Numerical investigation of flow boiling characteristics of R134A in a smooth horizontal tube

• Published in: International journal of heat and mass transfer Vol. 227; p. 125596
• Main Authors: Osowade, EA, Adelaja, AO, Olakoyejo, OT, Obayopo, SO, Tryggvason, G, Meyer, JP, Markides, CN
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2024
• Subjects: ANSYS Fluent; CFD; Evaporation; Flow boiling; Frictional pressure drop; Heat transfer; phase change; CFD; Flow boiling; phase change; ANSYS Fluent; Frictional pressure drop; Evaporation; Heat transfer
• ISSN: 0017-9310
• DOI: 10.1016/j.ijheatmasstransfer.2024.125596

•R134a flow boiling 3D simulations were performed in smooth tubes using ANSYS fluent.•Effect of saturation condition, heat and mass flux was studied at varying diameter.•Heat transfer and pressure drop results are in dimensional and non-dimensional forms.•Results agree well with relevant correlations and experiments with low deviations.•Findings contribute to understanding flow boiling and optimizing heat exchangers. Three-dimensional transient simulations using ANSYS Fluentʼs mixture multiphase model was conducted to investigate the impact of heat flux, mass flux, and saturation temperature variations on pressure drop behaviour and heat transfer characteristics during flow boiling of R134a refrigerant in smooth horizontal tubes of different diameters. The simulations employ an implicit numerical method to solve the governing equations, with relevant source terms for mass and energy transfer, incorporating the continuum surface force (CSF) and shear stress transport (SST) κ-ω models to account for surface tension and flow turbulence respectively. The results are presented in both dimensional (heat transfer coefficient and pressure drop) and non-dimensional (Nusselt number and two-phase frictional factor) forms. The Nusselt number shows a direct relationship with the Reynolds number, while the two-phase friction factor exhibits different behaviour. At higher vapor quality, mass flux significantly affects heat transfer performance and pressure drop. Heat flux plays a crucial role in heat transfer, but its impact on pressure drop is negligible. Higher saturation temperatures enhance heat transfer while reducing pressure gradients. The obtained results demonstrate good agreement with existing correlations, with mean absolute deviations (MAD) as low as 1.2 % for the heat transfer coefficient and 23.7 % for the pressure drop behaviour. This highlights the model's accuracy in predicting flow boiling behaviour of R134a in smooth horizontal channels, providing valuable insights for thermal analysis. The findings contribute to the understanding of flow boiling processes and aid in designing and optimizing efficient heat exchangers for various engineering applications.