Theoretical study on a ground source heat pump using abandoned frozen pipes as ground heat exchanger

The artificial ground freezing is a special construction technology. It makes the formation water congeal into ice and makes the natural ground turn into frozen soil, which enhance the soil’s strength and stability, and reduce or even cut off the influence of groundwater on the underground engineering. With the protection of frozen wall, the underground engineering construct more secure. But when the project is finished, the frozen tubes are always abandoned in the ground. So we can use these abandoned frozen tubes replace the traditional buried tubes as the heat exchanger of the ground-source heat pump(GSHP), which utilize the heat and chiller from the shallow and deep soil layers. In the project, the calculation of heat transfers of the heat exchange in the GSHP systems, not only relates the feasibility of the system utilizing this energy, but also influences the form and management of the system. And it is also the key factor influencing the operation of the GSHP. So calculating the heat transfer accurately is very important. This paper takes a project as an example, establishes a heat conduction model based on the cylindrical source theory, calculates the summer and winter heat transfer of the frozen pipe heat exchanger. And the results show that the average heat transfer of the frozen pipe is 108 W/m in winter and 72 W/m in summer.