Simulation And Experimental Study Of Air Source Heat Pump System Based On Intermediary Heat Exchang

At present,air source heat pumps have become the most widely used form of heat pump in China.However,conventional low-temperature vortex air source heat pumps have relatively small heating capacity per unit,complex control logic for parallel heating of multiple units,and are prone to cold island effects.Large capacity air-cooled screw units are limited by noise and defrosting issues,making them difficult to apply in civil buildings.To address the above issues,an air source heat pump system based on intermediate heat exchange was proposed,and the structure of the surface cooler in the intermediate system was optimized.A low energy consumption defrosting scheme was proposed,and the energy consumption characteristics and operating economy of the system during heating were analyzed through numerical simulation.The main content of the study includes:A type of air source heat pump system based on intermediate heat transfer was constructed,and the operating principle of the system was presented.The focus was on studying the influence of the structure,material,and fluid flow mode of the intermediate system surface cooler on frost formation,corrosion resistance,and heat transfer characteristics of the surface cooler.Based on this,a heat transfer mathematical model of the surface cooler was established.The accuracy of the heat transfer mathematical model of the surface cooler was verified through experimental methods,and the structure of the surface cooler was optimized.The experimental results show that the maximum deviation between the mathematical model of the approximate counter current surface cooler and the experiment is 3.06%;The approximate reverse flow pipeline connection method can increase the heat transfer capacity of the surface cooler by 28.7% under the same heat exchange area;The heat transfer efficiency of the surface cooler is highest when the fin spacing is 2.0-2.4mm,the tube spacing is 18-22 mm,and the number of tube rows is 4-6.A new alternative defrosting scheme for hot and cold water tanks was proposed,and the feasibility of the scheme was verified through design experiments.The defrosting energy consumption of the system was analyzed.The experimental results show that when the ambient temperature is 0℃ and the air humidity is between 70% RH and 80% RH,the surface cooler undergoes complete frost formation after 30 minutes.After frost formation,the wind resistance of the surface cooler increases by 135Pa;When the heat storage temperature is 30℃,the automatic control system can effectively defrost,with a defrosting time of 6 minutes.At the end of defrosting,the surface temperature of the fins is 10℃,and the defrosting heat consumption is 12428.5k J;The defrosting energy consumption of this scheme is reduced by 79% compared to the conventional hot water tank cycle defrosting scheme,and the proportion of defrosting energy consumption to the unit heating capacity within the defrosting interval is reduced by 12.2% compared to the conventional air source heat pump.The simulation models of the air source heat pump heating system and the conventional low-temperature vortex air source heat pump heating system based on the intermediary heat transfer are constructed,and the actual heating performance of the two heating system is simulated.The simulation results show that the end return water temperature of the two heating system in the heating season is higher than 32℃,which meets the requirements of building heat consumption;The average COP of the air source heat pump system based on intermediate heat transfer during the heating season is 2.39,while the average COP of the conventional low-temperature vortex air source heat pump system during the heating season is 1.94;The pump and fan energy consumption of the intermediary system during the heating season accounts for 25.5% of the total energy consumption of the system,and the dynamic investment payback period of the system is 3.6 years.The air source heat pump system based on intermediate heat exchange solves the problems of high noise reduction cost and high defrosting energy consumption faced by air-cooled screw units in civil building applications.Research has shown that the system has high stability and reliability,and has broad application prospects.