HEAT TRANSFER: NUMERICAL MODELLING WITH EES APPLICATIONS

Abstract

Most heat transfer problems are complex, in the sense that in most cases there are no analytical (exact) solutions to obtain temperature fields or heat transfer rates/coefficients. Thermal energy systems, and in general energy systems, involve heat transfer processes and, therefore, also require approximate solutions. The approximate solution to non-linear systems of algebraic equations or differential equations is typically obtained with numerical methods, which became increasingly popular with the advent of affordable and fast computing. Second generation computer programs, such as Engineering Equation Solver (EES), do not even require conventional computer programming to solve mathematical problems, being based on the use of internal algorithms. The simulation of heat transfer processes and thermal energy systems widely benefits from such tools, allowing fast approximate solutions, and also the study of alternative processes/systems through the use of parametric analyses. This book is dedicated to the numerical simulation of thermal energy systems, with the use of the EES software tool. However, prior to the use of software tools, problem analysis is fundamental, in order to decide which type of model and degree of accuracy is acceptable. In this book, several heat transfer and thermal system problems are presented, coming from the energy engineering practice. After problem analysis and discussion, a numerical model is applied and solutions are obtained with the use of EES. Computed results are discussed, always trying to assess the effect of model assumptions on the results, and obtain conclusions which might be useful for the design of those systems. The book starts by revisiting some well-known numerical methods to solve equations that appear on most practical cases (chapter 1). Global and distributed models are distinguished. In the case of distributed models, the finite volumes approach is favoured. A brief presentation of the EES software follows (chapter 2); however, this book does not replace the software manual, and it is advisable that the reader has some prior experience of EES. Chapters 3 and 4 present several examples of thermal system modelling, with chapter 3 dedicated to global modelling and chapter 4 to distributed modelling.