圆管内氦氙混合气体与超临界二氧化碳换热特性对比分析

Comparative analysis of heat transfer characteristics betweenhelium-xenon mixture and supercritical carbon dioxide in a circular tube

小型化、高紧凑反应堆系统是陆上多用途能源供给的研究重点,直接热-动循环下的能量转换对冷却剂工质选型提出极高要求。为了明确氦氙混合气体、超临界二氧化碳的工质适用性,本文采用数值模拟方法,对二者在圆管内的换热特性进行计算,对比了2种冷却剂的物性,分析了不同加热功率、入口速度、入口温度对冷却剂换热系数的影响,拟合提出了2种冷却剂工质圆管内换热的经验模型。研究结果表明:反应堆在加热功率超过100 kW/m~2、入口流速大于10 m/s下,对流换热系数较大;氦氙混合气体入口温度在1 000~1 200 K、超临界二氧化碳在入口温度550~600 K附近时,对流换热系数存在极大值;在高雷诺数区(Re>10~4),2冷却剂的修正关系式与计算值吻合良好。本文计算能够为新型反应堆开发提供数据及模型基础。

The miniaturization and high compactness of reactor systems are the research focus of multipurpose energy supply on land.However,energy conversion with direct thermal-dynamic cycles poses extremely high requirements for the choice of coolants.In this work,the heat transfer characteristics in a circular tube are calculated by numerical simulation method to compare the physical properties of two coolants and analyze the effects of different heating power,inlet velocity,and inlet temperature on the coolant heat transfer coefficient,thus clarifying the suitability of working fluids for helium-xenon(He-Xe)gas mixtures and supercritical carbon dioxide(S-CO 2).In this paper,an empirical model of heat transfer in a circular tube filled with two coolants is proposed.The results show that the convective heat transfer coefficient is relatively high when the heating power of the reactor exceeds 100 kW/m 2 and the inlet flow rate is greater than 10 m/s.Furthermore,there exists a maximum when the inlet temperature of the helium-xenon mixture is about 1000~1200 K,and the supercritical carbon dioxide is about 550~600 K.Finally,in the high Reynolds number region(Re>104),the D-B type fitting relationship of the two coolants is in good agreement with the calculated values.The calculation in this paper can provide data and model basis for the development of new reactors.