Solar Energy Coupling Integration Of Air Source Heat Pump Hot Water System Of Performance Research

With the rapid growth of China's economy,the energy consumption of building air-conditioning heating has risen rapidly.Energy shortages and environmental pollution caused by the burning of traditional fossil fuels have become increasingly prominent.The task of developing and utilizing clean renewable energy is extremely urgent.Solar energy and air energy are two types of renewable energy that are inexhaustible and lighter to the environment.In recent years,they have received high attention and favor.The air source heat pump is small in size and high in efficiency,and can replace centralized heating by means of coal burning.It plays a decisive role in the“replace coal-fired heating with electricity”market.At present,the utilization of solar energy is mostly in the preparation of hot water for domestic use.Because of its timeliness and instability,it is limited in the heating of buildings and needs to be optimized with other energy assistance or energy storage technologies.Therefore,the heating method combining solar energy and air energy comes out.The existing solar energy and air energy coupling utilization methods are mostly solar-air source heat pump systems,solar air preheating air source heat pump systems,and solar phase change heat storage auxiliary air source heat pump systems.These systems generally have large footprint and expensive initial investment.The proposed solar integrated air source heat pump(SASIHP)is based on the traditional air source heat pump,and then sprays a solar selective absorbing coating on the surface of the evaporator to form the core component—solar finned tube evaporator.SASIHP absorbs solar energy,mainting the advantages of small footprint,easy installation,and forced convection with air,achieving multi-directional energy utilization,and improving system performance.According to research conducted by the research group,SASIHP is used in the refrigerant direct radiant heating system(SASIHP RFHW),with an average COP of the coldest month of 3.02 and a hottest month of 4.03,an increase of 8.1%over the conventional air source heat pump system;For the hot water system(SASIHP DHW),the average summer COP was 6.03,which was 44.16%higher than that of the conventional air source heat pump hot water system,and the average COP of the winter operating system was 3.25,which was 6.56%higher than that of the conventional air source heat pump hot water system.However,the solar energy absorption area of SASIHP is not large enough and is severely blocked by the fan.The proposed WF-SASIHP is based on the SASIHP to widen the solar finned tube evaporator by reducing the number of heat exchanger tubes and set it on the fan drum.This collector evaporator has a larger solar collector surface and can absorb more solar energy under the same conditions.In the structural design of the evaporator,the total heat transfer coefficient is an indispensable parameter.The total heat transfer coefficient of the conventional finned tube evaporator includes the refrigerant-side heat transfer coefficient and the air-side heat transfer coefficient,and does not consider the influence of solar radiation.The solar finned tube evaporator is different from the traditional finned tube type in that the surface thereof is coated with a solar absorbing coating,and solar heat gain and radiation heat exchange between the wall surface and the air need to be considered.Therefore,on the basis of the steady-state mathematical model of the original finned tube evaporator,the solar radiation heat gain coefficient and the solar radiation convection heat transfer coefficient are introduced to represent the solar radiation energy per unit area of the finned tube for every 1K rise.Building a mathematical model of the solar finned tube evaporator.The experimental verification shows that the error of the new model is within 5%,and the traditional mathematical model is used to calculate the heat transfer of the s solar finned tube evaporator with an error of more than 10%.Using MATLAB to write the simulation program of solar finned tube evaporator,design program of solar finned tube evaporator,and simulation program of performance parameters of solar finned tube evaporator and its heat pump,In turn,it is used to simulate the simulation of solar finned tube evaporator,provides calculation data when verifying the mathematical model,and calculating the structural parameters of WF-SASIHP RFHW under different solar irradiation.The airflow organization of SASIHP and WF-SASIHP is also different.SASIHP's collector evaporator is located on the suction side of the fan,while WF-SASIHP's collector evaporator is located on the blower side of the fan.FLUENT was used to simulate the airflow of WF-SASIHP.The results showed that the average wind speed of the blower side was larger than that of the suction side.The numerical values were similar to the experimental values.Using the average wind speed on the blower side of the fan as the oncoming wind speed of the collector evaporator,using the same rated heating capacity and compressor power as the SASIHP are used,as the outdoor temperature is 0°C and the humidity is 15%,the structural parameters of WF-SAIHP's evaporator has been designed.After calculation,the total heat exchange tube length of the WF-SASIHP's collector evaporator is 20m,the total air volume is 3000m~3/h,and the rated COP is 3.489.Comparing the performance parameters of the SASIHP and WF-SASIHP heat collectors under different solar irradiations,the total heat transfer coefficient of the WF-SASIHP heat collector is smaller,and the total heat resistance is less after 150 W/m~2.Comparing the performance parameters of SASIHP RFHW and WF-SASIHP RFHW under different solar irradiations,the system COP of WF-SASIHP RFHW is gradually higher than SASIHP RFHW after solar irradiation above 250 W/m~2,and when the solar radiation is 700 W/m~2,it reaches 3.87.In general,the performance of WF-SASIHP is more significantly changed by solar irradiation.