含有一般性热转移过程的低耗散型热机的权衡优化研究
摘要: 实际热机在工作过程中必然伴随热转移过程.本文提出了含有一般性热转移过程的低耗散热机模型.利用权衡优化方法对该低耗散热机的性能进行了优化分析,推导出了权衡判据下热机功率和效率表达式.详细讨论了不同热转移过程支配下的热机功率以及效率特征,其结果有助于深入理解实际热机的优化机制.
Trade-off optimization for low-dissipation heat engine with generic heat transfer process
Keywords:
- 低耗散热机 /
- 热转移律 /
- 权衡判据 /
- 热机效率
Abstract: The heat transfer process inevitably occurs in the operation of real heat engine. In this article, a low-dissipation heat engine with generic heat transfer process is proposed based on the low-dissipation Carnot model. The formulas for the power and the efficiency of heat engine with generic heat transfer law are derived, and the low-dissipation heat engine performance is also optimized by the trade-off optimization method, which offers a unified scheme to understand the behaviors of heat engines with generic heat transfer processes. Furthermore, the characteristics of the power as well as the efficiencies for thermal engines with the different heat transfer processes are discussed in detail, and it is found that the power and the efficiency without heat transfer process are independent of heat leak, but are related to contact time, heat dissipation and Carnot efficiency. The power output of heat engine monotonically increases as Carnot efficiency increases, but the large contact time ratio and the large dissipation ratio make it difficult to provide the big power output. When the heat leak is absent andα(β) is fixed, the efficiency of heat engine decreases (increases) with the increase ofβ(α). It is noted that the heat transfer process greatly influences the performance of heat engine, andη?/ηC versusβdisplays the similar properties under three heat transfer laws. It is clearly shown thatη?/ηC versusβshows the transition from the monotonic decrease to monotonic increase with α increasing, but η?/ηC versusα is opposite to the former, and the maximum value ofη?/ηC also shifts rightwards with the increase ofβ. Additionally, the corresponding efficiency of heat engine diminishes significantly as m decreases and n increases. When heat engines are dominated by different heat transfer laws, the curves ofη? versusηC are consistent asηC is relatively large or small, but it is observed that there exist the evident differences among three characteristic curves in the middle regime. The relatively large βor small α will also lead to the reduction of the working regime where heat engine can function normally. Our results are very helpful in understanding the design principle and the optimization mechanism for actual thermal engines and refrigerators.