Numerical modeling of heat and mass transfer characteristics during the forced convection drying of a square cylinder under strong blockage

Abstract

Two-dimensional analysis of heat and mass transfer during drying of a square cylinder (SC) for confined flow with a strong blockage ratio (=0.8) was performed using the alternating direction implicit (ADI)-based software. The influence of Reynolds number (Re=10-50) and moisture diffusivity number (D=1x10(-5)-1x10(-8)m(2)/s) on the heat and mass transfer mechanisms was investigated. The convective heat transfer coefficients on SC surfaces were obtained using a commercial software package. The moisture content distributions inside a SC under transient conditions were calculated using the ADI method. The calculations showed that a higher Reynolds number enhances the overall mean Nusselt number and heat transfer coefficient value. The largest mean Nusselt number and heat transfer coefficient values were obtained at the front face of the SC, which makes the greatest contribution to the overall mean Nusselt number and heat transfer coefficient values for all surfaces of the SC. The effect of Reynolds number on the overall drying time was also investigated. Low Reynolds number and moisture diffusivity values lead to an increase in the overall drying time (t(od)). For Re=10, the t(od) values are 502.19220288s and for Re=50, the t(od) values are 126.1470353.21s for a moisture diffusivity range of D=1x10(-5)-1x10(-8)m(2)/s. t(od-Re=10)/t(od-Re=50) ratios are 3.98-3.89 and 3.13 for a moisture diffusivity range of D=1x10(-5)-1x10(-8)m(2)/s. t(od-D2)/t(od-D1) is 7.47 for Re=10, and t(od-D3)/t(od-D2) is 7.63 for Re=50, whereas t(od-D3)/t(od-D1) is 438.66 for Re=10, and t(od-D3)/t(od-D1) is 557.74 for Re=50. Additionally, iso-moisture contours of SC were presented and relations for Nusselt number and mass transfer coefficient values were derived.