Porous Bed Research Articles

An approximate approach to estimation of dissociation rate of gas hydrate in porous rock bed

Development of deep shelf or onshore gas hydrate fields involves drilling wells with subsequent thermal, decompression or chemical action on the bed. In this case, the radius of thermal or decompression action is limited. As the field develops, recovery efficiency decreases, and necessity arises for drilling a new well that influences the cost of the technology. To determine the rational wells location, it is necessary to predict the advance of the phase transformation rate front into the depth of the bed. In this work, to study the movement dynamics of the gas hydrates dissociation front in a porous layer of rock, the Stefan problem solution is used. The method adequacy is substantiated by comparing the calculated results with known experimental data. The temperature fields are modelled in a porous bed during the methane hydrate dissociation. The temperature field dynamics for 200 days in a porous bed during the methane hydrate dissociation caused by thermal action is shown. The influence of porosity and excess temperature on the dissociation front movement rate is revealed.

STRATIFIED FLUID OF VARIABLE VISCOSITY PAST A POROUS BED UNDER THE ACTION OF PRESSURE GRADIENT.

Unsteady flow of viscous stratified liquid in a channel with the porous bed has been studied in this paper. To study the effects of the stratification factor and slip parameter on the flow. We divide the entire flow region into two zones, zone 1 relates to the region between the impermeable upper plate and the lower one being the porous bed where the flow is governed by Navier Stokes equations, zone 2 is the porous region where the flow is governed by the modified Darcy’s law. In this paper, we have studied the effects of the stratification factor(η) and porosity factor(σ) on the velocity profile of the flow generated by an oscillating pressure gradient. Here we have taken an oscillating pressure gradient and applied Lighthill’s technique for obtaining the velocity profile of the flow.

An Experimental Study on Burning Characteristics and Temperature Distribution of Inert Porous Sand Bed Soaked by Leaked Combustible Liquid

An Experimental Study on Burning Characteristics and Temperature Distribution of Inert Porous Sand Bed Soaked by Leaked Combustible Liquid

Simulator development of a rotary magnetocaloric refrigerator by stepwise regenerator modelling approach

Magnetic refrigeration has been seeing as a promising technology based on the magnetocaloric effect. One of its great advantages is it offers smaller global environmental impact relating to conventional refrigeration. Modeling and simulation of such processes can provide important data in the development and optimization of the experimental devices. Among existing designs, the rotary refrigerators presents several challenges in terms of complexity when comparing to reciprocating ones, which is compensated by several properties. A novel full process simulator of a magnetocaloric refrigerator processes was implemented to study the processes performance over different conditions. A stepwise modeling approach was applied, simplifying the phenomena of heat transfers. Gd was chosen as refrigerant material because of its magnetic transition temperature. The routine considered a rotating clockwise Gd wheel with an anticlockwise closed flow loop of water, which percolates the six Gd porous beds, hot and cold heat exchanger. The simulator was able to represent the transient aspects as well as the steady state conditions of the processes, considering both time performance and numerical stability. The inversion in heat transfer profiles along the process was used as a limit in the calculation of the maximum heat transfer absorption in the cold exchanger.

Experimental investigation of optimum charging and discharging time on packed bed heat regenerator for space heating and solar drying application

Solar energy has outstanding potential as a renewable source of energy. Presented work deals with building of such heat storage system which can store heat radiated from sun during the day and provide space heating at night by gradually discharging it for space heating and solar drying application. A parametric experimental study has been carried out on the bases of numerical based equations for dry clay material filled in packed reservoir which act as porous bed for absorbing heat under four different temperature i.e. 40 °C, 45 °C, 50 °C, 55 °C and 3 diverse mass flow rate i.e. 0.225 kg/m2-s, 0.335 kg/m2-s and 0.445 kg/m2-s. Based on results the optimum charging time at 40 °C, 45 °C temperature range with optimum mass flow rate 0.445 kg/m2-s has been achieved 48 min and 55 min and optimum discharging time at 40 °C, 45 °C temperature range with optimum mass flow rate 0.225 kg/m2-s has been achieved 125 min and 130 min for space heating application. The optimum charging time at 50 °C, 55 °C temperature range with optimum mass flow rate 0.445 kg/m2-s has been achieved 62 min and 68 min and optimum discharging time at 50 °C, 55 °C temperature with optimum mass flow rate 0.225 kg/m2-s has been achieved 135 min and 140 min for solar drying application with at least 3 packed bed having bed length of 1.6 m and diameter 0.1 m, which satisfy the requirement of 8 hrs continuous heat supply through packed bed heat reservoir during night time for space heating and solar drying application.

Numerical study of preheating primary air on pinewood and corn straw co-combustion in a fixed bed using Eulerian-Eulerian approach

The effect of preheating primary air on the co-combustion characteristics of a 50–50% blend of pinewood and corn straw in a fixed bed. The primary air temperatures were assessed from 20 to 130 °C. The co-combustion characteristics were included the co-combustion behaviors and emissions. In order to reveal the features of the combustion process in the porous bed, a two-dimensional unsteady state model was employed to investigate the combustion process in a fixed bed of blended biomass on the combustion process in a fixed bed reactor. Conservation equations of the bed were implemented to describe the combustion process. The gas phase turbulence was modeled using the k-ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. Results showed that by increasing primary air temperature the residual mass on bed decreased, while the average burning rates and ignition front propagation velocity increased At the primary air temperature of 85 °C the smallest unburned carbon was left in the ash, and the emissions of nitrogen-compounds were relatively small. In contrast, the primary air temperature of 85 °C was found to be well-operating condition, which can be suggested for industrial boiler during blend co-combustion. The simulation results were then compared with experimental data for different temperature, which shows that the combustion process in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data.

A magnetic wine cooler prototype

This work presents the design and performance evaluation of a novel magnetic refrigeration unit capable of controlling the temperature of a 31-bottle wine cooler cabinet. The main components of the system are: an active magnetic regenerator composed of eight porous beds of Gd/Gd-Y spheres, a two-pole magnetic circuit responsible for the magnetic field changes, a set of solenoid valves for flow control, and fan-supplied finned tube heat exchangers on the cold and hot sides of the wine cooler apparatus. Synchronization of the magnetic field variation and fluid flow processes was performed using real-time magnetic field measurements. The system was capable of reaching a mean temperature of 10.8 oC inside the retrofitted wine cooler cabinet by generating 27.9 W of cooling capacity for an ambient temperature of 25 oC. The coefficient of performance and second-law efficiency for this operating point were estimated as 0.21 and 1.0%, respectively. When operating at a cabinet temperature of 12.5 oC, the coefficient of performance and second-law efficiency achieved by the magnetic system were 0.38 and 1.6%.

Innovative large-scale photobioreactor for coal propelled power plant effluents treatment

This paper presents a phycoremediation technology application for effective wastewater treatment of two Israeli coal propelled power plants, one in Ashkelon (Rothenberg) and the second in Hadera (Orot Rabin). The technology is based on a new photobioreactor (PBR) at the heart of a biological integrative pollution prevention and control (Bio-IPPC) system. Unlike other known tubular and flat plate PBRs that are applicable in small Wastewater Treatment Plants (WWTP), this special PBR can be applied in large-scale domestic and industrial WWTPs. The unique PBR interior configuration, which includes multiple high porous polypropylene beds, enables the system to handle pollutants from both gaseous and aquatic effluents. Furthermore, while most existing algal-based technologies preserve cultured strains, this setup relies on WWTP habitat endemic flora. In the pilots of both power plants, the native biomass was single cyanobacteria Synechocystis salina, although the PBR photosynthetic composition can include multiple species of mixotrophic and/or autotrophic microorganisms. The results show that the photosynthetic biomass that grew on the PBR PP beds effectively assimilated the biomass nutrients such as nitrogen, phosphorous, magnesium, boron and calcium, and the toxic elements strontium and fluoride. Moreover, the system also mitigated greenhouse gas emission by the assimilation of bicarbonate (HCO3−) from the aquatic phase and CO2 from the gas phase.

Compound Boussinesq-type modelling over porous beds

In the present work a previously presented high-order Boussinesq-type model is extended to account for wave propagation over porous beds. The resulting wave solver is coupled with a sediment transport and morphological model to form a compound numerical tool for studying coastal hydrodynamics and morphodynamics. The linear properties of the derived equations are studied analytically with respect to wave celerity and spatial damping rate. The values of relevant parameters for the improvement of linear properties are also reviewed. The model is tailored for simulating wave propagation over permeable submerged breakwaters. The effect of the inclusion of dispersive terms in Darcy-Forchheimer equation on the propagation of both short and long waves over a permeable submerged breakwater is studied numerically. A qualitative investigation of the wave-induced current field and the resulting morphological evolution of a sandy beach is also presented.

3D CFD Modeling and Optimization of a Cylindrical Porous Bed Reactor for Hydrogen Production using Steam Reforming of Methane

Steam Reforming of Methane, which converts natural gas into products with higher economic value in the presence of a suitable catalyst bed reformer, is the most economical method for hydrogen production in petroleum refineries. This study focuses on developing a Computational Fluid Dynamics (CFD) model of a steam methane reformer. To this purpose, a steady-state heterogeneous 3 Dimensional model that was composed of mass, species, momentum, and energy balances was developed. It compares two different geometrical porous bed reformers with different heating tube configurations for better heat transfer and reforming. Effects of heating tubes inlet temperature, the ratio of inlet CH4/H2O, and the configuration of the heating tube are studied and optimized. The results show that conversion of methane will be promoted by increasing inlet temperature of the heating tube as well as the number of heating tubes in the reformer when CH4/H2O ratio is about 0.2. In this platform, the conversion of methane is not affected by the porosity below 0.35. Also, the simulations results are shown to be in agreement with typical data reported in the literature. So, this study can be used to develop industrial natural gas reformers.

Damping Characteristics of Solitary Wave Propagating over Sandy Bed in Shallow Water

To analyze the damping characteristics of solitary waves over a sandy bed, a numerical wave tank (NWT) with non-reflected wave generation system for solitary waves was used in this study. For the validity and effectiveness of NWT used, it was compared with the theoretical results to show damping phenomena of solitary wave passing over a porous bed. It is shown that the applied NWT in this study is applicable to the numerical analyses of a solitary wave propagation over a porous bed. Using the results obtained from NWT, the solitary wave amplitudes were reduced as the wave propagates over a sandy bed. And the solitary wave attenuations became more serious as the vorticity and turbulence kinetic energy were increased by the velocity difference around the face of a sandy bed. As well, the solitary wave attenuations became more serious with higher amplitude ratio to water depth when the solitary wave propagates over a sandy bed. In addition, the effects of effective wavelength on the damping of solitary waves over a sandy bed is discussed.

Statistics of particle diffusion subject to oscillatory flow in a porous bed

An experimental study was conducted of particle diffusion within a porous bed when exposed to oscillatory flow. The particle oscillates up and down within the porous bed in response to the oscillatory flow, but also becomes intermittently stuck for time intervals of varying duration. The combination of oscillating flow and random hindering of the particle motion by the porous bed leads to a diffusive process called oscillatory diffusion. A variety of statistical measures are used to characterize the particle diffusion under the oscillatory flow. These measures show that the experimental data exhibit characteristics of both classical diffusive processes as well as oscillatory processes. The particle hold-up time duration was found to be well fit by a log-normal distribution for all experimental cases examined. A simple stochastic model that captures the key features of the oscillatory diffusion process is shown to yield statistical measures that compare well with experimental data.

An Improved Configuration of Vertical-Flow Mesh Tube Filters for Seawater Pretreatment: Performance, Cleaning, and Energy Consumption

Roughing filters are types of porous media filter used in pretreatment systems where the raw water contains a large amount of suspended particles (SPs) and organic matter. Mesh tube filtration (MTF) media are roughing-filter media composed of low-density polyethylene used for SP removal during wastewater treatment. In this study, we present an improved MTF design—a porous filter bed (PFB), which exhibits superior SP removal performance compared to conventional MTF media. We then compare the applicability of MTF and PFB to both the primary pretreatment process for seawater desalination and the water reuse process. In bench-scale SP removal experiments, PFB shows removal rates of 46.7%, 68.0%, 67.6%, and 68.4% at hydraulic retention times of 15, 20, 30, and 60 min, respectively, which are better than those of MTF. The specific energy consumption (SEC) of batch dissolved air flotation (DAF) was known to range from 0.035 to 0.047 kWh/m3, whereas the SEC calculated for pilot-scale MTF and PFB is 0.027 kWh/m3 and minimum energy for influent supply, respectively. This suggests that PFB can compete with DAF as a primary pretreatment process. MTF predominantly removes SPs by sedimentation, whereas SP removal in PFB typically occurs via deposition of SPs on the mesh tube media.

Porous Bed Saturation Changes in Elution Process with Surfactant Solutions in Advanced Oil Recovery

AbstractThe elution of high‐viscosity substances from a granular bed using fluids with different interfacial tensions was investigated. Analyses of changes in flow resistance and the degree of saturation of the deposit during the process were conducted. The elution process was described by means of the modified concept of capillary bundles, based on the Blake‐Kozeny‐Carman relationship. The use of this dependence can be helpful in determining the degree of saturation of the deposit at any given time of elution process only on the basis of the flow hydrodynamics and parameters of the deposit and liquid. This makes it possible to estimate the residual saturation of the bed without the need to perform troublesome experimental research for the content of oil in the reservoir.

A facile and economical configuration for continuous generation and separation of oil in water emulsions

The development of a facile, compact, and inexpensive system for continuous liquid-liquid emulsification and separation, is a major engineering challenge in different industries such as petroleum, cosmetics, and food production. Herein, we report a simple and scalable design strategy for continuous generation and separation of the oil in water emulsions. The inexpensive, abundantly available sand was utilized for the fabrication of porous beds connected to process piping for continuous emulsion generation and separation. A mechanistic understanding of the governing parameters such as sand wettability, pore size, retention time, and energy dissipation are discussed in detail. Building on this understanding, we are able to generate stable oil in water emulsions with either nanoparticles or surfactants and achieve their complete demulsification by tuning the sand wettability, pore size, and retention time. We show the industrial applicability of the designed system by generation and separation of extremely viscous heavy crude oil in water emulsion, which would be suitable for pipeline transportation. Our results show the new way for the development of a modular and economical process unit at the industrial scale for liquid-liquid emulsification and separation.

Estudio de la movilidad de nanofluidos estables basados en hierro para remediación in situ de contaminantes inorgánicos

Las nanopartículas de hierro cerovalente (FeNPs) se han empleado para la remoción de una gran variedad de contaminantes en medio acuoso, transformándolos en especies de menor toxicidad mediante mecanismos de adsorción superficial y reacciones rédox. En tratamientos de remediación in situ de aguas subsuperficiales se inyectan como nanofluidos (NFs), donde las suspensiones de FeNPs deben estabilizarse para evitar su precipitación y favorecer su transporte. En este trabajo se prepararon nanofluidos estables a partir de FeNPs empleando estabilizantes como carboximetilcelulosa (CMC) o goma xántica (GX), y se evaluó su movilidad en columnas rellenas de lecho poroso, a escalas de laboratorio y piloto. Los parámetros del lecho se obtuvieron por modelado de las curvas de ruptura de un trazador de NaCl, empleando un software específico. Los NFs mostraron buena movilidad, mientras que las FeNPs sin estabilizar quedaron retenidas en el medio poroso. Con el objetivo de dilucidar completamente los mecanismos de transporte y los modelos de flujo actuantes se comenzó también con la caracterización reológica de los NFs, encontrándose resultados iniciales interesantes. Mediante una combinación adecuada de los experimentos de movilidad en columna, el modelado y la caracterización, se encontraron resultados alentadores que ayudarán a diseñar un sistema de inyección in situ de los NFs.

The effects of air gaps and inert layers on exploding bridgewire detonator function

ABSTRACT Exploding bridgewire (EBW) detonators work by electrically exploding a thin conducting wire as a result of a high voltage discharge from a capacitor. The process creates a strong UV (ultraviolet) emission and a shock compaction wave into the surrounding porous explosive bed. To investigate the significance of each, the research presented here utilized air gaps, an optical window, or inert porous powders between the bridge and explosive powder bed. The thickness of the air gap was varied to attenuate the air shock but allow the transmission of UV light. The optical properties of the inert porous bed were varied to allow a similar shock compaction to occur, but with different intensities of UV light. Finally, a thin optical window was used that blocked the shock, but allowed transmission of the UV light. It is clearly shown that both UV light and shock compaction are important to the functioning of EBW detonators at practical energy levels although each is individually capable of resulting in detonation if sufficient pure energy of either form is applied.

Multiple Solutions for Slip Effects on Dissipative Magneto-Nanofluid Transport Phenomena in Porous Media: Stability Analysis

In the present paper, a numerical investigation of transport phenomena is considered in electrically-conducting nanofluid flow within a porous bed utilizing Buongiorno’s transport model and Runge-Kutta-Fehlberg fourth-fifth order method. Induced flow by non-isothermal stretching/shrinking sheet along with magnetic field impact, dissipation effect, and slip conditions at the surface are also included. The numerical results show the existence of two branches of the solution for a selected range of the governing parameters. The physical significance of both branches of solutions is ensured by performing a stability analysis in which a linearized eigenvalue problem is solved. The multiple regression analysis with the help of MATLAB LinearModel.fit package has also been conducted to estimate the dependence of the parameters on Nusselt number.

Resistance coefficient for large-scale roughness with seepage through porous bed

Resistance coefficient is an important parameter in estimating the energy loss for bed roughness in open channels. The Manning–Strickler (MS) formula has been used widely over the past decades. However, it is not suitable for calculating the resistance coefficient of large-scale roughness. The problem becomes more complex when penetration through roughness is considered. This paper proposed a new resistance coefficient formula for quantifying the flow resistance for large-scale bed roughness considering the seepage effect. A two-layer dynamic model was established for the turbulent flow over large-scale roughness. In this model, the flow was divided into two part: the free-flow layer and permeable layer. The resistance formula was derived based on the two-layer model that considered the roughness area and seepage effect through roughness elements. Two sets of large-scale roughness data, namely, gravel-bed data and experimental data of the tetrahedral permeable frames, were used to validate and calibrate the derived formula. For gravel, qualitative analysis was undertaken to estimate the reliability of formula. For tetrahedral permeable frames, the coefficient of determination and Nash-Sutcliffe model efficiency were used to evaluate the model performance, which showed the formula reliably simulated measured data. Results indicate that the formula can be applied to different kinds of large-scale bed roughness with seepage flow by adjusting the shape factor. This research could provide a theoretical basis for the application of large-scale roughness in river engineering and management.

Analysis of air flow resistance through a porous stone bed

The results of analysis of airflow resistance through a porous stone accumulator bed are presented with studies conducted in laboratory and in a full-scale facility. The Darcy–Weisbach equation and Ergun's equation were used to determine the flow resistance coefficients. It was found that a simplification of the Ergun's equation by omitting the viscosity term did not result in a significant error in estimating the flow resistance. Dimensional analysis was applied to analyse the flow resistance in the full-scale facility and to determine the form and parameters of equation allowing a calculation of airflow resistance as a function of independent variables. The analysis showed a significant convergence between the friction factors and flow resistance calculated with the use of proposed equations and the values obtained from measurements. It is concluded that the following factors have the largest impact on the airflow resistance in order: bed particle diameter, followed by airflow velocity, effective section diameter and, to the same degree, layer height and bed mass.