立式螺旋折流板冷凝器内制冷剂流型和换热特性的数值模拟

摘要

通过数值模拟对比研究单、双头变角度三分螺旋折流板与变间距弓形折流板立式冷凝器的凝结换热性能。建立了设有挡液堰和疏液缺口的三分螺旋折流板立式冷凝器和弓形折流板立式冷凝器的模型，利用Fluent软件的混合模型模拟了蒸汽在上述不同立式冷凝器内的速度、压力及凝结液的分布情况。模拟结果表明，双头变角度三分螺旋折流板立式冷凝器能够有效提高凝结换热系数，其平均换热系数可比弓形折流板方案提高35.7%，且挡液堰与疏液缺口能够有效排液，防止凝结液被蒸汽流夹带，克服了传统立式冷凝器的水平弓形折流板不能有效疏液的局限。%The condensation heat transfer characteristics of the vertical condensers with variable angled trisection helical baffles with single or double thread and with a variable spanned segmental baffle were numerically studied and compared. The physical models of the trisection helical baffle condensers and the segmental baffle one were developed. The distributions of the velocity and pressure of vapor and the volumes of fraction of condensate in these heat exchangers were simulated with the mixing module of Fluent software. The simulation results show that, the variable angled trisection helical baffle vertical condenser with double-threads could significantly improve the condensation heat transfer coefficient, and the average shell-side heat transfer coefficient of the vertical condenser with dual-thread variable angled trisection helical baffles is 35.7%higher than that of the variable spanned segmental baffled one. The liquid dam plus drainage gaps on each inclined baffle plate could drain condensate effectively and prevent liquid film entrainment into vapor, thus it overcomes the limitation of the conventional vertical condensers which could not drain condensate effectively with horizontal segmental baffles.