碩士 / 中國文化大學 / 材料科學與製造研究所 / 88 / The present study had tested the fin-and-tube heat exchangers with slit fin and wavy fin geometry. Total of sixteen different specification of heat exchangers were tested both in open type wind tunnel and close type wind tunnel. The effect of the number of row, fin pitches and fin pattern of the air-side heat and mass transfer performance were experimentally investigated. The test results are compared and presented as Colburn j factor and fanning friction factor f against Reynolds number ReDc based on the fin collar diameter Dc in the range of 300 to 10,000 in open type wind tunnel and 500 to 7,000 in close type wind tunnel, respectively.
In open type wind tunnel, the test results indicated that the heat transfer performance increase as the fin pitch decreasing for one row configuration. However, when row number over than four, the effect of fin pitch on the heat transfer performance is reversed. In addition to the effect of fin pitch, the heat transfer performance decrease with increasing the number of tube row. But the friction characteristic is relatively independent of the number of tube row. Based on the present results and those from the former investigation by Mirth and Ramadhyani, a general correlation is proposed to describe the airside performance of wavy fin configuration, mean deviation of the proposed heat transfer correlation are —27.2% and 2.1%, respectively.
In close type wind tunnel, the test results indicated that the heat transfer performance is relatively independent of inlet relative humidity. However, when ReDc > 3,000 with smaller fin pitch, the heat transfer performance slightly increase with inlet relative humidity. The test results showed that the heat transfer performance in close type wind tunnel had a similar trend compared with open type wind tunnel. Friction factor f increase as the decreasing of the fin pitch, and also as the function of the humidity of the inlet conditions in one row configuration. In two-row configuration of slit fin geometry, the friction characteristics showed as the function of the inlet relative humidity under high frontal velocity conditions.
Total of five different coating of heat exchangers were tested both in open type wind tunnel and close type wind tunnel. One fin-and-tube heat exchangers with slit fin was not hydrophilic coated, and other four exchangers were coated. The test results showed that the heat transfer performance and friction factor f are to be similar. The pressure is higher than others on the one heat exchanger without hydrophilic coating .
| Identifer | oai:union.ndltd.org:TW/088PCCU0159007 |
| Date | January 2000 |
| Creators | Li-Cheng Chen, 陳立錚 |
| Contributors | Wei-Han Tao, 陶惟翰 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 79 |
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