The trend toward higher engine power leads to larger radiators in automobile sector and increased frontal areas, resulting increased fuel consumption. Heat transfer of coolant flow through the automobile radiators is of great importance for the optimization of fuel consumption. Compaq cooling system can be manufactured by introducing nanocoolant with in automobile radiator. In this paper, heat transfer of CNT based nanocoolant has experimentally compared to that of pure water in an automobile radiator. Four different concentrations of nanofluids in the range of 0.15- 1 vol. % have been prepared by the addition of CNT nanoparticles into the water. The test liquid flows through the radiator consisted of vertical tubes with rectangle cross section and air makes a cross flow inside the tube bank with constant speed. The CNT nanocoolants are synthesized by functionalization CNT (FCNT) and surface treatment (SCNT) method. The effects of type of nanofluid, variation in pH and nanoparticle concentration on the Nusselt number are deeply investigated. Results demonstrate that both nanocoolant show enormous change Nusselt number in comparison with water. The results of functionalized CNT nanocoolant with 5.5 pH show better performance than 6.8 and 9 pH nanocoolant. The surface treated CNT nanocoolant show results deterioration in heat transfer performance. Furthermore, increasing the nanoparticle concentration and nanofluid velocity enhances the Nusselt number.
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