wrote:

udarrell wrote:


... in some situations the higher SEER won't achieve any savings over
a lower SEER unit



Why?
http://www.udarrell.com/air-conditio...tent-heat.html

has a chart with the first two columns below...

Relative Humidity/Maximum Comfortable Temperature

RH Temp Atemp APMV Ftemp FPMV

60% 78.5F .221389 81.352 .2114619
50% 79.0F 78.934 .221450 81.727 .2113076
40% 79.5F 79.379 .221356 82.155 .2214492
30% 80.0F 79.842 .221377 82.549 .2213459

The ASHRAE 55-2004 comfort standard based on surveys of 21,000 people
says 78.5 F at 60% RH would have a +0.221 "Predicted Mean Vote" (very
slightly warm) on a comfort scale with -3 = cold, 0 = comfortable, and
+3 = hot. The upper ASHRAE summer comfort zone ends with PMV = +0.5.
Lowering the RH raises the upper comfort temp slightly, about 0.8 F,
according to the calculation below, but raising the air velocity from
0.1 to 0.1 m/s (the F vs A temp numbers above) raises it more, by about
4 F. In an airtight house, we might save energy by sitting under a slow
ceiling fan and lowering the humidity and raising the temperature, and
zone the house with indoor humidification... (dehumidification?)

Nick

50 CLO =.5'CLOTHING INSULATION (CLO)
60 MET=1.1'metabolic rate (met)
70 WME=0'external work (met)
80 TA=(78.934-32)/1.8'air temp (C)
90 TR=TA'mean radiant temp (C)
100 VEL=.1'air velocity
120 RH=40'relative humidity (%)
130 PA=0'water vapor pressure
140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa
150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa
160 ICL=.155*CLO'clothing resistance (m^2K/W)
170 M=MET*58.15'metabolic rate (W/m^2)
180 W=WME*58.15'external work in (W/m^2)
190 MW=M-W'internal heat production
200 IF ICL.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor
210 HCF=12.1*SQR(VEL)'forced convection conductance
220 TAA=TA+273'air temp (K)
230 TRA=TR+273'mean radiant temp (K)
250 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp
260 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermed iate values
300 P5=308.7-.028*MW+P2*(TRA/100)^4
310 XN=TCLA/100
320 XF=XN
330 N=0'number of iterations
340 EPS=.00015'stop iteration when met
350 XF=(XF+XN)/2'natural convection conductance
360 HCN=2.38*ABS(100*XF-TAA)^.25
370 IF HCFHCN THEN HC=HCF ELSE HC=HCN
380 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)
390 N=N+1
400 IF N150 GOTO 550
410 IF ABS(XN-XF)EPS GOTO 350
420 TCL=100*XN-273'clothing surface temp (C)
440 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin
450 IF MW58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating
460 HL3=.000017*M*(5867-PA)'latent respiration heat loss
470 HL4=.0014*M*(34-TA)'dry respiration heat loss
480 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation
490 HL6=FCL*HC*(TCL-TA)'heat loss by convection
510 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient
520 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote
530 PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied
540 GOTO 580
550 PMV=99999!:PPD=100
580 PRINT 1.8*TA+32,RH,CLO,PMV


A lot of factors enter into the individual human comfort level equation.
Please put all those factors into meaningful communication content that
techs and consumers can use for the benefit of everyone.
Very interesting Nick, Villanova has to be an enlightening institution.
Do you have a website? - udarrell

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