Effective Thermal Conductivity of an Iron Globule Packed-bed Sphere Porous Medium

Abstract

The investigation of an effective thermal conductivity (keff), influenced by conductive and
radiative heat transfer, of the packed-sphere porous medium is the goal of this research. The iron
globule having diameter of 5.5 mm and porosity (??) of 0.475 is examined. The experimental
procedure is based on ASTM E1225. The tested porous sample is sandwiched by the reference
materials that a known thermal conductivity (ksolid), Brass solid (70%Cu, 30%Zn), is used. The
energy heat rate supplied to the system at one end is obtained from electrical wire heater with a
constant value at 350 W and the temperature of this position is defined as the higher temperature
(TH). To ensure thatthe temperature gradient measured along the length of the bed, the other end is
cooled by water and thus the temperature of this position is called as the lower temperature (TL).
From the experiment, it was found that keffis decreased with increasing TH and the relation between
keff and TH can beappropriately proposed by apowerequation(kfit = 3880(TH/100)-2.77)owing to R2 =
0.983. In addition, the average quantity of keff (kavg) is slightly higher than the thermal conductivity
combined by void and solid(k??,s), i.e., kavg> k??,s, because of the effect of conduction and radiation is
regarded in kavg. However, the value of ksolidis highest becausethe solid materials do not taken into
account the effect of conduction from porosity or void volume.

Keywords: Effective thermal conductivity, Packed-sphere porous medium, Raditive heat transfer