10

10

-

-

3 

3 

The Ideal 

The Ideal 

Vapor

Vapor

-

-

Compression 

Compression 

Refrigeration Cycle

Refrigeration Cycle

presented by: 

presented by: 

Linda Manning

Linda Manning

02/22/01

02/22/01

Topics of Discussion

Topics of Discussion

Household Refrigerators

Processes of Ideal Vapor-
Compression Refrigeration Cycle

Steady Flow Analysis

Carnot Cycle vs. Ideal Vapor-
Compression Refrigeration Cycle

Practice Problem

Household Refrigerator

Household Refrigerator

Encarta Deluxe 2001

Four Processes

Four Processes

1-2 Isentropic compression in a 

compressor

2-3 Constant pressure heat rejection in 

a condenser

3-4 Throttling in an expansion device

4-1 Constant pressure heat absorption 

in an evaporator

Ideal Vapor

Ideal Vapor

-

-

Compression 

Compression 

Refrigeration Cycle

Refrigeration Cycle

Schematic

Schematic

1-Enters Compressor 

Sat. Vapor

2-Enters Condenser

Super. Vapor

3-Throttled 

Sat. Liquid

4-Enters Evaporator

Sat. Mixture

T

T

-

-

s Diagram

s Diagram

Area under process 
curve = heat transfer 

Area under 4-1 = 

heat absorbed

Area under 2-3 = heat 
rejected

Steady Flow Process

Steady Flow Process

PE and KE small 
relative to work 
and heat transfer.

q

L

=h

1

-h

4

w

net

,in=h

2

-h

1

q

H

=h

2

-h

3

COP

R

=q

L

/w

net,in

COP

HP

=q

H

/w

net,in

Carnot

Carnot

Cycle vs. Ideal Vapor

Cycle vs. Ideal Vapor

-

-

Compression Refrigeration Cycle

Compression Refrigeration Cycle

Two phase after evaporation

Turbine, not throttling device

Internally reversible

Practice Problem

Practice Problem

10-12

Given: Refrigerant-134a

m

dot

= 0.05 kg/s

P

1

=120 kPa

P

2

=0.7 Mpa

Find: (a)  rate of heat removal from refrigerated 

space  & power input into compressor

(b)  rate of heat rejection to the environment
(c)  coefficient of performance