Heat transfer and frictional loss performance in radial flow through multiple parallel disk assemblies are experimentally studied by a modified single-blow transient test method. The mechanisms of heat transfer enhancement are determined in the four flow regimes which are characterized by different combinations of flow patterns: pure laminar, laminar-oscillating-laminar, laminar-oscillating-turbulent-laminar, and laminar-oscillating-turbulent type convection. The fifth convective regime is predicted. The results of a condensation-heated disk core are incorporated for discussion and performance comparison. The effects of the disk spacing and size and influx disturbance on the transfer performance are investigated. It is concluded that the disk device has the performance characteristics comparable to high-performance plate-fin type surfaces that are commonly employed in compact heat exchangers.