超临界压力下竖直蛇形管内RP-3燃料换热特性数值研究

Numerical Research on Heat Transfer Characteristics of Supercritical-Pressure RP-3 Fuel in a Vertical Serpentine Tube

关键词:  蛇形管  超临界压力  RP-3燃料  传热  离心力

Key words:  Serpentine tube  Supercritical pressure  RP-3 fuel  Heat transfer  Centrifugal force

摘要:

针对空-油换热器的结构优化问题，对竖直蛇形管内超临界压力RP-3航空煤油的换热特性开展了数值研究。探究了运行压力、进口温度、质量流速、热流密度对换热的影响，通过管截面流体温度、二次流、湍动能、局部质量流速分布情况阐述了周向非均匀换热机理，讨论了不同运行工况下离心力参数和迪恩数沿流动方向的变化情况，提出了竖直蛇形管换热关联式。结果表明：离心力致使管截面出现两对迪恩涡，强烈扰流作用是强化换热的原因。湍动能和局部质量流速异常分布导致周向不均匀的换热特征。离心力参数阶跃到峰值后周期性波动，迪恩涡沿流动方向先增强后减弱。提高质量流速和运行压力、降低热流密度和进口温度，均弱化离心力作用。修正后的关联式预测偏差处于±20%范围内。

Abstract:

Based on the structural optimization of air-kerosene heat exchanger， a numerical study on heat transfer characteristics of supercritical-pressure RP-3 aviation kerosene in a vertical serpentine tube was conducted. Effects of the operational pressure， inlet temperature， mass flux， and heat flux on heat transfer were investigated. The mechanism of circumferential non-uniform heat transfer was explained by the fluid temperature， secondary flow， turbulent kinetic energy， and local mass flux distributions in tube cross-sections. The variations of centrifugal-force parameter and Dean number along the flow direction under different operating conditions were analyzed. The heat transfer correlation for vertical serpentine tube was proposed. Results indicate that the centrifugal force leads to two pairs of Dean vortices in the tube cross-section， and the strong turbulent-flow effect is the reason for enhanced heat transfer. The abnormal distributions of turbulent kinetic energy and local mass flux lead to the uneven heat transfer characteristics in the circumferential direction. The centrifugal-force parameter first steps to the peak and then fluctuates periodically， while the Dean vortex first strengthens and then weakens along the flow direction. Increasing the mass flux and operational pressure， reducing the heat flux and inlet temperature， could weaken the effect of centrifugal force. The prediction bias of modified correlation is in the range of ±20%.