高温下饱和回填材料的换热特性研究

HEAT TRANSFER CHARACTERISTICS OF SATURATED BACKFILL MATURIAL UNDER HINGH TEPERATURE

大饱和度地下区域储能时,回填材料的水热运移对埋管换热器和基体间热传递的作用不容忽视。基于改进理查德方程和Marsily表观热导率,建立高含水率下回填材料(粘土、砂及砂加膨润土)的二维热湿迁移模型,并在室内搭建换热试验平台,获取3种材料的单位换热效率及排、停热工况下温、湿度场分布。结果表明:高含水率密闭系统中的Soret效应相对较弱,可只考虑潜热的纯导热;高饱和度条件下,砂类等低持水性材料传热效果最好。但综合考虑热容能力时,在忽略热损失情况下,粘土的间歇排、取热有利于提高储能系统的有效性,经济性最高;所建数学模型与试验数据吻合度好,高温饱和条件下,水蒸气扩散及蒸发冷凝引起的水热运移可忽略,所建模型适用于大饱和度环境下回填材料的传热分析。

When heat storage under groundwater-rich region, heat and water migration has obvious effect on heat transfer between the backfill and the main body. The two-dimensional thermal-moisture model in high saturation condition was built based on the Richards equation and Marsily＇ s apparent thermal conductivity. Simultaneously, the rate of transfer heat, the distribution of temperature and moisture are not prominent in closed-system with high moisture, and only gained by test. Results indicated that the effect of Soret is conduction of latent heat need to be considered. The low water-holding capacity material such as sand show large heat transfer rate. The way of intermittent discharge is more beneficial to improve the effectiveness of thermal storage system as ignoring heat loss. Considering the specific heat capacity, the economic of heat storage using clay is optimal in three kinds of backfill material. The theoretical value and experiment have well agreement. It illustrates that the model built is suit for the thermal analysis of backfill material at high temperature and moisture.