空冷式换热器中两相制冷剂质量的新计算模型

Novel Calculation Method of Two Phase Refrigerant Mass in Air Cooled Heat Exchanger

在制冷装置压缩机刚开机过程中,空冷式换热器两相区制冷剂质量计算需考虑干度强非线性分布。在此建立了分区集中参数换热器模型两相区质量制冷剂新计算模型。通过分布换热器模型预测两相区干度分布,引入相对长度实现通用化描述换热器结构在不同运行工况下两相区任意点位置,进而拟合基于相对长度的两相区制冷剂干度分布多项式分布模型,从而推导出两相区的平均空泡系数,最终可用于预测两相区制冷剂质量。将新模型与已有的基于干度线性分布的两相制冷剂质量计算模型进行对比,结果表明:当干度分布呈现非强非线性分布时,两种模型的预测精度的差别可忽略;但是当两相区制冷剂干度分布呈现强非线性分布时,以分布参数计算为基准,新计算模型相对于已有模型的平均误差和最大误差分别减少为原来的59%和55%,新计算模型具有很好的精度;同时两种模型的计算速度相当。

When compressor starts and doesn＇t reach stable, the two phase refrigerant mass calculation should consider the affection of non-linear quality distribution. A novel refrigerant mass calculation method for phase-lumped air cooled heat exchanger model is proposed. Firstly, the refrigerant quality distribution is predicted based on distributed heat exchanger model, then the dimensionless length of arbitrary point for two phase zone is introduced to describe the point of two phase zone; and then the refrigerant quality with the dimensionless length is fitted in polynomial; lastly, the mean void fraction for predicting two-phase refrigerant mass is described. When the refrigerant quality distribution is nearly linear, the difference of predicted refrigerant mass between the novel model and the existed model is small. When the refrigerant quality distribution is intensively non-linear, comparing with the existed two-phase refrigerant mass calculation model based on linear quality distribution, the novel two-phase refrigerant mass calculation model can decrease mean deviation and max deviation respectively to the 59% and 55% of the original ones, while the calculation speeds of these two models are similar.