ABSTRACT Flow field design in PEM fuel cells has an important influence on both the power density and efficiency of fuel cell systems. In order to effectively utilize the active area, flow distribution and current density should be as homogenous as possible. In addition, pressure losses should be minimized. The main objective of this work is to provide a comprehensive study of the flow field characteristics for different parallel flow channel configurations. The investigated channel configurations are parallel with various cross-sectional configurations. For each channel configuration pressure drop, species mass fraction, velocity, and current distributions are numerically predicted. In addition, performance curves are presented and discussed. The predicted performance parameters are compared with the corresponding available experimental data. Based on the computed results the optimum channel design is selected. Detailed results are presented and discussed. The present work would help PEM fuel cell manufacturers, companies and researchers to choose the optimum configuration for their applications and products to achieve the best possible performance.

abstract The performance of Proton exchange membrane fuel cell (PEMFC) has been experimentally investigated. An experimental set-up was designed to study the effects of operating parameters such as cell temperature, gas humidification, and cell operating pressure on the performance of fuel cell. The results indicated that the output power increase with the increase of humidification ratio. Furthermore, an increase of cell pressure results in a significant increase of cell power. The results indicated that increasing of the temperature leads to a decrease of cell power. The results are explained and discussed in more details for different operational parameters.

This paper investigates carbon dioxide enrichment in commercial greenhouses to improve CO2 capture and utilization. The paper develops and numerically solves a mathematical model that simulates the CO2 capturing process through the coupled-non steady- energy and mass species (CO2, H2O) balance equations in the greenhouse components. The model accurately treats the solar radiation transport inside greenhouse. The realistic photosynthesis sub model selected in the present work is a mechanistic one applicable to the commonly planted C3 species. The present model allows strategies for CO2 enrichment and for cooling air inside sealed and ventilated greenhouses. These strategies keep both CO2 concentration and air temperature inside the greenhouse at the required prescribed value within small specified deviation. The validity and accuracy of the present mathematical model were verified through the agreement of its numerical results with the available experimental data in the literature. Numerical predictions of the present model was obtained for a case study to investigate the effects of environmental conditions, CO2 concentration enrichment level, and the cooling method on the cumulative amount of captured CO2 in the greenhouse that describe its performance.

This paper investigates carbon dioxide enrichment in commercial greenhouses to improve CO2 capture and utilization. The paper develops and numerically solves a mathematical model that simulates the CO2 capturing process through the coupled-non steady- energy and mass species (CO2, H2O) balance equations in the greenhouse components. The model accurately treats the solar radiation transport inside greenhouse. The realistic photosynthesis sub model selected in the present work is a mechanistic one applicable to the commonly planted C3 species. The present model allows strategies for CO2 enrichment and for cooling air inside sealed and ventilated greenhouses. These strategies keep both CO2 concentration and air temperature inside the greenhouse at the required prescribed value within small specified deviation. The validity and accuracy of the present mathematical model were verified through the agreement of its numerical results with the available experimental data in the literature. Numerical predictions of the present model was obtained for a case study to investigate the effects of environmental conditions, CO2 concentration enrichment level, and the cooling method on the cumulative amount of captured CO2 in the greenhouse that describe its performance.

This paper investigates carbon dioxide enrichment in commercial greenhouses to improve CO2 capture and utilization. The paper develops and numerically solves a mathematical model that simulates the CO2 capturing process through the coupled-non steady- energy and mass species (CO2, H2O) balance equations in the greenhouse components. The model accurately treats the solar radiation transport inside greenhouse. The realistic photosynthesis sub model selected in the present work is a mechanistic one applicable to the commonly planted C3 species. The present model allows strategies for CO2 enrichment and for cooling air inside sealed and ventilated greenhouses. These strategies keep both CO2 concentration and air temperature inside the greenhouse at the required prescribed value within small specified deviation. The validity and accuracy of the present mathematical model were verified through the agreement of its numerical results with the available experimental data in the literature. Numerical predictions of the present model was obtained for a case study to investigate the effects of environmental conditions, CO2 concentration enrichment level, and the cooling method on the cumulative amount of captured CO2 in the greenhouse that describe its performance.

Expansion and reduction are the two common end forming processes for tubes. In the tube end expansion process using a square punch, it is difficult to obtain a small corner radii due to the stretching of the tube around the punch corners. The wall thickness around the corners is small when compared to the side wall. Hence, a tube having a poor square look is formed. In this study, a 2-stage end expansion of a round tube end into a square section having an improved square look i.e. small corner radii and increase in wall thickness around corners is developed. In the 1st stage, the tube end is flared into a cone shape using a 30° conical die by axial compression. In the 2nd stage, the conical end of the tube is drawn through a taper square die using a conical bottom square punch, and a near square section is formed. A 15% ironing ratio is applied during the drawing process to flatten the side wall of the square. Experimental and FEM simulation were performed to evaluate and to verify the forming process. Although the height of the square section increases when the punch stroke at the 1st stage is increased. However, this increase is limited by the buckling of the pipe at the circular section of the thick blank tube. Since the conical end is drawn into a square section having different radial lengths, the bottom of the square section is uneven. The uneven bottom end is trimmed off in the later process. A square section having a maximum height of 32 mm after trimming is successfully obtained from the experiment for the punch stroke, S = 44 mm using an API 5 L tube.