博士 / 國立成功大學 / 機械工程學系 / 107 / The paper study is divided into two parts. Firstly, the influence of the variable louver angle of the louvered fin heat exchanger on the heat transfer enhancement is discussed, which is a passive heat transfer enhancement method. The other part is a active type heat transfer enhancement method with the electrohydrodynamic (EHD) technique, and this part is divided into two directions of wire and needle electrodes to explore on the influence of heat transfer enhancement of plate surface in the case of natural convection. Which are described as follows:
The optimization of the variable louver angle (Δθ) and initial louver angle (θi)for a louvered-fin heat exchanger was determined numerically using the conjugate gradient method. The area reduction ratio relative to a plain surface was the objective function to be maximized. A search for the optimal variable louver angle (Δθ) and initial louver angle (θi), in the ranges of +0°〈Δθ〈+4° and 18° 〈 θi 〈 30°, respectively, was performed. The results show that the maximum area reduction ratios are 48.5~55.2％ for the optimal design of (Δθ, θi) at ReH = 133~1199 (Uin = 1.0 ~ 9.0 m/s).
EHD is an active heat transfer enhancement method, so it is necessary to consider the power loss that occurs during heat transfer enhancement. Therefore, the net heat transfer enhancement per unit power consumption is defined to confirm the actual demand for an evaluated standard of heat transfer enhancement. An optimal analysis was carried out along with the conjugate-gradient method, where the objective function was defined as the heat transfer enhancement per input power, which is maximized by searching for the optimum electrode pitch (SL) and height (H) combination. A search for the optimum electrode pitch (SL) and electrode height (H), ranging from 50 mm〈 SL 〈 200 mm and 15 mm 〈 H 〈 55 mm, respectively, with V0 (14, 16, 18 and 20 kV) and ΔT (33, 53 and 73 K), was performed, respectively. This result shows that the maximum heat transfer enhancement per power consumption as well as the optimal electrode position are obtained.
| Identifer | oai:union.ndltd.org:TW/107NCKU5489022 |
| Date | January 2019 |
| Creators | Chun-ChungChen, 陳俊忠 |
| Contributors | Jiin-Yuh Jang, 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 | 148 |
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