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Thread: Heat Rejection Factor
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20-10-2005, 03:43 AM #1
Heat Rejection Factor
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
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20-10-2005, 07:58 AM #2
Re: Heat Rejection Factor
Hi,
This depends on the construction of the compressor and on the application. A good estimation will be about 5% of the absorbed power.
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21-10-2005, 02:31 AM #3
Re: Heat Rejection Factor
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.
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21-10-2005, 02:39 AM #4
Re: Heat Rejection Factor
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.
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24-10-2005, 08:08 AM #5
Re: Heat Rejection Factor
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
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25-10-2005, 01:06 AM #6
Re: Heat Rejection Factor
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.
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25-10-2005, 11:56 PM #7
Re: Heat Rejection Factor
Freddy, This may be of some help for you
http://66.28.63.222/documents/Conden...550rpm_630.pdf
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26-10-2005, 06:19 AM #8
Re: Heat Rejection Factor
Thanks Pal
Nice piece of information.
Cheers
Freddy
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10-03-2010, 04:38 AM #9
Heat Rejection Factor
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 COMPRESSORSEVAPORATOR TEMP (F)CONDENSING TEMPERATURE (F)90100110120130140-40-30-20-101.661.571.491.421.731.621.531.461.801.681.581.502.001.801.651.57***1.64****05101.361.531.311.401.371.341.441.411.381.501.461.431.561.521.491.621.591.551520251.281.261.241.321.291.271.351.331.311.401.371.351.461.431.401.521.491.453040501.221.181.141.251.211.471.281.241.201.321.271.231.371.311.261.421.351.29
*Outside of normal limits for single stage compressor application.
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10-03-2010, 04:40 AM #10
Re: Heat Rejection Factor
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.
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10-03-2010, 07:43 AM #11
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10-03-2010, 11:08 AM #12
Re: Heat Rejection Factor
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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