国际协议和法规概述了逐步淘汰氢氟碳（HFC）制冷剂的计划，这些制冷剂因其对环境的影响而广泛应用于供暖、通风、空调和制冷（HVAC&R）。一些拟议的替代品是氢氟碳化合物和氢氟碳化合物（HFO）的共沸混合物。虽然这些混合物具有较低GWP的优点，但它们的冷凝不同于纯流体的冷凝。具体而言，在冷凝过程中，液相和汽相以及液/汽界面的温度和成分明显偏离平衡值。这是由于组成流体在恒定压力下的饱和温度不同造成的。此外，在冷凝过程中，低挥发性组分的优先冷凝导致高挥发性组分在界面处积聚，降低局部饱和温度并引入额外的传质阻力。 纯流体模型不考虑这些与传质相关的效应。关于HFC/HFO混合物冷凝的研究数量有限（Jacob等人，2019b）。此外，其中一些共沸制冷剂混合物被提议用于高温热泵和热泵热水器。对于此类应用，制冷剂过热温度可能高达35°C（63°F）（Arpagaus等人，2018年），这导致另一种非平衡现象的贡献增加:过热冷凝。传统上，冷凝器中的传热是通过假设局部热力学平衡并将冷凝器分为三个不同区域来建模的:单相蒸汽、两相冷凝和单相液体。然后使用适当的单个或两个参数确定每个区域的局部传热系数- 相传热关联式。然而，过去对纯过热蒸汽冷却的调查（Kondou和Hrnjak 2012；Agarwal和Hrnjak 2014）表明，一旦冷凝器管壁温度降至饱和温度以下，冷凝就开始。这发生在制冷剂体积焓等于饱和蒸汽焓的位置的上游，从而形成所谓的过热冷凝区。在该区域，由于潜热传递的普遍性，测得的局部传热系数远大于单相蒸汽关联预测的系数。由于冷凝发生在传统定义的两相区边界之外，因此了解这些条件下的压降和传热非常重要。 此外，准确预测过热冷凝传热为设计紧凑型热交换器提供了机会。引文:2020年虚拟会议扩展摘要论文

International agreements and regulations have outlined plans to phase out hydrofluorocarbon (HFC) refrigerants from a wide range of heating, ventilation, air conditioning, and refrigeration (HVAC&R) applications due to their environmental impact. Some of the proposed replacements are zeotropic mixtures of HFCs and hydrofluoroolefins (HFO). While these mixtures have the advantage of a lower GWP, their condensation differs from the condensation of pure fluids. Specifically, temperatures and compositions in the liquid and vapor phases, as well as at the liquid/vapor interface, deviate significantly from the equilibrium values during condensation. This is due to the differences in saturation temperatures of the constituent fluids at a constant pressure. Furthermore, during condensation, preferential condensation of the less volatile components leads to an accumulation of the more volatile components at the interface, depressing the local saturation temperature and introducing an additional mass transfer resistance. Pure fluid models do not account for these mass transfer related effects. There have been a limited number of investigations on condensation of HFC/HFO mixtures (Jacob et al. 2019b).In addition, some of these zeotropic refrigerant mixtures are being proposed for applications in high temperature heat pumps and heat pump water heaters. For such applications, the refrigerant superheat temperature may be as high as 35°C (63°F)(Arpagaus et al. 2018), which leads to an increased contribution from another non-equilibrium phenomenon: superheated condensation. Conventionally, the heat transfer in condensers is modeled by assuming a local thermodynamic equilibrium and dividing the condenser in to three different regions: single-phase vapor, two-phase condensation, single-phase liquid. The local heat transfer coefficients for each region are then determined using the appropriate single or two-phase heat transfer correlations. However, past investigation (Kondou and Hrnjak 2012; Agarwal and Hrnjak 2014) on cooling of pure superheated vapors have shown that condensation begins as soon as the condenser tube wall temperature drops below the saturation temperature. This occurs upstream of the location where the refrigerant bulk enthalpy equals the saturation vapor enthalpy, which leads to development of the so-called superheated condensation region. In this region, the measured local heat transfer coefficients are much greater than those predicted by single-phase vapor correlations, due to the prevalence of latent heat transfer. As condensation occurs outside the bounds of the traditionally defined two-phase region, it is extremely important to understand the pressure drop and heat transfer for those conditions. Furthermore, accurately predicting superheated condensation heat transfer offers an opportunity to design compact heat exchangers.