Determination of the Convective Heat Transfer Coefficient of Hot Air Rising through Terracotta Flues

We experimentally studied natural convection processes inside terracotta flues as a part of a larger numerical study of ancient Roman baths. The air, heated in a plenum below the wall, rose through the tubes. Two clusters of thermocouples, equally spaced in the flues, measured temperatures throughout the thickness of the wall. The data from the two clusters proved to be measurably different. The resulting convective heat transfer coefficients determined using the bottom cluster, showed no dependence on the plenum temperature. The measured convective heat transfer coefficient was between 6.2 and 7.6 W/m2·◦C, with an average of 7.0 W/m2·◦C.