| The research on air source heat pump water heaters is of great significance because they can use the low-temperature heat source in the air for operation,are more energy-efficient than ordinary household electric water heaters,and have a wide range of applications.However,previous studies have had issues with high experimental costs and energy consumption.In this paper,a steady-state simulation model of the air source heat pump water heater system was constructed using the Simulink platform.Optimization conclusions were proposed to make the device more energy-efficient and have a longer service life.The reliability of the simulation model and optimization conclusions were verified by constructing an experimental platform.The main research work and achievements of this paper are as follows:1.The operational mechanism of the air source heat pump water heater system was briefly outlined,with analysis conducted on both the theoretical and practical cycle processes of the system.An effective energy analysis model was utilized to identify the key components requiring optimization,namely the compressor and condenser.2.A theoretical model for the complete air source heat pump water heater system was established by using thermodynamic principles to develop theoretical models for the four main components: the fully enclosed scroll compressor,jacketed condenser,thermal expansion valve,and finned tube evaporator.The parameters were coupled based on energy and mass equations.3.Using the Simulink platform of the Matlab software and based on the theoretical models established in the previous section,separate simulation models were built for each of the four major components.These models were then coupled together to obtain a simulation model for the entire system.Furthermore,the simulation program interface was designed using the GUI module of the Matlab software to simplify the operation process.4.To validate the simulation results under three typical operating conditions with environmental dry/wet bulb temperatures of 5℃/3℃,20℃/16℃,and 35℃/26℃ respectively,an experimental testing platform was constructed.The results of the study indicated that the error between the experimental and simulation results was less than 10%,thereby verifying the reliability of the simulation model.5.Based on the simulation model,the effects of ambient temperature,cold water inlet temperature,cold water flow rate,and compressor speed on performance parameters such as heating capacity,power consumption,COP,suction pressure,discharge pressure,and discharge temperature were analyzed.Optimization conclusions were proposed,based on the principle that higher COP indicates higher energy efficiency of the equipment and smaller compressor pressure ratio indicates longer service life of the equipment.These optimization conclusions were then verified through experiments,confirming their reliability.The simulation results and optimization conclusions are as follows:(1)With all other operating conditions remaining constant,when the ambient dry/wet bulb temperature increased from 5℃/3℃ to35℃/26℃,the COP of the system increased by approximately 52%,and the compressor pressure ratio decreased by approximately 25%.Therefore,using the equipment in higher ambient temperatures within the range of 5℃-35℃ is an effective optimization method.(2)The COP of the system increased by approximately 25%-32%,and the compressor pressure ratio decreased by approximately 22%-50%with all other operating conditions remaining constant,when the cold water inlet temperature decreased from 20℃ to 5℃.Additionally,the outlet water temperature decreased by approximately 15%-45% during a single operation.Therefore,within the range of 5℃-20℃,reducing the cold water inlet temperature is an effective optimization method when there is no high requirement for the supply water temperature.(3)With all other operating conditions remaining unchanged,increasing the cold water flow rate from 0.025 kg/s to 0.035 kg/s led to a COP improvement of approximately 20%-44% and a reduction in compressor pressure ratio of approximately 14%-24%.Furthermore,the outlet water temperature decreased by approximately 20%-21% during a single operation.Therefore,within the range of 0.025 kg/s to 0.035 kg/s,increasing the cold water flow rate is an effective optimization method when there is no high requirement for the supply water temperature.(4)When all other operating conditions remained constant,reducing the compressor speed from 3500r/min to 2800r/min resulted in a20%-26% increase in the system’s COP,and a 32%-53% decrease in the compressor pressure ratio.Thus,within the range of 2800r/min to3500r/min,reducing the compressor speed is an effective optimization method. |
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