The analogy between heat, mass, and momentum transfer is applied to a rotating disk. Experimentally measured mass-transfer rates from a disk rotating in an infinite environment under laminar and turbulent conditions are related to the corresponding heat-transfer process by means of an analogy method. The experimental analog is shown to eliminate difficulties associated with accurate measurements of heat-transfer coefficients. Experimental data on the effect of an adiabatic surface placed at various distances parallel to the disk on the transfer rate from the disk are presented. Observations of some unusual flow patterns resulting from Goertler type vortexes in the transition regime and from some as yet unexplained turbulent vortex phenomena are also reported.