Heat transfer from eccentric annuli of small gap ratio

A Computational Fluid Dynamics (CFD) study has been reported on the eccentric annuli with a wide range of radius ratios (α=0.5, 0.65, 0.8 and 0.95) and dimensionless eccentricity values (0.0, 0.3, 0.5 and 0.7) representing small gap ratios. All the geometric cases are investigated either by imposing a constant heat flux or peripherally varying heat flux on the inner wall. The narrow zone in the annular channel has been observed to have encountered drastic variations in hydrodynamic (velocity and Darcy friction factor) and thermal (temperature and Nusselt number) characteristics. The velocity in the narrow gap increases by 17% for values of α ranging from 0.5 to 0.65, and decreases thereafter. For a typical eccentricity value of 0.7, the mass flux in the narrow gap zone decreases by 75% and Darcy friction factor by 23%. The maximum temperature at the inner cylinder surface is found to increase by 188% at this eccentricity for constant heat flux case and 140% for varying heat flux. Copyright © 2012 by ASME.