A 120 mm × 53 mm x 19 mm horizontally-oriented pico projector in which both a pin-fin array and a piezoelectric fan were installed was tested to measure the thermal resistance at various heating powers. The operating frequency of the 40 mm x 10 mm aluminum piezoelectric fan ranged from 242 Hz to 257 Hz. The heat transfer coefficient of the pin-fin array was also estimated based on a thermal resistance network of the pico projector. The results showed that the thermal resistance of the pico projector which had a piezoelectric fan vibrating at a specific frequency would not monotonically reduce as the heating power increased. The heat transfer coefficient of the 1.5-mm-wide pin-fin array was higher than that of the 2.0-mm-wide pin-fin array at a given fan tip velocity ranging from 0.26 m/s to 0.76 m/s. The highest heat transfer coefficient of the 1.5-mm-wide pin-fin array reached approximately 21 W/m~2K, while the highest heat transfer coefficient of the 2.0-mm-wide pin-fin array was approximately 16 W/m~2K. A correlation between Nusselt number of the pin-fin array and Reynolds number was also developed in this study in a form of Nu = 0.3526Re~(0.1774).
展开▼
