View Full Version : Heat Rejection Factor
freddyng
20-10-2005, 03:43 AM
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
20-10-2005, 07:58 AM
Hi,
This depends on the construction of the compressor and on the application. A good estimation will be about 5% of the absorbed power.
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.
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
24-10-2005, 08:08 AM
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
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
25-10-2005, 11:56 PM
Freddy, This may be of some help for you
http://66.28.63.222/documents/Condenser_WCE_550rpm_630.pdf
freddyng
26-10-2005, 06:19 AM
Thanks Pal
Nice piece of information.
Cheers
Freddy
jaimebuiles2
10-03-2010, 04:38 AM
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
10-03-2010, 04:40 AM
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
10-03-2010, 07:43 AM
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 :confused::confused:
D.D.KORANNE
10-03-2010, 11:08 AM
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 .
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