Two-Phase Frictional Pressure Drop and Flow Boiling Heat Transfer for R245fa in a 2.32-mm Tube

Abstract

Experimental two-phase frictional pressure drop and flow boiling heat transfer results are presented for a horizontal 2.32-mm ID stainless-steel tube using R245fa as working fluid. The frictional pressure drop data was obtained under adiabatic and diabatic conditions. Experiments were performed for mass velocities ranging from 100 to 700 kg m⁻² s⁻¹, heat flux from 0 to 55 kW m⁻², exit saturation temperatures of 31 and 41°C, and vapor qualities from 0.10 to 0.99. Pressures drop gradients and heat transfer coefficients ranging from 1 to 70 kPa m⁻¹ and from 1 to 7 kW m⁻² K⁻¹ were measured. It was found that the heat transfer coefficient is a strong function of the heat flux, mass velocity, and vapor quality. Five frictional pressure drop predictive methods were compared against the experimental database. The Cioncolini et al. (2009) method was found to work the best. Six flow boiling heat transfer predictive methods were also compared against the present database. Liu and Winterton (1991), Zhang et al. (2004), and Saitoh et al. (2007) were ranked as the best methods. They predicted the experimental flow boiling heat transfer data with an average error around 19%.

Acknowledgments

The authors gratefully acknowledge the financial support under contract numbers 05/60031-0, 06/52089-1, and 07/53950-5 given by FAPESP (The State of São Paulo Research Foundation, Brazil). The technical support given to this investigation by José Roberto Bogni is appreciated and recognized.

Gherhardt Ribatski is a professor in the Department of Mechanical Engineering at the University of São Paulo (USP), Brazil. He received his Ph.D. at the University of São Paulo, Brazil, in 2002. He was a postdoctoral researcher in the Department of Mechanical and Industrial Engineering at the University of Illinois at Urbana–Champaign and a postdoctoral researcher in the Laboratory of Heat and Mass Transfer at the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland. His research interests cover nanofluids, pool boiling, falling-film evaporation and condensation, two-phase flow, boiling and condensation of external and internal flows, and convective evaporation and condensation in micro-scale channels. He has published two book chapters and more than 70 papers on two-phase flow and heat transfer.

Cristiano B. Tibiriçá has bachelor's and master's degrees in mechanical engineering from University of São Paulo (USP), Brazil. He started his Ph.D. in 2007, at USP, and worked during one year as a doctoral assistant at the Laboratory of Heat and Mass Transfer at the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, as part of an interchange doctoral program. His research interests cover two-phase flow, boiling and condensation of external and internal flow, and convective evaporation and condensation in micro-scale channels. He has published more than 10 papers on two-phase flow during the first two years of his Ph.D. program.