Natural convection air cooling between vertical parallel plates with heated protrusions simulating plate-mounted electronic components within an enclosure

摘要

Natural convection air cooling from uniformly heated protruding elements on vertically parallel plates simulating evenly spaced, vertical, plate-mounted electronic components within an enclosure maintained at constant temperature, wasexperimentally investigated. The effect of the aspect ratio(b/H) on natural convection heat transfer between parallel plates with protruding heat sources has also been studied. Four protruding heaters on each vertical plate were mounted with uniformvertical spacing. The two vertical plates on which heated elements were mounted were movable so that the channel width could be adjusted to the desired distances in the center of enclosure. The four heaters on the each plate were identical with eachhaving horizontal protuberance of 30 mm and vertical height of 30mm. All external surfaces of enclosure were cooled at constant temperature. The channel spacing between two plates was varied in experiments from 5mm to 30mm. The experiments were conductedfor six values resulting in variations in the channel spacing to plate height ratio and channel width to protruding height ratio of 0.02 to 0.12 and 0.17 to 1.0, respectively. Air was used as convection cooling medium. Flow visualization pictures and heat transfer data indicate that the relatively high velocity flow risen up along the heated plate with protruding elements at the channel directly affects the local heat transfer coefficient of the heated section. The two rotational flows of mutuallydifferent direction between the top heated section and the top cooling surface influence the heat transfer coefficient of top heaters of two plates. Channel spacing variation between heated plates influences the heat transfer process due to the changes of flow patterns. This influence is weak when the ratio of width to protruding height is 0.5 to 1 and the optimal ratios of the channel spacing to plate height and channel width to protruding height accounted for heat transfer effect is 0.04 to 0.06 and 0.33 to 0.5. Modified channel Rayleigh number, based on six different channel spacing to vertical plate height ratios were analyzed. The correlation of Nusselt number versus modified channel Rayleigh number were reported.