Abstract:

Based on genetic aggregation response surface models and multi-objective genetic algorithms, the effects of key structural parameters and inlet velocities on the shell-side flow and heat transfer of rod-baffle heat exchangers (RBHXs) with twisted oval tubes were investigated. The performance of twisted-oval-tube RBHXs was optimized. The results show that the heat transfer coefficient h decreases by 9.38% firstly and then remains constant with the increase of the pitch and it increases with the ratio of long axis to short axis under lower inlet velocities and decreases firstly and then increases when inlet velocities are higher. When the inlet velocity is 0.1 m/s, the heat transfer coefficient increases by 45.92% with the ratio of long axis to short axis. When the inlet velocity is 0.5 m/s, the heat transfer coefficient decreases by 12.96% firstly and increases by 7.74% then. The pressure drop Δp is constant with the increase of the pitch; the increase with the ratio of the long and short axes is reduced by 36.67%. The sensitivity analysis shows that inlet velocities influence the heat transfer coefficient and pressure drop more than structural parameters and the ratio of long axis to short axis of structural parameters influences output parameters more than the pitch, which provides theoretical guides for structure improvement and inlet velocities selection of RBHE given structure and inlet velocities. Three sets of optimal results were obtained by employing multi-objective genetic algorithms to maximize the heat transfer coefficient and minimize the pressure drop simultaneously on response surfaces. Compared with the original structure, the heat transfer coefficient increases averagely by 19.17%; the pressure drop decreases by an average of 5.74%; the comprehensive performance h/Δp is enhanced by 26.42%.

Key words: rod-baffle heat exchanger, twisted oval tube, numerical simulation, genetic aggregation response surface model, multi-objective genetic algorithm, optimization, turbulent flow

摘要：

基于遗传聚集响应面模型和多目标遗传算法，研究了以螺旋扁管为换热管的折流杆换热器结构参数、入口速度对壳侧流动和换热性能的影响，并对螺旋扁管折流杆换热器的性能进行了优化分析。结果表明：传热系数随螺距的增大先减小9.38%，后维持不变；在低入口速度条件下，随长短轴之比的增大而增大，在高入口速度条件下，存在先减小后增大的趋势。压降随螺距的增大基本不变；随长短轴之比的增大减小了36.67%。由敏感性分析可知传热系数和压降对入口速度的变化最敏感，截面椭圆长短轴之比次之，对螺距最不敏感。优化后的螺旋扁管折流杆换热器结构比原结构单位压降下的传热系数平均提高了26.42%。

关键词: 折流杆换热器, 螺旋扁管, 数值模拟, 遗传聚集响应面模型, 多目标遗传算法, 优化, 湍流