Forced Convection Cooling of Low-Power Handheld Devices Using a Vibrating Cantilever Beam

Abstract

In this study, a convection cooling technique for handheld electronic devices is proposed and investigated. The technique uses bulk airflows generated by a vibrating cantilever beam actuated by a rotating imbalance motor. Analytic coupled physics modeling using an approximate integral method within laminar-flow boundary layers was used to analyze the proposed cooling technique. The cantilever beam and enclosure were designed based on the form factors of a typical handheld device. The bulk airflow cooling performances at various probe locations were investigated experimentally for low and high heating loads and numerically verified. The results indicate that a higher heating load of the heat source results in a larger temperature drop at the same convection rate. Also, for the probe locations away from the heat source and closer to the beam, the resulting temperature drops were relatively small despite a stronger velocity field generated by the beam. This is due first to the heat generated by the vibrating beam itself and second to a circulation of the air heated by the heat source to the rest of the regions in the enclosure. In general, a good agreement between experimental and numerical results was attained, even though a slight difference between two results exists. Overall, significant cooling was achieved by the proposed system. With a beam tip deflection of ±4 mm, nearly an 18-fold increase in the cooling performance was achieved compared to a natural convection case. Furthermore, the cooling performance continues to increase as the tip deflection of the cantilever beam increases. Thus, a cooling system using the bulk airflow generated by a vibrating cantilever beam has much potential as a feasible solution for electronic handheld devices.