Glass Balls Research Articles

Using Dates Leaves Midribs to Prepare Hierarchical Structures Incorporating Porous Carbon and Zeolite A Composites for Cesium137Cs Ion Exchange

This study synthesized zeolite 4A, and hierarchical composite structure consisting of zeolite 4A- carbon were successfully prepared. Hydrothermal method was used to grow a layer of zeolite 4A over porous carbon surfaces to enhance mass transfer and increase surface area of zeolite. The products then were used to remove radioactive cesium137Cs from liquid wastewater. Iraqi dates leaves midribs (DM) were used as locally available agricultural waste to prepare low- cost porous carbon, using carbonization method in tubular furnace at 900C for two hours. Hierarchical porous structures including zeolite are prepared by mechanically activating the carbon surface via Ultrasonicating nanoparticles suspension of ground zeolite type 4A.For preparing nanoparticles suspension, commercial zeolite has been milled using 0.3-0.4 mm diameter glass balls as grinding media. Nanoparticles of zeolite 4A acting as seeding (nucleation centers) increase the crystallization of amorphous aluminosilica gel on modification carbon surface. The products of the syntheses zeolite 4A and the hierarchal composite materials (DMZ) were characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Nitrogen sorption (BET) and Energy dispersive X-ray spectrometer (EDX) to check the morphology, structure, surface area, and the chemical composition respectively. The products were used to treat radioactive wastewater contaminated with radioactive cesium 137Cs collected from destroyed building of the Radiochemistry Laboratories (RCL) in AL-Tuwaitha Nuclear Site. The activity concentration for the contamination water pre and after the treatment were measured using gamma spectroscopy system supplied with a high purity germanium detector (HPGe) with 60% relative efficiency. The results showed that the radioactivity concentration after the treatment process decreased significantly from 4800 Bq/L to 186 and Bq/L,121 Bq/L using 0.045 gm from synthesized zeolite 4A and DMZ respectively.

Hierarchical Structures Incorporating Carbon and Zeolite to Remove Radioactive Contamination

Synthesis, characterization and application of hierarchical zeolites are becoming a subject of an increasing interest among scientists and researchers. Hierarchical structures incorporating zeolites possess secondary porosity at meso- and macrolevel to overcome problem of mass transport, which occurs with using conventional zeolites.
 In this study, the porous carbon surface was prepared by carbonization of the locally available agricultural waste of the Iraqi Nut shell (NS) using a carbonization method in a tubular furnace at 900ËšC for two hours. Hierarchicalpours structures including zeolite were prepared by the mechanical activation of the carbon surface using ultrasonication with a nanoparticles suspension of ground commercial zeolite type 4A. Zeolite was milled using 0.3-0.4 mm diameter glass balls as grinding media to prepare nanoparticles seeding, which increases the crystallization of the amorphous aluminosilica gel on the modified carbon surface during the hydrothermal method. The Product of the syntheses of zeolite 4A and the hierarchal composite material were characterized using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Nitrogen-Adsorption /desorption isotherms (BET), Energy Dispersive Spectroscopy (EDX), and Thermo Gravimetric Analysis (TGA) to determine the structure, morphology, surface area, chemical composition, and percentage weight of zeolite on carbon, respectively. The products were applied to remove the radioactive hazardous cesium isotope Cs137 from the radioactive wastewater provided by the destroyed building of Radiochemistry laboratories (RCL) in AL-Tuwaitha Nuclear Site. Gamma spectroscopy system with high purity germanium detector (HPGe) was used to measure the activity concentration for the contamination water before and after the treatment. The results showed that the activity concentration decreased from 4800 Bq/L to 186Bq/L and 100Bq/L using pure zeolite 4A and NSZ.respectively. The results also showed that the composite materials could be used effectively to remove radioactive 137Cs from a real wastewater, with ease of separation and recovery from the solution compared with the pure zeolite 4A.

Productivity enhancement of traditional solar still by using sandbags of El Oued, Algeria

AbstractThis manuscript aims to study the experimental analysis of solar still with sandbags as energy storage materials. To achieve this idea, 25 bags filled with El Oued sand was fixed inside a square basin vertically and distributed regularly, this is called the modified solar still with sandbags (MSS‐SB). The sand used in this study is very effective than many store mediums considered within many previous works such as glass balls, sponges, phosphate, yellow sand, black sand, and black gravel. This fact is due to its components characterized by high thermal conductivity. By using the Fourier‐transform infrared spectroscopy, X‐ray diffraction, and X‐ray fluorescence, it has been confirmed that the chemical properties of El Oued sand are composed mainly by 97.6% quartz (SiO2) and 0.56% calcite (CaCO3) and very low concentrations of some other oxides. To obtain the influences of the sandbags utilized in this study, the performance of MSS‐SB and traditional solar still (TSS) was tested at the same climatic conditions of the southeast of Algeria throughout 24 hours. Experimental results revealed that the overall cumulative distillate yield of TSS reached 3.76 L/m2/d, while for utilization the sandbags for MSS‐SB increase the cumulative distillate yield to 5.06 L/m2/d, representing 34.57% improvement in cumulative distillate yield. Also, the daily efficiency of TSS 33.1%, while for utilization the sandbags for MSS‐SB increases the daily efficiency to 44.63%, representing 34.83% improvement in daily efficiency.

Magic on the glass balls: Growth of two-dimensional atomic crystals with tunable bandgap

Magic on the glass balls: Growth of two-dimensional atomic crystals with tunable bandgap

Who invented the glasses and when

Glasses, if to sort things out, are one of the most remarkable inventions of mankind, which has given millions of people the opportunity to perceive the world through vision. Prototype of the first glasses — they were the thinnest emerald plates enclosed in a bronze frame — was found in the tomb of Tutankhamun according to historical information. Ancient Greeks and Romans did not know the glasses unlike the ancient Egyptians and used pieces of rock crystal for reading, they preferred to use monocle prototypes, i.e., devices for one eye. Medieval monks also tried to use pieces of rock crystal or quartzite as lenses, which after some time they began to place in a frame. Arabs were the first to come up with a glass ball as an optical device. It is believed that glasses for the protection against the sun and sun glare were invented even earlier than glasses for vision correction. It is noteworthy that this invention belongs not to the southern, but to the northern peoples –inhabitants of Greenland were the first to come up with the use of bone plates with narrow slots that protected eyes from the snow shining in the bright sun.

Thermal and hydrodynamic behavior of suspensions comprising nano-encapsulated phase change materials in a porous enclosure

Nano-encapsulated phase change materials (NEPCMs) are known to enhance the thermal characteristics of fluids; therefore, there is a rising interest in employing these materials in future thermal control systems. This paper investigates hydrodynamic and thermal characteristics of nanofluids, NEPCMs mixed in the host liquid, in glass balls as a porous structure. The geometry is a two-dimensional porous square cavity in which the left boundary is hot, the right boundary is cold, and the horizontal ones are considered to be insulated. The NEPCMs are composed of polyurethane (PU) as shell and nonadecane as a core. The impact of different non-dimensional parameters, such as Darcy number, 10−5 ≤ Da ≤ 10−1, porosity, 0.4 ≤ ɛ ≤ 0.9, Stefan number, 0.2 ≤ Ste ≤ 100, fusion temperature, 0 ≤ θf ≤ 1, and volume fraction of the NEPCMs, 0 ≤ ϕ ≤ 0.05, is studied on the flow and heat transfer characteristics. It is shown that the volume fraction of NEPCMs is directly proportional to the strengthening of the heat transfer rate in such a way that applying 5% volume fraction of NEPCMs could enhance the heat transfer up to 20.1% and 14.1% at θf = 0.5 in comparison to the cases of pure fluid and NEPCM mixture with no core-phase change, respectively. The effect of non-dimensional fusion temperature on the rate of heat transfer is also found to be noticeable. The maximum average Nusselt number emerges at θf = 0.5, which is the optimum fusion temperature.

G EXPERIMENTAL AND THEORETICAL STUDY OF FORCED CONVECTION AROUND A CYLINDER EMBEDDED IN POROUS MEDIA

An experimental and theoretical study of air forced convection heat transfer at Reynoldsnumber (1091.5 to 1560) around a circular cylinder placed in an iron test section (0.2x0.2x0.4m3) filled with saturated porous material glass balls of 5mm in diameter. A copper circularcylinder heater of diameter 0.015m and length 0.2m is heated electrically; it is located indifferent positions in X and Y direction within the test section. The forced convection heattransfer is simulated using the ANSYS program (Fluent). The results showed that the surfacetemperature distribution of the cylinder has the same trends for the different locations withinthe test section. The average Nusselt number increases with Reynolds number and heat flux.Also, the results show that the use of porous material improves heat transfer by 67.4%. Themaximum percentage deviation between the experimental and theoretical results is 1.622%.Moreover, experimental correlations were introduced and comparison was performedbetween the present results with the previous studies and it gives a good agreement.

Flexible, Conformable Organic Semiconductor Proximity Sensor Array for Electronic Skin

AbstractA flexible and conformal thin film proximity sensor array based on organic semiconductor dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (DNTT) is demonstrated, which can be perfectly affixed onto the curved objects such as glass ball, human brain model, and even the deforming human skin. Both spatial position and shape can be registered with fast response when human finger or insulator plastic to be recognized is approaching and removing. This flexible, conformal organic semiconductor sensor array bears merits of low operation voltage (1 V) and ultralow power consumption (0.36 nW), which is ideal for applications of the electronic skin in future wearable electronics.

Darcy–Boussinesq convective flow in a trapezoidal enclosure with thermal stratification

We explore numerically the Darcy–Boussinesq convective flow of water, kerosene, and engine oil through the glass ball, aluminum foam and sandstone porous medium inside a right-angle trapezoidal enclosure taking into consideration of thermal stratification. The bottom and left walls of the enclosure are uniformly heated, whereas thermal insulation is considered for the upper wall of it. Thermal stratification is applied to the right wall. The governing nondimensional partial differential equations are simulated using the Galerkin weighted residual finite element method with the help of COMSOL Multiphysics. We explored the time evolution of solutions and investigate the effects of the Rayleigh number, thermal stratification parameter, porosity parameter, types of the solid matrix and working fluids, and on the average Nusselt numbers, streamlines and isotherms. The simulated results confirm that the heat transfer rate amplifies with the increase in Rayleigh number and diminishes with the thermal stratification, porosity and aspect ratio of the enclosure. The results further guarantee that engine oil and aluminum foam perform better for heat transfer intensification. A two-cell flow is obtained for a stronger thermal stratification.

Indoor Air Quality and Passive E-cigarette Aerosol Exposures in Vape-Shops.

Direct emissions of nicotine and harmful chemicals from electronic cigarettes (e-cigarettes) have been intensively studied, but secondhand and thirdhand e-cigarette aerosol (THA) exposures in indoor environments are understudied. Indoor CO2, NO2, particulate matter (PM2.5), aldehydes, and airborne nicotine were measured in five vape-shops to assess secondhand exposures. Nicotine and tobacco-specific nitrosamines were measured on vape-shop surfaces and materials (glass, paper, clothing, rubber, and fur ball) placed in the vape-shops (14 days) to study thirdhand exposures. Airborne PM2.5, formaldehyde, acetaldehyde, and nicotine concentrations during shop opening hours were 21, 3.3, 4.0, and 3.8 times higher than the levels during shop closing hours, respectively. PM2.5 concentrations were correlated with the number of e-cigarette users present in vape-shops (ρ = 0.366-0.761, p < .001). Surface nicotine, 4-(N-methyl-N-nitrosamino)-4-(3-pyridyl)butanal (NNA), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were also detected at levels of 223.6 ± 313.2 µg/m2, 4.78 ± 11.8 ng/m2, and 44.8 ± 102.3 ng/m2, respectively. Substantial amounts of nicotine (up to 2073 µg/m2) deposited on the materials placed within the vape-shops, and NNA (up to 474.4 ng/m2) and NNK (up to 184.0 ng/m2) were also formed on these materials. The deposited nicotine concentrations were strongly correlated with the median number of active vapers present in a vape-shop per hour (ρ = 0.894-0.949, p = .04-.051). NNK levels on the material surfaces were significantly associated with surface nicotine levels (ρ=0.645, p = .037). Indoor vaping leads to secondhand and THA exposures. Thirdhand exposures induced by e-cigarette vaping are comparable or higher than that induced by cigarette smoking. Long-term studies in various microenvironments are needed to improve our understanding of secondhand and THA exposures. This study adds new convincing evidence that e-cigarette vaping can cause secondhand and THA exposures. Our findings can inform Occupational Safety and Health Administration, state authorities, and other government agencies regarding indoor air policies related to e-cigarette use, particularly in vape-shops. There is an urgent need to ensure that vape-shops maintain suitable ventilation systems and cleaning practices to protect customers, employees, and bystanders. Our study also demonstrates that nicotine can deposit or be adsorbed on baby's clothes and toys, and that tobacco-specific nitrosamines can form and retain on baby's clothes, highlighting children's exposure to environmental e-cigarette aerosol and THA at home is of a particular concern.

Free convection of a suspension containing nano-encapsulated phase change material in a porous cavity; local thermal non-equilibrium model

Due to the instinctive temperature-dependent heat capacity of the Nano-Encapsulated Phase Change Material (NEPCM), there is a growing interest in the potential applications of such materials in heat transfer. As such, steady-state natural convection in a porous enclosure saturated with nanofluid using NEPCMs has been investigated in this study. The cavity is assumed to have constant hot and cold temperatures at the left and right vertical boundaries, respectively, and fully insulated from the bottom and top walls. Considering the Local Thermal Non-equilibrium (LTNE) approach for the porous structure, the governing equations are first non-dimensionalized and then solved by employing the finite element Galerkin method. The impact of different parameters, such as porous thermal conductivity (ks), solid-fluid interface heat transfer (10 ≤ H ≤ 105), Stefan number (0.2 ≤ Ste ≤ 1), and volume fraction of nanoparticles (0.0 ≤ φ ≤ 0.05) on the patterns of the fluid and solid isotherms, streamlines and the contours of the heat capacity ratio, fusion temperature (0.05 ≤ θf ≤ 1), local and average Nusselt numbers, and overall heat transfer ratio has been studied. It is shown that improving the porous thermal conductivity not only leads to an increase in the rate of heat transfer but also augments the fluid flow inside the cavity. For low values of the Ste, the rate of heat, transferred in the porous enclosure, is intensified. However, regardless of the amount of the Stefan number, the maximum rate of heat transfer is achievable when the non-dimensional fusion temperature is approximately 0.5. Employing NEPCMs in a highly conductive porous structure is more efficacious only when the phases are in the state of local thermal equilibrium. Nonetheless, the rate of heat transfer is higher when the Local thermal non-equilibrium is validated between the phases. Besides, for poor thermal conductivity of the porous medium like glass balls (LTE condition), adding 5% of the nano-encapsulated phase change materials to pure water can boost the rate of heat transfer up to 47% (for Ste = 0.2 and θf = 0.5). This thermal investigation of NEPCMs shows in detail how advantageous are these nanoparticles in heat transfer and opens up an avenue for further application-based studies.

Tribological and mechanical properties of Cu/Ni-microdiamond bilayers on brass substrates coated by composite electrodeposition technology

Currently thin-plate glass used in portable devices is initially segmented by laser beam. The material melts and vaporizes during the process, which requires micro-tools for further edge milling. Due to the poor wear resistance and short life of the micro-milling tools and the fragile nature of the glass, the processing cost is high due to the low yield. In this study, a new alternative for preparing micron diamond milling tools was reported. Bilayers on brass substrates by a composite electrodeposition technique was prepared by using diamonds with a diameter of 2–4 μm. In order to improve the adhesion between the coating and the substrate, the electroplated pure copper was coated as the bottom layer, then the nickel and the diamond were compositely electrodeposited. The effects of current density, stirring speed, and diamond concentration in the electrolyte on the mechanical properties of the coating were investigated. The content and distribution of the incorporated diamond were analyzed by electron microscopy. It was found that, with the increase of current density, stirring speed, and the concentration of diamond in the electrolyte, the diamond content of the coating increased first and then decreased. When the parameters were: 200 rpm, 1.33 A dm−2, 10 g l−1, the content of the incorporated diamond in the coating became the densest and most uniform one, which enhanced the hardness and the wear resistance of the coating and reduced the roughness of the workpiece. The result of the wear test indicated that no coating composition was transferred to the glass ball, which meant the coating did not contaminate the glass material. The unique press-in mechanism protected the pull-off of the diamond and prolonged the tool’s service life. The rebounding mechanism of the coating was also feasible to the machining process of the glass, which could avoid the fragment of the thin glass. The use of the composite electrodeposition technique can remarkly reduce the manufacture cost of the micro-milling tool and, in the mean time, improve the machininng efficency and quality of hard and fragile materials.

Irreversibility analysis of thermally driven flow of a water-based suspension with dispersed nano-sized capsules of phase change material

A precise understanding of the thermal behaviour and entropy generation of a suspension comprising nano-encapsulated phase change materials (NEPCM) is important for the thermal energy storage and heat transfer enhancement in various engineering applications. Studies to date, have improved the knowledge of the heat transfer of NCPCM. However, a suspension comprising NEPCM in the porous medium could enhance the overall heat transfer performance. Therefore, this study aims to investigate the thermal, hydrodynamic and entropy generation behaviour of the NEPCM-suspensions in a porous medium. Conjugate natural convection heat transfer and entropy generation in a square cavity composed of a porous matrix (glass balls), occupied by a suspension comprising nano-encapsulated phase change materials, and two solid blocks is numerically investigated. Galerkin Finite Element Method is employed to solve the nonlinear coupled equations for the porous flow and heat transfer. The phase transition and the released/absorbed latent heat of the nano-capsules are attributed in a temperature-dependent heat capacity field. The thermal conductivity ratio (1 ≤ Rk ≤ 100), the Darcy number (10−5 ≤ Da ≤ 10−1), the Stefan number (0.2 ≤ Ste ≤ 1), the porosity of porous medium (0.2 ≤ ε ≤ 0.9), the dimensionless fusion temperature (0.05 ≤ Tfu ≤ 0.95), the solid walls thickness (ds = 0.1 and 0.3), and the volume fraction of the nano-capsules (0.0 ≤ φ ≤ 5%) are considered for the numerical calculations. The numerical results illustrate that the rates of heat transfer and the average Bejan number are maximum and the generated entropy is minimum when the fusion temperature of the nano-capsules is Tfu = 0.5. Besides, adding the nano-sized particles of encapsulated phase change materials to the host fluid increases the heat transfer rate up to 45% (for the studied set of parameters) and also augments the average Bejan number. The total entropy generation elevates with the increment of the volume fraction of the nanoparticles, for low values of the Darcy number; however, a downward trend can be found for higher values of the Da. The combination of NEPCM-suspensions (with latent heat thermal energy storage) and a porous medium (with the extended surface area) provides an extensive capability for thermal enhancement and energy storage applications. In this regard, the findings of the current work demonstrate that the selection of the fusion temperature and Darcy number are two essential key parameters, which could change the trend of the results.

Movement initiation of millimeter particles on a rotating rough surface: The role of adhesion

We performed experiments to determine the critical moment for movement initiation of a millimeter bead on a rotating rough surface. The corresponding critical angular velocities were measured for glass and stainless-steel ball bearings over two different rough surfaces with glued glass beads. A basic theoretical analysis was developed to explain the observed results. Although the expectation of a simple approach with the presence of the obstacles offered by a rough surface could be sufficient to describe the problem, we prove here that the sole consideration of these obstacles, and even friction, are insufficient to explain the results in the range of a few-millimeter glass particles. Where the thermodynamic work of adhesion between surfaces is significant, the adhesion forces must be considered in the force balance for particle detachment. This effect is a determinant for describing theoretically and numerically the dynamics of millimeter particles.

Visible and solar photodegradation of textile wastewater by multiple doped TiO2/Zn nanostructured thin films in fixed bed photoreactor mode

Azo dyes degradation in aqueous solution as an actual sample of textile wastewater was studied by the photocatalytic process using Zn, N and S, and Zn, N and S tri-doped TiO2 thin films. Thin films were synthesized by a sol-gel method, successfully. Spectroscopy and chemical oxygen demand techniques were used to assess the progress and efficiency of the reaction. UV–Vis results demonstrated that at natural pH 5.8 of the sample solution, maximum decomposition of 87–99% of azo dyes in 4 h has happened under visible irradiation with a primary concentration of 25 mg/l. According to COD results, after 4 h, a decreasing of the COD values from the azo dyes of solution significantly was obtained in the same condition. Besides, our results demonstrated, which nanostructure of TiO2/Zn-urea thin films with the highest efficiency decomposition, are recycled and permanent, showing a good potential of this technique in practical application. The immobilized TiO2 on the glass balls were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDS), diffuse reflectance spectroscopy (DRS), CHNS analysis and atomic absorption spectroscopy (AAS).

Experimental study on the coefficient of restitution of grain against block interfaces for natural and engineered materials

The coefficient of restitution (COR) is an important input parameter in the numerical simulation of granular flows, as it governs the travel distance, the lateral spreading, and the design of barriers. In this study, a new custom-built micromechanical impact loading apparatus is presented along with impact experiments on engineered and natural materials. The COR and energy loss of various grains and base block combinations are studied, including fairly regular-shaped Leighton Buzzard sand (LBS) grains as a natural soil and granite or rubber as base blocks, apart from the use of engineered materials for the grains (chrome steel balls, glass balls) and blocks (stainless steel, brass). The repeatability of the new micromechanical impact loading apparatus was checked by impacting chrome steel balls on stainless steel block. In all the test combinations, the higher and lower values of the COR are found for granite block (ranging between 0.75 and 0.95) and rubber block (ranging between 0.37 and 0.44) combinations, respectively. For the tested grain–block combinations, lower values of COR were observed for impacts between materials of low values of composite Young’s modulus. However, within the narrow range of composite surface roughness of the tested grain–block interfaces no particular trend was observed in the COR values. Compared to glass balls and chrome steel balls, greater scatter in the COR values is observed for natural sand grains. This is due to the variation of the elastic and morphological characteristics among individual LBS grains.

Numerical study on natural convection of Ag–MgO hybrid/water nanofluid inside a porous enclosure: A local thermal non-equilibrium model

This paper investigates the natural convection of Ag-MgO/water nanofluids within a porous enclosure using a Local Thermal Non-Equilibrium (LTNE) model. The Darcy model is applied to simulate the flow dynamics throughout the porous medium. Using non-dimensional parameters, the dimensionless form of the prevailing equations has been derived. Finally, the Galerkin finite element method is utilized to solve governing equations using a non-uniform structured grid, numerically. The key parameters of this study are Rayleigh number (10 ≤ Ra ≤ 1000), porosity (0.1 ≤ ε ≤ 0.9), nanoparticles volume fraction (0 ≤ φ ≤ 0.02), interface convective heat transfer coefficient (1 ≤ H ≤ 1000), and the thermal conductivity ratio of two porous phases (1 ≤ γ ≤ 10). It is indicated that dispersing Ag–MgO hybrid nanoparticles in the water strongly decreases the transport of heat through two phases of the porous enclosure. For glass ball and aluminum foam, by increasing the H from 1 to 1000, Qhnf would be 1.33 and 5.85 times, respectively, at φ = 2%.

Increasing the solar cell efficiency using glass balls

Solar cells lose high percent of their capacity as a result of insufficient solar radiation, due to changing of the solar angle of projection during the day. Thus this research aims to increase the cell efficiency by a novel method which is based on collecting rays in the convex focus and dispersed in the concave lens, to make the rays always perpendicular on cells. To achieve this purpose, glass balls with a diameter of 10 mm were used and arranged on the cell area. This work found an obvious increasing in the cell efficiency, where it is possible to have an increasing in generating voltage by an estimated 7.53%, and the current 1.086% by this novel method.

Effect of Multi Size Porous Media Properties on the Flow of Non-Darcy Regime

The objective of this paper is to study effect of multi size media on behavior of fluid at post-Darcy flow regime as porous medias differences in the sizes and weight. Crude oil used as fluid within three types of medias (gravels, glass balls, SiLibeads), and Kozeny –Carman model is used to estimate the head loss experimentally under changing on the flow rate. There are two coefficients have effect on non-Darcy flow regime (Reynolds number, Forchheimer number) at the same time depends it’s on properties of media; one of them is determined by using linear regression model to predicts the Forchheimer numbers. The permeability, porosity and Tortuosity are determined theoretically and all of them depend on properties of fluid and media. the test result shows the theoretical analysis from the Forchheimer number is directly proportional with effect of post-Darcy flow regime, and that non-Darcy behavior has good value with glass media (0.5166 porosity) .Porous media properties shows the permeability and non-Darcy coefficient have effect on non-Darcy behavior and inertia coefficient depends on porosity and properties of permeable bed.

Free Convection Heat Transfer Around a Cylinder Embedded in an Enclosure Filled with Porous Media

An experimental and theoretical study of free convection heat transfer for a cylinder placed in an iron test section of dimensions (0.2x0.2x0.2 m3), the test section filled with saturated porous material glass balls (5 mm), and the air is the working fluid with Raleigh number (7692.6 ≤ Ra ≤ 17654). The circular cylinder heater (D = 0.015 m, L = 0.2 m) is heated electrically, made of Copper and located in different positions (in X &amp; Y direction). The theoretical part includes solving the free convection heat transfer using the ANSYS program (fluent). The experimental and theoretical results showed that the surface temperature values around the cylinder perimeter when changing its position within the test section are changing as moving up and down where the effect of buoyancy force appears. The maximum difference between the upper and lower position at the experimental result is 7.22%, and the average Nusselt number increases with Raleigh number and heat flux. Also, the experimental results showed that the use of porous material significantly improves the heat transfer by 48.6%. The maximum percentage change between the experimental and theoretical results is 5.46%. Moreover, experimental correlations were achieved, and a comparison was performed between the present results with the previous studies and it gives a good agreement.