A Study of Heat Sink Ability Enhancement in Natural Convection

• Main Authors: Cheng-Ming Hsu, 徐振民
• Other Authors: Cherng-Yuh Su
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/v83759

碩士 === 國立臺北科技大學 === 機電整合研究所 === 97 === In this study, the heat transfer of heat sink is improved by the chimney effect in natural convection is studied. The four types of heat sink- short plate fin, spin fin, short plate fin with long base and the down side part of extrusion case, were designed for the experiments. The chimney effect is attributed to the height of chimney, and the Gr number and the quantity of heat dissipation from free convection to the heat sink is enhanced. Because of this, the performance of heat sink is also improved. Besides the height of chimney, the space between fins is a key factor. In the experiment, it was found that the local heat transfer of narrow space between fins was increased , and the narrow one was better than the wide one about 8℃ at the chimney 80mm/30W. The experimental result of spine fins is similar with short plate fins when the spin fins are in vertical orientation. The experiment was exhibited that the smaller vertical space of aligned spin fins was better than the stagger about 1.3℃ for improving temperature at the chimney 80mm/30W. However, the spine fins oriented horizontal with vertical base, side vents of heat sink blocked and one way of air through the chimney, the position of array for the spine fin is another factor. Because of wake, the performance of aligned spine fin was inferior to the staggered when chimney was attached on. From the result, the aligned spine fin was worse than the staggered about 4℃ at chimney 120mm/30W. Though the ability of heat sink is improved by the chimney effect, it is not certainty to meet the expectancy in the efficiency for whole system when chimney is not placed on main hot area of heat sink or the incorrect orientation of heat sink. The experiment for the short plate fins with long base , the 80mm high chimney for the sub-heat dissipation area was higher than original 2℃. The experiment for the down side part of extrusion case, the uncut-fin with chimney 80mm high was only improved 2℃ compared with cut-fin without chimney.