From nick@vu-vlsi.ee.vill.eduFri Nov 25 11:36:52 1994 Date: 22 Nov 1994 10:59:08 -0500 From: Nick Pine To: renew-energy@twosocks.ces.ncsu.edu Subject: Another drumwall water heater? Here is another possible design for a drumwall that might be used as a solar water heater. It would use 30 drums, stacked up horizontally in a square array, 20'long x 6' tall, perhaps behind 120 square feet of single pane glass, with a reflective insulating shutter that lifts up from the top edge of the drums at a 45 degree angle, and a reflective floor, inside a shed with a south wall made of, eg Dynaglas. It might look like this, not to scale: ......................................... ... . . . . . . . south east . . . . . d. . . . . y. day. . ......................................... .. 10' n. H...... . .. . D . D . . . . . . . . . a. n. . . ......................................... <--S g. i...... . . . . . . . . . . . . 6' l. g. . . 6' ......................................... a. h...... . . . . . . . . . . . . s. t. . . ............................................................................ | 20' | The D's are drums, H is a horizontal hinge... Day and night shutter positions are shown... The numbers below again indicate drum water temperatures in degrees F, from a small simulation using average Philadelphia weather conditions in January (ambient temp, 32 degrees, 1200 Btu/day of sun on a south-facing wall, T^4 heat loss) while extracting 100K Btu/day of domestic hot water from the wall, using some food-grade, *lined* drums plumbed in series, on the top row, pressurized with cold water on the way to the input of an electric hot water in a house. It looks like 4 heat exhanger drums are enough. Nick 10 'Todd Hall drumwall solar water heater? 20 'est. water temps for rectangular drumwall with 45 degree upward shutter 30 NH=10'number of horizontal drums 40 NV=3'number of vertical drums 50 ND=NH*NV'total number of drums 60 PI=4*ATN(1)'pi... 70 AD=(2*(23/2)^2*PI+23*PI*35)/144'drum area in ft^2 80 DIM T(NV, NH)'array of drum water temperatures 90 OPEN "drumout" FOR OUTPUT AS #1 100 'find steady-state temps 110 FOR R=1 TO NV'1 is top row, nv is bottom row... 120 FOR D=1 TO NH'1 is west drum in row... 130 T(R,D)=150'initialize drum temps 140 NEXT:NEXT 150 AREA=4*NH*NV'effective area of drumwall surface 160 SUNH=1.85*AREA*1000/ND/24'hourly sun energy/drum, inc. by shutter refl. 170 ES=15*5*3*8*55'energy for 15 5 min, 3 gpm, 110 degree showers/day 180 UH=ES/24'useful hourly heat output of drumwall 190 GLOSSF=1.74E-09*6*AREA/ND/24'factor for heat lost thru glazing per drum 200 AMRADF=(32+459)^4'factor for radiation from surroundings to drumwall 210 CP=55*8'thermal mass of a drum full of water 220 CLS 230 HMAX=192 240 PRINT #1,"Charging mode, with sun..." 250 PRINT "Charging mode, with sun..." 260 DT=.1'simulation time step 270 FOR H=0 TO HMAX+.01 STEP DT'hours of use 280 TECON=0'initialize total convection heat from below 290 LB=UH*DT/(T(1,NH)-55)'water moved thru system per time step 300 GOSUB 740 310 'adjust top drum row temperatures 320 FOR D=1 TO NH'drum number in top row 330 TD=T(NV,1)-T(1,D)'temp diff between top drum and lower drums 340 IF TD>0 THEN ECON=TD*AD ELSE ECON=0'convection heat from below 350 TECON=TECON+ECON'accumulate total hourly convection heat 360 HEATFLOW=(SUNH+ECON-((T(1,D)+459)^4-AMRADF)*GLOSSF)*DT 370 T(1,D)=T(1,D)+HEATFLOW/CP'adjust top row drum temp 380 IF T(1,D)>T(NV,1) THEN T(1,D)=T(NV,1)'limit upper drum temp 390 NEXT D 400 ECONA=TECON/(NH*(NV-1))'heatflow to top row from average drum 410 FOR R=2 TO NV'adjust bottom row temps 420 FOR D=1 TO NH 430 HEATFLOW=(SUNH-ECONA-((T(R,D)+459)^4-AMRADF)*GLOSSF)*DT 440 T(R,D)=T(R,D)+HEATFLOW/CP 450 NEXT D 460 NEXT R 470 IF INT(10*H+.05) MOD 480= 0 THEN GOSUB 800'print drum temp array 480 NEXT H 490 PRINT #1, 500 PRINT 510 PRINT #1,"Storage mode, with no sun..." 520 PRINT "Storage mode, with no sun..." 530 FOR H=DT TO 168+.01 STEP DT'hours of use 540 TECON=0'initialize total convection heat from below 550 'adjust top drum row temperatures 560 LB=UH*DT/(T(1,NH)-55)'water moved thru system per time step 570 GOSUB 740 580 FOR D=1 TO NH'drum number in top row 590 TD=T(NV,1)-T(1,D)'temp diff between top drum and lower drums 600 IF TD>0 THEN ECON=TD*AD ELSE ECON=0'convection heat from below 610 TECON=TECON+ECON'accumulate total convection heat 620 T(1,D)=T(1,D)+ECON*DT/CP 630 IF T(1,D)>T(NV,1) THEN T(1,D)=T(NV,1)'limit upper drum temp 640 NEXT D 650 IF INT(10*H+.05) MOD 240= 0 THEN GOSUB 800'print drum temp array 660 ECONA=TECON/(NH*(NV-1))'heatflow to top row from average drum 670 FOR R=2 TO NV'adjust bottom row temps 680 FOR D=1 TO NH 690 T(R,D)=T(R,D)-ECONA*DT/CP 700 NEXT D 710 NEXT R 720 NEXT H 730 END 740 T(1,1)=(LB*55+(CP-LB)*T(1,1))/CP'move 55 degree water into top left drum 750 IF T(1,1)<55 THEN T(1,1)=55'limit lower drum temp to 55 760 FOR D=2 TO NH'move water across top row 770 T(1,D)=(LB*T(1,D-1)+(CP-LB)*T(1,D))/CP'move water from top drum d-1-->d 780 NEXT D 790 RETURN 800 PRINT #1, 810 PRINT 820 PRINT #1,"Day:";INT(H/24+.01) 830 PRINT"Day:";INT(H/24+.01) 840 FOR RS=1 TO NV'display drum temperatures 850 FOR P=1 TO NH-1 860 PRINT #1,INT(T(RS,P)+.5);TAB(6*P); 870 PRINT INT(T(RS,P)+.5);TAB(6*P); 880 NEXT P 890 PRINT #1,INT(T(RS,NH)+.5) 900 PRINT INT(T(RS,NH)+.5) 910 NEXT RS 920 RETURN Charging mode, with sun... Day: 0 149 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 Day: 2 95 120 136 146 152 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 Day: 4 96 121 137 146 153 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 156 Day: 6 96 122 137 147 153 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 157 Day: 8 97 122 138 148 154 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 158 Storage mode, with no sun... Day: 1 89 112 128 138 145 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 149 Day: 2 84 104 118 128 135 139 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 141 Day: 3 80 97 110 119 125 129 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 132 Day: 4 75 90 101 109 115 120 123 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 124 Day: 5 71 83 93 100 106 110 113 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 115 Day: 6 67 77 85 92 97 101 104 106 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 107 Day: 7 64 72 78 84 88 91 94 97 99 99 <--hot water temp 99 99 99 99 99 99 99 99 99 99 supplied to house 99 99 99 99 99 99 99 99 99 99 after a week w/o sun, in January