Numerical Simulation And Experimental Research Of Soil Temperature Characteristics For Buried Tube

Experimental study and numerical simulation have been carried out to analyze the temperature variation in the soil for the refrigerating and heating word conditions in this thesis. In allusion to the heat imbalance caused by the cooling and heating load, the analysis show that the temperature variation in the soil is one of the key factors that have a significant impact on the system performance. The temperature variation as well as the corresponding reasons was analyzed after the refrigerating and heating word conditions.Based on the soil structure and the distribution of the temperature field, the structure properties including the soil layers for different soils are analyzed, and the thermal conductivity of the layered are determined. In addition, the physical model and the mathematical model are built. The analog computations are carried out with the help of numerical simulation software. The distribution of the temperature field under different working conditions is studied numerically.For the sake of increasing the system performance, a reasonable operational mode is very important. For example, at the earlier stage of refrigerating word conditions, the ground heat exchangers are used as the cold source without heat pump, which can meet the requirements while the cooling load is low. In addition, the temperature variation is small in comparison to the traditional operational mode, and this is because the heap pump does not run reducing a portion of heat release to the soil.The operating characteristics for the next working condition were analyzed according to the soil temperature recovery in the recovery phase after each working condition associated with the soil characteristics. The recovery efficiency was employed to determine the temperature recovery in the soil on the basis of the experimental data. The results showed that the recovery efficiency for the refrigerating word conditions reaches 0.91 being only 26 days after stop running of GSHP system whereas 75 days are needed for the heating word conditions. The factors that affect the recovery efficiency include the temperature difference between the soil near the ground heat exchangers and the soil faraway and the thermal diffusivity of the soil. The soil that does not recover to the initial temperature can be regarded as the energy storage to increase the heat release to the soil for the refrigerating word conditions.