Experimental study on heat transfer characteristics of shallow vertical spiral buried pipe heat exchangers

A prototype-scale experimental platform for a shallow vertical spiral buried pipe heat exchanger is built to conduct experimental studies on the heat transfer characteristics of the spiral buried pipe under the influence of different flow rates in the pipe and rainfall infiltration. Two quantitative evaluation indexes of instantaneous heat transfer coefficient and efficiency coefficient are introduced to reflect the heat transfer characteristics of the spiral buried pipe. The results show that increasing the flow rate in the pipe can improve the heat transfer performance of the spiral buried pipe. However, when the flow rate increases to a certain extent, due to insufficient heat exchange, the improvement effect on the heat transfer performance of the buried pipe will gradually weaken, and the energy consumption of the system pump is also increased.Therefore, it is recommended that the design flow rate of the spiral buried pipe should not be too high on the premise of ensuring turbulent flow. Rainfall infiltration can improve the thermal properties of the soil in the spiral buried pipe area to a certain extent, which is more conducive to heat transfer, and can effectively improve the instantaneous heat transfer coefficient and efficiency coefficient of the spiral buried pipe, thus improving the heat exchange performance of the buried pipe.