碩士 / 國立成功大學 / 機械工程學系碩博士班 / 94 / The finite difference method in conjunction with the least-squares scheme and experimental temperature data is proposed to predict the average heat transfer coefficient, heat rate, and fin efficiency on a vertical annular circular fin of annular-finned tube heat exchangers for various fin spacings and air speeds. The heat transfer coefficient on this annular circular fin is assumed to be non-uniform. Thus the whole plate fin is divided into several sub-fin regions in order to predict the average heat transfer coefficient and fin efficiency from the knowledge of the measured temperatures. The unknown heat transfer coefficient on each sub-fin region can be assumed to be constant. The results show that the average heat transfer coefficient increases with increasing the fin spacing, and the fin efficiency decreases with increasing the fin spacing in natural convection. The average heat transfer coefficient and fin efficiency can approach their corresponding asymptotical value obtained from a single annular circular fin for the fin spacing above a certain value. The heat rate seems to increase with increasing the fin spacing. The present estimates of the average heat transfer coefficient under the condition of the isothermal situation are slightly higher than those obtained from the correlation recommended by current textbooks for various fin spacing. This phenomenon can result from the simultaneous consideration of the convection and radiation heat transfer coefficients in the present study. The average heat transfer coefficient increases with increasing the air speed, and the fin efficiency decreases with increasing the air speed for various fin spacing in forced convection. The average heat transfer coefficient increases with increasing the fin spacing for a fixed air speed. It can also approach its corresponding asymptotical value obtained from a single annular circular fin for the fin spacing above a certain value. However, the effect of the fin spacing on the fin efficiency is very small. The heat rate increases with the air speed for a fixed fin spacing. However, the effect of the fin spacing on the heat rate is small for a fixed air speed. In order to evidence the reliability of the present inverse scheme, the present estimated results of the average heat transfer coefficient in forced convection agree with the experiment results. Thus the reliability of the present inverse scheme is expected.
| Identifer | oai:union.ndltd.org:TW/094NCKU5490064 |
| Date | January 2006 |
| Creators | Wei-Lun Hsu, 許維倫 |
| Contributors | Han-Taw Chen, 陳寒濤 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 88 |
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