Estudo experimental de um descritor invariante do resfriamento conjugado por convecção forçada-condução de aquecedores discretos em canais

Abstract

In this research was carried out an experimental study of the conjugated heat transfer by convection forced-conduction of discrete protruding heaters assembled in a rectangular duct with forced internal air flow. The heat loss of the heaters occurred by two mechanisms of heat transfer, by forced convection on the surfaces exposed to the air flow and by conduction to the substrate plate. Two substrates were analyzed, one being adiabatic and the other conductive. The convective process was described by the adiabatic convective coefficient, while the conjugated process of heat transfer for convection forced-conduction by a matrix of conjugate coefficients, therefor these two descriptors invariant with the heat exchange rates. The effects of the heaters cooling on the two substrates were compared by these invariant descriptors. The experiments were carried out in an aerodynamic tunnel of the suction type with open return. The flow used was in the scale Re 2000 to 10000, being considered in the transition region. The tests were performed containing three protruding heaters on the substrate. In this case, only one active heater was considered at a time, thus verifying its influence on the others. It is intended to perform an experimental validation of an invariant descriptor of the heat transfer conjugate process by convection forced-conduction of discrete heaters in channels, by the conjugate influence coefficients, and thus to determine a conjugate matrix. The results found for the adiabatic substrate presented a difference in experimental and the estimated temperatures in the range of 0.13 to 5.86%. While with the conductive substrate this difference was from 0.41 to 7.51%. Validating the matrix of the conjugated coefficients proposed by Antonini Alves (2010).