OpenFOAM Design and Experimental Validation of a Single Phase Flowrate Restrictor

Abstract

The use of flow-rate restrictors in systems with large density gradients is justified by the presence of thermal-hydraulic instabilities. A typical example is boiling systems, where density waves can occur. This phenomenon arises from a flow-rate perturbation that propagates through the system under consideration. These fluctuations are significant in the two-phase region due to changes in density caused by boiling, which propagate as waves with a time delay. An effective way to stabilize two-phase flow is to increase the head loss in the liquid-phase region. In this work, two restrictor designs, characterized by their head loss coefficients in the turbulent regime, are studied. First, CFD simulations were carried out to determine the head loss coefficients. Then, an experimental setup was built to validate the simulations, exploring a wider range of Reynolds numbers that includes the simulated cases. A comparison between numerical and experimental results shows an average difference of less than 5%.