Heat transfer characteristics in the U-bend of a microfin tube evaporator using R-407C
- Sung Kyun Kwan Univ., Suwon (Korea, Republic of)
This work experimentally investigated the effects of parameters on the heat transfer coefficients in the U-bends and the straight sections of smooth and microfin tube evaporators using R-22 and R-407C refrigerants. The parameters were mass flux of 200 and 400 kg/m{sup 2}{center_dot}s, heat flux of 6 and 12 kW/m{sup 2}, and inlet quality of 0.1 and 0.2. The system pressure was 0.65 MPa. The apparatus consisted of a test section of four straight sections and three U-bends, preheater, condenser, refrigerant pump, mass flowmeter, and other equipment. One-third of the downstream straight section was affected by the upstream U-bend due to the centrifugal force and mixing of two-phase flow. The average heat transfer coefficients in the U-bends were higher by 4% to 33% than those in the straight sections. The average heat transfer coefficients in the microfin tube were higher by 19% to 49% in the straight section and by 33% to 69% in the U-bend than those in the smooth tube. The average heat transfer coefficients for R-407C were lower by 33% to 41% for the smooth tube and by 17% to 29% for the microfin tube than those for R-22.
- Sponsoring Organization:
- Korea Ministry of Education (Korea)
- OSTI ID:
- 687675
- Report Number(s):
- CONF-980650--
- Country of Publication:
- United States
- Language:
- English
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