Study On The Heating Performance Of Radiant Floor Heating Condenser With Phase Change Material Used In Air Source Heat Pump System

With the increasingly serious energy shortage and environmental pollution,the development of renewable energy utilization and reduction of energy consumption have raised global concerns,especially in the field of building air conditioning.Therefore,the air source heat pump(ASHP),which uses abundant,clean and stable air heat energy,has been used worldwide in the field of refrigeration and heating owing to the advantages of energy-saving and environmental friendliness.At the same time,the ASHP system has become the main force of " electricity instead of coal " in China.In this paper,a novel air source heat pump system which combined radiant floor heating system and phase change energy storage technology is proposed and studied by theoretical analysis and experimental tests.The system uses radiant floor heating condenser with composite phase change material(CPCM)modules in winter.The main findings are summarized as follows:(i)The dodecanoic acid-tetradecanol-hexadecanol(LA-TD-HD)mixture is adopted as PCM which has good stability,suitable phase change temperature and high latent heat for defrosting in winter according to the theory of eutectic mixture.After that,the composite phase change material LA-TD-HD/EG is formed by adding expanded graphite(EG),and the heat storage and release rates are increased by 56.4%and 39.8%,respectively.Finally,the CPCM is packaged by aluminum alloy to form the CPCM module which is easy to install.(ii)The heat transfer model and indoor thermal environment model are established for the radiant floor heating condenser with CPCM modules and the room is conditioned by the novel system in winter and summer.Additionally,the models are verified comparing with the experimental results and the maximum deviations between the experimental results and simulated results are lower than 6.5% and 3.2%,respectively.The results indicate the heat transfer model and the indoor thermal environment model can be used to simulate and analyze the heat transfer performance of the radiant floor heating condenser with phase change material and the indoor thermal environment of the conditioning room.(iii)The radiant floor heating condenser with CPCM modules experimental test system and the system operation test platform in winter and summer are built.The thermal performance of the radiant floor heating condenser in heating and defrosting conditions,the operation performance of the system and indoor thermal environment in actual engineering are tested and analyzed.The test results show that the system can provide better indoor thermal comfort: the heating capacity transferred into the room can reach 88.4% of the heating condition in defrosting process;the COP of the system is about 30% higher than that of the air source heat pump with hot water floor radiant heating system or radiator system.(iv)The influence of pipe spacing and length,condensation temperature and refrigerant mass flow rate on the performance of radiant floor heating condenser are analyzed quantitatively by the verified heat transfer model.The influence of different parameters on indoor thermal environment in winter and summer conditions is simulated and analyzed by the verified indoor thermal environment model of the room conditioned by the novel system.The simulation results provide theoretical support and suggestions for the optimal selection of design parameters and schemes for wide application of this system.