CO_2热泵热电池储能性能实验研究

Experimental Study on CO_2 Heat Pump Thermal Battery System

CO_2热泵热电池系统由跨临界二氧化碳水源热泵与蓄冷蓄热装置组成,其在储能过程中系统的效率会逐渐降低。本文实验研究了CO_2热泵热电池的储能性能,分析了储冷罐、储热罐循环水体积流量、压缩机频率和电子膨胀阀开度对储能效率的影响。结果表明:低循环水流量既可使储能罐获得良好的温度分层,又能获得较大的换热量;压缩机频率越高,系统效率越大;同时电子膨胀阀开度也影响系统的储能效率。当压缩机频率为50 Hz,电子膨胀阀开度为330脉冲,储冷罐、储热罐循环水体积流量分别为0.2 m^3/h、0.1 m^3/h时,总体COP最大,为5.49。同时数学拟合了系统COP与储冷罐、储热罐出水温度、控制参数的关联式,提出了一种基于遗传算法的优化控制策略,系统总COP可达6.29。

CO2 heat pump thermal battery system consists of a water-source transcritical carbon dioxide heat pump coupled with hot and cold thermal storage, and its performance gradually decreases during the process of thermal energy storage. This paper presents experimental studies of a CO2 heat pump thermal battery system. The performance of this system was tested under a variable water-circulation volume flow rate for the hot/cold tank, a variable compressor frequency, and electronic expansion valve （EEV） opening. The results show that adoption of a lower water-circulation flow rate allows the tank to obtain good thermal stratification and a larger capacity. Further, a high compressor frequency benefits the system performance. The EEV opening also influences the system performance. The overall coefficient of performance （COP） reaches a maximum of 5.49 when the compressor frequency is 50 Hz, the EEV opening is 330 pulse, and the hot and cold water volume flow rates are 0.1 and 0.2 m3/h, respectively. Moreover, through mathematical fitting, a correlation was established between the COP, the outlet temperatures of the hot and cold tanks, and the control parameter. Overall, the total COP is 6.29 when the optimal control strategy based on the genetic algorithm is applied.