碩士 / 國立交通大學 / 機械工程研究所 / 85 / In this research report, seven convex-louver fin condensers and seven wavy fin condensers with indentical tube diameter (Do), longitudinal and transverse tube pitch (Pl, Pt) but differential numbe rof tube rows (N) and fin pitch (Fp) were tested and analyzed for the heat transfer and pressure drop characteresties. Results are presented with the Colburn j factor and Fanning factor f against Reynolds number (ReDc) based on the tube collar diamater (Dc) in the range of 300 to 8,000. Experimental datas show that the effect of the number of tube rows does not influence the f factor for both convex-louver and wavy fin geometry when ReDc＞1,000 and the effect of Fp＝2.54mm on j factor variation is also very small. For the case of Pf＝1.21mm, the j factors decrease with the increasing number of tube rows when ReDc＜2,000 but the effect of Fp is negeligible when ReDc＞2,000 for the reason that the effect of tube rows starts to influence the air passing the condenser. The vortices are weakened so that the fin pitch might not disturb the j factors anymore.
This study compare not only the performances of the j and f factors but also the performances of area and volume. The results show that the performace of convex-louver fin is higher than that of wavy fin with the expection that for the case at lower Reynolds number with 4-row coils with Fp＝1.21mm for convex-louver fin. The reason of j factor drop off is that a recirculation region will be established in the "sheltered" area formed by the apex angle of the chevron, and that the trapped fluid in the "sheltered" area often can not eject to the main stream at low Reynolds number so that the thermal boundary layer will not fully develope.
The correclations of j and f factor for convex-louver and wavy fin geometries are abtained for condenser sizing problems with the pattern and parameters of the heat exchanger and the rate of heat transfer and air side pressure drops, the program can give the heat transfer area and the size of the condenser.
| Identifer | oai:union.ndltd.org:TW/085NCTU3489033 |
| Date | January 1997 |
| Creators | Tsai, Yu-Min, 蔡祐民 |
| Contributors | Lu, Ding-Chong, 盧定昶 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 90 |
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