多股流板翅式换热器翅片通道中传热的计算流体力学模拟及定性尺寸

Computational fluid dynamics simulation of heat transfer in channels for multi-stream plate-fin heat exchanger and determination of fin qualitative size

板翅式换热器结构紧凑,传热效率高,常用于多个冷热物流之间的换热,但是其通道数量众多,其内部流道中的流场和温度分布很难用实验方法来测定。采用计算流体动力学(CFD)软件ANSYS,针对锯齿形翅片模拟了板翅式换热器进出口的温度场分布,根据热量平衡和热量传递速率方程,对多股流板翅式换热器的各通道的温度分布进行模拟,并分别计算出各个流股在各个通道的二次传热表面最大传热距离,即通道定性尺寸。分别对两流股和三流股的2个板翅式换热器进行通道温度场分布CFD模拟,从而计算得到板翅式换热器的定性尺寸。对于两流股一冷一热交替排列的通道,数值模拟的定性尺寸与简化的经验方法计算结果都为翅片的一半,而对于三流股八通道的定性尺寸,中间的第四通道和第六通道的翅片定性尺寸大于基于传统计算方法得到的定性尺寸,对应的翅片效率小于传统方法得到的结果。基于板翅式换热器传热机理对结果分析表明,数值模拟结果比文献经验计算方法的结果更合理,即为板翅式换热器的设计提供了准确的基础参数,原因是数值模拟结果考虑了相邻多个通道热流量和温度对通道传热的影响,改进了传统方法仅考虑相邻通道热流量和温度的影响。

The plate-fin heat exchangers have a compact structure, which feature high transfer efficiency and many of the passages, and they are used for heat transfer between several hot and cold streams, while it is difficult to predict the distribution of flow field and temperature in passages by the experiment methods. In this article, the temperature distribution of inlet and outlet of heat exchanger with serrated fins was studied by using a computational fluid dynamics （CFD） code, ANSYS, According to heat balance and the equation of heat transfer rate, the temperature distribution in passages was simulated, and the maximum heat transfer distance was calculated in the second heat transfer surface, which was the determined size of plate-fin heat exchanger. The heat transfer in the passages was simulated by CFD for two streams and three streams of multi-passage heat exchanger, and the fin qualitative size of the plate-fin heat exchanger was obtained. Finally, the determined size obtained by numerical simulation was half of the fin height for the passage with two streams, which was consistent with the result obtained by simplified experience methods, but for the fin qualitative size of three streams and eight passages, they were larger than that obtained by experience method in the fourth and sixth passage, and the corresponding fin efficiency were smaller. The results analysis based on the heat transfer mechanism showed that the results of numerical simulation were more reasonable than that of the experience method in literature, i.e. the accurate design parameters were provided for the design of the plate-fin heat exchanger, as the effect of temperature and heat flow in multiple passages on the heat transfer in the passages was considered by numerical simulation, while the influence of heat flow and temperature in adjacent passage was just considered by the traditional method.