Convective heat transfer improvement for a horizontal grooved surface by the piezo-fan integration

Abstract

In this study, the thermal and hydraulic performances of horizontal grooved surfaces subjected to the piezo-fan (PF) is numerically investigated. A total of four grooved surfaces with varying dimensionless edge length of the square groove cross-section (EL = 0.25, 0.5, 0.75 and 1) and a corresponding baseline flat surface (EL = 0) are considered. Two kinds of numerical models are utilized to capture the turbulent characteristics and temperature distribution. The dynamic mesh technique and user-defined function are employed to descript the vibration trajectory of the PF. The focus of this study is on assessing the impact of PF in the design of an active heat sink. It is confirmed that, due to the change in surface geometry, the flow cannot follow the surface contour perfectly, leading to a pressure drop and a separation of flow from the grooved surface. The integration of PF into a horizontal grooved surface is a highly efficient means for improving heat transfer performance. Its role in heat transfer enhancement is most significant when the dimensionless edge length is EL = 0.75. With the presence of PF, the effective area-averaged convective heat transfer coefficient (h_area,eff) both on flat and grooved surfaces are generally larger than the corresponding one without the PF. Of particular is that the h_area,eff of both types of target surfaces reach their maximum within the specified zone S4 (4 A_PP × 4 W_PF), with the grooved surface being approximately 14% to 28% higher than the flat surface. Moreover, the numerical simulation method has been validated through the comparison with a simple heat transfer experiment.