It's not *my* job to remedy deficiencies in *your* education.
(cargo?) WARM HEAVY work-pants? (google not much help)
Dec 13, 2006
29 Replies
Nor mine. So far, we merely have two different opinions. YOU made a claim, and I invited you to justify it.
Nick
Look up
Carhart Dickies Skillers Duluth ___________________________ Keep the whole world singing. . . . DanG
Actually, remedying deficiencies in your education *is* your responsibility.
Here's how I figure it:
20 TDB=-2.2'average daily min temp in January in Duluth (F) 30 TDBC=(TDB-32)/1.8'dry bulb temp (C) 40 V=11.6'windspeed (mph) 50 W=.0012'average humidity ratio 60 PA=29.921/(1+.62198/W)'vapor pressure ("Hg) 70 E=3.3772*PA'vapor pressure (kPa) 80 TDP=9621/(17.863-LOG(PA))-460'dew point temp (F) 90 IF TDP>TDB THEN TDP=TDB 100 TDPC=(TDP-32)/1.8'dew point temp (C) 110 GAMMA=.00066*101.325'constant for wet bulb temp calc 120 TDC=(TWBEC+TDPC)/2 130 DELTA=4098*E/(TDC+237.3)^2 140 TWBC=(GAMMA*TDBC+DELTA*TDC)/(GAMMA+DELTA)'wet bulb estimate (C) 150 IF ABS(TWBC-TWBEC)>.01 THEN TWBEC=TWBC:GOTO 120'iterate to 0.01 C 160 TWB=1.8*TWBC+32'wet bulb temp (F) 170 IF TWB>TDB THEN TWB=TDB 180 A=.002056*TDP+.7378'coefficient in Niles equations 190 TS=92'skin temp (F) 200 QR=1.63E-09*((TS+460)^4-A*(TDB+460)^4)'radiation loss (Btu/h-ft^2) 210 QC=(.74+.3*V)*(TS-TDB)'convection loss (Btu/h-ft^2) 220 B=3.01*(.74+.3*V)*((TS+TWB)/65-1) 230 QE=B*(TS-TWB)-QC'evaporation loss (Btu/h-ft^2) 240 PRINT TDB,TWB,TDP 250 PRINT QR,QC,QEdry bulb wet bulb dew point
-2.2 -2.2 -2.2 F
radiation convection evaporation
98.83666 397.524 59.00485 Btu/h-ft^2NREL's V = 11.6 mph in line 40 was probably measured at an airport. Changing to V = 0 lowers convection to 70 and evaporation to 10, so radiation loss dominates.
NREL's 24-hour average humidity ratio makes the wet bulb and dew points higher than the dry bulb, which probably means there's frost on an average January night, which might warm you up.
Thanks for the "education" :-)
Nick
Heat transfer by radiation for bare skin? What about the effect of clothing on radiation efficiency?
Won't your "TS" be much closer to air temp than body temp?
Or we're you just looking for SWAG on bare skin Q as a starting point?
In any case, for properly clothed human in a cold environment, QR looks to be pretty low compared to other mechanisms
cheers Bob
cheers
...
But one would assume you're not going to be standing out directly as a radiative body. The outer layer trying to radiate to the environment won't be but a few degrees warmer than the ambient, certainly nothing even remotely close to 90F.
Heat transfer by radiation for bare skin? What about the effect of clothing on radiation efficiency?
Or we're you just looking for SWAG on bare skin Q as a starting point?
In any case, for properly clothed human in a cold environment, QR looks to be pretty low compared to other mechanisms
cheers Bob
PS for everyone's information, here is a qualitative article about heat loss (while outdoors, low, moderate & heavy exertion levels) hiking & backpacking related but IMO applicable to working outside as well
bottomline of the article ......QR generally very low in comparison except when person is inactive (esp at night) in a windless condition...then QR remains where heat loss by other means have fallen.
SO...wrt to keeping warm while "working" QR is not importatnt unless our subject's job involves sleeping outside. (at night) :)
Yes. Clothing lowers the losses.
Maybe. I measured 92 F in a 70 F room.
Nick
Thanks to all for the WONDERFUL replies!
What a super group this is!
David
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