Simulation Study On Solar-ground Source Heat Pump Combined Heating Digester In Cold Regions

In cold regions, As the winter air temperature and ground temperature are low, methane gas production rate and utilization rate is very low, even digesters were frozen crack. Most method of heating is suitable for individual users of methane tank. In cold regions, for large and medium biogas to heat insulation, thereby ensuring utilization of biogas digesters in the winter, Currently gives no good way. This shows an urgent need to find a practical method of heating large and medium-sized methane tank. This shows an urgent need to find a practical method of warming and medium-sized biogas digesters to meet the development requirements of biogas. Therefore, this paper proposed new ideas of the application of solar energy - ground source heat pump heating methane tank. Namely,use the hot water which has been producted by solar energy - ground-source heat pump hot water heating system ,then,make the hot water through the heat exchange tube heating methane surrounding material liquid, and combining with the internal control system, make the methane gas temperature is maintained at best temperature fermentation. This paper uses a simulation calculation based on combined heating system in the whole calculation under different meteorological conditions simulated to verify the new system in cold region can be achieved.First of all, for a methane tank in cold region,whose volume is 500m3. Use Fluent simulated with the plus heat in the liquid of methane tank, methane tank and surrounding temperature field, and optimize the digester size and insulation. On the basis of methane tank load, preliminary select solar collectors area, underground u-shaped heat exchanger area, heat pump units and other components.Secondly, Use matlab to optimize the area of solar collector selection and U-ground soil heat exchanger heat transfer area, also developed a system model of the start and stop conditions, and Simulated the system operation throughout the year.Finally, the three strategies on the digester heating are compared for economic analysis and the system in this paper is predominant and economical, which further verified the feasibility of this system in cold regions.The results of this study will have some reference value for building a large or medium-sized biogas digesters in north cold area of china .Meanwhile ,this paper laid the initial foundation for this system's continuing application.