NUMERICAL SIMULATION OF COLLOIDAL SOLIDIFICATION INSIDE A DIFFFERNTALLY HEATETD CAVITY

Conference Name: Proceedings of the ASME 2013 Summer Heat Transfer Conference
Location: Minneapolis, MN, USA
Date: 2013

List of Authors:

Yousef. M. F. EL Hasadi, , J. M. Khodadadi

Abstract

The colloidal solidification phenomena had a wide range of applications ranging from frozen-food industry, creyoprevention, freeze cast materials, and energy storage. In this study, the development of the solid-liquid interface, particle's concentration distribution, and as well, as the development of the thermo-solutal convection will be investigated. The numerical model is based on the one-fluid-mixture approach with the single-domain enthalpy-porosity model for phase change. The linear dependence of the liquidus concentration of the nanoparticles was assumed. The segregation coefficient is kept constant to a value of 0.1. A colloidal suspension consisted of water and copper, and alumina nanoparticles were considered in the current investigation, the nanoparticle size selected was 2nm. The suspension was solidified unidirectional inside a square differentially heated cavity, cooled from the left side. I was found that the solid-liquid interface changed it's morphology from planer to dendritic as the solidification process proceeds in time, due to the constitutional supercooling resulted from the increased concentration of particles at the solid-liquid interface rejected from the crystalline phase. Initially, flow was consisted of two counter rotating cells. However, at later times only one cell survives rotating counter clock wise. Changing the material of the particle to alumina, results in crystalize phase, with a higher concentration of particles if it is compared to that of the solid phase resulted from freezing the copper-water colloidal suspension. Decreasing the segregation coefficient destabilize the solid interface, and increase the intensity of the convection cell with respect to that of the case of no particle rejection. At slow freezing rates, the crystal phase resulted consisted of lower particle content if it is compared to that resulted from higher freezing rate.