太阳能-U形埋管土壤蓄热特性数值模拟与实验验证

Numerical simulation and experimental validation of energy storage characteristics of solar-U-tube soil

为了探讨利用太阳能-地源热泵系统中现有钻孔U形埋管进行太阳能跨季节性土壤蓄热的可行性及其特性,基于多孔介质传热传质及地下水渗流理论,建立了考虑地下水渗流与热湿迁移影响的准三维U形埋管土壤蓄热的数学模型.基于对模型的数值求解,探讨了间歇蓄热运行模式及地下水渗流对U形埋管土壤蓄热特性的影响,结果显示:间歇蓄热方式有利于土壤温度的恢复,从而可提高蓄热效率;同时,地下水渗流的存在可以强化地下埋管的换热效果,但不利于用埋管作为蓄热装置.实验验证表明,埋管日平均出口温度及日蓄热的计算值与实验值随时间的变化规律一致,其平均相对误差为5.6%.所建模型为U形埋管土壤蓄热及其传热特性的研究提供了理论基础.

In order to discuss the feasibility and characteristics of solar energy storage through the U- tubes of solar-ground source heat pump system, a quasi three-dimensional U-tube soil energy storage model, which considers the effects of the ground water advection and heat-moisture transfer, is developed based on the theory of heat and mass transfer in porous medium and ground water advection. Based on the numerical solution of the model, the effects of the intermittent energy storage mode of U-tube and ground water advection on energy storage characteristics are analyzed. The results indicate that the intermittent energy storage mode helps to resume the temperature of soil around U-tube and thus can improve the energy storage efficiency. At the same time, the existence of ground water advection can intensify heat transfer effect of U-tube, but it is unfavorable to the energy storage using U-tube. The experimental validations show that the calculated values of day-average outlet temperature of U-tube and energy storage amount agree with the corresponding experimental values, and the predicted average relative error is 5.6%. The model provides a theoretical basis for the study of characteristics of U-tube energy storage and heat transfer.