86 Applications of the Formulas 



felt. If we assume the temperature of the surrounding air to be 

 59 F., it results from what we have said in (807) that the quan- 

 tity of heat emitted per square foot per hour when the pipe is 

 bare is 298 B T 7, and for one foot of length this becomes 352. 

 To find the quantities of heat emitted per lineal foot per 

 hour, by the pipe when it is covered with a layer of hair felt of 



. 5 " 1.0" 1.5" 2.0" 2. 5 " 5-0" 



in thickness, we must, in the formula (885), make C'=- : ff = 

 .03 R= .188 feet and give to R' the successive values, in feet: 

 .229 .271 .313 .354 .396 .604 



To obtain the values of Q, we must remember that Q = K 

 -f- K' , K and K' being the coefficients of cooling by radiation 

 and air contact ; if we suppose the covering material to be 

 wrapped with canvas, A' will equal .75; and the values of K' 

 we may take from figure 4. 



These values of K' are as follows : 



53 -5i -50 -49 -49 -4 6 



then the values of Q are : 



1.28 1.26 1.25 1.24 1.24 i. 21 



The values of N are : 



.200 .367 .510 .636 .747 1.170 



Substituting the constants in formula b (886) it becomes : 



28.84 QR' 

 W+QR'N 



and we obtain the following results : 



Thickness of covering 



in inches. Value of M. 



= ^9 



9-86 



1.0 -=63.6 



.155 



11.30 



1.5 - = 49.2 



.230 



12.65 



2.0 -=41.0 



309 

 14.12 



= 35 ' 7 



21.08 



5-0 



