On the Water Swelling Phenomena of Once-through Boilers

Abstract

During start-up of a once-through boiler plant, the so-called water swelling phenomena (Wasserpfropfen) occur, which large quantities of water are simultaneously discharged from the boiler and flow into the by-pass circuits. In this report we first of all suggest a calculation method using an electronic digital computer which incorporates assumptions approximating the actual conditions. Numerical calculations are then performed by this method, and the effects of various factors on the water swelling phenomena are made clear. We also report the test results at the 75 MW Shin-Shimizu Thermal Power Station, which has the first large-size commercial Benson boiler in Japan.