Optimization And Analysis On PVT And Dual Source Heat Pump Coupled System Based On Phase Change Energy Storage

The application of energy saving system in ultra low energy consumption building is still in its initial stage in China.In order to solve the problems of energy saving system in the ultra low energy consumption building,this paper is based on the Sino-German Ultra Low Energy Consumption Demonstration Center of Shenyang Construction University.Starting from the point of view to reduce the energy consumption of the system,and the principle of system energy-saving design of broaden sources of income and reduce expenditure,we should make full use of renewable energy.To optimize and analyze the phase change energy storage technology and PVT dual source heat pump coupling system,and to discuss the optimization of energy saving system of ultra low energy consumption building in cold regions,which making the foundation.of promoting the ultra low energy consumption building energy saving system in the northeast cold region.The composition of the coupled system is determined by the analysis of the type,characteristic and applicability of the phase change energy storage technology and the type of renewable energy.Using FLUNT simulation software and establishing the mathematical model of the PVT system,the PVT system is analyzed by numerical simulation.Simulation results show that with the system inlet velocity increasing from 1m/s up to 6m/s,the air return port of the vortex area enlarges,and the phenomenon of "dead zone" the gradually disappeared,the average exit temperature decreased.In the system,the process of the temperature drop of the system has experienced three stages of change,and finally tends to a fixed value.While increasing the number of outlets,when the inlet flow rate is 6m/s,the average export temperature increased by 0.6?,the thermal efficiency increased by 2.4%.When the system uses 4 export design and the inlet flow rate is 3m/s,the system is in the best operating condition,which the outlet temperature will be 21.8?,the thermal efficiency can reach 21.7%.The phase change energy storage system is studied through the analysis of the phase change materials and the phase change heat storage tank.The type of phase change material used in the system is the 46#paraffin.Using the CFD software,the numerical simulation of the phase change heat storage tank system is carried out.The change of the temperature and the liquid in the storage of PCM in the tank is analyzed.The results show that in the the storage(releasing)process,the 46#paraffin phase change storage units store(releass)a large number of latent heat,resulting in a phase change thermal storage tank in the storage and releasing process of the water temperature experienced three stages of change.Heat storage process is from 40? to 55 ?,and the melting process of 46#paraffin phase change storage unit is 16845s,and the whole storage time is 7.28h.Heat releasing process is from 55 ? to 40?,the solidification process of the heat storage unit is 17725s,the heat releasing time of the system is 7.58h,which meets the needs of heating buildings.The results of the dynamic simulation of PVT-dual source heat pump coupled system based on phase change energy storage show that in the typical day,the maximum value outlet temperature,thermal efficiency and power generation efficiency of the PVT system show in 11,which the maximum outlet temperature is 19.8 ?,the thermal efficiency is 21%,power generation efficiency is 13%.In the heating period,the average COP of the air source model of the dual source heat pump unit is 4.3,and the average COP of the ground source model is 3.96.when applying the phase change energy storage technology,the solar energy contribution rate of the system is increased by 3.1%,the operating time of the heat pump is reduced by 14.6%,which can increase the utilization rate of the renewable energy and alleviate the thermal imbalance of soil.By comparing the coupled system with the single soil source heat pump system and the central heating system in the initial investment,the annual operating cost and the recovery period of static investment,the economic benefits of the coupled system is the most obvious.Therefore,the research on PVT and dual source heat pump coupled system based on phase change energy storage has great significance in the application renewable energy in ultra low energy buildings in China.