土壤源热泵U型埋管换热器冻结取热过程的模拟研究

Simulation Study on Freezing Heat Extraction of U Buried Pipe Heat Exchanger of Ground-source Heat Pump

本文针对严寒地区地下土壤温度低和供暖负荷大的特点,提出了利用土壤相变来进行取热的方法,建立了土壤源热泵U型埋管换热器周围土壤的二维非稳态传热模型,使用显热容法求解了土壤相变问题。对长春地区的模拟结果表明:系统取热功率为21.82 W/m;运行39 d时埋管出水温度降低到0℃以下;运行80 d以后内、外层埋管出水温度出现差值;采暖期结束时外层埋管周围土壤未发生冻结,当内层埋管半径为0.2 m时,土壤冻结深度达到了8.6 m。

In this paper,basing on the characteristics of low temperature of underground soil and large heating load in extreme cold regions,the heating method by using the phase change of soil was proposed, a two-dimension unsteady state heat transmission model on soils around U buried pipe heat exchangers of GSHP was established, and the soil phase change problem was solved by using sensible heat capacity method. The simulation results of Changchun indicated that the heat extraction power of the system was 21.82 W/m, the outlet water temperature of the buried pipes reduced to below 0 ℃ after the system was operated for 39 d, difference of water outlet temperatures occurred between inner and outer layer buried pipes after the system was operated for 80 d, furthermore, soils around the outer layer buried pipes was not frozen until the heating period ended, while for the inner layer buried pipe with radius of 0.2 m, the frozen depth reached to 8.6 m.