Loss of Heat from Covered Steam Pipes 



reduces the loss from 150 to 85, a reduction of forty-three per 

 cent, instead of fifty. This is because the surface resistance to 

 loss is the same in both cases. In all these examples the cover- 

 ings are supposed to be surrounded by a thin canvas jacket. 



It is of interest, though perhaps of no particular practical 

 value, to note that if we employ a pipe covering having a con- 

 ductivity greater than 6.00, which is not so very much greater 

 than that of some plaster, the loss of heat will increase with the 

 thickness of the covering, and may even be greater than for the 

 bare pipe. This is because the action of the increased surface 

 outweighs the feeble resistance of the covering. 



1.5 2. 2.5 



Thickness of covering in inches. 



3.5 



The Effect of Different Steam Pressures. Figures 7 and 8 

 should prove of value in the judicious choice of thickness of cov- 

 ering for very high steam pressure on the one hand and for the 

 conveyance of hot water on the other. 



The Effect of Different Sized Pipes. A little consideration 

 will show that if, in our efforts to stop the escape of heat by an 

 increase of thickness, we at the same time present a larger area 

 for its passage, our gain will be but slight. This is precisely what 

 happens with thick coverings on small pipes, as shown in Figure 

 9. We see that a one-inch pipe requires one and three-quarters 

 inches of covering to keep the loss per square foot on its surface 

 the same as for a ten -inch pipe with only eight-tenths of an inch 

 of covering. This Figure is an excellent example of the danger 

 of interpreting a theory from a too narrow point of view. It evi- 

 dently indicates that coverings for large pipes should be thinner 



