An investigation on the heat transfer model for immersed horizontal tube bundles in a pressurized fluidized bed

Bao, Zhongkai; Duan, Lunbo; Wu, Ke; Zhao, Chuanwen

doi:10.1016/j.applthermaleng.2020.115035

Cited by 10 publications

(4 citation statements)

References 41 publications

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“…Based on Figure 9, there is an upward trend of increasing the average heat transfer data with an increase in the superficial gas velocity, except for the values of the average heat transfer coefficient at mean bed particle sizes of 0.241 and 0.219 mm (8.1 < U g /U mf < 8.5). The predictions of this model represent the similar trend variation of average heat transfer coefficient with increasing superficial gas velocity, similar to the works of [16,17,24,34,[58][59][60][61][62][63]. In Figure 9, the red line represents the correlation equation obtained for the heat transfer data using a nonlinear regression in Origin 8 software [64].…”

Section: Discussionsupporting

confidence: 75%

“…On the other hand, the reduction in the value of h avg , is more pronounced at a low vertical pitch of the tube bundle. It is worth mentioning that Equation ( 6) has also been used in other works [24,33].…”

Section: Formulation Of Mechanistic Heat Transfer Modelmentioning

confidence: 99%

“…The obtained heat transfer data indicated that the average heat transfer coefficient increases with the increasing system pressure. Furthermore, Bao et al [24] observed that the fluidization number corresponding to the h max increases as the system pressure increases. Another work [25] developed an empirical correlation for Nusselt number versus Archimedes number and d t /d p for two different horizontal cylinders size on the basis of the measurements made in pilot-scale and laboratory-scale CFB facilities.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

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In the research work, energy transport between a dense fluidized bed and submerged horizontal tube bundle is analyzed in the commercial external heat exchanger (EHE). In order to investigate the heat transfer behavior, the authors carried out eight performance tests in a fluidized bed heat exchange chamber with a cross-section of 2.7 × 2.3 m in depth and width and a height of 1.3 m. The authors have been developing a mechanistic model for the prediction of the average heat transfer coefficient, which includes the effect of the geometric structure of the tube bundle and the location of the heat transfer surface on the heat transfer rate. The computational results depict that the average heat transfer coefficient is essentially affected by superficial gas velocity and suspension density rather than bed particle size. The empirical correlations have been proposed for predicting heat transfer data since the existing literature data is not sufficient for industrial fluidized bed heat exchangers. On the basis of the evaluated operating conditions of an external heat exchanger, the optimal conditions where heat transfer occurs could be deduced. The developed mechanistic heat transfer model is validated by experimental data under the examined conditions.

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Section: Discussionsupporting

confidence: 75%

Section: Formulation Of Mechanistic Heat Transfer Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

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2021

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“…To regulate operating temperatures, facilitate heat exchange, and improve particle mixing, immersed tubes are introduced into the system. The presence of im m ersed tubes in the fluidized bed restricts the size of bubbles, facilitating increased contact between the gas and solid phases and enhancing mixing efficiency [115,116]. However, when dealing with biomass particles, which have non-spherical shapes and a wide size distribution, the incorporation of immersed tubes in a fluidized bed system becomes challenging, especially when using a mixture of biomass and silica sand.…”

Section: Chapter 5 Effect Of Design Parameters On the Hydrodynamics A...mentioning

confidence: 99%

Improvement of hydrodynamics and heat transfer in biomass fluidized bed combustor with immersed tubes using CFD-DEM

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Computational Fluid Dynamics coupled with Discrete Element Method (CFD-DEM) has been extensively utilized for studying hydrodynamics and heat transfer in fluidization processes. This study specifically focuses on improving hydrodynamics and heat transfer in a biomass fluidized bed combustor with immersed tubes. The investigation involves the use of mixed biomass, exploring the effects of biomass types, biomass loading, and blending ratios to propose criteria for selecting suitable biomass fuel for the system. Design parameters related to the immersed tubes, such as the angle between tubes, tube diameters, and distance between tubes, were also considered. A data-driven model was developed based on the CFD-DEM results to predict system parameters. This model offers potential applications in real-time practical engineering without the need for CFD-DEM simulation. The CFD-DEM model was developed for cylindrical biomass and spherical silica sand particles, incorporating an appropriate drag force model. The results showed that the use of mixed biomass with a blending ratio of 1:3 of wood chips to coarse bagasse, with a 5% biomass loading using a ratio of the average equivalent diameter of the biomasses to the equivalent diameter of silica sand of 4.44, was identified as suitable conditions in a general case to obtain the most efficient hydrodynamic results in this study. The criteria for selecting biomass are cylindrical biomass with a greater equivalent diameter than silica sand. Additionally, the proportion of wood chips should be less than that of bagasse. Furthermore, through a 2k factorial design analysis, it was determined that the angle between tubes and tube diameter had the most significant influence on the system behaviors. Moreover, the development of Artificial Neural Network (ANN) models was successful using the simulation dataset, enabling accurate predictions of the mixing index, solid volume fraction, and solid temperature within the system. This study enhances the understanding of hydrodynamics and heat transfer within systems and provides valuable insights for optimizing the design and operation of applications involving mixed biomass and silica sand.

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New Concepts for OCAC in Other Applications

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Oxygen-Carrier-Aided Combustion Technology for Solid-Fuel Conversion in Fluidized Bed

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In this chapter, some new concepts like OCAC with oxy-pressurized fluidized bed oxy-fuel combustion, OCAC coupled with staged conversion of fuel, OCAC application beyond fluidized bed and multi-functional OCAC, are proposed, and the basic principles and technical advantages of these new technologies are introduced in detail. We are confident that there will be more and more beneficial applications of OCAC in the future, We also look forward to providing new ideas for the diversified development of OCAC technology through the proposal of related new concepts.

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An investigation on the heat transfer model for immersed horizontal tube bundles in a pressurized fluidized bed

Cited by 10 publications

References 41 publications

Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

Improvement of hydrodynamics and heat transfer in biomass fluidized bed combustor with immersed tubes using CFD-DEM

New Concepts for OCAC in Other Applications

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