An Experimental Investigation on R134a Evaporation inside an Internally Discrete Inclined Grooved Tube

Abstract

In this experimental study, heat transfer and pressure drop characteristics of R134a evaporating flow are investigated inside a horizontal internally grooved tube with discrete inclined grooves. The test evaporators are made of smooth and grooved copper tubes of 20 mm inner diameter. The length, width, and depth of grooves are 6, 2, and 0.5 mm, respectively, and the angle of the grooves with the tube centerline is 30°. The test conditions include mass flux in the range of 16.5 to 105 kg/m²s, vapor quality of 0.06 to 0.98, and heat flux of 3.5 to 25 kW/m². The experiment results show that the boiling heat transfer coefficient of R134a in the grooved tube is 1.25 to 1.65 times higher than that of the smooth one. The frictional pressure drop of R134a inside the grooved tube is 10% to 60% higher than the smooth tube. Moreover, by increasing mass flux, the heat transfer coefficient, and frictional pressure drop of R134a refrigerant inside horizontal smooth and grooved tubes increase as well. In conclusion, the energy performance of R134a evaporating flow inside the grooved tube is more efficient than that in the smooth tube regarding energy saving in most experiments.

Conflict of interest

The authors declare that there is no conflict of interest.

Additional information

Notes on contributors

Alireza Hojati

Alireza Hojati is a Ph.D. student in the School of Mechanical Engineering at the University of Tehran, Iran. His current research is on heat transfer enhancement in two-phase flows under supervision of Professor M.A. Akhavan-Behabadi and Dr. P. Hanafizadeh.

Mohammad Ali Akhavan-Behabadi

Mohammad Ali Akhavan-Behabadi is a Professor in the School of Mechanical Engineering at the University of Tehran, Iran. He received his Ph.D. from Indian Institute of Technology at Roorkee, India, in 1993. He has coauthored about 300 journal and conference publications. His research interests include experimental two-phase and single-phase convective heat transfer.

Pedram Hanafizadeh

Pedram Hanafizadeh is an Associate Professor in the School of Mechanical Engineering at the University of Tehran, Iran. He has a Ph.D. from the Sharif University of Technology, Iran. His current research interests include two-phase flow, fluid mechanics, and numerical simulation.

Mohammad Mahdi Ahmadpour

Mohammad Mahdi Ahmadpour is a researcher in the School of Mechanical Engineering at the University of Tehran, Iran. He received his M.Sc. degree in energy conversion field under supervision of Professor M.A. Akhavan-Behabadi. He currently works on the heat transfer enhancement in two-phase flows.