A Sparcely Filled Liquid/Liquid Rotating Drum Heat Exchanger (RDHE) was investigated for its heat transfer characteristics. Drums upto 10 cm in diameter and 1.0m long were rotated upto 350 rpm. Liquids investigated varied in kinematic viscosity from water at 2.2 * 10(-3) m(2)/hr to 32 wt% LiCl solution at 6.3 * 10(-3) m(2)/hr. In this range data showed that the him heat transfer coefficient did not depend on kinematic viscosity. This resulted in a "best fit" correlation of Nusselt Number (100 to 800) with Peclet Number (200,000 to 2,000,000) as oppossed to Nusselt Number with Reynolds Number (2000 to 20,000). Analysis suggested that the heat transfer between two liquid films adhering to opposite surfaces of a rotating drum was controlled by conduction not a convection mechanism. The RDHE has found application in the heat transfer between two liquids of similar pressure where little to no pressure drops are allowed.