Stack Of Plates Research Articles

Sb2O3 microrods: self-assembly phenomena, luminescence and phase transition

Sb2O3 microrods of the orthorhombic phase have been grown by evaporation deposition with Sb powder as precursor. The rods, of rectangular cross section, are composed of weakly bonded stacks of tiny plates of few hundreds of nanometres, which self-assembled during the growth process parallel to the growth axis. Photoluminescence (PL) spectra show resonance peaks in the ultraviolet-blue region related to optical cavity modes across the cross sections of the rods. Local phase transformation from the orthorhombic to the cubic Sb2O3 phase has been induced by long irradiation with the 325 nm laser light, as confirmed by Raman spectroscopy and PL.

Influence of stack plate thickness and voltage input on the performance of loudspeaker-driven thermoacoustic refrigerator

A loudspeaker-driven thermoacoustic refrigerator has been built and tested to gain understanding of its thermal performance and the cooling rate. The influence of plate thickness made of acrylic sheet was experimentally investigated by varying plate thickness of the stack, 0.15 mm, 0.5 mm and 1 mm, respectively. The experiments were conducted with various voltage input to the driver starting from setting 4 to 9 voltage peak-to-peak. The temperatures at both ends of the stack were acquired. For all variations, thermoacoustic cooling effect occurred in seconds and escalated rapidly in two minutes and became stable in ten-minute time. The experimental results showed that higher voltage input yielded higher thermal performance and faster cooling rate. For each set of experiment, the operating frequency and other parameters of the stack were kept unchanged. The experimental results show that the thermal performance and cooling rate increase with the decrease of plate thickness. The largest temperature difference, 14.8°C, was achieved with 0.1 mm plate thickness at voltage setting 9. However, the thermal performance gained for 0.5 mm plate thickness voltage setting of 9, was arguably the optimum thickness in terms of advantages in the ease of fabricating the stack and more consistent cooling.

Experimental study on the influence of the porosity of parallel plate stack on the temperature decrease of a thermoacoustic refrigerator

Thermoacoustic refrigerators are cooling devices which are environmentally friendly because they don't use hazardous gases like chlorofuorocarbons (CFCs) or hydrofuorocarbons (HFCs) but rather air or inert gases as working medium. They apply sound wave with high intensity to pump heat from the cold to hot the regions through a stack in a resonator tube. One of the important parameters of thermoacoustic refrigerators is the porosity (blockage ratio) of stack which is a fraction of cross sectional area of the resonator unblocked for the gas movement by the stack. This paper describes an experimental study on how the porosity of parallel plate stack affects the temperature decrease of a thermoacoustic refrigerator. The porosity of parallel plate stack is specified by the thickness of plates and the spacing between plates. We measured the maximum temperature decreases of thermacoustic refrigerator using stacks with various porosities in the range of 0.5 – 0.85, with plate spacing from 0.5 mm to 1.5 mm and plate thicknesses 0.3 mm, 0.4 mm, and 0.5 mm. The measurements were done with two resonators with length of 0.8 m and 1.0 m, with air at atmospheric pressure and room temperature, correspond to thermal penetration depths (δκ) of 0.26 mm and 0.29 mm, respectively. It was found that there is an optimum porosity which gives the largest temperature decreases, and there is a tendency that the optimum porosity shifts to a larger value and the temperature decrease become larger when we used a stack with thinner plates. On the other hand, the study on the dependence of the temperature decrease on the plate thickness and the plate spacing reveals more useful information than that on the stack porosity itself. We found that stack with thinner plates tends to give larger temperature decrease, and the plate spacing of around 4δκ leads to the largest temperature decrease.

High Temperature Oxidation of Ferritic Steels for Solid Oxide Electrolysis Stacks

Oxidation rates of ferritic steels used as interconnector plates in Solid Oxide Electrolysis Stacks are of concern as they may be determining for the life time of the technology. In this study oxidation experiments were carried out for up to 1000 hours in hydrogen-side and oxygen-side simulated atmospheres at 800°C. Four commercially available alloys: Crofer 22 APU, Crofer 22 H, AL29-4, E-Brite were characterized in humidified hydrogen. One alloy, Crofer 22 APU was also characterized in pure oxygen both in the as-prepared state and after application of a protective coating. Best corrosion resistance in humidified hydrogen atmosphere was observed for Crofer 22 APU and Crofer 22 H alloys. Corrosion rates for Crofer 22 APU measured in humidified hydrogen are similar to the corrosion rates measured in air. Both coatings of plasma sprayed LSM and dual layer coatings (Co3O4/LSM-Co3O4) applied by wet spraying were found to reduce corrosion rates in pure oxygen significantly.

The influence of flow maldistribution on the performance of inhomogeneous parallel plate heat exchangers

The heat transfer performance of inhomogeneous parallel plate heat exchangers in transient operation is investigated using an established model. A performance parameter, denoted the Nusselt-scaling factor, is used as benchmark and calculated using a well-established single blow technique. A sample of 50 random stacks having equal average channel thicknesses with 20 channels each are used to provide a statistical base. The standard deviation of the stacks is varied as are the flow rate (Reynolds number) and the thermal conductivity of the solid heat exchanger material.It is found that the heat transfer performance of inhomogeneous stacks of parallel plates may be reduced significantly due to the maldistribution of the fluid flow compared to the ideal homogeneous case. The individual channels experience different flow velocities and this further induces an inter-channel thermal cross talk.

도금된 폴리카보네이트 분리판을 이용한 공기 호흡형 고분자 전해질막 연료전지에 관한 연구

본 연구에서는 도금된 폴리카보네이트를 사용하여 공기호흡형 고분자 전해질막 연료전지의 분리판을 제작하였다. 도금층은 구리 40μm, 니켈 10μm, 금 0.3μm 로 구성되었으며, 구리는 전기 전도층, 니켈은 구리와 금의 결합, 금은 도금층의 부식을 방지하기 위해 사용되었다. 본 분리판을 사용하여 성능을 평가한 결과 120mW/cm<SUP>2</SUP> 의 전력 밀도를 보였으며 이는 동일한 조건에서 그라파이트 분리판을 사용했을 때의 전력밀도와 거의 차이가 나지 않았다. 또한 평판형 12 층 스택의 공기호흡형 연료전지를 구성한 결과 각 전지당 132.7mW/cm<SUP>2</SUP> 의 성능을 보였으며 이를 12 시간 운전해본 결과 안정적인 성능을 보여 공기호흡형 고분자 전해질 연료전지의 분리판으로 적합함을 확인하였다.

Development of Open Pore Copper Foams to Use as Bipolar Plates in Polymer Electrolyte Membrane Fuel Cell Stacks

Polymer electrolyte membrane fuel cell stacks contain fluid flow plates, generally known as bipolar plates; which are traditionally made from graphite based materials. Brittleness of graphite enforces manufacturers to fabricate bipolar plates in great thicknesses which severely reduce the stack's power to weight ratio. Therefore, recently the use of low permeability open pore metallic foams has been attended. This survey is focused on development of powder metallurgy method to manufacture copper foams for use as bipolar plates. After three-point flexural tests and air permeability measurements, it was shown that powder metallurgy method based on using space holder agent has high capability to produce functionally graded foams in order to substitute conventional stack fluid field plates.

A02 高性能模型スターリングエンジンにおける流動と軸出力の特性(スターリングサイクル機器及び関連要素と応用システム(1))

Flow resistance, heat transfer and indicated work were measured for a high performance model Stirling engine. Flow resistance was measured for Stacks of honeycomb plates and of metal gauzes. Flow resistance for honeycomb plate was correlated with Uchida's analytical solution with a 1.2 factor. That for wire gauze was roughly doubled. Compression and expansion were carried out almost adiabatically. Heat transfer in isometric heating and cooling was comparable to that calculated for an isothermal model. In spite of low heat transfer on compression and expansion, indicated work corresponds to that calculated with isothermal model.

Demonstrating of a Standing Wave - Thermoacoustic Refrigerator

This manuscript begins with a full description of Thermoacoustic Refrigerator (TAR) technology followed an analysis of the elements necessary for successfully designing the various components of a TAR. The authors developed and tested a standing wave thermoacoustic refrigerator (TAR) to study the effects of stack plate thickness, load and stack temperature variation on TAR performance. They then used a CFD simulation to simulate the performance of the TAR, particularly the temperature and velocity within.

Experimental and theoretical investigation of thermoacoustic prime mover

The thermoacoustic prime mover is part of an interesting class of prime movers that can be used to generate clean energy and to drive cryogenic refrigeration systems. A thermoacoustic prime mover has been built based on the linear thermoacoustic model, which consumes thermal energy and produces acoustic energy. The objective of this article is to design a thermoacoustic prime mover that can be used as a drive for a thermoacoustic refrigerator. It is found that stack plate length and its distance from the closed end have a significant effect on the thermal efficiency of the prime mover. For different stack center positions, there is an optimum length of stack plate that has a significant effect on the performance of the thermoacoustic prime mover in terms of temperature gradient, frequency, and pressure amplitude. In this study, the experiments have been done on the thermoacoustic prime mover by varying stack position and its length with constant blockage ratio and resonator length. The results obtained from the experiments have been compared to the theoretical results acquired from DeltaEc Software.

The influence of demagnetizing effects on the performance of active magnetic regenerators

Active magnetic regenerators (AMR) comprise an involved, multi-physics problem including heat transfer, fluid flow, magnetocaloric properties, and demagnetizing fields. In this paper a method is developed that combines previously published models that simulate a parallel-plate AMR and the magnetostatics of a stack of parallel plates, respectively. Such a coupling is non-trivial due to the significant increase in computational time, and a simplified scheme is thus developed and validated resulting in little extra computational effort needed. A range of geometrical and operating parameters are varied, and the results show that not only do demagnetizing effects have a significant impact on the AMR performance, but the magnitude of the effect is very sensitive to a range of parameters such as stack geometry (number of plates, dimensions of the plates and flow channels, and overall dimensions of the stack), orientation of the applied field, and the operating conditions of the AMR (such as thermal utilization).

Active negative-index metamaterial powered by an electron beam

A novel active negative index metamaterial that derives its gain from an electron beam is intro- duced. The metamaterial consists of a stack of equidistant parallel metal plates perforated by a periodic array of holes shaped as complementary split-ring resonators. It is shown that this structure supports a negative-index transverse magnetic electromagnetic mode that can resonantly interact with a relativistic electron beam. Such metamaterial can be used as a coherent radiation source or a particle accelerator.

Silver micro-, submicro- and nano-crystals using bovine bone as template. Formation of a silver/bovine bone composite

Bovine bone is employed as a template to support silver particles using the simple impregnation-reduction method of synthesis. SEM studies show that micro, submicro and nano silver crystals grow up on the surface and around bone pores with high faceted structures (hexagons and squares). More complex silver structures are also generated from the stacking of irregular silver plates. UV–vis spectra of silver nanoparticles in the silver-bone composites show the surface plasmon resonance band of Ag nanoparticles at 411nm. TEM studies show Ag-nanoparticles below 50nm with a FCC structure as confirmed by SAED.

Building Blocks for the Development of an Interface for High-Throughput Thin Layer Chromatography/Ambient Mass Spectrometric Analysis: A Green Methodology

Interfacing thin layer chromatography (TLC) with ambient mass spectrometry (AMS) has been an important area of analytical chemistry because of its capability to rapidly separate and characterize the chemical compounds. In this study, we have developed a high-throughput TLC-AMS system using building blocks to deal, deliver, and collect the TLC plate through an electrospray-assisted laser desorption ionization (ELDI) source. This is the first demonstration of the use of building blocks to construct and test the TLC-MS interfacing system. With the advantages of being readily available, cheap, reusable, and extremely easy to modify without consuming any material or reagent, the use of building blocks to develop the TLC-AMS interface is undoubtedly a green methodology. The TLC plate delivery system consists of a storage box, plate dealing component, conveyer, light sensor, and plate collecting box. During a TLC-AMS analysis, the TLC plate was sent to the conveyer from a stack of TLC plates placed in the storage box. As the TLC plate passed through the ELDI source, the chemical compounds separated on the plate would be desorbed by laser desorption and subsequently postionized by electrospray ionization. The samples, including a mixture of synthetic dyes and extracts of pharmaceutical drugs, were analyzed to demonstrate the capability of this TLC-ELDI/MS system for high-throughput analysis.

Reconstructing Historical Light Curves of Symbiotic Stars and Novae

Abstract We reconstructed photometric histories of symbiotic stars and novae from direct inspection and measurement of photographic plates preserved at historical archives. We have completed the digging of the rich Asiago archive, and have started working on the Harvard plate stack, while other plate collections should be added soon. For homogeneity, we use the same UBV RCIC photometric comparison sequences used in current CCD observations. This data harvest has permitted the discovery of past undetected outbursts and secular trends, or to derive previously unknown orbital periods and recurrence times, which are essential to constrain the nature of these capricious and variegated active binaries.

Effects of variation in working fluids and operating conditions on the performance of a thermoacoustic refrigerator

This study reports on a numerical investigation of the effects of variation in working fluids and operating conditions on the performance of a thermoacoustic refrigerator. The performance of a thermoacoustic refrigerator is evaluated based on the cooling power, coefficient of performance (COP), and the entropy generation rate within the device. The effect of the variation of the working fluid is observed by changing the Prandtl number (Pr) between 0.7 and 0.28. The operating conditions investigated are drive ratio (DR), stack plate spacing (y0), and mean pressure (pm). The present research shows that lowering the Pr of the working fluid does not improve the performance of a thermoacoustic refrigerator for all of the selected operating conditions. COP increases 78% by reducing the Pr from 0.7 to 0.28 at y0=3.33δk, at atmospheric pressure and a DR of 1.7%. While the COP decreases by reducing the Pr from 0.7 to 0.28 at y0=1.0δk, at atmospheric pressure, and a DR of 1.7%. The results are compared with the available experimental data and found good agreement.

Determination of the energy of a relativistic electron beam by measuring the thickness of the colored layer in glass

A method for determining the energy of relativistic electrons, which was used in the investigation of electromagnetic fields in plasma and dielectric structures, is described. The electron energy was determined by the extrapolated track of electrons in glass, which was estimated by the thickness of the colored (darkened) layer formed by electrons. The density distribution of the colored layer along the direction of electron motion makes it possible to record the width of the beam energy spectrum and the beam position relative to the axis of the transit channel. A stack of glass plates on which the beam is incident can be installed in the transit channel of the dielectric structure or in plasma. Each plate in the stack is placed in parallel to the beam axis. After irradiation of the plates with relativistic electrons, the colored layer depth and the density distribution are determined. Examples of determining the electron energy of a pulsed relativistic electron beam are presented. The method is insensitive to electromagnetic noise, is inexpensive, simple, and easy to use.

The effect of injection molding PMMA microfluidic chips thickness uniformity on the thermal bonding ratio of chips

Injection molding PMMA microfluidic chips can significantly improve the efficiency of chips forming. However, due to the coexistence of macro and micro effects in the injection molding process, the thickness uniformity of molding substrates is poor, which will seriously affect the thermal bonding quality of chips. In this paper, the effect of injection molding PMMA microfluidic chips thickness uniformity on the thermal bonding ratio and the quality of micro-channels was studied by experiments and simulations. The results show that when the following three conditions were satisfied during injection molding process, chips bonding ratio reaches to 93.9 % and the distortions of micro-channels caused by thermal bonding were acceptable. Firstly, the cover plates flatness error is smaller than 50–60 μm and substrates flatness error is smaller than 80–90 μm. Secondly, the maximum thickness difference of stack chips (cover plate stack with substrate) is smaller than 70–80 μm. Thirdly, chips thickness of the middle is larger than that of the two ends along their length direction and chips thickness distribute evenly along their width direction. These conclusions can be used for the parameters selection and moulds design during injection molding process of PMMA microfluidic chips.

A nonlinear, data-driven model applied in the design process of disc-spring valve systems used in hydraulic dampers

This paper proposes an analytical tool that supports the design process of a disc-spring valve system used in hydraulic dampers. Such a valve is representative of a broader family of valve systems used in many industrial applications. The tool will speed up the valve-system design process. The paper considers a valve system that combines a number of circular metal plates, referred to further in the paper as ‘a stack of plates’. The proposed analytical tool obtains a key design characteristic of a valve, the flow rate, and the corresponding maximum stress level in the stack of plates as a function of pressure load. The stress level enables the ranking of valve settings in terms of durability. The calculation process is based on the response of a nonlinear, data-driven model that approximates the a priori simulated cases to cover the complete range of input design parameters, namely the number of plates, their thickness and their diameter. The cases are produced by a first-principle model using a Finite Element (FE) approach. The model was calibrated based on experimental results to provide accurate results in the entire range of input parameters. The advantage of the analytical tool is its ability to immediately provide the pressure-stress-flow characteristic of a valve instead of repeating time-consuming calculations for each new setting of input parameters. The objectives of the paper are as follows: to (a) adapt the model to a three-plate stack by applying large strain theory, (b) select and rank the Artificial Neural Networks used in order to approximate simulation data, and (c) demonstrate validation and application results obtained with the Approximation Tool.

Acoustic field measurements in a standing wave thermoacoustic refrigerator using time-resolved particle image velocimetry

A standing-wave thermoacoustic refrigerator consists of a stack of plates placed in an acoustic resonator. Two heat exchangers are located at each stack extremity. The thermoacoustic effect takes place in the thermal and viscous boundary layers along each plate of the stack. It results in a heat transport along the plates and in a temperature difference between the two stack ends. In such devices, the full understanding of the heat transfer between the stack and the heat exchangers is a key issue to improve the global efficiency of these devices. The aim of this work is to investigate the vortex structures, which appear at the ends of the stack and modify the heat transfer. Here, the aerodynamic in the gap stack-exchanger is characterized using a time-resolved particle image velocimetry technique. Measurements are performed in a device operating at a frequency of 200 Hz. Instantaneous velocity fields are recorded at a frequency of 3125 Hz (ie 15 maps per acoustic period). Measurements show that vortex shedding occur at high pressure levels, when a nonlinear acoustic regime prevails, leading to an additional heating generated by viscous dissipation in the gap and a loss of efficiency.