CONSIDERATIONS OF A TWO-PHASE FLOW DIFFUSER DURING SELF-FLASHING PHENOMENON OF HOT WATER IN PIPING

Abstract

Self-flashing two-phase flow caused erosion damage to the piping just downstream from the constricted parts such as valves, orifices, etc. of the hot water piping. The cause and allowable value of erosion, caused at the diffuser behind valve, were experimentally analyzed using a half-cut diffuser in order to make the observation of inner surface easy. As the result, the intensity of the erosion was affected by the two-phase flow pattern and the divergent angle of the diffuser. The erosion was mainly caused by an eddy flow generated at the diffuser. Allowable values of erosion factors, such as averaged velocity, averaged kinetic pressure and cavitation coefficient, depended on the divergent angle of the diffuser.