14 Loss of Heat from Covered Steam Pipes 



Two test pipes were employed, one 4 inches in diameter, and 

 one 10 inches; both were vertical and 36 inches in length. 



In the calculations in this case, the value of K' was taken 

 from Figure 5, instead of from Figure 4, as in the other tests. 



Further experiments with the lo-inch pipe with great thick- 

 nesses of coverings were vitiated by the fact that the ends of the 

 pipes emit heat, according to a very different law from that obtain- 

 ing for the cylindrical portion, and further, the ends being covered 

 by a thickness equal to that on the cylindrical portion the length 

 of cylindrical surface is increased. This seriously impairs the 

 value of Mr. Norton's conclusions as to the relative advantage of 

 increased thickness of covering. 



Mr. Norton also made a number of tests on the loss of heat 

 from his test pipes without any covering. 



An analysis of these reveals inconsistencies which are easily 

 explained by a study of Pellet's experiments on the conductivity 

 of metals. Mr. Norton's agitating arrangement though sufficient 

 for the slow loss of heat from a covered pipe was quite inadequate 

 for the loss from a bare pipe and the results of his experiments 

 were falsified by the resistance of the oil. We may however draw 

 certain general conclusions that are useful. 



By exposing one of his bare pipes to the draft from an elec- 

 tric fan the loss of heat was increased by about 50 per cent. The 

 radiation would be unaffected by the draft, but the air contact 

 loss, which in still air was about 40% of the total loss, must have 

 been increased by 120% or to more than double its value in 

 still air. 



Now if we take the case of the magnesia covering in still 

 air we have by the experiment a loss per sq. ft. of pipe of 147 B. 

 T. U. per hour. In this case the value of A' (radiation) was .96 

 and K' (air contact) .73. If we increase K' by 120% we have 

 K' equal to 1.6, A' remains .96 as before, and the computed value 

 of the loss per square foot of pipe would become 166, an increase 

 of 13%. 



Mr. Norton stated during the discussion that in no case had 

 he been able to increase the loss with any of the covered pipes 

 more than 10% by the draft from an electric fan. This agree- 

 ment between our calculation and his experiment gives us some 



