ISSN Online: 2377-424X
ISBN Print: 0-89116-130-9
International Heat Transfer Conference 6
PREMATURE DRYOUT IN CONVENTIONAL AND NUCLEAR POWER STATION EVAPORATORS
Abstract
There has been extensive operating experience of dryout causing on-load corrosion failures in power station evaporators. These have covered low, intermediate and high steam qualities over a wide range of pressures, flow rates and heat fluxes. In many cases, the recommended chemical treatment was being applied and the heat fluxes were not necessarily very high.
When heat fluxes are not high the likelihood of dryout in horizontal banks of tubes and in helices depends very much on the detailed two phase flow patterns in the tube. The paper describes three distinct types of flow which can give rise to dryout at low, intermediate and high steam qualities. Theoretical models have been developed to a degree where they can be usefully applied to practical problems and these are described and critically assessed to show where further work is likely to lead to valuable improvements.
When heat fluxes are not high the likelihood of dryout in horizontal banks of tubes and in helices depends very much on the detailed two phase flow patterns in the tube. The paper describes three distinct types of flow which can give rise to dryout at low, intermediate and high steam qualities. Theoretical models have been developed to a degree where they can be usefully applied to practical problems and these are described and critically assessed to show where further work is likely to lead to valuable improvements.