Modeling Of Heat Transfer Coefficients During Condensation At Low Mass Fluxes Inside Horizontal And Inclined Smooth Tubes

Abstract

In this study, in-tube condensation was conducted for mass fluxes of 100, 75 and 50 kg/m²s, and temperature differences of 1, 3, 5, 8 and 10 °C. Measurements and flow regimes were captured at various mean vapor qualities between 0.1 and 0.9 inside an inclined smooth tube with an inside diameter of 8.38 mm and 1.49 m long. Fifteen distinct inclination angles from -90° to 90° were considered while the condensation temperature was always maintained at 40 °C. The experimental results showed that the inclination angle significantly influenced the flow patterns and the heat transfer coefficients. It was also shown that the heat transfer coefficient was dependent on the temperature difference, even though this dependency was greater for downward flows than for upward flows. By using the experimental data and fuzzy C-means clustering adaptive neuro-fuzzy inference system (FCM-ANFIS) technique, a model was proposed for the prediction of heat transfer coefficients during condensation of low mass fluxes inside inclined smooth tubes. By using three statistical criteria, the performance of the proposed model was examined against experimental data and it was found that FCM-ANFIS was a strong tool for the prediction of the heat transfer coefficient based on the effective parameters of vapor quality, temperature difference and inclination angle.

Additional information

Notes on contributors

Daniel Raphael Ejike Ewim

Daniel R. E. Ewim obtained his B.Eng. in Mechanical Engineering (Refrigeration & Air-Conditioning Engineering) in 2006 from the Federal University of Technology Owerri, Nigeria and his M.Eng. in Mechanical Engineering (Energy Studies) in 2012, from the University of Agriculture, Makurdi, Nigeria. He is currently completing his Ph.D. in Mechanical Engineering at the University of Pretoria, South Africa. He is a member of the Clean Energy Research Group at the University of Pretoria and his research interests include thermofluids, nanofluids, nuclear thermohydraulics, clean energy, CFD, refrigeration and engineering education.

Mehdi Mehrabi

Mehdi Mehrabi obtained his B.Eng. in Mechanical Engineering (Heat and Fluid Flow) in 2006 and his M.Eng.  in Mechanical Engineering (Energy Conversion) in 2011, both from Urmia University, Urmia, Iran, and his Ph.D. in Mechanical Engineering from the University of Pretoria, South Africa in 2015. He joined the Department of Mechanical and Aeronautical Engineering at the University of Pretoria, South Africa as a Senior Lecturer in 2017. He is a member of the Clean Energy Research Group and his research interests include convection heat transfer, multi-objective optimization techniques, application of artificial intelligence techniques for modeling heat transfer processes, clean and renewable energy and thermophysical properties of nanofluids.

Josua Petrus Meyer

Josua P. Meyer is Professor and Head of the Department of Mechanical and Aeronautical Engineering and Chair of the School of Engineering at the University of Pretoria. His research field is convective heat transfer in which he has published more than 600 scholarly articles, conference papers and book chapters. He has received various international awards for his research. According to the Essential Science Indicators of the ISI Web of Knowledge he is ranked among the top 1% of the world in engineering in all three evaluation fields, which are citations, number of papers and citations per paper. He is/was the editor, lead editor and associate editor of various prominent international heat transfer journals.