High Heat Transfer Rates Research Articles

Study on Flow and Heat Transfer Characteristics of 25 kW Flameless Combustion in a Cylindrical Heat Exchanger for a Reforming Processor

Flameless combustion has advantages such as low pollution and uniform temperature in the combustion chamber, making it an excellent option for heat exchangers. Previous studies have focused solely on the flameless combustion phenomenon, without considering its interaction with the target being heated. In this study, we conducted experimental and computational fluid analyses on a cylindrical reformer for reverse air injection flameless combustion. Typically, small-scale reformers of 10 kW or less are coaxial triple-tube cylindrical reformers. In contrast, multitubular reformers are used for larger-scale applications, since the heat transfer rate in single-burner cylindrical reformers decreases sharply as the scale increases. Flameless combustion, with high heat transfer efficiency, helps overcome the limitation of premixed burner. Compared with conventional premixed burners, flameless burner decreases the combustion gas outlet temperature by 30% at 25 kW while reducing energy consumption by 24% (owing to the high heat transfer rate) for a given cooling fluid outlet temperature. Furthermore, it is shown that introducing a ring at the combustion chamber exit can enhance combustion gas recirculation. The experimental result was confirmed through computational fluid analysis. It is concluded that for reverse air injection flameless combustion, the combustion gas recirculation rate in the combustion chamber is strongly related to the heat transfer.

Analysis of Thermal Performance of Polylactic Acid Nanocomposite by Using T-History Method

In this study, we perceived the thermo-physical boundary and the thermal efficiency of zinc oxide for volume fraction in polylactic acid based on a heat energy storage system was examined by using the T-history method. The use of the T-history method for the assessment of thermo-physical boundary describes the specific heat capacity and thermal conductivity enhanced in solid as well as liquid phases of the mixture until the addition of 0 to 0.025% of volume part of zinc oxide in the polylactic acid nanocomposite. After the addition of the zinc oxide, the heat of fusion falls and polylactic acid has a high rate of fusion related to 0.025% volume part of zinc oxide mixed with polylactic acid. Further zinc oxide-based polylactic acid nanocomposite has 31.30% and 13.5% higher solid as well as liquid thermal conductivity in comparison with polylactic acid. Moreover, raise the particle size and analysis as well as distributions found by dynamic light dispersing method for different volume parts of zinc oxide mixed on polylactic acid. In contrast to the thermal efficiency analysis of 0.025% of volume fraction zinc oxide in polylactic acid nanocomposite has a 30.6% high heat transfer rate related to pure polylactic acid along the stage of 4 minutes. Further, the addition of zinc oxide above 0.025% volume fraction in polylactic acid, rise the particle settlement rate freely. Whatever can become to end that 0.025% volume fraction of zinc oxide in polylactic acid mixed thermal energy storage arrangement outcome of maximum thermo physical property and thermal efficiency.

Effects of Hall Current and Activation Energy on a Three-Dimensional Rotating Casson Hybrid Nanofluid Flow over a Stretched Plate in the Presence of Joule Heating and Nonlinear Thermal Radiation

Nanofluids are of great importance to researchers as they have significant uses industrially due to their high heat transfer rates. Recently, a new class of nanofluid, ‘‘hybrid nanofluid” is being used to further enhance the heat transfer rate. This new model in 3D is employed to examine the impact of magnetic field, joule heating, rotation parameter, Hall current, with nonlinear thermal radiation, on a rotating hybrid Fe3O4/Al2O3 nanofluid over-stretched plate in the presence of chemical reaction is the focus of this research. Using similarity transformations, the controlling partial differential equations are turned into a set of nonlinear ordinary differential equations. For that system of equations, the shooting method is used to generate numerical solutions. The impact of various entry parameters on transversal and longitudinal velocities, temperature, heat flow and surface shear stress are studied numerically and graphically. A good correlation between the earlier studies is obtained in specific cases showing the convergence criteria of the present procedure. Further, the physical significance of the contributive parameters is presented through graphs and tables. The observation shows that the particle concentration for the hybrid nanofluid augments the fluid velocity. Moreover, the inclusion of dissipative heat favors enhancing the fluid temperature for the involvement of the particle concentration.

Compound passive heat transfer augmentation techniques: A comprehensive review

AbstractThe function of energy is becoming increasingly vital in meeting the requirements of modern societies and sustaining rapid economic and industrial growth globally. Heat transfer equipment has been employed for heat recovery and conversion in various domestic and industrial applications. Therefore, due to the recent global energy crisis, boosting the thermal efficiency of energy systems has become an essential requirement, which would reduce both their size and rates of energy demand. There are active and passive methods for boosting heat transfer rates. As they have no moving components, passive methods are more affordable and dependable than active ones. Applying two or more passive techniques concurrently will result in a higher heat transmission rate than any approach working independently. The current article comprehensively reviews experimental and computational investigations of passive compound forced convection heat transfer augmentation techniques at laminar, transition, and turbulent flow regimes. This article focuses on compound techniques arrangement in the form of turbulators, typical twisted tapes (TTs), surface roughness, vortex generators, and so on. The pioneering research suggests that using a lower twist ratio, lower pitch, and smaller winglet angles in TTs can result in higher heat transfer rates, albeit with a slightly increased friction factor. The combination of alternate‐axes and wings in TTs leads to more effective heat transfer enhancement within the tube.

2D MXene based nanocomposites for solar driven renewable energy storage utilizing binary eutectic phase change material

In this study, we incorporated eutectic phase change materials (EUPCM) into MXene nanopowder to strengthen the thermal properties of EUPCM. Here, Ti3C2 MXene was synthesized from Ti3AlC2 MAX phases via mild chemical etching using microwave and doped at concentrations ranging from 0.2 % to 1 % into binary eutectic of PEG 6000 and PEG10000. The FESEM validated the existence of adequate pores in the MXene structure and DLS revealed that approximately 66 % of the measured nanoparticles had a size of 218 nm. The FTIR and XRD investigations affirmed that the interaction between EUPCM and MXene was predominantly physical in nature. Differential scanning calorimetry (DSC) analysis revealed fusion enthalpies ranging from 163.5 J/g to 159.3 J/g and freezing enthalpies varying from 155.1 J/g to 146.2 J/g for the nanocomposites, keeping melting and freezing temperature. The incorporation of MXene resulted in a consistent decrease in time required for heating and cooling of EUPCM. Furthermore, the nanocomposites exhibited durability as demonstrated by thermal cycling tests, with no significant variation in the chemical structure and only slight fluctuations in the enthalpies after 500 melt/freeze cycles. Consequently, MXene-based nanocomposites display relatively high heat transfer rates compared to EUPCM for the same amount of solar radiation and present promising prospects for integration into solar energy storage systems.

The heat transfer potential of compressor vanes on a hydrogen fueled turbofan engine

Hydrogen is a promising fuel for future aviation due to its CO2-free combustion. In addition, its excellent cooling properties as it is heated from cryogenic conditions to the appropriate combustion temperatures provides a multitude of opportunities. This paper investigates the heat transfer potential of stator surfaces in a modern high-speed low-pressure compressor by incorporating cooling channels within the stator vane surfaces, where hydrogen is allowed to flow and cool the engine core air. Computational Fluid Dynamics simulations were carried out to assess the aerothermal performance of this cooled compressor and were compared to heat transfer correlations. A core air temperature drop of 9.5 K was observed for this cooling channel design while being relatively insensitive to the thermal conductivity of the vane and cooling channel wall thickness. The thermal resistance was dominated by the air-side convective heat transfer, and more surface area on the air-side would therefore be required in order to increase overall heat flow. While good agreement with established heat transfer correlations was found for both turbulent and transitional flow, the correlation for the transitional case yielded decent accuracy only as long as the flow remains attached, and while transition was dominated by the bypass mode. A system level analysis, indicated a limited but favorable impact at engine performance level, amounting to a specific fuel consumption improvement of up to 0.8 % in cruise and an estimated reduction of 3.6 % in cruise NOx. The results clearly show that, although it is possible to achieve high heat transfer rate per unit area in compressor vanes, the impact on cycle performance is constrained by the limited available wetted area in the low-pressure compressor.

A mechanistic model to predict saturated pool boiling Critical Heat Flux (CHF) in a confined gap

Boiling enables high rates of heat transfer from a surface made possible at a relatively low thermal resistance motivating the use of two-phase cooling for increasingly compact thermal management solutions. However, extreme geometrical confinement of the liquid above the boiling surfaces is known to have detrimental effects on maximum heat transfer rate by inducing premature onset of film boiling. Moreover, previously developed critical heat flux (CHF) models for confined geometries focused on triggering mechanisms associated with unconfined pool boiling and, thus, are not generalizable. This work proposes a new mechanistic model for predicting CHF during boiling within in narrow gap, specifically developed to account for confinement effects on the triggering mechanism. The model postulates that occurrence of CHF coincides with the irreversible growth of a dry spot on the boiling surface. Three competing forces govern the two-phase interface dynamics, namely vapor momentum, surface tension, and hydrostatic forces. Dryout is triggered when the vapor momentum force due to vaporization at the two-phase interface balances the combined surface tension and hydrostatic forces leading to irreversible growth of the dry spot. The present work offers a predictive confined CHF model that accounts for confined boiling surface shape, size, orientation, confinement gap spacing, and working fluid properties, with a single fluid-specific fitting coefficient that represents the ratio of vapor area to the confinement opening area near CHF conditions. Notably, the developed CHF model is also effective in predicting the threshold gap below which confinement reduces pool boiling CHF. The model is compared to 197 experimentally measured confined CHF data points available from 10 studies in the literature that represent 7 different working fluids and a range of boiling surface inclinations and shapes. The model predicts the confinement-reduced CHF values with a root mean square error of 21%, which is less than half of the error compared to all other available predictive models. This clarification of the triggering mechanism and improved prediction accuracy of CHF, as offered by the current study, will enable broader practical system implementation of compact two-phase cooling technologies.

Effect of pressure variations on film boiling characteristics of liquid nitrogen

Liquid nitrogen is a widely used cryogenic fluid in various industrial and scientific applications. Film boiling is inevitable when a hot surface is exposed to a cryogenic fluid like liquid nitrogen. This mode of boiling can affect the heat transfer rate and cooling efficiency of the process. The present study investigated the effect of operating pressure on film boiling characteristics of liquid nitrogen using continuum-based numerical simulations. Simulations were performed at atmospheric, intermediate, and near-critical pressures using a coupled level-set and volume of fluid method of interface tracking. Bubble dynamics and heat flux variations were examined at different degrees of wall superheat. The results show that the pressure condition significantly affects the bubble dynamics and boiling of liquid nitrogen. At higher pressure, the specific heat of the vapor phase increases, resulting in a higher heat transfer rate. It was also noted that at high levels of superheat, the bubbles detach from the heating surface faster, resulting in a higher transfer of heat. The effect of pressure on the number of bubble formation sites was also investigated. The simulations also reveal that the local thermodynamic conditions, such as pressure, temperature, and vapor concentration, significantly influence the bubble size.

An engineering model for the pyrolysis of materials

Accurately representing the time dependent heat release rate of fuels is critical to performance-based design in fire safety applications. Existing simplified models either use average pyrolysis rates at different heat fluxes or do not account for the change in burning behavior at higher heat transfer rates. This paper presents the theoretical basis of a scaling-based pyrolysis model, S-Pyro. The model is based on the concept of maintaining the shape of a reference heat release rate per unit area curve but scaling the magnitude and time based on a dynamic thermal exposure. The model has been implemented in the computational fluid dynamics software Fire Dynamics Simulator (FDS). The model is validated with solid-phase only and multi-phase simulations of cone calorimeter experiments. The solid-phase simulations evaluated the capability of the model to predict the heat release rate per unit area of 149 materials tested at heat fluxes other than the reference flux. Multi-phase simulations of bench-scale fire experiments with a single material, Canada Pine and Spruce plywood, were used to evaluate the performance of the pyrolysis model in FDS. The model uncertainty was lower for high heat release rate materials, with the model uncertainty approaching the experimental uncertainty at higher burning rates.

Experimental study of interface behavior and sound pressure oscillation of direct contact condensation of a steam jet in flowing water

Direct contact condensation of a vapor jet in liquid is frequently encountered in lots of industrial applications because of its high heat and mass transfer rates. However, severe interface and sound pressure oscillation associated with condensation might cause vibration and even failure of pipeline systems. In this paper, the interface behavior and the sound pressure oscillation of a steam jet in flowing water are captured respectively by a high-speed camera and a high-frequency hydrophone. According to the gray profile of the image, an identification method is proposed to determine the interface characteristics, including the plume shape, width, and penetration length of the jet. The statistical intensity and power spectrum density of the interface position and sound pressure oscillation of the steam jet are calculated. Two typical condensation regimes of Chugging and Oscillation-I under low steam mass flux (Gs < 346 kg/m2s) are observed. The intensities of the interface oscillation and sound pressure oscillation decline with increasing steam mass flux and a significant correlation coefficient of about 0.94 between them is revealed. With the incorporation of sound pressure parameters, two correlations of the dimensionless jet length and its oscillation intensity are established, with relative deviations of 20% between the experimental and predicted values. For Oscillation-I, the dominant frequencies of the interface oscillation and sound pressure oscillation are quantitatively consistent. From the time and frequency domain perspectives, it is quantitatively confirmed that the sound pressure oscillation of the steam jet under low steam mass flux is caused by its interface oscillation.

Effect of non-uniform heating on conjugate heat transfer and entropy generation characteristics within a partially filled porous corrugated channel

The persistence of the present numerical investigation is to evaluate the thermal and total entropy generation characteristics of flow within a partially filled porous wavy channel with finite wall thickness subjected to non-uniform wall heat flux. The average Nusselt number and the total entropy generation increase with the permeability value of the porous medium (Da) irrespective of asymmetric wall heat flux amplitude and wavelength as well as with the variation in thickness ratio and thermal conductivity value of the solid substrate. However, the total irreversibility decreases for a high Darcy number value when the phase angle between the applied heat fluxes is varied. Moreover, the average Nusselt number decreases up to a critical value of phase angle followed by a gradual increment for Da = 10−5 and 10−3, respectively. On the contrary, the reverse trend can be seen for Da = 10−1. The optimal choice of nonuniform heat flux amplitude, wavelength, and phase angle for a high heat transfer rate with minimum irreversibility generation is found to be 10 W/cm2, 5 mm, and 180°, respectively for a thickness ratio of 0.5 and thermal conductivity value of 646.07 W/m·K independent of Darcy number.

Theoretical analysis of convective transport over a slender body of revolution

The study of thermal transport in the laminar boundary layer had been a great area of research since long ago because of its practical necessity in different fields of engineering such as aerodynamics, electronics cooling, designing of turbine blades, etc. The primary goal of the research has always been to look into geometries or shapes that have higher heat transfer rates but a less viscous drag. This is also a topic of fundamental interest to the aerospace industry. For this purpose, a cone-shaped body of revolution has been considered. Such geometries are chosen due to their wider acceptance in modern aerodynamics, with their enhanced heat transfer rates and lower aerodynamic drag. In this connection, axisymmetric bodies of revolution having different body contours and involving surface transverse curvature are usually considered. The selection of such a curved body and the imposed particular type of momentum and thermal boundary conditions make the problem of non-similar nature. Such kinds of problems are normally dealt with by an implicit finite difference scheme due to the accuracy of the solution. The current problem has also been solved with the same numerical scheme. It is concluded that a more streamlined body of revolution has a less spread of velocity and temperature within the boundary layer with a large heat transfer rate and wall skin-friction. On the other hand, the parabolic body of revolution has a large distribution of velocity and temperature but less heat transfer rate and wall skin-friction. Moreover, the assisting role of surface transverse curvature on temperature distribution and wall skin-friction has also been observed in this study.

Investigation of Icephobic Coatings for Supercooling Heat Exchangers under Submerged Conditions Using Ice Detection Equipment

By using ice slurry generated through a supercooler as storage, it is possible to reduce energy consumption due to high energy density and heat transfer rate along with the phase change. The supercooled water will then be disturbed to create ice crystals in a crystallizer. The main challenge is to prevent the formation of ice in the supercooler since this leads to its blockage. One aim of the European H2020 TRI-HP project is to develop icephobic coatings for supercoolers, that promote high-water supercooling and avoid the formation of ice. In this study, three coatings to prevent or depress freezing in supercoolers are investigated. Specialized equipment for testing freezing on submerged surfaces has been developed, and the results have been correlated to standard surface properties like roughness and contact angle. It was found that the submerged surfaces do not necessarily follow normal icing theory, where freeze depression is related to contact angle. Instead, it is believed that the mobility of surface additives in amphiphilic coatings has an important role.

Numerical study on the flow and heat transfer characteristics in a high-temperature gas-cooled reactor core

In the high-temperature gas-cooled reactor (HTGR), the core operation heavily relies on the heat transfer process facilitated by the coolant that withdraws the heat released by fuel particles. Therefore, it is imperative to carefully study the flow and heat transfer characteristics between the fuel particle and coolant. Additionally, under high core temperature conditions, the fuel particle tends to incur damage. In this study, we have designed a new type of HTGR using hydrogen as a coolant, and performed numerical simulations to explore the flow and heat transfer conditions in the core under various working conditions. Our results indicate that under high velocity inlet and low temperature inlet conditions, the system provides a high heat transfer rate. Furthermore, interesting relationships were observed between the flow and heat transfer characteristics of the model through the Reynolds number (Re), n, and Tr. Since the density of the coolant changes as the temperature varies, the hydrogen is susceptible to compression. Notably, poor thermal conductivity on the fuel particle surface generates hotspots at the points of flow stagnation, flow separation, and flow convergence. Our study on the new reactor core's flow and heat transfer characteristics provides an important reference for improving the core outlet temperature and the fuel particle's structure.

Thermal convection and entropy generation analysis of hybrid nanofluid slip flow over a horizontal poignant thin needle with an inclined magnetic field: A numerical study

Hybrid nanofluids have emerged as a promising field of research in recent years, finding applications in various industries and sectors. The entropy generation and impact of an inclined magnetic field on a water-Ethylene Glycol (50:50) mixture-based nanofluid over a poignant thin needle has been investigated under slip conditions. The flow is swotted using thermal and velocity slip boundary conditions. The numerical effects of an inclined magnetic field on the flow of ferrous and aluminum oxide nanoparticles in a hybrid nanoliquid with as base fluids have been examined. The non-dimensional ODEs along with boundary conditions are solved by numerical technique based on the Runge–Kutta fourth-order method. Velocity profile has been analyzed for the magnetic parameter, inclined angle and volume fractions. The Bejan number provides insights into the balance between heat transfer and entropy generation in a system. From the numerical values of skin friction coefficient and Nusselt number, it is analyzed that [Formula: see text]O3 possesses 1.01% and 1.06% of high heat transfer rate and high surface drag force than [Formula: see text]O4. Heat transfer profile has been analyzed for entropy generation and the Bejan number. The applications of hybrid nanofluids are vast, and one specific area where they can be utilized is in horizontal needle systems.

A scientific report on Stokes' second problem for a transient nanofluid model with a heated boundary in the presence of a magnetic field

Stoke's second problem is a well-known classical boundary layer (BL) issue involving the time-dependent shear flow of viscous fluid about a flat porous plate in the magnetic field. This study has several applications, including chemical engineering, nanotechnology, heat conduction issues, and biological and medical sciences. A theoretical heat transfer (HT) analysis analyzes Stoke's second problem for an MHD time-dependent nanofluid flow through a porous plate. It produces a sinusoidal oscillation that is perpendicular to the flat plate. Copper (Cu) nanoparticles are suspended in water or ethylene glycol (EG), a base fluid. Modeling the fluid flow uses dimensional PDEs, which are then altered into dimensionless forms by adding the proper parameters. With no slip, the resulting non-dimensional PDEs are handled analytically by the Laplace transform approach (LTA). It is demonstrated that EG-Cu nanofluid has greater skin friction and higher HT rate than water-Cu nanofluid. Furthermore, skin friction is reduced by magnetic and porosity parameters, whereas the nanoparticle solid volume fraction and porosity parameters improve HT.

Liquid immersion thermal management of lithium-ion batteries for electric vehicles: An experimental study

The thermal and electrical performance of lithium-ion batteries subjected to liquid immersion cooling conditions in a dielectric fluid has been experimentally investigated in this study. A single 26650 LiFePO4 cylindrical cell is completely immersed in Novec 7000 and charged and discharged at onerous maximum rates of up to 4C and 10C, respectively, where C can be defined as the measure of the rate at which a cell is charged or discharged relative to its rated capacity. Immersion cooling offers high rates of heat transfer from the cell's surface, in particular when the saturation temperature of the fluid is exceeded, and two-phase conditions are established. At a preheated liquid pool temperature of 33 ± 0.5 °C for discharge rates ≥ 2C, subcooled boiling conditions develop, with the cell's temperature rise limited to 3.6 °C at the end of 10C discharge. Furthermore, for 4C charging under the same preheating conditions, the cell's temperature rise does not exceed 1 °C. Superior performance is observed under two-phase immersion cooling conditions in comparison to both single phase liquid immersion and natural convection air cooling for the same charge and discharge rates. Excellent thermal homogenisation across the cell is also determined, with a maximum axial temperature difference of 0.25 °C and 1 °C for 4C charging and 10C discharging respectively.

Tailored monolithic catalyst and reactor by direct photo-curing 3D printing for oxidative desulfurization of fuels

Structured monolithic catalysts have attracted growing attention in the petrochemical industry due to significant advantages of reusability, easy scale-up, and high heat and mass transfer rate. 3D printing offers enormous flexibility in accurately regulating the configuration of monolithic catalysts to realize the strengthening of the reaction process. However, this remains challenging in terms of reliable manufacturing, high resolution, and the distribution of active sites. Here, we report a direct photo-curing 3D printing based method for manufacturing precise monolithic catalysts for oxidative desulfurization of fuels. Numerous molybdenum oxide nanoparticles with a high density of oxygen vacancies are spatially distributed in three-dimensional Al2O3 by 3D printing technology and post-treatment, thus favoring the catalytic reaction. This 3D-MoOx/Al2O3 exhibits excellent catalytic performance with a 99.2 % conversion of dibenzothiophene. Furthermore, this tailored catalyst is 3D-printed to manufacture a monolithic agitating impeller as a stirring reactor, which plays a dual role in mixing and catalysis. The study provides an effective strategy for precisely manufacturing structured catalysts with excellent catalytic activity and can be readily applied to a range of chemical reactions.

Entropy analysis of slip flow second-grade Cu − EO and TiO 2 − EO nanofluids using Modified Buongiorno model

The current research investigates the magnetohydrodynamic (MHD) slip flow of second-grade nanofluids past a permeable stretching sheet in a porous medium. The flow analysis is accomplished considering thermophoresis, Brownian diffusion, chemical reaction, and elastic deformation. The implementation of the Modified Buongiorno model (MBM) on second-grade nanofluid is the novel aspect of the study. The formulated coupled nonlinear equations are non-dimensionalized, applying suitable similarity transformation. Numerical resolution of the resulting equations is achieved via MATLAB solver bvp4c. In our problem, two different groups of nanofluids, Cu − EO and TiO 2 − EO, have been considered. The development of profiles of nanofluid velocity, temperature, concentration, entropy generation and Bejan number, with the flow parameters, is elaborated graphically. Tabulated values of skin friction, Nusselt number, and Sherwood number are illustrated. The principal outcomes of this study demonstrate a higher rate of heat transfer of Cu − EO nanofluid than TiO 2 − EO nanofluid. The Nusselt number significantly decelerates, and the Sherwood number accelerates due to the combined influence of the Brownian diffusion and thermophoresis parameters. The second-grade parameter and nanoparticle volume fraction boost the skin friction magnitude. Furthermore, the entropy generation increases due to the Brinkman number and concentration diffusion parameter. The present research can be utilized to enhance the effectiveness of cooling systems in automobile engines, nuclear reactors, and heat exchangers. For the validation of our result, a comparative study is made with the previous authors and concludes in good agreement.

Effect of orange waste pretreatment on the fluid dynamics of spouted beds with mechanical agitation

The spouted bed has a vigorous cyclic movement of the solids and high rates of heat and mass transfer, allowing for effective contact between the different phases. However, the spouted bed may exhibit instabilities for inherently cohesive solids due to unwanted agglomeration, preferential channels, particle segregation and high energy consumption. In this context, the present work analyzed the effect of a preliminary treatment of the orange waste, through the addition of lime and mechanical pressing, on the fluid dynamics in two spouted bed configurations of same dimensions, one conventional (CSB) and the other one modified with mechanical agitation (modified mechanically spouted bed, MMSB). The preliminary treatment of the biomass allowed reducing the moisture content by 31.7%, thereby improving the movement of solids in the CSB as when the in natura (raw) biomass was loaded, as the latter underwent agglomeration until it no longer circulated. Persistent instability issues in the CBS were overcome through mechanical stirrers, which made the bed uniform by improving the movement of solids in the annular region. Furthermore, mechanical agitation allowed increasing the maximum static bed height from 21.1 to 27.0 cm, as well decreasing the air flow by up to 91.74%, since the air stream is only that required for bed expansion.