Fin Optimization In A Flow Field Induced By Piezoelectric Fan
Özet
In recent years, piezoelectric fans have been investigated for forced convection heat transfer applications as an alternative to conventional fans. Basically, it consists of a piezoelectric and a non-piezoelectric patch. When AC current is applied, piezoelectric part vibrates with a certain amplitude at that specific AC frequency. In this study, forced convection heat transfer driven by a piezoelectric fan is investigated for fin optimization problem. A 3-dimensional numerical model is implemented with CFD approach employing a commercial CFD solver: Ansys Fluent 17.2. In this model, a piezoelectric fan with a known movement function is simulated in time domain to generate air flow first with a horizontal fan arrangement. The generated air flow is directed to a fin block which is placed at a certain distance from the piezoelectric fan. As a design parameter, the number of fins in fin block is increased. The fin block is formed by attaching conjugated cylindrical fins side by side. The number of conjugated fins is increased from 1 to 10, resulting in 10 different fin block configurations. In this study, there are two boundary conditions applied. Firstly, the total amount of applied heat remains the same. In each configuration 0.8064 W heat is applied to the base of fin block as a boundary condition. Secondly, the applied heat flux remains the same. In each configuration 50400 W/m2 heat flux is applied to the base of fin block as a boundary condition. The average surface temperature of fin blocks, the average surface temperature difference between natural and forced convection, heat transfer augmentation ratio and average base temperature of fin blocks are compared. This comparison results in the optimum number of fins for each criterion. When the heat transfer augmentation ratio is evaluated, the 2-fin-block configuration for the constant total heat boundary condition and the 1-fin-block configuration for the constant heat flux boundary condition gives the best results, respectively. Additionally, a vertical fan arrangement is employed and the results are compared to a horizontal fan arrangement for a specified fin configuration. For the studied fin geometry the horizontal fan arrangement is found to provide better cooling performance in all fin configurations compared to the vertical fan arrangement.
