Cooling of Cylinders in a Stream of Air. 



127 



diameter, thus bringing into agreement the two formulae 

 which had been obtained by different experimenters, II = ktv 

 given by Reynolds, Nicholson, Williams for large bodies, 

 while Boussinesq, Morris, King arrived at the formula 

 H = Jct V v for wires. In the case of those cylinders, with 

 which a number of readings at fairly low wind-velocities have 

 been obtained, there are indications that the value of n is 

 much smaller. With the'cylinder of diameter 1*93 cm., n at 

 very low velocities is *57, while at higher velocities n is "65; 

 and with the large cylinder of diameter 15*5 cm. n=*6 at 

 low wind -velocities, whereas at high velocities it is *98. 



Variation of Heat-Loss with Diameter. 



The way in which the heat lost varies with the diameter 

 can be obtained by comparing the heat-loss from the different 

 tubes at the same velocity. These values are plotted in fig. 5, 

 and it will be seen that the heat lost is proportional to d' bl 

 at all velocities. 



Fig. 5. 



Leer Heat t.oss'at constent veto. 





' 











13 











y 



























^ 



v II 

 m ~-56 





/ 



v-13 

 m--5S 





^ 



vl5~ 

 m--5d 

























v =■ 5 met r 



es per sec. 





v*>7 



s> 



S 



v-9 





'■ 



m-SI 





\ 



m-57 







m°-57 























Lop diameter 



Stream-Line Section. 



In several technical applications it is important that the 

 cooling system should have as small an air resistance as 

 possible, and accordingly a few experiments were made on a 

 tube of stream-line section with the object of finding its 

 efficiency for cooling purposes. The perimeter of the cross 

 section of the tube was 23*1 cm., its maximum thickness 

 being 2 cm. 



