Zukauskas关系式用于微细管式预冷器适用性的评价与分析

为研究Zukauskas关联式在计算微细换热管束管外换热特性上的适用性，本文利用数值分析方法，在分析空气横掠微细管束换热特性基础上，发现空气横掠管束入口几排换热管的换热尤为强烈，温降过程沿着流动方向呈现由急变缓的特点，剧烈的温度变化造成Zukauskas关联式按照一般均物性方法计算时，计算结果偏高27%以上；对比分析可知，过于剧烈的温度变化使基于换热管束整体给出的对数平均温差作为平均换热温差的处理方法不再适用；根据空气温度变化的特点，按照流动方向将换热区域分成若干部分，再分别利用Zukauskas关联式计算，预测精度得到了极大改善，当换热区域划分成12部分时，平均计算偏差降为了5.8%，鉴于此，在计算骤冷条件下气体横掠管束换热特性时，建议采用适当的分区方法进行计算。

Evaluation and Analysis of Applicability of Zukauskas Correlation to Microtubular Pre-Cooler

In order to investigate the applicability of Zukauskas correlation in heat transfer characteristics calculation about shell-side of slim tube bundle, numerical simulation was employed to obtain the heat transfer characteristics outside of the tube bundle in this paper. It showed very strong heat transfer around the first few rows of the tube bundle, where the air temperature experienced rapid decrease, afterwards, the reduction became slow. And because of this, a prediction about 27% higher than that of the simulation results was resulted by Zukauskas correlation on the basis of conventional average physical properties. A comparison shows that it is no longer suitable of logarithmic mean temperature difference taking heat exchanger tube bundle as a whole under a large change of temperature. Considering the dramatic change of air temperature, the heat transfer region was segmented along the flow direction, heat transfer in each segments was predicted by Zukauskas correlation respectively, by which the prediction accuracy was greatly improved, and when the heat region was divided into 12 parts, the average deviation was reduced to around 5.8%. In view of this, it is suggested to segment the heat exchange area outside a tube bundle for predicting the heat transfer characteristics by Zukauskas correlation under the condition of sudden cooling.