HFC404A condensation inside a 4mm horizontal smooth tube: comparison with the long-term low GWP substitutes HC290 (Propane) and HC1270 (Propylene)

This paper presents the comparative analysis of HFC404A and its low GWP substitutes HC290, and HC1270 in saturated vapour condensation inside a 4 mm ID horizontal smooth tube. The experimental tests were carried out at 30, 35, and 40°C of saturation temperatures, with refrigerant mass flux in the range 75 - 800 kg m-2s-1 at decreasing vapour quality. A transition point from gravity-dominated and forced convection condensation was found for an equivalent Reynolds number around 10000. The experimental heat transfer coefficients in the forced convection condensation regime were very well predicted by the Akers et al. (1959) model, whereas the Friedel (1979) correlation was able to reproduce the frictional pressure drop data in the whole experimental range. HC290 and HC1270 exhibit heat transfer coefficients higher and frictional pressure drops lower than those of HFC404A; therefore both the HC refrigerants seem to be very promising as long-term low GWP substitutes for HFC404A.