Coeficientes de transporte em trocadores de calor bi-tubulares liso e com aletas tipo placa perfurada

Abstract

The heat transfer coefficients and friction factors we re determined experimentally in smooth and finned double-pipe heat exchangers. Experiments were performed in three heat exchan gers with fins of holled plates. At all cases the free area of holes was the same and the diameters of the holes changing. The used heat exchangers were: holes with diameters of 3mm, 5mm and 8mm. The fluids were air in enviromental conditions like cold fluid and hot water like hot fluid. The air-flow was through the annular region while the water-flow was through the inner pipe, in counter flow. Both flows were turbulents. The thermal boun-dary conditions consisted of uniform temperature on the inner surface and the outer surface being insulated. Was performed a heat transfer analisys in order to obtain the fin efficiency and annular region officiency. The heat transfer coefficients and friction factors are presented in dimensioless forms, as func-tions of the Reynolds number of the flow for the relations attain ned by the least squares fitting. Finally, it's realized a compa rison among the results of the finned heat exchangers and of the finned heat exchangers with the smouth tube.