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<br />. . .. <br />Lv... J ~.;f <br /> <br />~~r <br /> <br />Ae an example. euppoee a 30-lnch-dlameter plpe le expoeed to temperature <br />of zero and lt 11 deslred to eetlmate the tlme requlred to freeze a ehell of <br />10e 9 lnches thlok ln lt under w1nd oond1tlonB Buch that E : 5.0 Iltu/(ft.)2 <br />(hr. )(OF). Then T = 32 - 0 = 32. a = 0.50 ft. b = 1.25 ft. <br /> <br />HW _ (143~ (62.4) = 221.3 <br />iT - n.2 ) (32) <br /> <br />~=~ . ~:~5 = 2.5 loge ~:l = 0.91629 - ~2 loge ~=~ : - 0.11453 <br /> <br />(b2 _a2) <br />(4 ) <br />And: <br /> <br />= 0.32812 K (b2 _a2) : 0.13230 <br />2E ( b ) <br /> <br />'l <br /> <br />/ 7 <br />t = 221.3 / 0.32812 f 0.13230 - 0.11453/ <br />L ~ <br />It would treeze to the oenter (a = 0 ) In: <br /> <br />76.5 hourI, or about 3 daye. <br /> <br />_I <br /> <br />t = (221.3) (0.54812) = 121.3 hours, or about 5 days. <br /> <br />In order to keep a plpe from treeBlng. lt le neceBBary to eupply heat <br />enough to provide for the 10eBee. In the above caBe theee would be about <br />ET = (5.0) (32) = 160 Iltu per Iquare toot of plpe eurfaoe per hour. ThiB <br />can be Bupplled trom the water flowlng ln the plpe lf the lnoomlng water <br />temperature le sllghtly above the freeBlng polnt. If weter from a lake were <br />a'll'alleble at 400 " about 1,000 tflet of the above plpe could be Ialpt lee free <br />wlth a flow of 0.7 cublo feet per eecond. The quantlty of vater requlred to <br />prevent freeBlng oould be greatly reduced by lneuletlng or burylng the pipe. <br /> <br />Sincerely yourl, <br /> <br />/Sgd./ Robert E. Glover, <br />Head of Teohnical Sectlon. <br /> <br />:BC-Record copy <br />R.E. Glover <br />CC-Commlelioner (221) <br /> <br />25 <br />