Numerical Simulation On Heat Transfer Characteristics Of U-finned Tube Heat Exchanger For GSHP

With the concerns on energy consumption and environmental issues increasingly by people, the ground-source heat pump technology in HVAC field has been applied and studied with its unique advantages, and how to improve the thermal efficiency of heat exchangers has become the focus of research.The paper improved the traditional structure of ground heat exchanger and put forward U-tube ground heat exchanger with interior fins. By applying FLUENT software, in the inlet velocity 0.6 m/s ~ 1.2 m/s range, the heat transfer characteristic of ordinary smooth type and rib chip (respectively within fin-root 4, 6, 8) type ground heat exchange with the same length and diameter is analyzed by three-dimension numerical simulation, and gets the distribution of soil temperature field around three kinds of fins and smooth type ground heat exchanger.The results of the study show that: fins and smooth type ground heat exchanger have the same influence law on the surrounding soil temperature, which was the soil temperature distributed symmetrically along the U-shaped buried tube. And as the distance from the u-shaped buried tube increasing, soil temperature presents attenuation trend,but in the same direction,soil temperature at the point with the same distance from the U-tube for finned tubes was higher than that of the smooth tube. The import and export temperature difference of fins and smooth type ground heat exchanger decreases with the velocity increasing. The import and export temperature difference of fins is about 2～2.2 times about of smooth tube. Average surface heat transfer coefficient, heat transfer and flow resistance of fin-root tube is greater than that of smooth tube, and increases with the inlet velocity increasing. In considering pump power consumption, the thermal efficiency of 4 fin-root tube is highest and about the 1.33 times that of smooth tube, the thermal efficiency of 6 fin-root tube is higher than that of smooth tube in inlet velocity 0.6m/s～1.0m/s range, and the thermal efficiency of 8 fin-root tube is lowest.