Re: Above Ground Pool Collapse

 

EZ-Set pools seem nice, with the air doughnut at the top... 12'x36"
for $98, 14'x39" for $159, 16'x42" for $218, 18'x48" for $297, at
Wal Mart, including a ladder and pump and filter.

They might last a long time, away from people and out of the sun.

We might put a 12'x3' pool inside a 16'x16'x8'tall greenhouse with 5 $7
doubled 1x3 bows on 4' centers and stretch 2 $20 16'x25' poly film layers
over a $20 layer of 80% shadecloth over the bows and trickle water between
them with Grainger's $157 4RD12 pump, collecting 0.8(620+1000)8'x16'
= 165.9K Btu and losing about 6h(130-34)201ft^2/R1 = 115.8K Btu on
an average January day in Phila, for a net gain of 50.1K Btu/day.

If it supplies 50K Btu/day over 5 cloudy days and 250K = (130-110)P,
it needs P = 12.5K pounds of water, 12.5K/62.3/pi/6^2x12 = 21" deep.
We might float a 10'x1" foamboard disk on top that supports a 300'x1"
$60 HDPE pipe in a flat spiral to heat water for showers, and surround
it all with 2' of mulch or bags of dry leaves.

Nick

 
And cover the pool surface with a 9'x2" foamboard disk supporting a $60
300'x1" flat pipe spiral, with a 12'x12'x2" layer of foamboard over that,
and mulch around the pool up to the foamboard, with whitewash over (how
much of?) the north wall of the greenhouse. The 2x2'(12'+16') = 112 ft^2
of mulch surronding the horizontal collector would act as a parasitic air
heater, warming the air around the collector and reducing its loss.

Nick

 
The pool comes with a filter and a 540 gph pump. With no filter,
it might push water up a few inches above the water level. With
130 F water, it might need a cooling air supply, eg a small hole
in the greenhouse near the ground and another near the peak.


...and black fiberglass window screen over that, and poly film over that.
A separate fountain pump might move a little water over the top of the film
to prevent overheating in summertime. Outdoor air with w = 0.0133 in July
in Phila makes Pa = 0.626 "Hg. At 130 F and 100% RH, Pw = 4.74 "Hg, so
a wet square foot might lose 100(Pw-Pa) = 411 Btu/h by evaporation,
more than the peak solar gain.


...about 4 feet above the collector, to reflect more winter sun onto it.

20 PI=4*ATN(1)
30 WC'N-S collector width (feet)
40 LC'E-W collector length (feet)
50 HC=3'collector height (feet)
60 AC=WC*LC'collector area (ft^2)
70 RCC=1'collector cover US R-value
80 RC=RCC/AC'collector-greenhouse thermal resistance (F-h/Btu)
90 WG'greenhouse width (feet)
100 LG'greenhouse length (feet)
110 HG=8'greenhouse height (feet)
120 FOR HR=6.9 TO 7.1 STEP .1'reflector height above ground (feet)
130 WUC=WC/2+SQR(HG^2-HR^2)'unshaded collector width (feet)
140 AGC=PI*16*16/2+PI*8^2'greenhouse cover area (ft^2)
150 RVG=.8'greenhouse US R-value
160 RG=RVG/AGC'greenhouse-outdoor thermal resistance (F-h/Btu)
170 GHGAIN=.9*(WG*620+HR*1000)*LG/6'Jan gh gain (Btu/h)
180 CGAIN=.9*(WUC*620+.9*(HR-HC)*1000)*LC/6'Jan collector gain (Btu/h)
190 SACGAIN=GHGAIN-CGAIN'sacrificial heater gain (Btu/h)
200 TA4'outdoor temp (F)
210 TP0'pond water temp (F)
220 TGAT=TA+SACGAIN*RG'Thevenin gh air temp (F)
230 CLOSS=(TP-TGAT)/(RC+RG)'collector loss (Btu/h)
240 CNET=6*(CGAIN-CLOSS)'net collector gain (Btu/day)
250 PRINT HR,"Jan (Btu/day):"TAB(35);CNET
260 NEXT

reflector
height

6.9'      Jan (Btu/day):       57521.07
7.0'      Jan (Btu/day):       57581.57
7.1'      Jan (Btu/day):       57579.94

With Pi(7^2-5.25^2)3/27 = 7.5 cubic yards of mulch or bags of leaves inside
a 14'x3' welded-wire fence circle (which would provide some pool reinforcing),
16.4K pounds of 120 F water might lose 5dx24h(120-34)(100ft^2/R24+64ft^2/R20)
= 75.8K Btu and provide (16.4K(130-110)-75.8K)/5 = 50.4K Btu/day of hot water
for 5 cloudy days in January.

Nick