2-LAYER-MODEL PREDICTIONS OF HEAT-TRANSFER INSIDE ENHANCED TUBES

Turbulent flow in axisymmetric enhanced tubes with repeated transverse rectangular disruptions was simulated using the two-layer turbulence model of Chen and Patel [1]. The predictions were in good agreement with experimental data for friction factors and both local and average Nusselt numbers. The low-Reynolds-number two-equation model of Lam and Bremhorst [2] was considered, and the predicted results were also compared with local heat transfer measurements. This model overestimated the local Nusselt numbers at some locations by about a factor of 2. Results from the two turbulence models were also compared for a sudden pipe-expansion geometry. The Lam and Bremhorst model yielded acceptable local Nusselt number predictions, while the Chen and Patel model underpredicted the local Nusselt numbers and predicted the location of the heat transfer maximum further upstream.