احمد نعمة مهدي الحصيني

Owing to its potential to limit the issues of intermittency and instability in solar energy by means of phase-change materials (PCMs), latent heat thermal energy storage (LHS) has met increasing attention and been widely employed in thermal-based systems. Most PCMs, however, inherently exhibit poor heat conductance leading to modest rate of charging. To master this drawback, highly conductive metal foams are utilized to upgrade the bulk heat conductance of a PCM resulting in an enhanced rate of heat transport; hence, accelerating the melting process. This enhancement way is employed to promote the response of a tube-bundle thermal energy storage unit configured of staggered tubes filled with high-porosity copper foam embedded in paraffin wax as a storage medium. To charge the thermal energy storage (TES) unit proposed, a relatively hot stream of water is allowed to flow across the bundled tubes through the voids in-between. To check how feasible the proposed design is, the tubes enclosing the TES medium and the water flow in the shell surrounding have been simulated by ANSYS Fluent CFD code. A variety of design factors has been examined to explore their influence on the charging performance attained including structural properties of the metal foam employed along with the configuration of the tube-bundle considered. The foam structural characteristics inspected are the porosity and pore density , while various tube-bundle configurations have been tested in terms of the packing density as well as the shape of PCM tubes used . Results indicate that for a certain tube-bundle configuration, the best response is acquired when denser foam with lower porosity is used, while the best performance can only be achieved with higher porosity due to the better TES capacity offered. For certain foam structural properties of , it has been observed that increasing the packing density can save up to 56 % of the time taken for charging completion with up to 200 % increase in storage capacity leading to up to 48 % improvement in the system overall performance. It has also been found that using paraffin embedded with copper foam as a TES medium accelerates the melting process considerably and saves more than half the time taken to charge the corresponding TES unit based on pure paraffin. It is also worth mentioning that the currently suggested LHS unit is not only of simple configuration, but practically efficient as well, with outstanding gross performance. Through a proper manipulation of design conditions, it has been found that the charging response can be notably improved leading to substantial promotion in the overall performance realized.

In remote areas, a scarcity of accessible water poses a significant predicament, and sun-powered propelling contraptions offer promising solutions. It is possible to collect solar energy with the goal of raising a fluid. Bubble pumps are used in the process of creating two-phase flows via the boiling of fluids in diffusion-absorption refrigeration cycles. In this investigation, a solar-powered bubble pump lifted the water. EES, which stands for engineering equation solver, was used in order to carry out the theoretical study of the bubble pump technology. Based on the results, it was determined that the void fraction displays a pattern that is comparable in applications using diffusion absorption refrigeration. In addition, the maximum water lift occurs at a certain heat flux value and any rise that is greater than this threshold causes the bubble pump to collapse entirely. Empirical tests were conducted utilizing bubble pumps with diameters of 8 mm and 10.21 mm to raise water across a distance of 4.53 m. The experiments examined a certain range of heat flow values at specified submergence ratios. According to the testing results, increasing the heat flux within the prescribed range significantly increased the 10.21 mm bubble pump's ability to lift water, yielding a maximum increase of 21%. According to the findings of the study, a universal set of optimal conditions and values for the bubble pump is not feasible to ascertain. This is because every system possesses distinct characteristics and operational elements that necessitate the utilization of optimized parameters for optimal performance.

In this paper, the elasto-hydrodynamic (EHD) performance of partial journal bearings has been studied. A numerical analysis has been conducted using the ANSYS Workbench (17.2) platform to investigate the performance of partial journal bearings. The lubricant used is considered Newtonian and incompressible fluid that flows steadily under laminar conditions, while the bearing material is assumed to be elastic, isotropic with smooth surface conditions. In the current FSI analysis, the lubricant flow has been predicted according to the finite_ volume method, while the finite element method has been adopted to compute the deformation and stress in the bearing surface. A wide range of operating and design conditions have been considered including the eccentricity ratio (0.1≤ε≤0.82), and arc bearing angle bearing (90ᵒ≤θ≤180ᵒ), while the values of bearing length to diameter ratio (L /D) and rotation speed (N) have been fixed at=0.77 and 1500r.p.m, respectively. The hydrodynamic pressure, performance characteristic of journal bearing, stress, and deformation have all been computed. It was found that the arc bearing angle and eccentricity ratio has a clear effect on the elasto-hydrodynamic properties of the partial bearings especially at high values of them.

In this paper, the elasto-hydrodynamic (EHD) performance of partial journal bearings has been studied. A numerical analysis has been conducted using the ANSYS Workbench (17.2) platform to investigate the performance of partial journal bearings. The lubricant used is considered Newtonian and incompressible fluid that flows steadily under laminar conditions, while the bearing material is assumed to be elastic, isotropic with smooth surface conditions. In the current FSI analysis, the lubricant flow has been predicted according to the finite_ volume method, while the finite element method has been adopted to compute the deformation and stress in the bearing surface. A wide range of operating and design conditions have been considered including the eccentricity ratio (0.1≤ε≤0.82), and arc bearing angle bearing (90ᵒ≤θ≤180ᵒ), while the values of bearing length to diameter ratio (L /D) and rotation speed (N) have been fixed at=0.77 and 1500r.p.m, respectively. The hydrodynamic pressure, performance characteristic of journal bearing, stress, and deformation have all been computed. It was found that the arc bearing angle and eccentricity ratio has a clear effect on the elasto-hydrodynamic properties of the partial bearings especially at high values of them.

In the current analysis, the effects of circumferential scratches along the inner surface of a 170ᵒ -arc partial journal bearing has been numerically investigated. Their impact on the thermo-elasto-hydrodynamic performance characteristics, including maximum pressure, temperature, deformation, and stress, has been examined thoroughly. The ANSYS Fluent CFD commercial code was employed to tackle the iterative solution of flow and heat transfer patterns in the fluid film domain. They are then applied to the ANSYS Static Structure solver to compute the deformation and stress resulted in the solid bearing zone. A wide range of operating conditions has been considered, including the eccentricity ratio ( ) and scratch depth ( ). In contrast, the bearing length-diameter ratio (L/D) and the rotation speed (N) have been fixed at 0.77 and 1500 rpm, respectively. The thermo-hydrodynamic pressure, temperature, stress, and deformation have all been computed. It was found that the scratch depth has a direct effect on the thermo-hydrodynamic performance of the partial bearings. Meanwhile, the deep central scratches are important, especially at scratch depth equal to 0.224 mm.

In the present research, highly-conductive graphite foams have been employed to effectively dissipate the heat generated in electronic components. The heat sinks suggested have been configured from staggered foamed-baffles arranged either in parallel or perpendicular to the air paths through the slots in between to reduce the pressure drop resulted while improving the heat dissipation. The performance of the currently proposed heat sinks has been examined numerically based on the volume averaging concept of porous media, with employing the local thermal non-equilibrium model to account for the interstitial heat exchange between the foam solid matrix and the fluid particles flowing across. The Simcenter STAR-CCM+ CFD commercial code has been utilised to implement the iterative solution based on the SIMPLE algorithm. A wide range of design parameters have been tested including the heat sink configuration along with geometrical characteristics of the graphite foam used. The impact of operating conditions, including the inlet airflow strength and the heat flux applied, has been inspected as well. The currently proposed heat sinks have been found efficient to meet the extremely thermal demands of high-performance electronic equipment and sweep away the heat generated there with a reasonable cost of pressure drop, where hot spots can be eliminated entirely with proper manipulation of design conditions.

In this paper, the effect of inserting a porous layer inside a wavy channel on the mean flow and turbulent characteristics in both developing and repeated flow regions have been investigated numerically. The modified Launder-Sharma low-Reynolds number turbulence model, which was used in a previous study [1] with two extensions model, has been utilised to represent the turbulence in the porous region. For validation, the flow in a clear channel with wavy bottom wall has been considered. The results of clear channel have been compared with the experimental data produced by [2], where the results computed were in a good agreement with the experimental data. In the porous wavy channel flow case, the same dimensions of the clear wavy channel have been adopted but with covering the bottom wavy wall with a porous layer formed of an open-cell metal foam. Three values for the wave amplitude of the wavy bottom wall and porous layer thickness have been considered, which are and , respectively. Three samples of metal foams have been tested along with the effect of the wave amplitude of the wavy surface and the thickness of the wavy porous layer on the turbulent flow. These types are , and . For all calculations, a Reynolds number equals to 20,600 has been considered. In the near fluid-porous interface region, damping functions have been used. The results show that the repeated flow pattern tends to occur in earlier region towards upstream than the flow over solid wavy surface when the permeability of the porous layer is decreased. Moreover, the repeated flow pattern also tends to occur in early region of the wavy part of the channel when the wave amplitude and porous layer thickness are increased, compared to the lower wave amplitude and low porous layer thickness. Decreasing the permeability increases the size of the recirculation cell in the repeated flow region and also increases the turbulent energy in the clear region. Increasing porous layer thickness, on the other hand, reduces the size of circulation cell and the turbulent energy.

Due to their unique heat transfer features, graphitic foams have been used in the current analysis to form heat sinks effective enough to dissipate extreme heat generated within high-performance electronics. The heat sinks suggested are formed from foamed-baffles arranged in-parallel or perpendicularly to the coolant paths via the staggered voids in between to alleviate the penalty of pressure drop while maintaining high heat dissipation capability. Dielectric liquid, developed for direct electronics cooling, has been utilised as a coolant to sweep away the too high heat density generated within high-performance electronics. The feasibility of the currently suggested thermal management technique has been numerically inspected following the volume-averaging approach of porous media considering a local thermal non-equilibrium to prevail between the solid foam and liquid coolant flowing through. Based on the SIMPLE algorithm, the iterative solution has been implemented using the STAR-CCM+ CFD commercial code for a wide range of operating and design conditions. The design parameters tested are the height of foam baffles and how they are orientated towards the mainstream besides the structural specifications of the graphitic foam employed, while the operating conditions examined are the coolant flowrate along with the heat density applied. It has been found that the heat sinks proposed is effective enough to fulfil the extreme thermal requirements in high performance electronics and capable to dissipate the heat generated there with affordable pressure losses, where proper selection of design parameters in light of the operating conditions applied can prevent the emergence of hot spots entirely.

Fluid-Structure Interaction (FSI), also known as engineering fluid mechanics, deals with mutual interaction between fluid and structural components. Fluid flow depending on the structural shape, motion, surface, and structural roughness, acts as mechanical forces on the structure. FSI can be seen everywhere in medicine, engineering, aerospace, the sciences, and even our daily life. This book provides the basic concept of fluid flow behavior in interaction with structures, which is crucial for almost all engineering disciplines. Along with the fundamental principles, the book covers a variety of FSI problems ranging from fundamentals of fluid mechanics to plasma physics, wind turbines and their turbulence, heat transfer, magnetohydrodynamics, and dam-reservoir systems.

As key elements in plenty of rotating machinery, the elastohydrodynamic performance of journal bearings should be carefully checked in light of the design and operating parameters considered. This first part of the current study aims to numerically analyse the operation of journal bearings under alignment conditions. In the fluid-solid interaction analysis conducted, the lubricant flow field is solved using the finite volume method. Based on finite elements strategy, a structural analysis is then implemented to the solid bearing using the pressure distribution computed earlier on its inner surface. A wide range of operating conditions has been considered including the eccentricity ratio (0.1≤ε≤0.9), bearing length-diameter ratio (0.8≤L/D≤2), and rotation speed (4,000≤N≤10,000 rpm). Three principal categories of operational quantities have inspected, namely; the lubricant pressure distribution, overall performance parameters, and structural aftereffects. Among all the parameters examined, the eccentricity ratio is the most influential one on the performance of journal bearings. As it increases with applying heavier loads, a significant rise occurs in each of the friction force, power loss, stress levels, and deformation on the inner surface of the bearing. The bearing length and rotation speed, on the other hand, affect the bearing performance as well, but to a less extent.

Due to its potentials to overcome the problems of instability and intermittency of energy through using phase change material (PCM), latent heat energy storage has been used in a variety of practical applications. However, most of the phase change materials possess poor thermal conductivity resulting in a modest charging/discharging rate. To overcome this deficit, high porosity metal foam is used to improve the overall thermal conductivity of the phase change materials leading to enhancing the heat transported, and hence, promoting the PCM melting and solidification. This proposal has been utilised to improve the performance of a thermal energy storage system formed of staggered bundled tubes, which are filled with paraffin wax as a PCM compounded to open-cell copper foam. The PCM unit is charged/discharged using a relatively hot/cold water stream flowing across the tube-bundle units. The feasibility of such a configuration is examined numerically through simulating the proposed PCM-metal foam composite units and their surrounding shell computationally using the ANSYS Fluent CFD commercial code. The impact of some design and operating parameters on the charging/discharging performance has been tested including the water flow strength as well as the tube-bundle configuration. The currently proposed design of LHTES system has been found not only easy to configure, but practically efficient as well, where the overall performance achieved is remarkably outstanding, i.e. OP=(104~105). Besides, the charging/discharging rate can be remarkably boosted through a wise selection of design parameters.

The primary focus of the present study is to investigate the impact of anti-vortex holes design on the film-cooling performance in a film-cooled rotor blade model using the large eddy simulation method (LES). One row of the film holes was positioned on the pressure surface of the rotor blade. This row had three cylindrical holes (the main hole in the present study) with a diameter (D) of 4 mm and a tangential injection angle of 28 deg. Each main hole supplemented with the addition of two symmetrical side holes (anti-vortex holes), which branch out from the same main hole. Three positions for the anti-vortex side holes were considered; namely: upstream to the outlet of the main hole; in line with the main hole; and downstream of the main hole. The Reynolds number was fixed at Re = 1.92 × 105 and the speed of the rotor blade was taken to be 1800 rpm. The blowing ratio varied from 1.0 to 5.0 and the density ratio of coolant to mainstream was 2.0. Compared to the base hole, the film cooling performance of the all anti-vortex cases showed obvious improvement at all blowing ratios. The middle stream side holes and downstream side holes each demonstrated good film cooling performance at all blowing ratios, while the upstream side holes perform well only at a lower blowing ratio. The presence of side holes can restrain the CRVP (counter rotating vortex pairs) intensity of the main hole and reduce the coolant lift-off, improving the film coverage and film cooling effectiveness. The downstream side holes can perform better in reducing the CRVP intensity.

In this paper, flow field and heat transfer performance in stationary and rotating wavy channels with different shapes were numerically investigated. Three different geometries were generated through three different values of phase-shift angles of ∅= 0, 90 and 180° between the two opposite wavy walls. A cell-centred finite-volume technique was employed to solve the three-dimensional governing equations based on the SIMPLE algorithm technique. Besides, the Menter SST turbulence model was used to simulate the turbulent flow in the current study. The wavelength and wave amplitude of the channel examined were Lw=20 mm and a = 2 mm, respectively. Numerical simulations were carried out over a range of design and operating conditions including the phase-shift angle of ∅= 0–180°, Reynolds number of Re=1,000–10,000, and rotating speed of Ω= 0–1000 rpm. The results showed that the surface-averaged Nusselt number increases as Re increases for all shapes of the wavy channel, however, at the expense of the raised pressure losses. Also, the wavy channel with a phase-shift of ∅= 0 deg showed the highest enhancement in the performance of heat transfer followed by that of ∅=90 and 180 deg, respectively. The rotation had a strong impact on the flow field and heat transfer performance. With the increase of rotating speed, lower wall heat transfer coefficient significantly increased, while the upper wall heat transfer coefficient exhibited a slight increase, indicating that those three different geometries of the wavy channels had a good versatility at various values of rotating speeds. The numerical results were compared with those available in the literature, and the results were in a good agreement.

This chapter is aimed as a concise review, but well-focused on the potentials of what is known as “High-porosity metal foams,” and hence, the practical applications where such promising media have been/can be employed successfully, particularly in the field of managing, recovering, dissipating, or enhancing heat transfer. Furthermore, an extensive comparison is conducted between the formulations presented so far for the geometrical and thermal characteristics concerning the heat and fluid flow in opencell metal foams.

A numerical analysis of the fluid flow and heat transport phenomenon through a rotary thermal regenerator is presented using a porous media approach. An aluminium core formed of multi packed passages is simulated as a porous medium of orthotropic porosity in order to allow the counter-flowing streams to flow in a way similar to that inside the regenerator core. Based on empirical equations, geometric properties of the core were transformed into the conventional porous media parameters such as the permeability and inertial coefficient; so, the core has been dealt with as a porous medium of known features. Heat is only allowed to transport within the rotating core, where a local thermal non-equilibrium situation is assumed there between the fluid and solid phases. The use of porous media approach has been found to be sufficient to solve the current problem. The results are presented by means of overall regenerator effectiveness, pressure drop, and the overall system performance. The impact of different design aspects were investigated such as the core geometrical characteristics, core dimensions, and operating conditions. The data obtained reveal an obvious impact of the parameters inspected on both the heat restored and the pressure loss; and hence, the overall efficiency of the regenerator system. Although regenerator effectiveness can be improved considerably by manipulating the design factors, care must be taken to avoid unjustified expenses resulted from potential augmentation in pressure drop.

In order to enhance the amount of heat transported in a double-pipe heat exchanger, a compound enhancement is proposed herein incorporating both active and passive methods. The first one is through introducing secondary flows in the vicinity of the conducting surface using metal foam guiding vanes, which are fixed obliquely and rotating coaxially to trap fluid particles while rotation and then force them to flow over the conducting surface. The other is via covering the conducting surface between the two pipes with a metal foam layer to improve the heat conductance across it. This proposal is examined numerically by studying the three-dimensional, steady, incompressible, and laminar convective fluid flow in a counter-flow double-pipe heat exchanger partially filled with high porosity metal foam and rotating in a coaxial-mode. In regards to the influence of rotation, both the centrifugal buoyancy and Coriolis forces are considered in the current study. The generalised model is used to mathematically simulate the momentum equations in the porous regions employing the Boussinesq approximation for the density variation. Moreover, thermal dispersion has been taken into account with considering that fluid and solid phases are in a local thermal non-equilibrium. Computations are performed for a range of design parameters influencing the performance achieved such as the operating conditions and the configuration of the guiding vanes utilised. The results are presented by means of the heat exchanger effectiveness, pressure drop, and the overall system performance. The current proposal has proved its potential to enhance the heat transported considerably with saving significant amount of the pumping power required compared to the corresponding heat exchangers, which are fully filled with metal foam. Also, the data obtained reveal an obvious impact of the design parameters inspected on both the heat exchanged and the pressure loss; and hence, the overall performance obtained. Although the heat exchanger effectiveness can be improved considerably by manipulating the design factors, care must be taken to avoid unjustified expenses resulted from potential augmentation in pressure drop.

The film-cooling performance in a low-speed rotor blade of a 1-1/2 turbine stage has been examined using LES approach. Two rows of film holes were positioned on the rotor blade surface, one on the pressure surface and the other one the suction surface, with axial locations of 24.2% and 22.6% of the chord length, respectively. Each row has three cylindrical film-cooling holes with a diameter (D) of 4 mm and a tangential injection angle of 28o on the pressure side and 36o on the suction side. The Reynolds number, based on the mainstream velocity of the turbine outlet and axial length of the turbine, was fixed at Re=1.92×105, the coolant-to-mainstream density ratio (DR) was about 2.0, and the speed of the rotor blade was taken to be 1800 rpm. Several blowing ratios (BR) in the range of 1.0–5.0 were investigated. The effects of blowing ratio, rotation, and curved surfaces were analysed to investigate the effects of the stator–rotor interaction on the film-cooling characteristics. The commercial CFD code STAR-CCM+ was used to run the simulations using the WALE subgrid-scale model for modelling the turbulence. The solutions were obtained by solving the incompressible, 3D Navier–Stokes equations under the rotating coordinates system with the energy equation, and the pressure–velocity coupling was achieved by using the well-known SIMPLE algorithm. The results show that on the pressure side, the film coverage and film-cooling effectiveness increase with increasing BR. A lower BR results in stronger film deflection. The film injection with higher BR produces better film attachment. The film deflects centripetally due to the effect of rotation. On the suction side, the trend of film coverage and film-cooling effectiveness is parabola as the blowing ratio rising and a centripetal deflection of the film is observed. The deflection of the film path could be amplified by decreasing the BR.

In order to enhance the amount of heat transported in a double-pipe heat exchanger, a compound enhancement is proposed incorporating both active and passive methods. The first one is through introducing secondary flows in the vicinity of the conducting surface using metal foam guiding vanes, which are fixed obliquely and rotating coaxially to trap fluid particles while rotation and then force them to flow over the conducting surface. The other is via covering the conducting surface between the two pipes with a metal foam layer to improve the heat conductance across it. This proposal is examined numerically by studying the three-dimensional, steady, incompressible, and laminar convective fluid flow in a counter-flow double-pipe heat exchanger partially filled with high porosity metal foam and rotating coaxially. With regards to the influence of rotation, both the centrifugal buoyancy and Coriolis forces are considered in the current study. The generalised model is used to mathematically simulate the momentum equations in the porous regions. Moreover, thermal dispersion has been taken into account while considering that fluid and solid phases are in a local thermal non-equilibrium. Computations are performed for a wide range of design parameters influencing the performance achieved such as the operating conditions, the configuration of the guiding vanes utilised, and the geometrical and thermal characteristics of the metal foam utilised. The results are presented by means of the heat exchanger effectiveness, pressure drop, and the overall system performance. The current proposed design has effectively proved its potential to enhance the heat transported considerably in view of the significant savings in the pumping power required compared to the heat exchangers fully filled with metal foams. Furthermore, the data obtained reveal an obvious impact of the design parameters inspected on both the heat exchanged and the pressure loss; and hence, the overall performance obtained. Although the heat exchanger effectiveness can be improved considerably by manipulating the design factors, care must be taken to avoid unnecessary expenses resulted from potential increases in pressure drop.

Rotating machineries operating at extreme temperature conditions usually need to be cooled internally by involving cooling passages inside them. A potential way to improve heat dissipated by these channels is by filling them with high porosity metal foams ε ≥ 0.89. This proposal is examined numerically by studying developing convective flow across a porous rectangular channel subjected to a uniform wall heat flux and rotating in a parallel mode. In regards to the influence of rotation, both centrifugal buoyancy and Coriolis forces are considered. The generalized model is used to mathematically simulate the momentum equations employing the Boussinesq approximation for the density variation. Moreover, thermal dispersion has been taken into account with considering that fluid and solid phases are in a local thermal non-equilibrium. Computations are performed for a wide range of dimensionless parameters including the aspect ratio, medium porosity, fiber size, rotation number, and solid- to fluid-phase thermal conductivity ratio, while the values of Reynolds and Prandtl numbers are maintained constant. The results reveal that both rotation and thermal dispersion have significant roles in enhancing heat transfer at high levels of porosity and low conductivity ratios. However, these roles are reduced gradually with decreasing the medium porosity or increasing thermal conductivity ratio, but do not completely vanish. In addition, overall performance is improved with either decreasing the aspect ratio for Ar < 1 or increasing it for Ar > 1. Eventually, the worth of using high porosity fibers in enhancing the heat transported through rotating channels has been inspected. An overall enhancement parameter was compared for the current study with a previous study regarding turbulent flow in a rotating clear channel, where it has been confirmed that the current proposal is practically justified and efficient.

The development of three-dimensional heat transfer and fluid flow in a square channel rotating in a parallel-mode has been investigated numerically. The duct is partially occupied by a foam material of high porosity ε ⩾ 0.89 and subjected to a uniform wall heat flux. In regards to the influence of rotation, both the centrifugal buoyancy and Coriolis forces are considered in the current study. The generalized model is used to mathematically simulate the momentum equations employing the Boussinesq approximation for the density variation. Moreover, thermal dispersion has been taken into account with considering that fluid and solid phases are in a local thermal non-equilibrium. The governing equations are discretized according to the finite volume method with employing a hybrid differencing scheme. Computations are performed for a wide range of parameters including the hollow ratio (0 ⩽ S ⩽ 1), foam porosity (0.89 ⩽ ε ⩽ 0.97), pore density (5PPI ⩽ ω ⩽ 40PPI), solid to fluid thermal conductivity ratio (250 ⩽ κ ⩽ 4000), Reynolds number (250 ⩽ Re ⩽ 2000), and rotation number (0 ⩽ Ro ⩽ 1), while the values of characteristic temperature difference and Prandtl numbers are maintained constant at ΔTc = 1000 °C and Pr = 0.7, respectively. Results reveal that flow resistance and heat transport are augmented with either decreasing the hollow ratio and foam porosity or increasing Reynolds and rotation numbers, while two contradictory trends are found for the impact of increasing pore density on heat transfer; either enhancing or suppressing depending on the size of hollow zone. In addition, both rotation and thermal dispersion have dominant roles in enhancing heat transfer at the higher levels of porosity or the lower values of conductivity ratios. However, these roles are reduced gradually with decreasing the foam porosity or increasing thermal conductivity ratio, but do not completely vanish. Eventually, the worth of using high porosity fibrous media in enhancing the heat transported through rotating channels has been inspected. An overall enhancement parameter is compared for the current study with a previous work regarding turbulent flow in a rotating clear channel, where it has been confirmed that the current proposal is practically justified and efficient.

A numerical analysis for the fluid flow and heat transport phenomenon through a rotary thermal regenerator is presented by means of employing the porous media concept. An aluminum core formed of multi packed square passages is simulated as a porous medium of an orthotropic porosity in order to allow the counter-flowing streams to flow in a way similar to that inside the regenerator core. The geometric properties of the core were transformed into the conventional porous media parameters such as the permeability and the inertial coefficient based on empirical equations; so, the core has been dealt with as a porous medium of known features. Local thermal non-equilibrium situation is assumed between both fluid and solid phases, so heat is allowed to be exchanged between them. The results are presented by means of overall temperature effectiveness, pressure drop, and the relative output power. The use of porous media approach has been found to be sufficient to solve the current problem. The data obtained reveals an obvious impact of the core geometrical parameters on both the heat restored and the pressure loss; and hence, the overall efficiency of the regenerator system.

The experimental investigations of rotating heat exchangers are usually too costly and provide limited understanding for the phenomena of heat and fluid flow within them; hence, a less expensive and more comprehensive method is required to investigate what can affect their overall performance. In the current study, a porous media concept is presented as an alternative way to numerically analyse the fluid flow and heat transport through a rotary thermal regenerator. An aluminum core formed of multi-packed square passages is simulated as a porous medium of an orthotropic porosity in order to allow the counter-flowing streams to flow in a way similar to that inside the regenerator core. The geometric properties of the core were transformed into the conventional porous media parameters such as the permeability and inertial coefficient based on empirical equations; so, the core has been dealt with as a porous medium of known features. Fluid and solid phases are assumed to be in a local thermal non-equilibrium state with each other. A commercial CFD code "STAR CCM+" was used to solve the current problem numerically, where heat is allowed to be exchanged between the two phases and tracked by creating a heat exchanger interface in the core region. The results are presented by means of overall thermal effectiveness, pressure drop, and coefficient of performance COP. Using porous media approach has been found to be sufficient to simulate the current problem. The data obtained reveal an obvious impact of the core geometrical parameters on both the heat restored and pressure loss; and hence, the overall efficiency of the regenerator system.

The problem of double-diffusive flow in a long rotating porous channel has been analysed numerically. The two opposite vertical walls of the channel are maintained at constant but different temperature and concentration, while both horizontal walls are kept insulated. The generalised model is used to mathematically simulate the momentum equations with employing the Boussinesq approximation for the density variation. Moreover, both the fluid and solid phases are assumed to be at a local thermal equilibrium. The Coriolis effect is considered to be the main effect of rotation, which is induced by means of the combined natural heat and mass transfer within the transverse plane. The governing equations are discretised according to the finite volume method with employing the hybrid differencing scheme to calculate the fluxes across the faces of each control volume. The problem of pressure–velocity coupling is sorted out by relying on PISO algorithm. Computations are performed for a wide range of dimensionless parameters such as Darcy–Rayleigh number (100 ≤ Ra* ≤ 10,000), Darcy number (10−6 ≤ Da ≤ 10−4), the buoyancy ratio (−10 ≤ N ≤ 8), and Ekman number (10−7 ≤ Ek ≤ 10−3), while the values of Prandtl and Schmidt numbers are maintained constant and equal to 1.0. The results reveal that the rotation seems to have a dominant role at high levels of porous medium permeability, where it reduces the strength of the secondary flow, and hence the rates of heat and mass transfer. However, this dominance decreases gradually with lessening the permeability for the same level of rotation, but does not completely vanish.

The development of three-dimensional heat transfer and fluid flow in a square channel rotating in a parallel-mode has been investigated numerically. The duct is occupied by a foam material of high porosity (ɛ ⩾ 0.9) and subjected to a uniform wall heat flux. In regards to the influence of rotation, both the centrifugal buoyancy effect and Coriolis forces are considered in the current study. The generalised model is used to mathematically simulate the momentum equations employing the Boussinesq approximation for the density variation. Moreover, both the fluid and solid phases are considered to be in local thermal non-equilibrium. The governing equations are discretised according to the finite volume method employing the hybrid differencing scheme to calculate the fluxes across the faces of each control volume in the transverse plane. Computations are performed for a wide range of dimensionless parameters including the medium porosity (0.9 ⩽ ε ⩽ 0.97), rotation number (0 ⩽ Ro ⩽ 1.0), Darcy–Rayleigh rotational number (1.1 × 103 ⩽ View the MathML source ⩽ 6.2 × 105), and solid to fluid-phase thermal conductivity ratio (102 ⩽ κ ⩽ 103), while the values of Reynolds and Prandtl numbers are maintained constant at Re = 2000 and Pr = 0.7, respectively. The results reveal that the rotation seems to have a dominant role in enhancing heat transfer at high levels of porosity and low conductivity ratios. However, this role is reduced gradually with decreasing the medium porosity or increasing thermal conductivity ratio, but does not completely vanish. Eventually, the worth of using high porosity fibrous media in enhancing the heat transported through rotating channels has been inspected. An overall enhancement parameter was compared for the current study with a previous work regarding turbulent flow in a rotating clear channel, where it has been confirmed that the current proposal is practically justified and efficient.

In the present study, free convection heat and mass transfer of fluid in a square packed bed enclosure is numerically investigated. For the considered geometrical shape, the left vertical wall of enclosure was assumed to be kept at high temperature and concentration while the opposite wall was kept at low temperature and concentration with insulating both the top and bottom walls of enclosure. The Brinkman–Forchheimer extended Darcy model was used to solve the momentum equations, while the energy equations for fluid and solid phases were solved by using the local thermal non-equilibrium (LTNE) model. Computations are performed for a range of the Darcy number from 10-5 to 10-1, the porosity from 0.5 to 0.9, and buoyancy ratio from -15 to 15. The results showed that both the buoyancy ratio and the packed bed characteristics have significant effect on each one of the flow field, heat transfer and mass transfer.

In the present study, natural convection of fluid in a square packed bed enclosure is investigated numerically using a uniform magnetic field. The geometry model is heated from left-hand side vertical wall and cooled from opposite wall with adiabatic condition at both the top and bottom walls. Normally to this enclosure an electric coil was set to generate a uniform magnetic field. The Brinkman–Forchheimer extended Darcy model was used to solve the momentum equations, while the energy equations for fluid and solid phase were solved using the local thermal non-equilibrium (LTNE) model. Computations are performed for a range of the Darcy number from 10-5 to10-1, the porosity from 0.3 to 0.9, and Hartmann number from 0 to 75. The results showed that both the strength of applied magnetic field and the packed bed characteristics have significant effect on the flow field and heat transfer.

A numerical study for the developing laminar flow characteristics through a two dimensional channel which occupied by a porous media structure has been made in the present work. The study included the numerical solution of the continuity and momentum equations. A SIMPLE algorithm procedure was used in the developed computational algorithm, which is capable of calculating the hydrodynamic parameters, such as; velocity components, local and mean friction factors. Effect of Reynolds number, porosity and permeability on the behavior of flow are investigated. Results indicate that the flow velocity through the porous layers increase with increasing of anyone of the investigated parameters, and instantaneously it decreases in the clear region with increase the porosity and permeability but it increases with increase Reynolds number.

A numerical study [in the engineering sciences branch (No.8)] for the developing turbulent flow and heat transfer through a duct of square cross-section with suction and injection through the duct walls has been made in the present work. The study included the numerical solution of the [continuity, momentum, and energy equations together with the two equations of the (k-ε) turbulence model] by using the finite volumes method and with help of the SIMPLE algorithm procedure. The hydrodynamic and thermal properties of turbulent flow was studied at (Re=57890) and (Pr=0.72), where the results showed that the injection through the duct walls increases the rate of growth of boundary layer, while the suction decreases the rate of growth of boundary layer, also the friction factor values decrease with injection and increase with suction, finally the heat transfer levels and Nusselt number values decrease with injection and increase with suction.

Simulation of free convection heat transfer in a square enclosure induced by heated thin plate is represented numerically. All the enclosure walls have constant temperature lower than the plate’s temperature. The flow is assumed to be two-dimensional. The discretized equations were solved stream function, vorticity, and energy equations by finite difference method using explicit technique and Successive Over- Relaxation method. The study was performed for different values of Rayleigh number ranging from 103 to 105 for different angle position of heated thin plate(0°, 45°, 90°). Air was chosen as a working fluid (Pr = 0.71). Aspect ratio of center of plate to the parallel left wall A2 take a constant and is equal to 0.5. The effect of the angle position of the heated thin plate on heat transfer and flow were addressed. With the increase of Rayleigh number heat transfer rate increased in both vertical and horizontal position of the plate. For the vertical situation (γ=90°) of thin plate, heat transfer becomes more enhanced than for the horizontal situation (γ=0°) and the inclined situation (γ=45°) especially when the value of aspect ratio A1 is equal to 0.25.