A fin-array-equipped test pico projector with horizontal or vertical orientation was cooled by a vibrating piezoelectric fan in this study. The 47 mm x 10 mm piezoelectric fan was operated at 90 V-rms at a frequency ranging from 135.5 Hz to 129.5 Hz. It was found that the fan vibrating amplitude was affected by both the input power of the heater and the fan operating frequency. The thermal resistance of the fan-cooled test pico projector not always reduced as the heater power increased, and would be equally affected by both forced convection and natural convection depending on Gr and Re numbers. Such phenomenon that might arise from the temperature effect on the fan blade material and the fluidic damping was especially marked when the plate-fin-array-equipped test pico projector was horizontally tested. The results also showed that the pin-fin array was more favorable than plate-fin array for the cooling of test pico projector as a piezoelectric fan vibrated at a specific frequency, regardless of the orientation. When the pin-fin array was cooled by a vibrating piezoelectric fan at 133.5 Hz at 7W in a horizontally and vertically oriented projector, the maximum thermal resistance reduction was about 3.4 degrees C/W and 3.8 degrees C/W, respectively. (C) 2015 Elsevier Ltd. All rights reserved.