Experimental study on the effect of fan speed on performance of a CO2 air source heat pump water heater
In order to quantitatively explore the change law of the CO2 air source heat pump water heater system performance with fan speed,the influence of fan speed change on discharge pressure,superheat,CO2 mass flow rate,system heating capacity,total power consumption of the system and the coefficient of heating performance COP under different working conditions were studied through experiments.The response surface method was used to optimize the experiment,and the COP regression model was fitted with the experimental data and the reliability analysis was carried out.The optimal operating condition of the system was predicted by the regression model and verified by the experiment.The results show that there is an optimal fan speed existing in CO2 air source heat pump water heater when the compressor frequency and opening of the electronic expansion valve(EEV)is constant.In the range of 45～85 Hz,with the increase of compressor frequency,the COP increases first and then decreases with the increase reaching up to 8.97%,and the optimal fan speed corresponding to the maximum COP at each frequency decreases continuously.In the range of 35%～55%,with the increase of EEV opening,the COP increases first and then decreases,with an increase of 6.6%,and the optimal fan speed corresponding to the maximum COP under each EEV opening increases continuously.When the compressor frequency is 65 Hz and the EEV opening is 50%,the corresponding optimal fan speed is 1 000 r/min,and the system COP reaches its peak(4.09).The maximum error of COP regression model fitted is 4.5%.The predicted optimal operating conditions of the system are as follows:Compressor frequency is 68 Hz,EEV opening is 52%,and fan speed is 956 r/min.Under this operating condition,the COP of the system reaches the maximum value of 4.29,and the prediction error is 3.7%.This study can provide theoretical guidance for CO2 air source heat pump water heater system to maintain efficient operation.
CO2 heat pump water heaterfan speedsystem performanceexperimental research
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