Heat Transfer with Thermal Control Applications

Abstract

XIVcritical locations on space shuttle orbiter-type vehicles. Schneider has developed a general correlation for section weight of passive and ablative insulators used in mild aerodynamic heating environments. Performance of ablator materials in ramjet environments is the subject of the last paper by Cohen, Couch, and Murrin.A number of individuals played key roles during the preparation of this volume, and to them I owe a debt of gratitude. AbstractThe nature of thermal rectification which occurs at certain contacts due to induced thermal stresses has been investigated. The distortions produced are not only detrimental to joint conductance but also frustrate the design of thermally predictable assemblies. The analyses presented indicate the factors that must be considered when the intention is to produce a joint with high heat-transfer characteristics and low local stresses. The study has highlighted the pitfalls that can be encountered unknowingly by measuring techniques. Where necessary, experimental evidence is presented to corroborate the presented theory. Nomenclature a = radius of a microcontact, ym c = radius distinguishing contact and noncontact regions,m g( ) = constriction alleviation factor g f ( ) = first derivative of g( ) i= index relating to heat flow direction k = thermal conductivity, wnT 1 K" 1 Abstract Conduction shape factors for a disk on an insulated half-space with arbitrary surface heat flux prescribed have been calculated. The solution of the differential equation was obtained by formulating the problem numerically in the oblate spheroidal coordinate system. The uniform heat flux case and that corresponding to a uniform disk temperature were solved to test the stability and convergence of the numerical solution scheme. Dimensionless resistances were found to be 0.2716 and 0.2507, respectively, which agree to within 1/2% of the analytically known values. In both cases a 40 x 20 grid was chosen,and solutions converged uniformly to the stated accuracy in less than 50 sec IBM 360/75 computing time. Five additional cases were run^and dimensionless resistance values were obtained which lie above and below the bounds formed by the two classical solutions cited previously* Abstract This paper describes the equipment, procedure, and results of an experimental investigation on the overall thermal resistance of sphere-flat contacts. Two spherical specimens having diameters of 1 and 2 in. in elastic contact with relatively smooth flats were examined. Tests were conducted with air and argon, pressures ranging from atmospheric conditions to 10~5 mm jjg. The effect of a lubricant, with and without air present, also was studied. Mechanical loads were varied from 3.6 to 160 Ib, thereby producing contact radii varying from 4.34 x 10"3 to 1.53 x 1CT 2 in. The experimental results are in good agreement with the theory previously published by these authors. AbstractAn analysis is presented for predicting the local contact conductance of a woven metallic wire screen contacting two smooth solids under vacuum co...