Intensified heat transfer in modular steam generators

The assessment of tubes with inner fins in the helix points to the intensification of heat transfer in the evaporation part of the steam generator model tube. The effects of pitch and fin height cannot so far be evaluated in view of the fact that heat technology measurements were only carried out on tubes with a 250 mm pitch and a 0.5 mm fin height. It can be expected, however, that increasing the fin height and reducing the pitch will result in full stream rotation and an increased additional turbulence between the fins, which will undoubtedly affect the significant increase in critical tube performance. The assessment of the measurements confirms theoretical assumptions. The use of tubes with helical inner fins allows a significant reduction in the heating surface size of the evaporation steam generator part. For instance, in the finned tube studied at the same steam dryness can be obtained at the evaporator outlet as in a smooth tube. The heating surface, however, can be shortened twice as much. Operating modes and configuration should be selected such that departure nucleate boiling in a finned tube is considerably eliminated. (Kr)