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Old 07-26-15, 12:51 PM   #11
gtojohn
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After re-reading your original post you're not using your evaporator condensate water. With your air precooling water coil you would be also preheating your water before it gets to your condenser. It would seem any gain precooling your air might be a loss by preheating your condensing unit. Your a/c coils are more efficient than water coils because of refrigerant's change of state. Because of this it might be more important to supply the a/c with the coldest water possible. I think it might be a wash. I'd still look at something to do with the cold condensation water we discard.

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Old 07-26-15, 03:14 PM   #12
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Quote:
Originally Posted by gtojohn View Post
After re-reading your original post you're not using your evaporator condensate water. With your air precooling water coil you would be also preheating your water before it gets to your condenser. It would seem any gain precooling your air might be a loss by preheating your condensing unit. Your a/c coils are more efficient than water coils because of refrigerant's change of state. Because of this it might be more important to supply the a/c with the coldest water possible. I think it might be a wash. I'd still look at something to do with the cold condensation water we discard.
Steve already stated he would be running parallel flows to each heat exchanger. I brought up the same point earlier. The increase in heat pump coil entering water temperature would not add much load on the condensing exchanger anyway. Same thing with the condensate water: the few btu's of heat is insignificant relative to the thousands of btu's the heat pump would be moving. Maybe a tenth of a point or two in EER or COP for how much extra complexity?
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Old 08-10-15, 07:13 AM   #13
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Well I got results on my water precooler and to be succinct, Randen was exactly correct - my well water temp is too high to get a significant effect.

Basically the drop in entering air temperature was too low to be significant at all. The problem is that the entering water temperature here in central Oklahoma is just too high (mid 60s F).

I got an approximate sized evaporator cooler from an old ac unit and duct taped together a box to hold it in place in front of the existing evaporator coil. Used metal foil tape here to seal any air cracks. Thus all entering air would have to pass through new precooler. This added resistance did decrease the air flow velocity a bit (5%), but when no water was passing through the precooler none of the output parameters changed a lot. The exiting air temp did go down a bit, condensate volume went up 2%.

When water flow was introduced through the pre-cooler, it worked best when I reduced the air flow on the fan to the minimum setting, but then I got significant frost build up on the evaporator coil with two hours. The condensate volume shot up to almost a 30% increase before stopping abruptly (froze up).

The good news is there were several "a ha!" moments during the evaluation that I will comment on in another thread.

Bottom line - a well water precooler will work, but you require at least a 20 F decrease between the entering air temp and the water temp.

With the shop at 75 F, the precooler caused condensate output volume rate to increase (~ 2%), and the output air temperature did decrease by about 5%.

Yesterday I did do a test when the shop was very hot (88F). In this situation, the water precooler did augment condensate flow. My problem is that this is a difficult comparison as I don't have a similar test cooling off the shop without the well water precooler when it started hot. I may yet do this.

Now I need to build a data logger! One issue here is that I need to figure out how to measure condensate rate over time. My current method is a small glass jar (10 oz; 300 ml), a 250 ml graduate cylinder and my watch (precise, accurate and cheap). Collect condensate output volume for ~ 15 minutes. An accurate scale and measure weight over time?

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Old 08-10-15, 09:37 AM   #14
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Good info. That shows that a water radiator using my well water would help cool the shop. Especially when I first start cooling the shop and it's over 100* out there.
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Old 08-10-15, 10:31 AM   #15
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Elcam

Yes, if the difference between the entering water and the entering air is > 30 F, then you can make it work. Your problem is that your well water is even warmer than mine . . . .


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Old 08-10-15, 11:00 AM   #16
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Awesome rundown and results. With most high efficiency devices, a couple of percent translates to a higher sticker price, sometimes a lot higher. With the air handler on low, you gained something, this is good. Every little bit of water you collect is 10 times the equal volume of air the evaporator can cool, plus you can always speed up the fan to move more dry air once the room temperatures pull down to comfortable levels. Or you can "coast", turning off the compressor while still running the fan on low speed and pumping water through the precool coil. The balance points where which mode is less expensive to run when can be calculated without much effort.


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