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.
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:
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=29.921*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 ICLHCN 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 TCL=100*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 HL6=FCL*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...
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