Parallel Plate Research Articles

Multi-channel current electro-optic isolated measurement and discharge current characteristics in a parallel plate transmission line driver

Multi-channel current electro-optic isolated measurement and discharge current characteristics in a parallel plate transmission line driver

Experimental investigation on slow thermal pyrolysis of real-world plastic wastes in a fixed bed reactor to obtain aromatic rich fuel grade liquid oil

Plastic wastes have become one of the biggest global environmental issues and thus recycling such massive quantities is targeted. Thermal pyrolysis has been the most suitable approach to convert the waste plastic into a source of energy. This study aims to compare the thermal pyrolysis of waste plastic with that of the modal plastic compounds in a fixed bed reactor. The liquid oil, obtained from the thermal pyrolysis of HDPE, LDPE, PP and PS wastes were characterized using FT-IR, GC-MS and 1H NMR. Also, their fuel properties such as viscosity and calorific values were characterized using parallel plate rheometer and bomb calorimeter respectively. C10–C44 paraffins and C10–C22 olefins were obtained along with aromatics and alcohols in different type of plastic waste pyrolysis oil. The viscosity of the plastic oil is within kerosene and diesel range. The calorific values of the oils are at par with the Petro fuels.

TIME DEPENDENT PRESSURE GRADIENT EFFECTS ON UNSTEADY MHD COUETTE FLOW THROUGH A PARALLEL POROUS PLATE

In this paper, the unsteady MHD Couette flow through a porous medium of a viscous incompressible fluid bounded by two parallel porous plates under the influence of thermal radiation and chemical reaction is investigated. A uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to time dependent pressure gradient. The transformed conservation equations are solved analytically subject to physically appropriate boundary conditions by using perturbation and Eigenfunction expansion techniques. The effects of some non-dimensional parameters are graphically represented and interpreted. It is observed that primary velocity is maximum when pressure gradient is time dependent as compared to when it is independent on time. Also, increase in temperature dependent pressure gradient leads to oscillation in primary velocity along distance y.

A new class of Finitely Extensible Nonlinear Elastic FENE-P model obtained with a thermodynamical approach and the use of compressible natural configurations. Part I: Isothermal deformations

In a recent contribution to the fundamental understanding of polymer fluid dynamics, Khambhampati and Rajagopal (2021) established a connection between the natural configuration theory of Rajagopal and Srinivasa (2000) and the FENE-P model of Bird et al. (1987 [6]). In this paper we capitalize on the result in Khambhampati and Rajagopal (2021) and present a new class of FENE-P models using a more general Helmholtz potential within the conceptual framework of evolving natural configurations. To show its qualitative behavior, we exemplify with a classical Couette flow between infinite parallel plates. The model is capable of reproducing key features experimentally observed such as stress relaxation and the overshoot of the shear stress at the beginning of typical shear stress growth experiments. Comparison against the FENE-P type model obtained in Khambhampati and Rajagopal (2021) is used for comparison.

Low-loss high-confinement terahertz guided-wave propagation along a subwavelength gap between double-dielectric-ridge-integrated gratings

Dielectric grating-based spoof surface plasmonic (SSP) structures are among the recent low-loss and subwavelength field-concentrating solutions for realizing high-density terahertz (THz) and sub-THz integrated circuits. In this paper, we report on a novel waveguide structure capable of supporting highly confined SSP mode while exhibiting much lower propagation loss compared to other similar SSP structures. The proposed structure is composed of two perfectly aligned identical silica ridges placed on the inner faces of the metallic plates of a parallel plate waveguide with a proper plate distancing in order to leave an empty gap region between the ridges. Each of the ridges embodies a periodic arrangement of high-resistivity silicon blocks with the same height as their own, although with smaller widths compared to their width. By performing modal analysis on the 2D and 3D structures of the proposed waveguide, its propagation properties are studied. It is observed that if the gap region is properly designed, a waveguiding structure with a subwavelength cross-sectional size around λ0/3×λ0/3, where λ0 is the free-space wavelength at the maximum frequency of operation, capable of providing a high degree of field confinement over a wide frequency bandwidth of nearly two octaves and with a very low propagation loss factor compared to similar SSP structures is achieved. Moreover, the performance of the proposed waveguide for implementing a 90° waveguide bend of the radius λ0/3, and for obtaining a spectroscopy-based refractive-index sensor is addressed. The results of our assessments suggest that the proposed waveguide can bring the state-of-the-art SSP designs yet another step closer to realizing ideal waveguiding structures for various applications in THz and sub-THz regimes.

Analysis of chemically reactive squeezing flow of silica and titania hybrid nanoparticles in water-based medium between two parallel plates with higher order slip

Considering the significance of hybrid nanofluid over convectional fluid in terms of high rate of heat transfer, nanoscience and nanotechnology has been enhanced by dispersing nanoparticles in the base fluid to obtain new material with series of properties and applications. In this study, the analysis of chemically reactive squeezing flow conveying silica and titanium dioxide nanoparticles in water-based medium across two parallel plates with higher order velocity slip is carried out employing three different chemical kinetics for exothermic/endothermic reactions. The system of partial differential equations resulting from the fluid model assumed the ordinary differential form in alliance with appropriate similarity variables. The modified ordinary differential equations is simulated numerically in MATLAB software package using fourth order Runge–Kutta integration scheme in line with shooting techniques. The tested validity for limited case conform to preceding reports in the literature. The outcomes from the scrutiny uncovered in tables and graphs revealed that the velocity and temperature distributions of the hybrid nanofluid decrease steadily as first order slip factor varies from 0.2 to 1.0 but increase with second order slip factor at all levels of chemical kinetics. Moreover, for exothermic reaction, the rate of heat transfer decreases at the lower plate by −221.923% with increasing value of activation energy parameter when m=−2,0,0.5 but converse is the case in endothermic reaction as the rate of heat transfer increases by 106.382%.

Modified calibration protocols in electron beam dosimetry: comparison with IAEA TRS-398 and AAPM TG-51

This study aimed to compare absolute calibration outputs based on the protocols of the International Atomic Energy Agency (IAEA) Technical Report Series (TRS)-398, the American Association of Physicists in Medicine (AAPM) Task Group (TG)-51, and modified calibration approach. The electron beam output calibration followed the IAEA TRS-398 and AAPM TG-51 protocols, both of which required cylindrical chambers and parallel plates. However, the use of cylindrical chambers is not recommended at low energies because of the large fluence-correction factor. TG-51 recommended cross-calibration of the parallel-plate chamber against the cylindrical chamber in a high-energy electron beam. In 2020, an electron beam dosimetry modification was introduced that used a cylindrical ionisation chamber at all energies and updated the data for beam quality conversion factors. This modification provided a lower deviation than that reported in AAPM TG-51. Thus, the modified calibration based on TRS-398 was applied in the present study, which yielded results below the permissible tolerance. The beam calibration at 6, 8, 10, 12, and 15 MeV energies was carried out for two Elekta linear accelerators.. Electron beam dosimetry followed the AAPM TG-51 and TRS-398 protocols, and modified calibration were performed to measure the dose at the maximum depth expressed in dose/monitor units (cGy/MU). Charge-reading measurements were measured using ionisation chambers PTW 30013, IBA CC13, and Exradin A11. The average absorbed dose ratios were 1.004 and 1.009 using the modified calibration and TRS-398 and modified calibration and TG-51, respectively. Therefore, based on IAEA TRS-398, the results were below the tolerance limit (±2%).

Effects of porous medium filling on thermally developing forced convection in a parallel plate channel

This study obtains the semi-analytical solutions and explores the thermal characteristics of a thermally developing flow in a parallel plate channel, partially filled with a porous medium at the core, while considering local thermal non-equilibrium conditions, and viscous dissipation for the first time. The developing temperature field, for a porous medium filling of volume fraction fixed at 0.9, indicates an increasing difference in temperature between the solid and fluid phases with the axial distance. Besides, heat flux bifurcation starts in the entrance region as more heat diffuses to the solid at the interface, more markedly with a decreasing Darcy number, Da. When the thermal transport is dominated by interstitial heat transfer between solid and fluid in the porous medium, the thermal entrant length is the shortest. An increasing amount of porous medium filling with such quality and an increasing Da tend to shorten the thermal entry length. Nonetheless, as a lower Da porous media convects more heat away from the interface, it expedites the thermal development in cases where interstitial heat transfer in porous medium is poor. With an increasing porous medium fraction, the impact of viscous dissipation on heat transfer magnifies at the entrance region, thereby reducing the effectiveness of porous medium insert.

Porosity and tortuosity: Keys for accurate modeling of porous electrodes in supercapacitors

Modeling of porous electrodes in supercapacitors (SCs) is rather important for both characterizing and improving the charging/discharging process of SCs, but the current models fail to balance accuracy, flexibility, and detail characterization of the electrode structure, especially the porosity and tortuosity. In this work, we develop a porous tortuous electrode (PTE) model consisting of a stack of multiple parallel plate capacitors with adjustable structural parameters for accurate modeling of SCs. By solving the equivalent circuit of the PTE model, the influence of the electrode structures on electric capacity and relaxation time are characterized with experimental validation, signifying the keys for accurate modeling of SCs as tortuosity and porosity and offering a general formula for describing the relaxation time of SCs. Based on the adjustable parameters in the PTE model, the spatial heterogeneity of the electrodes enables more intricate electrode structure designs. The PTE model facilitates various electrode designs and provides insight into the charging and discharging kinetics of porous electrodes.

Quality assurance of six cylindrical and two parallel plate chambers by radioactive check device: Influence of chamber age to its performance

PurposeTo evaluate the performances of eight ionization chambers, (two types) manufactured in a time span of 14 years, with radioactive source devices and photon beams. MethodsThe measurements were performed with six Farmer and two parallel plate ionization chambers with appropriate radioactive check devices and accompanying inserts. Some tests were performed with photon beams at linear accelerator. Physical visibility check, stability, linearity of response, directional dependence, determination of leakage current, ion recombination and polarity effect and influence of background radiation tests were conducted and analyzed. ResultsThe performance of all Farmer ionization chambers was in agreement to IEC standard as well as for parallel plate type chambers. Long-term stability of older planparallel chamber was somewhat worse than expected. ConclusionRadioactive check devices have proven to be easy to use in clinical environment. According to results of this work Farmer type ionization chambers showed good quality regardless of the time of production, which make them long-term suitable for clinical dosimetry in radiotherapy. Also, for parallel plate type of ionization chambers the results showed fine agreement with the IEC standard, except long-term stability for older chamber, which needs further investigation.

Convergence analysis of Lattice Boltzmann method for Stokes flow in digital rock characterization

The absolute permeability is a key parameter for characterization of reservoir rocks. It can be estimated numerically by combining digital rocks and Stokes flow simulation using Lattice Boltzmann Method (LBM). In previous research, the LBM is usually implemented as an iterative process, which continues until the changes in estimates of the parameters between two consecutive iterations reach below a certain threshold level. We remark that this termination criterion is not appropriate and may lead to low accuracy in the simulation results. Here we analyze the convergence of LBM in various tests including the Poiseuille flow between two parallel plates, and several types of digital rocks (dune sand, sandstone and carbonates). The logarithm of relative error of each estimate compared with the estimate at infinite time (as stable state) is found to have a linear relation with regard to the number of iterations, indicating an exponential rate of convergence. If the difference of errors between two consecutive iterations is used as the termination condition, the result could be far from a stable state. Instead, we recommend using the decay trend of the error difference in the LBM simulation to provide an accurate termination criterion, which serves as a practical and more adequate way for characterization of reservoir rocks. We also provided the theoretical explanation of convergence rate, which is related to the spectral radius of iterative matrix in linear algebra.

Toward Improved Correlations for Mixed Convection in the Downcomer of Molten Salt Reactors

Developing heat transfer correlations for buoyancy-driven flows and mixed convection is challenging, especially if the fluid’s Prandtl (Pr) number is not close to 1. For advanced nuclear reactor (Generation IV) designs, the downcomer plays a crucial role in normal operation and loss-of-power scenarios. The fluid-flow behavior in the downcomer can involve forced, mixed, or natural convection. Characterizing the heat transfer for these changing regimes is a serious challenge, especially in the heat transfer deterioration region. In this paper, the downcomer is simplified to heated parallel plates. The high–Pr number fluid FLiBe (a mixture of lithium fluoride and beryllium fluoride) is considered for all simulations. Direct numerical simulations using the graphics processing unit–based spectral element code NekRS are performed for a wide range of the Richardson number, from 0 to 400, at two different FLiBe Pr numbers (12 and 24). This results in an unprecedented 74 cases in total. Each case’s Nusselt number is calculated to evaluate existing heat transfer correlations. Moreover, we propose several new modifications for cases without satisfactory choice. As a result, several novel mixed-convection heat transfer correlations have been built for high–Pr number fluids. The correlations are expressed as a function of the buoyancy number, covering several mixed-convection regimes. The Pr number effect on the Nusselt number behavior is also analyzed in detail. We also propose a novel method to evaluate the heat transfer deterioration region. Modified Reynolds-Gnielinski forced-convection correlations are defined for the laminarization region, and a free-convection correlation is used for the natural-convection-dominated region. These correlations can describe well the trend in the heat transfer–deficient region.

Leakage Analysis of PEMFC Sealing System Considering Temperature Cycling

Addressing the leakage rate prediction problem of the PEMFC sealing system is of great importance for its stable operation. The leakage calculation method of the PEMFC sealing system is proposed based on thermal coupling. The parallel plate leakage model is improved to make it applicable to the leakage rate calculation with a variable channel cross-section height. The interface macroscopic contact pressure is solved using a finite element simulation for solid mechanics analysis. The Greenwood–Williamson model is used for contact mechanics analysis to solve for the average height of the leakage channel. The effects of the ambient temperature, compression ratio, bipolar plate misalignment, and gasket size on the cell sealing effect were studied numerically. The data indicated that as the ambient temperature, compression ratio, and gasket size became larger, the volume leakage rate began to be reduced. The leakage rate as a parameter to characterize the sealing performance, considering the influence of gasket size, operating conditions, and other factors on the cell sealing effect, is more meaningful for the durability study and failure analysis of PEMFC.

Heat and mass transfer analysis of nonmiscible couple stress fluid in a porous saturated channel

The present flow problem analyzes the impact of radiative heat and mass transfer with inclined magnetic field on thermal exchange and entropy production of two immiscible nature of electrically conducting couple stress fluid in a static porous saturated conduit. In this model, the lower and upper porous regions of the rectangular channel are occupied by two different types of couple stress fluids. The static horizontal parallel plates of the porous duct are completely isothermal and the flow of immiscible fluid through the porous duct develops because of a constant pressure gradient at the entry zone of the duct. The Brinkman model is utilized in the modeling of fluid flow through porous saturated domain and Rosseland’s approximation is utilized to compute the radiative thermal exchange effect on nonmiscible couple stress fluid. In this work, authors have analyzed the effect of various thermo-physical parameters such as the Hartmann number (Ha), permeability parameter (Da), Schmidt number (Sc), Soret number (Sr) and couple stress parameter ([Formula: see text]) on the entropy generation characteristics, Bejan number distribution, thermal behavior, concentration distribution and flow characteristics of immiscible couple stress fluid which passes through the porous channel. The parameters Ha, Da, [Formula: see text], Sc, Sr correspond to magnetic field effect, permeability of porous media, couple stress, mass diffusion and thermal diffusion, respectively. The most significant findings of this research work are as follows: • In a porous saturated channel, the immiscible couple stress fluid velocity, entropy production number and thermal profile get enhanced on increasing the couple stress parameter. • On increasing the Hartmann number and decreasing the permeability of porous region, the thermal properties and entropy production number both decrease. • The couple stress fluid’s concentration field and Bejan number distribution get decreased on enhancing Soret number Sr and Schmidt number Sc. • The entropy generation near the wall of the channel rapidly increases on increasing the Schmidt number and Soret number. The emerging finding of this research work exhibits excellent agreement with previously published work. This research work can be utilized in food processing, petroleum products and chemical process.

Propulsion due to thermal streaming

We demonstrate that the relative motion of horizontal parallel plates can be generated using patterned heating. This movement is driven by nonlinear thermal streaming associated with a pitchfork bifurcation. The propulsive effect is strongest when all the heating energy is concentrated in a single Fourier mode of the spatial heating pattern; it increases with a decrease in the Prandtl number and increases with the addition of a uniform heating component.

Advanced in vitro hemocompatibility assessment of biomaterials using a new flow incubation system

Physiologically relevant in vitro hemocompatibility assessment of biomaterials remains challenging. We present a new setup that enables standardized whole blood incubation of biomedical materials under flow. A blood volume of 2 mL is recirculated over test surfaces in a custom-made parallel plate incubation system to determine the activation of hemostasis and inflammation. Controlled physiological shear rates between 125 s−1 and 1250 s−1 and minimized contact to air are combined with a natural-like pumping process. A unique feature of this setup allows tracing adhesion of blood cells to test surfaces microscopically in situ. Validation testing was performed in comparison to previously applied whole blood incubation methodologies. Experiments with the newly developed setup showed that even small obstacles to blood flow activate blood (independent of materials-induced blood activation levels); that adhesion of blood cells to biomaterials equilibrates within 5 to 10 min; that high shear rates (1250 compared to 375 s−1) induce platelet activation; and that hemolysis, platelet factor 4 (PF4) release and platelet loss - but not thrombin formation – depend on shear rate (within the range investigated, 125 to 1250 s−1).

Analysis of mixed convection flow on Arrhenius-controlled heat generating/absorbing fluid in a super-hydrophobic microchannel: A semi-analytical approach

The theoretical analysis of steady mixed convection with Arrhenius-controlled heat flow for a viscous and an electrically-conducting fluid traveling across an isothermally heated vertical parallel plate in a slit micro-channel is investigated in this study. One wall had super-hydrophobic slip and a temperature spike, while the other did not. A semi-analytical technique (perturbation series) was employed to analyze the nonlinear and coupled leading equations. The results were carefully scrutinized, and the effects of the relevant and pertinent parameters were illustrated using various plots. It is concluded from this work that the actions of mixed convection and chemically reacting factors are noticed to substantially strengthen the fluid movement in the micro-channel for a constant pressure gradient. Additionally, the function of heat source parameter is depicted to raise the fluid flow while heat absorption parameter yields the reverse phenomenon. In the fields of engineering and medicine, it is essential to understand these fluids' characteristics. Owing to the lubrication of micro-channel boundary surfaces where conductivity and viscosity interact with thermos-physical behavior, the results of the present investigation can significantly enhance the functioning of micro-electro-mechanical systems (MEMS) and micro-devices relying on micro-fabrication processes.

The propulsive effect generated by fast travelling-wave vibrations

A prototype problem for the propulsion arising from a spatially-dependent source is analysed asymptotically. Such driving is a phenomenon that, while fairly common in biological settings, is less well understood in mechanical and engineering contexts. If two parallel plates bound a fluid and the plates are free to translate relative to each other, recent calculations have shown that vibrations applied to one plate in the form of travelling waves may induce motion of the other. The degree of the propulsion obtained is a function of both the wavelength and the phase speed of the imposed vibrations and there seems to an optimal wavelength for which propulsion is greatest. In order to shed light on these observations, here we undertake a formal asymptotic analysis of the process in the circumstance when the vibrations move quickly. It is shown how the flow structure takes on a form consisting of a bulk core layer supplemented by suitable edge layers attached to the two plates. The efficiency of the mechanism relies on the generation of a mean flow component whose properties are considered. It is found that there is excellent agreement between our analytical predictions and the previous simulations; in particular we are able to find the critical wavelength for maximum propulsion and explain the modifications that arise in the short and long wavelength limits.

Energy-efficient indirect evaporative cooler design framework: An experimental and numerical study

A remarkable surge in cooling demand is observed in the last decades. Currently, the cooling market is dominated by mechanical vapor compression chillers which are energy intensive and use harmful chemical refrigerants. Therefore, the current focus of the current research in cooling is the development of unconventional, sustainable cooling systems. In this regard, indirect evaporative coolers have shown significant potential (particularly under hot-dry climates) with high energy efficiency, low cost, water-based sustainable operation, and benign emissions. However, these systems are in the development stage and have not yet been fully commercialized because of certain design challenges. An innovative indirect evaporative cooler is proposed, fabricated, and experimentally tested in this study. Particularly, the study is focused on the development of heat transfer coefficient correlation for the system for commercial-scale design and expansion. This is because the earlier available correlation is based on simple airflow between parallel plates assumption and does not incorporate the effect of the evaporative potential of the system resulting in under/over-estimation of the heat transfer characteristics. The results showed that the proposed system achieved a temperature drop of 20 °C, a cooling capacity of around 180 W, and an overall heat transfer coefficient of up to 30 W/m2K. Moreover, the study presents an experiment-regression-based heat transfer coefficient correlation that satisfactorily captures the effect of outdoor air temperature and airflow rate ratio which are critical in the design of evaporative coolers. The proposed correlation showed a high (±5%) with experimental data thus making it suitable for the future design of IEC systems over assorted operating scenarios.

Research of the effect of different corrugated dust collection plates on particle removal in electrostatic precipitators

In this paper, a multi-physics field coupled model of electric, flow and particle fields was constructed by COMSOL to compare the effects of three different corrugated dust collector plates on electric field distribution, airflow field, particle trajectories and dust removal efficiency in an electrostatic precipitator, and to compare them with a conventional electrostatic precipitator with a parallel plate structure. The results indicated that the corrugated dust collection plate influenced the electric field within the ESP channel, while the wire plate spacing directly affected the size and distribution of space charge density. Furthermore, the corrugated dust collection plate also affected the EHD flow within the channel, with the D2-ESP and D3-ESP being the most strongly influenced by the ionic wind. By comparing the dust removal efficiency of the four ESPs, we found that D2-ESP has the highest dust removal efficiency, followed by D3-ESP, then Flat-ESP, and finally D1-ESP. The ranking order of the four ESPs' dust removal efficiency is consistent with the ranking order of the space charge density within the four ESP channels, which shows that the size of the space charge density directly affects the dust removal efficiency of ESPs. Numerical simulation results show that the change of wire plate spacing is the main reason why corrugated ESP affects the dust removal efficiency of electrostatic precipitators.