<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">
I built an air-cooled wall collector where the incoming air went up between the absorber panel<div>and the glazing, over the top and down the back, for a double wash of the absorber. </div><div>We used aluminum roof panels and Rustoleum Barbecue Paint, flattened with a little wood ash. </div><div> Would collection be improved by making the spacing asymmetrical; that is, making the air go faster </div><div>on one side (glass side?) of the plate? </div><div><div> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div>Clarke Olsen</div><div>373 route 203</div><div>Spencertown, NY 12165 </div><div>USA</div><div>518-392-4640</div><div><a href="mailto:colsen@fairpoint.net">colsen@fairpoint.net</a></div><div><br></div></span><br class="Apple-interchange-newline"></span><br class="Apple-interchange-newline"></span> </div><br><div><div>On Feb 19, 2011, at 12:31 PM, nick pine wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"> <div><strong><font face="Courier">Modeling an air heater with R1 single glazing with a nominal R2/3<br>inside air film resistance and an R1/3 outdoor film and 90% solar<br>transmission in 250 Btu/h-ft^2 sun on a 30 F day with 70 F inlet air<br>in a fixed font (can we fix this group to allow that?)...</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier"> 225 Btu/h <br> --- Tp Ra/AP Ta 1/cfm<br>|---|-->|-------www---------www--- 70 F<br> --- | | -----><br> | | Uhg<br> I| w I| w<br> g| w Rr g| w Ra<br> r| w c| w<br> v | v |<br> | | 1/3 <br> ---------------www--- 30 F <br> Tg -----><br> Iga<br> <br>Assuming Tg = 70 F to start makes the glazing loss to outdoor air<br>Iga = (70-30)3 = 120 Btu/h, which makes the useful heat gain<br>Uhg = 225-120 = 105 Btu/h, which makes the air temp Ta = 70+105/10<br>= 80.5 F with 10 cfm of airflow, which makes the convective glazing<br>gain Igc = (80.5-60)/R2/3 = 30.8 Btu/h, approximately, which makes<br>the absorber plate temp Tp = 80.5+(30.8+105)/R2/3/1ft^2 = 284 F, with<br>1ft^2 of plate area, which makes the average absolute plate-glazing<br>temp Tavg = 460+(284+60)/2 = 632 R, which makes the linearized<br>plate-glazing radiation resistance Rr = 1/(4x1.714E-9x632^3)<br>= 0.58 ft^2-F-h/Btu, which makes the radiative glazing heat gain<br>Igr = (284-60)/0.58 = 388 Btu/h (wow), which makes Tg = 0.9x70<br>+0.1(30+(388+30.8)/3) = 80 F, and so on...<br> <br>10 D=6/12'collector depth (feet)<br>20 FOR AP = 1 TO 5'absorber plate area (ft^2)<br>30 FOR CFM=5 TO 20 STEP 5'collector airflow<br>40 V=CFM/D/88'air velocity (mph)<br>50 RA=1/(1.5+V/5)'airfilm resistance (ft^2-F-h/Btu)<br>60 TG=60'initial glazing temp (F)<br>70 FOR I=1 TO 100'relaxation iterations<br>80 IGA=(TG-30)*3'glazing loss (Btu/h)<br>90 UHG=225-IGA'useful heat gain (Btu/h)<br>100 TA=70+UHG/CFM'collector air temp (F)<br>110 IGC=(TA-TG)/RA'convective glazing gain<br>120 TP=TA+(IGC+UHG)*RA/AP'plate temp (F)<br>130 TAVG=460+(TP+TG)/2'average plate-glazing temp (R)<br>140 RR=1/(4*1.714E-09*TAVG^3)'radiation resistance<br>150 IGR=(TP-TG)/RR'radiative glazing gain (Btu/h)<br>160 TG=.9*TG+.1*(30+(IGR+IGC)/3)'new glazing temp (F)<br>170 NEXT<br>180 EFF=100*UHG/250'efficiency<br>190 PRINT 1000*AP+CFM;"'";TG,TA,TP,EFF<br>200 NEXT CFM<br>210 NEXT AP</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">AP cfm Tg (F) Ta (F) Tp (F) Efficiency<br> <br>1 05 74.78818 88.12709 160.9878 36.25419%<br>1 10 71.01676 80.19498 155.3407 40.7799<br>1 15 69.4577 77.10846 152.7532 42.65077<br>1 20 68.55936 75.4661 151.0895 43.72877</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">2 05 69.2611 91.44334 137.74 42.88668<br>2 10 64.71699 82.0849 129.8671 48.33962<br>2 15 62.89892 78.42022 126.4515 50.5213<br>2 20 61.89681 76.46548 124.39 51.72383</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">3 05 66.82973 92.90216 126.66 45.80433<br>3 10 61.9705 82.90885 117.7309 51.63541<br>3 15 60.05735 78.98853 113.958 53.93118<br>3 20 59.02503 76.89625 111.7519 55.16997</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">4 05 65.47826 93.71304 120.2377 47.4261<br>4 10 60.45372 83.36388 110.7095 53.45554<br>4 15 58.49396 79.30121 106.745 55.80725<br>4 20 57.44931 77.13261 104.4702 57.06084</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">5 05 64.62126 94.22724 116.0589 48.45449<br>5 10 59.4962 83.65114 106.1483 54.60457<br>5 15 57.50936 79.49813 102.0662 56.98878<br>5 20 56.45863 77.28121 99.75274 58.24965</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">The glazing and plate temps fall and solar collection<br>efficiency rises with more plate area and airflow.</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">A mesh plate can further improve efficiency<br>by keeping cooler inlet air near the glazing and<br>blocking some radiation from a back wall to the glazing.</font></strong></div> <div><strong><font face="Courier"></font></strong> </div> <div><strong><font face="Courier">Nick</font></strong></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">_______________________________________________</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Greenbuilding mailing list</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">to Send a Message to the list, use the email address</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="mailto:Greenbuilding@bioenergylists.org">Greenbuilding@bioenergylists.org</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">to UNSUBSCRIBE or Change your List Settings use the web page</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org">http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org</a></div> </blockquote></div><br></div></body></html>