碩士 / 國立成功大學 / 機械工程學系 / 85 / The thermal-hydraulic characteristics of three different kind of finned-tube heat exchangers (test A, B and C) are studied numerically and experimentally. Tests A and B are circular finned-tubes, while test C is an elliptic finned-tube, which has the same perimeter as that of test B. The flow is assumed to be steady, three-dimensional and laminar. The numerical results for the streamline, isotherm, Nusselt number and fin efficiency are first presented at various frontal velocities (1∼5 m/s) for the case of isothermal fin assumption (i.e., the fin conductivity is infinite). The conjugate convective heat transfer in the flow field and heat conduction in the circular fins are also considered. Experiments were conducted in a steady-state induced draft wind tunnel.
The numerical result indicated that the pressure drop of circular finned-tube heat exchanger (test B) is 3.74 times of elliptic finned-tube heat exchanger (test C), while the heat transfer coefficient of circular finned-tube (test B) is 1.36 times of elliptic finned-tube (test C). The heat transfer coefficient per unit of pressure drop for test C is (elliptic finned-tube) is 2.5 times test B (circular finned-tube). The conjugate effect reduces the heat transfer conefficient about 6.0%∼10.7% for test B and 5.0%∼14.7% for test C. The one dimensional approximation (Schmidt method) overestimates the fin efficiency by about 2∼5%. The numerical results for the pressure drop are in excellent agreement with the experimental data; although both the calculated and experimental results of the average heat transfer coefficients are in the same order of magnitude, the numerical results overestimate the heat transfer coefficient by 80-100%.
| Identifer | oai:union.ndltd.org:TW/085NCKU3489052 |
| Date | January 1997 |
| Creators | 賴振田 |
| Contributors | 張錦裕 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 150 |
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