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LXXXT. Convection of II eat and Similitude. 

 By A. H. Davis, B.Sc* 



Contents. 

 Introduction. 



1. Natural Convection. 



Formula. 



Examination of Formula. 



2. Convection fbom a Body in a Stream of Fluid. 



Formula. 



Examination of Formula. 



(1) Tlriu cylinders. 



(2) Spheres and thick cylinders. 



(3) Long cylinders : thick and thin compared. 

 Summary. 



Introduction. 



I^HE heat-losses from a hot body may be due to con- 

 duction, radiation, and convection. While the two 

 former may be calculated, if the constants of the materials 

 and surfaces be known, the loss by convection is com- 

 plicated by its dependence on the geometrical form of 

 the surface. Although for the simplest forms (spheres, 

 cylinders, etc.) the effect may be calculable, it is obvious 

 that in general it can only be found by experiment, using 

 either the actual object or an object of similar form. It 

 may be remarked here that, mathematically, convection is 

 a combination of hydrodynamics with the Fourier equations 

 for heat-flow, and that in the solution of the purely hydro- 

 dynamic problems presented by ships and by aircraft 

 the value of experiments with models has been proved. 

 One is led, therefore, to derive relations applicable to 

 convection from the standpoint of models. 



1. Natural Convection. 



Formula. 



Boussinesq h;is given a mathematical solution of the 

 problem of heat-loss by convection, natural t and forced %. 

 The desirability of conducting experiments and expressing 

 experimental results in a form applicable to models is 

 further indicated by the tact that study of his analysis 

 shows that he is led to consider bodies of similar form. 



' * Communicated by the Author. 

 t -Boussinesq, Comptes Rendus, cxxxii. p. 1382 (1901). 

 t Ibid, cxxxiii. p. 257(1901). 



