Momentum and energy transfer during phase change of water under high hydrostatic pressure

This work is aimed at investigating phase change processes of water under high pressure by help of an in situ visualization technique. High Pressure Digital Particle Image Velocimetry and Thermography (HP-DPIV and HP-DPIT) techniques are applied to a phase change process for the first time and temperature-convective fields are analysed. Peculiar local flow characteristics are observed, such as stagnation or extensional flow regions, for different processes. Pressure-induced thawing process demonstrates inhomogeneities in temperature field, whereas pressure-assisted thawing has almost a homogeneous temperature distribution. Moreover, one of the ice types which has a higher density than that of water (Ice III) is distinguished with an opposite direction of motion of the solid body, regarding Ice I, and it demonstrates different flow characteristics. Additionally, the processes are represented with conservation balance for mass, energy and momentum to render a global interpretation and to analyse process mechanisms.This work was partially presented in the High Pressure Bioscience and Biotechnology conference in Rio de Janeiro in October 2004.Industrial relevance:In this study, phase change processes of water under high pressure were investigated. The goal was to analyze the fluid-mechanical characteristics of the system and their interactions thermodynamically. A dimensional analysis was carried out. This tool helps in scale up analysis to reduce the number of necessary parameter variations to a minimum. Further, this study aims at a more precise understanding of the primary heat transfer mechanisms which represent an important aspect concerning uniform processing.