Sphere Approximation for Nanorod Near-Field Radiative Heat Exchange Analysis

Abstract

A theoretical method for cylinder-to-cylinder radiative heat exchange is formulated by utilizing a sphere approximation method. The sphere approximation method requires dividing the cylinders into smaller connected spheres and applying a previously published numerical method for near-field sphere-to-sphere radiative exchange. The overall radiative power exchange is obtained by an additive ray-tracing assumption. These results are compared to results produced by a rigorous cylinder-to-cylinder radiative heat exchange method. The heat exchange of nanorods is plotted vs. the gap to assess the impact of near-field radiative transfer as the gap decreases. The unit sphere method is applied to nanorod configurations having length-to-diameter ratios of 3:1, 5:1, and 7:1. Graphical results of energy vs. nanorod radii are presented. A nanoradii/gap dimensionless relationship caused by geometric effects is found and related to power for nanorods of different aspect ratios and temperatures. A V-shaped configuration is considered, with the results plotted for heat exchange vs. angle. An assessment of the number of spheres required to produce an accurate approximation of the V-shaped configuration of nanorods is presented. An error analysis of this method based on a ray-blocking assumption from neighboring spheres is discussed.