Investigation of performance augmentation for natural convective heatsink with the help of chimney

Abstract

The effect of adding a plastic chimney on the top of upward horizontal rectangular heatsink under natural convection was investigated experimentally and numerically. The effect of the chimney height, length, depth, inclination, view factor, and conductivity for different fins array dimensions were investigated as well. The presence of low thermal conductivity chimney induces airflow by creating effective pressure difference between the edge and the center of the chimney. Yet higher chimney height results in larger pressure difference. Yet the pressure difference is accentuated with a sharp edge chimney. A smooth edge chimney reduces the pressure gradient and entrained airflow. The chimney with low thermal conductivity is capable to entrain more airflow into the heatsink when comparing with high thermal conductivity chimney (aluminum). The entrained airflow can be as much as 25% higher than the metal chimney. A smaller fin spacing may block the airflow and reversed the heat transfer. For the present configuration, it is found that the chimney is only effective when the heatsink is placed horizontally upward. By employing a transparent chimney, the view factor of the heatsink can be appreciably improved when comparing with opaque chimney.