Performance Of Rock Heat Exchanger With Three Inlet Pipes And One Outlet Pipe

As a sustainable development technology using renewable energy and protecting environment,ground source heat pump is becoming more popular today when the energy conservation and emission reduction and low carbon economy is advocated. The effect of ground heat exchanger upon ground source heat pump system is very important .Today,how to improve the performance of the ground heat exchanger is a hot research topics in the research field of ground source heat pump.Each thermal resistance of U-shaped buried tube,a fact that the the percentage of thermal resistance in the hole went to 48.48%～58.68% was found,to reduce the thermal resistance in the hole was took as the breakthrough direction,and then to increase the contact area between each object was took as a technology to enhance the heat exchange in hole. The mechanism of heat loss of outlet pipe was analyzed. To make outlet pipe heat-insulated and to reduce the sectional area of outlet pipe was proved to be an effective measure to reduce heat loss.The features of conventional vertical ground heat exchanger was analyzed and summarized, ground heat exchangers with three inlet pipes and one outlet pipe(GHETIOO) was put forward,and it had two kinds layout,which were contrasted , one kind was took as object of study at last.The paper reduced the formula of thermal resistance in hole of GHETIOO, calculated and contrasted the thermal resistances of the there kinds heat exchanger and found that the thermal resistance of GHETIOO was obviously less than single U-shaped and double U-shaped. The theoretical model and numerical model of GHETIOO were established ,and the numerical model were validated and analyzed,the simulation results inosculated experiment perfectly.The experiment table was established,and experiment was make The heat exchanging performances of the three kind heat exchanger were contrasted.The construction technique of ground heat exchanger were summarized in detail.The experiment indicated that:When the flow velocity changed from 0.4m/s to 0.86m/s,it's effect on heat exchanging performance of GHETIOO was small;When it changed to 0.2m/s, The heat exchanging performance changed strikingly.The heat exchanging performance of GHETIOO was better than DU and SU.In this experiment , relative to SU and DU,the unit depth heat ex-change of GHETIOO risen by 25.01% and 9.12% respectly.The stop automatic was very useful to improve heat exchanging performances.Under proper load ,the ground heat exchanger could operate energy-savingly for long time.The effect of main fators upon GHETIOO was simulated ,and the result indicated that :When the depth of hole increased from 40m to 100m, the unit depth heat ex-change varied little,the total heat ex-change increased strikingly.To enlarge the distance between pipes could improve the heat exchanging performance.When the thermal conductivity of pipe wall was less than 0.45 W/(m.k),to enlarge the thermal conductivity could improve the heat exchanging performance. When the thermal conductivity of pipe wall was greater than 0.45 W/(m.k),to enlarge the thermal conductivity could not improve the heat exchanging performance strikingly.The effects of the pipe diameter of bured pipes upon heat exchanging performance was small,to enlarge pipe diameter could not improve heat exchanging performance strikingly.