Research on Heat Transfer Characteristic of Vertical Ground Heat Exchangers in Ground Source Heat Pump Systems
|School||Huazhong University of Science and Technology|
|Course||Heating,Gas Supply, Ventilation and Air Conditioning Engineering|
|Keywords||Ground source heat pump Ground heat exchanger Heat transfer characteristics Energy efficiency coefficient The heat exchangers utility time Experimental test Multipole theory of heat transfer model|
Ground source heat pump system using buried in the underground heat exchanger and soil heat exchange to enhance the taste of the shallow geothermal renewable energy, the new technology of the 21st century is one of the most promising air conditioning. Many factors restricting the development of ground source heat pump technology, which ground heat exchanger heat transfer has been one of the key technology. Pipe heat transfer process characteristics do not know the full, blind design pipe structure and size of the ground heat exchanger performance will lead to a serious decline, increased the energy consumption of the air conditioning system, or even completely paralyzed, bound to bring new technologies to promote The great obstacle. Firstly, to proceed from the heat transfer process closely associated with the ground heat soil characteristics and the need for soil waste heat or take heat ground heat exchanger load characteristics, analyzes the soil thermal properties, groundwater flow characteristics as well as different areas, different construction heat exchanger load distribution characteristics and laws, a description of the ground heat transfer in the soil two principal mechanisms and characterization of the heat exchanger load three important characteristics. These characteristics directly determine the long-term ground heat exchanger performance heat exchanger to maintain the good state of the heat exchanger, also decided to keep the sustainability of many years of operation of ground source heat pump system. By theoretical analysis, this paper two heat transfer mechanisms to the fields of mathematical physics model ground heat exchanger heat transfer process, by means of the boundary conditions and initialization conditions embodied a pipe dynamic heat load characteristics. The entire field of discrete finite volume method for solving domain whole field solver. Concern basis for the design and operation of ground source heat pump inlet and outlet temperature and the heat exchanger sustainability, the introduction of ground heat exchanger, the energy efficiency coefficient and heat transfer utility time parameters, on the ground heat exchanger energy efficiency characteristics and the maximum available temperature difference can be The continuing heat exchangers time quantification analysis. Infinity boundary values ??on the optimized ground heat exchanger heat transfer process dynamic numerical simulation analysis of whether the groundwater seepage soil pipe heat exchanger performance differences, and discuss a variety of ground heat The structure and size, state of the soil thermal stratification characteristics, heat exchanger load characteristics and operation mode conditions Shimoji heat the heat transfer characteristics and the effectiveness of the time variation, and a section of heat transfer theory and its dynamic migration characteristics for soil stratification characteristics The ground heat match the optimal design of the heat exchanger and the air conditioning system parameters to provide theoretical and technical support. The base field experiment platform Pipe Heat Exchanger model to establish the ground heat created by the use of field experimental tests validate the mathematical model of the heat exchanger and its correctness and reliability of the process, and from the perspective of experimental verification and analysis of the inlet fluid temperature, flow rate, and run the way the field of soil temperature and ground heat exchanger, heat transfer characteristics of the role of law, reserves provide the basic data for the ground source heat pump engineering practice. View of the ground surrounding soil temperature simulation and measured values, in buried pipe circulating fluid and the heat transfer process of the surrounding soil, the soil temperature in the axial direction changed little, and thus can be used two-dimensional heat transfer model analysis of drilling outside soil heat transfer. Based on this, this paper pipe heat transfer theoretical model of a multi-polar and thermal resistance network balance principle to establish a vertical U-shaped pipe heat transfer analytical model. The model will be buried drilling inside and outside with the surrounding soil heat transfer area is divided into two parts, drilling for steady-state heat transfer using the U-tube model of the multi-polar theory, drilling outside the column heat source model for the transient heat transfer, and considered ground heat within the circulating medium axial change. Under certain heat exchanger time by using the model to the analysis of ground heat transfer characteristics, with high reliability and less computational effort. In this thesis, the research will allow pipe heat exchanger design and engineering practice to rationalize energy use technology to provide a theoretical basis and support for the promotion and development of ground source heat pump, shallow geothermal great potential of energy-saving and environmental protection.