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Posted by George Ghio on July 21, 2005, 10:45 pm
Nick Pine wrote:
> . ----
> . .
> . . 30 F
> . .
> . .
> . pond .
> .-----------. ----
> 12' . s 4' . 12' 10.4'
> . s .
> <--S . s T .
> . s . 6.92'
> . s .
> . s .
> . s .
> .duct duct.
> ----------------------------------------------------------------------
> 12'
>
> We might build a 12'x16' equilateral A-frame with a 4'x12' shallow pond
> at the top (view above, in a fixed font) and 2 poly film water ducts
> along the north and south edges to avoid wind sliding and overturning...
> 20 psf makes 208 lb and 1082 ft-lb on each 1' EW slice of the greenhouse,
> so we need 12W = 1082 ie W = 90 pounds of water in each foot of duct, eg
> 1.44 ft^3 of water in a 16" duct.
>
> We could make each of the 10 slightly curved "half-bows" on 4' centers
> with 2 12' 1x3s with 1x3 spacer blocks every 2' and a hinge at the top,
> and use 3 horizontal 1x3 purlins.
>
> The south side could have 80% shadecloth to make hot air rise under the
> pond (which could be poly film over EPDM over foil over welded-wire fence.)
>
> If we can somehow arrange that most of the greenhouse stays cooler while
> the airpath between the shadecloth and glazing and under the pond is temp
> T during the day, and the space above the pond is also temp T, we might
> figure 0.9xsqrt(1000^2+620^2)12' = 12,712 Btu enters a 4' slice of south
> glazing on an average 30 F Jan day in Phila, and 0.81^2x4x1177 = 3813 of
> that enters the pond. At 130 F, it might also gain 6h(T-130)4ft^2x1.5
> = 36T-4680 Btu/day from the bottom, and more, if the ground to the south
> is reflective.
>
> If the glazing loses 6h(T-30)12ft^2/R0.8 = 90T-2700 Btu/day and the daily
> energy that flows into the slice equals the energy that flows out, 12712
> = 3813+(36T-4680) + 90T-2700, so T = 129 F, and the pond slice gains about
> 3813 Btu, and 50K/3813 = 13.1', so a 16' greenhouse might provide most of
> the heat in January. With about 3813x16'/6h = 10.2K Btu/h during solar
> collection, 5 gpm (2400 Btu/h-F) would rise 4 F, and 400'x1/2" PE pipe
> with 75 ft^2 of U30 surface would rise 10.2K/(75x30) = 5 F.
>
> A row house with a flat roof might have a $98 12' diameter x 3' tall
> EZ-Set pool in the basement with a $60 300'x1" fresh water pressurized
> PE pipe heat exchanger near the top of the pool under floating Styrofoam
> and a low-head pump with a $40 400'x1/2" PE pipe heat exchanger in the
> pool bottom. With lots of insulation and 0.8xPi(11/2)^2x3x62.33 = 14216
> pounds of water at 110 F after 5 cloudy days, after supplying 5x50K Btu,
> it needs to be 110+250K/14216 = 128 F on an average day. Then again, it
> might melt :-) It might need reinforcing, eg a tarp tied up around it.
> Or maybe we need a different kind of pool.
>
> This might also be a standalone structure in a yard, with the filter pump
> that comes with the pool.
>
> Nick
>
You used the word "Might" 8 times, "Could" 3 times, "If" 3 times, with a
"Maybe" and "Somehow" once each.
"Could" it be that you "Might" be proposing that "If" "Somehow" you
"Maybe" actually built one you could prove your point without using
those words that only confirm that you are in fact just guessing.
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