Heat Rejection Factor

[freddyng]

Hi All

Can anyone tell me how Heat Rejection Factors are obtained for 100% suction-cooled hermetically sealed compressor? Some manufacturers do not provide such data in their catalogue anymore.

Cheers
Freddy

[BESC5240]

Hi,
This depends on the construction of the compressor and on the application. A good estimation will be about 5% of the absorbed power.

[Dan]

My recollection is that it is about 3% less than absorbed power (compressor wattage). This is the assumed reduction through the compressor body and discharge piping to the ambient. A safe number, methinks.

[Dan]

I suppose I didn't answer the original question all that well. If you look at the compressor wattage versus capacity you have a ratio which changes significantly between the major suction pressures represented by Low Temperature, Medium Temperature, and High Temperature applications. The heat rejection factor is a way of representing that ratio that you can apply to the capacity of the compressor. It's really just an approximation of the input/output ratio.

The wattage input represents all the heat that you must reject with suction cooled semi-hermetic compressors. My ealier (3%) comment referred to fudging this number down for heat loss before the condenser.

[freddyng]

Thank you for the valuable information.

By the way, Dan. Is there an industry standard to classify the different ranges of evaporating temperature?
I am refering to Low Temp, Medium Temp, and High Temp. It seems that different compressor manufacturer uses a slightly different ranges of temperature in their catalogue.

Cheers
Freddy

[Dan]

Regarding the difference between the operating temperature range classifications, it is rather arbitrary, since many semi-hermetic compressors can operate across rather broad temperature ranges. For convenience, I think of the ranges as such:

• Ultra low temperature below -40 deg F
• Low temperature -40 to -10 deg F
• Medium temperature - 5 to 25 deg F
• High temperature/air conditioning 30 and above

I am not aware of an industry standard, nor do I see the need for one.

[wambat]

Freddy, This may be of some help for you
http://66.28.63.222/documents/Conden...550rpm_630.pdf

[freddyng]

Thanks Pal

Nice piece of information.

Cheers
Freddy

[jaimebuiles2]

It depends from the evaporator and condensing temperature. You can find tables like that for open compressors, but it's for hermetic compressors. I hope it can help you.

SUCTION COOLED HERMETIC COMPRESSORS

EVAPORATOR TEMP (F)

CONDENSING TEMPERATURE (F)

90

100

110

120

130

140

-40

-30

-20

-10

1.66

1.57

1.49

1.42

1.73

1.62

1.53

1.46

1.80

1.68

1.58

1.50

2.00

1.80

1.65

1.57

*

*

*

1.64

*

*

*

*

0

5

10

1.36

1.53

1.31

1.40

1.37

1.34

1.44

1.41

1.38

1.50

1.46

1.43

1.56

1.52

1.49

1.62

1.59

1.55

15

20

25

1.28

1.26

1.24

1.32

1.29

1.27

1.35

1.33

1.31

1.40

1.37

1.35

1.46

1.43

1.40

1.52

1.49

1.45

30

40

50

1.22

1.18

1.14

1.25

1.21

1.47

1.28

1.24

1.20

1.32

1.27

1.23

1.37

1.31

1.26

1.42

1.35

1.29

*Outside of normal limits for single stage compressor application.

[jaimebuiles2]

It depends from the evaporator and condensing temperature. You can find tables like that for open compressors, but it's for hermetic compressors. I hope it can help you.

[Toosh]

It depends from the evaporator and condensing temperature. You can find tables like that for open compressors, but it's for hermetic compressors. I hope it can help you.

Geez man this post is over 5 years old

[D.D.KORANNE]

I usually take it as heat equivalent ( in kw ) of evaporator capacity + motor kw as the heat rejection capacity of condenser . Besides, i keep the allowance for max sst expected after fresh start up .