[Greenbuilding] Comfort and shutters

nick pine nick at early.com
Fri Nov 19 15:29:22 CST 2010


<terrain at shaw.ca> writes:

> Pretty hard to model air movement

If a 70 F room is 20'x20' with 4'x8' of 56 F glass on one side 
and a (4x56+16x70)/20 = 67.2 average temp on that wall and
the opposite wall is 70 F with 16.6x10x20sqrt(8'(70-67.2))
= 15.7K cfm of convective airflow and a 15.7K/200 = 79 lfm
air velocity, it looks like we have to raise the room temp
 ALMOST ONE FULL DEGREE F! :-)

20 CLO = 1'clothing insulation (clo)
30 MET=1.1'metabolic rate (met)
40 WME=0'external work (met)
50 RH=50'relative humidity (%)
60 DATA 70.767,56,70,63
70 FOR CASE=0 TO 1
80 READ TAF,TWF'air and glass/shutter temps (F)
90 TA=(TAF-32)/1.8'air temp (C)
100 TW=(TWF-32)/1.8'glass/shutter temp (C)
110 TR=.9866*TA+.0133*TW'mean radiant temp (C)
120 TWW=(4*TWF+16*70)/20'average window wall temp (F)
130 CFM=16.6*10*20*SQR(70-TWW)'convective cfm
140 VEL=CFM/200/196.9'air velocity (m/s)
150 PA=0'water vapor pressure
160 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa
170 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa
180 ICL=.155*CLO'clothing resistance (m^2K/W)
190 M=MET*58.15'metabolic rate (W/m^2)
200 W=WME*58.15'external work in (W/m^2)
210 MW=M-W'internal heat production
220 IF ICL<.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor
230 HCF=12.1*SQR(VEL)'forced convection conductance
240 TAA=TA+273'air temp (K)
250 TRA=TR+273'mean radiant temp (K)
260 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp
270 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermediate values
280 P5=308.7-.028*MW+P2*(TRA/100)^4
290 XN=TCLA/100
300 XF=XN
310 N=0'number of iterations
320 EPS=.00015'stop iteration when met
330 XF=(XF+XN)/2'natural convection conductance
340 HCN=2.38*ABS(100*XF-TAA)^.25
350 IF HCF>HCN THEN HC=HCF ELSE HC=HCN
360 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)
370 N=N+1
380 IF N>150 GOTO 510
390 IF ABS(XN-XF)>EPS GOTO 330
400 TCL=100*XN-273'clothing surface temp (C)
410 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin
420 IF MW>58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating
430 HL3=.000017*M*(5867-PA)'latent respiration heat loss
440 HL4=.0014*M*(34-TA)'dry respiration heat loss
450 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation
460 HL6=FCL*HC*(TCL-TA)'heat loss by convection
470 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient
480 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote
490 PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied
500 GOTO 520
510 PMV=99999!:PPD=100
520 PRINT 600+CASE"'";TWF,TAF,PMV
530 NEXT CASE
540 LIST 60
550 'Innova AirTech Instruments has an excellent comfort web site...
560 'http://www.impind.de.unifi.it/Impind/didattica/materiale/
570 'microclima/innova/thermal.htm

56      70.767       -.3222994
63      70           -.322392

Passiv Haus fascists tend to overrate mean radiant temperatures.   

Nick
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