فهرست مطالب puriya mohammad gholy nejad

In this study, the thermal characteristics of turbulent nanofluid flow in a helical tube in the tube heat exchanger (HTTHE) were assessed numerically through computational fluid dynamics (CFD) simulation. The findings of both the turbulent models: realizable k-epsion (k-ε) and re-normalisation group (RNG) k-epsilon were compared. The temperature distribution contours show that realizable and RNG k-ε models, together with the swirl dominated flow are of more uniform temperature distributions. The proper prediction of two layer theory leads to having a uniform temperature distribution and proper dimensionless wall distance (Y+). The turbulent flow and heat transfer of two nanofluids (SiO2, Al2O3) and base fluid with respect to swirl dominated flow was simulated through the RNG model. The effects of the concentration of nanoparticles on heat transfer characteristics in HTTHE and two turbulent models were analyzed in a comprehensive manner. It is concluded that up to 1% concentration of SiO2 and 1% concentration of Al2O3, similar heat transfer characteristics are observed. Comparison between the CFD results with the predicted values for friction factor coefficient (f) and Nusselt number (Nu) calculated through experimental correlations indicate the maximum errors of 6.56% and 0.27%, respectively.

An electrochemical analysis on a single channel PEM fuel cell was carried out by Computational Fuel Cell Dynamics (CFCD). The objective was to assess the latest developments regarding the effects of change in the current collector materials, porosity of electrodes and gas diffusion layer on the fuel cell power density. Graphite, as the most applicable current collector material, was applied followed by Aluminum and Titanium. It was found that titanium enhances the performance of the fuel cell as compared to the graphite and aluminum. Other results obtained were: the total porosity of electrode's layers does not have a significant effect on power density. At higher porosity of gas diffusion layer at voltages higher than 0.5 is favorable in gas diffusion, which leads to better performance. A numerical model, based on the assessment of basic best practice guidelines for CFCD, was developed that led to reasonably good agreement with the experimental results.