Fluid mixing analysis for predicting shell wall thinning of a feed water heater

Abstract

Feedwater flowing in the tube side of the number 5 high pressure feedwater heaters is heated by extraction steam from the high pressure turbine and drain water from the moisture separators and the number 6 high pressure feedwater heaters and supplied into the steam generators. Because the extraction steam from the high pressure turbine is a two phase fluid of high temperature, high pressure, and high speed and changes direction after colliding with the impingement baffle, the shell wall of the number 5 high pressure feedwater heaters may be subjected to flow-accelerated corrosion. Wall thinning damage caused by the flow-accelerated corrosion has primarily occurred in carbon and low alloy steel piping. Components, such as feedwater heaters, condensers, etc., however, have recently experienced severe wall thinning damage, which will increase as operating time progresses. This paper describes the fluid mixing analysis study using PHOENICS code in order to determine root cause of the shell wall thinning of the feedwater heaters. To identify the relation between the wall thinning and the fluid behavior, the local velocity components in the x-, y-, and z-direction were compared with the wall thickness data by ultrasonic test.