Numerical simulations of heat and mass transfer phenomena applied to flat-plate solar collectors.

Numerical methods and simulations in fluid dynamics and Heat Transfer (HT) are constantly growing in terms of number of both courses offered at universities and active researches in the field. Nowadays, Computational Fluid Dynamics (CFD) codes are being consolidated as design tools by the industry and both commercial and open-source codes are available. Anyway, users of CFD need to have a fully understanding of the numerical methods implemented in these more complex software in order to give meaning and accuracy to their results. Therefore, the two main objectives of this project are: firstly, to acquire a basic training in the numerical resolution of the governing equations in heat transfer and fluid dynamics problems, acquiring the skills to critically judge their quality through validation techniques and, secondly, apply the developed knowledge to a real-world case like the heat transfer study of a flat-plate solar collector. The project is organized like a work-flow that starts from the most basic numerical methods and problems to the most complex ones; finalizing the work with a study of a flat-plate collector. Chapter 1. ‘Introduction’ contains the work-flow description and a brief presentation of all the case-study analysed. Chapter 2. ’Discretization methods and solvers’ contains the fundamental numerical methods with which physical phenomena, described through appropriate differential equations, are analysed. Chapter 2. ‘Heat conduction methods’ is the construction base of all the methods implemented in this work, therefore emphasis on concepts and calculation details are given here. Chapter 4. ‘Convection and diffusion’ is focused on the resolution of convection and diffusion problems, with the flow field known in advance. The Smith-Hutton problem is addressed in this chapter since many of the features commonly encountered in practical convection-diffusion problems. Different numerical schemes are presented in and their pros and cons are described. The calculation of the velocity field itself is finally treated in Chapter 5. ‘Incompressible flow method using the Navier-Stokes equations’. This chapter describes the implementation of the Fractional Step Method (FSM) in the solution of the Navier-Stokes equations with the aim to obtain solutions for two famous benchmark problems: the Lid-Driven Cavity problem and the Differentially Heated Cavity problem (DHC). In the DHC problem, momentum equations are coupled with the energy equation. The problems presented and solved are intended to be a material base over the analysis of flat-plate solar collector in Chapter 6. ’Numerical analysis of a flat-plate solar collector’. In the last chapter an analysis of a typical flat-plate solar collector is performed, with a simple one-dimensional (1D) model. The heat transfer between the absorber plate and the cover is then investigated deeply and the results are compared to the ones obtained with the 1D model.