Convective boiling of R-123 on enhanced-tube bundles

Abstract

The current paper presents the experimental investigation of the heat transfer performance and effect of tube pitch on highly enhanced surfaced tube bundles. The fluid-tube combination used was R-123-TBIILP. Three pitch-to-diameter ratios were studied 1.167, 1.33, and 1.5; all with a staggered triangle arrangement. Twenty enhanced tubes were used in each bundle; the tube outer diameter and length are 19.05 mm (3/4 in.) and 1 m (39.36 in.), respectively. Three input variables were studied: heat flux (5–60 kW/m2), mass flux (15–55 kg/m2 s), and thermodynamic quality (10–70%). The test saturation temperature was 14.44 °C. A local method employing the EBHT technique was implemented in data reduction. All tube bundles showed strong dependency on heat flux and some dependency on quality. When compared to the pool boiling performance, the smallest P/D bundle was lower while the other two showed closer performance. Tube dry-out at high quality was observed for the smallest bundle (P/D 1.167). The dry-out phenomenon was characterized by performance degradation to that of a smooth tube. The P/D 1.33 bundle is the optimum bundle as it shows quite similar behavior to the P/D 1.5 bundle while operating at a lower refrigerant charge.