Thermal-hydraulic aspects of valves used in nuclear power plants are discussed. Emphasis is given to a review of recent work on safety and pressure relief valves, including the presentation of some experimental results describing one- and two-phase flow through such valves. Measurements of internal flow fields are presented. Significant flow separation occurs in both the safety and the pressure relief valves. An experimental study using high-speed photography to determine vaporization sites in safety valves when the flowing medium is initially a compressed liquid is described. A new method of estimating the observed decrease in valve coefficient when choked vapor flow changes to liquid flow is developed. This method also permits the prediction of the observed dependence of the valve coefficient on the receiver pressure in the choked and unchoked flow regimes. The fluid dynamic phenomena that lead to valve disk vibrations are discussed.

Thermal Hydraulics of Valves for Nuclear Applications

Etude experimentale des caracteristiques thermiques et hydrauliques des soupapes de surete et des soupapes de decompression pour centrales nucleaires. Presentation de donnees experimentales sur des ecoulements mono et diphasiques a travers de telles soupapes

Thermalhydraulics of valves for nuclear applications

A modeling approach to study the fluid dynamic forces acting on the spool of a flow control valve

Divergence and limit cycle oscillations in valves operating at small openings

One of the foremost concerns facing pump users today is that of pulsation problems in their piping systems and manifolds. In cases where a fluid excitation is coincident with both an acoustic resonance and a mechanical resonance of the piping system, large piping vibrations, noise, and failures of pipes and attachments can occur. Other problems that uncontrolled pulsations can generate include cavitation in the suction lines, valve failures, and degradation of pump hydraulic performance. The potential for problems greatly increases in multiple pump installations due to the higher energy levels, interaction between pumps, and more complex piping systems involved. The aim of this tutorial is to provide users with a basic understanding of pulsations, which are simply pressure disturbances that travel through the fluid in a piping system at the speed of sound, their potential for generating problems, and acoustic analysis and, also, to provide tips for prevention of field problems. The target audience is users who have had little previous exposure to this subject. Accordingly, the tutorial neglects the high level mathematics in the interest of presenting fundamental concepts in physically meaningful ways in the hope that benefit will be provided to the layman.

N. Kouwen

Papers

Flow Induced Vibrations of a Hydraulic Valve and Their Elimination