The New Generation of High-Pressure Heaters for Steam Turbine Units at Nuclear Power Plants

Abstract

The designs of vertical high-pressure heaters (HPHs) for a regeneration system of steam-turbine units (STUs) at nuclear power plants are compared. The proposed heat exchanger with a header-platen tube system is compared with a conventional counterpart by thermohydraulic and design characteristics, weight and dimensions, and performance indicators. Excellent thermohydraulic performance of the proposed apparatus are brought about by the effective condensation due to a high velocity of the condensing steam flow in the shell’s side. The tube bundle consists of standardized platens, the spacing between which can vary in a wide range. The introduction of a cylindrical tube header in place of the tube sheet considerably decreases the wall thickness with a corresponding reduction in the apparatus weight and also prolongs the service life due to elimination of sludge build-up at tube-to-tube header attachment points. Easy maintenance of these heaters is enabled by the access to tubes fixed in the upper and lower vertical cylindrical tube headers through manholes to ergonomically plug faulty tubes. The manufacturing time of the apparatus exchanger and the man-hours for its installation decrease due to the application of standardized tube platens and a shorter length of tube attachment holes. The proposed design has been used as the basis for developing a series of heat exchangers for installation at operating and newly designed power units of NPPs. These apparatuses can accommodate two series-connected, two parallel-connected, or two-series-connected and two parallel-connected HPHs in a single shell, thereby reducing the footprint occupied in a turbine hall. The above-mentioned features of the developed apparatuses are important in the reconstruction (or modernization) of operating NPP power units when the steam capacity of a nuclear steam generating plant is to be increased. The introduction of the proposed apparatuses opens the new way to the optimization of the design, process, and space-and-layout solutions for the regeneration systems of existing and newly designed steam turbine units with a corresponding reduction in operating costs and capital investments in the construction or reconstruction of NPP power units.