This work deals with modeling and numerical simulation of fluid flow and heat transfer associated with phase change process inside both isotropic and anisotropic porous media, based on the Two-Phase Mixture Model (TPMM) along with the assumption of Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. In particular, it demonstrates the necessity and usefulness of a newly proposed smoothing algorithm for handling the sharp discontinuities in the effective diffusion coefficient in order to avoid the occurrence of non-physical “jump” in the predicted temperature distribution during the numerical simulation of the complete phase change process inside porous media. For the purpose of demonstration, one- and two-dimensional phase change problems operated in the Darcy flow regime have been considered.The Finite Volume Method (FVM) has been used on both staggered and non-staggered grid layouts in order to solve the governing conservation equations. In this work, after critically analyzing the drawbacks of the existing enthalpy formulation based on TPMM, a modified formulation has been also developed that can easily accommodate substantial density variations in the single phase regions. The results obtained from the modified enthalpy formulation have been compared with that predicted by the existing modified volumetric enthalpy formulation and excellent agreements have been observed for all tested cases. A thorough parametric study, using both LTE and LTNE models, indicates that the adoption of the proposed smoothing algorithm successfully eliminates “jump” in the predicted temperature distribution and does not alter the overall energy and momentum balance. All tested cases, covering applicable ranges of parametric variations, could be physically interpreted. The methodology is, therefore, recommended for future simulations of complete phase change process inside porous media. The results also show that the modified enthalpy formulation requires significantly less computation time thanmodified volumetric enthalpy formulation.

Liquid-Vapor Phase-Change Phenomena presents the basic thermophysics and transport principles that underlie the mechanisms of condensation and vaporization processes. The text has been thoroughly updated to reflect recent innovations in research and to strengthen the fundamental focus of the first edition. Starting with an integrated presentation of the nonequilibrium thermodynamics and interfacial phenomena associated with vaporization and condensation, coverage follows of the heat transfer and fluid flow mechanisms in such processes. The second edition includes significant new material on the nanoscale and microscale thermophysics of boiling and condensation phenomena and the use of advanced computational tools to create new models of phase-change events. The importance of basic phenomena to a wide variety of applications is emphasized and illustrated throughout using examples and problems. Suitable for senior undergraduate and first-year graduate students in mechanical or chemical engineering, the book can also be a helpful reference for practicing engineers or scientists studying the fundamental physics of nucleation, boiling and condensation.

The Surface Wettability Effect on Phase Change collects high level contributions from internationally recognised scientists in the field. It thoroughly explores surface wettability, with topics spanning from the physics of phase change, physics of nucleation, mesoscale modeling, analysis of phenomena such drop evaporation, boiling, local heat flux at triple line, Leidenfrost, dropwise condensation, heat transfer enhancement, freezing, icing. All the topics are treated by discussing experimental results, mathematical modeling and numerical simulations. In particular, the numerical methods look at direct numerical simulations in the framework of VOF simulations, phase-field simulations and molecular dynamics. An introduction to equilibrium and non-equilibrium thermodynamics of phase change, wetting phenomena, liquid interfaces, numerical simulation of wetting phenomena and phase change is offered for readers who are less familiar in the field. This book will be of interest to researchers, academics, engineers, and postgraduate students working in the area of thermofluids, thermal management, and surface technology.

This thesis presents a detailed analysis of vapor bubble dynamics and the interfacial process of liquid-vapor phase change. A spherically symmetric model for a single vapor bubble is employed to present a numerical and theoretical analysis of the intermediate bubble collapse, where, in contrast to the thermally induced or inertia dominated collapse, both the effects of liquid-vapor interfacial heat transfer and the advection of the surrounding liquid play an important role. The contrast in thermal, intermediate, and inertial behavior of collapse is represented in the form of a regime map defined by two non-dimensional quantities, Bsat and Îl, which can be directly evaluated from the initial system conditions of collapse. The same model is also used to simulate a spherically symmetric bubble growth configuration to assess the physical validity of a constant interface temperature assumption made by Highly-Resolved Simulation (HRS) studies aimed at solving flows undergoing phase change. Results show that HRS predictions are inaccurate during the initial period of bubble growth, which coincides with the inertial growth stage. A closed-form expression for a threshold time is derived, beyond which the commonly employed HRS assumptions hold. Forgoing the limitation of spherical symmetry, the second theme of this thesis is on the development of a general two-phase flow solver that can handle the phase change process. Under a finite volume framework using a geometric Volume of Fluid (gVoF) approach, two key challenges with phase change flows have been addressed in this work, namely, (i) added deformation of the interface, and (ii) capture of velocity and pressure gradient discontinuity at the interface, both caused due to phase change. To track the interface in the gVoF scheme, an effective flux is defined that captures the effect of phase change on interface motion. This method improves upon the source term approach used in other studies. For the solution of velocity and pressure, a ghost fluid approach has been implemented, which is the first of its kind in a VoF-based phase change solver.

Since the second edition of Liquid Vapor Phase Change Phenomena was written, research has substantially enhanced the understanding of the effects of nanostructured surfaces, effects of microchannel and nanonchannel geometries and the effects of extreme wetting on liquid-vapor phase change processes. This edition includes significant new coverage of microchannels and nanostructures along with many other updates. More worked examples and numerous new problems have been added along with a complete solutions manual and electronic figures for classroom projection.