refrigeration and air conditioning (2161908) · a laboratory manual for refrigeration and air...

1

A Laboratory Manual for

Refrigeration and Air

Conditioning (2161908)

6th Semester

Mechanical Engineering

DARSHAN INSTITUTE OF ENGINNERING

AND TECHNOLOGY, RAJKOT

Campus: At Hadala, Rajkot-Morbi Highway, Near Water Sump, Rajkot 363650 Phone:

+91-2822-293010 Web: www.dashan.ac.in

2

DARSHAN INSTITUTE OF ENGINNERING

AND TECHNOLOGY, RAJKOT

Certificate

This is to certify that, Mr. / Ms.__________________________

Enroll no.__________________ of Eighth semester Bachelor of

Mechanical Engineering has completed the term work satisfactorily

in Refrigeration and Air conditioning (2161908) for the academic

year 2015 as prescribed in the curriculum.

Place: _________ Enrolment No.:____________

Date: _________ Exam. Seat No.:___________

Subject Teacher Head of the Department

3

DARSHAN INSTITUTE OF ENGINNERING AND

TECHNOLOGY

Department of Mechanical Engineering - 6th Semester

Refrigeration and Air Conditioning (2161908)

List of Experiments

Sr.

No. Title

Starting

Date

Date of

Completion

Assessment

Marks Sign Remark

1.

To study and calculate

capacity & COP of

Vapour Compression

Refrigeration(VCR)

system

2.

To study and calculate

capacity & COP of

Vapour Absorption

Refrigeration(VAR)

(Electrolux

Refrigeration) system

3.

Study of Air

Conditioning system

and calculate COP of

Air Conditioning

system with the help of

P-H Chart

4.

To carry out Heating

process of fresh air and

find out relevant

parameter of air and

also plot the process on

psychrometric chart.

5.

To carry out Cooling

process of fresh air and

find out relevant

parameter of air and


psychrometric chart.

6. To carry out Heating

and humidification

4

process and find out

relevant parameters and


psychrometric chart

7.


and humidification




psychrometric chart

8.


and dehumidification




psychrometric chart

6

1. STUDY OF VAPOUR COMPRESSION REFRIGERATION SYSTEM AND

CALCULATE COP OF SYSTEM WITH THE HELP OF P-H CHART

1. Objective:

To Study Refrigeration test rig and to study the vapour compression refrigeration cycle.

2. Aim:

To calculate co-efficient of performance with the help of P-h diagram.

3. Nomenclature: Nom Column Heading Units Type

Cos Φ Power factor. Given

Cp Specific heat of water kJ/kgoC. Given

(C.O.P.)Rel(b) Relative co-efficient of performance for batch operation Calculated

(C.O.P.)Rel(c) Relative co-efficient of performance for continuous operation Calculated

(C.O.P.)Th Theoretical co-efficient of performance. Calculated

(C.O.P.)Act(b) Actual co-efficient of performance. for batch operation Calculated

(C.O.P.)Act(c) Actual co-efficient of performance for continuous

Operation

Calculated

CWAct Actual compression work kJ/kg Calculated

H1 Enthalpy of refrigeration effects at compressor inlet kJ/kg Calculated

H2 Enthalpy of compressor work at compressor outle kJ/kg Calculated

H3 Enthalpy of sub cooling at the outlet of condenser kJ/kg Calculated

H4 Enthalpy of refrigerant inlet of evaporator kJ/kg Calculated

I Ammeter reading Amp. Measured

m(b) Mass of water for batch operation kg/sec. Calculated

m(c) Mass of water for continuous operation kg/sec. Calculated

W Heater Wattage KW Given

P1 Pressure at compressor suction kg/cm2 Measured

P2 Pressure at compressor discharge kg/cm2 Measured

REAct(b) Actual Refrigeration effect for batch operation kJ/sec Calculated

REAct(c) Actual Refrigeration effect for continuous operation kJ/sec Calculated

T1 Temperature at compressor suction C Measured

T2 Temperature at compressor discharge C Measured

T3 Temperature at condenser outlet C Measured

T4 Temperature at evaporator inlet C Measured

T5 Temperature of water inlet for continuous operation C Measured

T6 Temperature of, water in evaporator for batch

cooling / water outlet for continuous operation

C Measured

T6i Temperature of water before cooling in batch operation C Measured

T Time sec Measured

V Voltmeter reading Volts Measured

Vwe Volume of water in evaporator for batch cooling Ltrs Measured

7

Vwr Flow rate of water through evaporator for continuous cooling LPH Measured

w Density of water kg/m3 Given

4. Introduction:

Refrigeration may be defined as the process of removing heat from a substance under controlled

conditions. It is used for the manufacture of ice and similar products.

Refrigeration is the branch of science that deals with the process of reducing and maintaining the

temperature of a space or material below the temperature of the surroundings. Heat must be

removed from the body being refrigerated and transferred to another body whose temperature is

below that of the refrigerated body. This is widely used for cooling of storage chambers in which

perishable foods, drinks, and medicines are stored. The refrigeration has also wide applications in

submarine ships, aircrafts.

5. Theory:

Fig. 1.1 Schematic diagram of Vapour Compression Refrigeration System

5.1 Vapour Compression Cycle: The refrigerant starts at some initial state or condition, passes through a series of processes in a

definite sequence and returns to the initial condition. This series of processes is called a cycle.

8

The Standard Vapour Compression Cycle (SVCC) consists of the following processes:

Process 1-2: Reversible adiabatic compression from the saturated vapour to a super heated

Condition (electrical) input.

Process 2-3: Reversible heat rejection at constant pressure (de-superheating and condensation of

the refrigeration

Process 3-4: Irreversible constant enthalpy expansion from high pressure saturated liquid to a

low- pressure liquid and small amount of vapour.

Process 4-1: Reversible heat absorption at constant pressure from space to be cooled.

Fig. 1.2 Pressure- Enthalpy Diagram

5.2 Standard Vapour Compressor Cycle :

Compressor:

The main function of compressor is to raise the pressure and temperature of the refrigerant by the

compression of the refrigerant vapour and then pump it into the condenser

Condenser:

Condense the vapour refrigerant into the liquid by condenser fan and passes it into the receiver

tank for recirculation.

Capillary Tube:

It expands the liquid refrigerant at high pressure to the liquid refrigerant at low pressure so that a

measured quantity of liquid refrigerant is passed into the evaporator.

Evaporator:

Evaporates the liquid refrigerant by absorbing the heat into vapour refrigerant and sends back into

the compressor.

Evaporator

Capillary Tube

Condenser

Compressor

9

Drier:

A drier is used in between the condenser and expansion device. The main function of the drier is

to absorb the moisture from the liquid refrigerant and filter the dust particles.

Accumulator:

An accumulator is fitted in between the Evaporator and Compressor. It prevents the liquid

refrigerant from entering the compressor.

Co-efficient of Performance: The coefficient of performance of (C.O.P.) of a refrigerating cycle is defined as the ratio between

net refrigeration (output) and compressor work (input).

CW

REPOC ..

41 HHRE

12 HHCW

12

41...HH

HHPOC

6. Description:

The set up demonstrates the basic principal of a refrigeration cycle. The test rig is designed for

the study of Vapour Compression Refrigeration Cycle. The set up consist of voltmeter,

amperemeter, Energymeter, rotameter, heater. Instrumentation is done to measure the temperature

& pressure wherever necessary

7. Utilities Required:

Electricity Supply: Single Phase, 220 V AC, 50Hz, 5-15Amp. Combined socket with earth

connection.

Water Supply @ 2 LPM at 1 Bar.

Floor Drain required.

Floor Area Required: 1.5 m x 1m

8. Experimental Procedure:

8.1 Starting Procedure (For Batch Operation):

1. For batch operation fill known amount of water in the evaporator tank.

2. Put the temperature sensor T6 in the evaporator tank.

3. Note down the reading of temperature T6i.

4. Switch ON the mains power supply.

5. Switch ON the compressor.

6. Wait for 2-3 minutes to switch ‘ON’ the compressor.

7. Open the valves below the pressure gauges.

8. Switch ON the pump for 30 sec after every 10 minutes.

9. After 10 minutes, note the temperature sensors reading.

10. Note down the voltage and current.

11. Note down the time.

12. Note down the reading of pressure gauges.

10

13. Note all the reading after every 10 minute till the temperature of water in evaporator comes

constant.

14. Repeat the experiment for different volume of water.

15. Repeat the experiment by switching ‘ON’ the heater (load condition)

8.2 Starting Procedure (For Continuous Operation):

1. For continuous operation, open the valve and drain the water.

2. Connect pipe evaporator water outlet to drain.

3. Connect water supply to rotameter.

4. Set a flow rate of water with help of valve.

5. Put the temperature sensor T6 at evaporator water outlet.

6. Switch ON the mains power supply.

7. Switch ON the compressor.

8. Wait for 2-3 minutes to switch ‘ON’ the compressor.

9. Open the valves below the pressure gauges.

10. After 10 minutes, note the temperature sensors reading.

11. Note down the voltage and current.

12. Note down the time.


14. Note all the reading after every 10 minute till the temperature of water in

evaporator comes constant.

15. Repeat the experiment for different flow rates of water.

16. Repeat the experiment by switching ‘ON’ the heater (load condition).

8.3 Closing Procedure:

1. Switch ‘OFF’ the main supply.

2. Close water supply to rotameter.

3. Open the valve to drain out the water.

9. Observation & Calculations:

9.1.a Data:

Power factor Cos Φ = 0.7

Density of water w = 1000 kg/m3

Specific heat of water Cp = 4.186 kJ/kg oC

Heater Capacity W = …………….KW

9.1.b Observation Table:

T6i = ------------ (oC)

For Batch Operation

11

Sr.

No

t

min

P1

kg/cm2

P2

kg/cm2

T1

(oC)

T2

(oC)

T3

(oC)

T4

(oC)

T5

(oC)

T6

(oC)

Vwr

(LPH)

V

(Volts)

I

(Amp)

9.1. Calculations:

To Calculate Cop of the System

174.404847.0}548.3)04.0{( 1111 TPTH

082.413834.0}080.3)0183.0{( 2222 TPTH

441.194662.1}225.0)005.0{( 3233 TPTH

12

41..HH

HHPOC Th

43 HH

(A) For batch operation:

601000

t

Vm wwe

b

(kg/sec)

)( 66 TTCmRE ipbActb

(kJ/sec)

1000

CosIVCWAct

(kJ/sec)

Act

bAct

bActCW

REPOC .)..(

Th

Act

lPOC

POCPOC b

b ..

...)..( Re

9.1.c OBSERVATION TABLE:

T6i = ------------ (oC)

For continuous operation

Sr.

No

t

min

P1

kg/cm2

P2

kg/cm2

T1

(oC)

T2

(oC)

T3

(oC)

T4

(oC)

T5

(oC)

T6

(oC)

Vwr

(LPH)

V

(Volts)

I

(Amp)

(B) For continuous operation:

12

36001000

t

Vm wwr

c

(kg/sec)

)( 65 TTCmRE pccAct (kJ/sec)

1000

CosIVCWAct

(kJ/sec)

Act

cAct

cActCW

REPOC .)..(

Th

Act

clPOC

POCPOC c

..

...)..( Re

10. Precautions & Maintenance Instructions: 1. Never run the apparatus if power supply is less than 180 volts and above 230 volts.

2. Do not start unit, before putting the water in the evaporator.

3. During the observation do note open the evaporator.

11. Troubleshooting:

If electric panel is not showing the input on the mains light, check the main supply.

12. Conclusion

13. References:

12.1 Dossat, Roy J. (2004). Principles of Refrigeration. 4th Ed. ND: Pearson Education Pvt.

Ltd. pp 102-105,118-125

12.2 Jordan, Richard C. & Priester, Gayle B. (1966). Refrigeration & Air Conditioning. 2nd Ed.

ND: Prientice-Hall of India Pvt. Ltd. pp 16-23,423-429.

14

2. TO STUDY VAPOUR ABSORPTION REFRIGERATION SYSTEM AND

CALCULATE THE COP.

1. Objective:

To study Electrolux Refrigeration system.

2. Aim:

To determine COP of Vapour absorption refrigeration system.

3. Nomenclature:

Nom Column Heading Units Type

COP Co-efficient of Performance Calculated

T1 Temperature of generator oC Measured

T2 Temperature of condenser oC Measured

T3 Temperature of evaporator oC Measured

4. Introduction:

Electrolux refrigerator is a absorption type refrigeration system. In absorption refrigeration

system the vapour is drawn from the evaporator by absorption into liquid having high affinity

for refrigerant. The refrigerant is expelled from the solution by application of heat and its

temperature is increased. This refrigerant in the vapour form passes to the condenser where

heat is rejected and the refrigerant gets liquefied. This liquid again flows to the evaporator at

reduced pressure and the cycle is completed.

Absorber:

The main function of Absorber is the absorption of the refrigerant vapour by its weak or poor

solution in a suitable absorbent or adsorbent, forming a strong or rich solution.

Condenser:

Condenses the vapour refrigerant into the liquid by condenser fan and passes it into the

receiver tank for recirculation.

Evaporator:

Evaporates the liquid refrigerant by absorbing the heat into vapour refrigerant and sends back

to next run.

5. Theory:

The flow of fluids in the system has been shown in the diagram with different shadings and

the index of these shadings also indicated in diagram. Vertical boiler in which an aqua

solution of ammonia can range itself from distilled water at the bottom of the boiler to strong

ammonia vapour at the surface of liquid.

A water separator which is provided to remove water vapour so that they should not enter the

condenser, get condensed there and pass on to evaporator where chocking might occur due to

its freezing. The water vapour is formed in the boiler as some of the water may evaporate on

15

application of heat to the boiler. The separator is a jacket with liquid ammonia at pressure of

about 14 bar gauge for which the saturation temperature is about 40 ºC

The dehydrate ammonia gas gets condensed to liquid in the condenser and gravitates to ‘U’

tube which acts as seal for a gas to enter the evaporator, or any gas passing from evaporator

to condenser.

Fig. 2.1 Vapour Absorption Type Refrigeration System

In the evaporator, ammonia liquid comes across an atmosphere of hydrogen at about 12-bar

gauge. The plant is charged to a pressure of about 14 bar. Hence due to Dalton’s law of

partial pressure the pressure of ammonia gas should fall to about 2 bar gauge and the

saturation temperature corresponding to about 2 gauge is about –10 ºC. the temperature

surrounding the evaporator is much higher than this. Thus ammonia evaporates and produces

the refrigerating effect, i.e. absorbs the latent heat of vaporization at 2 bar gauge and about–

10 ºC from the space to be refrigerated.

In order to ensure continuous action, hydrogen gas has to be removed from ammonia vapors.

This is done in the absorber where a descending spray of very dilute ammonia liquid moseys

the ascending mixture of ammonia vapour and hydrogen. Ammonia vapour is readily

absorbed with evaluation of heat so that absorber has to be water jacketed or air cooled,

otherwise evaporation may take place in this unit and the absorption may cease.

Heat exchanger (Condenser): liquid heat exchanger is placed in between absorber and the

generator. This weak liquid gets cooled and strong liquid gets heated, thus is economized and

better thermal efficiency obtained. This heat exchanger is counter flow type. The strong

solution from the absorber is preheated on its way to generator or boiler and the dilute

solution on its way to absorber is cooled. This cooling of weak liquid also helps absorption

and reduces the cooling of absorber by external source.

Working:

1. Strong ammonia solution flows from the absorber vessel to the boiler.

2. When the ammonia solution is heated in the boiler, bubbles of ammonia as raises from the

pump.

16

3. The ammonia vapour passes into the condenser.

4. Weak ammonia solution flows into the tube.

5. Air circulating over the fins of the condenser. Cool down the vapour. Condensing it in

liquid ammonia.

6. Liquid ammonia flows through the pipe to the evaporator.

7. The hydrogen in the evaporator lowers the ammonia vapour pressure and makes it

evaporate.

8. This process extracts heat from the evaporator, which in turn extracts heat from the food

storage space. Thereby the temperature inside the refrigeration is lowered.

9. The mixture of hydrogen and ammonia passes from the evaporator to the absorber.

10. Weak ammonia solution is fed from the boiler system.

11. As it turns to the absorber vessel, it absorbs the ammonia from the ammonia/hydrogen

mixture and gets ready for another round in the boiler.


1. Electricity Supply: Single Phase, 220 VAC, 50 Hz, 5-15 amp socket with earth

connection.

2. Bench Area Required: 1 m x 0.5 m.


1. Ensure that all ON / OFF switches given on the panel are at OFF position.

2. Switch ON the main Supply.

3. Switch ON the refrigerator.

4. Record the temperatures when the steady state is achieved.

8. Observation & Calculation:

8.1 Observation Table: S. No. T1 (

oC) T2 (

oC) T3 (

oC)

8.2 Calculations:

15.27315.27315.273

15.27315.27315.273

321

213

TTT

TTTCOP

9. Precaution & Maintenance Instructions:

9.1 Never run the apparatus if power supply is less than 180 volts & above than 230 volts.

9.2 Unnecessary handling of equipment should be avoided.

9.3 Never open the refrigerator during the experiment.


17

10.1 If electric panel is not showing the input on the mains light, check the main supply.

11. Conclusion:

12. References:

11.1 Domkundwar, Arora (1995). A Course in Refrigeration & Air Conditioning. 5th Ed. IND:

Dhanpat Rai & CO. (P) Ltd. pp 6.4- 6.5.

19

3. STUDY OF AIR CONDITIONING SYSTEM AND CALCULATE COP OF AIR

CONDITIONING SYSTEM WITH THE HELP OF P-H CHART

1. Objective:

To study the vapour compression air conditioning cycle. And calculate the COP of the Air

conditioning cycle.

2. Aim:

To study the Vapour Compression air conditioning cycle

To calculate Co-efficient of performance (COP) by the use of P-H diagram

To measure dry bulb & wet bulb temperature of inlet and outlet air

3. Nomenclature:


Cos Φ Power Factor Given


C.O.P.Th Theoretical Co-efficient of performance Calculated

RE Refrigeration Effect kJ/ kg Calculated

CW Compressor Work KJ/Kg Calculated

H1 Enthalpy of refrigeration effects at

compressor inlet

kJ/ kg Calculated

H2 Enthalpy of compressor work at compressor

outlet

kJ/ kg Calculated

H3 Enthalpy of sub cooling at the outlet of

condenser

kJ/ kg Calculated

H4 Enthalpy of refrigerant inlet of evaporator kJ/ kg Calculated







Tdi Dry Bulb Temperature of air at inlet of duct C Measured

Twi Wet Bulb Temperature of air at inlet of duct C Measured

Tdo Dry Bulb Temperature of air at outlet of duct C Measured

Two Wet Bulb Temperature of air at outlet of duct C Measured

ρa Density of air Kg/m3 Given

Va Velocity of air flowing through duct m/sec Measured

X1 Humidity at inlet of duct Kg/Kg of dry air Measured

X2 Humidity at outlet of duct Kg/Kg of dry air Measured

X Change in Specific Humidity Kg/Kg of dry air Calculated

20

4. Introduction:

Air conditioning is the simultaneous control of the temperature, humidity, motion and purity

of the atmosphere in a confined space. Air conditioning applies in the heating season as well

as in the cooling season. The Air conditioning has wide applications in submarine ships,

aircrafts and rockets. Air conditioning is associated with the human comfort and controlling

the humidity ratio.

Air conditioning means "preparing the air as per required conditions of temperature, humidity

and velocity. The conditions required are different for different applications, e.g. a small

room requires air at about 24 - 26 °C where humidity control is not so important, or a

building may be air conditioned for supplying air of 24 - 26°C temperature & 50-60 %

relative humidity. Measurement rooms in factories are to be maintained at the temperature of

-20 °C. So depending upon the requirement, the air conditioning system is designed. A

complete air conditioning system has the following jobs.

1. Filtration of air, where it contains dirt or dust particles.

2. Deodorization of air.

3. Cooling of air in summer.

4. Dehumidification of air by cooling coil itself and again heating it, as may be required in

humid areas in summer.

5. Heating of air in winter.

6. Humidifying and heating of air as may be required in winter.

7. Circulating the conditioned air through the space to be air conditioned.

An air conditioning system may be provided with some or all the units required to perform

the above jobs, which is determined by conditioning requirements and cost aspects. A

window type air conditioner provides some filtration and cooling of air. In large buildings,

cooling, heating and humidification systems may be used, along with partial recirculation of

exhaust air. This is done as it will require a huge capacity plant to condition the whole fresh

air entering the space to be conditioned. Thus some air from the exhausted air which is at a

temperature lower than the ambient temperature is mixed with the entering fresh air. Total

recirculation is generally avoided in large installations as the exhausted air contains odors.

The Air Conditioning Test Rig comprises of the following components.

1. A conditioning unit consisting of cooling coil, heaters and humidifier

2. Fan with circulating duct.

3. Control and measurement panel

5. Block Diagram:

h1 Enthalpy of air at inlet of duct KJ/Kg of dry air Calculated

h2 Enthalpy of air at outlet of duct KJ/Kg of dry air Calculated

V Voltmeter Reading Volts Measured

I Ampere meter reading Amp. Measured

21

Fig. 3.1 Line Diagram of Air Conditioning Apparatus

6. Theory:

Air conditioning may be defined as the process of removing heat from a substance under

controlled conditions. It also includes the process of reducing and maintaining the

temperature of a body below the general temperature of its surroundings. This is widely used

for cooling of storage chambers in which perishable foods, drinks, and medicines are stored.

Fig. 4.2 shows the schematic of the unit with complete description.

Fig. 3.2 Block Diagram of Standard

Vapour Compression Cycle (SVCC)

COMPRESSOR:

The main function of compressor is to raise the pressure and temperature of the

refrigerant by the compression of the refrigerant vapour and then pump it into the

condenser.

CONDENSER:

Capillary

tube

Evaporator

Compressor

Condenser

22

Condense the high pressure vapour refrigerant into the high pressure liquid by

condenser fan and passes it into the receiver tank for recirculation

CAPILLARY TUBE:

Expands the liquid refrigerant at high pressure to the sub cooled liquid refrigerant at

low pressure so that a measured quantity of liquid refrigerant is passed into the

evaporator.

EVAPORATOR:

Evaporates the sub cooled liquid refrigerant by absorbing the sensible heat into

vapour refrigerant and sends back into the compressor.

VAPOUR COMPRESSION CYCLE:

The refrigerant starts at some initial state or condition, passes through a series of

processes in a definite sequence and returns to the initial condition. This series of

processes is called a cycle.

Fig. 3.3 Standard Vapour Compression Cycle (SVCC)

The Standard Vapour Compressor Cycle (SVCC) consists of the following processes:

Reversible adiabatic compression from the saturated vapour to a super-heated

condition.

Reversible heat rejection at constant pressure (sub cooling liquid and

condensation of the refrigerant)

Irreversible enthalpy expansion from saturated liquid to a low pressure sub

cool liquid.

Reversible heat addition at constant pressure.

COEFFICIENT OF PERFORMANCE (C.O.P):

23

The coefficient of performance of (C.O.P.) of a refrigerating cycle is defined as the

ratio between net refrigeration (output) and compressor work (input).

CW

REPOC ..

41 HHRE

12 HHCW

12

41..HH

HHPOC

7. Description:

The air-conditioning test rig unit is required to conduct experiments and demonstrate the

processes of heating, cooling, heating and humidification, cooling and dehumidification,

cooling and humidification of atmospheric air. The unit consists of a compressor. Both

evaporator and the air cooled condenser are mounted on board with separate fans. Air is

sucked from the room and is supplied to the room after conducting the different processes.

The system is provided with voltmeter, ampere meter, digital temperature indicator, air

heater, steam generator. The unit will be fitted with all instrumentation facilities so that

temperature and pressure can be measured at different points in the air-conditioning system.

Steam generator is provided from which steam comes directly to the air inlet of air

conditioning which is required for humidification purpose. Heating coil is provided for

heating of air and cooling coil is provided for cooling and dehumidification of air. Suitable

valves and fittings are fitted in the pipe line of steam. Water level indicator is provided to safe

guard of heater.


1. Electricity Supply: Single Phase, 220 VAC, 50 Hz, 5-15 Amp. Combined socket with earth

connection.

2. Floor Area Required: 2 m x 1 m


Starting Procedure:

1. Switch ‘ON’ the compressor.

2. Wait for 2-3 minutes for switch ‘ON’ the compressor.

3. Open the valves of pressure gauges.

4. After 10 minutes note down the reading of temperature sensor.


6. Note down the reading of inlet and outlet temperature of air.

7. Note down the reading of temperature and pressure after every 10 minutes till the

temperature of outlet of air come constant.

Closing Procedure:

1. Switch off the compressor.

24

2. Switch off the mains power supply.


10.1 Data:

Cos Φ = 0.7

a = 1.21 Kg/m3

10.2 Observation Table:

Va= …………… m/sec

Sr.No. t

min

P1

Bar

P2

Bar

T1

(C)

T2

(C)

T3

(C)

T4

(C)

Tdi

(C)

Twi

(C)

Tdo

(C)

Two

(C)

V I

10.3 Calculations:

To Calculate COP of the System:

723.415)652.0()98.1011.0( 1111 TPTH

723.415)652.0()98.1011.0( 2222 TPTH

93.199228.1 33 TH

12

41..HH

HHPOC Th

43 HH

1000

CosIVCW

KJ/sec

To calculate the specific humidity X1 and enthalpy of air h1 at temperature Tdi & Twi.

__________1 X (kg/kg of dry air)

h1 = (kJ/kg of dry air) [from psychrometric chart]

To calculate the specific humidity X2 and enthalpy of air h2 at temperature Tdo & Two



Heat rejected from the air = Change in enthalpy of air = R.E.

R.E. = h1 – h2

= (kJ/kg of dry air)

25

11. Precautions & Maintenance Instructions:

1. Operate the Valves gently.

2. Never run the apparatus if power supply is less than 180 volts and above 230 volts.

3. Duct should be free from dust particles.


1. If electric panel is not showing the input on the mains light, check the main supply.

2. If voltmeter showing the voltage given to heater but ampere meter does not, check the

connection of heater in control panel.

13. Conclusion:

14. References:

1. Dossat, Roy J. (2004). Principles of Refrigeration. 4th Ed. ND: Pearson Education

Pvt. Ltd. pp 125-126.

2. Jordan, Richard C. & Priester, Gayle B. (1966). Refrigeration & Air Conditioning. 2nd

Ed. ND: Prientice-Hall of India Pvt. Ltd. pp 444-447,455-466.

3. S.C. Arora, S Domkundwar (1995). A Course In Refrigeration And Air Conditioning.

5th Ed. Dhanpat Rai & Sons pp 16.1-16.24.

4. Psychometric Chart.

27

4. TO CARRY OUT THE HEATING PROCESS OF FRESH AIR & FIND OUT

RELEVANT PARAMETERS ON AIR CONDITIONING TEST RIG AND TO

PLOT THE PROCESS ON PSYCHROMETRIC CHART

1. Objective:

To study the heating of air in air conditioning test rig and perform experiment to calculate the

change in relevant parameter of air during heating process.

2. Aim:


Plot the process on Psychrometric chart

Calculate the heat supplied during heating process.

3. Nomenclature:

4. Introduction:



























28
















5. Block Diagram:


6. Theory:

The heating of air, without any change in its specific humidity, is known as sensible heating.

Let air at temperature Td1 passes over a heating coil of temperature Td3 as shown in Fig. 5.2.

It may be noted that the temperature of air leaving the heating coil(Td2) will be less than Td3.

The process of sensible heating, on the psychometric chart, is shown by horizontal line 1-2

29

extending from left to right as shown in Fig. 5.2. The point 3 represents the surface

temperature of the heating coil.

The heat absorbed by the air during sensible heating may be obtained from the psychometric

chart by the enthalpy difference (h2-h1) as shown in figure. It may be noted that the specific

humidity during the sensible heating remains constant (i.e. W1 = W2). The dry bulb

temperature from td1 to td2 and relative humidity Φ1 to Φ2

Heat added,

Q = h2 - h1

= Cpa(td2-td1) + Wcps(td2-td1)

Sensible heating of the air is important when the air conditioner is used as the heat pump to

heat the air. In the heat pump the air is heated by passing it over the condenser coil or the

heating coil that carry the high temperature refrigerant. In some cases the heating of air is

also done to suit different industrial and comfort air-conditioning applications where large air

conditioning systems are used.

Fig. 4.2 Sensible Heating Process on Psychrometric chart

In general the sensible heating process is carried out by passing the air over the heating coil.

This coil may be heated by passing the refrigerant, the hot water, the steam or by electric

resistance heating coil. The hot water and steam are used for the industrial applications.

Like the sensible cooling, the sensible heating process is also represented by a straight

horizontal line on the psychrometric chart. The line starts from the initial DB temperature of

30

air and ends at the final temperature extending towards the right (see the figure). The sensible

heating line is also the constant DP temperature line.

7. Description:













guard of heater.



connection.



Starting Procedure:

1. Switch ‘ON’ the main power supply.

2. Switch ‘ON’ the air heater.

3. After 10 minutes note down the temperature of ambient air by rotating sling psychomotor

and also of conditioned air by putting sling psychomotor in front of air duct. Repeat the

experiment till the temperature of outlet of air become constant.

Closing Procedure:

1. Switch OFF the heater.

2. Switch OFF the main power supply.


10.1 Data:

Cos Φ = 0.7

a = 1.21 Kg/m3



31

Sr.No. t min Tdi (C) Twi (C) Tdo (C) Two (C) V I

10.3 Calculations:







For Sensible Heating Process X1 = X2

Heat added to the air = Change in enthalpy of air

= h2 – h1










13. Conclusion:

32

14. References:


Pvt. Ltd. pp 125-126.






34

5. TO CARRY OUT THE COOLING PROCESS OF FRESH AIR & FIND OUT

RELEVANT PARAMETERS ON AIR CONDITIONING TEST RIG AND TO

PLOT THE PROCESS ON PSYCHROMETRIC CHART

1. Objective:

To study the cooling of air in air conditioning test rig and perform experiment to calculate the

change in relevant parameter of air during cooling process.

2. Aim:



Calculate the heat rejected during cooling process.

3. Nomenclature:








compressor inlet

kJ/ kg Calculated


outlet

kJ/ kg Calculated


condenser

kJ/ kg Calculated

















35

4. Introduction:




























5. Block Diagram:





36


6. Theory:

Cooling of the air is one of the most common psychrometric processes in the air conditioning

systems. The basic function of the air-conditioners is to cool the air absorbed from the room

or the atmosphere, which is at higher temperatures. The sensible cooling of air is the process

in which only the sensible heat of the air is removed so as to reduce its temperature, and there

is no change in the moisture content (kg/kg of dry air) of the air. During sensible cooling

process the dry bulb (DB) temperature and wet bulb (WB) temperature of the air reduces,

while the latent heat of the air, and the dew point (DP) temperature of the air remains

constant. There is overall reduction in the enthalpy of the air.

In the ordinary window or the split air conditioner the cooling of air is carried out by passing

it over the evaporator coil, also called as the cooling coil. The room air or the atmospheric air

passes over this coil carrying the refrigerant at extremely low temperatures, and gets cooled

and passes to the space which is to be maintained at the comfort conditions.

In general the sensible cooling process is carried out by passing the air over the coil. In the

unitary air conditioners these coils are cooled by the refrigerant passing through them and are

called also called evaporator coils. In central air conditioners these coils are cooled by the

chilled water, which is chilled by its passage through the evaporator of the large air

conditioning system. In certain cases the coil is also cooled by the some gas passing inside it.

The sensible cooling process is represented by a straight horizontal line on the psychrometric

chart. The line starts from the initial DB temperature of the air and ends at the final DB

temperature of the air extending towards the left side from high temperature to the low

temperature (see the figure below). The sensible cooling line is also the constant DP

37

temperature line since the moisture content of the air remains constant. The initial and final

points on the psychrometric chart give all the properties of the air.

Fig. 5.2 Sensible Cooling Process on Psychrometric chart

7. Description:













guard of heater.



connection.


38


Starting Procedure:




11. After 10 minutes note down the reading of temperature sensor.


13. Note down the reading of temperature and pressure after every 10 minutes till the

temperature of outlet of air come constant.

Closing Procedure:

3. Switch off the compressor.

4. Switch off the mains power supply.


10.1 Data:

Cos Φ = 0.7

a = 1.21 Kg/m3



Sr.No. t

min

P1

Bar

P2

Bar

T1

(C)

T2

(C)

T3

(C)

T4

(C)

Tdi

(C)

Twi

(C)

Tdo

(C)

Two

(C)

V I

10.3 Calculations:


723.415)652.0()98.1011.0( 1111 TPTH

723.415)652.0()98.1011.0( 2222 TPTH

93.199228.1 33 TH

12

41..HH

HHPOC Th

43 HH

1000

CosIVCW

KJ/sec

To calculate the specific humidity X1 and enthalpy of air H1 at temperature Tdi & Twi.


H1 = (kJ/kg of dry air) [from psychrometric chart]

39

To calculate the specific humidity X2 and enthalpy of air H2 at temperature Tdo & Two


H2 = (kJ/kg of dry air) [from psychrometric chart]

For Sensible Cooling Process X1 = X2

Heat rejected from the air = Change in enthalpy of air

R.E. = h1 – h2










13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.






41

6. TO CARRY OUT THE HEATING AND HUMIDIFICATION PROCESS OF

FRESH AIR & FIND OUT RELEVANT PARAMETERS ON AIR

CONDITIONING TEST RIG AND TO PLOT THE PROCESS ON

PSYCHROMETRIC CHART

1. Objective:

To study the heating and humidification process of air in air conditioning test rig and perform

experiment to calculate the change in relevant parameter of air during process.

2. Aim:



Calculate the heat supplied during heating process

Calculate the amount of water vapour add during the process

3. Nomenclature:

4. Introduction:

























42


















5. Block Diagram:


6. Theory:

In heating and humidification psychrometric process of the air, the dry bulb temperature as

well as the humidity of the air increases. The heating and humidification process is carried

out by passing the air over spray of water, which is maintained at temperature higher than the

dry bulb temperature of air or by mixing air and the steam.

43

When the ordinary air is passed over the spray of water maintained at temperature higher than

the dry bulb temperature of the air, the moisture particles from the spray tend to get

evaporated and get absorbed in the air due to which the moisture content of the air increase.

At the same time, since the temperature of the moisture is greater than the dry bulb

temperature of the air, there is overall increase in its temperature.

During heating and humidification process the dry bulb, wet bulb, and dew point temperature

of the air increases along with its relative humidity. The heating and humidification process is

represented on the psychrometric chart by an angular line that starts from the given value of

the dry bulb temperature and extends upwards towards right (see the Fig. 7.2 below).

Fig. 6.2 Heating and Humidification Process on Psychrometric chart

7. Description:









44





guard of heater.



connection.



Starting Procedure:



6. Allow steam to pass through the pipe and slowly open the wet steam vent valve to release

wet steam from the pipe.

7. Close the wet steam vent valve.

8. Rotate psychrometer and note down the ambient temperature of air.

9. After 10 minutes note down the temperature of air by putting sling psychrometrer in front

of air duct.

10. Note down the reading of pressure gauges and temperature sensors.

11. Repeat the experiment till the temperature of outlet of air become constant

Closing Procedure:

3. Switch OFF the heater.

4. Stop steam supply by closing the steam valve.



10.1 Data:

Cos Φ = 0.7

a = 1.21 Kg/m3



Sr.No. t

(min)

Tdi (C) Twi (C) Tdo (C) Two (C) V I

45

10.3 Calculations:







Amount of water vapour added to air = 12 XXX

= (kg/kg of dry air)

Heat added to the air = Change in enthalpy of air

= h2 – h1










13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.



46




48

7. TO CARRY OUT THE COOLING AND HUMIDIFICATION PROCESS OF



PSYCHROMETRIC CHART

1. Objective:

To study the cooling and humidification process of air in air conditioning test rig and perform

experiment to calculate the change in relevant parameter of air during process.

2. Aim:



Calculate the heat rejected during process

Calculate the amount of water vapour add during the process

3. Nomenclature:








compressor inlet

kJ/ kg Calculated


outlet

kJ/ kg Calculated


condenser

kJ/ kg Calculated















49

4. Introduction:




























5. Block Diagram:







50


6. Theory:

Cooling and humidification process is one of the most commonly used air conditioning

application for the cooling purposes. In this process the moisture is added to the air by

passing it over the stream or spray of water which is at temperature lower than the dry bulb

temperature of the air. When the ordinary air passes over the stream of water, the particles of

water present within the stream tend to get evaporated by giving up the heat to the stream.

The evaporated water is absorbed by the air so its moisture content, thus the humidity

increases. At the same time, since the temperature of the absorbed moisture is less than the

DB bulb temperature of the air, there is reduction in the overall temperature of the air. Since

the heat is released in the stream or spray of water, its temperature increases.

One of the most popular applications of cooling and humidification is the evaporative cooler,

also called as the desert cooler. The evaporative cooler is the sort of big box inside which is a

small water tank, small water pump and the fan. The water from the tank is circulated by the

pump and is also sprayed inside the box. The fan blows strong currents of air over the water

sprays, thus cooling the air and humidifying it simultaneously. The evaporative cooler is

highly effective cooling devise having very low initial and running cost compared to the

unitary air conditioners. For cooling purposes, the cooling and humidification process can be

used only in dry and hot climates like desert areas, countries like India, China, Africa etc.

This cooling process cannot be used in hot and high humidity climates.

The cooling and humidification process is also used in various industries like textile, where

certain level of temperature and moisture content has to be maintained. In such cases large

quantity of water is sprayed, and large blowers are used to blow the air over the spray of

water.

51

During the cooling and humidification process the dry bulb of the air reduces, its wet bulb

and the dew point temperature increases, while its moisture content and thus the relative

humidity also increases. Also, the sensible heat of the air reduces, while the latent heat of the

air increases resulting in the overall increase in the enthalpy of the air.

Cooling and humidification process is represented by an angular line on the psychrometric

chart starting from the given value of the dry bulb temperature and the relative humidity and

extending upwards toward left.

Fig. 7.2 Cooling and Humidification Process on Psychrometric chart

7. Description:













guard of heater.

52



connection.



Starting Procedure:










of air duct.


21. Repeat the experiment till the temperature of outlet of air become constant.

Closing Procedure:

6. Switch OFF the compressor.




10.1 Data:

Cos Φ = 0.7

a = 1.21 Kg/m3



53

Sr.No. t

(min)

P1

Bar

P2

Bar

T1

(C)

T2

(C)

T3

(C)

T4

(C)

Tdi

(C)

Twi

(C)

Tdo

(C)

Two

(C)

V I

10.3 Calculations:


723.415)652.0()98.1011.0( 1111 TPTH

723.415)652.0()98.1011.0( 2222 TPTH

93.199228.1 33 TH

12

41..HH

HHPOC Th

43 HH

1000

CosIVCW

KJ/sec







Amount of water vapour added to air = 12 XXX



R.E. = ∆h










54

13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.






56

8. TO CARRY OUT THE COOLING AND DEHUMIDIFICATION PROCESS OF



PSYCHROMETRIC CHART

1. Objective:

To study the cooling and dehumidification process of air in air conditioning test rig and

perform experiment to calculate the change in relevant parameter of air during process.

2. Aim:



Calculate the heat rejected during process

Calculate the amount of water vapour removed during the process

3. Nomenclature:








compressor inlet

kJ/ kg Calculated


outlet

kJ/ kg Calculated


condenser

kJ/ kg Calculated















57

4. Introduction:




























5. Block Diagram:







58


6. Theory:

The process in which the air is cooled sensibly and at the same time the moisture is removed

from it is called as cooling and dehumidification process. Cooling and dehumidification

process is obtained when the air at the given dry bulb and dew point (DP) temperature is

cooled below the dew point temperature.

Let us understand the cooling and dehumidification process in more details. When the air

comes in contact with the cooling coil that is maintained at the temperature below its dew

point temperature, its DB temperature starts reducing. The process of cooling continues and

at some point it reaches the value of dew point temperature of the air. At this point the water

vapor within the air starts getting converted into the dew particles due to which the dew is

formed on the surface of the cooling and the moisture content of the air reduces thereby

reducing its humidity level. Thus when the air is cooled below its dew point temperature,

there is cooling as well as dehumidification of air.

The cooling and dehumidification process is most widely used air conditioning application. It

is used in all types of window, split, packaged and central air conditioning systems for

producing the comfort conditions inside the space to be cooled. In the window and split air

conditioners the evaporator coil or cooling coil is maintained at temperature lower than the

dew point temperature of the room air or the atmospheric air by the cool refrigerant passing

through it. When the room air passes over this coil its DB temperature reduces and at the

same time moisture is also removed since the air is cooled below its DP temperature. The

dew formed on the cooling coil is removed out by small tubing. In the central air conditioning

systems the cooling coil is cooled by the refrigerant or the chilled water. When the room air

passes over this coil, it gets cooled and dehumidified.

59

In the general the cooling and dehumidification process is obtained by passing the air over

coil through which the cool refrigerant, chilled water or cooled gas is passed.

During the cooling and dehumidification process the dry bulb, wet bulb and the dew point

temperature of air reduces. Similarly, the sensible heat and the latent heat of the air also

reduce leading to overall reduction in the enthalpy of the air. The cooling and

dehumidification process is represented by a straight angular line on the psychrometric chart.

The line starts from the given value of the DB temperature and extends downwards towards

left.

Fig. 8.2 Cooling and Dehumidification Process on Psychrometric chart

7. Description:












60


guard of heater.



connection.



Starting Procedure:

22. Close valves below the pressure gauges

23. Open the funnel and air vent valve of steam generator.

24. Fill water in the steam generator upto 3/4th

of its capacity by observing the level of water

in level indicator.


26. Switch ‘ON’ the heater of steam generator and set the temperature of steam with the help

of DTC (100-120 oC). And wait until steam temperature reaches to desired value.










of air duct.


36. Repeat the experiment till the temperature of outlet of air become constant.

Closing Procedure:

9. Switch OFF the compressor.


11. Switch OFF the air heater.



10.1 Data:

Cos Φ = 0.7

a = 1.21 Kg/m3


61


Sr.No. t

(min)

P1

Bar

P2

Bar

T1

(C)

T2

(C)

T3

(C)

T4

(C)

Tdi

(C)

Twi

(C)

Tdo

(C)

Two

(C)

V I

10.3 Calculations:


723.415)652.0()98.1011.0( 1111 TPTH

723.415)652.0()98.1011.0( 2222 TPTH

93.199228.1 33 TH

12

41..HH

HHPOC Th

43 HH

1000

CosIVCW

KJ/sec







Amount of water vapour removed from air = 1 2X X X



= h1 - h2










62

13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.






refrigeration and air conditioning (2161908) · a laboratory manual for refrigeration and air...

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