Document 2je6zDE0pwQJ6Em6jb1JdpXM7

568 CHAPTER 24 1954 Guide Table 3. Snowfall Data fob Vakiops Cities^ Ndmbeb or Readings with 1 Maximum TtMi'EnATuAvi: in -- Period below Fbbesing at Various Snowfall Rates City Snowfall Rate in Equivalent Inch of Water per Six Hours. 0.00 1 0.25 to 0.24 to 0.49 Col.l Col. 2 Col. 3 Albany, N. ............................................... Asheville, N. ........................................... 2052 463 1640 2838 1300 29 5 4 0 3 0.50 to 0.74 Col. 4 0.75 to 0.099 Col. 5 51 10 00 0 0 1323 1871 2390 1363 1498 . 11 23 9 19 3 42 3 0. 0 1 0 1045 3 0 0 1569 2 0 1351 4 1 1207 4 0 1830 5 3 916 5 1 1 1514 44 9 1189 12 2 Madison, Wise........................................ 2370 2703 5 7 2 0 0 613 8 4 0 1795 8 1 891 10 2 1 1365 6 2 2054 33 4 1088 5 0 1 1482 5 0 1545 11 1 Washington, D. C.......................... . - 533 7 2 1 Total Taken 1 Assumed 1 Design Rate of. S nowfall" Col. 6 3720 3536 3532 3720 3720 3720 ITlO 3720 3720 3720 3720 3348 s Col. 7 0.16 0.08 0.08 0.08 0.08 0.16 0.08 0.08 0.08 0.08 0.08 0.08 0.25 0.16 0 08 0.08 0.16 0.16 0 08 0.16 0.08 0.08 0.16 0.16 0.16 6 Data from U.S.Wtatk'rBureau. daily tom November 15 to Febmery Co,. , and the sum of mrf^mCoh. 2. 3. ccoolluuJmmTnnhiecsoadnentsaaiigvneninrargagettehmeisatxfeoinmutunhmareavasadlluaineug,vaiwsnadfo. su*hnJoMdu.lCldAVUsbse_umm__ue_l_ttih_palitetdhebyla2rgtoerovbataluine tihnetmheaxhiemaudmingra0t1eif>our a=^6>-.-h--o-u--r period. This maximum rate divided by 6 is the design rate per hour. This is equivalent to dividing the larFgeorr veaxlaumepinle:thFeorheAalbdainngyo, fNth.eYs.elCecotleudmcnoslu5manndby4 3to. tal six readings, and consequently the tenth reading iiss -ii-nn---CC--oo--ll-uu--mm- ,nn_3, whic.h...h..a..s...t..h..e.....laYrg. eCrovluamlu.ne. so.3if 0a.n49d i4ntothtaelcnsooixllunrmmeanndihhneegaasdd, iianngng..d c.DDoniivvsi'ieddnuitni g 0.49 by 3,the design -- 1--5" *u luted in Column 7. iter equivalent oi v.iu juw4 , __ e New York City record was not used i n tins tabulation since for tout were not cow parable with those of the other stations. that allowances must be made for the physical properties of the circulating fluid. This fluid may be an aqueous solution of ethylene glycol, or it may be a petroleum distillate. In either case, the manufacturer should be contacted for the physical properties. Ethylene glycol solutions should Panel Heating 569 Table 4. Heat Output and Fluid Temperature for Snow Melting Systems s Rate of Snowfall = OF Velocity V 5 10 15 it = 10 F. Velocity 9 5 10 15 U = 20 F Velocity o 5 10 15 U : 30 F Velocity t> 5 10 15 0.08 1.0 So 151 205 260 127 168 209 102 128 154 76 84 . 94 108 135 162 97 117 138 85 97 110 70 75 79 0.0 So- 66 66 66 64 64 64 62 . 62 62 GO 60 60 66 66 66 65 65 65 64 64 64 63 63 63 0.16 i.o So 218 273 327 193 233 274 165 191 217 135 144 154 142 169 198 129 149 170 117 129 142 100 105 109 0.0 So 133 133 133 129 129 129 125 125 125 121 121 121 99 96 99 97 97 97 95 95 95 93 93 93 0.25 1.0 So 292 347 401 265 305 346 235 261 287 203 212 221 *m 179 206 234 165 186 206 151 163 176 134 139 144 0.0 So 208 208 208 202 202 202 195 195 195 188 188 188 - __ 137 137 137 134 134 134 131 131 131 127 127 127 Note: This table is based on a relative humidity of 80 percent for all air temperatures, s = Rate of snowfall, inches of water equivalent per hour (See Table 3). ^ = Free area ratio. Co -- Slab output, Btu per (hour) (square foot), fa = Air temperature, Fahrenheit. fm -- Fluid temperature, Fahrenheit. Based on construction as shown in Fig. 16. v = Wind velocity, miles per hour. contain a rust inhibitor (probably triethanolamine phosphate), and this :Will affect the properties slightly. For large installations, the friction losses should be calculated by the Fanning equation where }IV* ht = 2gd (14) h = the loss in head of the fluid under conditions of flow, in feet, i = the length of the pipe, in feet., V = the velocity, in feet per second. g -- the acceleration due to gravity = 32.174 ft per (second) (second), d = the internal diameter of the pipe, in feet. / = a dimensionless friction coefficient. The factor / can be determined from the Moody chart which is Fig. 4 of Chapter 4, Fluid Flow. In determination of the Reynolds number, the effect of the inhibitor should be taken into account. The manu facturer of the anti-freeze solution must therefore be consulted. For aPproximate data for ethylene glycol without an inhibitor and for. a light oil, see Table 5. For small installations requiring less than 1 hp pump capacity, it may be satisfactory to compute the pump head required from friction loss tables for hot water heating systems, as given in Chapter 22, and to cor rect for the effect of. the anti-freeze solution. Generally, hydraulic tables are prepared for water at 60 F and, 10 to 15 year old pipe. Since the circuit will be closed and the pipe will not scale