The thermal distortion of mechanical seal faces has a critical impact on the performance of the seal. Experimental work is discussed which quantifies the thermal characteristics of a mechanical seal and its operating environment. Experimental techniques are employed which measure the seal face torque, thermal gradients, and fluid flow patterns under the normal operating conditions of the seal. The experimental data is used to calculate the heat that is generated at the seal faces and the Nusselt number on the wetted surfaces on the stationary element. The experimentally determined Nusselt numbers are compared to experimental and empirical values that have been presented by other researchers. The effect of the seal geometry on the experimental Nusselt numbers is evaluated.Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997