Numerical evaluation of the thermal performance of different configurations of soil-air heat exchangers

Abstract The use of soil as an energy source is aimed at reducingenergy consumption in buildings resulting from the use of heating, ventilation, and air conditioning equipment. Due to its high thermal capacity, soil acts as a thermal reservoir, heating or cooling the air inside buildings, depending on the localclimate conditions. In thisstudy, the finite volume method was used to analyse the thermal performance of this type of earth-airheat exchanger (EAHE). Initially, the effects of soil thermal properties, air velocity, and duct diameter on the thermal performance of the EAHE were investigated under steadystate, as it is a limit condition. In addition, two configurations for the duct distribution in the soil (two and four steps) were analysed. The resultsshowed that the best performance for the EAHE was obtained using saturated soil and operating with an air velocity of 2.5 m/s in a duct with a 0.10 m diameter, and that a 0.5 m distance between the duct’s center lines was the most appropriate. In addition, simulations were performed intransient state, applyingclimate conditions through sinusoidal functions.

摘要 以土壤作为能源载体，旨在降低建筑因采暖、通风与空调设备运行产生的能源消耗。土壤凭借较高的热容量可作为热储库，依据当地气候条件对建筑内部空气进行加热或降温。本研究采用有限体积法（finite volume method）对这类土壤-空气换热器（earth-air heat exchanger, EAHE）的热性能展开分析。初始阶段，本研究以稳态作为极限工况，探究了土壤热物性、空气流速以及管道直径对EAHE热性能的影响。此外，还分析了土壤内管道排布的两种构型（2段式与4段式）。研究结果显示，当采用饱和土壤、在管径0.10m的管道中以2.5m/s的空气流速运行时，EAHE可获得最优性能，且管道中心线间距0.5m为最优参数。同时，本研究通过正弦函数引入气候条件，开展了瞬态工况下的模拟仿真。