印刷电路板式换热器的设计分析

Design Analysis of Printed Circuit Heat Exchanger

为了对基于超临界二氧化碳燃气轮机余热利用循环的印刷电路板式换热器进行性能分析,提出了一种定热负荷下对印刷电路板式换热器的离散分析方法。该方法将印刷电路板式换热器看成由许多子换热单元组成的整体,利用MATLAB建模,并参考了美国国家标准与技术研究院的物性库。通过分析定热负荷下,不同冷热侧流速对印刷电路板式换热器性能的影响。结果表明:二氧化碳在临界点和近临界点附近的比热具有较大的变化。采用分段设计的方法可以避免换热器性能剧烈变化带来的问题。在相同的初始条件下,换热器局部效率随冷流体质量流量的增加而增大,但是平均对数温差随冷流体质量流量的增加而减小。因此,换热性能的提高是以热导率为代价的。为了提高超临界二氧化碳印刷电路板式换热器的性能与安全运行,必须仔细选择设计参数的工作范围。

In order to analyze the performance of printed circuit heat exchanger (PCHE) used in supercritical carbon dioxide cycle on heat recovery of gas turbine, a discrete analysis method for PCHE under constant heat load was proposed. In this method, the PCHE is regarded as a whole composed of many sub- heat exchangers, referring to the physical properties database of the National Institute of Standards and Technology by MATLAB. The differences between cold and hot side under constant heat load were analyzed. The results show that the specific heat of carbon dioxide varies greatly near the critical point. The segmented design method can avoid the problems caused by the changes in the performance of sub-heat exchangers. Under the same initial conditions, the local efficiency of the heat exchanger increases with the increase of cold side mass flow rate, but the mean logarithmic temperature differences decrease with the increase of cold side mass flow rate. Therefore, the improvement of heat transfer performance is at the cost of thermal conductivity. In order to improve the performance and safe operation of supercritical carbon dioxide PCHE, the working range of design parameters must be carefully selected.