The Flow of a Flashing Mixture of Water and Steam Through Pipes

Abstract

Abstract This paper presents a method of designing piping to carry a Hashing mixture of water and steam. An example of such piping is the cascade drain lines between feedwater heaters. The flow formula is based on a thermodynamic analysis of the problem, and the necessary coefficients of friction have been determined from tests. Calculations indicate the possibility of a critical-pressure condition at the end of a pipe carrying a flashing mixture. Each of the drain lines included in the study exhibited this phenomenon. The paper also includes a discussion of erosion of elbows in pipe lines carrying a flashing mixture, and suggests designs for minimizing or preventing failures from this cause. A criterion for predicting the comparative life of different sizes of pipes for a given line carrying a flashing mixture is set up on the basis of the total force on the elbows due to the momentum of the flowing fluid. An example of the application of the proposed flow formula to an actual design case is given in the Appendix.