Finite Element Modelling Of Thermal Processes With Phase= Transitions
Abdelhaq Abouhafc

Site of the project:
TNO Science and Industry
Schoemakerstraat 97
2628 VK

start of the project: September 2006

In December 2006 the Interim Thesis has been appeared and a presentation has been given.

The Master project has been finished in June 2007 by the completion of the Masters Thesis and a final presentation has been given.

For working address etc. we refer to our alumnipage.

Summary of the master project:
Adding and removing heat and mass to and from a product take place in several processes in the industry. For example: steam production, freezing and drying. Improving product quality is the objective of using physical and chemical models. These models solve a set of heat and mass equations as a function of time and position. The pressure is assumed to be constant, while the temperature and concentration are chosen as state variables. When phase change takes place during these processes the modeling becomes more complicated. In this case using only temperature and concentration is not sufficient for the process description. Additional state variables such as solid, liquid and vapor fractions are needed.

These processes are encountered by oil refineries

The simulation model should decide which equations are appropriate at a given time during the simulation; one should also take into account that the phase changes usually occur during a part of the entire process. The simulation of thermal process with phase changes is usually quite difficult because we need to solve different sets of equations for different phases of the process. Switching from one set of equations to another can cause instability of the numerical solution. We also need to use a large amount of input parameters, such as specific heat and densities of all phases and latent heat of phase changes.

The objective of this project is the combination of the density-enthalpy phase diagram with finite elements methods. The finite element method can be used to solve transport equations (mass, heat and impulse) and the density-enthalpy phase diagram gives the thermodynamics constants. The permeability, viscosity and heat conductance are very important in this case. The developed models can be used to optimize processes and products quality.

The density-enthalpy phase diagram for water

Contact information: Kees Vuik

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