# Thread: For those well versed in thermodynamics

1. ## For those well versed in thermodynamics

I think that's the right term.

Here's a question for you. I have a solar cover on my in-ground pool. Will the pool warm up faster if I run the filter during the day, or if I run the filter at night? In other words, with the water still, or moving?

2. Good question ; how the heck should I know I am a wood finisher, I'm sure some of the rocket scientist on here will have an answer for ya Rennie.

3. Good question. I do know I run my during the day. Afraid that running it at night would radiate the heat to outer space...

4. I'm no scientist, but I'd think you'd want to run it during the day. The ground around the pool is an insulator, but also transferring cooler temps from the surrounding ground to the pool, once you bring it to a like temperature it should stay more consistent. just my .02

5. Right now, I would be looking for ways to COOL it.

6. With the pump off during the day the water temp stratifies with very warm water at the top 4 to 6 inches. Having the filter run at night mixes it all up. The cover is left on unless we are swimming so radiating out to space should not be a huge concern....I guess.

My thoughts go either way. If the water moving under the cover (filter on) can still pick up the same amount of heat as it does when it is still I guess leaving the filter off at night and not mixing things up makes more sense. Good answers so far - let's see who else weighs in!

7. It probubly makes no differance since 1 BTU of heat will raise 1 lb. of water 1 degree f. it doesn't matter if it is moving or stagnent.

8. I don't have a pool so I'm not 100% sure of the cover you speak of, but I did take plenty of thermo in school.

I don't think it's going to be a whole lot of difference in this instance, as I understand it the heat is gathered through the light being blocked by the water. Most all this energy will be captured.

If it were something like a heating element at the top of the pool, circulating the water over it would cause it to heat up faster. The larger the temperature difference between the heating element and the water, the faster the heat transfers. In other words energy can be transfered faster to cooler water, so it's better to heat it up evenly instead of at one spot.

If I don't understand the cover correctly and it is actually acting like a heating element, then you want to circulate the water during the day for sure. I've heard of people putting coils of tubing on their pumps and running them in the day to let the tubing heated by the sun warm the water a little. Not sure how well it works, but it's an idea.

9. Originally Posted by Jeb Taylor
If I don't understand the cover correctly and it is actually acting like a heating element, then you want to circulate the water during the day for sure
I think this is the answer. Yes, the cover (looks like a huge sheet of bubble wrap) is supposed to capture energy and transfer it to the water. So, if I read your comment correctly, I need to change the settings on my timer and run the filter while the pool is in sunlight.

10. I think you want to circulate the water during the day, so that as much of the water passes by your solar lens (the cover) as possible to absorb the suns rays. During the night I don't think you want the water to circulate as there is probably more heat loss through the cover as opposed to the pool's sides (assuming a below ground pool). There will be some natural circulation (cold water will sink and be replaced by the warmer water below), but not the same as having the filter run. So in summary, pass as much water as you can by the daytime heat source (cover) and avoid passing water past the night time heat loss (cover).

Just my thought process on it.

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