Convection from Wires in a Stream of Air. 903 



given by Hughes* for larger cylinders (0*43 — 5*06 cm. 

 diameter), steam-heated, in air (assumed 15 u C.) moving 

 with speeds of 200 to 1400 cm. per sec. These data have 

 been plotted on a graph f having heat loss as ordinate and 

 vl as abscissa ; values read off from this curve give points in 

 the upper part of fig. 1. 



Fig. 1. 



Ofl £ 





+ Kiwg, (C-003 cr»3.) 



• Ker>pei!y 



Log (v!/a>) 



Some values intermediate between the two sets above 

 mentioned were obtained from figures compiled by Lang- 

 muir I from a study of results given by Kennelly §. They 

 relate to the high velocity (800-1800 cm. per sec.) values 

 for Kennelly's largest wire (0*0204 cm.) working at tem- 

 perature excesses of 51° and 128° C. 



The graph thus obtained — * Thermal Relation } of fig. 1 — 

 is excellent, practically independent of the temperature or 

 diameter of the cylinders involved. The data range over 

 air-streams of from J to 50 miles per hour, wires of 

 0*003 cm. diameter up to 5 cm. piping, and temperatures 

 from that of boiling water to a bright red heat. 



The curve may be further examined by comparison with 

 the results of experiments by Kennelly and Sanborn ||, who 

 investigated the heat loss from a wire in air at various 

 pressures, the wire being mounted on a whirling arm in a 



* Hughes, Phil. Mag. xxxi. p. 118 (1916). 



t Davis, loc. cit. 



X Langmuir, Trans. A.I. E. E. xxxi. (1) p. 1229 (1912). 



§ Kennelly, Trans. A. I.E.E. xxviii. (1) p. 363 (1909). 



|| Am. Phil. Soc. Proc. liii. p. 55 ^1914). 



