EXPERIMENT INVESTIGATION ABOUT ENHANCED HEAT TRANSFER OF UNDERGROUND HEAT EXCHANGER IN GROUND SOURCE HEAT PUMP

摘要

Underground shallow part is a giant resource of renewable energy that absorbs solar energy, and also a available energy storage body in the heating or cooling process in the Ground Source Heat Pump (GSHP) system. So GSHP are recognized to be an outstanding heating and cooling system to use the earth energy and save large energy. This paper describes the efforts undertaken recently to explore heat transfer enhancement of ground heat exchangers, in vertical boreholes (100m, 200m depth) of closed-loop GSHP in a testing field. New measures to enhance heat transfer with a screw core tube bundle in the ground heat exchangers is presented. It may disturb the flow and increase the heat transfer surface of underground pipe. Experiment data show that the absorbing heat capacity of the unit depth is about 75～100W/m in a hole, 200m depth and 100mm diameter, and the releasing heat capacity is about 240～280W/m in another hole, 100m depth and 150mm diameter. This kind of canular flow has increased the efficiency of heat transfer and makes better use of earth energy.