Experimental and analytical study on nucleate pool boiling heat transfer of R134a/R245fa zeotropic mixtures

摘要: Abstract In the present study, nucleate pool boiling heat transfer characteristics of zeotropic binary mixtures (R134a/R245fa) with different blending ratios, as well their pure components, were experimentally investigated in a visualized pressure vessel. For each test refrigerant, experiments performed on horizontal plain copper surface (10 mm × 10 mm) at same evaporating temperature 26 °C flux ranging from 1.2 kW/m2 to 360 kW/m2. The curves refrigerants subdivided into up four zones natural convection region bubble column according visualization results. slope curve coalescence was greater than that isolated region. onset (ONB) point obviously lagged behind namely, higher wall superheat required, which presented consistent variation glide. coefficient mixtures, although increasing increase flux, degraded compared corresponding ideal coefficient, except for some specific cases high flux. Based analysis degradation factors and additional mass resistance, process identified three stages due presence two inflection points, pseudo fully developed (P-FDNB) double (P-DB) point. P-DB stable certain value did not vary ratio. thermodynamic fluctuation theory introduced describe effect resistance calculation results showed good agreement experimental data.