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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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
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.
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.
Freddy, This may be of some help for you
http://66.28.63.222/documents/Conden...550rpm_630.pdf
Thanks Pal
Nice piece of information.
Cheers
Freddy
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.
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.
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 .