HFC 404A boiling 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 HC290 (Propane), HC1270 (Propylene), and HFC404A during vaporisation inside a 4 mm smooth tube. The experimental tests were carried out at three different saturation temperatures (5, 10, and 20 °C) at increasing vapour quality up to incipient dryout to evaluate the specific contribution of heat flux, refrigerant mass flux, mean vapour quality, and saturation temperature (pressure). The heat transfer coefficients show a reduced sensitivity to vapour quality, particularly at low refrigerant mass flux, high heat flux, and saturation temperature (pressure), therefore nucleate boiling seems to be the prevailing heat transfer regime in the present experimental tests. Although an early onset of dryout might partially compromise the boiling heat transfer performance of HC290, both the HC tested seem to be very effective as long-term low GWP substitutes for HFC404A and HFC507A.