Quote:
Originally Posted by stevehull
Jeff,
I have been thinking of doing this with my open loop GT heat pumps (precooling return air with water) for summer AC
My well water temp is about 60F and I can get a real cheap evaporator (that doesn't leak) to put before existing GT heat pump air coil.
When the unit is on, it uses ~ 5 gallons per minute (~ 40 L/min). Easy to plumb the water exiting this precooler to then go to the GT heat pump input. I bet the water temp is now a few degrees higher, which means a lowering of the EER.
Clearly, I am not going to get any latent water removal, but it should pre-cool the return air. Return air is about 80 F or so.
Do you think the time/trouble is worth it? Or am I trading just one efficiency for another . . . .?
Thanks . . .
Steve
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You could run both coils in tandem off of your well pump. Then both the heat pump and the pre-cool exchangers would see the same source temperature. Some fiddling might be needed to balance the flows, but imho it would be worth it. Don't underestimate the power of 60 degree water to yank lots of latent humidity (and sensible heat) out of the return air.
If you felt daring, you could rig up a control that would adjust the flow automatically. As your heat pump ramps up, the pre-coil could do more gpm. At a certain setpoint of discharge water, the control could feed more water to the heat pump, increasing heat flow and COP.
Just running source water through the pre-cool coil while the heat pump isn't running (at reduced cfm) could also save energy. Unless your source water is very close to return air temp, then all bets are off. But knocking 5 degrees per pass off of your return air for the cost of a water pump and a blower running on low could prove to be very economical.