过载条件下流动沸腾压降振荡的建模与仿真研究

流动沸腾系统中,压降振荡是系统不稳定性的主要型式之一。过载条件下流动沸腾压降振荡缺乏研究。本文采用数值仿真方法,对过载条件下管内流动沸腾的压降振荡特性进行了研究。建立了不同重力条件下压降振荡计算的数学模型,基于此,对过载条件下R134a在2.168 mm水平管内的压降振荡进行了仿真分析,得出了1.41 g、3.16 g(g=9.8 m/s^2)过载条件下的压降振荡特性及其引起的流量振荡、流体温度振荡和壁温振荡,并与对常重力(1 g)下的压降振荡特性进行了对比。结果表明,随着重力增加,流动特性N曲线的负斜率段缩短;一定条件下,当过载增加时,系统从稳定状态趋于不稳定状态。

Modeling and Simulation of Pressure Drop Oscillation of Flow Boiling under Hypergravity

Pressure drop oscillation is one of the major flow instability in flow boiling systems.So far no literature in the pressure drop oscillation of flow boiling under hypergravity is found to be available.In this paper,the pressure drop oscillation of flow boiling in tubes under hypergravity is investigated numerically.The mathematical model for the pressure drop oscillation of flow boiling in tubes under various gravity levels was developed,based on which the pressure drop oscillations of R134 a flow boiling in a 2.168 mm horizontal tube under 1 g(Earth/s gravity),1.41 g,and 3.16 g(g=9.8 m/s^2)were simulated,including the resultant mass flow oscillations,fluid temperature oscillations,and wall temperature oscillations.The 1 g condition is included for comparison.The results show that the negative slope region of the N-shaped characteristic curves becomes shorter,and that in some conditions the system tends to be unstable from a steady state with increasing gravity.