The Study On The Operating Characteristics And Operation Optimization Of Surface Water Heat Pump Systems

Developing renewable energy is necessary to energy structure optimization and environmental protection of China. As a renewable energy technology, ground-source heat pumps which include ground-coupled heat pumps, groundwater heat pumps and surface water heat pumps (SWHPs) can utilize diffused low-grade energy over shallow water and soil. Some ground-coupled heat pump systems and groundwater heat pump systems have been built in China, but the application of SWHPs is rare, so is the study on SWHPs. Studies on the operating characteristics and the operation optimization of SWHPs according to the characteristics of the surface water temperatures and climate of south China have been carried out in this dissertation. Experimental and theoretical studies on the operating characteristics of open-loop SWHPs, closed-loop SWHPs and hybrid SWHPs and on the variations of the surface water temperatures when SWHPs operate are included in the first part of the dissertation. The second part deals with the operation optimization of SWHPs. The researches and the related results obtained in the dissertation are practical in engineering applications. The major works and related results include:(1) Based on the analysis of development of researches on SWHPs, a large pioneer SWHP system for district heating and cooling that utilizes lake water as heat source-sink of heat pumps in Xiangtan was designed. A series of field tests for the system were performed. The objects of the tests include the water quality, the recovery of lake water temperature, the air temperature, the entering and leaving water temperature of condenser and evaporater, COP values, etc. Based on the field tests of the COP values, SWHP performance is compared with air-source heat pump (ASHP) performance in south China. The design and tests for the system can provide considerable experiences, practical data and references for developing large SWHP system for district heating and cooling in China.(2) An integral and systemic model for closed-loop SWHP system is established. Dynamic simulation for a closed-loop SWHP system in Changsha was performed by applying the model according to the hourly load and the hourly weather data. The impacts of the coil size, the area and the depth of the water body on the entering fluid temperature and the bottom water temperature are analyzed through the simulation. The bottom water temperature with heat rejection/extraction is...