Optimally Staggered Finned Circular and Elliptic Tubes in Turbulent Forced Convection

This work presents an experimental geometric optimization study to maximize the total heat transfer rate between a bundle of finned tubes in a given volume and a given external flow both for circular and elliptic arrangements, for general staggered configurations. The results are reported for air as the external fluid, in the range $2650⩽Re2b⩽10,600$⁠, where $2b$ is the smaller ellipse axis. Experimental optimization results for finned circular and elliptic tubes arrangements are presented. A relative heat transfer gain of up to 80% $(Re2b=10,600)$ is observed in the elliptic arrangement optimized with respect to tube-to-tube spacings, as compared to the optimal circular one. A relative heat transfer gain of 80% is observed in the three-way optimized elliptic arrangement in comparison with the two-way optimized circular one; i.e., with respect to tube-to-tube and fin-to-fin spacings. An empirical correlation for the three-way optimized configuration was obtained to evaluate the resulting maximized dimensionless heat transfer rate.