矩形回路内超临界水稳态自然循环特性数值分析

Numerical Simulations on Steady State Behavior of Supercritical Water Natural Circulation in a Rectangular Loop

采用计算流体力学(CFD)方法对简单矩形回路内的稳态自然循环进行数值模拟研究,并对超临界条件下的重力压降计算方法进行评估分析。结果表明,稳态自然循环流量随加热功率的变化,加热段出口流体温度在拟临界点附近时出现最大值,该最大值随加热段入口流体温度的增加而减小;加热段的温度整体上升并向拟临界区移动时,加热段进出口间的密度差、速度差趋于增加,而压降趋于减小。重力压降计算方法评估表明,Ornatskiy与Razumovskiy所推荐的公式在计算较长管道(2 m)内重力压降时结果偏小,最大偏差接近-30%,辛普森公式可以较好地计算较长管道内的重力压降,可用于处理实验数据。

Numerical simulations on steady state behavior of supercritical water natural circulation in a rectangular loop were carried out. Different expressions of gravitational pressure drop were evaluated. The calculation results indicated that with the heat load variation, the mass flow rate of the steady-state natural circulation obtains a maximum value when the heater outlet temperature is near the pseudo-critical temperature, and the maximum value decreases with an increase in heater inlet temperature. The density difference and velocity difference between the heater inlet and outlet increase when the temperature of the whole heater moves towards the pseudo-critical area, while the pressure drop decreases in this condition. The evaluation of the gravitational pressure drop expressions indicated that when the expression proposed by Omatskiy and Razumovskiy was used to calculate the gravitational pressure drop in a relatively long tube （2 meters）, the results were lower than those obtained from integral method which could be considered to be the real gravitational pressure drop, and the maximum error was near 30 percent. On the basis of Simpson integral method, a new method was proposed to calculate the gravitational pressure drop. The new method showed more satisfactory and could be adopted in experimental data analysis.