Research On The Influence Exerted By Backfill Materials On The Heat Exchange Capacity Of Buried Pipe

Shallow geothermal energy, as a clean and sustainable energy, is used by the GSHP air condition system. While in the utilization of shallow geothermal energy, the heat transfer characteristics of buried pipe is influenced by many factors, including the flow of the groundwater, the property of the backfill materials, the possibility of phase transition around the buried pipes, and the change of the soil condition..The heat exchange in the backfill material, which between the heat transfer of heat exchange and soil, will influence the heat transfer characteristics of buried pipe and the surrounding medium directly. Therefore, backfill technology is important in the construction of GSHP.In the condition of constant heat flux boundary, a physical heat transfer model has been established in this dissertation to analysis the influence of backfill material property parameters on the heat exchange capacity of buried pipe in short and long term heat transfer process. Thermal conductivity coefficient and volumetric thermal capacity, as influence factors, have been considered.Through theoretical analysis, conclusion can be made that in short-term heat transfer process, the increase of the thermal conductivity coefficient and volumetric thermal capacity can improve the heat exchange capacity of buried pipe; while in long-term heat transfer process, the heat exchange capacity of buried pipe will be enhanced much more by increasing the thermal conductivity coefficient.Then a buried pipe test platform has been established to simulate the shot-term heat transfer process, the power of electrical heating rod is under constant control during the test. The silica sand in different moisture content has been analysised to study its influence on the electrical heating rod and the surrounding backfill material. The theoretical analysis can also be verified through experiment.