Abstract: A parallel plate heat sink, used in conjunction with an air moving device which provides an annular flow of air against the heat sink, is further provided with enhanced flow deflector means which selectively block potential exhaust paths so as to redirect the flow of air to the region under a central hub of the fan. This transforms otherwise stagnant air volume in the center of the heat sink into a primary cooling region thus lowering conduction losses and electronic component junction temperatures. Redirection of air flow includes passages within end fins which enhance capacity by improving the exiting flow.