碩士 / 國立中山大學 / 機械工程學系 / 87 / Heat transfer enhancement is one of the most important objectives for heat exchanger design. However, the coefficient of heat exchanger mainly depends on the performance of fin. In the present study, the local convective heat transfer coefficients on the plate fin of a fin-and-tube heat exchanger with different geometrical parameters, including fin pitch of S=D/3.8, D/4.4 and D/5.6, transverse tube pitch of S=2.0D, 2.5D and 3.0D, longitudinal tube pitch of L=1.5D, 2.0D and 2.5D, and Reynolds number range of 2000 to 9300 are studied and described.
Experimental models of heat exchangers are constructed according to similarity principles. Complete distribution of local heat transfer coefficients are measured over the full surface of the plate fin of a fin-and-tube heat exchanger by the transient heat transfer method with thermochromic liquid crystal used as the surface thermometer. Software, LCIA (Liquid Crystal Image Analysis), is used to obtain the temporal history of the surface temperature used to determined the local heat transfer coefficient.
The results show that the heat transfer coefficient of the plate fin increases with the Reynolds number and the fin pitch. The heat transfer coefficients of the plate fin with transverse tube pitch S=2.0D is similar to the case with S=2.5D, and is larger than the case with S=3.0D. The heat transfer coefficients of the plate fin with longitudinal tube pitch L=1.5D is similar to the case with L=2.0D, and is smaller than the case with L=2.5D. Therefore, there should exist an optimum geometry of the plate fin for a fin-and-tube heat exchanger.
| Identifer | oai:union.ndltd.org:TW/087NSYSU489006 |
| Date | January 1999 |
| Creators | Yen Chang Hsun, 顏昌旭 |
| Contributors | Yang Ru, 楊儒 |
| 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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