梅花孔板纵向流换热器壳程流动与传热的三维数值模拟

基于梅花孔板纵向流换热器的三维物理模型，采用RNG k-e湍流模型，对其壳程流动与传热特性进行了数值模拟，以空气为工作介质，考察了孔板开孔率y=0.148, 0.18和0.214的换热器在雷诺数Re=4000~12000范围内的传热和压降. 结果表明，流体流过梅花孔后产生贴壁射流，射流的卷吸和二次流作用有利于流体的混合与传热. 换热器壳程平均努塞尔数Nu和单位长度压降Dp/lz均随开孔率y和折流板间距L减小而增大；与相同条件下弓形折流板换热器相比，在研究范围内，该流换热器的Nu提高了14.9%~52.88%，Dp增减幅度为152.85%~-16.62%，综合性能系数PEC为1.03~1.44，适当增大开孔率y和孔板间距L可提高换热器的综合传热性能.

Three-dimensional Numerical Simulation of Fluid Flow and Heat Transfer in the Shell Side of Quincunx Orifice Baffle Longitudinal Flow Type Heat Exchanger

Based on the 3-dimensional physical model of quincunx orifice baffle longitudinal flow type heat exchanger, numerical simulation was performed to study fluid flow and heat transfer in the shell side. The RNG k-e turbulent model was adopted. Air was taken as working medium. And the effects of quincunx hole opening ratio on the baffle y at 0.148, 0.18 and 0.214 respectively and Reynolds number in the range from 4000 to 12000 on the heat transfer and pressure drop of exchanger were examined. The numerical simulation results indicate that wall jets will form when fluid flows through the quincunx holes, thus the degree of fluid mixing and heat transfer will be enhanced under the action of jet entrainment and secondary flow. Mean Nusselt number of shell side Nu and flow resistance per unit shell length Δp/lz will increase with the decrease of y and L. Compared with a single segmental baffle heat exchanger under the same conditions, Nu value of the quincunx orifice baffle exchanger is increased 14.9%~52.88%, the corresponding variance ratio of Dp ranges from 152.85% to -16.62% and the comprehensive coefficients PEC between 1.03 and 1.44 in the research scope. The comprehensive heat transfer performance can be improved by increasing y or L properly.