Comparative study of flow boiling heat transfer and frictional pressure gradient of a non-azeotropic mixture of R-1270/R-600a, and R-22 in a smooth horizontal tube

Abstract

Generation of air conditioners’ refrigerants suitable for countries with high ambient temperatures has become a necessity. Along with that, in this work, a non-azeotropic mixture (R-1270/R-600a), which is suitable for high ambient temperatures, composed of propylene (85%) and isobutane (15%) by mass was proposed. The heat transfer coefficient (HTC) and the frictional pressure gradient (FPG) of the boiling flow of this mixture were experimentally measured in a smooth horizontal tube and compared with that of R-22. Besides, the effect of mass flux (76.51, 95.64, and 114.76 kg/m2. s) and vapor quality (ranged from 0.1 to 0.7) on HTC were investigated. As a result, HTCs varied proportionally to both the vapor quality, and saturation pressure. Whereas, FPGs changed proportionally to vapor quality and inversely to saturation pressure. Additionally, at mass flux of 95.6 kg/m2 s, HTCs, and FPGs were enhanced by (19.04–67.32%), and (14.55–103.76%), respectively, w.r.t R-22. Moreover, the experimental results of HTCs and FPGs showed a good agreement with those of empirical correlations prediction.

Keywords

• R-1270/R-600a non-azeotropic mixture
• R-22
• Heat transfer coefficient
• Frictional pressure gradient