scholarly journals Effect of Bed Particle Size on Thermal Performance of a Directly-Irradiated Fluidized Bed Gas Heater

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 967
Author(s):  
Sae Han Park ◽  
Chae Eun Yeo ◽  
Min Ji Lee ◽  
Sung Won Kim
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Gas Velocity ◽  
Bubble Behavior ◽  
Heat Transfer Characteristics ◽  
Maximum Value ◽  
Solar Thermal Collector ◽  
Sic Particle

There is a growing interest in a fluidized bed particle receiver that directly irradiates sunlight to particles in the fluidized bed as a solar thermal collector for heating. Thermal performance of directly-irradiated fluidized bed gas heater is strongly affected by the physical properties of the particles. The effect of SiC particle size on heat transfer characteristics in the solar fluidized bed gas heater (50 mm-ID × 100 mm high) has been determined. The outlet gas temperatures showed a maximum value with increasing gas velocity due to the particles motion by bubble behavior in the bed, and the maximum values were found at 3.6 times of Umf for fine SiC and less than 2.0 times of Umf for coarse SiC. Heat absorption from the receiver increased with increasing gas velocity, showing with maximum 18 W for the fine SiC and 23 W for the coarse SiC at 4.5 times of Umf. The thermal efficiency of the receiver increased with increasing gas velocity, but was affected by the content of finer particles. The maximum thermal efficiency of the receiver was 14% for fine SiC and 20% for coarse SiC within the experimental range, but showing higher for the fine SiC at the same gas velocity. A design consideration was proposed to improve the thermal efficiency of the system.

Heat Transfer Characteristics in an Airtight Oscillating Fluidized Bed and Their Relation with Bubble Behavior

2003 ◽  
Vol 29 (4) ◽  
pp. 585-587
Author(s):  
Seiichi Deguchi ◽  
Masayuki Deguchi ◽  
Mikitaka Isobe ◽  
Akira Nishimura ◽  
Yukihisa Fujima
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Bubble Behavior ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Influence of Fluidization Velocity on Bed Defluidization in Fluidized Bed Combustors

2005 ◽  
Author(s):  
Mohammad R. Golriz ◽  
Morgan Eriksson ◽  
Marcus O¨hman ◽  
Anders Nordin ◽  
Rainer Backman
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Large Scale ◽  
Particle Diameter ◽  
Operating Conditions ◽  
Biomass Combustion ◽  
Gas Velocity ◽  
Fluidization Velocity ◽  
Significant Difference ◽  
Superficial Gas Velocity

Effects of superficial gas velocity and bed particle size on bed defluidization during biomass combustion were investigated. Sampled bed particles from four different large-scale circulating- and bubbling fluidized bed combustors, using biomass as fuel, were collected and analyzed. The bed particles from each fluidized bed unit were divided into small and large particle size fractions. The results indicate no significant difference in elemental compositions between small and large coated bed particles but the ratio of coating thickness to the mean particle diameter was higher for the small particles compared to the large ones. Controlled fluidized bed agglomeration tests revealed strong influence from fluidization velocity on initial defluidization temperatures at lower velocities, but little effect at higher velocities. Influence of bed particle size on initial defluidization temperature varied depending on operating conditions. Finally, a model based on viscous flow sintering is proposed for the relation between agglomeration temperature and superficial gas velocity. The model predictions are in good agreement with experimental data.

Attrition of dolomitic lime in a fluidized-bed reactor at high temperatures

2013 ◽  
Vol 67 (2) ◽  
Author(s):  
Miloslav Hartman ◽  
Karel Svoboda ◽  
Michael Pohořelý ◽  
Michal Šyc ◽  
Michal Jeremiáš
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Mechanistic Model ◽  
Attrition Rate ◽  
High Grade ◽  
Gas Velocity ◽  
Dolomitic Lime ◽  
Elapsed Time ◽  
Three Samples ◽  
Inner Diameter

AbstractResults of an experimental study on the rate of attrition of lime catalyst/sorbent in a high-temperature, turbulent fluidized bed with quartz sand are presented. Batch measurements were conducted at 850°C in an electrically heated gasification reactor of the inner diameter of 5.1 cm with three samples of high-grade dolomitic lime of the particle size 450 μm, 715 μm, and 1060 μm, respectively. In addition to the influence of the particle size, the effect of operating (elapsed) time was investigated at different superficial gas velocities. Assuming that the attrition rate decreases exponentially with time, a simple mechanistic model, enabling the correlation of the measured experimental data, was developed. The course of the lime particles attrition is described as a function of the elapsed time, excess gas velocity, and particle size. The presented approach and the results might be applicable for the attrition of high-grade dolomitic lime, particularly in fluidized gasification of biomass.

A Study on Fluidized Bed-Type Particulate Filter for Diesel Engines

2007 ◽  
Vol 129 (4) ◽  
pp. 1072-1078 ◽  
Author(s):  
Sung-Sub Kee ◽  
Ali Mohammadi ◽  
Takuji Ishiyama ◽  
Takaaki Kakuta
Keyword(s):  
Particle Size ◽  
Diesel Engine ◽  
Pressure Drop ◽  
Fluidized Bed ◽  
Particle Diameter ◽  
Filtration Efficiency ◽  
Particulate Filter ◽  
Design Parameters ◽  
Gas Velocity ◽  
Bed Height

A fluidized bed-type diesel particulate filter (DPF) was applied to filter particulate matter (PM) in diesel engine exhaust gas. The effects of the fluidized bed design parameters, such as gas velocity, bed particle size, and height, on PM and smoke filtration efficiencies, and pressure drop were experimentally investigated using a single-cylinder direct injection (DI) diesel engine. High PM filtration efficiency and low pressure drop were achieved with the DPF, especially at a lower gas velocity. The PM filtration efficiency was higher with a smaller bed particle size at the lower gas velocity; however, it drastically decreased with an increase in gas velocity due to excessive fluidization of the bed particles. Increase in bed height led to higher PM filtration efficiency while causing an increase in pressure drop. The theoretical work was also conducted for further investigation of the effects of the above-mentioned parameters on PM filtration. These results indicated that diffusion filtration was the dominant mechanism for PM filtration under the conditions of this study and that the decrease in PM filtration efficiency at high gas velocity was caused by a deterioration in the diffusion filtration. The bed particle diameter and the bed height should be optimized in order to obtain a high filtration efficiency without increasing the DPF size.

scholarly journals Effect of Particle Size on Carbon Nanotube Aggregates Behavior in Dilute Phase of a Fluidized Bed

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 121 ◽  
Author(s):  
Sung Kim
Keyword(s):  
Particle Size ◽  
Carbon Nanotube ◽  
Fluidized Bed ◽  
Laser Sheet ◽  
Scale Up ◽  
Experimental Parameter ◽  
Aggregate Size ◽  
Chemical Vapor ◽  
Gas Velocity ◽  
Effect Of Particle Size

Fluidized bed reactors have been increasingly applied for mass production of Carbon Nanotube (CNT) using catalytic chemical vapor deposition technology. Effect of particle size (dp = 131 μm and 220 μm) on fluidization characteristics and aggregation behavior of the CNT particles have been determined in a fluidized bed for its design and scale-up. The CNT aggregation properties such as size and shape were measured in the dilute phase of a fluidized bed (0.15 m-ID × 2.6 m high) by the laser sheet technique for the visualization. Two CNT particle beds showed different tendency in variations of the aggregates factors with gas velocity due to differences in factors contributing to the aggregate formation. The CNT particles with a larger mean size presented as relatively larger in the aggregate size than the smaller CNT particles at given gas velocities. The aggregates from the large CNT particles showed a sharp increase in the aspect ratio and rapid decrease in the roundness and the solidity with gas velocity. A possible mechanism of aggregates formation was proposed based on the variations of aggregates properties with gas velocity. The obtained Heywood diameters of aggregates have been firstly correlated with the experimental parameter.

Characteristics of Mixing/Segregation in a Bubbling/Slugging Fluidized Bed with Binary Mixtures

2011 ◽  
Vol 396-398 ◽  
pp. 322-325 ◽  
Author(s):  
Heng Zhi Chen ◽  
Zheng Kui Guo
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Binary Mixtures ◽  
Fixed Bed ◽  
Size Difference ◽  
Gas Velocity ◽  
Carbon Particles ◽  
Fluidization Regime ◽  
Superficial Gas Velocity

Fluidization behavior of binary mixtures with titanic slag particles and carbon particles had been investigated. Three solids states in the bed: fixed bed, transient fluidization and steady fluidization, emerges as increasing gas velocity. The extent of segregation of solids mixture in transient fluidization regime depended on the size difference between jetsam particles and flotsam particles. The effects of flotsam particle size, initial jetsam concentration and the superficial gas velocity on the segregation of binary solids had been measured.

scholarly journals Potential of Solar Collectors for Clean Thermal Energy Production in Smart Cities using Nanofluids: Experimental Assessment and Efficiency Improvement

2019 ◽  
Vol 9 (9) ◽  
pp. 1877 ◽  
Author(s):  
M. Sarafraz ◽  
Iskander Tlili ◽  
Mohammad Abdul Baseer ◽  
Mohammad Safaei
Keyword(s):  
Flow Rate ◽  
Thermal Performance ◽  
Tilt Angle ◽  
Thermal Efficiency ◽  
Smart Cities ◽  
Heat Pipes ◽  
Filling Ratio ◽  
Working Fluid ◽  
Solar Thermal Collector ◽  
Evacuated Tube

In this article, an experimental study was performed to assess the potential thermal application of a new nanofluid comprising carbon nanoparticles dispersed in acetone inside an evacuated tube solar thermal collector. The effect of various parameters including the circulating volumetric flow of the collector, mass fraction of the nanoparticles, the solar irradiance, the tilt angle and the filling ratio values of the heat pipes on the thermal performance of the solar collector was investigated. It was found that with an increase in the flow rate of the working fluid within the system, the thermal efficiency of the system was improved. Additionally, the highest thermal performance and the highest temperature difference between the inlet and the outlet ports of the collector were achieved for the nanofluid at wt. % = 0.1. The best tilt angle and the filling ratio values of the collector were 30° and 60% and the maximum thermal efficiency of the collector was 91% for a nanofluid at wt. % = 0.1 and flow rate of 3 L/min.

scholarly journals Experimental Study on the Thermal and Electrical Characteristics of an Air-Based Photovoltaic Thermal Collector

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2661 ◽  
Author(s):  
Sang-Myung Kim ◽  
Jin-Hee Kim ◽  
Jun-Tae Kim
Keyword(s):  
Flow Rate ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Solar Thermal ◽  
Electrical Performance ◽  
Energy Output ◽  
Inlet Flow ◽  
Pv Module ◽  
Solar Thermal Collector ◽  
Inlet Flow Rate

A photovoltaic thermal (PVT) system is a technology that combines photovoltaics (PV) and a solar thermal collector to produce thermal energy and generate electricity. PVT systems have the advantage that the energy output per unit area is higher than the single use of a PV module or solar thermal collector, since both heat and electricity can be produced and used simultaneously. Air-based PVT collectors use air as the heat transfer medium and flow patterns are important factors that affect the performance of the PVT collector. In this study, the thermal and electrical performance and characteristics of an air-based PVT collector were analyzed through experiments. The PVT collector, with bending round-shaped heat-absorbing plates, which increase the air flow path, has been developed to improve the thermal performance. The experiment was done under the test conditions of ISO 9806:2017 for the thermal performance analysis of an air-based PVT collector. The electrical performance was analyzed under the same conditions. In the results, it can be found that the inlet flow rate of the PVT collector considerably affects the thermal efficiency. It was analyzed that as the inlet flow rate increased from 60 to 200 m3/h, the thermal efficiency increased from 29% to 42%. Then, the electricity efficiency was also analyzed, where it was determined that it was improved according to operating condition of PVT collector.

Sesame and Broad Bean Stalks: Mixing Characteristics of Chips as a Biomass Fuel for Bubbling Fluidized Bed Combustor

2018 ◽  
Vol 16 (6) ◽  
Author(s):  
Saad A. El-Sayed ◽  
Amro A. El-baz ◽  
Emad H. Noseir
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Mass Fraction ◽  
Broad Bean ◽  
Sand Particle ◽  
Gas Velocity ◽  
Mixing Index ◽  
Bubbling Fluidized Bed ◽  
Superficial Gas Velocity ◽  
Fluidized Bed Combustor

Abstract Mixing and segregation characteristics of biomass particles are of practical importance because the in-bed combustion efficiency of volatile matter affects the vertical location of biomass in bubbling fluidized bed combustor. Sesame and broad bean stalk biomass materials mixed with sand used in this study. The superficial gas velocity, biomass chip length, sand particle size and mass fraction of biomass varied as experimental variables. The mixing and segregation behavior of mixtures were analyzed in terms of mixing index. It was found that the variability in the chip-shape made the sesame chips is quantitatively and qualitatively higher homogeneity and mixedness than the broad bean chips. The optimum overall mixing index for the sesame and the broad bean is around 0.96 and 0.84 at dimensionless superficial gas velocity (U/Umf) of 2.0 (1.40 m/sec) and 2.1 (1.25 m/sec), respectively. It was found that as the mean diameter increased and the sphericity decreased, the mixing quality decreased. The average sand particle size of 371 µm can keep good mixing with biomass chips of both materials, compared with average particle sizes of sand 550 and 700 µm. Increasing the initial biomass mass fraction yields a poor mixing of the investigated biomass stalks.

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