Earth Pipe

I have a 3 bed house that gets very hot in summer and it's been suggested an "earth pipe" may be a solution.
How much cooling effet can one expect from an "earth pipe"?
What diameter pipe is suitable? How long does the pipe run need to be? How deep does it need to be buried?
Are there any websites with further info I can go look at?
sponix
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Try this: http://mb-soft.com/solar/saving.html
Also look at this thread: http://tinyurl.com/5zohf
Google Earth pipe and earth tube on groups and web.
In Germany they spiral a 8-12" pipe around a house foundations. Easy to do when building. Pretty common there.
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Humidity can lead to condensation and mold in these pipes. You need to be careful. Mold can kill.

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Ron Ciren wrote:

Run the air thru a heat exchagnger in the house to avoid this.
NT
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May as well bury hundreds of feet of plastic pipe underground and fill this loop with water. Use this to run though a water to air duct mounted heat exchanger. Will be easier to bury the small bore plastic pipe rather than large 8 to 12 inch plastic soil pipes.
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Good idea, until crippled with actual numbers :-)
NREL says an average July day is 76.7 F in Phila, with w = 0.0133 and a 67.2 daily min and a 64.9 F dew point and a 54.3 F deep ground temp. A 5K Btu/h "earth air conditioner" with 80 F indoor air might look like this, viewed in fixed font:
1/G 1/800 54.3 F ---www---www--- 80 F <---------- I
G is a ground-to-pipe conductance and 800 is the approximate air-water conductance of a $150 MagicAire SHW2347 2'x2' heat exchanger or a $35 used 1984 Dodge Omni automobile radiator. I = 5K Btu/h = (80-54.3)/(1/G+1/800) makes G = 257 Btu/h-F. Table 7 on page 22.33 of the 1993 ASHRAE HOF suggests k = 0.65 Btu/h-ft-F as a min conductance for clay soil. A foot of 1/2" PE pipe (0.722" OD) with 0.189 ft^2 of surface and a 10 Btu/h-F-ft^2 combined wall and inner water film conductance has 1/(0.189x10) = 0.529 Btu/h-F of thermal resistance. A foot of clay soil adds ln(1/(0.722/12)/(2Pi0.65) = R0.688, ie G = 1/(0.688+0.529) = 0.822 per foot of pipe, so we need 257/G = 313 feet of pipe.
But the soil warms up. If a house in Phila needs 2weeksx10h/dayx5KBtu/h = 700K Btu/year (not much), and the soil has 313xPix1^2x30 = 29.5K Btu/F of thermal capacitance, it might warm 700K/29.5K = 24 F over 2 weeks. So that won't work.
We might improve it by putting the pipe under stone in an L' trench with an EPDM liner, with another pipe or a night sprinkling system in the trench to keep the lower part filled with water. With lots of evaporative surface compared to the heatflow and the rock's shading and low airflow resistance and poor point contact thermal resistance to downward heatflow, the trench water temp might approach the dew point vs the wet bulb temp.
1/G 1/800 64.9 F ---www---www--- 80 F <---------- I
I = 5K Btu/h = (80-64.9)/(1/G+1/800) and G = 565 Btu/h-F make G = 565/0.539 = 1048' of pipe, eg 3 $40 400' rolls in a 400' trench. If the dew point is higher than 64.9 for 2 weeks and the trench water warms 10 F, 700KBtu/10F = 70K/(1x400Wx62Btu/F-ft^2) would make the trench 1' deep X W = 2.8' wide.
A small window AC with a clogged air filter might provide dehumidification to w = 0.012, within the ASHRAE 55-2004 comfort zone. A slow ceiling fan might provide equivalent comfort with w = 0.0133 and no dehumidification.
Nick
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Oops. That's 565x0.539 = 304' of pipe, eg 1 $40 400' roll in a 100' trench.

The fan only needs to raise the air velocity from 0.05 to 0.095 m/s, ie 9.8 to 18.7 feet per minute. About 10% of the population finds 36 fpm at 80 F an annoying draft, and 160 fpm can blow loose papers off desks.
Nick
20 MET=1.1'metabolic rate (met) 30 WME=0'external work (met) 40 DATA 80,0.0120,0.05,0.5 50 DATA 80,0.0133,0.095,0.5 60 FOR CASE = 1 TO 2 70 READ TC,WA,VEL,CLO 80 TA=(TC-32)/1.8'air temp (C) 90 TR=TA'mean radiant temp (C) 100 PA).921*3377.2/(1+.62198/WA)'water vapor ressure (Pa) 110 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa 120 ICL=.155*CLO'clothing resistance (m^2K/W) 130 M=MET*58.15'metabolic rate (W/m^2) 140 W=WME*58.15'external work in (W/m^2) 150 MW=M-W'internal heat production 160 IF ICL<.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor 170 HCF.1*SQR(VEL)'forced convection conductance 180 TAA=TA+273'air temp (K) 190 TRA=TR+273'mean radiant temp (K) 200 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp 210 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermediate values 220 P508.7-.028*MW+P2*(TRA/100)^4 230 XN=TCLA/100 240 XF=XN 250 EPS=.00015'stop iteration when met 260 XF=(XF+XN)/2'natural convection conductance 270 HCN=2.38*ABS(100*XF-TAA)^.25 280 IF HCF>HCN THEN HC=HCF ELSE HC=HCN 290 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC) 300 IF ABS(XN-XF)>EPS GOTO 260 310 TCL0*XN-273'clothing surface temp (C) 320 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin 330 IF MW>58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating 340 HL3=.000017*M*(5867-PA)'latent respiration heat loss 350 HL4=.0014*M*(34-TA)'dry respiration heat loss 360 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation 370 HL6L*HC*(TCL-TA)'heat loss by convection 380 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient 390 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote 400 PRINT TC,WA,VEL,CLO,PMV 410 NEXT CASE
T (F) Wa Vel Clo PMV
80 .012 .05 .5 .5225705 80 .0133 .095 .5 .5225394
Innova AirTech Instruments has an excellent comfort web site...
http://www.impind.de.unifi.it/Impind/didattica/materiale/microclima/innova/thermal.htm
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I knew you wish you would of had a mechanical education
snipped-for-privacy@ece.villanova.edu wrote:

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snipped-for-privacy@ece.villanova.edu wrote:

need
fill this

heat
rather than

temp.
like
air-water
used
suggests
1/2" PE

combined
Btu/h-F of

ln(1/(0.722/12)/(2Pi0.65)
2weeksx10h/dayx5KBtu/h
Btu/F
So
with an

trench
surface
resistance
trench
point is

700KBtu/10F
wide.
dehumidification
fan
dehumidification.
People have done it and it works. Somewhere something isnt adding up right... but where I really dont know.
Subject: Air / Earth Tubes Newsgroups: alt.solar.thermal Date: 2003-03-29
and the appallingly written http://mb-soft.com/solar/saving.html
NT
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