Natural convection heat transfer and boundary layer transition for vertical heated cylinders

Abstract

This experimental study characterizes the effect of radius of curvature on heat transfer and boundary layer regime transition from laminar to turbulent flow on vertical heated cylinders with a heat flux boundary. Spatially-resolved temperature and velocity data was gathered from a series of five heated cylinders with unique diameters using distributed temperature sensors, thermocouples, and particle image velocimetry. A novel geometric relation has been derived to quantify the influence of curvature on heat transfer and regime transition which has proven to be in good agreement with empirical results. Advanced experimental and analysis methods have been implemented to yield the first continuous, local, curvature-dependent Nusselt correlation for the laminar, transition, and turbulent regimes for natural convection from vertical heated cylinders. As part of this correlation, empirical curvature-dependent dimensionless expressions for predicting regime transition have been developed from three separate data types and are used to define the bounds of the Nusselt correlation regimes.