Experimental evaluation of flow boiling heat transfer coefficient of low-GWP non-azeotropic mixture R454C in a 6.0 mm stainless- steel horizontal tube

This paper presents an experimental study on flow boiling heat transfer of HFC/HFO blend R454C, a low GWP (148) non-azeotropic refrigerant having a not negligible glide (4.2 °C at 0 °C). R454C is a suitable alternative to R404A (GWP=3943) for low and average temperature applications, such as multipack refrigeration systems, condensing units and light commercial refrigeration units. The experiments are performed in a smooth circular horizontal stainless-steel tube with an internal diameter of 6.0 mm. Trends of the heat transfer coefficient are investigated under different operating parameters, such as mass flux (from 150 to 600 kg/m2s), bubble saturation temperature (from 25 to 55 °C) and heat flux (from 10 to 20 kW/m2), from the occurrence of boiling up to the dry-out. Finally, the experimental data are compared to R404A data obtained with the same test facility and at the same operating conditions, highlighting their performance differences.