Experimental investigations of pressure drop and friction factor in compact heat exchanger using computational fluid dynamics

Abstract

Automotive radiator tubes carry the hot engine coolant and help in exchanging the heat to the ambient, through the extended fin surfaces. Any improvement in the rate of heat transfer per unit surface area of the radiator tube will be helpful in enhancing the overall thermal performance of the radiator. Enhancement in heat transfer can be effected either by increasing the surface area in the air side or by enhancing the heat transfer coefficient in the inner side i.e., fluid to tube inner surface. Increasing the turbulence of the engine coolant fluid inside the tubes will increase the heat transferred from the fluid to the tube inner surface. Several turbulence enhancement devices were tested so far. Triangular winglet turbulator(s) placed on the bottom wall of the radiator tube was studied experimentally to assess the heat transfer enhancement, by the increased fluid side temperature drop across the tube, with water as the working fluid. Three variations in the triangular winglet turbulators were studied; A) First setup with only one triangular turbulator placed at the entrance region of the radiator tube; B) The second setup two triangular turbulators and C) The third with three numbers of triangular turbulators placed in the bottom wall. Experiments are planned for conducting tests on a simplified and scaled up radiator tube, for easy provision and access of the instrumentation. Temperature values measured at strategic locations on the radiator tube and at the fluid inlet and outlet were reported. The experiments were conducted at various flow rates of air and the results showed a decrease in goodness factorof 22.3% with respect to increase in Reynolds number from 240 to 455. The experimental results were compared with the CFD results and the f and j factors from the CFD analysis are in good agreement with the experimental data. The comparison of performance of the radiator tubes with different winglet turbulator configurations was carried out and reported. newline