Effect Of Channel Depth Research Articles

The Effect of Channel Depth on Joint Quality in Cu/AISI 1040 Materials Joined by Mechanical Locking Method

The Effect of Channel Depth on Joint Quality in Cu/AISI 1040 Materials Joined by Mechanical Locking Method

Effect of Anode Channel Depth on Cell Performance in Polymer Electrolyte Membrane Water Electrolyser

The Bipolar/Flow field plate is a vital component of Polymer Electrolyte Membrane Water Electrolysers (PEMWE) which enables electronic conduction, provide mechanical support to the cell and facilitates mass transport of liquid water and produced gases to and from the electrocatalyst surface. From a mass transport viewpoint, especially at high current density operation, optimizing the dimensions and configuration of the flow field plate is crucial to reducing mass transport limitation and achieve improved cell performance. This work investigates the effect of channel depth of the anode flow field plate on performance of a PEM Water Electrolyser using polarization curve and Electrochemical Impedance Spectroscopy technique. A single electrolyser cell with flow field plate having a single straight channel was employed having the channel depth varied from 3.0 mm to 8.0 mm and the cell performance was studied at current densities up to 2 A/cm2. The impedance spectroscopy results show that the effect of channel depth on cell performance is negligible at low and medium current densities, but significant at high current densities. The result indicate that the two-phase flow liquid/gas interactions in the flow channel and the flow regime of operation have a direct influence on mass transport losses and overall performance in the PEM Water Electrolyser. Furthermore, the impedance spectroscopy result at high current densities shows that, generally, deeper channels show better performance than shallower channels which suggests that the effective mass transfer area at the surface of the gas diffusion layer increases with increase in channel depth thus yielding improved mass transport. However, the best performance was observed at 4.5 mm depth which suggests that there exist an optimal channel depth where an increase or decrease in depth would lead to loss of performance. This is attributed to the trade-off between reduced liquid flow velocity and reduced surface coverage of gas bubble/slug in the channel with increasing channel depth in the PEMWE flow field. Fig 1: Effect of channel depth on cell performance at (a) low, (b) medium and (c) high current density at water flow rate of 40 mL/min and inlet water temperature of 80°C. Figure 1

Effect of geometrical parameters of open microchannel surfaces on pool boiling heat transfer

This study focuses on the effect of channel depth on the heat transfer coefficient during nucleate pool boiling. Experimental studies were performed for saturated deionized water, and Novec-649 as working fluids at atmospheric pressure. Copper surfaces were modified to form microchannels with different geometrical properties. The microchannels were from 0.2 mm to 0.4 mm deep, 0.3 mm wide and spaced every 0.1 mm. The experiment was conducted for increasing heat flux up to the critical heat flux point. The surface modification provided an appreciably higher heat transfer coefficient compared to the smooth surface for all boiling liquids. The maximum heat transfer coefficient obtained exceeded 60 kW/m2 K.

Design and thermal analysis of a water-cooled DSC module

Elevated working temperatures reduce the efficiency of dye-sensitized solar cells (DSCs), and effective temperature regulation protects them from the undesirable efficiency loss. In this work, a semi-transparent DSC module equipped with a cooling system was designed and constructed for application in buildings, the temperature and output performance of the modules with or without cooling treatment were investigated. The test results showed the cooling system could noticeably improve the power generation and reduce the module temperature. Moreover, we established a mathematical model to analyze the modules’ thermal performances, and introduced the concept of cooling efficiency to evaluate the cooling effect. The model accuracy have been validated utilizing measured data, and the effects of channel depth and mass flow rate on the module temperature and cooling efficiency were further theoretically studied. The combined DSC module has been found to have a good application prospect in building integrated photovoltaic (BIPV), and the numerical results are important in system design.

Analysis on the performance of a flat-plate volumetric solar collector using blended plasmonic nanofluid

In this paper, thermal performance of a flat-plate volumetric solar collector using a blended plasmonic nanofluid as its heat transfer fluid was investigated. The blended plasmonic nanofluid used in the experiment was manufactured based on three different aspect ratios of gold nanorods (AuNRs), and it was designed to have broad-band absorption over the visible and near-infrared spectrum. The conversion process of solar radiation to heat in the blended plasmonic nanofluid was verified experimentally by measuring the temperature distribution inside the nanofluid under illumination of a tungsten–halogen lamp and by comparing it with the simulation result. Through the theoretical investigation of a flat-plate volumetric solar collector, effects of channel depth, channel length, mass flow rate, and the magnitude absorption coefficient of the blended plasmonic nanofluid were characterized in order to establish a basic design. The results of this study will facilitate the development of highly efficient solar thermal collectors using plasmonic nanofluids.

Effect of Channel Depth and Cell Temperature on the Performance of a Direct Methanol Fuel Cell

The main goal of this study is to analyze the performance of the direct methanol single cell using three channel depths at various cell temperatures. The membrane electrode assembly (MEA) used Nafion® 117, by loading a Pt-Ru (4 mg/cm2) catalyst at the anode and Pt-black (4 mg/cm2) catalyst at the cathode. The active area of the MEA was 100 cm (Jung et al., 2009, “Investigation of Flow Bed Design in Direct Methanol Fuel Cell,” J. Solid State Electrochem., 13, pp. 1455–1465). In these sets of experiments, anode and cathode channel depth were varied simultaneously. The cell performance is improved with an increase of temperature in a certain range because the conductivity of the membrane and the reaction kinetics at both the anode and cathode are increased. Also, when the channel depth of the bipolar plate is decreased from 2.0 to 1.0 mm, the cell performance increases. The decreased channel depth leads to an increase in the linear velocity of reactants and products.

Effect of Channel Depth of PEM Fuel Cell on its Peformance

The electrode structure, especially for the channel depth, plays an important role on the performance of the proton exchange membrane (PEM) fuel cell. In this paper, the performance and electrochemical impedance of the PEM fuel cell are measured experimentally. The simulation results of mass transfer and equivalent circuit for the electrochemical impedance are used to explain the effect of the channel depth on the performance of the PEM fuel cell. These results show that when the cell temperature is lower than the gas humidification temperatures, the performance of PEM fuel cell with the channel depth of 2mm is better than that of 1mm; there is more liquid water saturation in cathode for the channel depth of 1mm than that for the channel depth of 2mm. The charge transfer resistance of the PEM fuel cell with the channel depth of 2mm is less than that with the channel depth of 1mm. These results are very helpful to optimizing structure of the PEM fuel cell.

Mass diffusion‐based separation of sugars in a microfluidic contactor with nanofiltration membranes

Processes such as chromatographic separation and nanofiltration can remove low molecular weight sugars from liquid mixtures of oligosaccharides. As an alternative for the separation of such liquid mixtures, we studied mass diffusion separation of such sugars in a microfluidic device with incorporated nanofiltration membranes. This separation method is based on differences between diffusivities of components and does not require high transmembrane pressures. The effects of channel depth and flow rate were studied in experiments. The key parameters selectivity and rejection increased with increasing channel depth due to increased external mass transfer limitations. Among the studied membranes, the obtained selectivities and rejections correlated to the specified retention values by the manufacturers. Compared to more conventional nanofiltration where high pressure forces solutes through membranes, we obtained corresponding selectivities and fluxes of only an order of magnitude smaller. Simulated results indicated that with optimized microchannel and membrane dimensions, the presented separation process can compete with currently available separation technologies.

Design for Wall Shape Profile of a Millimeter-Scale Air-Heating Channel by Integrating Three-Dimensional CFD Code with Optimization Method

Optimization for the wall shape profile of a millimeter-scale air-heating channel of finite depth has been performed by a computer-aided design approach. The present design approach involves a direct problem solver and a numerical optimizer. A commercial software package is used as the direct problem solver, which is able to provide the numerical predictions of pressure drop and heat transfer performance for the three-dimensional air flows in the channel with an irregular wall shape profile. An objective function is calculated based on the numerical data of average pressure drop and heat flux provided by the direct problem solver. The numerical optimizer is a self-developed program which is used to continuously adjust the channel wall shape profile so as to minimize the objective function in the optimization process. In this article, the interface between the commercial software package and the self-developed optimizer has been established for connection. A scheme incorporating a point-by-point technique with a redistribution method is employed to construct the irregular wall shape profiles. It is found that the search process is robust and is independent of the initial guess. The optimal shapes at different inlet velocities are obtained, and the effect of channel depth on the optimal shape is also investigated.

Extraction of channel carrier concentration using C-V method for SiC buried-channel MOSFET

A theoretical and experimental study on extracting channel carrier concentration for 4H-SiC buried channel MOSFET has been carried out. The distortion of C-V curve caused by the existence of p-n junction in buried channel MOS structure would affect the extracting result, and the interface states on SiO2/SiC interface make extracting result deviate from true channel carrier concentration. In this paper, firstly, a theoretical analysis about the effects of channel depth and interface state on extracting result is made. Then the C-V curves for buried-channel MOS structure with two different channel depth are presented from which the channel carrier concentration is extracted. In the measurement of C-V curves, three different sweep velocities are used to analyze the effect of interface states. The theoretical results agree with experimental results.

Examination of optimal separator shape of polymer electrolyte fuel cell with numerical analysis including the effect of gas flow through gas diffusion layer

This work concentrates on the effects of channel depth and separator shape on cell output performance, current density distribution and gas flow condition in various conditions with PEFC numerical analysis model including gas flow through GDL. When GDL effective porosity was small, the effect of gas flow through GDL which was changed by channel depth on cell output performance became large. However, current density distribution was ununiform. As GDL permeability became larger, cell output density increased, but current density and gas flow rate distribution were ununiform. From the results of changing the gas flow rate, it was found that the ratio of the minimum gas flow rate to the inlet flow rate depended on channel depth. Furthermore, the optimal separator, which increased output density and made the current density distribution and gas flow rate distribution uniform, was examined. It was also found that cell performance had possible to be developed by improving the turning point of the serpentine separator.

Forced convection of low temperature nitrogen gas in rectangular channels with small aspect ratio

Forced convection of low temperature (80–150 K) nitrogen gas flowing through rectangular channels with hydraulic diameters of 0.513–1.814 mm and aspect ratios of 0.013–0.048 has been investigated experimentally. Close attention was focused on the effects of channel depth and heat addition on the heat transfer and flow characteristics, the transition from laminar to turbulent flow and the existence of an optimum channel depth. A dimensionless heating number was adopted to characterize the heating effect. The experimental correlation developed for the Nusselt number shows that the heat addition is the most important effect, followed by the channel aspect ratio, Reynolds number and Prandtl number.

Analysis of channel-geometry effects on separation efficiency in rectangular-capillary electrochromatography columns

A three-dimensional random walk model was developed to evaluate the impact of column geometry on separation efficiency in chromatography systems driven by electroosmotic flow. Contributions of injection plug length, cross-sectional area of channels, and aspect ratio of rectangular channels were examined in these simulation studies. Sample plug length had no impact on efficiency until it exceeded roughly 0.4% of the channel length. Plate height increased rapidly with increasing k′ as expected, almost doubling in going from k′=0.25 to 0.35. Channel geometry also had a major effect on efficiency. Plate height increased sharply in rectangular channel columns until the channel aspect ratio reached 4–8. But the effect of channel depth was even more dramatic. Minimum plate height ( H min) was roughly half that of the channel depth in ideal cases. H min in a 10×2 μm channel was at 1.6 mm s −1. Rectangular channels comparable to those obtained by microfabrication are equivalent to packed column capillary electrochromatography columns in all cases.