The method for studying the drag coefficient of spherical particles under non-isothermal conditions

Abstract

A method and results of an experimental studying the sedimentation of solid spherical particles in a viscous liquid under non-isothermal conditions at low Reynolds numbers (Re<1) are presented. To determine the dependence of the drag coefficient on the temperature difference between the particles and liquid, a special setup has been developed. The experimental setup for determining the effect of non-isothermal conditions on the gravitational sedimentation of solid spherical particles in a viscous liquid consists of a prismatic cell with a viscous liquid, a particle heating device, a device for incorporating the reference and heated particles into the liquid, and a system for visualization of the particle sedimentation. In the experimental setup, two particles of the same diameter, made of the same material, are introduced into the cell at a zero initial velocity. Immediately before introduction into the liquid, one of the particles is heated (or cooled) to a temperature different from the temperature of the other (reference) particle, equal to the temperature of the liquid. The deposition rate of each of the particles is measured by the time-of-flight method using video of the deposition process through the transparent walls of the cell. As a result of a series of experiments, a decrease in the drag coefficient by 38% was obtained at a maximum temperature difference between the particles and liquid of 280°C.