| Renewable energy is one of the most effective ways to solve energy shortage and environmental pollution.However,due to the limitation of existing technologies,there are many challenges in the practical application of renewable energy.How to effectively promote the development of renewable energy utilization technology and gradually realize the orderly replacement of fossil fuels by renewable energy is a hot issue.And solar energy and air energy are widely used as an environmentally friendly,safe and renewable energy source.The heat pump technology can realize the comprehensive utilization of solar energy and air energy and other renewable energy sources.In this paper,we design a micro heat pipe heat exchanger that can realize the complementary utilization of solar energy and air energy by using micro heat pipe array,flat aluminum channel and serrated fins as the main components to form the core heat transfer components,and apply it to the heat pump system to form the solar-air composite heat source heat pump system,and carry out the relevant experimental tests and theoretical studies.The relevant experimental tests and theoretical studies were conducted to provide data support for further optimization of the composite heat source heat pump system and to promote the application of heat pump technology in the field of energy saving and emission reduction in buildings,with the main work and conclusions as follows:Firstly,we designed the micro heat pipe heat exchanger and the solar-air composite heat source heat pump system with its core components and built the experimental test platform.It also developed a system operation strategy using three modes:air source heat pump(ASHP),photovoltaic/thermal water source heat pump(PV/T-WSHP)and photovoltaic/thermal water&air source heat pump(PV/T-W&ASHP)to meet various weather conditions under the heating operation condition.Secondly,performance and operational characteristics of the heat pump system were experimentally tested and analyzed.The results show that both the fin side and the micro-heat pipe array(MHPA)side inside the micro-heat pipe heat exchanger are uniformly heated,and their longitudinal temperature difference values are kept to fluctuate between 0-1°C and 0-0.5°C,respectively.When the air flow rate reaches 777.6 m~3/h,the temperature difference between the import and export on the fin side reaches 4.4°C,which can better achieve the heat absorption in the ambient air;while the water flow rate of the MHPA side is at 0.33 m~3/h,the temperature difference between the import and export on the MHPA side reaches 4.88°C,which shows the excellent heat transfer performance of the MHPA.Moreover,under the winter heating condition,the average COP of the heat pump in ASHP mode is 2.08;PV/T-WSHP mode can realize photovoltaic power generation while producing hot water,with a power generation efficiency of 14.26%,an average heat collection efficiency of 38.85%and an average heat pump COP of 3.30;PV/T-W&ASHP mode uses solar energy and air energy to complement each other to realize heat generation.The PV/T-W&ASHP model also has the function of photovoltaic power generation,with a power generation efficiency of 13.27%,an average heat collection efficiency of 24.14%,and an average heat pump COP of 2.80.On the other hand,compared with the performance of different structural forms of heat pump systems,the future application prospects of the system proposed in this paper are more advantageous in terms of the complexity of the system piping,the amount of space occupied and the overall performance of the heat pump system.Then,the theoretical model of solar-air composite heat source heat pump system with micro heat pipe heat exchanger as the core component is established by MATLAB through the aggregate parameter method,which mainly includes solar radiation calculation model,PV/T collector model,low temperature water tank model,micro heat pipe heat exchanger model,compressor model,casing heat exchanger model,energy storage tank and capillary tube model,and the accuracy of the model is verified based on the actual measurement data.Finally,the validated theoretical model was used to analyze the influence law of external environmental parameters as well as system component operating parameters on the performance of micro heat pipe heat exchanger and heat pump system using the control variable method.The results show that for both ASHP and PV/T-W&ASHP modes,the heat exchanger airflow velocity has a greater effect on the component and heat pump system performance,while for PV/T-WSHP mode,the heat exchanger hot water tank water flow rate has a greater effect on the heat pump performance and PV/T collector photoelectric thermal performance.Furthermore,in terms of optimal matching of heat pump system components,the PV/T collector area is in the range of1.7m~2-5.1m~2,and the performance of the heat pump system is improved significantly.The heat exchanger mainly optimizes the structure of its heat transfer module.Compared with the time when the fins were not added,the heat exchanger’s heat intake rises significantly after the fins are added,and the COP of the heat pump is improved by about 22%. |
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