Study On Storage Tank In Solar Assisted Heat Pump Heating System

In recent years, the demand for energy is increasing with the rapid development of economy in our country. In the all energy consumption, building energy consumption account for up to a quarter, and increase gradually. Therefore, seeking a renewable energy instead of coal for building heating become necessity. In all the renewable energy, because of solar energy's green pollution-free, it becomes the preferred. Especially, solar energy and heat pump heating system can integrate the advantages of two kinds of heat source. But there are many problems when the traditional solar energy heat pump heating system apply in cold region in China. And lack study on indirect heat storage tank structure design for the different types building. So we analysis the problems of traditional solar energy heat pump, and then propose a new solar + low temperature heat recovery air source heat pump heating system based on the direct expansion system. At the same time, we propose the calculation method about the volume and structure design of the heat storage tank.First, expound the design method of solar+low temperature heat recovery air source heat pump heating system. Point out that the determination of air source heat pump unit capacity by outdoor hourly temperature and building hourly load. In the actual calculation, the best balance point temperature should be first determined, then, calculate the capacity of unit according to the building load in best balance point temperature. Pointing out the key parameter that influence the collector area is solar fraction and collection efficiency. Obtain calculation method and process of solar fraction through the analysis of the coupling property between outdoor hourly temperature, building hourly thermal load and heat pump heating performance. The best circular flow of collecting hot side is obtained by experimental test, and then calculate the collection efficiency. Point out the calculation method of heat storage water tank volume, then determin the heat storage temperature through analysising the refrigeration + heat recovery performance of the unit.Through analysising the relationship between residential, office building operation strategy and the water tank structure design, point out the emphasis in the tank structural design for residential, office building. For residential buildings, the displacement hot coil design should give priority to thermal efficiency, choose vertical spiral coil. The tank supply and return pipe to the heat pump design should consider the volume utilization ratio. Reference for the supply and return pipe design of natural stratification cold storage tank, improve the volume utilization ratio of the tank by changing the location of inlet and out pipe and setting baffle above inlet pipe. Through CFD simulation, compare the temperature stratification and volume utilization ratio between conventional tank and tank with baffle above inlet pipe. Point out that the volume utilization efficiency can be greatly improved after changing the tank structure.Set up a small testbed in chongqing university. Through testing water temperature and internal temperature distribution of different tank structure for residential building, prove the validity of the CFD simulation results, analyze reason about the different between test results and simulation results. Test the performance of two different heat exchange coil test for office building. Results show that the heat release rate of U tube is greater than the spiral riser, has exceeded the spiral tube in the advantages of high thermal efficiency. So should choose the U tube displacement hot coil for office building. And this paper aims to study method applied to the engineering in high latitude area by analogy.Finally, analyze and forecast the affect of different structure tank on unit operation performance. Research has shown that for residential buildings, when air source heat pump combine with baffle tank, COP can be increased 3.17% than with conventional tank; For office buildings, when heat pump combine with U tube displacement hot coil tank, COP can be increased 7.16% than spiral pipe.