套管双壳程对螺旋折流板换热器传热和阻力特性的影响

Effect of Casing Double-Shell on Heat Transfer and Flow Resistance of Spiral Baffle Heat Exchanger:A Simulation Study

利用数值模拟法,通过改变套管双壳程内壳直径探究螺旋折流板换热器传热和阻力特性,获得其(壳侧外直径为250 mm系列的换热器)局部压力、温度及流场分布,同时分析不同内壳程管径对螺旋折流板换热器性能的影响。结果表明:合理的管径设置可以让换热器壳侧总压降最大降低比率达53.2%~55.4%,壳侧传热系数最大提升至4.32%~10.7%,内壳直径为108 mm时换热器的综合性能最好;内壳直径低于某一值(约95 mm)时,壳侧压降增长剧烈,而高于该值时,随着管径的增大,压降波动相对平缓,管径过大或过小均会弱化换热能力;套管双壳程结构虽然能有效改善螺旋折流板换热器性能,但是其管径的设置会舍弃掉部分换热管束,换热管束数量牺牲过多时,限制了换热能力的上限,即最优的管径布置也弥补不了它的换热缺陷。

The flow-field,in the casing double-shell of spiral baffle heat exchanger,was reasonably approximated,mathematically formulated with Realizable k-εTurbulence model,theoretically analyzed and numerically simulated with Fluent software.The influence of the inner-shell diameter on the distributions of pressure/velocity/temperature of flowing water and performance of the heat exchanger was investigated.The simulated results show that the inner-shell diameter has a major impact.To be specific,the optimized diameter of 108 mm is capable of reducing the total pressure-drop by 53.2%~55.4%,and increasing the heat-transfer coefficient by 4.32%~10.7%on the shell wall.However,a small diameter,<95 mm,rapidly increases the pressure-drop,and a large diameter,>120 mm,considerably decreases the heat-exchange efficiency.The simulated and measured results were in good agreement.An obvious limitation of casing double-shell scheme is that removal of a cylindrical bundle of tube surround the inner-shell significantly decreases the heat-exchange capacity.