GOVERNMENT POLYTECHNIC

MUZAFFARPUR

LAB MANUAL OF Thermal Engineering Lab

SUBJECT CODE – 1625406

Government Polytechnic Muzaffarpur

Name of the Lab: Thermal Engineering Lab

Subject Code: 1625406

List of Experiments

Exp.

No.

Experiments Name Page No.

1 Study and Trial on solar water heating system. 1-3

2 To determine the thermal conductivity of given metal rod. 4-6

3 To determine Stefan Boltzmann Constant for radiation heat transfer 7-9

4 Study and compare various heat exchangers such as radiators, evaporators,

condensers, plate heat exchangers etc.

10-13

5 Report on visit to wind power generation plant / biogas plant /

hydraulic power plant.

14

6 Report on visit to sugar factory / Dairy / steam power plant with

specifications of boiler and list of mountings and accessories.

15

1

EXPERIMENT NO - 1 AIM: Study and Trial on solar water heating system.

THEORY:

We are blessed with Solar Energy in abundance at no cost. The solar radiation incident on the

surface of the earth can be conveniently utilized for the benefit of human society. One of the

popular devices that harness the solar energy is solar hot water system (SHWS). A solar water

heater consists of a collector to collect solar energy and an insulated storage tank to store hot water.

The solar energy incident on the absorber panel coated with selected coating transfers the hat to

the riser pipes underneath the absorber panel. The water passing through the risers get heated up

and is delivered the storage tank. The re-circulation of the same water through absorber panel in

the collector raises the temperature to 80 C (Maximum) in a good sunny day. The total system

with solar collector, storage tank and pipelines is called solar hot water system.

Broadly, the solar water heating systems are of two categories. They are: closed loop system and

open loop system. In the first one, heat exchangers are installed to protect the system from hard

water obtained from borewells or from freezing temperatures in the cold regions. In the other type,

either thermosyphon or forced circulation system, the water in the system is open to the atmosphere

at one point or other. The thermosyphon systems are simple and relatively inexpensive. They are

suitable for domestic and small institutional systems, provided the water is treated and potable in

quality. The forced circulation systems employ electrical pumps to circulate the water through

collectors and storage tanks.

The choice of system depends on heat requirement, weather conditions, heat transfer fluid quality,

space availability, annual solar radiation, etc. The SHW systems are economical, pollution free

and easy for operation in warm countries like ours.

Based on the collector system, solar water heaters can be of two types.

Flat Plate Collectors (FPC) based Solar Water Heaters

The solar radiation is absorbed by Flat Plate Collectors which consist of an insulated outer metallic

box covered on the top with glass sheet. Inside there are blackened metallic absorber (selectively

coated) sheets with built in channels or riser tubes to carry water. The absorber absorbs the solar

radiation and transfers the heat to the flowing water. There are 60 BIS approved manufacturers of

Solar Flat Plate Collectors.

Evacuated Tube Collectors (ETC) based Solar Water Heaters

Evacuated Tube Collector is made of double layer borosilicate glass tubes evacuated for providing

insulation. The outer wall of the inner tube is coated with selective absorbing material. This helps

absorption of solar radiation and transfers the heat to the water which flows through the inner tube.

There are 44 MNRE approved ETC based solar water heating suppliers.

2

Solar water heating is now a mature technology. Wide spread utilization of solar water heaters can

reduce a significant portion of the conventional energy being used for heating water in homes,

factories and other commercial and institutional establishments. Internationally the market for

solar water heaters has expanded significantly during the last decade.

Salient Features of Solar Water Heating System

Solar Hot Water System turns cold water into hot water with the help of sun’s rays.

Around 60 deg. – 80 deg. C temperature can be attained depending on solar radiation,

weather conditions and solar collector system efficiency.

Hot water for homes, hostels, hotels, hospitals, restaurants, dairies, industries etc.

Can be installed on roof-tops, building terrace and open ground where there is no shading,

south orientation of collectors and over-head tank above SWH system.

SWH system generates hot water on clear sunny days (maximum), partially clouded

(moderate) but not in rainy or heavy overcast day.

Only soft and potable water can be used.

Stainless Steel is used for small tanks whereas Mild Steel tanks with anticorrosion coating

inside are used for large tanks.

Solar water heaters (SWHs) of 100-300 litres capacity are suited for domestic application.

Larger systems can be used in restaurants, guest houses, hotels, hospitals, industries etc.

Fuel Savings:

A 100 liters capacity SWH can replace an electric geyser for residential use and saves 1500 units

of electricity annually.

Avoided utility cost on generation

The use of 1000 SWHs of 100 liters capacity each can contribute to a peak load shaving of 1 MW.

Environmental benefits

A SWH of 100 liters capacity can prevent emission of 1.5 tonnes of carbon dioxide per year.

Life: 15-20 years

Approximate cost: Rs.15000- 20,000 for a 100 liters capacity system and Rs.110-150 per installed

liter for higher capacity systems

Payback period: 3-4 years when electricity is replaced

4-5 years when furnace oil is replaced

5-6 years when coal is replaced

Though the initial investment for a solar water heater is high compared to available conventional

alternatives, the return on investment has become increasingly attractive with the increase in prices

of conventional energy. The payback period depends on the site of installation, utilization pattern

and fuel replaced.

3

Evacuated tube collector (ETC) based solar water heater

4

EXPERIMENT NO - 2 AIM: To determine the thermal conductivity of given metal rod

APPARATUS: Experimental setup of metal rod

THEORY:

Write the theory on following points

1. Definition of Heat transfer, applications, three modes of heat transfer with their governing

laws, definition of thermal conductivity, and thermal conductivity of important materials

2. Terms in three dimensional heat transfer equation and definition of thermal diffusivity

3. Variation of thermal conductivity with temperature in solids, liquids and gases

DESCRIPTION OF THE APPARATUS:

The apparatus consists of the aluminum rod of 200mm test section. Heat is provided by means

of band heater at one end and released through water jacket arrangement at another end.

Thermocouples are provided at suitable points to measure the surface and water temperatures.

Proper insulation is provided to minimize the heat loss in radial direction. The temperature is

shown by means of the digital indicator on the control panel, which also consists of heater

regulator and other accessories with instrumentation having good aesthetic looks and safe design.

PROCEDURE:

1. Give necessary electrical and water connections to the instrument.

2. Switch on the MCB and console ON to activate the control panel.

3. Set the voltage in the range of 70-80 volts

4. Start the cooling water supply through the water jacket (make sure it should not to exceed

3 lpm).

5. Note the temperature at different points, when steady state is reached.

6. Repeat the experiment for different heater input.

7. After the experiment is over, bring the voltage to minimum, switch off the heater and then

main, allow the water to flow for some time in the water jacket and then stop it.

SPECIFICATIONS:

1. Type of Material =Aluminium

2. Diameter of the metal rod=50mmPES I-

3. Test length of the metal rod=200mm

4. Distance between two consecutive thermocouples=50mm

5. Distance between First end and first thermocouple, last thermocouple and last end=25mm

6. Thermocouple type-K type (Cr-Al)

7. Maximum voltage and current range=150 volts

5

PRECAUTIONS:

1. Do not give heater input without the supply of water.

2. Input should be given very slowly.

3. Run the water in the jacket for about 5 min after the experiment.

4. Do not run the equipment if the voltage is below 180V.

5. Check all the electrical connections before running.

6. Before starting and after finishing the experiment the heater controller should be in off

position.

7. Do not attempt to alter the equipment as this may cause damage to the whole system.

6

EXPERIMENTAL SETUP OF THERMAL CONDUCTIVITY OF METAL ROD

7

EXPERIMENT NO - 3 AIM: To determine Stefan Boltzmann Constant for radiation heat transfer

APPARATUS: Stefan Boltzmann Apparatus, stop watch

THEORY: Write theory on the following topics

1. Definition of radiation heat transfer

2. Characteristics of radiation heat transfer

3. Stefan Boltzmann law

4. Intensity of radiation

5. Lambert’s cosine law

6. Solar radiation and greenhouse effect

DESCRIPTION OF THE APPARATUS:

The apparatus consists of

1. Copper hemispherical enclosure with insulation.

2. SS jacket to hold the hot water.

3. Overhead water heater with quick release mechanism and the thermostat to generate and

dump the hot water.

4. Heater regulator to supply the regulated power input to the heater.

5. Thermocouples at suitable position to measure the surface temperatures of the absorber

body.

6. Digital Temperature Indicator with channel selector to measure the temperatures.

7. Control panel to house all the instrumentation.

With this the whole arrangement is mounted on an aesthetically designed self-sustained MS

powder coated frame with a separate control panel.

PROCEDURE:

1. Fill water slowly into the overhead water heater.

2. Switch on the supply mains and console.

3. Switch on the heater and regulate the power input using the heater regulator. (Say 60 – 85

C)

4. After water attains the maximum temperature, open the valve of the heater and dump to

the enclosure jacket. IT -

5. Wait for about few seconds to allow hemispherical enclosure to attain uniform temperature

– the chamber will soon reach the equilibrium. Note the enclosure temperature.

6. Insert the Test specimen with the sleeve into its position and record the temperature at

different instants of time using the stop watch.

7. Plot the variation of specimen temperature with time and get the slope of temperature

versus time variation at the time t = 0 sec

8

8. Calculate the Stefan Boltzman’s constant using the equations provided.

9. Repeat the experiment 3 to 4 times and calculate the average value to obtain the better

results.

SPECIFICATIONS:

1. Material of the specimen=copper

2. Mass of the specimen=4.7 g

3. Specific heat of the specimen=410J/kgK

4. Diameter of the specimen=15mm

5. Type of thermocouple= K type (Cr-Al)

PRECAUTIONS:

1. Check all the electrical connections.

2. Do not run the equipment if the voltage is below 180V.

3. Do not switch on the heater without water in the overhead tank.

4. Do not turn the heater regulator to the maximum as soon as the equipment is started.

5. Do not attempt to alter the equipment as this may cause damage to the whole system.

9

10

EXPERIMENT NO - 4 AIM:

Study and compare various heat exchangers such as radiators, evaporators, condensers, plate heat

exchangers etc.

THEORY

Heat exchangers are the device in which the heat is transferred from one fluid to another.

Exchange of heat is required at many industrial operations as well as chemical process.

Common examples of heat exchanger are radiator of car, condenser of a refrigeration unit

or cooling coil of an air conditioner.

Heat exchangers are of three types –

i) Transfer type – in which both fluids pass through the exchanger and heat gets

transferred through the separating walls between the fluids.

ii) Storage type – in this, firstly the hot fluid passes through a medium having high

heat capacity and then cold fluid is passed through the medium to collect the heat.

Thus hot and cold fluids are alternately passed through the medium.

iii) Direct contact type – in this type, the fluids are separated but they mix with

each other and heat passes directly from one fluid to other.

Transfer type heat exchanger are the type most widely used in transfer type heat

exchangers, three type of flow arrangements are used, viz. parallel, counter or cross flow.

In parallel flow, both the fluids flow in the same direction while in counter flow, they flow

in the opposite direction. In cress flow, they flow at right angle to each other.

The ‘DYNAMIC’ apparatus consists of two concentric tubes in which fluid pass. The hot

fluid is hot water, which is obtained from an electric geyser. Hot water flow through the

inner tube, in one direction. Cold fluid is cold water, which flows through the annulus.

Control valves are provided so that direction of cold water can be kept parallel or opposite

to that of hot water. Thus, the heat exchanger can be operated either as parallel or counter

flow heat exchanger. The temperatures are measured with thermometers. Thus, the heat

transfer rate, heat transfer coefficient, L. M. T. D. and effectiveness of heat exchanger can

be calculated for both parallel and counter flow.

SPECIFICATIONS-

1) Heat exchanger – a) Inner tube - θ 12.7mm O. D., θ 11.7mm I. D. copper tube

b) Outer tube - θ 25mm NB G. I. Pipe.

c) Length of heat exchanger is – 1 m.

2) Electric heater – 3 kw capacity to supply hot water.

3) Valves for flow and direction control – 5 Nos.

4) Thermometers to measure temperatures – 10 to 110 0C – 4 Nos.

11

5) Measuring flask and stop clock for flow measurement.

EXPERIMENTAL PROCEDURE –

1. Start the water supply. Adjust the water supply on hot and cold sides. Firstly, keep

the valves V2 and V3 closed and V1 – V4 opened so that arrangement is parallel flow.

2. Put few drops of oil in thermometer pockets. Put the thermometer in the

thermometer pockets.

3. Switch ‘ON’ the geyser. Temperature of water will start rising. After temperature

become steady, note down the readings and fill up the observation table.

4. Repeat the experiment by changing the flow.

5. Now open the valves V2 and V3 and then close the valves V1 and V4. The

arrangement is now counter flow.

6. Wait until the steady state is reached and note down the readings.

OBSERVATION TABLE

HOT WATER COLD WATER

TYPE OF TEMPERATURE TIME FOR 1 TEMPERATURE TIME FOR 1

FLOW LIT. WATER LIT. WATER

IN ˚C OUT ˚C Xh Sec. IN ˚C OUT ˚C Xc Sec.

PARALLEL

FLOW

COUNTER

FLOW

CALCULATIONS –

1) Hot water inlet temp. thi =

Hot water outlet temp. tho = 0C

2) Hot water flow rate mh –

Let time required for 1 lit. of water be xh sec.

Mass of 1 lit. water = 1 kg.

mh = 1 / xh kg/s.

3) Heat given by hot water (inside heat transfer rate)

qh = mh . cp .(thi – tho) watts

12

Where cp = Specific heat of water = 4200 J/kg . K

4) Logarithmic mean temperature different (LMTD)

Ti – To

LMTD = Tm = -------------------

In (Ti / To)

Where, for parallel flow for counter flow

Ti = thi – tci Ti = thi – tco

To = tho – tco To = tho – tci

5) Overall heat transfer coefficient, U –

a) Inside overall heat transfer coefficient, Ui –

Inside diameter of tube = 0.011 m

∴ inside surface area of the tube, Ai = Π . di. L = Π x 0.011 x 1 = 0.03454 m2

Now, qh = Ui . Tm . Ai

∴ Ui = qh / ( Tm . Ai) w / m2 0C

b) Outside overall heat transfer coefficient, Uo –

Outside diameter of tube = 0.012m

Outside surface area of the tube, Ao = Π . do. 1 = Π x 0.012 x 1

= 0.03768 m2

Similarly, qc = Uo . Tm . Ao

∴ Uo = qo / Tm . Ao

6) Effectiveness of heat exchanger –

Rate of heat transfer in heat exchanger

∑ = ----------------------------------------------------

Maximum possible heat transfer rate

Mh . cp. (thi – tho)

∑ = --------------------------

(mc cp) (tco – tci)

13

where, (m cp) is smaller of two capacity rates of mh or mc.

RESULT –

HEAT TRANSFER RATE LMDT

Inside (Watts) Outside (watts) 0C Ui Uo

w/m2 0C w/m2 0C

PARALLEL

FLOW

COUNTER

FLOW

PRECAUTIONS –

1) Never switch on the geyser unless there is water supply through it.

2) If the red indicator on geyser goes off during operation, increase the water supply,

because it indicates that water temperature exceeds the set limit.

3) Ensure steady water flow rate and temperature before noting down the readings,

as fluctuating water supply can give erratic results.

14

EXPERIMENT NO – 5 AIM:

Report on visit to wind power generation plant / biogas plant / hydraulic power plant.

THEORY:

In this particular visit, students are expected to visit wind power generation plant/ biogas plant/

hydraulic power plant where they can learn thorough things about the plant and processes of the

power generation in those plants. They are also intended to write a Technical Report on the visit.

15

EXPERIMENT NO – 6 AIM:

Report on visit to sugar factory / Dairy / steam power plant with specifications of boiler and list

of mountings and accessories.

THEORY:

In this particular visit, students are expected to visit sugar factory / Dairy / steam power plant

where they can learn thorough things about the plant and processes of those plants. They are also

intended to write a Technical Report on the visit.