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چکیده
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Heat transfer enhancement of thermal systems is most important problem in many industrial applications owing to the lack of energy sources. With the development of heat engines, heat pumps and similar devices, the requirement for better heat transfer has become increasingly important. Among all the prominent qualified pathways that have been brought up today, application of microchannel heat exchangers, nanoparticles and nano-fluids and phase change micro-capsulated materials have been further studied and given the most attention today. The development and use of nanofluids, have found a wide range of applications in consumer products, nanomedicine, energy conversion, and microsystem cooling. Of special interest is the use of nanofluid flow for enhanced convection heat transfer to achieve rapid cooling of high heat-flux devices. However, for proper optimization of such thermal engineering systems in terms of design and operation, not only the heat transfer has to be maximized but the entropy generation has to be minimized as well.In this work, the application of nano fluids and its effect on heat transfer enhencment and entropy generation are specifically discussed. nanofluids are prepared using a two-step method in an aqueous solution.
The results are reported of experiments on convective heat transfer and entropy generation behavior of TiO2, Al2O3, hyb1(0.25Al2O3 0.75 TiO2) and hyb2 (0.75Al2O3 0.25 TiO2) as hybrid nanofluid, nanofluids undergoing laminar flowing in a circular tube.
The result indicated that, compare to the base fluid, the heat transfer coefficient of the Al2O3 and TiO2 is increasd by 23.27% and 28.027% respectively. And for the hybrid nanofluids, hyb1 and hyb2 the enhencment increased by 34.053% and 27.1% respectively. The total entropy generation of the system is decresed to47.04% when the hyb1 nanofluid used. In addition, the overall performance of the tested nanofluids are assessed based on the performance index and optimum work conditions, dem
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