Vertical U-tube Performance Analysis Of Ground Source Heat Pump Based On The Different Load Characteristics

With the fact that fuel is becoming scarcer and the environment is becoming worse in the world, our country also appeals energy conservation and emission reduction. The ground coupled heat pump system has drawn public attention to the situation, as a new energy system, therefore the ground coupled heat pump system attracts the vast number of scholars and researchers starting an in-depth study on it. Combined with the examples of specific ground coupled heat pump application, this paper analyzes vertical ground pipe performance about ground coupled heat pump system based on two different load distributions, and this text has carried on the research about long-term performance and economic analysis of the ground coupled heat pump system.Considering the situation of a single U ground pipe and using the heat transfer model inside and outside boreholes the differences of heat transfer situations for two typical kinds of load distributions about U-tube heat exchanger in different climate zones are compared to analyze the heat exchange capacity of the unit well depth, the fluid outlet temperature, wall temperature of the boreholes, and soil temperatures in1m distance from boreholes.Combined with specific engineering example, then the annual hourly load of underground building is calculated. The heat interaction of multi-boreholes is taken into consideration in this thesis to analyze ground heat transfer in multi-boreholes. The tube wells are classified depending on the position. All kinds of U-tube outlet temperature of different wells are analyzed to compare with each other.Then the sensitivity analysis is carried out on the buried tube for the two kinds of different load distribution projects, followed with the detailed analysis and comparison from four factors, including the borehole diameter, borehole depth, backfill material and well spacing. The influence of various aspects on outlet temperature of the ground pipe are compared, it is used to get the effects of various factors on ground source heat pump system.In the last chapter, a study of the long-term operational performance of the system is conducted. At first, the highest temperature of various borehole diameters, drilling depth, fluid mass flow rate, well spacing are discussed. Then three design multi-boreholes are proposed according to the results. Mean COP change trend of solutions in a year can be calculated according to the function of the COP and the ground pipe outlet temperature simulated before. Finally, the text carries economics analysis about different schemes on the source side, compares the cost according to the economic analysis model with long running. Then the design of the optimization is proposed after the comprehensive analysis.