Waste heat recovery system is a system using for preheating fresh air needed in industrial and waste heat plants. The aim of this study is to improve the performance of a heat recovery unit by using a heat exchanger consisting of a heat pipe which uses a (CuO + ZnO)/water hybrid nanofluid as a working fluid. As is known, the nanofluid in the heat pipe is able to evaporate at a temperature lower than the temperature of the base fluid, so the heat recovery unit will also be provided to benefit from the waste heat at lower temperatures. Thus, the temperature range of the heat recovery unit will be increased. The optimum conditions for the evaporation of hybrid nanofluid in the evaporator region of the heat pipe were investigated by performing experiments at different temperatures and flow rates of the waste heat. Similar conditions were made in a cold fluid, and the optimum conditions for condensing the nanofluid in the condenser region were investigated. Experiments were performed at 2 different cold air flows (30 g/s and 60 g/s), 3 different hot air flows (50 g/s, 70 g/s, and 90 g/s) and 2 different heating powers (1000 W and 2000 W). Thus, optimum values of temperature and flow were found at all Re numbers on the hot- and cold-fluid sides, and it was helped to determine the operating temperature ranges of the heat recovery unit. The efficiency improvement rates in the heat pipe were between 14% and 73%. The best result was achieved when the cold-air duct Reynolds number was 6700 and the hot-air duct Reynolds number was 11,250. The use of the hybrid nanofluid at all Re numbers reduced thermal resistance in the heat pipe. The maximum reduction rate in thermal resistance was achieved to be 40.4% compared to pure water when the cold-air duct Reynolds number was 12,400. As a result, the efficiency of the heat tension recovery unit increased.

中文翻译：

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通过使用混合（CuO + ZnO）/水纳米流体来提高包含热管的热回收装置的性能

废热回收系统是用于预热工业和废热工厂所需的新鲜空气的系统。这项研究的目的是通过使用由热管组成的热交换器来提高热回收单元的性能，该热管使用（CuO + ZnO）/水杂化纳米流体作为工作流体。众所周知，热管中的纳米流体能够在比基础流体的温度低的温度下蒸发，因此也将提供热回收单元以受益于较低温度下的废热。因此，将增加热回收单元的温度范围。通过在不同温度和废热流速下进行实验，研究了混合纳米流体在热管蒸发器中蒸发的最佳条件。在冷流体中进行了类似的条件，并研究了在冷凝器区域冷凝纳米​​流体的最佳条件。在2种不同的冷空气流量（30 g / s和60 g / s），3种不同的热空气流量（50 g / s，70 g / s和90 g / s）和2种不同的加热功率（1000）下进行实验W和2000 W）。因此，在热流体侧和冷流体侧的所有Re值处都可以找到最佳的温度和流量值，有助于确定热回收装置的工作温度范围。热管的效率提高率在14％至73％之间。当冷空气管道雷诺数为6700，而热空气管道雷诺数为11,250时，可获得最佳结果。在所有Re数下均使用混合纳米流体会降低热管中的热阻。当冷空气管道的雷诺数为12,400时，与纯水相比，最大的热阻降低率达到40.4％。结果，提高了热张力恢复单元的效率。