Porous Block Research Articles

Solvent-free carbon self-deposition of non-polymeric resin-based precursor toward N-doped porous carbon

Design and engineering of low-cost and high-efficiency functional carbonaceous electrode materials for supercapacitor has attracted increasing interest in energy storage. Herein, N-doped porous carbon block (N-PCB) was prepared via self-deposition of pyrolysis gas derived from directly degradation of typical resin monomer 3-aminophenol (AP) under the assistance of ZSM-5. In this monomer self-deposition approach, the rich pore channels of ZSM-5 promote the capture and deposition of pyrolysis gas from AP on ZSM-5 and the acidic surface of ZSM-5 catalyzes the pyrolysis gas conversion to carbon. This method realizes conversion of AP to porous carbonaceous material simply by grinding of AP and ZSM-5 mixture followed by routine pyrolysis treatment, without utilization of solvent and polymerization of resin, which simplifies the operation process and enhances the environmental friendliness. The prepared N-PCB replicates the bulk morphology of ZSM-5 and has a high specific surface area and a certain of nitrogen content, which provides favorable conditions for improving electrochemical performance.

Linear water wave interaction with a composite porous structure in a two-layer fluid flowing over a step-like sea-bed

ABSTRACT The present work is concerned with the interaction of oblique surface gravity waves by a simple and composite porous block of finite width placed on a multi-step bottom in a two-layer fluid. The ocean depth is taken to be finite and its bed impermeable. The problem is studied by employing linearised water wave theory and eigenfunction expansion. The dispersion relations and their roots are analysed which give a clear understanding of the phenomenon. The cases of simple and composite interface-piercing structures are taken up separately to investigate the impact of porosity in wave attenuation for surface and interface modes. Waves propagate through the porous structure with distinct eigenvalues. The appropriateness of structures of various configurations on the scattering of surface waves is investigated by examining the reflection coefficients for waves in surface and interface modes as well as their effects on the free surface and interface elevations, the wave-loads on the structure and the rigid wall supporting the structure at one end. Further, as a special case, the sea-bed preceding the step bottom is considered to be porous and its effect on reflection is examined. The investigation establishes that for a suitable configuration of the porous structure, an optimum width can be ascertained to design a breakwater of reasonable efficiency possessing characteristics of both reflection and dissipation processes. The problems are solved analytically and the results are presented in graphical form. This kind of study is likely to have immense significance for designing of different types of coastal structures with respect to reflection and dissipation of wave energy at continental shelves which is influenced by a stratified fluid, which is modelled in this work as a two-layer fluid for convenience. Comparison of present results with available results show good agreement and this points towards the effectiveness of the model described in this work.

Fabrication and Histological Evaluation of a Fully Interconnected Porous CO3Ap Block Formed by Hydrate Expansion of CaO Granules.

Carbonate apatite (CO3Ap) fabricated by a dissolution-precipitation reaction from a precursor exhibits excellent osteoconductivity and is readily replaced by bone. In the present study, a fully interconnected porous CO3Ap block was fabricated by hydrate expansion and carbonation of CaO granules, and the resulting CaCO3 was then converted to CO3Ap. When CaO granules were exposed to 100% humidity CO2 in a closed vessel, the CaO granules were hydrated and expanded to form a porous Ca(OH)2 block. The block was then carbonated to form a porous CaCO3 block, which was then immersed in a Na2HPO4 solution to convert it to a porous CO3Ap block. The resulting CO3Ap block possessed a fully interconnected porous structure. Histological analyses 4 and 8 weeks after implantation in rabbits revealed that the porous CO3Ap block resulted in more significant material resorption and bone formation than the dense CO3Ap block. Therefore, it was concluded that a fully interconnected porous CO3Ap block fabricated by the hydrate expansion of CaO granules has potential value as a bone substitute.

Three-in-one to enhance visible-light driven photocatalytic activity of BiOCl: Synergistic effect of mesocrystalline stacking superstructure, porous nanosheet and oxygen vacancy

Simultaneously integrating mesocrystalline stacking superstructures, porous nanosheets and defective oxygen vacancies (OVs) into BiOCl crystals is an available strategy to enhance the visible-light-driven photocatalytic activity. Herein, we report a facile etching agent-assisted hydrothermal approach to achieve one-pot fabrication of mesocrystalline BiOCl porous nanosheet stacking superstructures with defective OVs, which show high catalytic activities towards to the visible-light-driven degradation of organic dyes. The formation of stacking superstructure in a mesocrystalline BiOCl is responsibility for increasing the transport of charge carriers. Experimental results and theoretical calculations suggest that the presence of OVs is beneficial to tuning the energy band structure for the improvement of visible light harvesting, prolonging the lifetime and enhancing the oxidation activity of photogenerated charge carriers. Additionally, the porous morphology and thin nanosheet building block could supply abundant active sites for photocatalysis. This research might arouse in-depth investigations on the development of novel precursor-modified strategy for the synthesis of high-active BiOX (X = Cl, Br and I)-based photocatalysts.

Flow control and heat transfer enhancement inside a two-dimensional channel using porous blocks and applying bleeding condition between them

There are different methods to enhance forced convective heat transfer. In the current study, porous blocks are used on the hot wall of a two-dimensional channel. Use of porous media can enhance the heat transfer by improving the flow mixing with subsequent increment in the effective thermal conductivity of the domain at the position of the used permeable media. However, a cavity-like flow appears between the blocks, which deteriorates heat transfer there. In this study, a bleeding condition by suction is applied to improve heat transfer there. Effects of some important parameters including porous media permeability, porous blocks relative height, flow Reynolds number, and the bleeding coefficient on the thermal performance and pressure loss are investigated. The outcomes reveal that the bleeding condition effect on heat transfer mainly depends on the bleeding coefficient. For example, the effect of bleeding condition on the total average Nusselt number is negligible for the bleeding coefficient (σ) less than 0.01, while it could improve the average Nusselt number by 36% at σ = 0.05. Furthermore, increasing the permeability of porous blocks, the effect of the bleeding condition becomes more highlighted from the performance number point of view.

Hydromagnetic double diffusive moisture convection from an inclined enclosure inserted with multiple heat-generating electronic modules

This paper deals with thermosolutal convection in an inclined enclosure inserted with heat-generating porous blocks under the influence of magnetic field. The general Brinkman-extended Darcy model is adopted to formulate the fluid flow in the enclosure. An extensive series of numerical simulations is investigated in the range of parameters 0 ≤ Ha ≤ 150, 103 ≤ Ra ≤ 107, −10.0 ≤ N ≤ 10.0, 10−9 ≤ Da ≤ 10−1, 0.1 ≤ Kr ≤ 10 and −90° ≤ Φ ≤ 90°. Streamline, isotherms, isoconcentrations and masslines are produced to illustrate the fluid, heat and moisture flow structures. It is founded that overall Nusselt number is an increasing function of Ra, N, Da and Kr in the vertical enclosure, while decreasing with Ha. The permeability and thermal conductivity of porous blocks have no significant effect on moisture transfer rate. The Nusselt and Sherwood curves for different inclination angle are presented to be parabolic, and the maximum are near at Ф = −10° and 30°, respectively. In addition, correlations of the overall Nusselt and Sherwood numbers depending on thermal Rayleigh number, buoyancy ratio, Hartmann number and inclination angle have been obtained, which are beneficial to determine heat and moisture transfer rates in electrical devices.

Numerical study of non-Newtonian nano-fluid in a micro-channel with adding slip velocity and porous blocks

The investigation of microfluidics heat transfer in recent years has been of great interest to researchers. In studies to improve the thermal performance of micro-devices, the use of nano-fluids, geometric corrections and other parameters have been investigated. In addition to examining the heat transfer of cooling systems, the research of thermodynamics second-law of these systems has been widely studied in recent years. In this study, thermodynamics second law and heat transfer of non-Newtonian nano-fluid in a micro-channel with distributing variable temperature on the wall, the presence and absence of porous blocks and slip velocity with finite volume method (SIMPLE algorithm) have been investigated. Non-Newtonian nano-fluid contains water-CMC as the basis fluid and volume fraction of 3% and 4% nano-particles of TiO2. The current study is reviewed in two sections in the Reynolds number (10−100) and nano-particles volume fraction (3–4). In the first section, it investigates the influence of slip velocity and compares first and second-order models with different slip factor (0–0.1) on heat transfer, fluid flow, entropy generation and exergy losses. The outcomes present that the slip velocity of the first-order increases the mean Nusselt number in the range of 2.02% to 12.48%, and this range is 1.91% to 7.52% for second-order. Also, the first-order and second-order slip velocities reduce the generation rate of frictional entropy by a maximum of 76.2% and 67.43%, respectively. The rate generation of thermal entropy and exergy losses exhibits variable behaviour with Reynolds number. In the second section, the Darcy number (5 × 10−3–5 × 10−5), porosity (0.75–0.95) and thermal conductivity ratio (1–15) with first-order slip velocity are examined. The Nusselt number increases locally by reducing, reducing and enhancing the Darcy number, porosity and thermal conductivity ratio, respectively. The production rate of frictional entropy also increments by more than 800% with reducing Darcy number and porosity.

Hydrogenation of plant polyalkoxybenzene derivatives: convenient access to coenzyme Q0 analogues

A technologically advanced protocol has been developed for converting plant allyl(polyalkoxy)benzenes to methyl- and propyl(polyalkoxy)benzenes being intermediates in the syntheses of coenzyme Q0 analogues. The key stage of allyl and benzaldehyde moieties hydrogenation was carried out in a periodical autoclave mode on highly porous ceramic block Pd-catalysts. These catalysts possess large surface area, low hydraulic resistance, significant thermal and mechanical stabililty, multiple cycling and easy regeneration, which can dramatically reduce Pd consumption.

Experimental investigation of seepage characteristics in porous rocks with a single fracture

An experimental investigation of seepage characteristics in porous rocks with a single fracture is presented. A seepage system was developed and assembled in the laboratory using two experimental setups. Tests were conducted to quantify the effects of influent pattern, fracture aperture (B), coefficient of permeability of the porous medium (k), hydraulic gradient (J), and water temperature (T) on the seepage characteristics of a porous concrete matrix with a fracture; the porous concrete, with controlled characteristics, was designed to simulate porous rock. The mechanisms of seepage exchange between the porous media and the fracture are discussed, and a new formula for describing the seepage mechanism in a porous rock with a single fracture is proposed. The results showed that B, k, and influent pattern had significant effects on the seepage between the fracture and the porous concrete. The amount of effluent exiting the fracture was greater than that exiting the porous concrete blocks. The proposed model indicated that when B was less than 3.0 mm, the variation in fracture aperture had a significant influence on the effluent from the fracture, while its influence was relatively small when B was greater than 3.0 mm. When k was less than 1.0 cm/s and B increased to 4.8 mm, seepage exited only via the fracture. The proposed mathematical model can be used to effectively estimate the seepage through porous rocks with a fracture.

A comparative study on best configuration for heat enhancement using nanofluid

Abstract Nanofluid is a class of fluid which enhances the heat extraction from a hot surface. The concentration of nanoparticles enhances the conductivity of the fluid; however, it may change the fluid from Newtonian to a non-Newtonian. In addition, the type of base fluid plays a significant role in heat extraction. In this present study, three different configurations (porous block, porous straight channel and porous wavy channels) setups were investigated numerically using four different types of nanofluids mainly, 0.5% vol Al2O3/Water, 0.5% vol TiO2/Water, 0.5% vol Al2O3/Ethylene Glycol and 0.5% vol TiO2/Ethylene Glycol. Different parameters were assessed such as the local Nusselt number, the friction coefficient, the pressure drop, the temperature uniformity and the efficiency index. It was found that each nanofluid have a different performance for different configuration. If one relies on the efficiency index which combine the Nusselt number and the pressure drop, the nanofluid of 0.5% vol Al2O3 in water base provided the highest efficiency index.

A numerical analysis on the heat transfer of jet impingement with nanofluid on a concave surface covered with metal porous block

In this paper, combining the bilayer porous metal block of copper (BPMBC) on the concave heating surface and jet impingement of SiO2-H2O nanofluid is utilized in the flow channel. The k-e turbulent model coupled with Brinkman Forchheimer extended Darcy equations are employed to analyze the effects of the SiO2-H2O nanofluid concentration, porosity in the porous monolayer on concave surface, thickness ratio between the upper and lower porous layer in the bilayer porous metal block as well as the curvature of concave surface on the heat transfer. In comparison with pure water as working fluid, the 5.85% rise of average heat transfer coefficient (HTC) can be obtained while the 3.0% SiO2-H2O nanofluid is utilized in the mode. The combining effects of the porosity in the monolayer porous layer and the curvature of concave surface on the heat transfer are related to the heating surface area and convection between the jet nanofluid and heating surface. More heat transfer occurs in the bilayer porous metal block with a larger porosity in the upper layer and a lower porosity in the bottom layer due to the dominant effects of the convection and thermal conductivity respectively in the different porous layers. The effects of the thickness ratio between the upper and lower layer in the bilayer porous metal block on the heat transfer are related to the influencing portion between the surface area and convection. With an increase in the curvature of concave surface from R/L(ratio of concave radius to chordal length) =0.5 to R/L = 1.1, the average Nusselt numbers go up, and their rise rates decrease by the Reynolds number gradually, but the surface area decreases, which causes the average temperature rise of copper block. Besides, the higher average temperature occurs in the mode with a flat plate than that with a concave surface.

Solute Transport in the Element of Fractured Porous Medium with an Inhomogeneous Porous Block

In this paper, the problem of solute transport in a fractured-porous medium taking into account the non-equilibrium adsorption kinetic is studied. The solute transport in fractured-porous medium consisting of two fractures and a porous block between them located in a symmetric form is considered. The problem is then solved numerically by using the finite difference method. Based on the numerical results, the solute concentration and adsorption fields in the fractures and porous blocks are shown in graphical form. The effect of adsorption on the solute transport in a fractured-porous medium is then analyzed. In the case of different parameters in two zones, asymmetric distribution of the solute concentration and adsorption is obtained. The nonlinear kinetics of adsorption leads to an increase in the adsorption effects, conversely slowing down the rate of the distribution of concentration of the solute in the fluid.

ESTUDO EXPERIMENTAL DO DESEMPENHO DE PAVIMENTOS PERMEÁVEIS COMO ALTERNATIVA DE REDUÇÃO DO ESCOAMENTO SUPERFICIAL EM ÁREAS URBANAS

RESUMO: O processo de urbanização das cidades sem o adequado planejamento de uso do solo provoca uma crescente impermeabilização deste, levando a constantes cheias nos centros urbanos. Entende-se que os sistemas tradicionais de drenagem resolvem apenas parte do problema, pois não agem nas causas mas somente nos efeitos. Nesse sentido o presente trabalho tem como objetivo avaliar o desempenho do pavimento permeável em relação à capacidade de infiltração das águas pluviais, visando à redução do escoamento superficial em áreas urbanas; para isso foi realizada a simulação chuvas para obter o escoamento por meio da equação de precipitação de Palmas-TO, onde foi possível aferir parâmetros de infiltração e escoamento; também foram produzidos e ensaiados blocos em concreto poroso para avaliar sua capacidade de infiltração. Na simulação efetuada sobre o pavimento permeável em blocos intertravados observou-se que ocorreu uma absorção da precipitação nos 9 minutos iniciais; já na simulação realizada sobre os blocos vazados percebeu-se que neste praticamente não ocorreu escoamento superficial. Os blocos em concreto poroso demonstraram uma ótima capacidade de infiltração, conseguindo comportar em seu interior 7,2 litros, o que significa uma infiltração instantânea de 7,2mm de chuva.
 ABSTRACT: The process of urbanization of cities without the adequate planning of land use causes a growing waterproofing of this, leading to constant floods in urban centers. It is understood that traditional drainage systems solve only part of the problem, as they do not act on causes but only on the effects. In this sense, the present work aims to evaluate the performance of the permeable pavement in relation to the infiltration capacity of rainwater, aiming at reducing surface runoff in urban areas; for this, the simulation was performed rains to obtain the flow through the Palmas-TO precipitation equation, where it was possible to measure infiltration and flow parameters; blocks were also produced and tested in porous concrete to assess their ability to infiltrate. In the simulation carried out on the permeable pavement in interlocked blocks it was observed that precipitation was absorbed in the initial 9 minutes; already in the simulation carried out on the leaked blocks it was noticed that in this practically no surface runoff occurred. The porous concrete blocks demonstrated an excellent infiltration capacity, managing to accommodate 7.2 liters inside, which means an instant infiltration of 7.2mm of rain.

Fabrication of three-dimensional interconnected porous blocks composed of robust carbonate apatite frameworks

In scaffolds used for bone regeneration, osteogenic ability increases and mechanical strength decreases with increasing porosity. To ensure both mechanical strength and osteogenesis, an optimal pore architecture is necessary. Porous glass has high porosity and high mechanical strength, as it is framed with a rigid interconnected silica network and void interspaces in the silica network. In this context, based on the porous structure of glass, we fabricated porous blocks composed of carbonate apatite (CO3Ap), which is the major component of human bone mineral, with both high mechanical strength and high porosity. To fabricate the CO3Ap blocks, first, calcite-polymethyl methacrylate (PMMA) mixture granules were prepared. Next, the calcite-PMMA granules were allowed to join together in the mold by fusing PMMA, resulting in the formation of porous blocks composed of interconnected calcite-PMMA granules. Next, PMMA was thermally removed and the resultant interconnected calcite granules were partially sintered. Finally, the composition of the interconnected granules was converted from calcite to CO3Ap in a dissolution-precipitation reaction. Consequently, CO3Ap blocks with a continuous pore architecture were successfully fabricated. The porosity and diametral tensile strength were controllable within the range of 60‒70% and 1.0‒1.5 MPa, respectively, by filling the space between the calcite-PMMA granules. As these values are suitable for clinical use, the porous CO3Ap blocks have potential applications as scaffolds for bone regeneration.

Mixed convection enhancement by using optimized porous media and nanofluid in a cavity with two rotating cylinders

Mixed convection inside a square cavity with internal rotating heater and cooler is analyzed numerically by simultaneous application of porous media and nanofluid as a heat transfer enhancement technique. Optimized multi-block porous foams are utilized to enhance the heat transfer. This type of medium could improve the heat transfer rate with manipulation and selection of porous regions’ pore size (or permeability) by amplifying the flow in critical regions and weakening it in non-effective areas. The whole cavity domain is assumed to be made of 25 distinct porous blocks. At first, the effects of the various rotation directions have been investigated and then the optimum distribution of pore size in the porous media is determined in a manner to maximize the heat transfer rate using the pattern search optimization algorithm. Finally, simultaneous effects of application of multi-block porous media and nanoparticle addition to the base fluid on the average Nusselt number are studied in various conditions. For this purpose, various volume fractions of the nanoparticles are implemented to investigate the effects of the different values of the volume fraction on Nu number. The optimization has done for different Ri and Ra numbers for achieving to the best distribution in each condition. In the best condition, 20.4% increase in the heat transfer is obtained.

TiB2–ZrB2–SiC composite ceramic coating with the formation of solid-phase (TixZr1-x)B2 deposited by atmospheric plasma spraying as a barrier to molten cryolite-based salt

TiB2, ZrB2, and SiC powders with particles measuring several micrometers were first agglomerated and then deposited onto the substrate of a porous carbon block as a barrier to molten cryolite-based salt. Scanning electron microscopy, X-ray diffraction, and transmission electron microscopy were conducted to investigate the fine microstructure of the obtained ceramic coating and to elucidate the evolution of agglomerated powder from sprayed particles in plasma jet to splats on a substrate. Results indicated that a highly dense ceramic coating consisting of a solid solution (TixZr1-x)B2, residual TiB2, and ZrB2 was obtained. The compactness of the coating and the formation of a solid solution phase was mainly caused by a SiC-rich liquid phase, as determined from a boride and silicon carbide pseudodiagram. After being submerged in molten cryolite-based salt for 8 h, the ceramic coating was firmly bonded to a carbon block. No molten slat permeated the ceramic coating.

Effect of Aluminum Oxide on the Performance of Ionic Liquid-Based Aluminum–Air Battery

The aluminum–air (or oxygen) battery has received intense attention in the past because of its excellent benefits such as low cost and high energy density, but due to the challenging issues such as hydrogen evolution and inactive oxide film formation on the Al surface, it could not be fully applied. In this study, 1-Ethyl 3-Methyl Imidazolium Chloride ([EmIm]Cl) and aluminum chloride (AlCl3) are applied to resolve the aforementioned issues. Ex situ component-level and in situ cell-level open circuit voltage (OCV) tests combined with the physics-based model analyses were conducted to investigate the electrochemical reaction behaviors of the Al–air cell. Especially, the effect of aluminum oxide formation on the anode- and cathode-side reactions were analyzed in detail. The oxide film formed at the Al surface strongly was found to significantly impede the electrochemical reaction at the surface, and the film growth was controlled by decreasing the surface tension by aggressive anions. In the cathode side, the aluminum oxide precipitated in the porous cathode electrode was found to decrease the porous reaction area and block reactant access into the reaction sites. The effects of O2 solubility in the electrolyte, initial porosity and thickness of the porous electrode are compared in detailed, and optimal thickness is suggested.

Fabrication and Fireproofing Performance of the Coal Fly Ash-Metakaolin-Based Geopolymer Foams.

This paper aims to investigate the influence of coal fly ash (CFA) addition on the fireproof properties of the metakaolin-based geopolymer foams. The physical properties, thermal conductivity and fire resistance of the CFA-metakaolin-based geopolymer foams are discussed. The CFA-metakaolin-based geopolymer foams achieve a dry density between 259.43 kg/m3 and 349.73 kg/m3, a porosity between 71.78% and 72.98%, a thermal conductivity between 0.0871 W/(m·K) and 0.0944 W/(m·K) and a compressive strength between 0.38 MPa and 0.56 MPa, exhibiting better physical properties than that of the porous blocks without CFA addition. It is also found that the CFA addition could decrease the viscous sintering temperature and change the phase compositions of sintering products, resulting in the porous structure deterioration in a certain extent and obvious rise of the final reverse-side temperature during the fire-resistance tests. Fortunately, the conversion of the amorphous geopolymer gel to ceramics has helped to maintain the main skeleton structure stability. The CFA-metakaolin-based geopolymer foams still exhibit excellent fire resistance, and the reverse-side temperatures are always within 250 °C after 3 h fire-resistance tests.

3D pore-interconnected calcium phosphate bone blocks for bone tissue engineering

Pore size and connectivity of artificial bone scaffolds play key role in regulating cell ingrowth and vascularization during healing. The objective of this study was to develop a novel process for preparing 3D pore-interconnected open-cell bone substitutes with varying pore sizes. This was achieved by thermal-induced expansion, drying, then sintering the mixture of biphasic calcium phosphate (BCP) and a thermal responsive porogen comprising chitosan (CS) and hydroxypropyl methyl cellulose (HPMC). The interpolymer complexes (IPCs) of CS/HPMC were prepared and investigated by FT-IR. The mixtures of IPCs/BCP were heated up to 100 °C for analyzing their thermal expansion properties. This resulted in ~13% and ~42% volume increment for IPC-1/BCP and IPC-2/BCP, respectively, while ~230% volume increased in the case of IPC-3/BCP (therefore chosen for sintering bone blocks). Heating rate-dependent (0.20–0.25 °C/min range) sintering profiles for IPC-3/BCP were utilized to produce BCP bone blocks. Gasification of IPC during sintering resulted in the formation of interconnected porous structures, and the morphology was investigated by SEM, revealing varying sizes ranging from 106 ± 13 μm to 1123 ± 75 μm. The pore size range of bone blocks from 235 ± 46 μm to 459 ± 76 μm portrayed significantly high MC3T3-E1 cell viability with prominent filopodial extensions, and elongated cells, depicting efficient biocompatibility. Therefore, the process for preparing porous interconnected 3D bone blocks were feasible, thereby serving as an alternative for potential bone tissue engineering applications.

Numerical modeling and simulation of heat transfer and fluid flow in a two-dimensional sudden expansion model using porous insert behind that

A sudden expansion is a classical problem which is happened in different industries such as energy conversion, environmental control, and chemical processing. The current investigation is done to numerically analyze the fluid flow behavior and heat transfer over a sudden expansion when a porous medium is placed right after that. Effect of different parameters including Reynolds number (Re = 100, 200, 300), porous block height (D/H = 0.1, 0.2, 0.3, 0.4, 0.5), porous block length (L/H = 0.5, 1.0, 1.5, 2.0), and solid matrix–fluid thermal conductivity ratio (RK = 1, 10, 102, 103, and 104) on the heat transfer and pressure drop are examined. Results show that the average Nusselt number and performance number (the ratio of Nusselt number improvement to pressure drop increment) on the heated wall, located after the expansion, enhanced when Reynolds number rises (about 40% in Nusselt number at Re = 300). As well as, the results show that even low-permeable porous media could augment heat transfer at the expense of a little higher pressure drop (PN = 0.94 and about 16% better Nusselt number at L/H = 15, D/H = 0.5, Re = 300). The main achievement of this paper is that if the porous cover permeability is tuned, a good heat transfer enhancement could be achieved.