darshan institute of enginnering & technology · 2019-11-19 · cop of vcr system refrigeration...

DARSHAN INSTITUTE OF ENGINNERING &

TECHNOLOGY

Department of Mechanical Engineering

Semester – VI

Refrigeration & Air Conditioning (2161908)

List of Experiments

Sr. No.

Title Starting

Date Completion

Date Sign Grade

1

To study and calculate capacity &

COP of Vapour Compression

Refrigeration (VCR) system.

2

To study and calculate capacity and

COP of Vapour Absorption

Refrigeration (VAR) 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 parameters

of air and also plot the process on

psychrometric chart.

5

To carry out Cooling process of fresh

air and find out relevant parameters

of air and also plot the process on

psychrometric chart.

6

To carry out Heating and

humidification process and find out

relevant parameters and also plot the

process on psychrometric chart.

7

To carry out Cooling and

humidification process and find out

relevant parameters and plot the

process on psychrometric chart.

8

To carry out Cooling and

dehumidification process and find

out relevant parameters and also plot

the process on psychrometric chart.

COP of VCR System

Refrigeration and Air Conditioning (2161908) Department of Mechanical Engineering

Darshan Institute of Engineering and Technology, Rajkot

1- 1

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 (R 134a).

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 refrigerant at compressor inlet kJ/kg Calculated

H2 Enthalpy of refrigerant at compressor outlet kJ/kg Calculated

H3 Enthalpy of refrigerant at condenser outlet kJ/kg Calculated

H4 Enthalpy of refrigerant at evaporator inlet 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 min Measured

V Voltmeter reading Volts Measured

COP of VCR System



1-2

Vwe Volume of water in evaporator for batch cooling Ltrs Measured

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

w Density of water kg/m3 Given

4. Introduction:

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:

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

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

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

shown in Fig. 1.1.

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

vapour condition.

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. 1.1 Pressure- Enthalpy Diagram

COP of VCR System



1- 3

5.2 Standard Vapour Compressor Refrigeration System:

Standard vapour compressor refrigeration system consists of following basic

components as shown in Fig. 1.2.

Fig. 1.2 Schematic diagram of Vapour Compression Refrigeration System

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 refrigerant 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.

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.

COP of VCR System



1-4

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

of net refrigeration (output) to the 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, ampere meter, energy meter, rotameter, and 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 provided 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.

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).

COP of VCR System



1- 5

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 provided 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/kgoC

Heater Capacity W = 0.5 KW

Evaporator Tank capacity = 30 Ltrs

9.1.b Observation Table:

T6i = ______oC Water filled in Evaporator tank = ____ Ltrs

For Batch Operation

Sr.

No

t

min

P1

kg/cm2

P2

kg/cm2

T1

(oC)

T2

(oC)

T3

(oC)

T4

(oC)

T5

(oC)

T6

(oC) Vwe

V

(Volts)

I

(Amp)

NA

NA

NA

COP of VCR System



1-6

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:

60 1000we w

b

Vm

t

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)

NA

NA

NA

(B) For Continuous Operation:

1000 3600wr w

c

Vm

(kg/sec)

)( 65 TTCmRE pccAct (kJ/sec)

1000

CosIVCWAct

(kJ/sec)

Act

cAct

cActCW

REPOC .)..(

Th

Act

clPOC

POCPOC c

..

...)..( Re

COP of VCR System



1- 7

For Batch Operation

COP of VCR System



1-8

For Continous Operation

COP of VCR System



1- 9

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:

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

Ltd. pp 102-105,118-125

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.

COP of VAR System



2- 1

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

solution in a suitable absorbent, forming a strong 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 Fig. 2.1 with different

shadings and the index of these shadings also indicated in diagram. Vertical boiler or

generator 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

COP of VAR System



2-2

the water may evaporate on 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 (Three Fluid)

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 by absorbing 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 weak ammonia

COP of VAR System



2- 3

solution 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.

Counter flow type liquid heat exchanger is placed in between absorber and the

generator. Thus weak liquid gets cooled and strong liquid solution gets heated, thus is

economized and better thermal efficiency obtained. The strong liquid solution from

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

way to absorber is cooled. This cooling of weak liquid solution 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 strong ammonia solution is heated in the boiler, bubbles of ammonia as

raises.

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 and

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.

COP of VAR System



2-4

8. Observation & Calculation:

8.1 Observation Table: SR. 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:

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

2. Unnecessary handling of equipment should be avoided.

3. Never open the refrigerator during the experiment.


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

11. Conclusion:

12. References:

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

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

COP of Air Conditioning System



3- 1

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 (R 22).

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 refrigerant at compressor inlet kJ/ kg Calculated

H2 Enthalpy of refrigerant at compressor outlet kJ/ kg Calculated

H3 Enthalpy of refrigerant at condenser outlet kJ/ kg Calculated

H4 Enthalpy of refrigerant at evaporator inlet 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

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




3-2

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

V Voltmeter Reading Volts Measured

I Ampere meter reading Amp. Measured




3- 3

5. Block Diagram:

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.

6.1 Vapour Compression Cycle The refrigerant starts at some initial state, passes through a series of processes in a

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

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

shown in Fig. 3.2.

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

heated vapour condition.

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.




3-4

Fig. 3.2 Pressure- Enthalpy Diagram

6.2 Standard Vapour Compressor Cycle

Standard vapour compressor refrigeration system consists of following basic

components as shown in Fig. 3.3.

Fig. 3.2 Schematic diagram of Vapour Compression Refrigeration System




3- 5

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 refrigerant 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.

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

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




3-6


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.

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

kg/cm2

P2

kg/cm2

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




3- 7

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)

1 __________h (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 = Refrigerating effect

R.E. = h1 – h2

= (kJ/kg of dry air)




3-8




3- 9


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.

Sensible Heating



4- 1

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 parameters of air during heating process.

2. Aim:


Plot the process on Psychrometric chart.

Calculate the heat supplied during heating process.

3. Nomenclature:

4. Introduction:








following jobs.


















Sensible Heating



4-2
















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


3. Control and measurement panel.

5. Block Diagram:


Sensible Heating



4- 3

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. 4.2. 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 extending from left to right as shown in Fig. 4.2.

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

Sensible Heating



4-4

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 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:



















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.

Sensible Heating



4- 5


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

10.3 Calculations:







For Sensible Heating Process X1 = X2

Heat added to the air = Change in enthalpy of air

= h2 – h1


Sensible Heating



4-6

Sensible Heating



4- 7




volts.




supply.



13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.



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

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


Sensible Cooling



5- 1

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:






CW Compressor Work KJ/Kg Calculated






















Sensible Cooling



5-2

4. Introduction:








following jobs.
























Sensible Cooling



5- 3

5. Block Diagram:


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.

Sensible Cooling



5-4

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 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:












Sensible Cooling



5- 5








Starting Procedure:




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


6. 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.

2. Switch off the mains power supply.


10.1 Data:

Cos Φ = 0.7

a = 1.21 kg/m3



Sr.

No.

t

min

P1

kg/cm2

P2

kg/cm2

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

Sensible Cooling



5-6

12

41..HH

HHPOC Th

43 HH

1000

CosIVCW

KJ/sec







For Sensible Cooling Process X1 = X2


R.E. = h1 – h2


Sensible Cooling



5- 7

Sensible Cooling



5-8




volts.




supply.



13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.



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



Heating and Humidification

Refrigeration and Air Conditioning (2161908)



6- 1

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:








following jobs.


















6-2






















5. Block Diagram:






6- 3

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.

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. 6.2 below).

Fig. 6.2 Heating and Humidification Process on Psychrometric chart




6-4

7. Description:



















Starting Procedure:



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

release wet steam from the pipe.

4. Close the wet steam vent valve.

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

6. After 10 minutes note down the temperature of air by putting sling psychrometrer

in front of air duct.

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

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

Closing Procedure:

1. Switch OFF the heater.

2. Stop steam supply by closing the steam valve.



10.1 Data:

Cos Φ = 0.7

a = 1.21 kg/m3





6- 5



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

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





6-6





6- 7




volts.




supply.



13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.






Cooling and Humidification



7- 1

7. TO CARRY OUT THE COOLING 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 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:




























7-2

4. Introduction:








following jobs.






























7- 3

5. Block Diagram:


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.




7-4

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.

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:










7- 5













Starting Procedure:












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

Closing Procedure:

1. Switch OFF the compressor.




10.1 Data:

Cos Φ = 0.7

a = 1.21 kg/m3




7-6



Sr.

No.

t

(min)

P1

kg/cm2

P2

kg/cm2

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





7- 7




7-8




volts.




supply.



13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.






Cooling and Dehumidification



8- 1

8. TO CARRY OUT THE COOLING AND DEHUMIDIFICATION

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 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:




























8-2

4. Introduction:


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.






























8- 3

5. Block Diagram:


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




8-4

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.

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:










8- 5













Starting Procedure:

1. Close valves below the pressure gauges

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

3. Fill water in the steam generator upto 3/4th of its capacity by observing the level of

water in level indicator.


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

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

value.












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

Closing Procedure:

1. Switch OFF the compressor.


3. Switch OFF the air heater.





8-6


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







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


Heat rejected from the air = Change in enthalpy of air

= h1 - h2





8- 7




8-8




volts.




supply.



13. Conclusion:

14. References:


Pvt. Ltd. pp 125-126.






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