Forced Convective Heat Transfer Flow Research Articles

Numerical study of the influence of the geometrical aspect ratio and nanoparticles diameter on forced convection in a micro-channel heat sink of a nanofluid water/CuO based on a Brownian diffusion model

In order to cool electronic equipment with a high efficiency we can use the flow of a nanofluid in a rectangular micro-channel heat sink. The paper reports the results of the study of a hydrodynamically fully developed laminar forced convective heat transfer flow in two different geometries G1and G2. The study is numerical and was achieved using as nanofluid with and a single-phase approach. Calculations were first made with constant thermo-physical properties at and then made using temperature and nanoparticles diameter dependent thermo-physical properties based on a Brownian diffusion model. A three-dimensional conjugate heat transfer model was used and numerical simulations were based on a finite volume method. The simulations were made for a range of Reynolds numbers , for nanoparticle diameter in the range of and for a heat flux through the bottom surface of the heat sinks .The results of thermal and hydrodynamic fields show that nanofluids can provoke an increase in the local and average Nusselt numbers, a decrease of bottom surface local temperature and a slight decrease of the shear stress on the wall, particularly in the case of geometry G2. At the end of the study, the best geometry, volume fraction of nanofluid and nanoparticle diameter to be recommended for cooling were found based on minimum total thermal resistance of the micro-channel heat sink.

Multi-Objective Optimization of Force Convective Heat Transfer in a Stack of Horizontal Channels Using CFD and Genetic Algorithms: a Comparison with Asymptotic Method Results

In this paper, by combining the computational fluid dynamics (CFD) and NSGA II algorithm, the forced convective heat transfer flow in a stack of horizontal parallel plates has been multi-objectively optimized. In the optimization process, the distance between the plates in the set of parallel channels has been changed so as to simultaneously optimize the amount of heat transfer between the plates and fluid and the pressure drop of the fluid (maximization of heat transfer and minimization of pressure drop). The Pareto front, which illustrate the changes of the heat transfer from the plates and the pressure drop of fluid simultaneously, have been presented in the results section. This result contains important information regarding the thermal designing of stack of channels subjected to forced convective heat transfer. The Pareto front have been obtained for four different fluids that have different Prandtl (Pr) numbers (mercury, air, water and oil), and the results related to each fluid have been discussed. Finally, the multi-objective optimization results obtained in this paper have been compared with the results of the asymptotic analysis method (which is a single-objective method aimed at increasing the amount of heat transfer from plates) for internal fluid flows; and useful information has been obtained.

Study of Forced Convection of a Nanofluid Used as a Heat Carrier in a Microchannel Heat Sink

In order to cool electronic equipment with a high efficiency we can use the flow of a nanofluid in a micro-channel heat sink. The paper reports the results of the study of the laminar forced convective heat transfer flow in such geometries. The study is numerical and was achieved using the mixture water /γ-Al2O3 as nanofluid and a single-phase approach. The geometrical configuration used in the computations contains two inlet jets. Calculations were first made with constant thermo-physical properties and then made using temperature-dependent thermo-physical properties. The volume fraction of nanoparticles in the nanofluid mixture was taken as 0% (i.e. water only), 1% and 4%. A three-dimensional conjugate heat transfer model was used and numerical simulations were based on a finite volume method. The results of thermal and hydrodynamic fields show that nanofluids can provoke an increase in the average and local Nusselt numbers, a decrease of bottom surface local temperature and a slight decrease of the shear stress on the wall, when compared to predictions using constant properties and nanoparticles free water. The results are discussed for nanoparticle diameters of 38nm and a range of Reynolds number from 200 to 1200. Also the heat flux through the bottom surface of the heat sink was varied in the range q” =30W/cm2 to 120W/cm2.

A NUMERICAL PROCEDURE FOR THE LAMINAR HEAT TRANSFER IN CURVED SQUARE DUCTS

ABSTRACT The fully developed forced convective heat transfer flow in a curved square duct is studied, under a constant uniform wall temperature axially and peripherally. The continuity and momentum equations are solved with a new numerical-variational method denoted the CVP method. The method uses a nonstaggered grid for all primitive variables without introducing spurious oscillations in the solutions. Numerical results are presented for the effects of the curvature, the Dean number and the stream pressure gradient, on the velocity, the temperature, the friction factor, and the Nusselt number for fluids with Prandtl numbers 0.7 and 7. The accuracy of the method is discussed, and the results are in close agreement with those obtained by other methods.