Natural Convection From a Column of Flush Heat Sources in a Vertical Channel in Water

Abstract

Natural convection from a single column of eight in-line, rectangular heat sources flush mounted on one wall of a vertical channel immersed in water was examined. Input power to each heating element was varied from 0.2–2.0 W for channel spacings in the range of 1.5–15.0 mm, as well as with the shroud removed. Flow visualization in two mutually perpendicular vertical planes was carried out both with and without the shroud for each power level. Component temperature measurements were made using thermocouples embedded within the substrate. By suitably accounting for the increasing convected energy downstream, a single heat transfer correlation was obtained for all channel spacings larger than 3 mm. For smaller channel spacings, the component center temperatures increased substantially above the correlation. To investigate the effect of heater spacing, temperature measurements in the absence of shroud were also made with only selected components powered. As the spacing between successive heated components was increased to twice of the fully heated configuration, the upstream effects on component heat transfer become negligible. Further increase in spacing resulted in a weak enhancement in heat transfer downstream. Comparison of the present data with existing experimental studies and new computations revealed significant influence of the heater and substrate material thermal properties on the transport.