Experimental study of inverted annular film boiling in a vertical tube cooled by R-134a

• Published in: International journal of multiphase flow Vol. 37; no. 1; pp. 67 - 75
• Main Authors: Nakla, Meamer El, Groeneveld, D.C., Cheng, S.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2011; Elsevier
• Subjects: Annular; Applied sciences; Energy; Energy. Thermal use of fuels; Equivalence; Exact sciences and technology; Film boiling; Flux; Heat transfer; Hot-patch techniques; Inlets; Inverted annular film boiling; Theoretical studies. Data and constants. Metering; Trends; Tubes; Inverted annular film boiling; Hot-patch techniques; Subcooling; Critical heat flow; Heat flow; Film boiling; Heat transfer coefficient; Experimental study; Refrigerant fluid; Heat transfer; Vertical tube
• ISSN: 0301-9322; 1879-3533
• DOI: 10.1016/j.ijmultiphaseflow.2010.08.006

► Heat transfer coefficient vs. quality curve can be divided into four regions depending on the flow regime. ► Film boiling heat transfer coefficient increases with increasing pressure and mass flux. ► Heat flux has weak effect on film boiling heat transfer coefficient. ► Inlet subcooling affects heat transfer coefficient just downstream of CHF location. An experimental investigation of inverted annular film boiling heat transfer has been performed for vertical up-flow in a round tube. The experiments used R-134a coolant and covered a pressure range of 640–2390 kPa (water equivalent range: 4000–14,000 kPa) and a mass flux range of 500–4000 kg m −2 s −1 (water equivalent range: 700–5700 kg m −2 s −1). The inlet qualities of the tests ranged from −0.75 to −0.03. The hot-patch technique was used to obtain the subcooled film boiling measurements. It was found that the heat transfer vs. quality curve can be divided into four different regions, each characterized by a different mechanisms and trends. These regions are dependent on pressure, mass flux and local quality. A detailed examination of the parametric trends of the heat transfer coefficient with respect to mass flux, inlet quality, heat flux and pressure was performed; reasonably good agreement between observed trends and those reported in the literature were noted.