The Effect of Hard Scale Deposition on the Wall Heat Flux of a Cold Finger

A cylindrical cooled probe (cold-finger placed in cross-flow) has been used to investigate fouling in the off-gas duct located upstream from the gas cleaning system during primary aluminium production. Hard scale was formed on the front side of the probe whereas loose deposits accumulated on the rear side, causing inhomogeneous fouling resistance along the cold-finger circumference. Thermocouples and heat flux sensors allowed for the monitoring of the global and local heat transfer on both the front and rear sides of the probe. Additionally, the off-gas velocity upstream of the probe was monitored. Regression analysis of the heat transfer data produced was performed to calculate the fouling resistances from multiple experiments. Finally scale thickness was measured after the experiments and used to estimate its thermal conductivity. © The Minerals, Metals & Materials Society 2020