| Title |
Effect of Refrigeration Oil on the Condensation Heat Transfer for Alternative Refrigerant in Microfin Tube with a U-bend |
| Keywords |
Condensation heat transfer ; 응축열전달 ; R-407C, Microfin tube ; 마이크로핀관),U-bend ; 곡관부 ; POE oil |
| Abstract |
The present study experimentally investigated the effect of refrigeration oil on the condensation heat transfer for R-407C and R-22 in a microfin tube with a U-bend. POE oil (74.1 mm2/s, 40℃) and mineral oil (62.5 mm2/s, 40℃) were used for R-407C and R-22 respectively. Experimental parameters were an oil concentration from 0 to 5%, a mass flux from 100 to 400 kg/m2s and an inlet quality from 0.5 to 0.9. The enhancement factors for both R-22 and R-407C refrigerants at the first straight section decreased continuously as the oil concentration increased. They decreased rapidly as the mass flux decreased and the inlet quality increased. The heat transfer coefficients in the U-bend showed the maximum at the 90°position. The heat transfer coefficients at the second straight section within the dimensionless length of 48 were larger by a maximum of 33% than the average heat transfer coefficient at the first straight section. |