Pressure loss and heat transfer for single-phase turbulent flow in roughened channels: Methods of calculation

This Data Item is available as part of the ESDU Sub-series on Heat Transfer. Data and a simple method for the calculation of pressure loss and heat transfer for single-phase turbulent flow in channels subjected to uniform heat fluxes and uniform surface roughness on the shell-side or tube-side are provided. Surface roughening is one method that can be used to improve the ratio of heat transfer rating to heat exchanger size. The options available for the update or redesign of heat exchangers when roughened surfaces (roughness height up to 5% of the equivalent diameter) are used in place of smooth heat transfer surfaces are outlined. Available heat transfer and pressure loss data for axial flow over roughened surface are correlated using a technique developed in the nuclear energy industry. Two simple semi-theoretical equations giving pressure loss and heat transfer are presented. The equations contain three empirical factors which account for roughness shape, roughness size and channel geometry. The data are applicable for turbulent flow at Reynolds numbers up to 10 to the 7th power and for both heating and cooling of gases and liquids in channels of various cross-sectional shapes.