Effect of pore size on the nucleate pool boiling of structured enhanced tubes

Abstract

In this study, pool boiling test results are provided for the structured enhanced tubes having pores with connecting gaps. The surface geometry of the present tube is similar to that of Turbo-B. Three tubes with different pore size (0.20 mm, 0.23 mm and 0.27 ram) were manufactured and tested using R-11, R-123 and R-134a. The pore size which yields the maximum heat transfer coefficient varied depending on the refrigerant. For R-134a, the maximum heat transfer coefficient was obtained for the tube having 0.27 mm pore size. For R-11 and R-123, the optimum pore size was 0.23 mm. One novel feature of the present tubes is that their boiling curves do not show a 'cross-over' characteristic, which existing pored tubes do. The connecting gaps of the present tube are believed to serve an additional route for the liquid supply and delay the dry-out of the tunnel. The present tubes yield the heat transfer coefficients approximately equal to those of the existing pored enhanced tubes. At the heat flux 40 kW/m 2 and saturation temperature 4.40 C, the heat transfer coefficients of the present tubes are 6.5 times larger for R-11, 6.0 times larger for R-123 and 5.0 times larger for R-134a than that of the smooth tube

Experimental investigation of anodized/ spray pyrolysed nanoporous structure on heat transfer augmentation

“…The convective medium streaming over the surface is disrupted by nano structures on the surface. The capillary action of convective medium in the nano pores helps in achieving turbulence expeditiously [9][10][11]. The turbulent flow carries away more heat energy from the surface.…”

Insect-inspired breathing interfaces: investigating robustness of coating-free gas entrapping microtextured surfaces under pressure cycles

“…The mushroom-shaped (or doubly reentrant) features, could stabilize the intruding menisci of wetting liquids in 'metastable states' by trapping air in the microtexture, regardless of the wettability of the material. The DRC architecture has been extensively investigated for enhancing boiling nucleation [31][32][33][34] . In their pioneering contribution, Kim et al 32 inverted the DRC architecture to realize a doubly reentrant pillar (DRP) microtexture that can repel droplets of wetting liquids with surface tension as low as 10 mN/m (placed from the top) 16 .…”