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    Öğe
    Beyond direction-agnostic assumptions: Direction-integrated models for asymmetric falling film thickness and heat transfer under multidirectional vapor shear
    (Pergamon-Elsevier Science Ltd, 2026) Zhao, Chuang-Yao; Li, Qiong-Tao; Jia, Chen-Yi; Zhang, Fang-Fang; Qi, Di; Yildizhan, Hasan; Jiang, Jun-Min
    The orientation of vapor streams in falling film evaporators (FFEs), determined by tube bundle configurations, plays a critical role in shaping liquid film hydrodynamics and heat transfer performance. Conventional models adopt direction-agnostic assumptions, averaging vapor shear effects and introducing significant errors in localized predictions. This study proposes a direction-integrated framework that explicitly incorporates vapor orientation as a governing parameter, capturing the asymmetric effects of multidirectional vapor shear on film thickness and heat transfer. The proposed correlations are validated against a broad range of benchmark data, achieving 80 % of film thickness predictions within +25 % error, over 86 % of local heat transfer coefficients within +20 %, and all average values within +5 %. Comparative analysis shows strong agreement with experimental and numerical results under gravity-driven, laminar conditions. Vapor directionality is shown to significantly alter heat transfer along the tube periphery, especially between upper and lower regions. These findings enhance the predictive reliability of FFE modelling and provide valuable guidance for optimizing evaporator design and improving energy efficiency in industrial applications.
  • [ X ]
    Öğe
    Falling film hydrodynamics and heat transfer under vapor shearing from various orientations
    (Aip Publishing, 2024) Zhao, Chuang-Yao; Li, Qiong-Tao; Zhang, Fang-Fang; Qi, Di; Yildizhan, Hasan; Jiang, Jun-Min
    Vapor shearing is a common issue encountered in the operations of falling film heat exchangers. The vapor stream effect depends on its orientation. This study investigates liquid film hydrodynamics and heat transfer performance under the influence of vapor streams from different orientations. The results indicate that both orientation and velocity of vapor determine the encountering time and position of the films on the tube's two sides. The liquid film thickness uniformity and the liquid column deflection vary significantly depending on the orientation and velocity of the vapor. Zones of accelerated liquid film, climbing liquid film, liquid stagnation, and transition of liquid film flow pattern are observed. The gradient of film thickness along the tube axis and the deflection in time-averaged peripheral film thickness increase as the vapor orientation varies from 0 degrees to 90 degrees and subsequently decrease as the vapor orientation varies from 90 degrees to 180 degrees. Vapor streams have more pronounced effects on time-averaged peripheral film thickness in regions close to the liquid inlet and outlet. Vapor streams result in changes in peripheral heat transfer coefficients toward the downstream side depending on the orientation and velocity of the vapor. The impact of vapor streams on the overall heat transfer coefficient does not directly correlate with the velocity of the vapor when maintaining the same orientation.