Fluidization Number Research Articles

Impact of random packing on residence time distribution of particles in bubbling fluidized beds: Part 1–cross-current flow reactors

In this work, the influence of employing random packings on the residence time distribution in a bubbling fluidized bed is investigated. The bubbling fluidized bed cold-flow reactor setup allows for continuous cross-current flow of particles. Expanded clay aggregate (ECA) is employed in the packed-fluidized bed experiments as the packing. The effects of different parameters such as packing type (ECA or no packing), Fluidization number (4.4, 6.6, and 8.8), and solid throughflow rates (92, 133, and 164 g/s) are investigated. The axial dispersion and tank-in-series models are used to categorize flow patterns of particles in the packed-fluidized beds and compared to beds using no packing. Results show that the vessel’s dispersion number for solids decreases in the presence of ECA packings up to fourfold compared to unpacked beds. Furthermore, tank-in-series model shows that the number of tanks for experiments utilizing packing increases by up to threefold compared to unpacked beds. The experimental results are also compared to a model known as a hybrid model. The hybrid model considers a continuous-stirred-tank-reactor in series with a plug-flow-reactor. Comparison of the model to the measured data shows a clear shift of the relative size or residence time from the stirred tank reactor towards the plug flow reactor with axial dispersion in the packed-fluidized bed compared to a bed with no packing. Also the vessel dispersion number of the plug flow reactor model with axial dispersion is significantly decreased in the case of packed-fluidized bed.

A new quantitative method via on-line mass spectrometer: Application in biomass char/NO reaction

A novel quantitative analysis method via on-line mass spectrometer (OMS) was developed to calculate the mass flows of the reactants and products for the reaction between NO and biomass char in micro-fluidized bed. The experimental results showed that the quantitative method could accurately calculate the mass flow rate of each gas even though there were ion currents overlapping at mass-to-charge ratio (m/z) = 12,16, and 28 when CO, CO2 and N2 were simultaneously present in OMS. Furthermore, the method facilitated the quantitative analysis of gaseous reactants and products, thereby enabling the assessment of mass conversions of carbon (C) and nitrogen (N) in the NO reduction reaction. It was observed that CO was the predominant carbon-containing product in the reaction involving biomass char and NO at 900 °C, with over 96 % of nitrogen in NO participating in the reduction reaction being converted to N2. This study also revealed that increasing the fluidization number, NO concentration, and temperature in the micro-fluidized bed could significantly accelerate the conversion processes of C and N in the reduction of NO by biomass char. The peak mass flow rates of CO, CO2, and N2 were found to increase correspondingly with higher NO concentrations and temperature levels. The NO reduction process over sawdust char was compared to that of corncob char, showing a higher maximum NO reduction efficiency. The reaction order with respect to NO concentration was determined to be 0.82 for corncob char and 0.68 for sawdust char. Additionally, the apparent activation energies were determined to be 92.35 kJ/mol for corncob char and 125.60 kJ/mol for sawdust char, respectively.

KINETICS OF DRYING OF DISPERSED MATERIAL IN THE APPARATUS OF PERIODIC ACTION WITH FLUIDIZED BED

A theoretical method for calculating a periodically operating fluidized bed dryer is presented based on the zonal method for describing kinetics and an example of calculation is given in relation to the drying of pea grain. In the calculation, it is assumed that the solid phase in the apparatus is completely mixed, and the gas is ideally displaced, the particles have a spherical shape and are the same in size. Accounting for changes in the parameters of the drying agent in the layer is carried out on the basis of the equations of material and thermal balance for the layer with the division of the entire range of changes in the moisture content of the material into a number of concentration zones. The change in the temperature of the dried particles during the process is calculated based on the analytical solution of the linear heat conduction problem at a constant ambient temperature and the condition that moisture evaporation occurs at the surface of the particles (there is no internal evaporation). The calculation is carried out using the method of successive approximations. First, the duration of drying of the material in the concentration zone under consideration is set, then the average air parameters are determined by the height of the layer and by the drying time, and, using these data, by solving the problem of mass conductivity (moisture diffusion), the drying duration in the zone under consideration is determined and compared with the preset one. If there is a significant discrepancy, a second calculation iteration is carried out, taking the drying time found in the first calculation iteration. Calculations are carried out until an acceptable match between the previously accepted and calculated drying time. Then they move on to the second concentration zone, for which they do the same. The total drying time is equal to the sum of the times in the concentration zones. This technique was tested using the example of calculating the drying of pea grains. In the calculations, we used data previously found by the authors on the coefficient of mass conductivity (moisture diffusion), as well as literary reference data on the coefficients of thermal conductivity, thermal diffusivity and heat capacity of this material. Heat and mass transfer coefficients were calculated using criterion equations given in the literature. To select the operating air speed, the speed of the beginning of fluidization was calculated; the operating air speed was taken at a fluidization number of 1.05. The calculation of the Biothermal and mass transfer criteria showed that the thermal problem is mixed (the Biothermal number is 5.81), i.e. the heat transfer process is influenced by both internal and external heat transfer. The problem of mass transfer is purely internal (the modified mass transfer Bio number is 122.5), which was taken into account when calculating the drying time. The calculated drying curve was compared with the experimental one. A diagram of the experimental setup is given and a description of the experiment is given. Satisfactory agreement between the calculated and experimental drying curves indicates the correctness of the calculation method under consideration, which can be recommended for engineering use. For citation: Rudobashta S.P., Zueva G.A., Babicheva E.L. Kinetics of drying of dispersed material in the apparatus of periodic action with fluidized bed. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 109-118. DOI: 10.6060/ivkkt.20246706.6968.

Experimental investigation and modeling of the impact of random packings on mass transfer in fluidized beds

This study investigates the impact of two novel settings of bubbling fluidized beds equipped with random metal packings on the mass transfer. To do this, a comprehensive approach is applied that integrates experiments and modeling and explores the relevance of the different underlying mechanisms involved in interphase mass transfer in fluidized beds. Firstly, the mass transfer of water from moisturized silica gel particles to dry air is studied in both a packed-fluidized bed and a freely bubbling bed with no packing. The experimental set-up consists of a cylindrical bubbling fluidized-bed column with an inner diameter of 22 cm. Silica-gel particles with a mean particle diameter of 797 μm are used as bed material. The total bed amount ranges from 4 to 8 kg, while the fluidization number (F) varies between 1.7 and 2.3. Two types of packing, RMSR (stainless steel thread saddle rings) and Hiflow (stainless steel pall rings) are examined and compared to the reference case of a bubbling bed with no packing. The height of the packed section is maintained at 60 cm. The results show that, at all operating conditions, the use of packings enhances the amount of desorbed water in the fluidized bed. The increase is up to 17%, as compared to the bed without packing. The effect is believed to be inhibition of bubble growth in the packed-fluidized bed. To study this further, a mass-transfer model is introduced to analyze the different mass-transfer steps (intra-particle, particle surface to emulsion gas, and emulsion gas to bubble gas) in packed-fluidized beds compared to beds with no packing. TGA experiments are applied to describe the intra-particle mass transfer through a desorption kinetic model. Model analysis shows that the main resistance for mass transfer occurs across the bubble-emulsion boundary. The calculated value of the mass transfer coefficient for this, Kb, at reference conditions (6 kg of silica gel and F = 2.3) is 7.6e-5 s−1 with packings (in average) and 6.2e-5 s−1 without packings, i.e. a 23% improvement in the governing mass-transfer coefficient.

Effect of fluidized bed shapes on gas-solid fluidization characters and flow regime transition

The technology of gas-solid dense-phase fluidized bed separation is applied in the separation of fine particles in minerals due to its stable and reliable characteristics. The experiment collected time-domain distribution signals of pressure drop from fluidized beds with different shapes, systematically analyzed the spatiotemporal distribution characteristics of bed density, and studied the effects of bed shape and fluidization number N on the fluidization and flow transition of the bed layer. The results indicate significant differences in Umf among fluidized beds with different shapes, and the tapered bed requires the highest energy for fluidization. When N=1.3, the cylindrical bed layer is the most stable, maintaining an average density of 1.8 g/cm3, with a density fluctuation variance of 0.02 g/cm3. Additionally, when N<1.0, almost no bubbles inside the bed layer. With an increase in gas velocity, the time-domain distribution of pressure drop signals shows different degrees of fluctuation. When N=1.1, Conspicuous non-uniform particle flow is evident in the tapered bed, with a bubble main frequency of 8 Hz, an amplitude of 27.1, and the highest pressure drop energy signal, indicating that the tapered bed enters the bubbling state prematurely. Finally, fine coal separation experiments were conducted, and the results showed that the minimum E value for the cylindrical bed is 0.08 g/cm3, while the maximum E value for the tapered bed is 0.17 g/cm3.

Study on density distribution characteristics and fine coal separation of magnetically fluidized beds of microfine particles

ABSTRACT In this paper, the characteristics of the axial and the radial density distribution and the density stability of a gas-solid fluidized bed formed by microfine magnetite powder were studied under different fluidizing gas velocities and magnetic field intensities, and the separation experiments of −6 mm fine coal were carried out. The experimental results show that the axial density of the bed with magnetic field applied is lower than that without magnetic field applied under different gas velocities. The density fluctuation of the gas-solid fluidized bed with magnetic field is smaller than that of the ordinary gas-solid fluidized bed, and the stability of the bed density decreases with the increase of the fluidization number. The experimental results of separation of −6 mm fine coal show that the Ep value increases with the increase of fluidization number. Under the same fluidization number, the Ep value of −6 + 3 mm coal is smaller than that of −3 + 0.5 mm coal. When the fluidization number is 1.1, the Ep value of −6 + 3 mm coal is 0.0375 g/cm3, and the Ep value of −3 + 0.5 mm coal is 0.0475 g/cm3. This shows that the magnetically fluidized bed of microfine particles has a good separation effect for −6 mm coal.

Combustion of waste solids in a fluidized bed to generate sustainable energy

Exploring alternative options to address the impending global energy crisis while taking into account environmental concerns and climate change mitigation and addressing the sky-rocketing energy demand has become urgently essential. This need is further highlighted by the significant reliance of the Republic of Serbia on imported energy sources so that the focus of its energy sector strategy is rational use of energy resources, use of renewable energy sources (RES), and waste management with satisfying environmental regulations. The use of low-calorific and waste materials in conjunction with fluidized bed combustion technology is a method to achieve all the above goals synergistically. This paper presents experimental results of combustion of several solid wastes (coal mining waste from the ?RB Kolubara? complex, Serbia, paper sludge and hazelnut shells), conducted in an industrial prototype and experimental bubbling FB boiler (capacity up to 500 kW). Burning these wastes has a variety of advantages, including recovering substantial energy remaining in the waste and minimizing the overall waste volumes. The work focused on determination of furnace temperature profiles, composition of the flue gas at the furnace outlet as well as fluidization air and fuel flowrates, the minimum fluidization rate, fluidization number, maximum heat output and the transferred heat of the tested fuels. Based on the obtained results, potentials of FBC of waste fuels and the possibility of utilization of their energy potential are evaluated.

Oxygen Carrier Circulation Rate for Novel Cold Flow Chemical Looping Reactors

To achieve net-zero emissions by the year 2050, carbon capture, utilization, and storage technologies must be implemented to decarbonize sectors with hard-to-abate emissions. Pressurized chemical looping (PCL) with a novel reactor design called a plug flow with internal recirculation (PFIR) fluidized bed is proposed as an attractive carbon capture technology to decarbonize small- and medium-scale emitters. The objective of this work is to examine the solid circulation rate between redox reactors in a cold flow chemical looping facility using an energy balance approach. The effects of static bed height, weir opening height, purge configuration, and gas flow rate on solid circulation rate were investigated. It was determined that parameters that greatly affected the total gas momentum, such as the fluidization ratio or number of purge rows, tended to also have a large effect on solid circulation rate. Parameters that had a small effect on total gas momentum, such as bed height, did not have a measurable effect on solid circulation rate. It was noted that parameters that posed a restriction to solids flow, such as a vertical purge jet or the weir itself, decreased the solid circulation rate compared to similar tests without restrictions.

Anticipating of ash agglomeration behavior in a fluidized bed by population balance equation

Ash agglomeration as a potential problem in fluidized bed gasifiers, leading to defluidization, was investigated in this study in a lab-scale fluidized bed. The experiments were carried out in batch mode in the temperature range of 600–950 °C and atmospheric pressure. The defluidization temperature was determined from the total pressure drop across the bed. The effect of superficial gas velocity on the defluidization temperature was also investigated. With increasing the gas velocity, the defluidization temperature increases up to about 960 °C, beyond which it remained almost constant. The particle size distribution at the end of the tests (defluidization state) was estimated from the population balance equation. Assuming a first order growth rate of agglomerates, the parameters of the rate equation were determined by fitting the population balance equation to the size of the agglomerates at the moment of defluidization. The results showed that as the gas velocity increases, the frequency factor of the growth rate equation initially decreases up to the fluidization number 3, after which it remains constant.

Investigation of fluidization characteristics and separation performance of trapezoidal gas-solid fluidized bed

ABSTRACT A trapezoidal gas-solid fluidized bed separation system was designed to improve the separation space and processing capability of the gas-solid separation fluidized bed by combining inclined air distribution plates with horizontal air distribution plates. The distribution pattern of bed density was investigated under different operational conditions. The results showed that the operational conditions significantly influenced the standard deviation of bed density fluctuation and the skewness of bed density. When the fluidization number of the horizontal section and inclined section are 1.4 and 1.2 respectively, the aperture of the distributor plate is 6–2 mm, and the static bed height is 150 mm, the minimum standard deviation of bed density fluctuation (Sρ) is 0.07 g/cm3, and the skewness of density fluctuation (SKρ) was less than 0, indicating good fluidization quality of the bed under these conditions. Experimental separation tests of 13 ~ 6 mm raw coal were conducted in both the horizontal section of the bed and the overall trapezoidal fluidized bed, and the results showed that under the operational conditions with the best stability of bed density, ash separation was most prominent, with a possible minimum deviation (E) value of 0.120 g/cm3. Furthermore, under the same operational conditions, the maximum processing capacity of the horizontal bed section was 300 g, while the trapezoidal gas-solid fluidized bed with inclined air distribution plates could achieve a maximum processing capacity of 400 g, indicating that the trapezoidal gas-solid fluidized bed effectively expanded the separation space.

Steam Gasification in a Fluidized Bed with Various Methods of In-Core Coal Treatment

The aim of this work is to study coal steam gasification with various methods of coal in-core treatment in FB using a newly developed thermodynamic calculation method. A calculational study of subbituminous coal steam non-catalytic gasification was carried out using four different methods of coal in-core treatment in single-vessel multisectional fluidized-bed gasifiers. A semi-empirical model based on the entropy maximization thermodynamic method and “restricted equilibria” based on previously obtained experimental data has been developed. Based on thermodynamic calculations, the effect of the leading thermochemical processes and operating parameters of the fluidized bed (temperature, fluidization number, steam/coal ratio feed rate) was revealed. New information was obtained regarding the composition of char and syngas at the gasifier outlet, the syngas heating value, and the cold gas efficiency of the steam gasification of Borodinskiy subbituminous coal char. The results indicate the possibility of significantly accelerating and improving non-catalytic steam gasification in fluidized bed gasifiers through the appropriate organization of in-core coal treatment. Based on the results obtained, the following recommendation is made—when designing multi-section and multi-vessel steam-blown gasifiers, the ratio of residence times should be set in favor of increasing the coal residence time in the steam-blown carbonization zone. Structurally, this can be achieved by increasing the volume and/or area of the steam-blown carbonization section (vessel).

Apparent viscosity of high-density fluidized bed and synergistic effect of density and apparent viscosity on particle separation

ABSTRACT For gas-solid fluidization separation, mineral particles are separated under the joint action of bed density and apparent viscosity. In present study, the apparent viscosity of high-density binary mixture media was investigated by the falling ball method. Moreover, the significant effects of bed density and apparent viscosity on simulated mineral pellets and their interactions were investigated. The apparent viscosity model of high-density gas-solid fluidized beds was modified, and it was found that the Pearson correlation coefficient is 0.86. The results show that the apparent viscosity of high-density gas-solid fluidized bed decreases with increasing fluidization gas velocity. When the fluidization number is higher than 1.3, the apparent viscosity is basically stable in the range of 3.96–5.21 Pa·s. Under low apparent viscosity, when the pellet diameter is 20 mm and the density difference ∆ρ is greater than 0.27 g/cm3, gravity is the dominant factor affecting the settling behavior of the pellet. Under high apparent viscosity, the effect of viscous resistance on the settling behavior of pellets is dominant when the ∆ρ is less than 0.27 g/cm3. Based on the performed analyses, the low-viscosity medium can be selected for the separation of large mineral particles. Furthermore, for high-viscosity medium, the influence of bubbles on particle sedimentation can be effectively alleviated and it can be selected for the separation of small particles.

In-situ desulfurization using porous Ca-based materials for the oxy-CFB process: A computational study

Within circulating fluidized bed (CFB) processes, gas and solid behaviors are mutually affected by operating conditions. Therefore, understanding the behaviors of gas and solid materials inside CFB processes is required for designing and operating those processes. In addition, in order to minimize the environmental impact, modeling to reduce pollutants such as SOx emitted from those processes is essential, and simulation reproduction is necessary for optimization, but little is known. In this study, the gas and solid behaviors in a pilot-scale circulating fluidized bed combustor were investigated by using computational particle fluid dynamics (CPFD) numerical simulation based on the multiphase particle-in-cell (MP-PIC) method under oxy-fuel combustion conditions. In particular, the combustion and in-situ desulfurization reactions simultaneously were considered in this CPFD model. Effect of fluidization number (ULS/Umf) was investigated through the comparison of particle circulation rates with regards to the loop seal flux plane and bed height in the standpipe. In addition, the effects of parameters (temperature, Ca/S molar ratio, and particle size distribution), sensitive indicators for the desulfurization efficiency of limestone, were confirmed. Based on the cycle of the thermodynamic equilibrium curve of limestone, it is suggested that direct and indirect desulfurization occur simultaneously under different operating conditions in CFB, creating an environment in which various reactions other than desulfurization can occur. Addition of the reaction equations (i.e., porosity, diffusion) to the established simple model minimizes uncertainty in the results. Furthermore, the model can be utilized to optimize in-situ desulfurization under oxy-CFB operating conditions.

Particle Residence Time Determination with More Than 400 Tracer Particles in a Circulating Fluidized‐Bed Full‐Loop System

AbstractThe residence time of particles in a circulating fluidized‐bed (CFB) reactor is the essential parameter for design and performance of a CFB system. In this work, a noninvasive measurement method of positing tracer particles in a full‐loop CFB system is proposed. Based on the radio frequency identification technology, more than 400 tracer particles with individual code were made and moved freely in the CFB full loop system. With detecting the tracer particles' trajectory by high‐frequency readers located outside of the system, the effects of operating parameters including fluidization number and solid inventory on the movement and residence time of the tracer particles in the CFB system were investigated. The particle residence time is distributed in a certain range, influenced by superficial gas velocity and solid inventory.

Heat transfer behavior of an immersed tube with sCO2 working fluid in a hot fluidized bed at high pressure

In this work, a pilot-scale pressurized fluidized bed test rig was built to test the heat transfer performance between the supercritical CO2 (sCO2) loaded immersed tube with the dense bed. Results showed that the bed-to-tube heat transfer coefficient (HTC) in CO2 atmosphere was slightly larger than that in air atmosphere. The HTC increased with the increase of pressure and bed temperature, respectively. The increase of pressure did not change the circumferential distribution of HTC, but the increase of fluidization number improved it. A bed-to-tube heat transfer model was proposed on the basis of the partial heat penetration theory with the accuracy in ±25 %. For the heat transfer of sCO2 within the immersed tube deteriorated due to the buoyancy effect.

Bubble hydrodynamics of adding fine particles in 2D pulsed fluidized bed

The bubbling behavior of powders in the range of 30–2600 µm is well understood. However, the bubbling behavior in binary-medium pulsed fluidized beds is complex and has received little attention. Therefore, Geldart C and B magnetite powders were mixed to form a dense medium. The effects of C particles and frequency on the minimum fluidization gas velocity, bubble area, number, shape factor, and aspect ratio were studied. The results show that the introduction of pulsating energy can increase the bubble area but decrease the number of bubbles. Under an appropriate content of fine particles, the pulsating energy increases the bubble shape factor and reduces the aspect ratio. A bubble size growth model was developed. A pulsed fluidized bed mixed-medium minimum fluidization velocity model was developed with 10% error. A pulsed fluidized bed bubble size model was developed with a prediction error of 10% or less.

Effects of process parameters on preparation of Ti@SiO2 particles during fluidized bed chemical vapor deposition via design of experiments

Fluidized bed chemical vapor deposition (FBCVD) is a promising technology for preparing photocatalysts. However, the photocatalyst performance depends on numerous parameters, and the effects of process parameters on photocatalyst performance are not well understood. In this work, the effects of deposition time, fluidization number, reactant molar ratio and deposition temperature on photocatalysts prepared by FBCVD are investigated via a full factor factorial design approach, which is a kind of Design of Experiments. The results show that the deposition time, reactant molar ratio and deposition temperature are the main factors affecting the photocatalytic performance, while the fluidization number and the interactions between different parameters are insignificant factors. The characterization of the elemental content, elemental distribution and crystalline structure of Ti-deposited SiO2, Ti@SiO2, particles reveals that the formation of Ti-O-Si bonds and Ti-based nanoparticles on the Ti@SiO2 surface enhances the photocatalytic performance of the particles. Finally, the formation mechanisms of Ti@SiO2 particles are summarized which can be distinguished into two stages. At around 120 °C, intermediates such as Ti(OH)4 are generated and reactions consist of homogeneous and heterogeneous reactions. At around 400–600 ℃, the Ti@SiO2 particles are formed, which is dominated by heterogeneous reactions. The results of this study can improve understanding and control of photocatalyst preparation.

Numerical simulation study on mixing characteristics of binary Geldart-D particles in a pressurized fluidized bed

Understanding the mixing behaviors of different particles is significant for improving the mass and heat transfer performance of a pressurized fluidized bed. A numerical simulation study on the mixing behavior of binary Geldart-D particles in a pressurized bubbling fluidized bed is performed based on the CFD-DEM method. The mixing characteristics and bubble behavior of binary Geldart-D particles with different physical properties under elevated pressure are investigated in the current study. Increasing the fluidization gas velocity u g and operating pressure P could promote the mixing of the particles. Raising the operating pressure P would cause a smaller bubble size and large bubble quantity at the same fluidization number u g /u mg . Higher operating pressure P and fluidization number u g /u mg could create a stable and uniform distribution of jetsam in the fluidized bed. • Mixing behaviors in the pressurized fluidized bed are investigated by CFD-DEM. • Minimum fluidization velocity decrease as the increase of operating pressure. • Bubble size decreases as raising operating pressure of fluidized bed. • High operating pressure and gas velocity promote the mixing rate of particles.

Relationship of particle size, reaction and sticking behavior of iron ore fines toward efficient fluidized bed reduction

The relationship of particle size, reaction and sticking behavior of iron ore fines toward efficient fluidized bed hydrogen reduction were systematically investigated at 600–800 °C in a laboratory fluidized bed. First, the reduction kinetics were studied, and the results showed that hydrogen reduction of granulated iron ore was controlled by reduction reaction, and the activation energy was approximately 88.4 kJ/mol. The reduction rate of granulated iron ore with a diameter of 200 μm could be increased by 10 times as the reduction temperature rose from 600 to 800 °C. Then, a modified force balance model was established to distinguish the critical sticking point of granulated iron ore during high temperature fluidized bed hydrogen reduction, and it indicated that the defluidization temperature could be raised from 630 to 790 °C as the particle size was enlarged from 100 to 200 μm with a fluidization number of 10. Eventually, coupling the kinetic model and modified force balance model, the maximum gas utilization rate of fluidized bed hydrogen reduction was estimated, and it indicated that at reduction temperatures of 650–750 °C with particle sizes of 200–300 μm, the optimal gas utilization rate could be achieved, which was consistent with the experimental results. Contradictory to traditional understandings of chemical reaction engineering, due to the interaction of reduction performance and sticking behavior, too high of a reduction temperature or too small of a particle size might not be preferable for fluidized bed hydrogen reduction, and this study provided valuable references for industrial operation.

Experimental investigation of heat transfer from elliptic tubes heat exchanger immersed in a fluidized bed

In this work, heat transfer, wall-to-bed, characteristics from elliptic tubes heat exchangers, both inline and staggered tubes arrangements, were studied experimentally. Bundles of twenty tubes of the same total surface area of 0.015 m2 and a length of 200 mm are immersed in a bed of granulated charcoal of different grain sizes, 2, 4 and 6 mm. Air was used as a fluidizing fluid. One of these tubes which was made of copper, instrumented, electrically heated and positioned in the middle of tube bundle, while the others are wooden dummy to be influenced only by the presence of the neighbouring tubes. Measurements are reported in the range of fluidization number within range of 1 to1.4. The results showed that, the local Nusselt number around the elliptic heated tube is about uniform with its maximum value at the tube sides and minimum at the stagnation and rear points of the tube. In addition, the average Nusselt number increases with the increase of the fluidization number and with the decrease in particle diameter. Heat transfer characteristics were found to improve in staggered tube bundle if compared with the inline tube arrangements. The present results of pressure drop and average Nusselt numbers were validated with a numerical model of the same conditions for the case of particle diameter of 2 mm. Good qualitative and quantitative agreements have been achieved between experimental and numerical data. Finally, correlation equations for the average heat transfer in terms of Nu, fluidization number and tube to particle diameter ratio are deduced.