(C)DR.A.M.SURENDRA KUMAR 1

(C)DR.A.M.SURENDRA KUMAR 2

VAPOUR COMPRESSION REFRIGERATION SYSTEM

(C)DR.A.M.SURENDRA KUMAR 3

(C)DR.A.M.SURENDRA KUMAR 5

(C)DR.A.M.SURENDRA KUMAR6

COMPONENT PROCESS FIRST LAW RESULT

1 Compressor s = Const.

2 Condenser P = Const

3 Expansion Valve s > 0

4 Evaporator P = Const

( )W m h hin 2 1

( )Q m h hH 2 3Wnet 0

h h4 3

( )Q m h hL 1 4

RESULTS OF FIRST AND SECOND LAW ANALYSIS

FOR STEADY-FLOW

COPQ

W

h h

h h

COPQ

W

h h

h h

RL

net in

HPH

net in

,

,

1 4

2 1

2 3

2 1

(C)DR.A.M.SURENDRA KUMAR 7

(C)DR.A.M.SURENDRA KUMAR 8

P-H CHART

MERITS & DEMERITS OF VAPOUR SYSTEM OVER

AIR REFRIGERATION SYSTEM

• MERITS:

1. C.O.P. is quite high as the working of the cycle is very near to

that of reversed Carnot cycle.

2. When used on ground level the running cost of vapour

compression refrigeration system is only 1/5 of air

refrigeration system.

3. For the same refrigeration effect the size of the evaporator is

smaller.

4. The required temperature of the evaporator can be achieved

simply by adjusting the throttle valve of the same unit.

• DEMERITS

• 1. Initial cost is high.

• 2. the major disadvantages are

• a) Inflammability

• b) Leakage of vapours

• c) Toxity.

(C)DR.A.M.SURENDRA KUMAR 11

VAPOUR COMPRESSION REFRIGERATION

SYSTEM ON T-S.DIAGRAM

EFFECT OF SUCTION & DELIVERY PRESSURE

EFFECT OF SUPERHEATING & SUBCOOLING OF LIQUID

LIQUID- VAPOUR HEAT

EXCHANGER

(C)DR.A.M.SURENDRA KUMAR 17

EFFECT OF CONDENSING & EVAPORATING TEMPERATURE ON C.OP & REFRIGERATING EFFECT

(C)DR.A.M.SURENDRA KUMAR18

EFFECT OF CONDENSER WATER TEMPERATURE ON POWER

PULL –DOWN CHARACTRISTCS

• PURPOSE OF THE TEST – COMPARE THE VALUES FOR DIFFERENT

REFRIGERATORS FOR DIFFERENT REFRIGERENTS

• TESTING OF REFRIGERATORS ACCORDING TO ISI SPECIFICATIONS

• ENVIORNMENT TEMPERATURE – MAINTAINED AT 430C.

• NO-LOAD TEST

• ADJUST THERMOSTAT –CABNET TEMP. 70C.

• PURPOSE:

• FIND PULL –DOWN PERIOD

• NO LOAD POWER CONSUMPTION

• % RUNNING TIME

• PULL –DOWN PERIOD : TIME REQUIRED TO REACH THE SPECIFIED TEMP.

INSIDE THE CABNET AFTER SWITCHING ON THE UNIT.

Ice making time test

(C)DR.A.M.SURENDRA KUMAR 20

• For this test:

• Stable operating conditions after Pull-down test

• Quantity of 0.5 kg of water at 30 10C in std tray – kept in the freezer

• Time for each “ON” and “OFF” is noted.

• After specified time of 3 hrs., ice tray is examined for the formation of ice.

• Running time of the unit during 3 hrs of operation is obtained from DAS

• DAS –to monitor ÖN-OFF cycle.

• This running time of the unit is the ice making time.

• For Freon -12 refrigerator:

• pull-down period – 90 min for 160L capacity

• ice making time – 125 min.