Study On Heat Transfer Characteristics Of Phase Change Material Backfilling Ground Source Heat Pump

With the rapid development of world economy, energy consumption has increased. The energy issue has become a prominent problem for the sustainable development of the world. China GDP has obtained rapid growth, however, the unreasonable economic structure caused China as the world’s second largest energy consumer. Ground source heat pump as a clean energy technology, began to flourish in China, and the ground source heat pump technology to carry out a lot of research. The effect of heat transfer performance of the backfill material heat exchanger on the ground is very important. Phase change material as backfill material has certain advantages in theory that can improve the single drilling heat capacity, and reduce the thermal effect of radius. This feature can reduce the drilling distance of objective.This paper analysis the phase transition of single U-tube’s heat transfer characteristics of ground heat exchanger through the FLUENT software. By setting up a3-D unsteady heat transfer model for ground heat exchanger, phase change material and common backfill material is analyzed by comparative study to obtain heat transfer characteristics of the backfill filled with phase change material. Results showed that phase change material can reduce the heat short circuit of U-tube effectively and heat transfer will increases with the increase of velocity. In the same conditions, flow rate has little effect on thermal influencing radius. Analysis of U-tube temperature distribution and the radius of influence, results show that the phase change material as backfill can effectively reduce the heat influencing radius by compared with ordinary backfill soil. Studying on intermittent operation condition at10:14, phase change material can get close to the initial state that can improves the heat exchange at initial operation.To sum up, phase change material has certain advantages over ordinary solid. Phase change material can be considering as backfill material in lack of land which can improve single drilling heat capacity. Phase change material suitable for intermittent operation mode that can quickly return to the initial state.