Numerical Method And Application Of The Integrated Analysis On Thermal Engineering With Earth Energy Use System

In the practical engineering design and the analysis of function prediction, it is usually necessary to find a perfect analytic method for the thermal process of earth energy use which is a complex integrated process of dynamic change and multi-thermal system. Numerical simulation, as an effective integrated analytic method for multi-system coupling, is attracting more and more attention and being developed and used all the time. The earth energy use is an organic inter-correlated process between use and transformation system of over ground energy and the source end of underground energy supply systems. It is able to set boundary conditions of underground source end, based on the dynamic demand and transformation of over ground system. And then, the heat flowing characteristics and effect of the transmission process of the underground energy flow are analyzed, through the mathematic realization of multi-system coupling correlation. The thermal and energetic properties of each system are analyzed simultaneously.In this study, the one-dimensional and three-dimensional integrated analytic numerical method for the use of the earth energy which focuses on groundwater is presented, combined with research by the National Natural Science Foundation of C hina. one-dimensional correlation of each system of earth energy use and three-dimensional characterization for underground thermal energy transfer process are accomplished. The control of whole process numerical calculation and the upper management of value tra nsfer are realized one-dimensionally. System-wide integration analytic method of earth energy use is established. In addition, take practical engineering for example, based on the calculation and analysis on the elements, such as design program, operation mode and working condition of earth energy(mostly underground wafer energy) use, a method and its application system are built to provide the theoretical analysis for the engineering application.For earth energy utilization system, this research for the first time proposed one-dimensional and three-dimensional integrated analytic numerical calculation method to realize integrated analysis for the complex processes of multiple thermal system. This calculation realized one-dimensional and three-dimensional combined calculation, as well as numerical calculation control for single program, and the experimental verification of t model and algorithm was carried out. According to the application example t his research analyzes on how cooling period time varying mode of underground water source energy utilization system, flux and temperature control mode and drawing-pouring well flux dispatch mode affect the function parameters of the system. The research deeply delved into the basic characteristics and properties of the process. In areas where the heating load is dominant, the longer the cooling period is, the smaller the magnitude of pumping temperature declining is, the larger the COP value of cooling units in winter and EER value of the system are. the magnitude of the declining pumping temperature is quicker when using regulation mode of fixed temperature gap and variable flux,and also energy consumption is low in the operation period,and EER value of system is higher. O n contrast, regulation mode of variable temperature gap and fixed flux is more favorable for long-term stable running of the system because of the lowering of the temperature gap between the drawing and pouring wafer. Additionally, the greater the drawing-pouring well flux allocation difference is, the higher the COP value of cooling units and EER value of system is. When the drawing-pouring well flux allocation mode is identical, the COP value of drawing-pouring well flux allocation equivalence mode is higher than the drawing-pouring well flux cross allocation mode.For the geothermal energy utilization process of existing groundwater flow, usually the heat pump units COP of countercurrent mode is highest and the heat pump units COP of downstream mode is lowest. Among of them, the larger downstream flow rate is, the stronger the degree of thermal breakthrough is, for the mode that the pumping wells flow is equal to corresponding injecting wells, the larger the difference of flow distribution is, the more favorable the long-term stable operation system is; for cross-flow, the greater the flow velocity is, the more stable the operating system remains, the smaller the proportion of the upriver pumping well and injecting well flow is, the higher t he system whole pumping temperature is, the higher the unit COP(EER) and system energy efficiency ratio is, the more stable underground aquifer temperature is.In the technology analysis of active underground energy storage and inverting wells, we can further learn that in heat load dominated regions the inverted wells mode can weaken the heat breakthrough, the unit COP(EER) and system energy efficiency ratio is higher than the fixed well mode, these findings indicate that the inverted wells mode is effective; the active storage mode can improve unit COP(EER) and system energy efficiency ratio due to its certain energy supplement, generally, the energy storage effect is more obvious during the spring. For the inverted wells and energy storage coexistence mode, their combined effect is more obvious which prevent the heat breakthrough jointly, so pumping water temperature rises in the heating season and remains fairly low in cooling season, the unit COP(EER) and system energy efficiency ratio are higher.The paper further analyzes the dual source spatial arrangement and its influence of energy supply share in the process of the energy utilization of groundwater and soil. The hole group positioning bias of the underground heat exchanger will effectively slow the pumping temperature dropping and increase the heat spatial coverage. O n the contrary, the horizontal arrangement in vertical middle region lacks this advantage. The studies have shown that the energy supply share between the groundwater source and the soil has obvious influence of water temperature. The loading change of underground soil source heat exchanger will significantly lead to the change of groundwater pumping temperature, thus affect the unit COP(EER) and system efficiency of energy utilization.