an air - cooled shaft seal comprises an annular body having an inner surface and an outer surface . one or more helical channels are formed on the inner surface . a plurality of external surfaces such as radial fins are disposed in axially spaced relationship on the outer surface , and extend radially in a direction away from a longitudinal axis of the annular body . the external surfaces present a substantially increased surface area through which heat energy is transferred from polymeric material contained in the seal to the atmosphere . the seal may be installed on one or shafts of a gear pump for transporting a viscous material under pressure .