The modelling of multi-phase water
flow is an important modern-day design tool used by engineers
to develop practical systems which are beneficial to society . Multi-phase water
flow can
be found in many important industrial applications such as large scale conventional and nuclear
power systems, heat transfer machinery, chemical process plants, and other important examples.
Because of many inherent complexities in physical two-phase
flow processes, no generalised
system of equations has been formulated that can accurately describe the two-phase
flow of water at all flow conditions and system geometries. This has led to the development of many different models for the simulation of two-phase
flow at specific conditions. These models vary greatly in complexity.
The simplest model that can be used to simulate two-phase
flow is termed the homogeneous equilibrium (HEM) two-phase flow model. This model has been found useful in investigations of choking and flashing
flows, and as an initial investigative model used before the formulation
of more complex models for specific applications. This
flow model is fully de ned by three conservation
equations, one each for mass, momentum and energy. To close the model, an equation
of state (EOS) is required to deliver system pressure values. When solving the HEM, a general
practice is to employ an equation of state that is derived from a fundamental expression of the
second law of thermodynamics. This methodology has been proven to deliver accurate results
for two-phase system simulations.
This study focused on an alternative formulation of the equation of state which was previously
developed for the time dependent modelling of HEM two-phase
flow systems, termed the rate
form of the equation of state (RFES). The goal of the study was not to develop a new formulation
of the EOS, but rather to implement the RFES in a transient simulation model and to
verify that this implementation delivers appropriate results when compared to the conventional
implementation methodology. This was done by formulating a transient pipe and reservoir
network model with the HEM, and closing the model using both the RFES and a benchmark
EOS known to deliver accurate system property values. The results of the transient model
simulations were then compared to determine whether the RFES delivered the expected results.
It was found that the RFES delivered sufficiently accurate results for a variety of system
transients, pressure conditions and numerical integration factors. / MIng (Nuclear Engineering), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/13331 |
| Date | January 2013 |
| Creators | Fick, Lambert Hendrik |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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