In this research, entropic analysis of a double helical tube heat exchanger including circular depressions on both inner tube and outer tube is provided. Experimentally validated 3D numerical simulation is employed to reach the aim of this study. Entropic characteristics of four cases are investigated and reported. In case “a” both inner tube and outer tube are smooth. In case “b”, circular depressions are created on only inner tube while in case “c” both tubes contain circular depression. Case “d” is the same as case “c” while the depression arrangement is different from case “c”. Dimensionless entropy generation and dimensionless Nu number are used to evaluate the proposed designs based on the first and second laws of thermodynamics. Moreover, heat transfer improvement (HTI) factor is adopted to consider the impacts of said two parameters simultaneously. Results demonstrate that, although creating circular depressions on both tubes significantly improves the heat transfer characteristics of the heat exchanger, it increases the entropy generation level of heat exchanger as well. Case “d” in which the location of any circular depression of the outer tube is placed between any two continuous depressions of the inner tube, gives the highest thermal performance and also entropy generation.

在这项研究中，对双螺旋管式换热器的熵分析进行了分析，在内管和外管上均包括圆形凹陷。经过实验验证的3D数值模拟可达到本研究的目的。调查并报道了四种情况的熵特征。在“ a”的情况下，内管和外管都是光滑的。在情况“ b”中，仅在内管上形成圆形凹陷，而在情况“ c”中，两个管都包含圆形凹陷。情况“ d”与情况“ c”相同，而凹陷布置与情况“ c”不同。无量纲熵产生和无量纲Nu基于热力学的第一定律和第二定律，使用数字来评估建议的设计。此外，采用传热改善（HTI）因子来同时考虑所述两个参数的影响。结果表明，尽管在两个管子上都形成圆形凹陷可以显着改善热交换器的传热特性，但它也增加了热交换器的熵产生水平。在外管的任何圆形凹陷的位置位于内管的任何两个连续凹陷之间的情况“ d”中，具有最高的热性能并产生了熵。