变流量制冷系统循环性能稳定性的实验研究

Experimental Study on Stability of Cycle Performance of Refrigeration System with Variable Refrigerant Flow

针对变制冷剂流量（Variable Refrigerant Flow,VRF）空调系统中过热度、制冷量及性能系数（Coefficient of Performance,COP）等参数的不稳定现象,利用R32变流量制冷循环实验台,研究过热度振荡对系统参数稳定性的影响。结果表明：随着系统内制冷剂流量的增加,蒸发器内制冷剂流型迅速变化,引起换热方式的交替,过热度进入最小稳定过热度线（Minimal Stable Superheat,MSS）的不稳定区间,从而产生了过热度振荡;当过热度处于不同运行频率下的最小稳定点时,系统性能达到最佳,控制难度得到优化;系统定压比运行下,频率的增大对压缩机耗功有更直接的影响,因而导致COP与频率成反比。

In view of the instability of the parameters such as superheat, cooling capacity and coefficient of performance in the air conditioning system with variable refrigerant flow, the influence of the overheat oscillation on the stability of the system parameters is studied by using the R32 variable flow refrigeration cycle test bench. The experimental results show that with the increase of the refrigerant flow in the system, a rapid change of the refrigerant flow pattern in the evaporator leads to the alternating heat transfer mode, and the superheat enters the unstable region of the minimum stable superheat line, thus resulting in the superheat oscillation. When the superheat is located at the minimum stable point and with different op- erating frequencies, the system performance is the best and the difficulty of the control has been optimized. The increase in the frequency of the system under the constant pressure ratio has a more direct effect on the compressor power consumption, resulting in an inverse ratio of COP to frequency.