Measuring convection heat transfer coefficients and thermal resistance for protective fabrics using a heated cylinder in a wind tunnel

Abstract

One tradeoff in design of protective clothing for firefighters and other workers is between thermal protection and thermal stress management. Standard methods for assessing thermal stress management of protective clothing include guarded hot plate and mannequin tests. In this study, a fabric-covered heated cylinder was used in a wind tunnel to measure convection heat transfer coefficients and thermal resistance at various air speeds. Measurements demonstrated the impact of air permeability and wind speed on these parameters. When the cylinder was covered with low permeability fabrics, convection heat transfer coefficients were similar to values predicted using a correlation for bare cylinders. Thermal resistance measurements generally ranked fabrics in the same order as guarded hot plate tests. This cylinder test is more representative of the body’s geometry than hot plate tests, but less expensive to conduct than mannequin tests, and could serve as a bridge between these two tests for design purposes.