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Modeling of In-Tube Condensation of Zeotropic Mixtures

机译：共沸混合物的管内冷凝模型

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摘要

Studies in the literature have shown that zeotropic mixture condensation rates are lower than those predicted using a pure-fluid approach. This has been attributed to the decrease in fluid temperature that occurs with zeotropic mixtures and to the development of concentration gradients in the vapor-phase that limit the condensation heat transfer. The decrease in the apparent heat transfer coefficient is not consistent across mass fluxes, tube diameters, fluid combinations, saturation pressures, and concentrations. Several modeling techniques exist, which allow engineers to model the decrease in heat transfer rates. This study provides guidelines on when the mass transfer effects can be neglected and when it is appropriate to apply established models in the literature. A condensation database containing fluid combinations of pairs of hydrocarbons, ammonia and water, and synthetic refrigerants across large changes in operating conditions, tube diameters, and concentrations is used to validate the approach. The proposed framework predicts that the Bell and Ghaly (1973, "An Approximate Generalized Design Method for Multi-componentl Partial Condensers," AIChE Symp. Ser., 69, pp. 72-79) approach is valid for mid- and high-reduced pressures, i.e., above 0.40, while explicitly accounting for mass transfer is necessary at lower reduced pressures, i.e., below 0.40, where the influence of the temperature glide in the Bell and Ghaly method is weighted too strongly.
机译：文献研究表明，共沸混合物的凝结率比使用纯流体方法预测的更低。这归因于共沸混合物所引起的流体温度的降低以及气相中限制冷凝热传递的浓度梯度的发展。表观传热系数的降低在质量通量，管径，流体组合，饱和压力和浓度之间不一致。存在几种建模技术，这些技术允许工程师对传热速率的降低进行建模。这项研究为何时可以忽略传质效应以及何时在文献中应用已建立的模型提供了指导。冷凝数据库中包含烃，氨和水以及合成制冷剂对的流体组合，这些流体组合跨越了运行条件，管径和浓度的较大变化，从而验证了该方法。拟议的框架预测，Bell and Ghaly（1973，“多组分部分冷凝器的近似通用设计方法，” AIChE Symp。Ser。，69，pp。72-79）方法对中低还原度有效。压力（即高于0.40），而在较低的减压（即低于0.40）中明确考虑传质是必要的，在贝尔和加利方法中，温度滑移的影响权重过大。

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  • 来源
    《Journal of Heat Transfer》 |2016年第9期|091502.1-091502.7|共7页
  • 作者

    Malcolm Macdonald; Srinivas Garimella;

  • 作者单位

    Sustainable Thermal Systems Laboratory, GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30382;

    Sustainable Thermal Systems Laboratory, GWW School of Mechanical Engineering, Georgia Institute of Technology, Love Building, Room 340, 801 Ferst Drive, Atlanta, GA 30332;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
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