超临界压力下正十烷流动传热的数值模拟

Numerical Simulation on Flow and Heat Transfer of n-Decane Under Supercritical Pressure

关键词:  超临界压力  正十烷  再生冷却  数值模拟 

Key words:  Supercritical pressure  n-decane  Regenerative cooling  Numerical simulation

摘要:

为了深入理解主动再生冷却过程中碳氢燃料的超临界传热特性,基于SIMPLE算法建立了数值模拟方法,考虑了碳氢燃料物性随温度的剧烈变化,并利用电加热管实验结果验证了计算方法。针对超临界压力下细管道内正十烷的流动传热现象进行了系统的数值计算研究,考察了计算网格无关性和超临界流动传热过程中的压力效应。结果表明:网格选择与正十烷的状态有关；在超临界压力下,较低的正十烷压力引起临界温度附近的努赛尔数减小,导致传热效率下降；目前常用的传热经验公式在正十烷临界区域附近与数值计算结果差别较大。 

Abstract:

In order to understand the heat transfer characteristic of hydrocarbon under supercritical pressure in regenerative cooling process, a numerical method was established based on SIMPLE algorithm. The method can model the drastic variations of hydrocarbon thermophysical properties with temperature. The results of an electrically heated tube test were adopted to verify the method. A systemic numerical investigation was then conducted to study the flow and heat transfer phenomena of n-decane under supercritical pressure in a tube. Grid independence and the pressure effects on supercritical flow and heat transfer were analyzed in detail. The results show that the state of n-decane has a great effect on grid selection. Nusselt number decreases with decreasing pressure in the vicinity of critical temperature under supercritical pressure. Thus the efficiency of heat transfer declines. There are obvious differences between the results of empirical expressions and that of numerical prediction due to the drastic variations of thermophysical properties near the critical region. 