博士 / 國立清華大學 / 動力機械工程學系 / 89 / The airside performance of slit fin-and-tube heat exchangers is investigated in this dissertation. The heat transfer performance for slit-fin type is higher than that of plain-fin or wavy-fin type. The friction performance for slit-fin type is lower than that of louver-fin type. Performance data of the slit fin-and-tube heat exchangers with small diameter tubes are very important. Benefits of heat exchangers with smaller diameter tubes include the smaller form drag caused by the tubes and the higher heat transfer coefficients due to smaller hydraulic diameters.
Test results indicate that the airside performance for compact slit-fin geometry is relatively independent of the numbers of tube row and fin pitch. The results are quite different from those in previous studies [26] because of a smaller slit breadth in the present study. Test results of the slit-fin type are compared with those of the louver-fin and plain-fin type by various methods. The relevant airside performance of the interrupted surfaces (including louver and slit fin type) is invariably superior to that of plain-fin type. However, it should be pointed out that this advantage decreases with fin pitch and the Reynolds number. An updated correlation of the airside performance resulting from 56 test samples is proposed for the slit-fin type. The mean deviations are 7.26% and 7.18% for the proposed heat transfer correlation and the frictional correlation, respectively.
Airside performance for three new slit fin-and-tube heat exchangers under dehumidifying conditions is investigated. The effects of the number of tube rows, fin pitch, and the inlet relative humidity on the airside performances are analyzed. For type I slit-fin type with a small louver angle (convex-louver configuration), the results show that the sensible heat transfer performances are relatively independent of fin pitch. However, for type III slit-fin type with the smallest distance between adjacent slits, a decrease in the heat transfer performance for N（row number）= 1 and Fp（fin pitch）= 1.81mm is observed. This phenomenon is related to the “wake effect” caused by the slit geometry. A correlation is proposed for the slit-fin configuration, the mean deviations of the proposed heat transfer and friction correlation are 8.0% and 8.1%, respectively.
| Identifer | oai:union.ndltd.org:TW/089NTHU0311106 |
| Date | January 2001 |
| Creators | Lee, Wei-Song, 李煒松 |
| Contributors | Prof. Sheu, Wen-Jenn, 許文震 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 121 |
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