09-02-2013, 12:30 PM
Applications of computational fluid dynamics (CFD) in the food industry: a review
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Abstract
Computational fluid dynamics (CFD) is a simulation tool, which uses powerful computer
and applied mathematics to model fluid flow situations for the prediction of heat, mass and
momentum transfer and optimal design in industrial processes. It is only in recent years that
CFD has been applied in the food processing industry. This paper reviews the application of
CFD in food processing industries including drying, sterilisation.
Introduction
Computational fluid dynamics (CFD) uses powerful computers and applied
mathematics to model fluid flow situations. The yardstick of success is how well the
results of numerical simulation agree with experiment in cases where careful
laboratory experiments can be established, and how well the simulations can predict
highly complex phenomena that can not be isolated in the laboratory (Sethian,
1993). As a developing science, CFD has received extensive attention throughout the
international community since the advent of the digital computer.
Advantages of using CFD
CFD has grown from a mathematical curiosity to become an essential tool in
almost every branch of fluid dynamics. It allows for a deep analysis of the fluid
mechanics and local effects in a lot of equipment. Most of the CFD results will give
an improved performance, better reliability, more confident scale-up, improved
product consistency, and higher plant productivity (Bakker et al., 2001). Some
design engineers actually use CFD to analyse new systems before deciding which and
how many validation tests need to be performed. The advantages of CFD can be
categorised as (Wanot, 1996):
It provides a detailed understanding of flow distribution, weight losses, mass and
heat transfer, particulate separation, etc. Consequently, all these will give plant
managers a much better and deeper understanding of what is happening in a
particular process or system.
It makes it possible to evaluate geometric changes with much less time and cost
than would be involved in laboratory testing.
It can answer many ‘what if’ questions in a short time.
Performing a CFD analysis
To perform a CFD analysis, the analyst will state the problem and use scientific
knowledge to express it mathematically. Then the CFD software package will
embody this knowledge and expresses the stated problem in scientific terms.
Finally, the computer will perform the calculations dictated by CFD software and
the analyst will inspect and interpret their results. In principle, three different major
tasks should be done to perform a CFD simulation (Shaw, 1992).
Pre-processing
All the tasks that take place before the numerical solution process are called
pre-processing. This includes problem thinking, meshing and generation of a
computational model.
Problem thinking is the first stage in using CFD. Before committing to practice,
it is worth thinking about the physics of the problem that is faced. In this stage the
analyst should consider the flow problem and try to understand as much as possible
about it. The second stage is meshing. In this stage the analyst should create the
shape of the problem domain that needs to be analysed.