Experimental and Numerical Investigation of Forced Convective Characteristics of Arrays of Channel Mounted Obstacles

Abstract

An experimental investigation of the forced convective heat transfer of individual and arrays of multiple two-dimensional obstacles is reported. The airflow rate was varied from 800 ≤ ReDh ≤ 13000. The effects upon the Nusselt numbers and obstacle temperature differences of parametric changes in the Reynolds number, channel height, array configuration, and input heat flux are established. The input heat fluxes to the obstacles ranged from 950 ≤ q″ ≤ 20200 W/m2, which significantly extends beyond that seen in the open literature for forced convective air cooling of simulated electronic components. Comparisons of the obstacle mean Nusselt numbers are made with a two-dimensional laminar numerical model employing the Navier-Stokes equations. A set of correlations characterizing the heat transfer from the protruding heat sources within the channel is obtained. It was found that the obstacle temperature, the critical measure for electronic device failure, must be shown along with the corresponding Nusselt number to fully characterize the thermal state of the heated obstacle as the ratio definition of the Nusselt number can obscure large temperature increases. The results find that the proper placement of geometrically dissimilar obstacles, such as a taller obstacle, can be used to passively enhance the heat transfer in its vicinity. This effect would be dependent upon the flow rate and geometries in order to control the reattachment zones and their subsequent convective augmentation. The experimental results are found to be in good agreement with the results from the numerical simulation. Finally, a set of pertinent correlations for the arrays of channel mounted obstacles is given.