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RISS 인기검색어
- 검색키워드
- 저자 : Jeong Hwa Oh (검색결과 1 건)
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Jeong Hwa Oh 忠南大學校 大學院 2019 국내석사
ABSTRACT Heat transfer characteristics of a coil type heat exchanger with variation of shape and mass flow rate Jeong-Hwa Oh Department of Aerospace Engineering, Graduate School Chungnam National University Daejeon, Korea (Supervised by Professor Young-Sung Ko) Most of heat transfer study for the coil type heat exchanger were carried out using air as a flow media. therefore, in this study heat transfer characteristics of a coil type heat exchanger using helium gas with various type of shape and flow rate was investigated experimentally. Heat exchanger was heated by using a water bath. The experimental condition were 28,000 < Re < 90,000 and 0.044 < d/D < 0.15. The results are summarized as follows. (1) To validate experimental equipment, air was used as a flow media and experimental results were compared with existing air data in the range of 30,000 < Re < 90,000. Observed maximum discrepancy was within 14%. (2) For 28,000 < Re < 40,000, heat transfer rate is increased with increasing curvature ratio. However, beyond this Reynolds number, effect of the curvature ratio decreases, and when Reynolds number is more than 50,000, the curvature effect hardly appears. It is believed that as the Reynolds number increases, the momentum in the longitudinal direction of the spiral tube is increased, but the effect of the curvature is decreased due to reducing centrifugal effect. (3) For Re < 35,000, heat transfer rate of a coil type heat exchanger using air and helium does not show a large differences. However, for 35,000 < Re < 63,000, helium heat exchanger shows maximum of 18% higher heat transfer rate than air heat exchanger. It is recommended that when designing helium coil type heat exchanger - For Re > 50,000, curvature effect on heat transfer rate is neglectable - For Re > 35,000, heat transfer rate is higher than based on air data
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