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Thread: Cooling a pool with automobile radiator(s) is it feasible?

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    harleysilo's Avatar
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    Cooling a pool with automobile radiator(s) is it feasible?

    I found a couple threads, one specifically where automobile radiators were used to create a pool heater in an attic. I was wondering before i found that thread, couldn't one use a radiator to cool a pool. I happen to have an unfinished basement and my pool equipment is right beside the house, so adding a loop of piping to some radiators in my basement is doable.

    However the question is would it work, and if so how much surface area would you need for it to do anything? Are we talking a bank of radiators or just a handful?

    Obviously there would be concerns that something would break and you'd have a pool pumped into your house, so maybe one should just stick with the outside the house idea which would/could be a 30 degree temp difference or so.

    I guess comparing this idea with the pool cooler i'm using the only benefit would be no losing water from evaporation since the radiator would be a closed system. However you'd have to power a fan to cause it to cool and buy $100's worth or radiators.

    Should have bought the fancy Heat pump that cools, had no idea i'd want/need to cool my pool.....
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    If it is cooling the pool, it is heating the house. Probably not what you want.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    I changed the direction of the post halfway through, and suggested it should be outside....thoughts now?
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Radiators have small surface area so you would need forced air (electric fan) to increase the heat transfer. This is what makes the solar attic feasible. Otherwise, you would need a lot of radiators to have the same effect. Also, they are probably not the best choice for chlorinated water and you would need to use aluminum only.

    The easiest and most effective solution would be to use a solar panel at night.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    A car holds about 4 gallons of water/coolant. The radiator does an efficient job of cooling that amount of water.

    Your pool holds 19,000 gallons of water. How many old radiators do you have sitting around?
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Quote Originally Posted by mas985
    Radiators have small surface area so you would need forced air (electric fan) to increase the heat transfer. This is what makes the solar attic feasible. Otherwise, you would need a lot of radiators to have the same effect. Also, they are probably not the best choice for chlorinated water and you would need to use aluminum only.

    The easiest and most effective solution would be to use a solar panel at night.
    Yes I addressed the need for a fan and the expense to run it. Only thing about the solar panels is you couldn't cool it during the day, therefore you get the cycle where you cool it every night and it slowly heats up during they day. So come 6 pm when i get home from work pool is hot again.....
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Quote Originally Posted by texasdad
    A car holds about 4 gallons of water/coolant. The radiator does an efficient job of cooling that amount of water.

    Your pool holds 19,000 gallons of water. How many old radiators do you have sitting around?
    None.

    And yes i would like to know how many gallons of recirculated water that experiences a drop in temp from say 95 to 85 from (insert method here) is needed to cool the pool from 95 to 88. It would be nice to have a formula for that, then we could discuss GPM flow through a solar panel at night or a car radiator with a fan in the shade outside at 100 with an ambient air temp of 100.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    An auto radiator is designed to work with a very large difference in temperature between the internal fluid and the air (temp difference of 100+ degrees), it would do a terrible job at cooling liquid that is already close to air temperature (temp difference of perhaps 10 or maybe 20 degrees). For small temperature differences you want huge surface areas, like an array of solar panels, not a 1 or 2 sqft radiator. Also, an actual automotive radiator is not designed to handle chlorine in the water, and is likely to have corrosion problems.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Quote Originally Posted by harleysilo
    And yes i would like to know how many gallons of recirculated water that experiences a drop in temp from say 95 to 85 from (insert method here) is needed to cool the pool from 95 to 88. It would be nice to have a formula for that, then we could discuss GPM flow through a solar panel at night or a car radiator with a fan in the shade outside at 100 with an ambient air temp of 100.
    I'm a little confused here (so what's new )but if the air temp is higher than the pool water, you will heat the pool water by running it through the radiator or solar panels. Like Jason said, a cars' coolant is entering the radiator at 185 degrees or more. There will always be a cooling effect until the air temp is 185 degrees.

    Keeping the pool covered during the day and uncovered at night will cool the pool or at least slow the rate of heat gain. That and running the solar panels at night when the air temp is lower than the water will be even more effective. Doing all that with a fountain set up on the return would be the most effective outside of a dedicated pool cooler.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Quote Originally Posted by yeggim
    Quote Originally Posted by harleysilo
    And yes i would like to know how many gallons of recirculated water that experiences a drop in temp from say 95 to 85 from (insert method here) is needed to cool the pool from 95 to 88. It would be nice to have a formula for that, then we could discuss GPM flow through a solar panel at night or a car radiator with a fan in the shade outside at 100 with an ambient air temp of 100.
    I'm a little confused here (so what's new )but if the air temp is higher than the pool water, you will heat the pool water by running it through the radiator or solar panels. Like Jason said, a cars' coolant is entering the radiator at 185 degrees or more. There will always be a cooling effect until the air temp is 185 degrees.

    Keeping the pool covered during the day and uncovered at night will cool the pool or at least slow the rate of heat gain. That and running the solar panels at night when the air temp is lower than the water will be even more effective. Doing all that with a fountain set up on the return would be the most effective outside of a dedicated pool cooler.
    You are only confused because my post didn't make sense......

    In the thread about using 4 radiators in the attic, i read many things saying it was a bad idea, but i didn't read any "it won't work at all". I guess i don't understand the difference, unless it is the temp difference. Attic maybe 125, pool water say 85 for heating, for cooling say pool water 94 outside avg air temp say 90. Is it the difference in temps that makes cooling not realistic.

    If that is it, then putting them in a basement, with an avg temp of say 70, would get the temp diff's back in range of the "radiator heater", and with less concern (for me personally) in an unfinished basement vs. the attic......
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Quote Originally Posted by JasonLion
    An auto radiator is designed to work with a very large difference in temperature between the internal fluid and the air (temp difference of 100+ degrees), it would do a terrible job at cooling liquid that is already close to air temperature (temp difference of perhaps 10 or maybe 20 degrees). For small temperature differences you want huge surface areas, like an array of solar panels, not a 1 or 2 sqft radiator. Also, an actual automotive radiator is not designed to handle chlorine in the water, and is likely to have corrosion problems.
    I didn't read the criticism regarding the radiator heater idea, not that it means anything. Wouldn't it still depend on flow rate and heat removal? Can a radiator heat better than cool for some reason i don't understand?
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Not feasible.

    The rate of heat transfer is dependent on the difference in temperature. From real-life: if you heat a chunk of metal red hot and plunge it in a bucket of water, in a matter of seconds it's cool enough to handle with bare hands, right? Come back an hour later, that chunk of metal is probably still warmer than the water in the bucket. Because as the difference in temperature decreases, so does the rate of transfer.

    In a car, the water hitting the radiator is at least 195F on a modern engine - that's when the thermostat opens. A good many cars run closer to 220 or even higher when the needle is in the center of the gauge. With a 15 psi cap and 50/50 antifreeze, the boiling point is well over 300! Compare that to a scorching day, 110 maybe? So there will be fairly rapid transfer of heat.

    Trying to get 95 degree water cool by exposing it to 90 degree air just isn't practical.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    The attic pool heater works, though not amazingly well, because it is getting something like a 40+ degree temperature difference. For lower temperature differences, you either need a huge surface area or a heat pump, A heat pump works by increasing the temperature difference dramatically, making the heat exchanger efficient.

    If you are cooling your pool, I very much doubt that you want to heat your basement. That would effectively transfer the cooling load to your home AC unit, which will not be able to handle it and your house will get quite hot and you will spend a fortune on electricity.

    If you want to cool a pool, use a fountain, solar system at night, pool heat pump with cooling mode, or a swamp cooler. Swamp coolers are a slightly involved, but still quite practical DIY project.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Thanks for explaining it further in detail for me, i appreciate it. I am currently working on a pool cooler fountain, and fine tuning it, but I'm not sure whether i need finer mist or more volume, that discussion is in some other threads.
    my-version-of-a-pool-cooler-operating-off-a-return-t48856.html

    my-pool-cooler-build-share-your-results-t48932.html

    On a side note about this current discussion, i do have a basement waterproofing system, that also incorporates a fan running 24/7 pulling air out from underneath the slab, it reduces humidity and the "basement smell" and Radon if we had any. It is on the other side of the house, but if it wasn't that could be a source for cooler 24/7 air for a radiator setup outside in the heat.....
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    But that is probably pulling outdoor air underneath the slab so it will still be warmer than the water during the day. With a solar panel or other radiator cooler, you will need to run it at night when the air is cooler than the water. There is no other way around it so you might as well use the solar panel. That way you can at least heat the water when you need to.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Quote Originally Posted by mas985
    But that is probably pulling outdoor air underneath the slab so it will still be warmer than the water during the day. With a solar panel or other radiator cooler, you will need to run it at night when the air is cooler than the water. There is no other way around it so you might as well use the solar panel. That way you can at least heat the water when you need to.
    Actually it ends up pulling air from the first story of out house.... But they claim it reduces a/c costs lol
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    If it is pulling air from inside the house, that air will need to be replaced and it will come from the outdoors. When venting a crawl space, slab or roof, the venting air should always be from the outside. Otherwise, you are just wasting energy.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Quote Originally Posted by mas985
    If it is pulling air from inside the house, that air will need to be replaced and it will come from the outdoors. When venting a crawl space, slab or roof, the venting air should always be from the outside. Otherwise, you are just wasting energy.
    Well it is designed to vent the entire basement and the pipes installed under the slab via pulling air from upstairs. If I vented my basement with outside air it would be musky and humid especially now when I'd be pulling 100 degree air in there. I won't try to defend their (b-dry) energy savings claims, I look at it as the cost of having a waterproof non humid non musky smelling unfinished basement....
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Weather you like it or not, you are venting with outside air. It just travels through the interior of the house before venting outside again. When you remove air from the inside of the house, that air must be replaced by outside air so in effect you are venting with outside air.
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    Re: Cooling a pool with automobile radiator(s) is it feasibl

    Ran the two 2x20 solar mats last night with pool uncovered. Pool temp went from 88 to about 81. It was interesting to feel the mats warm. Last nights low was 71 with low humidity. That's quite a departure from the last couple of days with similar conditions. Usually only lose 3 to 4 degrees at night uncovered. Also had the eye turned up to lightly riffle the water
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