| Title |
Effect of Oil on Pool Boiling of Refrigerant on Enhanced Tubes having Different Pore Sizes |
| Keywords |
Enhanced tube ; 전열촉진관 ; Refrigerant-oil mixture ; 냉매-오일 혼합물 ; Pool boiling ; 풀비등 ; R-123, Mineral oil ; 광유 |
| Abstract |
The effect of enhanced geometry(pore diameter, gap width) is investigated on the pool boiling of R-123/oil mixture for the enhanced tubes having pores with connecting gaps. Tubes with different pore diameters(and corresponding gap widths) are specially made. Significant heat transfer degradation by oil is observed for the present enhanced tubes. At 5% oil concentration, the degradation is 26 to 49% for4.4℃. The degradation increases 50 to 67% for26.7℃. The heat transfer degradation is significant even with small amount of oil(20 to 38% degradation at 1% oil concentration for4.4℃), probably due to the ac-cumulation of oil in sub-tunnels. The pore size(or gap width) has a significant effect on the heat transfer degradation. The maximum degradation is observed for0.20mm tube at 4.4℃, and for0.23mm tube at26.7℃. The minimum degradation is observed for0.27mm tube for both saturation temperatures. It appears that the oil removal is fa-cilitated for the larger pore diameter(along with larger gap) tube. The highest heat transfer coefficient with oil is obtained for0.23mm tube, which yielded the highest heat transfer coefficient for pure R-123. The heat transfer degradation increases as the heat flux decreases. |