换热器壳程进出口折流区传热温差损失分析

Temperature difference deviation analysis for baffle flow area at inlet and outlet in shell side of heat exchangers

对管壳式换热器壳程进出口折流区的传热温差作了分析,以换热器热流体与冷流体的出口温度比例α表征换热器的换热深度,探讨了换热器换热深度与长径比的关系。采用流路分析方法,对换热器壳程折流区域的传热性能进行了数学分析,并与纯逆流情况作了对比。结果表明:换热器折流区域的传热温差较逆流区域传热温差的偏离量会随α的改变而产生变化,为避免偏移量过大应控制折流区域面积占总传热面积的比例。α<1时,为使传热温差偏移小于5%应使折流区域面积占总传热面积的比例小于0.6/R1 a,c。揭示了现有换热器结构大型化之后难以实现α<1的原因,并给出一种可以改进传统大型管壳式换热器长径比锐减、换热深度受限的有效结构——壳程多通道结构。

Heat transfer temperature difference deviation analysis for baffle flow area at inlet and outlet in shell side of shell and tube heat exchangers was presented.The ratio of outlet temperature of hot fluid to that of cold one α indicated the degree of heat transfer depth.In order to study the relationship between the ratio of length to diameter and heat transfer depth,the heat transfer performance in baffle flow pattern was mainly compared with that in counter flow pattern in terms of flow distribution analysis.The results show that deviation of heat transfer difference changes as a change of α.And the ratio of baffle flow area to the whole area should be changed for different α in order to control the deviation of heat transfer temperature difference not too much.The ratio of baffle flow area to the whole area of heat exchangers should be smaller than to control deviation of heat transfer temperature difference under 5% when α1.The reasons why traditional large shell and tube heat exchangers can′t achieve α1 were presented.The techniques should be incorporated to further enhance the heat transfer coefficient of heat exchangers and multi-parallel-channel structure in shell side is such an advantageous configuration.