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Solar Pool Heating-Design calculation for flat plate collectors

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Posted by Siddhartha on May 28, 2006, 8:35 am
 
Hi,

I am designing a swimming pool heating system using Solar Flat plate
collectors. The volume of water is 535 cu.metre. Please let me know the
following:

1. I am staying in Muscat, Oman. The average minimum ambient
temperature in winter around 21.3 degreeC. What will be the
corresponding water temperature?

2. What should be the final desired temperature of the pool for
swimming? Is it OK if I take 27 degreeC?

3. How do I calculate the quantity of flat plate collectors (with black
coated copper fins) for heating 535 cu.metre of pool water? In the
worst winter month (January), I have to heat the pool upto 27 deg.C.
Please let me know the calculation with or without pool cover. I am
using 7.5 HP recirculation pump (1+1).

4. Can I use the same flat plate collectors for cooling the water in
summer months? If yes, how it is possible?

5. Tell me some good sources of solar pool heater manufacturers.

Regards.

Siddhartha


Posted by nicksanspam on May 28, 2006, 11:57 am
 


Sounds like overkill. You might darken the concrete around the pool
and periodically flood it instead, or bury PEX tubing in the concrete.
Or make a transparent pool cover that automatically rises when the pool
is too cool and sinks when it's too warm and sinks to the bottom with
the push of a button for swimming.


Most of the heat loss occurs from the surface...


ASHRAE says pools lose heat mainly by evaporation, at about
100(Pw-Pa) Btu/h-ft^2. Pw and Pa are the water vapor pressures
near the pool surface (at 100% RH at the water temp) and in the air
(which depends on the RH and air temp or the humidity ratio, ie
the number off pounds of water vapor per pound of dry air)
in inches of mercury.

The minimum daily temperature doesn't matter much, if the pool has a long
time constant, compared to 1 day, maybe 6x62/2 = 186 hours for a 6'-deep
pool. What's the average air temp and humidity ratio w in January? How
much sun falls on the pool? The Oman Meteorological Service in Muscat
might know. They have 12 Dell computers.

If 2K Btu/day falls on a square foot of pool at temp T (F) and the average
humidity ratio w = 0.0100, Pa = 29.921/(1+0.62198/w) = 0.473 "Hg and
2000 = 24hx100(Pw-Pa), then Pw = 1.307 "Hg = e^(17.863-9621/(460+Tp)),
and Tp = 9621/(17.863-ln(1.307))-460 = 86.8 F, a little too warm...

I've read Muscat can be very hot and humid, eg 102 F at 43% RH in June,
ie Pa = 0.43e^(17.863-9621/(460+102)) = 0.905 "Hg, so the pool above with
2000 Btu/ft^2-day would have Tp = 95.8 F if it were 102 F and 43% RH for
a few weeks in a row.


Sounds nice. I've heard 72 F is on the cool side and 86 is warmish.


With a US R1 pool cover, you might lose 2 Btu/h-F-ft^2 from the surface.


That might be difficult, since they are designed to collect heat.

Nick


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