Fluid injection with supercritical reservoir conditions: Overview on morphology and mixing

The present work provides an overview on the possible phase transitions associated with supercritical fluid injection and a detailed evaluation of the mixing process between injectant fluid and quiescent ambience. The experiments cover superheated liquid disintegration, pseudo-boiling transition and single-phase jets under different nozzle pressure ratios. Pseudo-boiling effects emerge when rapid, subsequent changes in pressure/temperature interact with the non-linear behavior of thermodynamic response functions across the Widom line. The associated density fluctuations cause a significant increase in the scattering cross section and may lead to thermo-convective instabilities. Our analysis of the mixing process demonstrates the limited applicability of the adiabatic mixing model, which is often restricted to short residence times even in highly turbulent jets (Re = O(10(5))). Specifically, our findings show the importance of considering all coupled transport processes in the analysis of mixing problems at high pressures, in particular in presence of large mass concentration and temperature gradients. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study provides an overview of possible phase transitions associated with supercritical fluid injection and evaluates the mixing process between injectant fluid and ambient surroundings. Pseudo-boiling effects and density fluctuations leading to thermo-convective instabilities were observed, highlighting the importance of considering all coupled transport processes in high-pressure mixing problems, especially in the presence of large mass concentration and temperature gradients. Additionally, the limited applicability of the adiabatic mixing model, particularly in highly turbulent jets, was demonstrated.