Thermal-hydraulic characterization of R513A during flow boiling inside a 6.0 mm horizontal tube, comparison with R134a and development of a new correlation

• Published in: International journal of refrigeration 2023-11, Vol.155, p.47-57
• Main Authors: Mauro, A.W., Pelella, F., Viscito, L.
• Format: Article
• Language: English
• Subjects: Assessment of correlations; Chute de pression diphasique; Flow boiling; Frigorigènes à faible PRP; Low-GWP refrigerants; R513A; Two-phase pressure drop; Ébullition en écoulement; Évaluation des corrélations
• ISSN: 0140-7007; 1879-2081
• DOI: 10.1016/j.ijrefrig.2023.08.018

•Flow boiling heat transfer and pressure drop data for R513A.•HTC shows both nucleative and convective behavior with operating conditions.•Pressure drop increases with mass flux and decreases with saturation temperature.•New composite prediction method (MAPE = 25.3%) for heat transfer coefficient.•Frictional pressure gradients well predicted by Friedel correlation (MAPE = 13.8%). This paper presents two-phase heat transfer coefficient and pressure drop data of refrigerant R513A, a new azeotropic mixture conceived as possible alternative to R134a for medium temperature small-size refrigeration systems. All the experiments were performed in a commercial horizontal stainless-steel tube having an internal diameter of 6.0 mm and an outer diameter of 8.0 mm. The channel heating was obtained through DC current and Joule effect. The effect of the main operating parameters in terms of mass flux (from 150 to 500 kg/m2s), heat flux (from 5.0 to 40 kW/m2), saturation temperature (from 30 to 50 °C) and vapor quality (from the onset of boiling up to the dry-out occurrence) was analyzed and discussed for the heat transfer coefficient values, finding that both convective and nucleate boiling were significant contributions. The same ranges of mass flux and saturation temperature were also applied to frictional pressure gradient trends with vapor quality, taken in adiabatic conditions. The thermo-hydraulic performances were then compared with those of R134a, obtaining lower heat transfer coefficients and very similar pressure gradients. Finally, the collected experiments were assessed with values predicted from the most quoted correlations available in literature. A new composite method for nucleate-dominant or convective-dominant mechanisms was proposed for the evaluation of the heat transfer coefficient, with a mean absolute error of 25.3%, whereas the frictional pressure gradient values were well predicted with the Friedel correlation, that provides a mean absolute error of 13.8%.