26 Loss of Heat from Bare Steam Pipes 



to his test and some additional data in regard to Mr. Barrus' tests 

 has also been obtained. 



The results of the tests are shown graphically in Fig. 6. 

 The curves drawn thereon were computed as follows : 



Steam pressure 100 Ibs., temperature 338 Fahr., tempera- 

 ture of air 65 Fahr. Difference of temperatures 273. Outside 

 diameter of pipe 2.38 ins. 



Taking the value of A" at .87 we have 



R=.%-j X 1.04 X 2.03 = 1.83, 



the coefficient 1.04 for air temperature having been found from 

 Fig. 3, and the coefficient for difference of temperatures from 

 Fig. 2. 



The coefficient K' we find from Fig. 4, since the test pipes 

 were all horizontal, to be .68, choosing from Fig. i the proper 

 coefficient for difference of temperatures we have, 

 ^4=.68X 1.77 = 1.20. 



Then the loss in B. T. U. per square foot per hour per i 

 difference of temperatures between the steam and the surround- 

 ing air, 



= ^ + ^4 = 1.83+ 1.201=3.03. 



Proceeding thus for several different steam pressures the 

 curve for the 2 -inch pipe was drawn, and that for the 8 -inch pipe 

 was constructed in the same way. 



The curve for the 2 - inch pipe agrees within less than two 

 per cent with all the experiments on that size of pipe. The curve 

 for the 8 -inch pipe agrees with the only experiment on that sized 

 pipe that we have. 



It is, however, to be noted that Mr. Barrus' experiment on 

 the lo-inch pipe is not at all in agreement with the theory. 

 This experiment was made on two lo-inch pipes parallel to one 

 another and only 24 inches distant between centers, certainly not 

 the very best arrangement for a test of this kind. Although the 

 radiation would be somewhat decreased the air contact action of 

 the ascending currents of air might easily have been considerably 

 increased. 



We may say that Fig. 10 demonstrates that for a given size 

 of pipe the theory takes care of any steam pressure between zero 

 and 150 pounds. Brill's test would show that the theory also 



