Correlations for the symmetric converging flow and heat transfer between two nearly parallel stationary disks similar to a solar updraft power plant collector

•The symmetric sink flow and heat transfer in the collector of a SUPP was investigated numerically.•Buoyancy forces were considered in the model.•Variable flow cross-section was introduced.•Original friction factor and Nusselt number were derived.•Correlations for friction factor and Nusselt number were suggested.

By focusing on the derivation of the corresponding friction factor and Nusselt number for constant temperature absorber, this work considers the internal symmetric sink flow and heat transfer between two nearly parallel disks stationary similar to the fluid motion in the collector of a Solar Updraft Power Plant. For that, a numerical steady state turbulence model for buoyant incompressible fluids exploiting the variation of the duct cross-section was developed. Friction factor and Nusselt number correlations are suggested for intermediate range of Reynolds numbers, where thermo-hydrodynamic aspects are important for Solar Updraft Power Plant performance assessments.