THE LOSS OF HEAT FROM BARE STEAM PIPES 



In a previous paper it was shown that Peclet's theory of the 

 loss of heat from a surface maintained at constant temperature 

 gives results in agreement with extensive practical tests of the 

 loss of heat from covered steam pipes. 



The purpose of the present paper is to show that the theory 

 is of the same practical value for bare steam pipes. 



The subject is chiefly of value to manufacturers of pipe 

 coverings, since they are not infrequently required to guarantee 

 a certain saving by the use of their covering over the loss that 

 would take place with a bare pipe, and it was at the suggestion 

 of one of these gentlemen that this second paper was under- 

 taken. 



In tests of pipe coverings, one of the test pipes is usually 

 tried bare, and the result used for determining the saving due to 

 the various coverings. 



Any unreasonable claims on the part of the manufacturers are, 

 therefore, liable to prompt exposure, and some reliable method 

 of estimating the saving due to their covering under the particu- 

 lar circumstances of the test is evidently of value to them. 



When a metal steam pipe of customary thickness is filled 

 with steam at rest or in motion at ordinary velocities there is a 

 constant escape of heat through the walls of the pipe. This heat 

 traverses the pipe by virtue of the conductivity of the metal and 

 on reaching the outer surface a portion is radiated to the sur- 

 rounding objects and the remainder is carried off by the contact 

 of the surrounding air. 



The conductivity of all the metals is so high that we may 

 without perceptible error neglect this part of the process and 

 simply assume the temperature of the outer surface of the pipe 

 to be the same as that of the steam within . We need only consider 

 then the manner of the escape of heat from the surface. 



