Pore-scale experimental study of boiling in porous media

Abstract

Following a long-lasting failure in the cooling system of a water reactor, the superheated core can be cooled down efficiently by reflooding. At the French Institute of Radioprotection and Nuclear Safety (IRSN), the macroscopic model used to simulate this process is based on strong assumptions on the local flow patterns. This paper presents an experimental study of boiling in porous media with focus on different pore-scale boiling regimes. The experimental setup is a "two-dimensional" porous medium made of 2mm diameter cylinders randomly placed between two ceramic plates. The 145 heating cylinders are RTD probes (Resistance Temperature Detectors), used to give pore-scale thermal measurements as well as heat generation. The operating fluid is HFE-7000, a Fluorinert liquid with a low saturation temperature (Tsat =34°C at atmospheric pressure), which allows all the boiling regimes to be observed with moderate thermal constraints. This paper presents results for forced convection boiling on a single horizontal cylinder embedded in a porous medium, the influence of a heating porous medium on the different boiling regimes and the reflooding of a superheated model porous medium.