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R. Ruiz-Femenia, R. Salcedo, M.F. Gómez-Rico

University of Alicante (SPAIN)
Computational Fluid Dynamics (CFD) is aimed to simulate the fluid flow and heat transfer processes. It is based on the finite element method (FEM), a numerical method to solve the differential partial equations describing the conservation of mass, momentum and energy within a fluid. Today, CFD is becoming an efficient tool, due to the enormous potential of computers and availability of software packages with built-in routines, which allow numerical problems to be solved quickly without the user having to program complex codes.
CFD can be helpful for teaching in Chemical Engineering. The basic operations of chemical engineering are based on mass, energy and momentum balances, which analytical resolution is extremely difficult without major simplifications. The use of CFD software allows the resolution of the full governing equations of the processes involved in chemical engineering operations, which allows students to visualize the actual behavior of systems, such as heat exchangers, separation units, pumping systems and even chemical reaction systems.
The implementation of the principles of the European Higher Education Area demands a transition from a teaching-based system to a learning-based system [1]. This can be accomplished by using active learning methods that promote a greater participation of students in the learning process. Traditionally, an active method in chemical engineering programs is the laboratory. However, there is not enough time to cover most of the main topics of the lectures and only a few laboratory experiments are developed to reinforce the theoretical concepts. Besides that, some physical phenomena are not easy to illustrate with simple experiments. This problem can be addressed by the introduction of the concept of virtual laboratory, which means to perform computer experiments for modeling traditional physical experiments [2]. Also, the virtual laboratory allows to determine quantities that cannot be directly measured during their physical experiments, or cannot be measured due to equipment limitations, such as phenomena occurring over very short distances or short time scales. The CFD software provides students a virtual laboratory in which they can simulate any process involving mass, energy or momentum transfer.
The aim of this work is to develop a 3D model with fluid-thermal interaction, solving the full Navier-Stokes equations coupled with the general heat transfer equations. As an example, we study a shell and tube heat exchanger, where a hot fluid enters into the shell and the cooling fluid flows through the tubes. With this model the chemical engineering students obtain a clear understanding of the physical processes going on inside the complex industrial scale equipment. The use of this virtual laboratory also develops autonomous learning habits and the student's self-reflection, since the computer experiments allow students to design easily their own experiments (i.e. study the influence of variables and design parameters). This fact increases the pedagogical value of the tool proposed.

[1] S.L. Yagüe, M.T.G. Cubero, S.B. Rodríguez, P.A. García Encina, G.G. Benito, M.Á.U. Alonso, Adaptation of the chemical engineering degree to the EEES. Methodological learning process and evaluation changes, Prague, 2006.
[2] W. Clark, D. Dibiasio, Computer simulation of laboratory experiments for enhanced learning, Honolulu, HI, 2007.