Boiling heat transfer of new zeotropic mixtures

The aim of the present work is to investigate the heat transfer performance of non-azeotropic ternary low global warming potential (GWP) mixtures when vaporizing inside two channels: a 8,0 mm inner diameter tube and a 0,96 mm inner diameter channel. The tested mixtures are R455A, which is a ternary blend of R32, R1234yf and R744 (21,5/75,5/3,0% by mass composition), and R452B, which is a ternary blend of R32, R1234yf and R125 (67,0/26,0/7,0% by mass composition). While R455A presents a GWP value equal to 146 and a temperature glide of about 10 K, R452B is characterized by higher GWP (equal to 676) but lower temperature glide (about 1 K). Results demonstrate that an increased temperature glide leads to higher mass transfer resistance which penalizes the heat transfer of the zeotropic mixtures during vaporization and must be taken into account when extending available correlations developed for pure fluids to non-azeotropic blends.