REVIEW OF APPLIED IMECIIANICS.^ 



By L. Lecornu, 

 Member of the Institute, Inspector General of Mines, Professor at l' Ecole Poly technique. 



The domain of applied mechanics is great. The number of pub- 

 Ucations devoted to it, m Europe as well as in America, forms an 

 immense bibliography. I can not analyze here even briefly this 

 mass of material. I shall limit myself, as in former years (1903, 

 1905, and 1909), to describing a few of the most interesting residts. 



I. STEAM APPARATUS. 



Leprince-Ringuet published in the Revue de M^canique (1911) a 

 research upon the transmission of heat between a fluid in movement 

 and a metallic surface. After examining various theories and experi- 

 ments upon the subject he found that when a gas flows through a 

 tube the quantity of heat transmitted per hour per square meter 

 can be given by the expression BiCVp)'^, where B is the coefficient 

 of transmission", varying inversely as the 0.13 power of the length 

 of the tube; 6' is a coefficient increasing proportionately ^\dth the 

 temperature; F the velocity of the gas in meters; 2> the weight of a 

 cubic meter of the gas in kilograms; and n is an exponent which 

 depends upon the relation of the cross section to the perimeter. 

 For a circular tube of the diameter d it is practically 



n = -. 



1+I8d 

 \+3Qd 



The coefficients B and Ovary only slightly from one liquid to another. 



The author concludes that the exchange of heat can be consider- 

 ably increased bv increasing the flow, the eddies, and the ratio of the 

 perimeter to the cross section. It is also advantageous, whenever 

 possible, to promote the condensation upon the metallic surfaces. 



Bone developed the idea of aj)plying to the heating of steam 

 boilers a process suggested by an old invention of Lude, which con- 

 sisted in injecting through a contrivance formed of porous surfaces 



' Translated by permission from Kevue e<5n6rale ties Sciences pures et appliquiSs, Paris, July 30, 1912, 

 pp. 548-557. 



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