[TRNSYS-users] Type 927 Heat Pump: Carnot COP - evaporator and condenser temperatures

Flynn Ciaran ciaran.flynn at aalto.fi
Tue Mar 26 08:46:39 PDT 2013

Hello everybody,

I am trying to calculate the Carnot COP (heating mode) of the heat pump used in type 927 (the default pump, which is the TRANE WPWD 024), however I am having trouble determining the evaporator and condenser temperatures.

From online catalogues, I found that the refrigerant used is R22, but I didn’t find anything else regarding the refrigerant circuit (only the water circuits).
So I had to make some assumptions in order to get some results:

-          saturated vapour at the evaporator outlet

-          saturated liquid at the condenser outlet

-          isenthalpic expansion at the throttle

The problem then is that I have not been able to find the compressor efficiency (function of COP?) nor the ΔT between the refrigerant and the water streams in both evaporator and condenser (also function of COP?)…

I have tried making some realistic assumptions, but unfortunately results were inconsistent (I assumed a linear relationship between compressor efficiency and COP (60% to 80% for a COP of 3.8 to 5), and linear relationship between the ΔT and COP (14C to 28C in the range of 3.8 to 5)). I also assumed that the ΔT is the same between the refrigerant and the water in the evaporator as that of the refrigerant and the water in the condenser.

Does anyone know if it is even possible to determine the Carnot COP by making such assumptions? Or does anyone have any extra data regarding this heat pump (or any heat pump for that matter) ?

Any suggestions/help would be great,

Thanks again,

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