ESDU 82021 provides data and a simple method for calculating pressure loss and heat transfer for single-phase turbulent flow in channels subjected to uniform heat fluxes on the shell-side or tube-side and having uniform surface roughness. Surface roughening is one method that can be used to improve the ratio of heat transfer rating to heat exchanger size. ESDU 82021 outlines the options available for the update or redesign of heat exchangers when roughened surfaces (roughness height up to 5 per cent of the equivalent diameter) are used in place of smooth heat transfer surfaces. Available heat transfer and pressure loss data for axial flow over roughened surfaces have been correlated using a technique developed in the nuclear energy industry. Two simple semi-theoretical equations giving pressure loss and heat transfer are presented. They contain three empirical factors that account for roughness shape, roughness size and channel geometry. The data are applicable for turbulent flow at Reynolds numbers up to 1.0E7 and for both heating and cooling of gases and liquids in channels of various cross-sectional shapes, including annular, elliptical, rectangular and that available for flow along the outside of tubes in a tube bundle.