中深层地埋管换热器周围岩土热恢复特性

To reveal the heat recovery characteristics of the rock and soil around the deep borehole heat exchanger(DBHE), a numerical heat transfer model is established in this paper, which is solved based on the Finite Difference Method(FDM), and verified by the measured data of the project. On this basis, the annual temperature changes of the rock and soil around the DBHE are analyzed. The main conclusions are as follows: under specific working conditions, the heat influence range of the DBHE on the surrounding rock and soil is limited, and its heat-affected radius is 9.3 m; the heat extraction area of the DBHE is mainly concentrated in the rock and soil at a depth of 1 200~2 000 m; the thermal recovery rate of rock and soil gradually decreases with the increase of recovery time. Based on the thermal recovery rate of two months, the thermal recovery rates of four months, six months and eight months increase by 2.1%, 0.9% and 0.5% respectively, so the soil can basically recover to the initial temperature after 8 months of thermal recovery. When r=0.3 m, the corresponding thermal recovery rates of the buried pipe with depth of 1 200 m, 1 600 m, 1 800 m and 2 000 m are 98.7%, 97.9%, 97.9% and 98.2% respectively. This study can provide a theoretical reference for the design of DBHE.