AC to heat pump chiller conversion?

[Naja002]

Thinking about another project. I try to dump as much heat as possible outside during the warmer months, but have been using an indoor car rad to conserve the heat during winter months. But I would like to keep running chilled water all year round.

This is what I'm thinking and have really only 1 question:




I can yank the condenser and install a plateHX. Re-route the pipes to and from the compressor so that the evap is now the condenser. The unit would then draw in room air and put out hot/warm air. And allow me to run chilled 24/7/365 conserving heat in the winter and dumping it in the summer with my ghetto chiller.

The evap is smaller then the condenser. So, how would that effect the system performance? I would be charging the system myself, so would a slightly larger unit make up for a loss in capacity...? (needs to handle probably ~1200w, chill to ~16C/60F, inside ambient ~26C/79F)

The intent here is to leave the unit window mountable....

[[XC] Hicks121]

Bump for ya bro!!

Lots of views, but no one has any advice??

[wdrzal]

The condenser is usually larger, but definitely rejects more heat than the evaporator absorbs.

Say you have a basic~5000 btu window AC unit. The evap absorbs 1500watts (5118btu per hour of heat) @ 45F evap temperature. So say your COP(coefficient of performance) is 3 to 1. Your compressor is using 500 watts of electricity (to move 1500 watts ,5118 btu's of heat).And must compress the refrigerant to a superheated gas so it can reject its heat. (the refrigerant must be hotter than the ambiant air)
Just about all the compressors electrical wattage is converted to heat by the compressor doing work. 1 watt=3.412 btu

example: same for a light bulb.....100 watt light bulb gives off 341.2 btu's of heat. 3.412 btu per 1 watt. All energy can be converted into any other form.

But when looking at compressor spec sheets don't confuse the COOLING WATTAGE with the ELECTRICAL WATTAGE.

So now you add the 1500 watts (5118btu)from the evap, plus the 500 electrical watts from the compressor ,turned into work (heat of compression ) is 1706 bTU . Now your condenser needs to reject the heat from the evaporator plus the heat from the compressors work, 2000 watts total or 6,824 BTU's. There are small heat gains in piping ,but there are also heat loses through the compressor shell. We will call these close to equal or off setting for this basic discussion.

The condenser must reject 2000 watts (6,824btu) to cool the refrigerant enough to turn it from a superheated gas (as it leaves the compressor)to a sub-cooled liquid (as it leaves the condenser.) The pressure & temperature the refrigerant condenses too liquid is it saturation point. You consult a P/T chart for the refrigerant being used. For a single stage the saturation point MUST be above ambient air temperature for a air cooled condenser.

This is a very over simplified ,but the way things work basically.Different refrigerants have many different properties,One of the most important to know (other than saturation point) is how many (btu's/per /pound) or (kilojoules/per/kilogram.)of heat they can carry and reject.

[Naja002]

Thanx, Walt, for the response/info.

So, if I understand what you are saying correctly, then I could reasonably expect ~1,000w of cooling ability from a 5,200K BTU unit. Which is about the level I'm at now. So, I would want to step up to at least an 8K BTU unit.

Now I believe the evap would need to be "re-plumbed", correct? Multi-circuited, so the gas would not flow through properly and change to liquid, the way it would in a condenser