Abstract

Appropriate arrangement of the fin structures in the evaporator and condenser not only enhances the heat transfer coefficient but also suppresses the increase of pressure drop. Due to this reason, a new method of using large-scale pin fins is explored to increase the heat transfer area and to modify the liquid film flow characteristics in the enhanced tubes. In the present study, four enhanced tubes and one plain tube were manufactured by selective laser melting. The working fluid is R407C and the enhanced tubes are eight short pin fins tube, five long pin fins tube, twisted pin fins tube and a tube filled with metallic foam. The results show that the shorter fin tube has the largest heat transfer coefficient for condensation at 3967 W/m²⋅K and the metallic foam tube demonstrates the largest heat transfer coefficient for boiling at 10606 W/m²⋅K. However, the shorter fins have the highest efficiency indices based on the heat transfer coefficient-pressure drop evaluation criterion and the heat transfer coefficient-area evaluation criterion. For condensation, the indices are 1.28 and 1.35, respectively. For boiling, the indices are 2.55 and 1.62, respectively.

摘要

在蒸发器和冷凝器中适当布置翅片结构，不仅提高了传热系数，而且抑制了压降的增加。由于这个原因，探索了一种使用大型针翅片的新方法，以增加传热面积并改变增强管中的液膜流动特性。在本研究中，通过选择性激光熔化制造了 4 根增强管和 1 根普通管。工作流体为R407C，增强管为8个短针翅片管、5个长针翅片管、双绞针翅片管和一根填充金属泡沫的管子。结果表明，较短的翅片管具有最大的冷凝传热系数，为 3967 W/m ^{2⋅K 和金属泡沫管在 10606 W/m 2} ⋅K处表现出最大的沸腾传热系数。然而，基于传热系数-压降评价标准和传热系数-面积评价标准，较短的翅片具有最高的效率指标。对于冷凝，指数分别为 1.28 和 1.35。对于沸腾，指数分别为 2.55 和 1.62。