Theoretical And Experimental Investigation On Solar Energy-Phase Change Thermal Storage Heating System

Because of located in cold area and a long winter heating period in Beijing, building heating energy consumption accounts for a major part of building energy consumption in the Beijing area.Considering there is a lot of solar energy in Beijing, if make full use of solar energy as a supplement building heating in winter, it can not only reduce fossil energy consumption, but also raise solar energy utilization rate in the building heating. But because of inherent instability and intermittent of solar energy, it is difficult to directly take solar energy to the heating end with steady demand. Based on the previous research on phase change thermal storage technology,taking advantage of the PCM's characteristic with large latent heat and nearly keep constant melt temperature in charge and discharge period, the solar energy - phase change thermal storage - fresh air heating system is proposed. In this system, when solar radiation intensity is high at noon, it can store excess solar energy to the phase change thermal storage. And when solar radiation intensity is low at night or in the morning, the heat energy stored in PCM is used to heat fresh air. So it is achived the transfer of solar energy in time and place by this system. Considering the above academic thought, based on theory of heat transfer, fluid dynamics and phase change energy storage, some researches are carried out in the following:(1) The heat transfer model for all - glass vacuum tube collector to be used in a forced - circulation solar water heating system is established. In this model, the simplified heat transfer of the collector consists of natural convection within a single glass tube and a forced flow in a manifold header. From this, the heat balance equation of collector and the heat balance and flow equation of the single tube can be established. When known the solar radiation intensity, outdoor air temperature, as well as the inlet temperature of heat transfer fluid, outlet temperature of collector can be calculated according to the model.(2) Based on previous research, the improved phase change storage heat transfer model was published. By coupled solar collector and phase change thermal storage model, the heat transfer problem between solar collectors and phase change thermal storage is studied.(3) Based on the above research, the heat transfer model on solar energy - phase change - fresh air heating system is built. According to the system model and solar radiation in winter in Beijing, the optical collector system flowrate, the optical ratio between phase change material quality and collector area are analyzed. And operating strategy and operating conditions research to ensure the supply fresh air temperature stable is researched too.