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02-10-2009, 05:42 AM #1
Evaporating and Condensing Temperatures
Hello everyone. I am a design engineer for ground source heat pumps and a greenie in refrigeration. I am curious what the design evaporating and condensing temperatures would be for the following ground loop heat pump system (water to refrig and then refrig to air).
The refrigerant is R410A, the unit uses the Copeland compressor ZPS51K4EPFV. This would be sized for 64,000 BTU output at 70 deg ground loop entering water and 80 deg house entering air temperature. According to my figures, and using the information supplied by ClimateMaster, Series: Tranquility 27 (TT) Model: 064, I get the following evap and condensing temperatures:
Evap temp: 50.5 (144 psi)
Cond temp: 106 (347 psi)
at 70 EWT and 80 EAT
My question is if 50 sounds reasonable for an evaporation temperature...?
It is a high efficiency unit, probably 18 SEER?? (although I don't know if the SEER rating directly applies to ground source heat pumps). The airflow is 1825 CFM.
Next, what is the normal temperature difference between the Leaving Air Temperature (cold air going to the house) and the refrigerant saturation temperature in the evaporator? (for a ground source heat pump?)
At low EAT conditions like 65 EAT & 41.5 Leaving Air Temp, I get a negative TD of around 4 deg. That would be 41.5 (LAT) - 45.5 (Sat Evap Temp) = -4 TD. Is this possible?
Meaning my LAT is colder than my saturated evaporation temperature...?
Thanks in advance for the help!!
And thanks all the veterans of this post ... I have read through a number of items here and am quite impressed with the quality of this forum and the answers given and have found the topics covered here very helpful. Thanks!
Aaron
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