Research on Thermal Contact Resistance in a Bed of Steel Square Bars Using Thermovision

T. Wylecia la, D. Urbaniakb aDepartment of Industrial Furnaces and Environmental Protection, Czestochowa University of Technology, al. Armii Krajowej 19, 42-200 Czestochowa, Poland bInstitute of Thermal Machinery, Czestochowa University of Technology, al. Armii Krajowej 21, 42-200 Czestochowa, Poland

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The article presents the results of experimental research on the determination of thermal resistance values occurring on contact surfaces of adjacent steel square bars. The places of such contact in the theory of contact heat conduction are called connectors. More generally, this problem is related to the determination of the effective thermal conductivity of the porous charge in the form of a bundle of square bars. The value of coefficient kef is necessary to optimize the heat treatment of square bars heated in the form of bundles. One of the most important parameters affecting the value of kef is the thermal resistance of the connectors. This size of this can be determined both analytically and experimentally. Due to the geometrical complexity of the connectors being created by surfaces of adjacent bars and the oxidation phenomenon, the theoretical models developed so far cannot be applied. On the other hand, in standard measurement techniques of this parameter the sample with a length of several centimeters are used, which allows measurement of the temperature distribution. Because the transverse dimensions of bars are an order of magnitude smaller, these methods cannot be used in the analyzed case, too. It was decided to use a partially innovative experimental technique to determine the considered thermal resistance. The originality of the proposed method consists in using infrared measurements to research the temperature field of the analyzed medium. On the basis of the obtained data, the value of the sought parameter will be determined using the analytical dependences concerning heat conduction.

DOI:10.12693/APhysPolA.135.263 topics: porous charge, thermal contact resistance, thermovision, effective thermal conductivity