Soil Source Heat Pump U-pipe Heat Exchanger Heat Transfer

The Ground-Source Heat Pump system makes full use of soil as cold or heat source and boasts the features of protecting the environment and saving energy. GSHP with the adoption of the vertical U-tube heat exchanger has become increasingly popular because of such outstanding advantages as fewer area requirement, fewer limits, more steady and effective performance etc.This paper introduces edaphic characteristics and presents the equations to determine the undisturbed ground temperature based on relevant literature. A transient heat transfer model for the simulation of a single vertical U-tube heat exchanger is built and the controlled equation is dispersed in terms of Finite Volume Method. The temperatures of soil and fluid in U-tube are simulated and simulation results and experiment datum are consistent. The results indicates near the wall of tube well the radial temperature grad is great and far from the wall the grad is little. Along with GSHP running at refrigerate condition the temperatures of the out medium and the wall gradually rise. At the beginning the temperatures of wall of U-tube and soil rise quickly and along with the Heat Pump running the temperatures change tardily until the temperatures are steady. The system will be at steady state. Then, the least space between the well and the adjacent well can be fixed. Analysis of the quantity of heat exchange of unit length tube well having effects on exchanger capability indicates the tube length and the number of well can be reduced if the quantity of heat exchange is increased. But the out medium temperature will be higher and the Heat Pump refrigerate capacity is lower. Appropriate quantity of heat exchange of unit length tube well should be chose according to edaphic characteristics. This paper provides a method to determine the length of vertical U-tube exchanger based on BIN method calculating building load. What's more, this paper researches the mixed Ground Source Heat Pump and proves the mixed system's energy saving is evident by analyzing an example. Analysis above is essential conditions to design the Heat Pump system.