Sharif Digital Repository

In this study, the effect of graphene nanoplatelets (GNP)/distilled water nanofluid on the thermal performance of evacuated tube solar collector (ETSC) water heater was experimentally investigated. The mass percentage of GNP was considered at 0.025, 0.5, 0.075 and 0.1 wt%. The physical and thermal properties of the GNP nanofluids including stability, specific heat capacity, viscosity and thermal conductivity were investigated. The thermal efficiency tests on the solar collector were carried out for varying volumetric flow rate of 0.5, 0.1, and 1.5 L/min while the ASHRAE standard 93–2003 was considered to calculate the efficiency of the collector. The results indicated that the solar... 

Numerical investigation of fluid flow structure and convective heat transfer due to a circular jet impinging on a rotating disk is performed. Temperature and convection heat transfer coefficient are calculated. Flow is considered to be steady, incompressible and turbulent. k-ε RNG model is used to model the turbulent flow. Results are compared with experimental data showing good agreement. Two new criteria are introduced and used to evaluate the performance of cooling process, the first is maximum temperature difference on the disk, and the second is the average temperature of the disk. The first parameter shows the uniformity of temperature distribution in the disk and the second shows the... 

A simple chemisorption method was used to graft on the surface of MWCNTs and Graphene nanoparticles to prepare stable kerosene-based MWCNTs and Graphene nanofluids. The prepared nanofluids remained stable for more than five months and no sedimentation was observed. Regarding the effect of temperature on thermo-physical properties, it was observed that although increasing nanoparticle concentration led to an increase in the fluid viscosity, it was negligible enough at lower nanoparticle loading. Moreover, adding nanoparticles to the base fluid did not have any noticeable impact on the fluid density which was negligible even at high concentrations. The thermal conductivity improvement was... 

A numerical study has been carried out to investigate the fluid flow structure and convective heat transfer due to a circular jet impinging on a rotating disk. The temperature distribution and convection heat transfer coefficient on the disk are calculated. Flow is considered to be steady, incompressible and turbulent. k-e RNG model is used to model the turbulent flow. Two new criteria are introduced and used to evaluate the performance of cooling process which are maximum temperature difference on the disk and the average temperature of the disk. The first parameter shows the uniformity of temperature distribution in the disk and the second shows the effect of both thermo physical... 

A thermo-elastic analysis coupled with a phase change model is employed to evaluate thermal stresses as well as progress of austenite decomposition after hot strip rolling operations. The thermo-mechanical finite element analysis is utilized to assess the distributions of temperature and thermal stresses during cooling while at the same time, a model based on the additivity rule is used to determine the rate of austenite to ferrite decomposition. The proposed model is applicable to multi-pass rolling schedules while the effects of different process parameters including the rolling speed and cooling configuration of the run-out table can be taken into account. In order to verify the... 

This study presents a comprehensive investigation on hydrodynamic and thermal transport properties of mixed electroosmotically and pressure driven flow in microtubes. Particular emphasis is given to investigating the combined consequences of viscous dissipation, non-uniform Joule heating, and variable thermophysical properties. Analytical solutions are obtained using the Debye-Hückel linearization and constant fluid properties assumption, while a numerical solution is presented for variable fluid properties and non-uniform distribution of Joule heating. The results indicate that, viscous heating effect is pronounced significantly when a favorable pressure gradient exists and cannot be... 

Vapor pressure and liquid density of 20 pure alcohols were correlated using an artificial neural network (ANN) system and statistical associating fluid theory (SAFT) equation of state. The SAFT equation has five adjustable parameters as temperature-independent segment diameter, square-well energy, number of segment per chain, association energy and association volume. These parameters can be obtained by a non-linear regression method using the experimental vapor pressure and liquid density data. In continue, the vapor pressure and liquid densities of pure alcohols were estimated by using an artificial neural network (ANN) system. In the neural network system, it is assumed that thermodynamic... 

Magnetite (Fe3O4) nanostructures with different morphologies including uniform nanoparticles, magnetic beads and nanorods were synthesized via a co-precipitation method. The synthesis process was performed at various temperatures in the presence of polyvinyl alcohol (PVA) at different concentrations. It is shown that small amounts of PVA act as a template in hot water (70 °C), leading to the oriented growth of Fe3O4 nanorods, which was confirmed by selected area electron diffraction. Individually coated magnetite nanoparticles and magnetic beads were formed at a relatively lower temperature of 30 °C in the folded polymer molecules due to the thermo-physical properties of PVA. When a moderate...