Flow boiling characteristics of R134a and R245fa mixtures in a vertical circular tube

Abstract Considerable attention has recently been given to making new refrigerant mixtures for applications such as organic Rankine cycles (ORCs). In this study, the flow boiling of a mixture of R134a and R25fa was visualized. Mixtures at different molar fractions ranging from pure R245fa to a molar concentration up to 50% R245fa–50% R134a were chosen. The ranges of mass flux and heat flux were 300–800 kg/m2 s and 1–69 kW/m2, respectively. A circular glass tube with a 3-mm inner diameter and 200-mm length was used. In each case, different flow regimes were recognized, such as bubbly flow, slug flow, and annular flow. Throat-annular flow was observed in limited cases but not in all mixtures. The heat transfer coefficient in each case was analyzed carefully. Degradation of the heat transfer coefficient due to the mass transfer resistance is discussed, and the heat transfer coefficient of the mixtures is shown to be lower than that of the original pure refrigerants. The heat transfer coefficient data were compared to predictive methods in the literature, and a modified version of correlations is proposed for the mixture of R134a and R245fa.

[1]  J. C. Chen.  Correlation for Boiling Heat Transfer to Saturated Fluids in Convective Flow , 1966 .

[2]  K. Gungor,et al.  A general correlation for flow boiling in tubes and annuli , 1986 .

[3]  J. Thome,et al.  Experimental study on flow boiling heat transfer of multiport tubes with R245fa and R1234ze(E) , 2013 .

[4]  R. Revellin,et al.  Flow boiling characteristics of R-245fa in a minichannel at medium saturation temperatures , 2014 .

[5]  T. Karayiannis,et al.  Flow boiling of R245fa in 1.1 mm diameter stainless steel, brass and copper tubes , 2014 .

[6]  V. Gnielinski.  New equations for heat and mass transfer in turbulent pipe and channel flow , 1976 .

[7]  Bing-Chwen Yang,et al.  Subcooled flow boiling heat transfer of R-134a and bubble characteristics in a horizontal annular duct , 2000 .

[8]  Rémi Revellin,et al.  Flow pattern characterization for R-245fa in minichannels: Optical measurement technique and experimental results , 2013 .

[9]  S. Wongwises,et al.  Two-phase flow patterns and heat transfer characteristics of R134a refrigerant during flow boiling in a single rectangular micro-channel , 2015 .

[10]  Björn Palm,et al.  Flow boiling visualization in a vertical circular minichannel at high vapor quality , 2006 .

[11]  Li Zhao,et al.  A comparative study of pure and zeotropic mixtures in low-temperature solar Rankine cycle , 2010 .

[12]  K. Gungor,et al.  Simplified general correlation for saturated flow boiling and comparisons of correlations with data , 1987 .

[13]  R. Winterton,et al.  A general correlation for saturated and subcooled flow boiling in tubes and annuli, based on a nucleate pool boiling equation , 1991 .

[14]  S. Wongwises,et al.  An experimental investigation of flow boiling heat transfer of R-134a in horizontal and vertical mini-channels , 2013 .

[15]  R. Radermacher,et al.  A study of flow boiling heat transfer with refrigerant mixtures , 1989 .

[16]  R. Akasaka,et al.  A Thermodynamic Property Model for the R-134a/245fa Mixture , 2014 .

[17]  R. Revellin,et al.  Experimental investigation of R-245fa flow boiling in minichannels at high saturation temperatures: flow patterns and flow pattern maps , 2014 .

[18]  S. Wongwises,et al.  Flow pattern and heat transfer characteristics of R-134a refrigerant during flow boiling in a horizontal circular mini-channel , 2010 .

[19]  A. Levy,et al.  Flow boiling of binary solution in horizontal tube , 2010 .

[20]  W. Wagner,et al.  The GERG-2008 Wide-Range Equation of State for Natural Gases and Other Mixtures: An Expansion of GERG-2004 , 2012 .

[21]  L. Rossetto,et al.  R134a Flow Boiling Heat Transfer and Pressure Drop inside a 3.4 mm ID Microfin Tube , 2014 .

[22]  R. Radermacher,et al.  Horizontal flow boiling heat transfer experiments with a mixture of R22/R114 , 1989 .

[23]  Ravi Kumar,et al.  Heat transfer characteristics and flow pattern during two-phase flow boiling of R134a and R407C in a horizontal smooth tube , 2014 .

[24]  John R. Thome,et al.  High heat flux flow boiling in silicon multi-microchannels – Part II: Heat transfer characteristics of refrigerant R245fa , 2008 .

[25]  E. Schlünder,et al.  Horizontal flow boiling experiments of saturated pure components and mixtures of R846-R12 at high pressures , 1992 .

[26]  Gherhardt Ribatski,et al.  Flow boiling heat transfer of R134a and R245fa in a 2.3 mm tube. , 2010 .

[27]  P. B. Whalley,et al.  Flow patterns in vertical two-phase flow , 1985 .

[28]  J. Thome,et al.  Saturated flow boiling heat transfer and critical heat flux in small horizontal flattened tubes , 2012 .

[29]  F. Hormozi,et al.  Application of thermodynamic models to estimating the convective flow boiling heat transfer coefficient of mixtures , 2014 .

[30]  C. Liao,et al.  Experimental study of forced convective boiling for non-azeotropic refrigerant mixtures R-22/R-124 in horizontal smooth tube , 2009 .

[31]  M. Fernandino,et al.  Experimental results on boiling heat transfer coefficient, frictional pressure drop and flow patterns for R134a at a saturation temperature of 34°C. , 2014 .

[32]  John R. Thome,et al.  Flow boiling heat transfer of R134a, R236fa and R245fa in a horizontal 1.030 mm circular channel , 2009 .

[33]  Shan K. Wang,et al.  Handbook of Air Conditioning and Refrigeration , 1993 .

[34]  Maoqiong Gong,et al.  Experimental study on saturated flow boiling heat transfer of R170/R290 mixtures in a horizontal tube , 2010 .

[35]  Bruno Vanslambrouck,et al.  Potential of zeotropic mixtures as working fluids in organic Rankine cycles , 2012 .

[36]  M. Kazimi,et al.  Nuclear Systems Volume I: Thermal Hydraulic Fundamentals, Second Edition , 2011 .

[37]  Matthias Wettermann,et al.  Flow boiling heat transfer characteristics of wide-boiling mixtures , 2000 .

[38]  Markus Preißinger,et al.  Zeotropic mixtures as working fluids in Organic Rankine Cycles for low-enthalpy geothermal resources , 2012 .