NUMERICAL SIMULATIONS OF CONDENSING R134a FLOWS IN HORIZONTAL PIPES

D. Juggurnath
Department of Mechanical and Production Engineering, University of Mauritius, Reduit, Mauritius

Muhammad Zaid Dauhoo
Department of Mathematics, University of Mauritius, Reduit, Mauritius

M.K. Elahee
Department of Mechanical and Production Engineering, University of Mauritius, Reduit, Mauritius

Abdel Khoodaruth
Department of Mechanical and Production Engineering, University of Mauritius, Reduit, Mauritius

Jaco Dirker
Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria, South Africa

Josua Petrus Meyer
Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria, Private Bag X20, Hatfield, 0028, South Africa

Christos N. Markides
Clean Energy Processes (CEP) Laboratory, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom

DOI: 10.1615/TFEC2019.cmd.028053
pages 413-422

キーワード： numerical modelling, condensation, pressure drop, two-dimensional numerical simulation, R134a

要約

Three-dimensional numerical simulations were performed of condensing R134a flows in a smooth horizontal pipe with an inner diameter of 8.4 mm and a length of 1.5 m, and validated against experimental results. A constant mass flux of 100 kg m⁻² s⁻¹ was considered and the influence of vapour qualities (0.25 to 0.75) and saturation temperatures (30 °C and 40 °C) on the resulting flow regimes and heat transfer characteristics of these flows were investigated. The volume-of-fluid (VOF) method was employed in the numerical framework to track and reconstruct the interface between the liquid and vapour phases. The simulations, given the imposed flow conditions, produced stratified wavy flow which are in agreement with the expected flow pattern based on the El Hajal flow pattern map. The heat transfer coefficient in the numerically simulated flows were found to be in good agreement (within 1.3%) with corresponding experimentally-measured values. From the simulations, the liquid-phase height at the bottom of the pipe was observed to be smaller with increasing vapour quality, which results in an increase in the heat transfer coefficient. A thicker film thickness and lower heat transfer coefficient were noted at the higher saturation temperature.