变制冷剂流量制冷系统的不稳定性分析

发布时间：2019-06-05 18:18

【摘要】：针对变制冷剂流量(VRF)系统中的过热度不稳定性振荡现象,利用变流量水冷式制冷机组设计实验。通过观察同一频率下定阀开度变压比和定压比变阀开度时系统参数的振荡现象,分析不稳定段过热度振荡机理,并得出结论。实验结果表明:随着蒸发器内液相拉长,在蒸发量一定的情况下,完全蒸干点不断地向蒸发器出口推移,系统呈现出振荡初态;当过热度跨入最小稳定信号(MSS)线的不稳定区域时,由于制冷剂流型的变化使得蒸发器两侧换热机理发生交替,从而产生了不稳定性振荡;变阀开度对质量流量的增量影响仅为变压比下的53.3%,但两工况下能够在不稳定区间达到的最大峰谷差均在3K左右;工况1~#下压比对压缩机功耗有更直接的影响,在制冷量微升的前提下仍能促使系统性能系数(COP)趋势向下。
[Abstract]:The design experiment of variable flow water-cooled refrigeration unit is carried out in view of the overheat instability and oscillation in (VRF) system with variable refrigerant flow rate. By observing the oscillations of system parameters when the valve opening ratio and constant pressure ratio change valve opening at the same frequency, the overheating oscillation mechanism of unstable section is analyzed, and the conclusion is drawn. The experimental results show that with the prolongation of the liquid phase in the evaporator, under the condition of a certain amount of evaporation, the complete evaporating point continues to move to the outlet of the evaporator, and the system shows an oscillatory initial state. When the superheat enters the unstable region of the (MSS) line of the minimum stable signal, the heat transfer mechanism on both sides of the evaporator alternates due to the change of the flow pattern of the refrigerants, resulting in unstable oscillations. The incremental effect of variable valve opening on mass flow is only 53.3% of that under variable pressure ratio, but the maximum peak and valley difference can be reached in unstable range under two working conditions is about 3k. The power consumption of the compressor is more directly affected by the lower pressure of working condition 1 # than that of the compressor, and the (COP) of the system performance coefficient can still be pushed down on the premise of the slight increase of the refrigerating capacity.
【作者单位】：上海理工大学制冷与低温工程研究所;
【基金】：上海市动力工程多相流动与传热重点实验室项目(13DZ2260900)
【分类号】：TB657

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