Flow pattern, heat transfer and frictional pressure drop investigation of R365mfc condensation in a micro-structured corrugated gap with mixed angles

Abstract

• Experimental visualization results for condensation of R365mfc. • Mixed 27°/63° plate gap with microstructure are used. • Analysis of flow path, flow patterns, heat transfer and frictional pressure drop. • Comparison between empirical correlations in literature and experimental data. • A new heat transfer model based on condensation mechanism is developed. This paper experimentally investigates the condensation of R365mfc in a micro-structured corrugated gap with mixed 27°/63° chevron angle. The condensation mechanisms are analyzed by visualizing the flow patterns through a transparent polyurethane plate, and the measurements are carried out at saturation pressure 1.12 bar ( p red = 0.034), mass flux between 6.14 and 44.56 kg/m 2 s and a mean vapor quality from 0.58 to 0.92. Six flow patterns are identified as the mass flux is decreasing: annular flow, wispy-annular flow, partial film flow, smooth liquid film flow, churn flow and slug flow. A flow pattern map is drawn as a function of mass flux and vapor quality, G ≈ 20 kg/m 2 s is considered as a transition, after which no partial film flow is observed. The combination of G ≈ 20 kg/m 2 s and x ≈ 0.83 is the transition of the condensation mechanism between gravity-controlled condensation and a combination of gravity-controlled and convection condensation. The frictional pressure drop increases with the increase of mass flux and vapor quality and is not influenced by flow patterns. The experimental heat transfer coefficients and frictional pressure drop are compared with the prediction results calculated by the correlations in the literature and a new heat transfer model is developed, which includes the individual heat transfer models of a gravity-controlled regime, a transition regime and a shear force-controlled regime as well as the transition criterion between these regimes. The new model predicts 97% of experimental data within ±30%, the root mean square error and the mean absolute error is 12.7% and 9% respectively.