Effects of Cu and Ag nano-particles on flow and heat transfer from permeable surfaces

Consideration is given to flow and heat transfer of nano-fluids over a permeable flat plate with convective boundary condition. The governing partial differential equations are transformed into ordinary differen- tial equations using similarity solutions, before being solved numerically. Two types of nano-fluids, Cu– water and Ag–water are considered. The effects of nano-particles volume fraction, the type of nano-par- ticles and permeability parameter on skin friction and convection heat transfer coefficient are studied and discussed. It is shown that the increment in skin friction is a considerable drawback imposed by Cu–water and Ag–water nano-fluids, especially in case of injection. In the cases of injection and imper- meable surface, increasing the nano-particles volume fraction results in augmentation of convection heat transfer rate. However, in the case of suction, adding Cu and Ag particles reduces the convection heat transfer coefficient at the surface in spite of thermal conductivity enhancement imposed by the nano- particles

Evolution in the Design of V-Shaped Highly Conductive Pathways Embedded in a Heat-Generating Piece

This paper presents the evolution of architecture of high conductivity pathways embedded into a heat generating body on the basis of Constructal theory. The main objective is to introduce new geometries for the highly conductive pathways, precisely configurations shaped as V. Four types of V-shaped inserts, evolving from “V1” to “V4,” have been comparatively considered. Geometric optimization of design is conducted to minimize the peak temperature of the heat generating piece. Many ideas emerged from this work: first of all, the numerical results demonstrated that the V-shaped pathways remarkably sur- pass the performance of some basic configurations already mentioned in literature, i.e., “I and X-shaped” pathways. Furthermore, the evolution of configurations from V1 to V4 resulted in a gradual reduction of the hot spot temperature, according to the principle of “optimal distribution of imperfections” that characterizes the constructal law