复杂结构微通道热沉液体强化传热过程的热力学分析

微通道液体流动与传热是一个典型的不可逆过程，有必要减小传递过程中的不可逆损失大小，提高其有效利用程度，属于“质”的范畴。首先，根据热力学第一及第二定律，推导出了熵产率及热能传输系数，指出降低微通道热沉内液体温度梯度净值可以提高热能的有效利用程度；然后，基于前期的研究基础，设计出新型复杂结构微通道热沉，并模拟其三维流动与传热过程，对比分析微通道热沉结构的变化对熵产率及热能传输系数的影响，结果表明降低流体温度梯度的净值可以减少热能不可逆损失的大小，使热沉底面温度更均匀，有利于延长微电子器件的寿命；最后，由强化传热因子、熵产率及热能传输系数的定义指出用强化传热因子来评价微通道的综合传热性能更合理，而应该用熵产率及热能传输系数来评价能量的不可逆大小及利用程度。总之，热力学第一定律为微通道的综合传热性能提供了评价标准，而热力学第二定律指出了影响微通道内部强化传热的本质因素，二者相互联系，为微通道的优化设计提供热力学理论。

Thermodynamic analysis of enhanced heat transfer process in microchannel heat sinks with complex structure

It is a typical irreversible process of flow and heat transfer in the microchannel and it is necessary to reduce the irreversibility to improve effective utilization of energy in the heat transfer process. The entropy generation rate and transport efficiency of thermal energy are derived from the first and second law of thermodynamics, which indicate that the effective utilization of thermal energy increases with the decrease of net temperature gradient of fluid in the micro heat sink. A new micro heat sink with complex structure is proposed and simulated based on the previous study. The effect of structure on entropy generation rate and transport efficiency of thermal energy is also analyzed. The results reflect that the less the net temperature gradient of fluid, the less irreversibility and the more uniform the temperature of bottom in the heat sink. Based on the definitions of thermal enhancement factor, entropy generation rate and transport efficiency of thermal energy, it is reasonable to use thermal enhancement factor to evaluate the comprehensive performance of micro heat sinks, while the other two are used to measure the irreversibility and level of utilization in the heat transfer process. In short, the evaluation criteria is provided by the first law of thermodynamics, while the essence of heat transfer enhancement is indicated by the second law of thermodynamics, giving a complete thermodynamic theory for optimizing micro heat sinks.