ABSTRACT
Heat transfer can be enhanced by employing techniques and methodologies, such as increasing either the heat transfer surface or the heat transfer coef-„cient between the Šuid and the surface that provide high heat transfer rates in small volumes. This can be accomplished in two ways: either enhancing the heat transfer capability of the Šuid itself by using nanoparticles. The new techniques and methodologies, the particular materials, the strong
CONTENTS
5.1 Introduction ................................................................................................ 165 5.2 Production of Nanoparticles and NanoŠuids ....................................... 169 5.3 Applications and Potential Bene„ts ........................................................ 171 5.4 NanoŠuids Simulation Techniques ......................................................... 172
5.4.1 Single-Phase Model ....................................................................... 172 5.4.2 Discrete-Phase Model.................................................................... 173 5.4.3 Mixture Model ............................................................................... 176 5.4.4 Turbulence Modelling ................................................................... 177
5.5 Thermophysical Properties of NanoŠuids ............................................. 178 5.5.1 Effective Density ............................................................................ 178 5.5.2 Effective Heat Capacity ................................................................. 179 5.5.3 Thermal Expansion Coef„cient of NanoŠuids .......................... 179 5.5.4 Thermal Conductivity of NanoŠuids ......................................... 180 5.5.5 Effective Viscosity .......................................................................... 182
5.6 Some Results of Convection in NanoŠuids ............................................ 184 5.6.1 Results and Discussion for Case 1 ............................................... 185 5.6.2 Results and Discussion for Case 2 ............................................... 189 5.6.3 Results and Discussion for Case 3 ............................................... 191
Nomenclature ...................................................................................................... 194 References ............................................................................................................. 196
miniaturisation and the employment of nanoparticles in the Šuids require the evaluation of new heat transfer modes. In the last years, research activities have been very intensive in order to solve these problems, and several novel techniques have been proposed and studied theoretically, numerically and experimentally. Moreover, a deeper knowledge of the phenomenological aspects allows a better thermal design and the optimisation of thermal con„gurations.
