Influence of surface roughness on the supercooling degree: Case of selected water/ethanol solutions frozen on aluminium surfaces

This paper presents a study on the impact of the roughness of a metallic surface on the magnitude of the supercooling during freezing of an aqueous solution. Aqueous solutions of ethanol (5%, 10% and 15% w/w) were used as model solutions. Five tubes of aluminium (internal diameter 8 mm) were machined to obtain a roughness between 0.63 and 13.3 μm. These tubes were immersed in a refrigerated bath with a programmable temperature scan. Thermocouples located at the inner surface of the tubes and in the solution were used to measure the magnitude of supercooling. Crystallisations were monitored and supercooling released calculated for each experiments. Our experimental results reveal that roughness is the influencing parameter of the supercooling released: larger the roughness, lower the supercooling. Moreover, a power law correlation between the roughness and supercooling was deduced.