Sneak
Peak Video of the |
Download
Over 100Meg of |
re: r: r: we are looking for agents world wide 5 jul 2004 greetings andrea, i suggest you ignore paul's angry outbursts. he doesn't own this group. >...anyhow if someone except you may have some problems in dealing with >air distribution and air diffusion , laminar and turbolent cross flows, >and the fanger pmv or ppd can write me...i can reply and try to solve >the problems... that's generous and on-topic. i have a couple of questions: 1. if you put some water inside a perfectly-insulated cup, would it find itself close to the dew point temp, as water evaporates from the surface and water vapor molecules diffuse to the top of the cup, while the air above the water acts as a good insulator (about r5 per inch for downward heatflow)? which water depth will keep it coolest in an r5 3" diameter x 6" tall cup? as we fill the cup, the air layer insulates less, but more water evaporates, according to fick's law, because the concentration gradient increases as the air layer thins, no? 2. ashrae-standard 55-2004 ("thermal environmental conditions for human occupancy") defines two "comfort zones," winter (with a clo = 1 clothing thermal resistance) and summer (clo = 0.5.) its basic program estimates the predicted mean vote (pmv: +3 hot, +2 warm, +1 slightly warm, 0 neutral, -1 slightly cool, -2 cool, and -3 cold) and the predicted percentage dissatisfied (ppd) based on clothing, activity, metabolic rate, external work, air temp, mean radiant temp, air velocity, and rh... 50 clo = 1'clothing insulation (clo) 60 met=1.1'metabolic rate (met) 70 wme=0'external work (met) 80 ta=19.6'air temp (c) 90 tr=19.6'mean radiant temp (c) 100 vel=.1'air velocity (m/s) 120 rh=86'relative humidity (%) make one of rh or pa non-zero... 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'intermediate 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 hcf>hcn then hc=hcf else hc=hcn 380 xn=(p5+p4*hc-p2*xf^4)/(100+p3*hc) what's going on in lines 350-380? 390 n=n+1 400 if n>150 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 mw>58.15 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 why does line 510 use m instead of mw? 520 pmv=ts*(mw-hl1-hl2-hl3-hl4-hl5-hl6)'predicted mean vote what's going on in line 520? 530 ppd=100-95*exp(-.03353*pmv^4-.2179*pmv^2)'predicted % dissatisfied 540 goto 580 550 pmv=99999!:ppd=100 580 print ta,rh,clo,pmv,ppd t (c) rh clo pmv ppd 19.6 86 1 -.4778556 9.769089 23.9 66 1 .4732535 9.676994 25.7 15 1 .5239881 10.74283 21.2 20 1 -.4779105 9.770202 23.6 67 .5 -.4747404 9.706658 26.8 56 .5 .5145492 10.53611 27.9 13 .5 .5003051 10.23146 24.7 16 .5 -.4883473 9.982468 the first 4 lines are the winter comfort zone corners. the second 4 lines are the summer comfort zone corners. nick |