This document defines refrigeration and discusses air refrigeration cycles. It explains that refrigeration is the process of removing heat from a substance to lower its temperature below its surroundings. Air was historically used as a refrigerant since it is freely available, but has low heat carrying capacity and requires high power. The document also defines the unit of refrigeration as the melting of one tonne of ice at 0°C in 24 hours. Finally, it compares heat engines, heat pumps, and refrigerators, defining coefficient of performance as the ratio of heat removed or supplied to work input.

2. DEFINITION OF REFRIGERATION
AIR REFRIGERATION
UNITS OF REFRIGERATION
COEFFICIENT OF PERFORMANCE OF A
REFRIGERATOR (COP)
DIFFERENCE B/W HEAT ENGINE, HEAT PUMP &
REFRIGEARTION

3. It may be defined as the process of removing heat from a substance
under cntrolled conditions.
it also includes the process of reducing and maintaining the temperature
of a bodybelow the general temperatureof its surroundings.
The refrigeration means a continued extraction of heat from a
bodywhose temperture is already below the temperature of its
surrounding.

4.  In an air refrigeration cycle, the air is used as a refrigerant.
 In olden days, air was widely used in commercial applications because
of its availability at free of cost.
 since does not change its phase ,remain gaseous through-out the
cycle, therefore heat carrying capacity per kg of air is very small as
compare to others.
 Low COP & High power requirements. (practically obsolete)
 The basic components of this cycle:-1.Compressor, 2. Heat exchanger
3. Expander and 4.Refrigerator.

5. The practically it is termed as “Tonne of refrigeration” (TR).
A tonne of refrigeration is defined as the amount of refrigeration
effect produced by the uniform melting of one tonne (1000kg) of
ice from and at 0℃ in 24 hours.
latent Heat of Ice is 335KJ/Kg.
1TR=1000x335 KJ in 24hours
=(1000x335)/(24x60) KJ/min
In actual practice , TR is taken as equivalent to 210KJ/min or 3.5
KW.
1000 kg ICE
at 0℃
warm air cool air
24 hours

6. It is the ratio of heat extracted in the refrigerator to the work done on
the refrigerant.
or
It is the ratio of desire effect to the work input of any Machine.
mathematically,
Where, Q=The amount of refrigeration produced or its capcity.
W=Amount of Workdone.
W
Q
POC ...

7. HEAT ENGINE
T2
T1
HE
Q2
Q1
T2
T1
RE
T2
T1
HP
REFRIGERATOR HEAT PUMP
WORK OUTPUT WORK INPUT WORK INPUT
12
1
...
TT
T
poc


12
2
...
TT
T
poc


)2(
)(
)(
QHeat
Wwork
efficiency 