229 



An Apparatus for the Stttdy of the Radiation from Covered 

 AND Uncovered Steam Pipes. 



By O. W. Silvey and G. E. Grantham. 



"Tbe iiR'asnreiuent of the efficiency of materials in preventing loss of 

 beat from hoilies involves the determination of the constant K in the 

 expression : 



A(t2-t,) 



Where D = thicl^uess of the specimen. 



H = Amount of heat per sec. flowing through A. 



A = Area of specimen. 



ti = Temperature of cooler side of specimen. 



U ^= Temperature of hotter side of specimen. 

 "The determination of H, ti, and t, are attended with considerable 

 diflieulty if accurate work is attempted, and for much engineering work 

 the relative efficiency of two coverings for heated surfaces is all that is 

 required. For the testing of the relative efficiency of two such substances 

 as are conunonly used for covering steam pipes, or for determining the 

 relation between the heat loss from a covered pipe and that from an un- 

 covered pipe, the following method has been found suitable: 



"The apparatus consists of two short pieces of steam pipe which may 

 be heated electrically from within by means of a current bearing coil 

 of wire immersed in oil. If sufficient electrical energy be supplied, the 

 pipe becomes gradually heated to some temperature at which the amount 

 of heat energy lost to the surroundings is just equal to the electrical 

 energy siipplied to the heating coil. By measuring the electrical energy 

 with an ammeter and voltmeter we may find at once the amount of heat 

 lost from the pipe by radiation, convection, and conduction. At some 

 temperature the heat loss would be such as to require some other rate of 

 energy supply to keep the temperature of the pipe constant, and the 

 electrical supply would, therefore, have to be varied. Again, if the bare 

 pipe be heated to some convenient reference temperature (200°O iB 

 usually selected for testing steam pipe covers) and the current adjusted 



