板翅式换热器封头对其流体分配及换热的影响

Effects of header configurations on flow distribution and heat transfer in plate-fin heat exchangers

实验研究了板翅式换热器封头结构对其内部流体分配及换热特性的影响,实验结果表明,目前工业应用的板翅式换热器内部存在流体分配极为不均匀的严重问题,造成了其换热效能的严重下降。研制了各种新型孔板封头结构,并且实验研究了新型封头的各种参数,如孔板长度、开孔的分布规律和小孔直径对板翅式换热器流体分配及换热的影响。研究结果表明,孔板封头从根本上改善了换热器内部流体的分配问题,流体不均匀度从0.208减小到0.035,最大与最小流速比由改进前的2—3倍降低到1.1—1.2倍,温度分布不均匀度从0.826减小到0.601。孔板型封头结构增加了换热器的流动阻力,错排孔板型封头在改善换热器流体分配的同时,也较好地抑制了阻力损失的增加,得到了不同封头结构的流动阻力与雷诺数之间的关系。

The effects of header configurations on the flow distribution and heat transfer in plate-fin heat exchangers were experimentally studied. The flow maldistribution in heat exchangers is very serious because of the improper header configuration, which results in a significant deterioration of the heat transfer situation. The new header configurations with perforated plate were designed and manufactured. The experimental researches of the influence of the perforated plate length, the distribution of orifice and the orifice diameter on the flow distribution in heat exchangers were performed. It shows that the new header configuration can improve the flow nonuniformity and heat transfer in plate-fin heat exchangers, thus the degree of flow nonuniformity is reduced from 0. 208 to 0. 035, the ratio of maximal flow velocity to minimal flow velocity drops from 2-3 to 1.1-1.2, and the degree of temperature nonuniformity is reduced from 0. 826 to 0. 601. The header configuration with perforated plate increases the resistance loss of heat exchangers and the staggered perforated plate header can improve the flow distribution of heat exchangers and inhibit the increase of resistance loss. The relations of the resistance loss characteristic with Reynolds number are obtained under different header configurations.