammonia-calcium chloride, water-lithium
bromide, water adn zealites, R-21 and Tetra-ethylme glycol
dimethyl ether are some of the combinations. Each combination
offers some advantages but in the proposed solar powered air
conditioning system, ammonia-water has been selected due to its
favourable features outlined herein
(1) The refrigrant amamonia is very easily available all over
India at low cost and its handling practice is well
established.
(2) The thermodynamic and physical properties of aqua-ammanis
solution are well established and easily referred.
(3) The aqua-ammonia solution is relatively less corrosive on
containing vessel.
(4) The replacement of aqua-ammonia charge of the desired
concentration and quantity does not give any difficulty.
(5) The skill required in handling ammonia can be easily
acquired by semi-skilled operators who are to run the solar
powered air conditioning system.
(6) The cost of the charge ammonia required for the system of
the 20 TR is the lowest.
(7) The thermal performance of the solar powered air
conditioning system in terms of CoP etc. . is quite
favourable.
In line of the above merits of the aqua-ammonia
absorption system is the best system for application in rural
remote regions of India.
2.b OPERATING VRAIAELES AFFECTING SELECTION OF COMBINATIGN e
Low fluid circulation rates are desired to permit the
use of equipment components of comparatively small dimensions. A
low refrigerant circulation rate, for a given cooling caoacity,
necessitates a high heat of vaporization for the refrigerant. A
low absorbent solution circulation rate would result in
relatively small heat exchanger generator and absorber, chile
maintaining good transfer rates, and would require relatively
small expenditure in pumping energy. To obtain such solution
rates the absorbent solution must undergo a large change in
concentration in the absorber and generator. These factors would
require large pressure and temperature changes in the system.
(1) Pressure in the system: Operating pressures must escicialiy
be considered in the design of a practical appi _ation.
Systems operating at sub-atom pressure must be seal .ighcly
to prevent leakage of air into the equipment or supplied ay
the pumps which can maintain the desired pressures. The rate
of transfer of refrigerant in absorbent cycles is mucn less
than in mechanical cycles, since low pressure differenct:al
exists and absorption often occurs largely by diffus:on. The
large specific volume of the refrigerant necessitates large
passage for desired capacities. Any air in the equipment .n
contact with the absorbent solution will also acarava:e
corrossino problems, and decreased the life of the cooling
units.
System component having pressure above atmosphere
system must also be sealed to prevent loss of refrigerant, which
would reduce the quantity of liquid phase below satisfactory
operating limits, resulting in a reduction of the capacity of the
equipment. The greater refrigerant vapour density at higher
pressure and pressure differential obtainable between the
condenser and evaporator permit smaller equipment.
'There must be pressure difference to obtain flow in the
equipment and secure a difference in the evaporator and condenser
temperature and obtain a refrigeration effect.
(2) Temperature in the System : If useful air conditioning
system is to be obtained with high CoP, operating limits must be
stimulated for the temperature of various components. There _must
be sufficient difference between evaporator and air temperature
that sensible and latent heat transfer may be accomplished with a
reasonable evaporator surface area. The lowest practical
evaporator temperature for ordinary air conditioning is
approximatly 350C, since below this temperature there is danger
of icing of the tranfer surface. Evaporator temperature of the
order of 45°C are frequently used.
The absorbers temprature which is regulated by the
evaporator temperature desired and' the absorbent concentration
employed, should be maintained as low as possible to increase
CoP. However, since the heat must be rejected, the lower limit
13
for this temeprature is determined by the quantity and
temperatruer of the available cooling medium. If air cooling is
necessary, a high absorber temperature is necessary to enable
heat transfer in a heat exchanger of reasonable size.
Ideally, the condenser pressure and temperature, is
determined by the partial vapour pressure of refrigerant in the
generator, and it is controlled by cooling—water temperature. It
is desriable to have a high generator temperature to increase the
CoP. It the refrigerant has a low partial vapour pressure over
the solution at this high temperature. the vapour is highly
superheated when released, and heat is wasted in the cycle. On
the other hand, if the absorbent solution permits a refrigerant
vapour pressure, the temperature of the condenser is elevated,
tending to reduce thermal effeciency.
1.7 FACTORS AFFECTING SELECTION OF A REFRIGERANT
The refrigerant must be thermally stable throughtout
the range of operation, and should nctundergo irreversiable
reaction with any material in the system, including materials of
construction. Simple refluxing test usually give an adequate
measure of stability. Reversiable reaction between the
refrigerant and the absorbent is permissible and desirable.
The normal boiling point of the refrigerant is of great
importance, as it determines the operating pressure of the
evaporator, if the boiling point is extremly low, the presure in
evaporator will be relatively high and necessarily, the pressure
in the generator-condenser section will be higher. On the other
hand, a high boiling point refrigerant requires that the
absorber-evaporator be operated at low pressure. To minimise the
effect of leaks in equipments, the vapour pressure should be
close to atmospheric pressure, with the normal boiling point in.
the vicinity of 1000 to 550 C.
To minimise the circulation rate of refrigerant, the
heat of vaporization should be high.
Accoridng to Trouton rule, heat of vaprization - of a
substance is 21 times its normal boiling point in degree
absolute. The numerical factor is not exact, because a large
value is obtained for associated liquids, and those in which the
molecules exert attarctive forces upon each-other.''
Thus compounds having the largest heats of vaporization
will. be those, which are associated and are of law molecular
weight and high boiling point.
Material having these properties are hydrogen fluoxide,
water, ammonia, methyl and ethyl alochol. Values significantly
lower than others. In all of these components, association occurs
15
through the mechanism of hydrogen boiling in which the hydrogen
atoms in the molecules attract and hold the more negative atoms,
of neighbouring molecules.
The specific heat of the refrigerant should be as low
as possible. Some superheating of the vapour usually occurs as it
is released from the generator and this heat must be removed in
the, condenser, which requires, extra cooling. On throttling of
the liquid refrigerant to the evaporator, some, referigerating
effect is lost in cooling the liquid to the temperature of the
evaporator. Both of these losses are reduced as the specific heat
of the refrigerant decreases. If water is used as a refrigerant,
is required to cool of liquid from 45 to 10°C. This heat must be
obtained from evaporation of some of the water. Since the heat of
vaporization is about there is a loss of about $Y. in
refrigrenation effect.
1.9 LAYOUT ©F _THE SOLAR POWERED AIR CONDITIONING SYSTEM
Basic System
On the basis of the availability of the materials and
the quality of workmanship available in the .region, ammonia
vapour absorption air conditioning system has been adopted. To
eliminate the complications, the collection system selected
consists of the flat plate collectors augmented oby booster
reflectors. Since the storage of solar energy is presently a very
4n
uneconomical proposition, the system wil be accompanied by the
other heat supply source (like gas fired furnace, LPG).
The basic elemetns of such a system are shown in Fig.
(1.5) There are four fundamental processes which takes place
during the cycle of operation.
(a) Distillation of the refrigerant ammonia from the rich
aqua-ammonia solution by addition of heat energy to the
generator.
(b) Condensation of ammonia vapour distilled from the generator
by removal of heat of condensation at the condense.
(c) Evaporation of ammonia liquid in the evaporator by addition
of heat from the cooled space or chamber.
(d) Absorption of ammonia vapour coming farm the evaporator_ in
the weak aqua-ammonia solution in the absorber, while the
heat of absorption is removed by cooling media.
1.9 BASIC SUB-SYSTEM :
(A) Vapour Absorption Unit :
This unit consists of a generator, absorber rectifier
for-rectifying the distilled ammonia by elimentary the water
vapour associated with ammonia vapour, an ammonia condenser, an
ammonia receiver, an expansion valve, and a flooded evaporator
immersed in a brine tank.
0
17
61
FIG.1.3 : COMPLETE LAY OUT OF THE VAP-OU-~
_ ABs R TI AIR CONDITIONING SYSTEM '
(b) Auxiliary Flat Plate Solar Collector For Water Heating :
To subsidise the heat energy requirements of the main
solar collector, LPG or biagas heater is provided.
(c) Assisting Heating System :
To enhance the reliability of the system, assisting
biogas fired heater and agrowaste fired heater have been
provided, which can operate the system during periods when solar
energy is not available.
(d) Control values and instruments have been provided effective
operation of the solar refrigerator. Flow-over and equaliser
connection have been provided to control the refrigerant a
aqua-ammonia. solution flow in the system.
1.10 VAPOUR ABSORPTION AIR CONDITIONING SYSTEM COMPONENTS :
The components include the vapour absorption module,
rectifier, condenser, receiver, expansion value, evaporator and
heat exchanger and connecting piping. The various aspects of each
component are discussed herein :
Vapour absorption module
The module is connected to the rectifier, condenser, and
evaporator by high pressure piping having flanged joints. This
provision enables the system to be fitted with other modules for
changing the capacity of the system.
(a) Generator r It is an unit where ammonia is distilled out
from the aqua-ammonia solution. Heat requierd for. distillation is
provided either by solar energy or LPG or by other means. The.
temprature of outgoing ammonia varies from 75 to 95°C.
(b) Rectifier : It is an air cooled exchanger which reduces the
termperature of the mixture of ammonia vapours and water vapours,
such that water vapours are condensed and dramed back to the
generator. The relatively dry ammonia_ vapours are passed to the
coondenser. Temperatures from 50°C to 70°C of outgoing vapours.
imply that sufficiently dry ammonia vapours go the condenser.
(c) Condenser : The condenser is a shell and tube type water
coiled exchanger which condenses the ammonia vapours coming
from the rectifier. The condensed liquid ammonia passes on to
the receiver. The water to the condenser is supplied from a
cooling tower and it goes to the cooling tower where it is
cooled. The water from the cooling tower can be pumped to
, the absorbers.
(d) Expansion Valve : The, ammonia liquid collected in the
receiver is at the pressure corresponding to the condensing
temperature. And when cooling is to produce, the expansion value
is cracked and ammonia liquid rushes to the evaporator coil at
reduced pressure, and gets vaporised. The vapour moves on to the
absorber where weak aqua-ammonia solution absorbs it.
19
PUMP
(e) Evaportors It is a flooded type evaporator and the vapours
of ammonia percolate through the weak aqua-ammonia solutionand
get absorbed there. The evaporator coil is provided with
flow-over connection for transfer of any water which might have
come alonawith ammonia die to ineffective rectification the
chilled water from evaporator is circuited to air.handling units.
(f) Absorber : in this unit of the system, ammonia coming out
from the evaporator is absorbed by weak ammonia solution. Heat of
absorption is removed by circulating the water in heat exchanger.
(g) Values and Instrumentation : Several isolating values have
been installed to isolate the various sections of the system.
Pressure gauge cocks and thermometer oil pockets, have been
incorporated to indicate the respective quantities at various
,Sections of the sytem.
CHAPTER 11
2. 1 LITERATURE SURVEY ? REVIEW ; -
Of the two basic systems of Refrigeration i.e. the
vapour compression V vapour absorption, the later has been more
popular with most of the investigators for solar system, due to
smaller requirements of equipment. With several possibilities of
using photovoltaics, generation of motive steam, heating of water
for use at the generators, most of the attampts have been
restrieted to the use of -vapour absorption system (Intermittent
or continuous) either directly coupled to solar radiations or
through a thermal media. To adapt the vapour absorption system
for solar energy, several combinations of refrigerants &
absorbents have been investigated. Among the several
combinations, ammonia as the refrigerant & NaSCN or water as the
absorbent offer many advantages as compared to other
combinations. A brief description of the work carried out by
various investigator has been summerised herein.
2.2 INVESTIGATIONS OF WORKABLE SYSTEM:-
Green (12) in 1936 explored the possibility of using
solar energy for raising steam to work a steam - jet refrigeration
system. The steam was generated by heating water enclosed in a
pipe placed at the focal line of a cylindrical parabolic
concentrator type collector. His work initiated the solar
refrigeration research at the University of Florida.
Hainsworth 1131 summarised the work done in the field
of absorption refrigeration till 1944. The first absorption
refrigeration. system which was recognized, was produced by
Ferdinand Earre's around 1815. He developed an intermittent
absorption machine, using ammonia as a refrigerant & water as an
absorbent. Since then a large number of continuous .& intermittent
system have been developed using different refrigerant -absorbent
combinations & different modes . of supplying heat to the
generator. Trombe & Foex in 1957 used a vapour absorption system
having ammonia as a refrigerant & water as an absorbent working
intermittently, he used solar energy as a heating source, by
using cylinderical parabolic concentrated collectors. Williams
et.al developed an intermittent absorption system with R-21 as
the refrigerant & TEG-DME as the absorbent. He used paraboloidal
solar collectors for collecting solar energy. A lot of other
investigators had made investigation on VARS by utilizing solar
energy as a motive force. They found that temperature attained in
the generator by solar heating is low & thus the efficiency of
the system is very low. Due to the low efficiency of absorption
system when powered by solar energy, & non reliable nature of
solar energy there is need of developing absorption system based
on waste heat &. fossil fuel as a source of heat energy.
In India also, a lot of work has been carried out in
this field yet more work is required. Under the joint programme
between BHEL & IIT,. Madras one ton VAR system. using
22
Ammonia-Sodium Thiocynate was designed, installed & commissioned
at 117, Madras in 1977. Due to various problems like leakage &
solidification of sodium-thiocyanate etc. system could not be
operated for longer time.
A new system was designed to use ammonia-water as
binary mixture & was tested successfully in 1981. This system was
a research model % was operated by an electric simulator,
Sharma has given the design of cold storage by using gobar gas.
Mark Falleck E9) developed a parallel flow absorption chiller
heater, which can compete with electric centrifugal chillers. He
found that lesser energy is required in generator in_the parallel
flow absorber & efficiency of the system is increased. A major
advantae of absorption chillers is their fluxibility of heat
source, the high temperature generator can operate on steam,
exhaust gas or direct fired burner. He found that in direct
burner, a boiler efficiency of 90% is obtained.
2.3 REFRIGERANT-ABSORBENT COMBINATiONS:-
Buffington [61 had outlined the solid absorbents for
vapour absorption system way back in 1933. Since then a very
large no. of research teams have been engaged in the
investigation of different refrigerant-absorbent combinations.
Hainsworth traced the early developments in connections with
various refrigerants % outlined the ideal characteristics of
refrigerants & absorbents, he found that absorbent must have a
23
greater affinity for refrigerant then rorr•esponds to the ordinary
solubiIi.ty laws. He identified a large number of refrigerants but
found only four of them i.e. ammonia, carbon di-oxide, methyIe
chloride ?y. sulphur di-oxide suitable for refrigeration. For
vapour ahorption system many of the comb mat ions have been
in,/rI~t; i.r]at;ed, the I i t of the 5t1rne ry frigerant absorbent
combinations is given in Table L2.1].
Several other investigators, Piker et al hasinvestigated
AIcof -rol-salt mixtures. Sargent has made comparision of
ammonia-watn_r ?. ammonia sodium-tbiocyan ate systems. But the fact
remains that ammonia water combination 'stay's at the top because
of a very large number of favourable points.
Table 2
Refrigerant-Absorbent Combinations Ammonia with organic
absorbents :-
1. Tetra-ethyl dimethyl ether (TE6-Dt1A) .
2. Tri-ethylene glycol dirnethyl ether.
3. 1,4-Butanedi.ol.
4. 2,3-Butanedi.ol.
5. Tetra-ethylene glycol..
6. Octvlamine.
7. DirnetnyI. accetamide (DW .
Water with metallic salts :-
}.. t.. r 3 r 2. Cat..} Z. N a S 4. M 9 0.
Carbondioxide:-
1. CaD.
Ammonia With Metallic Salts :-
1. NaSCN. Alcohol (CH_SH) , (C,.H. OH) J L 3
2. Naar. 1. CaCI,.,.
3. NaT 2. NH„C1.
4. 2Nai : NaSCN. 3. MgCl 2' L
5. NaI : 2NaSCN. Sulphur di-oxide
6. NH4Br. 1. Silica gel.
7. NH4I. Methylene Chloride
S. ZnCI,_. 1. Dimethyl ether, tri-
9•. CaCl,,. ethyline glycol.
10. SrCl,_.
11. BaCl,,.
12, NiC1..
13, M9C12 .
14.. NH„C1.
CHAPTER III
3.1 DESIGN OF THE VAPOUR ABSORPTION AIR-CONDITIONING SYSTEM :
The design of the absorption system is quite
complitcatecf because of the diurnal and yearly variations in
solar insolation and changes in the state of the ambient air. The
influence of the changes in the concentration and temperature an
the thermal and physical properties of aqua-ammonia solution
plays an important role in enhancing the complications. Still to
obtain the best performance, the effect of variations in these
parameters from the values selected for design purposes, should
be appreciated to regulate it favourably.
3.2 PROBLEMS IN THE DESIGN OF ADSORPTION AIR-CONDITTONINS SYSTEM
The performance of the solar powered air-conditioning
system can be measured in the form of the quantity of ammonia
distilled during generation process and the . evaporator
temperature achieved. These depend in turn on the intensity and
duration of the solar insolation. and. the diurnal changes in the
dbt and wbt of the ambient air. The quantium of solar radiations
decide the highest temperature achieved by the aqua-ammonia
solution contained in the generator. The ultimate concentration
of aqua-ammonia solution after the generation process depends on
the highest temperature achieved. On a cloudy day little ammonia
will be distilled and tranferred to the receiver and the system
design requires provision of assisting heaters run on biogas or
a.growaste.
The changes in the ambient state of the air are likely
to cause fluctuations in the temperature of the cabin. The
l.►r.scihdi f:v of building up (limnoiii z renervr, in the receiver can be
envisaged. The size of the reserve can be determined by watching
the frequency of days when the insulation of poor intensity and
short duration is available. But this will complicate the design,
which will make the air-conditioning system economically
unvi.abi.e. The thermal inertia of the circulation water can be
decided to smoothen the variations in temperature of the cabin.
However, the overall success of the system is dependent
upon economic viability. The system has been known to
refrigeration industry since long, but the system becomes cost
intensive arheri powered by solar energy. The biggest challenge for
the designer is to evoluate cost effective system. Appropriate
LecIIIIO}.ogy c all influence Lhe r_'nsI f avrir,r,+hl y and since solar
powered systems is used in remote rural regions, due
consideration should be giver-I to reasonable reliability, ease in
operation, and durability of equipment.
3.3 BASIC SCHEME FOR THE DESIGN OF THE SYSTEM :
The design of absorption air-conditioning system will
involve the following steps ;
(a) Decision of the cooling load on the evaporator.
(b) Fixation of the design conditions
(c) State of the refrigerant in the evaporator and aqua-ammonia
solution in the absorber during the absorption.
(d) State of the refrigerant in the condenser and aqua-ammonia
solution in the generator during the generation. and
condensation period of the cycle on the P - T - X chart.
(e) Thermal energy transaction at various units of
air-conditioning system during 8 hour cycle and energy flow
diagram.
3.4 DESIGN CONDITIONS
The demand for cooling will be more during the summer
months when the ambient air is having high temperature.. At the
same time the generator will also achieve highest temperature due
to lesser loss to the environment. For selection of the design
conditions, the complete spectrum of temperature variation has
been watched.
3.4.1 Operating Temperature and Pressure in Condenser :
In designing an effective air-conditioning system, the
size -and type of the condenser is calculated by the following
equation :-
Under steady state
Q = U. A. At
n,~r . (~~ . (I r r r h I i II
where A = Surface area of. exchanger m2
pit= mean temperature difference
For a given condenser the capacity to coal is dependent
upon temperature difference, the mean temperature differrn-ce
between the condensing refrigerant and the coolant. Thus
condensing temperature depends on :-
(a} Temperature of water supply, which in turn depends upon wbt
of the ambient air. It is usually given by the sum of wbt
and the approach. /s such the location of the system
considerably affects the temperature of water supply and the
record of ambient air throughout the year in important.
(b) The nature and source of water.
(c) The capacity of the air-conditioning system in turn depends
an ammonia distilled during the generation.
(d) The overall heat transfer coefficient U, which may be
deteriorated with fouling-up of the heat transfer surface as
compared to design values selected initially. The
temperature difference tt will have to be higher to
compensate for reduced U. The effect will be to raise the
.condensing temperature.
It can be observed that the condensing temperature is
affected considerably by the above noted operating conditions,
and these may be manouvered to attain the lowest_ possible
1C)
condensing temperature for a location.
It can be seen that there are three regions of heat
tranfer viz. desuperheating, condensation and subcooling. The
condensing temperature is influenced by the temperature of water
at and inlet and the quantity of water flowing through the
condenser. With increased quantity of water, the condensing
temperature can be reduced and the corresponding pressure will
also'be lwoered.
The temperature of ground water in Lucknow region is
about 2-°C. Also the wbt of air during summer is 2-°C, as such
the condensing temperature around 38aC can be achieved in a
liberally designed condenser.
3.5 STREAM DESIGN :
Referring to flow diagram Fig 3.1 and with the help of
{h—X) chart, following table has been tabulated to calculate
the stream of ammonia through different units of the system.
Ptt r, tp
Fig.3.1 : Flow Diagram of Vapour Absorption
Air Conditioning System.
TABLE - 3.1
Generator Temperature = 95aC, Condenser Temperature = 409C
Absorber Temperature = 30°C, Evaporator Temperature = --20
Point Pressure (bar)
Temperature tcc:1
Concentration K x
(liq.) (Vap.)
Enthalp h (kJ /kg
1. 15.5 45 - .96 1775
2. 15.5 85 - 1 1645
3. 15.5 - 85 .45 - 325
4. 15.5 40 1 - 380
5. 4.0 -2 1 - 380
6. 4.0 -2 - 1 1290
7. 15.5 95 .42 - 330
8. 15.5 60 .42 - 230
9. 4.0 60 .42 - 230
10. 4.0 30 .49 - 62
11. 15.5 30 .49 - 62
12. 15.5 45 .49 - 92
20 x 211 4220 Ammonia through Evaporator = h = 1290 - 380
M5= 4.63 kg/min.
For Rectifier
By mass balance t'ti = M2. + M
By partial mass balance M2 x2 + M3X3 = M1 X1
On substituting the values from Table (3.1), we have
4.63 x 1 ► t1 x .45 = (4.63 + M3)x .96
M3 = 0.363 kg/min. J
hence, M 1 = 4.63 + 0.363 = 4.993 kg/min.
For Absorber :-
By mass balance M9 + M6
By partial mass balance M9X9 + M6X6 = M14X10
now, M9 x 0.42 + 4.993 x 1 = (M9 + 4.993)x 0.49
or M9 = 36.37 kg/min.
t'l1B = 3.63 + 36.37 = 41.0 kg/min.
Heat Supplied to Generator
Q = (M lh l + M7h 7 ) (M3h 3 + M12h 12 ) Q = (4.993 x 1775 + 36.:s? x 330)-(0.363 K 325 + 41 x 92)
Q = 16974.2 kJ/min. or 282.9 kW
Evaporator Load :-
= 20 TR or 70.33 kW
Absorber Load :-
(M9h9 + M6h6 M10h10)
_ (36.37 x 230 + 4.63 x 1290 - 41 x 62)
= 11795.8 ki/min. or 196.6 kW
Condenser Load :-
= M4(h2 - h4)
= 4.63(ib45 - 380) = 5856.95 kJ/min. or 117.6 kW
3.6 DESIGN OF DIFFERENT UNITS
3.6.1 Generator Design :
The performance of the absorption system depends upon
the cooling produced in the evaporator and the heat absorbed' by
the aqua-ammonia solution during the generation process. The
amount of ammonia distilled depends upon the highest temperature
attained by aqua-ammonia solution, as the lowest concentration of
the solution in the generator is decided by its temperature and
given operating pressure.
Heat supplied in generator = 282.9 kW
Also we have &i = UA ( it) .....
where, U = K
......2) fh L tC L
log 7 + ~S •I I s 1 0
where K _ Thermal conductivity of steel S
= 54 W/m-°C t8]
Let outside diameter of coil D = 3.5 cm a
thickness = 5 mm
For Water (h.) I
Properties at 87.500)
In let temperature of water = 9500, outlet temperature = 8O
7
FIG,3,2 : SOLAR POWERED VAPOUR ABSORPTION AIRCONDITIONING SYSTEM
C = 4.201 kJ/kg-°C, p = 963 kg/rn3, = z.88 x 10 kg/m-s p
K = 0.678 W/r-°C {2's
Let velocity of water be 2 m/s
Re p Y 0~ = %3 x 2 x 0.03
2.89 x 10 4
Re = 200625
u x C 2.88 x 10 x 4.201 x103 Pr = _
K 0.b78. Pr = 1.78
Using t1cAdmas Equation #'du = 0.024(Re)0.8 (Pr)0.37 ..... (3)
0.024 (200625)0.8 (1.78)0.37
h. x G. = 518.5 or z I K
° or h. = 11718.8 W/`- m C L
For Aqua-Ammonia Solution (h 1 a
Let D = 3.5 cm, and D. = 3.0 cm Q
Let velocity of aqua-ammonia solution be 2 m/s
Properties ,at (70C;
C = 6.43 kJ/kg-°C, p. 568.1 kg/m3, :1 = 91.41 x 106 kg/m-s p
K = 0.326 wlm-°f (from Table )
V D 568.1 x 2 x 0.35 0 Re
91.41 x 10-b
Re = 0.435 ;, 106 u Cp 91.41 x 10 5 x 6.43
Pr = --
K 0.326
Pr = 1.8
ammonia vapour
15.5 bar
45°C 1
hot water ~'SG Strong aqua-ammonia solution
~[- 1
Water 9000
Fig 3.3 Generator
Using Mcr~dmas Equation c Nu = O.024(Re)0.8(Pr)0.37
Nu = 0.024(0.4351 x 106 )0.9 (1.8)0.37
= 967.2
or h x D 0 a
K 967.2 -o ho = 9009.1 W/m-°C
Using Equation (2)
U = 1 1 + 0.035 Z o 3.5 + 1 3.0 11718.8 2x54 g 3.0 9009.1
U = 3854.3 W,'m`-°C
Now using Equation (1)
282.9 x 10 x= 3854.3 x" x 0.035 x L x (10)
where, diameter of water coil = 3.5 cm and Temperature difference of hat water coming from genrator
=10°c
hence we get L = 67 m
Again Generator Load = 282.9 kW
Heat transferred from water to aqua-ammonia solution* = N C at w pw
N x 4.186 x 10 = 282.9 w
N = 6.76 kg/s
Also N = p A V x Z, 2 = Number of tubes in each pass w
2 = 10
Let length of each tube = 1.0 m
Total length of tube =. 67 m
Number of passes = # 0 7 I ;
3.6.2 Design of Absorber :
In order to fix a unique solution for the design of an
absorber, the variables specified will normally include
(1) gas flow rate and composition
(2) Operating pressure and pressure drop across the absorber
(3) Desired degree of recovery of solute
In addition, the designer frequently has some degree of
freedom concerning the solvent to be employed. Generally, the
solvent must be recovered, and the recoverysystem ordinarily is
considered an integral part of the absorption process design.
The designer ordinarily is required to determine
(1) the best gas velocity through absorber
(2) the height of the vessel and the depth and type of packing
(3) optimum rate of solvent circulation through the absorber
(4) temperature of stream entering and leaving the absorber and
the quantity of heat to be removed to account for heat of
solution.
(5) • the pressure at which the absorber• and generator will
operate
WEAK AQUA
AMMONIA f I
Ay
STRONG AQUA - AMMONIA SOLUTION
.MMONIA
FIG.3.4 : ABSORPTION PHENOMENON
....,,5.. __-•--------- - )lotion
Ammonia vapour
0 water (24 L) water (30 C)
Heat removed in Absorber = 196.6 kW.
--
aqua-ammonia solution
Fig.(3.5) Absorber
Total volume coming into Absorber
= weak Ammonia solution + Ammonia vapour
36.37 4 4.63 x .31 7Bi.2 z
= .045 m/sec (specific volume of Ammonia
at -2°0 = 0.31 m3/kg)
16'% of volume gets shrinked due to absorption of Ammonia
vapour by aqua-ammonia solution.
For water (h.) .- Let D = 2.0 cm & D. = 1.8 cm 1 a I
Properties at (27 C)
;r =995.8 kg/m3 , C = 4.179 KJ/kg-°C, u = @.6 x 10 4kg/m-s K= 0.614 w/m-°C, velocity of aqua-ammonia V = 2.0 m/s
(Heat Transfer, by Brown & Marco)
Be = pVDi _ 995.B x 2 x 0.012 u B.6 x 10-4
Re = 6.947 x 10
Pr = -I C p _ 8.6 K 10-4x 4.179 x 10 K ..6l4
Pr = 5.853
McAdmas Equation
Nu = 0.023 (Re)0.8 (Pr)0.3
= 0.023 (6.947 x 104 ) 0.8(5.853) O.3
292 h. x D.
or I K i = 292
or h. = 5976.2 Wim`-°C I
For Aqua-Ammonia solution (h ) 0
Properties D = 3.5 cm, D.= 3.0 cm o z C = 4.774 kJ/kg-0C , p =781.2 kg/m3
p u = 259.8 x 10-6 kglm-s , K = 0.494 WJm-°C , V = 2 m!s
[From Table 4.1 (a) to (d)]
Re F' VDa 781.2 x 2 x .035 u 259.8 x 10-6
= 0.2104 x 10
Pr = u Cp = 259.8 x 10-6)x 4.774 x 10 K 0.494
2.51
McAdmas Equation
Nu = 0.024 (Re)0.9 (Pr)0.3
= 0.024 (0.2104 r< 106)0.8 (2.51) h D
or
0 0 = 573.5
or h = 8094.85 W/m`-°C Q
Now using Equation (2)
159
We have
1 U _ 3.5 1. 0.033 3.5 1
.0 x 51? b . 2 +
2 x .3''F log .J } CS034 . S5
U = 2852.2 W/m2- °C
From Equation (1)
196.6 x 10 = 2852.2 x n x .035 x (6)
Let temperature rise of water be 6°C
Hence
L = 110 m
Now, heat load in Absorbe = 192.6 kW
Heat gained by water = N x C x At w pcv
N x 4.186 x b = 196.6 w
or S M = 6.45 kg/s us also, N _ p A V x Z t+s
where, Z = Number of tubes in each pass
6.45 = 995.8 x x 0.018` x 2. x Z
Z = 12
Let length of each tube = 1.5 m
Total lenght of tube = 90 m
Number of passes = 121 x01.5 6
Required diameter of absorber
Q = V x 0.785 1201
1.43 where Q = ammonia vapour flow rate or D b x 0.785 3 = t. m/s D = 0.56 m
Equivalent Height of Absorber :- t 2( )0.35 Tom' 0.2 log--~
- H= 5.2 x D x 0.
I L C 1 mG
~'iu 1 m
L
(203
where, m = slope of the equilibrium line = 0.45 L
= Liquid to gas ratio = 7.2 G 7.2
H = 5.2 x 0.03 x(6.94 x 104 )0.2 K ( 71 Log G 0.35 K
D0.45 !-
7.2
7.0 m
3.6.3 Design of shell and tube type Condenser
The heat load on the condenser is estimated to be
97.-6 Kw. This heat is dissipated in the water cooled condenser.
In condenser, condensation of distilled ammonia will be
carried out by circulating water. Temperature of condensed ammonia
is dependent on the wbt of the available water.
Heat removed in condenser = 97.6 Kw
Let outside diameter of coil D = 3.5 cm 0
and thickness = 5 mm
For Water (h.) ; Properties (at 320C?
4t
1ka .+ friesl r►u u
FIG,3,6 ; SHELL AND TUBE TYPE CONDENSER,
~ e = P D - 995.8 x 2 x 003 = 6.94 x 104
8.6 x 1G
CL lr T
~, r - p _ 8.8 x 1 Q 4 x 4.179 x 10`' = 5.85 r: 0.814
Using McAdmas Equation
Nu = 0.024 ( . 94 x 10 4 0.9 i 5.85 f 0.37 h.D.
344.48 K `)r
h. = 7050 W/,n2-oC I
~'ar Ammonia (h ) :- a
Ammonia will be, first desuperheated from 95 to 40°E and
then gets condensed. Neat removed during desuperheating is very
'qrna3 1 ? which could be safely ignored.
~'roperties tat 40°E) :-
ftI = 197.5 x 10 ° kg/m-s, hf = 1100 kJ/kg., , = 579.4 kg/m3
iii = 493 W/m-°L [81
h fg x p1 x g x K13 0.25 (Introduction to h 0.943 ;t, x /St x D Heat Transfer, by
1 a .........(3) Brown and Marco,P-197)
1100 x 103 579.42 x 9.81 x 0.493 ]0,25 h = 0.93 ~ _ a
_ 197.6 x 10 x 40 x 0.035
h = 5935.7 Wlm2-°C
4:,
Using Equation (2)
U = 1 3.5 x 1 + 0.035 10 3.5 1 3 7050 2 x 54 g
} 3 5?35.7
U = 2608.5 W/m2-°C
Also, from Equation (1)
Q = UPi (At) -(Temperature difference far cooling water At = 5)
97.6 x 103 = 2608.6 x rt x 0.035 x L x (5)
or L = 70.2 m
For number of passes and number of tubes
Heat load in condenser = 97.6 kW
Heat removed by water = M x C x At w pw
N x 4.186 x 5 = 97.6
N _ 4.81 kg/s w
Also, N= p A V x Z, Z= Number of tubes/pass w
or, 4.81 = 995.8 x 2 x x 0.032 x Z
or, Z 10
Let length of each tube - 0.6 m
Total length of tube = 70.2 m 70.2 _
hence, number of passes - 10 x O.b
12
45
3.6.4 Design of Evaporator (Flooded shell and tube type) t
The evaporator is the place in the refrigerant circuit
where heat is removed from the substance being cooled, water or
air as in the case of air-conditioning. Liquid refrigerant
within the evaporator absorbs heat from the air or water and,
in doing so, boils. To effect this, two distinct types of.
evaporators are in use .-
(i.) the flooded evaporator, used mostly for'
air-conditioning.
(ii) dry, expansion evaporators, used for both water-
chilling and for air-cooled.
Here, we are discussing the design of Flooded shell and tube type
Evaporator.
(h--Ho C', amnon i i liquid
Water ammonia vapour (12-14°C) (-2°C)
In the evaporator first, water will be chilled by
evaporating ammonia and this chilled water will be recirculated
in air-water heat exchanger to cool the air for air-conditioning..
For Water (h.) 1
Let velocity of water be 2 m!s
D = 2.0 cm and D. = 2.8 cm a i
44
Properties at bulk temperature (10°C)
C = 4.195 kJ/kg-°C, p = 999.8 kg/m3,
p = 1.31 x 10-3 kg/m-, K = 0.575 W/m-°C
15)
F~ u O1 Re =
p
Re = 999.9 x 2 0.018 53424.4 1.31 x 1.0 3
Pr = 2 C .- 1.31 x 10-3 x 4.19 x 103 K 0.575
=9.55
Using McAdams Equation c-
Nu = 0.023 (53424.4)0.8 (9.55)0.3 (5)
or h. K D. 1 t
K. = 274.1
or h. = 7877.5 WJm6-°C I
For Evaporating Ammonia (h0) 0
Le t velocity of ammonia vapour coming out from evaporator be
15 m/s. Do = 3.5 cm, Di = 3.0 cm
Properties .(at -2 C)
p = 641.2.kg/m3, C = 4.624 kJ/kg-°C
K = 0.541 W/m-°C, 1 239.4 K 10r6 kglm-s
(8)
AS
AMMONIA VAPOUR,
WATER
' :: AMMONIA
CHILLED
-.~ -,~ WATER
FIG,3,7 : FLOODED SHELL AND TUBE TYPE EVAPORATOR
NuE = 2.8 x 10-4 (Re x i~Si 0.8 ..... (4, LUJ
where, N = 6.79 p V D 641.2 x 15 x 0.035
and Re p 239.4 x 10
= 0.8035 x 10.
Using Equation (4)
We have Nu = 2.8 x 10 4 (0.8035 x 106 x
h x 0.035 or, a 0.541 = 68.65
or h. = 1856.96 W/m`-°C C
Again, using Equation (2)
U = 1
35 x 10.035 log 3.5
+ 1 +
30 7877.5 2 x 54 g 3 1856.98
U = 1430.5 W/m2-QC
From Equation . (1) : Q = UA ( Lit. )
70330 = 1430.5 x z x 0.035 x L x(6.)
or L ti 150 m
For number of passes and number of tubes in each pass
Let velocity of water = 2 mis
Cross-sectional area of tube = 4 D. = A 0.0182 i
Now Heat load in evaporator = 70.33 kW
Heat gained by water = M x C (Lt) w pw
t4 x 4.186 x 6 = 70.33 w
M = 2.8 k'g/s w.
Also for water
M = ► x A x.V x Z where Z = number of tubes in each pass
2.9 = 94'5.6 x x 0.018 x 2 x Z
Let length of each tube he 2 m
Total length of tube = 150 m
Number of passes = 1507 It
3.6.5 Design of Heat Exchanger for weak and strong
aqua-ammonia solution
In this heat' exchanger, heat transfer takes place
between hot-weak aqua-ammonia solution coming from generator and
strong aqua-ammonia solution coming from absorber.
For hot weak Aqua-Ammonia Solution (h ) a
Properties of aqua-ammonia solution at bulk temperarture of 72°C
D = 3.5 cm, and D. = 3 cm Q 1
Velocity of aqua-ammonia solution be 2 m/s
C = 4.688 kJ/kg-°C, p.= 793.6 kg/m3 P
u = 265 x 10-6 kg/m-s, K = 0.525
(From Table ) pVD Re = _ x'73. b :t• 2 x 0.035
IU 265 x 10-b
Re = 109643.6
F, r ~ t C~~ 265 x 1.0 x 4.68E-3 x 10
F: 0.525
= 2.366
4'~
Hot A9 CL&A-wl-n-) d LL ( L
A mti)Y\J nu
1 55- 6oC
95
T 45 Tcm0.c
FIG.3.9 : HEAT EXCHANGER FOR WEAK fl STRONG
AQUA— AMMONIA SOLUTION
Using McAdmas Equation
Nu = 0.023 i 2O?643 . a) 0.8 { 2.360) 0.3
h it
or , ° = 538.4
or h = 80<<0.2 W/mom-°L a
Far Strong and Cold Aqua-Ammonia Solution fn.) :-
Properties of ammonia at bulk temperature of (3:.5°C}
C = 4.442 kJ/kg-°C, p = 833.3 kg/m3 P
tt = 510 x 10 kg/m-s, K = 0.517 W/m-°C
tFrom Table 5.1 (a) to (d)]
Re _ p V Do _ 833.3 x 2 x 0.03
x 10
Re = 0.9803 x 10
u C -b 3 Pr = = 510 r< i0 x 4.492 x i0 K 0.517
= 4.431
Using McAbmas Equation
Nu = 0.023 (0.9803 x 105 ) 0 . x (4.431) 0.3 h D
or ° ° = 410.5 K.
or h = 7075.9 W/m`--°C 0
Again, using Equation (2}
LJ = 1 35 1 } 0.035 ~ Q 3.5 } i 30 B07.2 2 x 54 g z 7075.9
U = 2980.18 W1m`-°C
Heat last by hot solution = M x C p x (At)
q 3603 3 x 4.688 x 10 _ x 35
= 91739.6 W
from Equation (1) :-
91739.6 = 2960.18 x rr x 0.035 x L x (15)
Here rise in temperature of strong aqua-ammonia
solution is 150C while temperature of weak aqua-ammonia solution
is lowered by 350 C.
L ~: 20 m
Also M = p A V x Z
36.37 = 033.3 x Z7 x 0.032 x 2 x Z
Z =20
If length of each tube is 1 m then number of passes is 1.
3.6.6 Air to Water heat exchanger (cross flow type) :-
Air, which is to be conditioned, will be allowed to
blow over the finned tubes, through which chilled water is being
circulated. This air later-on, will be supplied_ to the
conditioned space.
to find the area of 17 mm/20 mm copper tubes fitted
with Aluminium fins of 1 min thickness and spaced at 10 mm. The
pipe pitch is 60 mm.
4E
0
TO ACCOUNT FOR EXTRA AREA
Fig. 3,8 Air-water Cross flow type Heat Exchanger
WATT2 4
For water {h.) :- Let D = 2.0 cm and D. = 1.8 cm I o I
Properties at bulk temperature {10°C)
C _ 4.195 kJ/kg-°C, p = 999.2 kg/m`'
'U = 1.31 x 10-3 kglm-s, K = 0.55 'vi/m- C~
E5
`' V Do 999.2 x 2 x 0.03 Re= _ 1.31 x 10
Re = 45764.8
_z Pr = C = 1.31 x 1G " x 4.195 x 103
K 0.585 0.939
L}s i ng McAdmas Equation
Nu = C'.Ct23{45764.89•8{0.?39)0•4 h . D .
or 1 1 = 120.0
or h. = 2340.2 Wlm`-°C L
For Air (h ) a Let velocity of air r5 m/s.
Properties at bult temperature {22°CJ
C = 1.0057 kJ/kg°- C, p = 1.1744 kglm P
,L = 1.t^,46 x 10-5 kg/m-s K = 0.0252 W1rn-0 C
Re = p V D. i.1774 x 6 x 0.035
u • 1.846 x 10 5
u, 24-6¢36
Re = 13394 '~~r^~d~ a
Nu = 0.02a(Re)0.8 a E13
5O
Nu = 0.028(13394)O.B
h D or _.. ° = 56.06
or h = 41.96 W1mL-oC r7
Now the inside and outside heat transfer coefficients
are h. = 2340.2 Wlm 2-oC and h = 41.96 W/m2-°C. The inside 1 0
temperature is 60C and outside temperature 310 C. The heat to be.
tranferred is 70330 W.
To account for the extra area of fin
7 D` = 60 x 60 4 eq
The copper tube can be assumed to be concentrically
fitted with 1 mm Aluminium fins spaced at 10 mm comparing the
areas.. We have,
D - 6B mm eq
For Deq _ 68 8 20 0
Let the efficiency of fin be 90%
Number of fins on the tube of 1 m length
1000 _ 100 fins/m length
In
Now root area of the fin
A = n f? (length of tube) 0 0
= n D (1-Nt) a
Where N = number of fins,._.t = thickness of fins
51
Total area of finned tube A = (T -T.) O 0 E
= 67 m`
E 70330 41.96 31-a)
x 0.035 x (1 - 100 x 0.001) 0
= fi. u9B in
Area of fins A - ----x [D - D`1 x N .c 2 f - 4 eq o
_ TZ x E0.068` - O.03521 x 2 x ~0
= 0.533 m
Now inner area of copper tube
A. = tz D. L 1 1
_ ?? x 0.03 x 1
_ 0.0942 m2
Overall heat transfer coefficient
h (A 0 0
f
Ao +A (A0 f ) 1+fi~o
h. x A.
Where In = outside heat transfer coefficient. a
Af = Surface Area of both sides of fins.
U _ 41.96 (0.098 + 0.9< 0.533
(0.098+0.533) [1+41.96 0.98+0.9c0.533
1 0340.2 x 0.0942
= 34.64 Wfm2-•C
Total length of tube = 67 °` Ao+ i of
= 106.25 107 in
c7
For Rate of water flow
~t M xC x tit w pw
70330 = M x4186x(7) 4f
Rise in temperature of water 7°C.
Mir = 2.4 kg/s. or 2.4 LPS
Also M = p A V x i w
2.4 = 1000 x 4 x 0.032
or Z = 5
Let length of each tube = 2m
Number of Passes 5107 ` 21
3.6.7 Design of Rrectifier as heat exchanger :-
The rectifier is a recuperative type of heat exchanger,
which has a mixture of ammonia & water vapours inside the 'tubes &
the ambient air on the outer surface of the -tubing. in the
process of passing through the rectifier, the ammonia will be
fiesuperhe_ated & the water' vapours will be r_:andensed. The rate at,..
which the aqua-ammonia vapour mixture enters the` rectifier, is
dependent upon the insulation and heat- suppllie.d by auxiliary
system. Surface area can be estimated as below:
Surface area = rz D .L l x 2 x Yz D i L L x 3
rz x 0.035 x 0.5 x 2+ r? x 0.03 x 0.3 x 3
=
0.194 m2.. .
The heat is transferred from aqua-ammonia vapour
mixture to the ambient air, the inside film coefficient is high
due to condensation of water vapour & the outside film
coefficient is low due to convection to ambient air. The values
for these coefficients are selected as below:
Inside film coefficient h. = 5000 Wfm2-'rte I. Outside film r_oeffilczent h = 3 4rm2-'r: 0
[I]
The overall heat transfer coefficient
Li 'o 3.:
+
fi. K h 3.0 x 5000 35 I I 0
= 34.7 W/m -K
The mean temperature diff-eence between the vapour
mixture .& the ambient air has been assumed to be 15°C. The heat
exchanger capacity is calculated as below:
= U.A. ( t)
= 34.7 x 0.194 (15)
= 101.02 W,.
The total quantity of ammonia is likely to be around
5.53 kgfmin as per the design operating conditions of the cycle.
Density of liquid ammonia at 15.5 bar is 574.7 kg/m3 &
the volume can be determined.
Volume of the rectifier = 5.53
x 3
10 579.7
= 9.53 litres "' 10 litres
A steel pipe of OD 200 mm & ID 195 mm has been adopted
far the rectifier. It has to have a length to accomodate 10
litres of liquid ammonia. However, to arrange for any future
increase of the capacity a length of 0.5 m instead of 0.33 m, has
been selected. The rectifier has been fitted with a gauge glass
for the indication of level & provided with a scale.
-~-8 COOLING TNER, --3
In the Fig. (3.10) air enters the base of a tower at
oC wbt, water leaves at 2 0 8 24 C & L/G (water to air ratio) ratio
is 1.2, so dh = L/G "x dt.
The calculation is as in Table (3.1). Water temperature
is shown in column I for 10C from 28 to 35oC. The corresponding
film enthalpies are obtained from Fsychromatic tables.
The upward air path is in column 3. The initial air
enthalpy is 72.36 kJ/kg corresponding to 24°C wbt & increases by
the relationship tits = x ut.
55
• HTMOS DNI700O OT'E:bT3
qc ° L$ y
TABLE (3,1)
# 2 3 4 5 6 7
Water Temp. Enthalpy of Enthalpy of Enthalpy diff. # At it
fi.1i~s,h €tir,ha n- ha h-ha h-na h-
(kJ/kg) (kS/kgi (kS/kg)
28 89.5 72.36 17.14 .0583 .0593 .051
29 94.5 73.56 20.94 .0477 .0477 .10,
30 99.5 74.76 24.74 .0404 .0404 .14~
31 105.0 75.96 29.04 .0344 .0344 .18+
32 110.5 77.16 33.34 .0299 .0299 .21+
33 115.0 78.36 36.64 .0272 .0272 .23'
34 119.6 79.56 40.04 .0249 .0249 .26:
35 124.2 80.76 43.44 .0230 .0230 .28'
Calculation of WTU for Cooling Tower
The driving farce (h -h ), at the 'inlet outlet of a each increment is found by subtraction & is listed in column 4.
The reciprocals . are calculated (column 5), & the avrage for h -h a
each increment is multiplied by At to obtain the NTU for each..
increment (column 6). The summation of the incremental 'values
(column 7) represents the WTU for the summation of the
incremental temperature changes. -
Now considering the increments of temperature change & -
calculate the NTU values, which-correspondens to incrrement of
height.
From Table (3.1), for 1°C change in temperature, the
NTO value is 0.28589.
The approach = 29-24 3 = 5°C.
:. Height of tower = 5 x 0.28599.
= 1.42 ti 2m.
Width ti 0.5m, thickness - 0.8 cm ...... Li]
3.6.9 SOLAR INSOLATION:-
The total energy required for the generation process is
282.9 kW. However the insolation requirement will be higher due
to losses at the collector. With the design average insolation
assumed (725 Wfm`) for 'a period of 8 hours, at an average
efficiency of 0.35, the required collector area comes equal to
2 12 m . To reduce investments, it is proposed to supply heat
partly by auxiliary heaters coupled via a heat exchanger. This
hybrid collection system will require relatively low investment.
Heat gained by auxilliary system will be utilised by
aqua ammonia to raise its temperature from 95o to 95°C. Therefore
heat supplied from auxiliary system
= MxC x At p
_ 41 x 5.49 x 10
= 2250.9 k3/'min. or 37.5 kW
costing Rs.105/-
Total cost required during a day = 37.5 x 3600 x 8/1000
= 1080 MJ
Iletice cost of LPG used per day is 11o, 105 x 1USU/60U = us ltiy/-
3.10. Salection of Expauolon Value (Float, Valve)
Valves are used to start, stop, direct and modulate the
flow of refrigerant to satisfy system requirements in accordance
with load requirement. To assure satisfactory performance, valve
should be protected adequately from foreign materials, excessive
moisture and cor'roslon In ret'rigeratIon nyn loin by the innt+r I.I+ntton
of properly sized strainer and driers.
Float Valve - The float switch (or valve) is a device in which
u hunt, I,Itt'ouglt vt.tt'1nL1ui+ In 1.110 InvrI (Ii n I1+.1+t1(I flIH±t ++Iu+; r+(,
ur ututu Lc ul elccLi'lru.L curttucLty. 1.L 1 rut +tiuc:Lod by
equal .1 ].ng linos Lo the vorarin.I En which the .1 1(1(11(1 1 rvv] 1 r+ Lo Ira
mtilt1Ltu]ned,
Operation and Selection - Some f Ioat. w1 Lctief, (IY'.IY. 3, 11 )
operate from the movement of a magnetic armature is located in the
field of a permanent magnet. This method Is adapted to remote
controlled applications and are preferred for ultra-low
temperature applications. Switches having mercury tube contacts
are usually not recommended for installation in an ambient
temperature lower than (-32°C), since mercury will freeze at
Lemur► t_tLut n ul' nl,h, (, 'T.)Hl;)
Application - The float switch can be used to maintain or
indicate the level of a liquid, operate an alarm, control the
operation of a temperature, or perform many other functions.
A float switch, solenoid liquid valve, and hand expansion
valve combination can be used to control the refrigerant level on
the high or low pressure side of the refrigeration system In the
same way that high side or low side float valves are used. The
hand expansion valve, located in the refrigerant liquid line
immediately downstream of the solenoid valve, is initially
adjusted to provide a refrigerant flow rate at maximum load to
keep the solenoid liquid valve in the open position 80 to 90% of
the time; it need not he adjusted there after. From the outlet
aide of the hand expur►n.1,on valuo, the rot i ion I. panrien through a
11no art1 entorq either tho ovoporntnr or anrso drurn, depending on
the unit design.
When the float switch is applied for low side level
control, proper precautions must be taken to provide a quiet
liquid level that properly falls in response to an increase in
evaporator load and rises with a decrease in evaporator load. The
rrnma rocommondaLion for lnnulrrtton of (he body and 1,.iquid Leg of
the low side float valve apply to the float switch when it is used
for refrigerant level control on the low pressure side of the
refrigeration system. To avoid flood back in this application,
control should be wired to prevent the opening of the solenoid
valve when the solenoid suction valve closes.
MAGNETIC RELAY ASSEMBLY
MERCURY
SWITCH
FLOAT VALVE
LW
FIG.3.11 : FLOAT VALVE (EXPANSION VALVE)
SPECIFIC
HUMIDIDY
DST ------
FAN
FIG.3.12 : REPRESENTATION OF VAPOUR AIR CONDITIONING SYSTEM ON PSYCHROMETRIC CHART
8° 888888 8° 8 00 oo o 0 0 8 J1N ID C 1) N - ~ C7 h 10 N Q M N N - - •. I I I I I I I I _II lII I I
! O 0 0 1(1 p ~, ~~ OC1 C7 ti ~' Jl r F) v1 h 0 61 -0► ~0 ID Y1 0 M I N - - - 000 0 0 ;p
a 0 in V In
E 01mN
Wit) Q on N N- w- .0000 00 0- rr
1' 1 I 11 i 1 1 ! 1 I 1 I I 1 1!
11 I iu f —f i D
0 0 in N N 3 N.. -
888 o 00 0 p t
0 coo0001D O, o !'VP,NN - io NN CDQ0 q wN- - 00 a MNN- _00 00000 0 -
:
0 00 0 o 00000 0 om1poirMON0 _00 ao $S o$$ $ 80 08 0 ~n S0 winI In N - - (y 0 3 ~ E QQQ 0 0 « - - de%0 win@ Na
:' 5
Q N Q ,/~~I1 W ■ N +v r
N -- E~
3.8 WATER PIPEWORK
The high thermal capacity, cheapness and safety of
water make it an ideal fluid to convey energy in the form of heat
in air conditioning systems. It serves a prime use in
distributing cooling throughut a building to many ter3inal
devices and/or air handling units and as a conveyance for heat
rejection in water cooled condenser applications. The
application of water piping in these two applications can be
described as closed systems and open systems. Care has tc be
taken with the latter system since evaporation of water causes
residual solids to remain in supension, creating problems of
scale build up.
Recommended water velocities through various services
are shown in Table (3.2). The recommendations are made taking
into consideration the service for which the pipe is to be .sed;
the maximum - acceptable noise levels and erosion. Erosion can
cause severe deterioration by the velocity of the water and the
inclusion of solid matters will cause damage, particularly a: the
bottom of tubes and at elbows. Erosion is a function of these
considerations and time and careful attention must be .pa: J to
proper pipe sizing.
Increased water velocities increase the friction rate
of the pipework with resultant increase in pump and pupping
casts. these costs must be conisdered against the installed
pipework costs, which may be several times as high as the pump
costs, and in air conditioning systems it is frequent practice 'Co
operate at the highest tolerable velocity and friction rate to
minimise the installed cost.
3.9 AIR MOVING DEVICES :
The most common -fan used in Air-Conditioning system is
the centrifugal fan, which can be categorised by the shape of its
fan blades. Five basic arrangements are shown in Fig. t ? of
these types those in most frequent use are the forward curved, &
backward curved, the latter using aerofoil blades when operating
costs in large systems warrant their added capital cost.
The advantages of the, forward curved fans are the
ability to run at relatively low speeds compared with other types
in order to achieve the same air. volume, & the need for a smaller
fan dia for a given duty.
Power Input = r Q H 1000x-; j
Assuming efficiency be 75% 7
Pressure head H = f x L x 2xDxg
_ 0.0004 x 100 x 6' 2 x 0.03 x 9.81
Then power input = 9810 x 2.4 x Ids-3 x 25 1000 x 0.75 a
= 0.784 KW
1 KW (Say)
CHAPTER IV
ECONOMIC,, ANALYSIS
A theoretical investigation has been carried out on the
design & performance of air-conditioning system for a computer
centre at Lucknow of capacity 20 TR. Following conclusions are
drawn.
X4.1 ECONOMIC ANALYSIS & EVALUATION :-
One of the, objective of the investigation is to
discover the economic viability of the solar powered
Air-conditioning system. Analysis is done for conditioning a
computer centre at Lucknow. Several individual components cost
are calculated'on the basis of the component material. the
expected initial investment work out to be Rs. 4,000,00/= & a
lump sum amount of Rs 10000/- is considered enough to be spent at
the end of 5th & 10th year of the plant life for renovation
purposes. The plant is evaluated from the point of view of life
cycle .costs. Uniform annual owning & operating costs approach is
selected for the analysis.
4.2 THE PERFORMANCE dF THE SYSTEM :-
1. Quantity of ammonia distilled per kg water & cooling
effect per kg water increases with the'increase in generator
--temp-era-ture, but rate of increase of these parameters
decreases with the increase in generator temperature. Heat`
-supplied in generator increases with the increase in
generator temperature but total heat supplied in generator
first decreases with increase in generator temperature &
after certain temperature it starts increasing with further
increase in generater temperature.
2. Quantity of ammonia distilled per kg of water R+. cooling
effect decreases with the increase in condenser temperature.
At lower condensing temperature the COP of the system
is higher as compared to that at higher condensing
temperature. At higher condenser temprature COP decreases
more rapidly with the increase in generator temperature.
3. Ammonia distilled per kg of water & cooling effect
decreases with the increase in absorber temperature, but
rate of decrease of these quantities decreases with the
increase in absorber temperature. COP has the same trend as
for condenser temperature.
4. Ammonia distilled per kg water, cooling effect per kg
water & heat supplied per kg of water increases with the
increase in evaperator temperature. COP of the system
decreases as the evaperator temperature is reduced.
4.3 ELEMENTS OF OWNING COST :-
These include initial investment, interest rates,
depreciation rates etc.
6~
Initial Cost ;-
The system for the solar powered Air-Conditioning
system incroporates a large number of components & approximate
pricing of each component has been made, cost of initial charge
of refrigerant is also included. Further the present worth of the
quantium lump sum required for the major overhaul has also been
considered. This has been included in the initial investment. An
interest rate of 12% annual has been considered an the initial
investment.
4.4 SERVICE LIFE & AMORTIZATION PERIOD :-
The basic elements of system are heat exchangers & as
such these units have long life (upto 25 years). On the basis of
service life period outlined by C3], the life erpactancy of the
various units are given belwo:-
Insulation 24 years.
Evaporators ?.t Condenser 20 years.
Coils (tube) 20.years.
Therefore plant life is estimated to be around 1H
years. The renovation & general overhaul after each span of 5
years will keep the unit in trim form.
5.4 ECONOMIC ANALYSIS :-
For Generator :-
Material required for coil = -nED2 - D`1 x L
Density of steel
Rate of steel
Anmount required
4 a I
KE0.0352-0.0321 x 67
= 0.014 m3.
= 7833 kg/m3
= 75/Kg (Including
fabrication charges)
= 0.014 x 5046 x 75
= Rs. 10047/-
For Absorber.
Material required for coil = - xCD2 - D7- lx L _ 4 xEO.0352- 0.032) x 110 = 0.105 m3.
Quantity of steel required = 0.105 x 7833.
Amount Required = Rs 62142/-.
For Condenser :-
Material Required for condenser
= - xED2 - D 3x L _
E0.0352_ 0.032) x 70.2
= 0.0675 m3.
Quality of material = 0.0675 x 7933 = 528.77 m3
Amount Required = 75 x 529.77
= Rs. 39658/-
For Evaporator :-
Material. required
Quality of material
Amount Required
For Water-Air Neat-Exchanger :-
Material Required
Amoun t
xCD2 - BL 1 x L
2 x10.02 -0.0187 x 130 4
0.04082
= 0.04082 x 7833.
= 319.74 Kg
= 319.74 x 75
= R. 23980/-.
_ xCO.022 - 0.01821 x 167
= 0.03 35 r3
= 0.0335 x 7833 x 75
= 19800/-
Weak & Strong Aqua-Ammonia Heat Exchanger :-
Material Required = x[0.0352-0.032] x 20
= 0.0192 in
Amount = 0.0192 x 7833 x 75
= 11298/-
Cooling Tower
Matrial
Amount required
= 4 x C (hxw) tJ
= 4C{2x0.5) x 0.0091
= 0.032m3.
= 0.032 x 7933 x 75
= 1.8800/-
65
Solar Collector
Total heat required per day = 292.9 x 3600 x 8
= 8147.52 MJ
Heat yielding capacity of collector = 722 W/m2 U7J
2 or = 2599.2 k:Jlhr-m
Heat yielded per day by collector = 20793.6 kJ/m`'
or = 20.7936 MJ/ml
2 Hence required area of collector = 12m
Cost of collector = Rs 5000/- per m~
Total cost of collector = 5000 x 12 = 60,000/-
Cost of Pumps
Cost of 1 kW Pump = 3000/-
Number of pumps required = 5
Cost of total pumps = 15000/-
Cost of expansion valve, pressure reduction valve & joints
= 25000/-
4.5 OWNING COST :-
Expected cost of fabrication &, commissioning
Rs. 4,00000/-
Present work of Rs 10000/-needed in the 5th year
= 137000/ ( 1+0. 28)5
= Rs. 4371/-
Present worth of Rs. 10000/- needed in the 10th year
= l0000/l40.18)1
= Rs 1710.6/-
Total initial investment = Rs. 406281.6f-
V.le ij.-i0.iv1LO
Capital Recovery Factor = _•le'9 (1+o.iS)-17
Uniform annual owning cost for Rs. 406281.6I-
= Rs 131066.al-
Annual owning cost of insulation = Rs 8100I-
Annual owning cost of system = Rs. 139166.4/-
4.6 ANNUAL OPERATING COST :-
Vapour absorption air-conditioning system requires
continuous monitoring at specific times during a cycle. The skill
required for operation is quite simple, but still a time shared
operator is must. The wages of a part time operator is included
in the operating cost. Since the system is also powered by
auxiliary heating system {LPG)
Heat supplied by auxiliary system is 37.5 kW.
Total heat required during a day = 1090 NJ
Since total 600 NJ heat is supplied by a gas cylinder of
Cost Rs. 105/. Hence cost of LPG used per day Rs.. 1F91-- Cost of LPG used per year = Rs.570C( L. Operating cost of components are listed below :-
Maintenance cost/year = Rs. 5000/-.
Total wages of part time semi-skilled worker Rs. 25/- per day
= Rs. 8500/- per year.
Total annual operating cost
4.7 ECONOMIC VIABILITY :-
The initial cost of Rs. 400000/- appears high but solar
powered vapour absorption Air-conditioning system is highly
durable 2 has break-even with air-conditioning. It will become
favourable when trend in energy prices is noted. In rural regions
biogas s. agrowaste can be used in place of LPG.
4.8 INSULATION
The insulation over the pipes of the absorption system,
is going to limit the transmission gain of heat from the ambient
air to chilled water. The thickness of insulation has to be
decided on the basis of the expenditure of total annual expenses
on the absorption system in the form of keeping the water chilled
at (b-20Ci.
The choice of the insulation from the point of view of
cost, durability, consistent thermal conductivity, case in
application, resistance to weathering, safety etc. is made &
thermocole has been considered to be the most appropriate.
The decision about the thickness is based on the
estimate of awning cost of insulation and cost of cooling. The
thickness which incur-es minimum n annual total cost has been
chosen.
OPTIMUM THICKNESS INSULATION
COST (Ps) (LACK)
0
MINIMUM COST j it
p
I
F 10PTIMUM THICKNE [
2JG21022023o24Oe5020027G260290300310.320330340350
COST OF C --~- COST OF I ~ (O — — r ,:,~.~ .,. Eq. ICE ~J~ R~.:U ~T: ~. a TOTAL .~
Fig: 3 013 :OPTIMUM THIO1<NESS OF INSULflON
Annual owning cost of insulation
Volume of insulation = Transmission area x thickness
Annual owning cost of insulation =
Cost of insulation x (D+Iifi00, Rs.
where D is depreciation and I is the interest rate
Total annual cost = cost of air conditioning system
+ annual owning cost of insulation
Insulation rate = 25GOfm3
Interest = 15%
Deperciation = .5%
Transmission area = 18 m
on the basis of fig.(5.2) insulation of thickness 300
mm is recommended.
4.9 FUTURE PROSPECTS :-
This system can be developed according to the design
outlined in this investigation & an experimental investigation
may be performed to establish viability, the performance can be
compared with the theoretical investigation performed in this
work. Still an experimental investigation will be a valuable
contribution to the service of vapour absorption Air-conditioning
system design.
410 Charging the System
Before any charge of refrigerant is put into a system,
it must be thoroughly pressure tested for leaks on both the low
and high side of the system. Anhydrous carbon di-oxide should be
used for this and all joints and connections carefully inspected,
soapy water being used for a bubble test. A+ watch on the pressure
gauge will indicate if a serious leak is present. Following this,
a small amount of R1L should be added to the system, and all
joints, pipework and connection gone over with a hallide torch.
The system is regarded as free from leaks if, after
having been left under pressure for 24 hours, no variation is
observed in the gauge readings, due attention being paid to
variations in the ambient temperature, which will alter the gauge
readings.
CHAPTER V
RESULTS AND DFSCUSSION
5.1 GENERAL DISCUSSION :-
The generator, evaporator, condenser & absorber
temperatures, all influence the performance of refrigeration
system. The effect of all these parameters on the systems
performance is discussed below. It is expected that the
investigation shall provide an insight into the performance of
aqua-ammonia absorption Air-conditioning system & its dependance
on different operating parameters.
5.2 ABSORPTION SYSTEM PERFORMANCE STUDY :-
The most important variable which can be varied through
wide range accoridng to the design requirements is the
temperature of the generator. Although, the condenser & absorber
temperatures also effect the performances of the system but these
temperature may be considered constant, depending on local
existing conditions. Evaporator temperature depends an the
cooling requirements. A combined study of the influence of all
these parameters on the system performance can help us for the
optimum design of the system. In the following discussions, the.
influence of these operating parameters both separately & jointly
are discussed.
5.3 EFFECT OF GENERATOR TEMPERATUR ON THE PERFORMANCE :-
The generator is supplied with heat from the solar
collector & from the assisting heater fired by LPG or Biogas. The
airlount of ammonia distilled depend upon the highest temp.
attained by aqua-ammonia solution, as the lowest concentration of
the solution in the generator is decided by its temperature for
given operating condensing temperature.
Table (5.1) & Fig. (5.1) shows the effect of genrator
temperature on the performance of the system. Fig X5.2) shows the
effect of generator temperature on the COP of the system.
Table {5.l)
Condenser Temperature = 40°C, Absorber Temperature = 30°C
Evaporator Temperature = -2°C, Cooling Capacity = 2OTR.
Generator ------------------------------------------------------------------
COP Heat input Amount of Ammonia Temp to the Generator Distilled
( 0C) (kw) (kg/min)
75 0.1521 397.5
80 0.1908 451.1 4.93
95 0.253 407.2 4.97
90 0.2743 292.0 4.88
95 0.2782 282.9 4.992
100 0.2325 308.() 5.057
105 0.202 320.1 5.52
n-3
°u l 1 Ill i i.iI j I }I!lll : dr ah 11 I„, I. II rl i"IL A
Il,:;iid;a11"IIII'I'If al.ni~;'Ph'° ~~ ivhIP
Fig (4.1)
--
Ij
rerrormance of the Absorption system at different
Generator temperature.
It is desirable that aqua-ammonia solution in the
generator should operate at the highest possible temperature. The
likely operating temperature for the generator is going to vary
from 75 to 450E &. because of this the cooling capacity in each
cycle is going to vary in step with variation in generator
temperature.
All these figures show that COP of the system first
increases with increase in the generator temperature & reaches
its peak & after that decreases with increase in generator
temperature.
5.4 EFFECT OF ABSORBER TEMPERATURE t-
Absorber temperature also depends upon the cooling
water temp. conditions. Fig. (5.3) shows the effect of absorber
temperature on the performance of the system. It is analysed that
the COP of the system decreases with the increase in absorber
temperature. The reason for this is that as the absorber
temperature increases with same evaporator temperature, the
concentration of ammonia in aqua-ammonia solution decreases. As
the evaporator temperature is same, its pressure will also be
same. The pressure of. absorber remains same & its temperature
increases, at this low pressure & high temperature, the
concentration of ammmonia in aqua-ammonia solution also
CL
'1,,) „ ~5
4
~~'~~~~Ilh,i~~.:'1 ~1„~~ ~N° ,N~ ~i a~ 111°' ~.n, ki ~~ ►~ ql :~ . ~~a~~ r~..~: P N., N
4 !I
Fig: 4,3
0
I~~IhLN IPII~R~ II~I~I,~~I R~I II":hrrdl il'iril ~,II iie~~ III
dill flrm,
Illlr ~ll q ~•
"li Ip i Im I I ri I"I A Pr ~ r n~
..r n~~~~► ~~u ~~~.I,
,~~ ~I~ II~ ~N~L.,~ uir~H ~~ I ~,~~ ~~
~~ in ~r~ I~~,~ all ~~~~r~„N Ad r IA ~h•~
n~~~ l~l ~~lll iM~~lg1.tl~;`~r I~dI1 ~~II I~~Ilrililll.P Il~llo~l'~II~I Ul,ll llyrl'~~i~~~llli~l lr;ll •~
'4
III„~I ~ 41 rlliun hr 1~ hI
C 6y,hi I~ Ip ry„ r
I
rrIµiir M npI y~~ry'pry1' N 1 p
rll~~~l~~ II.~I 4'n~~ M ull' II” III~pl ll61P 1~ II ~iEP it l~ Ill lll;li~ n ~I, f J111 l~ol~r f ; ~lJI
.I•I, I~
~q I 1I
......
~Ilrll I7Ar
I .... p
,,
.I, iiii ..11l1,l 1IIi)
Fig: 4.4
I
111•.
i4 i
L4
U.
=; ED
Una
GEM
ama
k
- _
1
decreases. This reduces the quantity of ammonia distilled per kg
of water & hence reduces the cooling effect per kg of water,
leading to the reduction in the COP of the system. The rate of
decrease of the COP increases with the increase in absorber
temperature when the concentration of ammonia in AA8 after
absorption will equal to the concentration of ammonia in AAA
after generation the COP of the system will become zero, because
at this absorber temperature no ammoia will be distilled out.
It is clear from the Fig. 15.4) that concentration of
ammonia in absorption system decreases as the absorber
temperature increases at the same evaporator temperature. Due to
decrease in the initial concentration of ammonia in absorption
system, the quantity of ammonia distilled per kg of water
decreases with the increase in temperature of absorber.
5.5 EFFECT OF CONDENSER TEMPERATURE :-
The condenser temperature is also an important
operating parameter. This temperature is normally dependent upon
the temperature of available cooling water.
The effect of condenser temperature on the COP is shown
in Fig. (5.7 & 5.8). These figures show that the COP of the
system decreases as the condenser temperature increases_ COP
decreases more sharply as the condenser temperature increases.
The reason for the decrease in COP with the increase in condenser
Ii
20 5 c 60
Crii. nr 'Tnp n de ç)
3 e r (v); e.s a 4) d e g
Fig: 4.7
C iji IM
FAI
= __
PTj
LC
aiMa "-54
-
Mm
mmi
em
I
1Tj
o
L
gig
CiP
a
-77
temperature is that as the condenser temperature increases,
saturation pressure of ammonia also increases hence condenser &
generator pressures also increase. With increased pressure & same
generator temperature, the concentration of ammonia in
aqua-ammonia solution after generation increases, hence ammonia
distilled per kg of water decreases. Pence the quantity of water
charged in the ssytem will have to increased to distil same
amount of ammonia, this increases the heat supplied in generator.
S . 6 EFFECT OF EVAPORATOR TEMPERATURE :-
Evaporator temperature is selected according to the
cooling requirement. It is taken as 6-B°C below the temperature,
up-to whiich water is to be cooled. The effect of evaporator
temperature on the COP of the system is shown in Fig. (5.11 &
5.12).
It is clear from the figure that the COP of the system
increases with the increase in the evaporator temperature. The
ammonia distilled per kg of water & the cooling effect per kg of
water increases with the increase in the evaporator temperature.
As the evaporator temperature increases, the concentration of
ammoina in absorption system in absorber increases.From
fig.(5.11). It is clear that the heat supplied per kg of water
increases with the increase in evaporator temperature, while the
total heat supplied decreases. This is because of the fact that
the amount of water required to absorb the same quantity of
La
LT
\
• :
• I.
I
I.
.i .
•
H.
LO
m
2
Eaporator Ten p. kmnoa.distilied,"kg Tc95(de)
;t)1r2 c st ifq; wat'
• Eao rator Ten' (in de) 4
1—
. ,
• T4O Tam 3O
Fig; 4.13
P. -
=
Table (4.2)
Effect of Absorber Temperature on Genertor Temperature for
maximum CoP
Generator Temperature (°C) for maximum COP
-------------------------------------------------------------Evaporator Temperature = -2°C
Absorber ------------------------------
Temperature Condenser Temperature (°C)
30 40 --------------------------------------------------------------
20 81 97
25 96 90
30 91 95
35 96 104
40 101 108
45 105 112
-----------------------------=--------------------------------
Table (4.3)
Effect of Condenser - Temperature on Genertor Temperature for
maximum CoP
Generator Temperature t°C) for maximum CoP
Absorber Temperature = 35°C Condenser ------------------------------
iempe.raturet°C) Evaporator Temperature (°C)
-6 -2 --------------------------------------------------------------
20 92 87
25 97 91
30 101 96
35 i05 101
40 109 103
45 111 105
" 6
Table (4.4)
Effect of Evaporator Temperature o•rr<'`,Genertor Temperature far•
maximum COP.
Generator 'Temperature ( C) for maximum COP
__---._____ __________._._______.------------------------------------------------ Condenser Temperature - 40°C, 30°C
vaparator ~_-_-_-_------- ------
1emp-erature.t °C') Absorber Temperature = 30°C,' 30°C ------------------------------------------------=-- =----- ----_- '~r
113 100
108 98
-4 101 95
-2 95 92
92 89 90
sb
Table i4.5) Combined effect of All he Temperatures Generator Temperature (°C) for maximum COP
Evaporator Temperature Condenser Ab--r-r±r _.---------- .____________._._
}Temperature ( °C) Ternpberature (°C) -B -6 -4 -2 0
20 20 81 79 75 71 6~
25 25 .. 90 87 85 82 79
30 30 99 97 94 91 89 35 35 108 1.05 103 101 99
4O 40 115 115 110 108 107
j 45. ---.-----------------------------------------_--_----------------------
45 t;17 Ii? 113 112 110
Thereophysicai properties of l(qua-Aeeonia Solution
TABLE• 5.1(4
Thermal Conductivity of Aqua-Ammonia SolutionliV/a.KI
Mass concentration, % Ammonia
Temp, -
(k) 0 10 20 30 40 50 60 70 80 90
270 543 543 544 544 545 545 545 546 546 546
280 566 559 552 547 541 537 533 529 527 525
290 592 577.'. 563 550 539 529 521 514 508 5,93
300 612 590 569 551 535 520 508 497 488 482
310 629 600 574 550 529. 510 494 480 469 460
320 643 608 576 547 522 499 479 463 449 438
330 656 615' 578 544 514 467 464 445 429 417
340 664 618 576 S38 504 474 448 427 409 395
350 672 62). 574 532 494 461 432 407 387 372
360 679 623 571 525 ;493 446 415 388 366 , 349
370 681 620 565 515 , 470 431 397 368 344 326
380 684 618 559 504' 456 413 376 345 320 300
390 685 614 549, 491 438 392 352, 318:. 291 2fi9
TABLE- 5j.1(b)
VISCOSITY OF AQUA-A1MON1A SOLUTION to Pa-S)
Hass concentration, % Ammonia
Temp.
lkI 0 10 20 30 40 50 60 70 80 94
2110 1478,6 1348.34 1218,08 1087.8 957.56 827.3 697 566.8 436.52 306.26
290 1116,1 1020.24 924.42 826,58 732.74 636.9 541 445.2 349.38 253.54
300 879.1 805.29 731.48 657.67 538,86 510 436.24 362.4 288.62 214,81
310 711:3 652.77 594.24 535.1 477.18 4t1,5 360.12 301.6 243.06 184.53
320 591,8 543.96 496.12 448.20 400.44 352.6 304,76 256.9 209,08 161.24
330 503.3 463.16 423,02 382,88 342.74 302.6 262.46 222.3 182.18 142.04 1
340 433.5 399.36 365.22 331,06 296.94 262.8 228.66 194.5 160.38 126,24
350 377.6 348,16 316.72 209.3 259.84 2o.4 200.96 171.5 142.08 112.64
360 333.3 307.51 251,72 255.9 230.14 204,35 178.56 152.77 126.98 101.14
370 297.9 274.96 252,02 229.1 206.14 183.2 160,26 137.3 114.38 91.44
380 271.2 250.14 229.18 208.2 151,16 16.15 145.14 124.1 103.12 82.11
390 248.6 228,77 208,94 189.1 169,28 k~.15 129,62 109.8 89.96 70,13 `.
X00 228 209.08 190.16 171.24 152.32 13:1.4 114.48 95,5 76.64 57.72
TABLE - 5.1(C)
SPECIFIC HEAT OF AQUA-AMMONIA SOLUTION lkJ/kg-K)
mass croncentration., % Ammonia (emp. ..._
°k) 0 10 20 30 40 50 60 70 80 90 1
80 4,190 4.237 4.285 4.332 4.379 4.426 4,473 4.52 4157 4,615
?90 4.178 4.234 4.289 4.345 4.400 4.456 4.452 4.567 4.623 4.678
100 4.17 4.234 4.299 4.363 4.426 4,492 4,557 4.62 4.666 4.75 1
i10 4.167 4.242 4,316 4,390 4.464 4.538 4.612 4.686 4.761 4,83
120 4,167 4,253 4,339 4.424 4.51 4,595 4.68 4.767 .4,853 4.94
i30 4.170 4.270 4.370 4.470 4.57 4.67 4.77 4.87 4.97 5.07
NO 4.177 4.290 4,403 4.516 4.629 4.74 4.85 4.967 5.08 5.19
150 4.186 4.331 4.476 4,662 4,167 4.91 5.056 5.203 5.348 5,49
160 4.197 4.381 4.566 4.75 4.935 5,12 5.304 5.488 5.67 5.857 E
170 4.21 4.456 4.703 4,95 5,196 5.44 5.69 5.937 6.18 6.43
+d0 4.222 4.579 4,936 5,294 5.65 6.00 6.366 6.72 7.08 7.437 .1
X90 ' 4,238 4,841 5.444 6,047 6.65 7,254 7.857 8.46 9.06 9.66 1
SPECIFIC VOLUnK OF AW-AnMo181A 5OUYUOI 10411
mute concentration, % Ammonia
Tomp.
(°C l 0 10 20 :1{1 40 50 60 70 80 90
-10 .001 0.001029 .001058 .001088 ,00112 ,00114 .00117 .0012 ,00123 .0012
0 .001 0.001031 .001062 .001093 ,001124 .00115 .00116 .00122 .00125 .00129
10 .001 .001034 ,00106t ,001103 .001137 .00117 .0012 .00124 .00121 .00131
20 .001 .001037 .00107 .001113 .001151 .00119 00122 .00126 .0013 .0013 ,
30 .001 .001041 ,00106 .001123 .001164 ,0012 .00124 .00129 .00133 ,00137 .
40 .00101 .001054 ,001096 ,001143 .001187 .00123 .00121 .00132 .00136 .00141 .
50 .00101 .001051 .0011 .001153 .0012 .00125 .00129 .001344 .00139 .0014 .
60 .00102 .001072 .00112 .001175. .00122 ,00128 .00133 .00138 .00143 .0014E .1
70 .00102 .001077 ,00113 .001193 .00125 .00131 .00136 .00142 .00148 .00154 .l
60 .00103 ,001093 ,00115 ,00122 .00126 .00134 ..00141 .00147 .00153 .0016 ,C
90 , 00104 .00111 .00118 .00125 .00132 .00139 .00146 .00153 .0016 .00167 .0
100 .00104 ,00112 .00119 .00128 .00136 .00144 .00152 .0016 .00168 ,00116 .0
110 .00105 .00114 .00123 .00133 .00142 .0015 .0016 .00169 .00179 .00188 .0~
120 .40106 ,0017 ,00128 ,001:13 0015 .0016 .00173 .00184 ,00195 .0020 .01
1,30 .00107 .001227 .00138 .00154 .0017 .00186 .002 .0022 .00233 ,0025 ,Oc
FLO/ CHART 4? L
.d of thu.
Raj Enthpt :f
at duff. -ts Ir Ttip.
Read Conrmtratlon of
t f or 7prair
of vaper rpiion :sti IL' Ie'ip I
iilat Yicri
Reat !flt
5:x Th
I Find out t
r1iMU11 top -mrr.?dponding to
:~ocram evap; ~ses cr~;
mat1 = array [i.'10] of real, ~ar
T,rhoI,rhoo,ko,nuo,Cpo,ki.mul,nul,Cp,Re`l: mtt1; U,nuoo,hii ° hpo,nui:matl` Q:real; i:integer:
reuin clrscr; -[1]:= 24'0; rho1[1]:=.995,E k1[1]:~ 0.614; nul[l]: 0.00098;Cp[1]~~ 4179.0;
2],= 26'0; rhol[2]:= 994. kl[2]:= 0'623; nul[2]:= 0.000765;Cp[2]'= 4179.0;. -:33;~ 28.0; rhoI[3]:= 993.0: k1[3]:= 0.63; nul[3]:= 0.000682: Cp[3]'= 4174.0; E4]:= 30.0; rhol[4]:= 990.6' kl[4];~ 0.637; nul[4];= 0.000616:Cp[4]:= 4179.0;
~[5]:= 32.0; rhol[5]:= 988.7; kl[5]:= 0.644; nul[S];= 0.000616;C 5J: 4179-0; T[6]^= 34.0; rho1[6I:= 983.3; tl[6]:=0.654; nu1[6] 0.000471;Cp[6]:~ 4186.0: -[7]:= 36.0; rho1[7]: 7]:= 0'665; nu1[7]:= 0.000438;Cp[7]:= 4191.0; ~[8]:= 36.0; rhol[8]:= 973'T` kl[B]:= 0'668; nul[8]:= 0.0004; Cp[8]:= 4191.8;
-~1J:= 24.0; rhoo[1]:= 868,E; kc.1];= 0.535: nuo[1];= 0.00053886' Cpo[1]:= 4428.0; -[2]:= 26.0; rho~[2]:= 867':: :Z]:= 0.534; nucL2]:= 0.00051264:Cpo[2]:= 4439'0: -:3]:= 28.0; rhoo:3]:= 864.~2 :3];= 0.533; nuo[3];= 0.0005013; Cpo[3]~= 4445.0; 4]:= 30.0; rho~[4]:= 862.2=; kc~4]; 0.532; nuo[4]:= 0.0004B956`Cpo[4]:= 4478.0; -~53:= 32.0; rhoo[5];= 859.~; kc~5]:= 0.529; nuo[5]:= 0.00048353;Cpo[5];= 4493.0; -[6]:= 34.0; rho[6]:= 658.3/ ko~6]:= 0.527; nuo[6]:= 0.0004812:C~o[6]:= 4464.0; -[7]:= 36.0; rhoo[7]:= 357.2; k7]:= 0.527; nuo[7]:= 0.00047718`Cpo[7]:= 4472'0; -[8]:= 38'0; rhoo[8]:= 856'5: ko~B]:= 0.526; nuo[8]:= 0.00047518; Cpo[B]:= 4479'0;
:-:= 196600.0;
-or i:= 1 to 6-d begin
zui[i]:= 8.023*e:p<0.8*ln(rr:-l[L-0.04/nul[i])) * exp(0.3*1n(nul[i]*CpEi]/k1[i])};
ruo[i]`= 0.024*exp(O.8*ln(rhoo[i]~0. . nuo[i]\} * exp(O.3*ln(nuo[i]*Cpo[i3/k~[i])>;
UIi]:= 1/( (0.02/(0.018*hii[i]) ) + 0.0000195 + (1/hoo[i]) ) ;
~[i]:= Q/( U[i]* 0.376);
endv
Ircr;gotoxy<1,10>; ~or i:= 1 to 6 do bin ~rite('Length : ');write(l[i3:7:2); *riteln:end;
'readln~
program evap • uses cr t; _ type pe
match = array £1..10] of real var
T ,rho. :,mu,Re,hoo.nu: mlti; u,i:mati i:inteoer•
begin clrscr; TEII:= 0.0; rho[1]:= 640.1; kC17:= 0.54; mug 17:= 0.0002387; T[2]:= -1.0; rhoC2]:= 641.4, k[2]:-.0.54 3; muE ]:= 0.0002375; TC3],=.--2.O; r ho[.T7:= •642.7; kE37:= 0.5406; muE_]:= 000023807; TC4]:= -3:0; rhoC47:= 644.0; k[47:= 0.5409; muC4]:= 0.0002.3898; T[57:= -4.0; rho[5]:= 645.3 • kC5]:= 0.5412; mu[57:= 0.00023972; T[6]:= -5.0; rhoE6]:= 646.6; kC6]:- 0.541: rut6]:= 0.00024147; _ for i:= 1-'to 6-do begin nuti7:= OV.QC}~}4947* exp(0.8*ln(rho[i]/muCi]));
• hooEi7:= r lCI]: kE1]/o. 2;. u[i]:= i/( .)0015054+1!hooCi7); lEi]:= 70330.=/(uCi]*3.14159c0.02*4.0); end; go+_oxy(1,7). V for i:= 1 to 4 do begin V • ritei`The value of L. is '); rite(iCi7:7:')
• writein; :.. end; readin; V • and. •
The value of L is - 130.52 The value of L is 129.88 The value of L is 129.85. The value of L is 129.94 The value of L is 129.97 V V ' The value of L is 1.0.39 . -
uses :rt;
type mst1 = array [1..10] of reai;
var :- -: T,rno\,tfQ,kl,mul,nul,deltal,Re,l: mati; ~a,bb,cc:mat1;
'
Dou,deltat,0:rea1; ij:integer;
label |,2; begir. lrscr/
T[1];= 30.0; rho1[1],~ 596.37; k1[1]:~0.507; nul[l]: 0.000000349;de1tal[1]:= 65. T[2]"= 40.0; rho1[2];= 580.99; kl[2]:= 0.493; nul[2]:= 0.00000034; deltal[2]:= 55. T[3],~ 50.0; rhol[3]:= 564'33; k1[3]:= 0.476; nu1[3J:=/0'0[000033; delta1[3]"= 45. T[4]:= 60.0; rho1[4]r= 550.66; kI[4]:= 0.456; nuI[4]:= 0.00000C:21; deltal[4]:= 35
11450:0.0 ifg[3 105100{.0~ hfg[2:`= 1100000'0;hfg[4]:= 1021000'7~
muI[1 rhol[1] * nul[1]; mul[2~;= rh~1[2] * nul[2]; mu1[3~:= rhol[3] * nui[3]; mul[4i:= rho1[4] *nuI[4];
O~= :t::;800.0; deltat:= 5.0;
for I to 4 o begin
a~[i~,~V.943*(exp(0.25~ln(hfg[i]~rhol[i]*rhol[i]~9.~1$kl[iJ~kl[i]*kl[i]/(m~l[i]*del~
bb[i]:= 1/(0.00021435+1/aa[i]); ~'
1[i]:~ Q/(bb[i]*3.14159*0.035*deltat); '
end~ clrscr;gotoxy(1,10);
for i:~ 1 to 4 do begin ~rite('Length : ');write(I[i]:7:2); writeln; end; readln;
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