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re: is solar viable for our new house?
16 feb 2001
george estep wrote:
>assuming the water was at 150 degrees f at the beginning of the test...
if we do it that way...
>tau = 14 days/-ln((32-20)/(150-20)) = 5.9 days = 141.6 hours
or maybe it cools to 32 f after t1 = -5x8rln((32-20)/(150-32)) = 91.43r
hours, and freezes solid after another t2 = 144x5x8r/(32-20) = 480r hours,
and t1+t2 = 2x7x24 = 336 = 571.43r, so r = 0.588 f-h/btu...
>the effective r-value for a 7' long x 6" diameter tube is approximately:
>
>r = 3.54 h-f/btu*7ft*(0.5*pi)ft = r-4.9
and rv = ra = 0.588h-f/btu*7ft*(0.5*pi)ft = r6.5 ft^2-f-h/btu.
by comparison, a 4x8x8' box containing 16,384 pounds of water with 256 ft^2
of r20 surface would reach 32 f in -16384r20/256ft^2ln((32-20)/(150-32))
= 2926 hours and freeze solid after another 144x16384r20/256ft^2/(32-20)
= 15360 hours, after a total of 18286 hours or 2.086 years in the freezer.
nick
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