Using a heat pump for a humid climate like sydney, the air temperature should be lowered below it's dew point , then it should be increased into desired comfort temperature. what is the typical COP of such systems? ( not COP of heat pump alone, I mean the COP of total system including the heater).
There are multiple ways to do this and of course multiple answers to your question. You could use a heat pump that uses waste heat to reheat the air, or use electric resistance to heat the air. Or you could use a desiccant system to remove additional moisture or add heat pipes to the coil to change the SHR. So to answer your question it would take specific information on your application. If a heat pump is used to condition the air to a thermostat set point and that heat pump operates at a 3-4 COP, then using over-cooling to dehumidify the air will lower the COP to 2-3 if electric reheat is used (i.e., you'll probably take a 25% - 30% hit on efficiency). If waste heat is used then the COP would be somewhere in between these values (2.5 - 3.5). These are simply rough guesses at this point without more information.
To do the design calculation you would use COP = ( kWcoolingcapacity - kWreheatcapacity ) / ( kWcoolingpower + kWreheatpower ) to ballpark your efficiency.
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