Sharif Digital Repository

The monolithic catalytic converter still is the main pollution control device for modern vehicles in order to reach the ever-increasing legislative demands for low emission standards. The catalytic converters require a large expansion from the exhaust pipe to the front face of the monolith. Unfortunately, packaging constraints often do not permit the use of long diffusers. Hence, flow separation within the diffuser leads to a non-uniform flow distribution across the monolith. A uniform flow distribution at the inlet monolith face is favorable for the conversion efficiency as well as the durability of the catalytic converter. Therefore the main problem is to optimize the flow distribution at... 

In this study, the optimal location of baffle in the header of air-to-air plate heat exchangers and the geometry of the header and the effects of triangular fins arrays on the effectiveness were numerically investigated for different flow rates and Reynolds numbers on different models. The main purpose of inlet baffle and geometry changes is to improve the pattern of flow distribution and assist flow uniformity. The investigations show that the optimal location of the inlet baffle with high Reynolds numbers has an insignificant effect on effectiveness, while with Reynolds numbers 250-3000, the effectiveness is affected significantly by baffle location. On the other hand, the reduction in... 

This study concentrates on the improvement in the performance of PEM fuel cells through optimization of the channel dimensions and patterns in the velocity and pressure fields in bipolar plates. For design and optimization purposes, a 2D numerical simulation of the flow distribution based on the Nervier-Stokes equations using individual computer code has been done. The outcome of the numerical simulations showed excellent agreement with the experimental results in previous works. Finally numerical simulation has been conducted to investigate the advantages of conventional patterns with inspiration from leaf flow pattern. It was found that both velocity and pressure fields are very uniform in... 

The flow behavior around a cam shaped tube in a cross flow has been investigated experimentally using flow visualization and pressure distribution measurements. The range of attack angle and Reynolds number based on an equivalent circular diameter are within 0 < α < 360° and 2×104Reeq <3.4×104, respectively. The pressure drag features are clarified in relation to the flow behavior around the tube. It is found that the highest pressure drag coefficient occurs at α = 90° and 270° over the whole range of Reynolds number. Results show that the pressure drag coefficient of the cam - shaped tube is lower than that of a circular tube with the same surface area for more of the attack angles  

The efficiency of proton exchange membrane (PEM) fuel cell is straightly correlated to the bipolar plate design and fluid channel arrangements. Higher produced energy can be attained by optimal design of type, size, or patterns of the channels. Previous researches showed that the bipolar plate channel design has a considerable effect on reactant distribution uniformity as well as humidity control in PEM fuel cells. This paper concentrates on enhancements in the fuel cell performance by optimization of bipolar plate design and channels configurations. A numerical model of flow distribution based on Navier-Stokes equations using individual computer code is presented. The results gained from... 

This paper investigates the optimal operation of distribution feeder reconfiguration (DFR) strategy in the smart grids with high penetration of plug-in electric vehicles (PEVs) and correlated wind power generation. The increased utilization of PEVs in the system with stochastic volatile behavior along with the high penetration of renewable power sources such as wind turbines (WTs) can create new challenges in the system that will affect the DFR strategy greatly. In order to reach the most efficiency from the PEVs, the idea of vehicle-to-grid (V2G) is employed in this paper to make a bidirectional power flow (either charging/discharging or idle mode) strategy when providing the main charging... 

Proton exchange membrane (PEM) fuel cell performance is directly related to the bipolar plate design and their channels pattern. Power enhancements can be achieved by optimal design of the type, size, or patterns of the channels. It has been realized that the bipolar plate design has significant role on reactant transport as well as water management in a PEM Fuel cell. Present work concentrates on improvements in the fuel cell performance by optimization of flow-field design and channels configurations. A three-dimensional, multi-component numerical model of flow distribution based on Navier-Stokes equations using individual computer code is presented. The simulation results showed excellent...