Hydrodynamic-thermal boundary layer development and mass transfer characteristics of a circular cylinder in confined flow

Abstract

The effects of blockage on the hydrodynamic, thermal and mass transfer characteristics of a circular cylinder (CC) and their association with each other are investigated numerically, by considering the influence of blockage (beta=0.333-0.800) on the flow and heat transfer mechanisms in conjunction with moisture diffusivity (D=1 x 10(-8)-1 x 10(-5) m(2)/s) to show how much mass transfer behavior and phenomena are affected. As some comprehensive ANSYS-CFX runs are performed in the hydrodynamic and thermal fields around the CC, the moisture distributions within the CC are evaluated by Alternating Direction implicit method. It is determined that blockage causes thinner hydrodynamic and thermal boundary layers, rises the frictional and thermal activities, and shifts the separation locations (theta(s)) downstream to theta(s)=50.20 degrees, 41.98 degrees and 37.30 degrees for beta=0.333, 0.571 and 0.800. In the complete blockage scenario set, stagnation point heat transfer values are evaluated to be above those of the back-face, signifying the superior heat transfer enhancing capability of the stagnation point momentum activity when compared with the impact of downstream vortex system. The influence of moisture diffusivity on the overall drying times is determined to advance with stronger blockage. As the back face mass transfer coefficients (h(m-bf)) rise with a high beta, the contrary is valid for front face values (h(m-ff)), with the interpreting ratios of (h) over bar (m-bf)/(h) over bar (m)=0.51 and 0.57 and (h) over bar (m-ff)/(h) over bar (m)=1.49 and 1.43 for beta=0.333 and 0.800.