Abstract In this work, the effect of temperature-dependent thermal conductivity ( k ( T )k(T)) and viscosity ( μ ( T )\mu (T)) variation on entropy generation in circular channels with an approach from macro- to micro-scale is numerically investigated. Thermally as well as hydrodynamically fully developed flow of water through the fixed length channels with constant total heat flow rate and total mass flow rate is considered. The effects of k ( T )k(T) variation and μ ( T )\mu (T) variation on entropy generation are analyzed individually as well as collectively. It is observed that in the case of Constant Property Solutions (CPS) S gen , tot {S_{\mathit{gen},\mathit{tot}}} is maximum at the macro-level; however, in the case of combined k ( T )k(T) and μ ( T )\mu (T) variations it is maximum at the micro-level. The Bejan number ( Be\mathit{Be}) and irreversibility distribution ratio (φ) are also calculated for asserting the dominance of frictional irreversibility and conduction heat transfer irreversibility. Additionally, the optimum diameter ( D ∗ {D^{\ast }}) corresponding to the optimum number of channels is calculated at minimum total entropy generation. It is observed that D ∗ {D^{\ast }} is minimum for k ( T )k(T) variation followed by CPS, μ ( T )\mu (T) variation, and combined k ( T )k(T) and μ ( T )\mu (T) variations.

中文翻译：

---

热物理性质变化对微尺度熵产生的影响

摘要 在这项工作中，温度相关的热导率 ( k ( T )k(T)) 和粘度 ( μ ( T )\mu (T)) 变化对圆形通道中熵产生的影响从宏观到微观尺度进行了数值研究。考虑通过具有恒定总热流率和总质量流率的固定长度通道的热学以及流体动力学完全发展的水流。k ( T )k(T) 变化和 μ ( T )\mu (T) 变化对熵生成的影响分别进行了分析和综合分析。观察到，在恒定属性解 (CPS) S gen 的情况下， tot {S_{\mathit{gen},\mathit{tot}}} 在宏观层面是最大值；然而，在组合 k ( T )k(T) 和 μ ( T )\mu (T) 变化的情况下，它在微观层面上是最大的。还计算了 Bejan 数 (Be\mathit{Be}) 和不可逆分布比 (φ) 以断言摩擦不可逆和传导传热不可逆的优势。此外，在最小总熵生成时计算与最佳通道数相对应的最佳直径（ D * {D^{\ast }}）。观察到 D ∗ {D^{\ast }} 是 k ( T )k(T) 变化的最小值，其次是 CPS、μ ( T )\mu (T) 变化和组合 k ( T )k(T ) 和 μ ( T )\mu (T) 变化。