improve efficiency black pipe solar heater?

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Norman Martin
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improve efficiency black pipe solar heater?

Postby Norman Martin » Fri 28 Nov, 2008 08:35

My pipes lie on the ground. Is it best to cover them with polythene sheeting to improve heat absorbant efficiency? Best black sheeting (black body effect) or transparent sheeting (glass house effect) ? Does anyone know if it works? I realize the film will degrade in the sun but it is cheap and could be replaced every year.


Me...

Re: improve efficiency black pipe solar heater?

Postby Me... » Thu 26 Feb, 2009 07:09

Seen that done more than a few times and it works too, ugly but works. How many runs of pipe do you have? Several runs of slower moving water will work better then 1 large run of fast moving water. I have seen the pipe poured in a deck also. A valved manifold on either side of the pipe runs in case it needs to be adjusted or even turned off is a good idea.
Normartin

Re: improve efficiency black pipe solar heater?

Postby Normartin » Thu 26 Feb, 2009 15:54

Me... wrote:Seen that done more than a few times and it works too, ugly but works. How many runs of pipe do you have? Several runs of slower moving water will work better then 1 large run of fast moving water. I have seen the pipe poured in a deck also. A valved manifold on either side of the pipe runs in case it needs to be adjusted or even turned off is a good idea.


Thanks very much for your reply. But black or transparent PE film? I think transparent best. Installation is as you suggest. It's down a bank so you can't see it. I am in Madrid. My email is [email protected]
Norman
Me...
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Re: improve efficiency black pipe solar heater?

Postby Me... » Thu 26 Feb, 2009 18:04

I have no idea ATM as to what covering would be best. I wonder why any actually as the piping getting direct sun on it seems to work quite well. As for cover, I would be making sure the pool was covered real well to make sure the heat was retained.
chem geek
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Re: improve efficiency black pipe solar heater?

Postby chem geek » Thu 26 Feb, 2009 23:13

A pool cover is a good idea, but it should be a clear plastic bubble-type cover so that most of the sunlight shines through (it's OK if it blocks UV, but should let through most visible and infrared light). This will allow for substantial heating during the day while preventing evaporation and convection both day and night which is a major source of heat loss. The bubble-type cover also insulates against losses from conduction.

During the peak of summer around noon, a typical pool can be heated by about 0.7F degrees per hour, assuming most of the light makes it through the cover. Over a summer day in July in Arizona that can result in around a 5.3F rise while in June in New York it's around 3.9F.

The key to heating with a solar panel or pipe system is the amount of area exposed. As Me... pointed out, you want to have your water flow thinned out to maximize the surface area and that usually results in a lower flow rate. It's not the flow rate itself that matters, but the surface area. In fact, for the same surface area, you want a faster flow rate since slower flow rates heat up the water too much so it re-radiates back out too much. A properly operating solar panel at high efficiency is actually only slightly warmer than the ambient air.

If you had a solar panel that was 60% efficient and the same area as your pool, you'd get the temperature rise numbers I gave above since a white plaster pool absorbs about 60% of the sun's energy that hits it. I have more technical info about all of this in this thread . Typical flat black mat panels such as shown here are around 80% efficient (i.e. absorb 80% of the sun's energy over their area). Notice how they distribute the flow through many small narrow tubes so the water flow is like a sheet. That is what makes it more efficient.

Richard
ldb1954
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Improve efficiency black pipe solar heater?

Postby ldb1954 » Fri 22 May, 2009 03:36

Im thinking of doing this but cant find a small low flow per minute circulating pump. Can someone tell me where I could find one, as Id like to hook it up seperate from my pool pump? Thank you.

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