本研究是以數值模擬的方法，模擬三維封閉矩形腔體內暫態的自然對流和熱傳現象。在腔體內的氣體為空氣，底面的基板上放置固定熱量的三熱源，熱源的排列方式為，直線排列、交錯排列、斜角線排列，當Ra=1.7E+5和Pr=0.7時，比較熱源在不同排列方式與加上散熱片後對溫度分佈和速度場的影響。其中，未加上散熱鰭片的第2種熱源交錯排列有最大的溫度差異15.48%；四種排列方式加上三鰭片散熱片的溫度降介於12%~20%，溫度差異介於1%~4%；加上五鰭片散熱片的溫度降介於15%~22%，溫度差異介於1%~4%。直線排列時，當三鰭片散熱片的鰭片高度增加到19mm，溫度降為34.79%，溫度差異為3.44%。

研究中可知，雖然在熱源上放置散熱片降低了氣體流動的區域面積，但是由於散熱片鰭片數量和高度的增加，使的熱傳量增加，腔體內溫度降低。

A transient numerical method is developed to solve the coupled natural convection and heat conduction problem for three heat sources mounted on a conductive substrate in a three-dimensional enclosure filled with air. Three heat sources, are arranged in four different positions with iosthermal andinsulated walls. When Ra=1.7E+5 and Pr=0.7,the calculating results, show that different positioned arrangements strongly influence the temperature and velocity. The maximum relative temperature difference in the second stagger arrangement without heat sink is 15.48%. Four arrangements with three fins heat sink the temperature drop is 12%~20%, and the temperature difference is 1%~4%. With five fins heat sink the temperature drop is 15%~22%, and the temperature difference is 1%~4%. In the in line arrangement with three fins heat sink, fins height add to 19mm, the temperature drop is 34.79% and temperature difference is 3.44%.

The results indicates that even though fins and height increase the total fluid flow region reduce, but the total contact area between fluid and solid increases, the surface heat appears to exchange for increase and decrease of temperatures.

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