Refrigeration Calculations - Sporlan Online

27
A collection of short
pointed topical papers.
May 2006
Whether it’s Air Conditioning or Refrigeration
Refrigeration
Calculations
by: Garth Denison
Senior Application Engineer
The Sporlan Division of Parker Hannifin assumes no obligation or liability for any advice furnished or for any
results obtained with respect to this information. All such advice is given and accepted at users risk. This disclosure
of information herein is not a license to operate under, or a recommendation to infringe any patent of
Sporlan Division of Parker Hannifin or others.
® Registered trademark of Sporlan Division of Parker Hannifin, Washington, MO 63090 USA
© Copyright 2003 by Sporlan Division of Parker Hannifin, Washington, MO 63090 USA
This document may be copied and distributed for educational purposes only.
®
Cold W.A.R. Issue 027

Page 2 - Cold W.A.R. Issue 27
1. Net Refrigeration
Effect, Btu/lb
2. Net Refrigerating
Effect, Btu/lb
3. Net refrigerating
Effect, Btu/lb
4. Refrigerant Circulated,
lb/min
5. Compressor
Displacement, cu ft/min
6. Compressor
Displacement, cu ft/min
7. Heat of Compression,
Btu/lb
8. Heat of Compression
Btu/lb
9. Compression Work,
Btu/min
10. Compression
Horsepower
Refrigeration Calculations
Pressure-enthalpy charts are tools to use in better understanding refrigeration cycles, for judging
whether the operation is normal, and for estimating the effect of change in operation. Learning
how to read the charts and to do the calculations involved will pay rich dividends in all phases of
refrigeration work.
Examples of various refrigeration calculations are shown below.
Heat content of
vapor leaving
evaporator, Btu/lb
Latent heat of
vaporization,
Btu/lb
Capacity, Btu/min
Refrigerant circulated, lb/min
Load or capacity, Btu/min
Net refrigeration effect, Btu/lb
Refrigerant
circulated, lb/min
Capacity
Btu/min
X
Heat content of
Vapor leaving
Compressor, Btu/lb
X
Refrigerant circulated, lb/min
Compression work, Btu/min
Heat content of
liquid entering
evaporator, Btu/lb
Conversion factor, 42.41 Btu/min - hp
Change in heat content
of liquid from condensing
to evaporator temperature, Btu/lb
Volume of gas
entering compressor, cu ft/lb
Volume of gas
entering compressor, cu ft/lb
Net refrigerating effect, Btu/lb
Heat of compression,
Btu/lb
X
Heat content of
Vapor entering
Compressor, Btu/lb
(42.41 Btu/min - hp) (compression horsepower)
Refrigerant circulated,
lb/min
or
Btu/hr
2546 Btu/hr - hp

11. Compression
Horsepower
12. Compression
Horsepower
13. Compression
Horsepower per Ton
14. Power, watts
15. Coefficient of
Performance
16. Capacity,
Btu/min
17. Capacity,
Btu/min
18. Capacity,
Btu/min
COP =
Example of # 15
Net refrigeration effect
Heat of compression
NRE is
Refrigeration Calculations
108.8
- 45.1
63.7
H of C is
= 63.7
10.1
SCT is Saturated Condensing Temperature
SST is Saturated Suction Temperature
Cold W.A.R. Issue 27 - Page 3
Heat of compression,Btu/lb X Capacity, Btu/min
(42.41 Btu/min - hp) X Net refrigeration effect, Btu/lb
Capacity, Btu/min
(42.41 Btu/min - hp) X Coefficient of performance
4.716
Coefficient of performance
Compression horsepower per Ton X 745.7 w - ton/hp
Net refrigeration effect, Btu/lb
Heat of compression, Btu/lb
Refrigerant circulated, lb/min X Net refrigerating effect, Btu/lb
Compressor displacement, cu ft/min X Net refrigerating effect, Btu/lb
Volume of gas entering compressor, cu ft/lb
Compression
horsepower
118.9
-108.8
10.1
= 6.61
X
42.41
Btu/min - hp
X
Heat of compression, Btu/lb
139.0
49.8
Pressure
( p sia)
100 F
40 F
Enthalpy
(Btu/lb)
200
42.41
= 4.716
Net refrigerating
Effect, Btu/lb
Reference: Fluorocarbon Refrigerants Handbook
45.1
SST
SCT
108.8
R-134a
118.9