Quote:
Originally Posted by RickHeid
I have a 3 ton heat pump and it works fine as it is, but I would like to reduce my electric usage as I have already put a 3 kw solar electric system on my house. I put the heat pump in myself and it is only 3 years old. I was thinking I could use it and put a plate heat exchanger in line with the evaporator. My theory being I would first cool the freon with air and then further cool it with the water being pumped through the plate heat exchanger. In my mind this would then reduce the temperature rise of the well water.
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A 3 Ton heat pump...
That would be 3 x 12,000 = 36,000 BTU/hr
I don't know what the SEER rating is of your unit, but I would guess that your unit consumes somewhere around around 5 KW/hr, or 160% of your solar system's peak output.
If you were to compare your AC heat output to your well's ability to absorb heat, if it were a closed-loop grouted borehole, it might be able to absorb about 9,600 BTU/hr or about 25% of your heat. And as you suggested, it might be able to do somewhat more, depending on your water flow rate. (This is where it is important to know your continuous flow rate.)
Be mindful that if you wish to use an open water source, the inexhaustible particulate supply in the water will eventually cause fouling in a plate style heat exchanger. Usually, tube-in-tube or tube-in-shell exchangers are used in this application because the spaces between the plates in a plate exchanger is pretty small, and therefore easily fouled.
There would be a bonus for you in that the cooling water, which would get warm, could be utilized as part of your domestic hot water, if you had a preheater tank ahead of your hot water heater.
So, there are plate collectors (or tube-in-tube collectors) that are called de-superheaters that are placed as you suggested in the condenser part of the circuit, and are for pre-heating water.
If you are wary about all this DIY, you might contact the company that installed your heat pump and ask what they would charge you to install a de-superheater.
Here's a link to a site from Alabama that discusses this technique.
-AC_Hacker