Method of operating once-through steam generator and once-through steam generator operated by this method

摘要

A once-through steam generator has a vertical flue formed of tubes which are oriented vertically and which are connected in parallel for guiding a flow of flow medium therethrough. The tubes have a surface structure on an inner wall surface which causes flow turbulence and eddy currents in the flow medium. The surface structure includes first and second, mutually superimposed, contrary ribbings. The first ribbing encloses an acute angle with the tube axis, and the second ribbing extends parallel to the tube axis. The first ribbing forms an onflow flank angle with the tube wall which is flatter than a flow-off flank angle. Elevations of the ribbings rise at least 0.7 mm above the tube wall surface. A mass flow density of the medium in the tubes is adjusted as a function of the inner tube diameter, by maintaining the mass flow density below a predetermined limit curve.