Heating Coil in the Main Air Handling Unit

8/18/2019 Heating Coil in the Main Air Handling Unit

1/15

Heating Coil in the Main Air Handling Unit (AHU)

Once the cold season is hot water or steam is supplied to the heating coils in the

AHU. This coil heats the leaving the AHU, sending warm air to all of the rooms.. The

coil consists of a copper header suppling steam to a copper tu!e which passesthrough a continuous aluminium "n for added heat transfer surface area

HEATING COIL CALCULATION

#hen a certain volume of air passes a heating

coil, air temperature is increased from t$ to t%.

This process ta&es place at constant air

humidit. The e'ect of the heating coil is

calculated as follows

* + . $.% . t -, where

+ * air /ow rate, -m01s

t * increase in temperature across the coil,

-2C

34ample on calculation of re5uired heating coil

e'ect

t$ * 67 C, 8H * 96:

t% * %67 C

+ * $.; m01s

* $.; . $.% . %6 * 0;

Air velocit

The air velocit across the heating coil is

calculated as follows

+

v * + -m1s, where < * A

A


2/15

+ * air /ow rate m01s

A * gross area m%

#ater volume

To calculate pressure drop on the water side

of the heating coil and determine the si=e ofthe shunt valve, the water volume in a heating

coil must !e given.

This is calculated as follows

5 * -&g1s, where

Cp. t

* heating coil e'ect, -#

t * temperature increase of water through the

heating coil, -7 C

Cp * ;.$>9 ?1&g7 C at a water temperature of

967 C


3/15

@pace eFcienc is enhanced ! the compact si=e of the individual units, the long

ma4imum piping length, and the a!ilit to reali=e a largeGscale air conditioning

sstem with a single piping circuit.

O'ers a wide selection of models

+ineup of heat pump tpes is 9 to ; HI, and heat recover tpes is to ; HI,!oth in % HI incrementsJ. Endoor units consist of $6 tpes with a total of K0 models.

This wide selection of models ma&es it possi!le to !uild a sstem that perfectl suits

the customerLs re5uirements.

J 34cept for 9 HI

Operates over a !road temperature range

The lower end of the operating temperature range in heating has !een e4tended

from $97C to %67C.

Irovides superior design /e4i!ilit

The e4tended ma4imum piping length gives more /e4i!ilit when designing the

sstem.

+aout changes can !e made easil !ecause the capacit of the indoor units can !e

up to $06: that of the outdoor units.

Dew compressor technolog eliminates the need for piping calculations, which

shortens the time needed for design.

Outdoor units can !e placed on the roof where the have no e'ect on the design of

the !uilding interior.

3nhances ease of use

Units are designed to operate 5uietl, and are also e5uipped with a function for

silent operation especiall at night. The controller is eas to operate and has man useful functions. Units can !e

controlled in each individual room.

elivers ultimate relia!ilit

The selfGdiagnostic sstem identi"es pro!lems within the sstem 5uic&l and

accuratel.

The Auto 8estart function ensures that operation is restored with the previous

settings even if the power has !een shut o'.

Units are controlled in each individual room, so local malfunctions does not cause

the entire sstem to shut down.

@impli"es installation

The lightweight, compact units can !e transported using a regular lift.

Units can !e installed on each /oor.

The pipes are narrow and few in num!er, ma&ing laout simpler.

Enspection after installation is straightforward


4/15


5/15

pressure dependent


6/15

speciali=ed items such as M8E machines and lasers. Endustrial chillers tpicall come

as complete pac&aged closedGloop sstems, including the chiller unit, condenser,

and pump station with recirculating pump, e4pansion tan&, noG/ow shutdown, and

temperature control.

Closed loop industrial chillers recirculate a clean coolant at a constant temperatureand pressure to increase the sta!ilit and reproduci!ilit of waterGcooled machines

and instruments. Open loop industrial chiller sstems are also availa!le. Open loop

industrial chillers control the temperature of a li5uid in an open tan& or sump !

constantl recirculating it. The li5uid is drawn from the tan&, pumped through the

chiller and !ac& to the tan&. An ad?usta!le thermostat senses the ma&eup li5uid

temperature, ccling the chiller to maintain a constant temperature in the tan&.

Most industrial chillers use refrigeration as the media for cooling, !ut some rel on

simpler techni5ues such as air or water /owing over coils containing the coolant to

regulate temperature. #ater is the most commonl used coolant within process

chillers, although coolant mi4tures (mostl water with a coolant additive to enhance

heat dissipation) are fre5uentl emploed. Endustrial chillers are used for controlled

cooling of products, mechanisms and factor machiner in a wide range of

industries. The are often used in in?ection and !low molding, metal wor&ing cutting

oils, welding e5uipment, dieGcasting and machine tooling, chemical processing,

pharmaceutical formulation, food and !everage processing, lasers, vacuum

sstems, QGra di'raction, power supplies and power generation stations, analtical

e5uipment, semiconductors, compressed air and gas cooling.

Emportant speci"cations to consider when searching for industrial chillers include

the power source, cooling capacit, /uid discharge temperature, and compressor

motor horsepower. Irocess pump speci"cations that are important to consider

include the process /ow, process pressure, and pump rating. Other important

speci"cations include the reservoir capacit full load amperage. Control panel

features that should !e considered when selecting !etween industrial chillers

include the local control panel, remote control panel, temperature indicators, and

pressure indicators. Additional features include emergenc alarms, hot gas !pass,

cit water switchover, and casters. An important environmental parameter to

consider is the operating temperature.

To cool down a large !uilding, it is often !etter to have a central air conditioning

sstem. Et is simpler to have the refrigerant unit located at one place, and

distri!uting the coolness using water. Chilled water is easil pumped and it is a!le toreach all /oors in the !uilding. The heart of the central air conditioning sstem is

the chiller.

Chillers ma&e use of the refrigeration principles to wor&. A compressor is used to

compress the refrigerant gas to a higher temperature. The hot gas is then cooled !

a heat e4changer. The heat from the hot gas is dissipated to the outdoors through

cooling towers or fans. The hot gas, after !eing cooled, reverts !ac& to a li5uid


7/15

state. This is the propert of most refrigerants, to !e li5uid at normal room

temperatures and pressures. This li5uid is then led through a valve or ori"ce. The

li5uid !ecomes e4panded in volume after passing through this restriction. The

e4pansion of volume through the e4pansion valve or ori"ce !rings a!out a cooling

e'ect. Heat is a!sor!ed when the li5uid !ecomes a gas. The cooling e'ect is used

to cool chilled water through a heat e4changer. The chilled water sstem is thenpumped and distri!uted to all the air handling units at various /oors in the !uilding.

The air handling units contain fans for moving air through cooling coils. The indoor

air is thus cooled.

The /ow of the heat in central air conditioning sstem can !e summari=ed as

follows

Heat is transferred from the air in the rooms to chilled water at the air handling

units.

The chilled water is pumped through the chiller and the heat is transferred to the

refrigerant. The refrigerant is cooled ! cooling water circulating in the condenser of the chiller.

The heated cooling water is passed through cooling towers where the heat is

dissipated to the atmosphere ! fans.

Tpes of Chillers

Chillers are a general term for air conditioning units using chilled water as a

distri!uting agent. The are named according to the tpe of compressors the use.

Centrifugal chillers use centrifugal impellers and high rotational speeds to wor&.

8eciprocating chillers contain pistons, cran&shafts, suction valves and discharge

valves. @crew chillers use screw shafts to compress the refrigerant gas. i'erent

manufacturers produce their own designs !ased on these !asic ideas ofcompression. @ome manufacturer design for multistage compression, some have

enclosed electrical motors in the refrigerant circuit, while others have e4ternal

motors. Man of the control sstems are designed to suit the di'erent

manufacturers. The settings of controls and machine design also depend on the

refrigerant the use. There are also di'erent con"gurations for air or water cooled

condensers.

The lu!rication oil for chillers is special oil that is compati!le and a!le to mi4 freel

with the refrigerant. All manufacturers have their own arrangements to suit their

own designs, with oil heaters, oil !ath, oil pumps, and others.

Centrifugal Chiller

+arge si=ed chillers have centrifugal fans to compress the refrigerant gas. As with

an highGspeed centrifugal fans, these chillers are suscepti!le to surging if the

sstem is not matched properl. #henever there is a sudden change in the heat

loads or speeds, there is a possi!ilit of surging. Man manufacturers design their

machines to cater for these sudden changes. or normal usage, there is almost no


8/15

pro!lem in this area. Dormall the condensers are water cooled, and the wor& in

con?unction with cooling towers.

8eciprocating Chiller

The motors of reciprocating chillers are usuall totall enclosed inside the

refrigerant circuit. The pistons are made small in si=e. Necause of the reciprocating

movements of the several pistons (K to pieces), these chillers are usuall nois.

The commonl use 8G%% refrigerant.


9/15

Cooling

towers are

used in

central air

conditioning

sstems. Thefunction of

the cooling

tower is to

cool the warm

water from

the chiller

condenser.

ollowing the

central air

conditioning

sstem ccle,

the heat from

the rooms in a

!uilding is

transferred to

chilled water,

which is then

transferred

into the

refrigerant,

and "nall tothe cooling

water. The

cooling tower

is at the "nal

point of the

heat transfer.

The heat is

transferred to

the

atmosphere.

The heat in

the cooling

water is

removed !

letting moving

air come into


10/15

contact with

it. #ater is

normall

spread out

and allowed

to drop down! gravit

from a height.

Ilastic "llings

are arranged

so as to

increase the

wetted

surface of the

water while it

is dropping,

while at the

same time

provide !etter

contact

!etween the

air passages

and the water.

There are

!asicall %

tpes ofdesigns

Cross low

Counter low

Cross low

As the name suggests, the /ow of water is at right angles to the /ow of air. The

cooling tower for this tpe of design is usuall shaped li&e a !o4. #arm water is

pumped to the top of the cooling tower where it is distri!uted to the sides and

allowed to drop through small holes. Ilastic air inta&e louvers at the sides of thecooling tower allow the water to spread out while dropping. Air from the outside is

suc&ed into the cooling tower ! several fans located at the top. The incoming air

comes into contact with the dropping water, and the latter is cooled. The cooled

water is collected at the !ottom of cooling tower. This water is then pumped out

again and circulated through the chiller. The heat from the chiller is transferred to it


11/15

again. The warm water then returns !ac& to the top of the cooling tower and the

ccle starts again.

Counter low

Counter /ow cooling towers have the air passage /owing directl against the /ow of

the water. As with the cross /ow design, water is allowed to spread out with the help

of air inlet louvers. Their !ottle li&e shape characteri=es this tpe of cooling towers.

There is onl one single fan at the center. itted !elow the fan is a rotating water

pipe distri!utor. The pipes of the water distri!utor shoots water onl from one side.

The action of the water pressure shooting from one side rotates the distri!utor. The

water is thus dropped evenl over the air inlet louvers. The water dropping !

gravit meets head on with the up moving air current suc&ed in ! the fan. The air

cools the water. The water collected at the !ottom of the cooling tower is pumped

to the chiller, !ecomes heated up again, and is then returned !ac& to the cooling

tower for cooling.

#ater Treatment

En cooling towers, the cooling e'ect is achieved ! evaporation of a portion of the

water passing through it. As the water is evaporated, impurities remain in the

recirculating water. The concentration of the dissolved solids increases rapidl and

can reach unaccepta!le levels. En addition, air!orne impurities are often introduced

into the water. Ef the contaminants are not controlled, the can cause scaling,

corrosion, and sludge accumulations which can reduce heat transfer eFciencies.

En order to control the concentrations, it is necessar to !leed a small amount of

circulating water from the sstem and top up with fresh water. Ef the site conditions

are such that constant !leedGo' will not control scale or corrosion, chemical

treatment is necessar. 3ven with !leedGo' or chemical treatment, it is still

necessar to control !iological contamination. The growth of algae, and other

microorganisms can reduce sstem eFcienc and ma even contri!ute to

potentiall health ha=ards. Niocides are used to treat the water to control the

!iological growths

Cooling Tower #ater Management

Humidifcation

#hether it is a 5uestion of people feeling comforta!le and staing health inenclosed rooms or high performance computers continuing to function at their

pea& re?ected goods !eing &ept at a minimum, or fruit, vegeta!les and meat

staing fresh in cold stores to &eep their appeti=ing appearance (colour, form etc.)

the correct level of humidit is crucial for an optimal room climate.

34perts agree that a minimum of ;6: relative humidit is essential in order to

guarantee a room climate that is !oth health and comforta!le.

http://www.iklimnet.com/expert_hvac/cooling_tower_water.htmlhttp://www.iklimnet.com/expert_hvac/cooling_tower_water.html


12/15

En order to create the optimal conditions for highGtech industrial processes and for

peopleLs health, sterile, odourless and mineral free steam must !e produced. All

these re5uirements are met with the steam humidi"ers from Dordmann

3ngineeringS

Esothermal and adia!atic humidi"cation

The degree of moisture in the air can !e increased using two di'erent tpes of

procedures

J through isothermal humidi"cation (vapori=ation)

J through adia!atic humidi"cation (atomisation)

uring the isothermal humidi"cation process, water is !rought to !oiling point

causing water vapour to !e dispersed into the air. To change the state of water, an

e4ternal source of energ is re5uired. The temperature of the air is more li&el to

increase due to the high temperature of the water vapour.

uring the adia!atic humidi"cation process the water is "nel atomised (aerosol)

and mi4es with the air. Through this process, the temperature in the am!ient air can

decrease so much that it is necessar for it to !e reheated.

Electrode steam humidifcation

The heating sstem using electrodes

came into use at the !eginning of the

%6th Centur in countries with advancedelectri"cation. At that time industrial

water was !rought to around >6

degrees in large &ettles using graphite

electrodes.

En the si4ties, electrode heating was

further developed for the purposes of

steam generation. 3lectrode heating is

for evaporators in which the water is

!rought to !oiling point. The water itself

plas the part of the heating resistance. This guarantees an e4tremel e'ective

transformation of the electrical energ.

ue to the high wor&ing temperature a

micro!eGfree steam of the highest

5ualit is generated. The can !e used

with normal tap water and do not need


13/15

an e4cessive amount of servicing. ue

to the high steam temperature of

appro4. $667C all tpes of !acteria are

destroed and the ris& of

microorganisms !uilding up is

eliminated. The pure, hgienichumidi"cation ! using sterile steam is

isothermal. Using this process is more

economical as the room air is not cooled

down, therefore eliminating the

necessit to reheat it.

Electrode steam humidifcation manuacturer *Nordmann Engineering

e"nition of Humidi"cation Terms

Calculation of humidi"cation load

ehumidi"cation

ehumidifer

ehumidi"cation is the removal of water vapor from air, de"nition, and sorption

dehumidi"cation e5uipment has !een designed and operated successfull for

sstem pressures ranging from su!atmospheric to as high as K666 psi. The term

dehumidi"cation is normall limited to e5uipment that operates at essentiall

atmospheric pressures and is !uilt to standards similar to other tpes of airGhandling

e5uipment. or dring gases under pressure, or li5uids, the term drer or

dehdrator is normall used.

Dothing turns a hot da more oppressive than high humidit. En rooms that donBt

reall merit an air conditioner, or to cut down on the use of an air conditioner,

simpl run a dehumidi"er to ma&e living more !eara!le.

The recommended humidit level inside our home during the summer is around ;6

to 96 percent, and high indoor humidit can ma&e ou uncomforta!le and adversel

a'ect our home. Must smells, peeling wallpaper, warped wood, !listering paint

and moisture dripping from water pipes indicate e4cessive humidit and the need

for a dehumidi"er.

ehumidi"ers remove e4cess humidit ! drawing moist room air over cold

refrigerated coils. The moisture in the air condenses into droplets as it passes over

http://www.nordmann-engineering.com/http://www.iklimnet.com/expert_hvac/humidification_terms.htmlhttp://www.nordmann-engineering.com/user_content/editor/files/Nordmann/nordmanncalcsetup.exehttp://www.iklimnet.com/expert_hvac/dehumidifier.htmlhttp://www.nordmann-engineering.com/http://www.iklimnet.com/expert_hvac/humidification_terms.htmlhttp://www.nordmann-engineering.com/user_content/editor/files/Nordmann/nordmanncalcsetup.exehttp://www.iklimnet.com/expert_hvac/dehumidifier.html


14/15

the cold surfaces in the dehumidi"er and into a container. ried air then returns to

the room at appro4imatel its original temperature.

@ome commercial applications of dehumidi"cation include

+owering relative humidit to facilitate manufacturing and handling of hgroscopic

materials

+owering the dew point to prevent condensation on products manufactured in lowG

temperature processes

Iroviding protective atmospheres for the heat treatment of metals

Controlling humidit in warehouses and caves used for storage

Ireserving ships, aircraft, and industrial e5uipment that would otherwise

deteriorate

Maintaining a dr atmosphere in a closed space or container, such as the cargo

hold of a ship or numerous static applications

3liminating condensation and su!se5uent corrosion

ring air to speed the dring of heatGsensitive products, such as cand, seeds,and photographic "lm

ring natural gas

ring gases that are to !e li5ue"ed

ring instrument air and plant air

ring process and industrial gases

ehdration of li5uids

rostGfree cooling for lowGtemperature process areas such as

!rewer fermenting, aging, "ltering, and storage cellars !last

free=ers and refrigerated warehouses

rostGfree dehumidi"cation for processes that re5uire air at a su!free=ing dew

point humidit

Methods of dehumidi"cations

Cooling

8efrigeration of the air !elow its dew point is the most common method of

dehumidi"cation. This method is advantageous when the gas is comparativel

warm, has a high moisture content, and when the outlet dew point desired is a!ove

;67. re5uentl, refrigeration is used in com!ination with desiccant dehumidi"ers

to o!tain an e4tremel low dew point at minimum cost.

+i5uid esiccant

+i5uid desiccant conditioners (a!sor!ers) contact the air with a li5uid desiccant,

such as lithium chloride or glcol solution . The water vapor pressure of the solution

is a function of its temperature and its concentration. Higher concentrations and

lower temperatures result in lower water vapor pressures.


15/15

Documents

Heating Coil in the Main Air Handling Unit