Document xn0oeGEQnm93JYz8M1X4g12E

692 CHAPTER 49 1960 Guide Table 3... .Design Data for Three Classes of Snow-Melting System* sapbslt bat then cover risb should be reduced from 3 in. Depth d deb should always keep thermal resistance equal to 3 in. of concrete. S Depth required by structural design (should be a minimum of 3 in. of concrete). Pig. 1 .... Detail of Snow Melting Panel trace quantities about twice as often as there are for meas urable quantities of 0.01 in. or more. It is assumed that these light falls can be handled by the idling load. The remaining columns of Table 1 represent the frequency distribution of required heat output. This distribution is based on the solution to the basic equation for two values of the free area ratio, A,. This distribution represents tire basis of the analysis and is also the basis for Tables 3 and 4. For specific conditions, or for cities other than those given in Table 1, the solutions to Equation 2 are given in Table 2. Table 2... .Heat Output and Fluid Temperature for Snow-Melting System Rote of A, t - c F U ** 10 F ! - 20 F f. - 30 F Speec - Spend Speed Speed 5 10 15 5 10 15 5 10 15 5 10 15 0.08 1.0 151 205 260 127 168 209 102 128 154 75 84 94 tm 108 135 162 97 117 138 85 97 no 70 75 79 0.0 Q. 66 66 66 64 64 64 62 62 62 60 60 60 tm 66 66 66 65 65 65 64 64 64 63 63 63 0.16 1.0 ?. 218 273 327 193 233 274 165 191 217 135 144 154 U 142 169 198 129 149 17Q 117 129 id 100 105 109 0.0 9* 133 133 133 129 129 129 125 125 125 121 121 121 tm 99 99 99 97 97 97 95 95 95 93 93 93 0.25 1.0 ?. 292 347 401 265 305 346 235 261 287 203 212 221 tm 179 206 234 165 186 206 151 163 176 134 139 144 0.0 9* 208 208 208 202 202 202 195 195 195 188 188 18S tm 137 137 137 134 134 134 131 131 131 127 127 127 Note: This table b baaed ce a relative humidity of 80 percent for all air tem perature*. " rate of taowfsll, inches of water equivalent per hour, jtf free ua ratio. -- elab output, Bta per (boor) (square foot). U " air temperatore, Fahrenheit. tm * fluid temperature, Fahrenheit. Based oo construction as shown b Fig. I. " wind speed, miles per hour. Cffy Albuquerque, N. M. Amarillo, Tex. Boston, Mass. Buffalo-Niagara Falla, N. Y. Burlington, Vt. Caribou-Limestone, Me. Cheyenne, Wyo. Chicago, ill. Colorado Springs, Colo. Columbus, Ohio Detroit, Mich. Duluth, Minn. Falmouth, Mass. Great Falls, Mont. Hartford, Conn. Lincoln, Neb. Memphis, Term. Minneapolis-St. Paul, Minn. Mt. Home, Idaho New York, N. Y. Ogden, Utah Oklahoma City, Okla. Philadelphia, Pa. Pittsburgh, Pa. Portland, Ore. Rapid City, 8. D. Reno, Nev. St. Louis, Mo. Salina, Kan. Sault Ste. Marie, Mich. Seattle-Tacoma, Wash. Spokane, Wash. Washington, D. C. Desgc Output, Bfv par (Hr) (Sq R) an 1 system1 71 98 107 80 90 Oau 0 Class ID system* system* 82 167 143 241 231 255 192 307 142 244 89 (93) 83 89 49 (63) 52 138 129 165 63 72 307 425 350 293 253 69 83 (114) 93 84 (112) 115 140 206 144 138 254 255 374 165 372 260 64 (67) 134 63 (95) 50 121 202 144 155 90 298 246 212 254 140 342 98 216 217 66 81 350 97 229 263 89 157 275 86 97 111 58 (86) 98 122 85 52 (78) 102 154 152 120 144 447 155 198 228 213 92 128 133 87 127 189 117 121 144 From Air Conditioning, Beating and Ventilating, August 1957, p. 92. * Where idling rate is greater than Class I design rate, idling rate is given in parenthesis and should be used 83 Class I design output. For das 1 (residential) System*, the design output is ret at that required beat output (see Table 1) when Ar " 0 at the 98th percentile of the frequency distribution; that is where 98% of the hours have this output or less. t For Class U (comasocial) System*, the design outputis the maximum out put when A, 0 is Table 1 Oast column). i For Clare HI (industrial) Systems the design output is determined by tbe fallowing four requirements: (1) Output is never greeded for two consecutive boars; (9) Output for Ar -- 1; Table 1, is at bast 1 Btu per boor per sq ft greats than merimuro output for Ar -- 0; (3) Ar is greater than or equal to 0.6 maxi mum requirement shown b Table 1 for A, = I. That is, & -- -f- + 0.8 (q, + n) far the conditions wbere g, -- 9 + fa + 9t + g are a maximum; (4) The tree area ratio dr is unity for at least 98% of the boors listed in Table 1. Snow Melting 693 Table 4 .... Yearly Operating Data IdSnq Meftmo MSss Mattes Cfy Time,* hr per year Rate,* Btu per (hr) (sq ft) Output,* Btu per (year) (sq ft) Time,4 hr per year Output,* Oats* Btu pei (year) (*q ft) Cfy Tune,1 hr per Rote,* Output,* Btu per Btu per Time,* hr per (sq ft) (sq ft) year Out put* CW Btu per (yew) (sq ft) Albuquerque, N. M... 897 32.5 29100 22 Amarillo, Tex.............. 944 51.1 48200 33 Boston, Mass............... 1140 52.1 59400 Buffalo-Niagara Falls N. Y........................... 1702 50.2 85500 145 240 Burlington, Vt............ 1978 76.9 152000 Caribou-Limestone, Me.............................. 2563 93-0 238000 236 290 Cheyenne, Wyo........... 1808 77.7 140000 138 Chicago, HJ.................. 1848 67.8 125000 Colorado Springs, Qolo........................... 1583 63.4 100000 134 76 Columbus, Ohio......... 1383 45.0 62200 105 Detroit, Micb.............. 1790 49.0 87600 134 Duluth, Minn.............. 2922 113.8 332000 250 Falmouth, Mass.......... 1071 44.2 47400 73 Great Falls, Mont...... 1677 111.6 187000 174 Hartford, Conn........... 1412 41.9 59200 171 Lincoln, Neb................ 1906 67.2 128000 91 Memphis, Tenn......... -- Minneapolis-St. Paul, Minn.................... 454 2570 32.0 14500 95.1 244000 11 203 M 908 1260 II 969 Mt. Home, Idaho___ 1546 41.9 64800 40 IT 1530 III 1150 111 1590 1 2150 11 2520 111 2770 1 8000 II 9080 ill 9100 I 11800 I 14600 New York, N. Y....... 1532 1655 Oklahoma City, Okla. 719 50.7 44.6 56.2 77700 73800 40400 76 160 44 II 4690 III 4710 1 7050 11 7370 III 7370 I IT 2800 III 14900 111 5400 1 11800 I 2710 IT 13500 Philadelphia, Pa....... 820 31.4 25700 58 II 3100 ill 13800 1 17800* 1 20600 111 22500 1 9730 II 13200 1445 49.5 71500 182 221 17.4 3840 36 111 3110 I 9050 10700 TIT 11100 I 1300 II 1330 III 20200 1 7200 II 8390 Rapid City,-S. D.... 1873 86.4 162000 III 8700 T 3960* 11 3960 111 7390 1510 55700 I 3590 116 87 III 1360 1 7450* II 8250 III 13400 I 2970 3030 III 3030 I 2190 II 4180 III 5350 I 5540 11 6850 Hi- 7070 T 33200* Sault Ste. Marie, 11 38100 Ml 39500 I 3830 Seattle-Tacoma. 11 4250 111 4290 1 13700* n 15400 in 19100 i 9830 ii 10800 Washington, D. C__ 1104 2512 392 1673 770 44.8 4950 53.9 75400 77.7 195000 17.2 6750 39.1 65500 30.6 23600 33 54 345 44 196 33 III 2380 r 2920 ii 3370 HI 3810 i 17600* ii 22200 hi 23200 i 1410 ii 1430 iii 1430 i 8650 ii 9350 hi 9560 i 1650 n 1660 in 10810 i 4750* u 8350 i From Table 1, Column 8 X 3630 (hr per year). in 1690 in 8520 i 702 ii 721 * Bate when, idling, Bta per (Hr) (SqFt) - (0.37s + 3J) (33 - f), wbere - wind speed from Column 5, Table 1, and l = air temperature from Column 4, Tablet. mi 792 i 14200* n 17600 in 18400 * Produet of the two pi----ling columns. * Hoursof Snowfall, from Column 7, Table 1. * See footnote far Table 3. * Based on the mnrfitimi thatturfus Imnpmfaim h rmintaiiwi at nntit required output exceeds designed output, si which time design output is used regardlere of required output. Distribution of required output bsaed on Table 1. * Baaed on Idling Bate ratter than Pcrgn Bata. Air Conditioning, Healing and Ventilating, August 1957, p. 94. Notice that these solutions are for a relative humidity of 80 percent. For other values of relative humidity, corrections can be obtained by using Equations 8 and 9 as follows: dp. -4,(0.02019 + 0.055M/, (8) ~ coarnio + asssih,, m Snow-melting installations are classified in Table 3 ac cording to types as Class 1, II, or 111. These classes have been discussed thoroughly in Reference 3, and are defined in