临界热流的数值模拟

Numerical simulation of critical heat flux

建立了以加热板为计算域的核沸腾瞬态数值模型,以沸腾表面局部换热为边界条件,对多种工质在不同压力条件下的控制方程、边界条件和计算过程进行了量纲1化处理,并考虑了由核心随机分布产生的气泡重叠效应.数值研究包括模拟整个核沸腾曲线和临界热流(CHF).研究结果表明平均瞬态活化核心间距和气泡覆盖率可以作为沸腾到达CHF的判据.数值模拟的CHF与表面粗糙度无关,而与饱和压力有关,这与Kutateladze和Zuber等的关系式的结果相符合.

A 3-D transient numerical simulation model was proposed for nucleate pool boiling. This model addressed the 3-D transient conduction heat transfer process within the domain of the heating wall, and the effect of bubble overlapping was represented by the boundary conditions. The control equation, boundary conditions and simulation process were dimensionless for different liquid and pressure conditions. The whole nucleate pool boiling curve from low to high heat flux, and the critical heat flux （CHF） were simulated. The simulation results showed that the CHF was not affected by surface roughness. The average area ratio ΓAb covered by bubbles and transient dimensionless distance l4^＋ between nucleate sites were the criteria of pool boiling culminating in the CHF for different conditions. The results of CHF dependence on the saturate pressure simulated by numerical model were in agreement with those predicted by the Kutateladze and Zuber functions.