Genetic Programming based Drag Model with Improved Prediction Accuracy for Fluidization Systems

2017 ◽  
Vol 15 (2) ◽  
Author(s):  
R. R. Sonolikar ◽  
M. P. Patil ◽  
R. B. Mankar ◽  
S. S. Tambe ◽  
B. D. Kulkarni
Keyword(s):  
Pressure Drop ◽  
Genetic Programming ◽  
Drag Coefficient ◽  
Prediction Accuracy ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Superior Performance ◽  
Momentum Exchange ◽  
Drag Model ◽  
Parameter Ranges

Abstract The drag coefficient plays a vital role in the modeling of gas-solid flows. Its knowledge is essential for understanding the momentum exchange between the gas and solid phases of a fluidization system, and correctly predicting the related hydrodynamics. There exists a number of models for predicting the magnitude of the drag coefficient. However, their major limitation is that they predict widely differing drag coefficient values over same parameter ranges. The parameter ranges over which models possess a good drag prediction accuracy are also not specified explicitly. Accordingly, the present investigation employs Geldart’s group B particles fluidization data from various studies covering wide ranges of Re and εs to propose a new unified drag coefficient model. A novel artificial intelligence based formalism namely genetic programming (GP) has been used to obtain this model. It is developed using the pressure drop approach, and its performance has been assessed rigorously for predicting the bed height, pressure drop, and solid volume fraction at different magnitudes of Reynolds number, by simulating a 3D bubbling fluidized bed. The new drag model has been found to possess better prediction accuracy and applicability over a much wider range of Re and εs than a number of existing models. Owing to the superior performance of the new drag model, it has a potential to gainfully replace the existing drag models in predicting the hydrodynamic behavior of fluidized beds.

Three-Dimensional Simulation of Gas-Solid Flow in the Biomass Circulating Fluidized Bed Gasifier’s Riser

2011 ◽  
Vol 383-390 ◽  
pp. 6537-6542
Author(s):  
Wen Yi Chen ◽  
Xin Liu ◽  
Xiao Xu Fan ◽  
Lei Zhe Chu ◽  
Yi Mei Yang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Mutual Influence ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Momentum Exchange ◽  
Solid Flow ◽  
Radial Profiles

Using the Gidaspow model as the momentum exchange coefficient to take a full-loop simulation of miniature circulating fluidized bed gasifier (CFBG) in the lab, and taking mutual influence of different parts in consideration, it focus on the gas-solid flow structure in the riser in this paper. The heterogeneous behavior in the CFBG riser and the radial profiles of solid volume fraction under different solid inventories in simulation are showed in this paper as a replenishment of certain data which are hard to measure in experiments. The results showed it can’t form an obvious core-annulus flow because of the riser’s high height-diameter ratio and the big refeed line diameter. There are clusters growing and dissipation in a short time. A turning point of pressure drop may be seem as a separation of dense area and dilute area.The three-dimensional (3D) simulation revealed the solid flux and the pressure drop agree with the experimental data.

scholarly journals Magneto-Hybrid Nanofluids Flow via Mixed Convection past a Radiative Circular Cylinder

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
E. R. EL-Zahar ◽  
A. M. Rashad ◽  
W. Saad ◽  
L. F. Seddek
Keyword(s):  
Circular Cylinder ◽  
Drag Coefficient ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convective Boundary Condition ◽  
Hybrid Nanofluid ◽  
Current Analysis ◽  
Convective Boundary ◽  
Fundamental Parameters ◽  
Grid Points

Abstract The goal of the current analysis is to scrutinize the magneto-mixed convective flow of aqueous-based hybrid-nanofluid comprising Alumina and Copper nanoparticles across a horizontal circular cylinder with convective boundary condition. The energy equation is modelled by interpolating the non-linear radiation phenomenon with the assisting and opposing flows. The original equations describing the magneto-hybrid nanofluid motion and energy are converted into non-dimensional equations and solved numerically using a new hybrid linearization-Chebyshev spectral method (HLCSM). HLCSM is a high order spectral semi-analytical numerical method that results in an analytical solution in η-direction and thereby the solution is valid in overall the η-domain, not only at the grid points. The impacts of diverse parameters on the allied apportionment are inspected, and the fallouts are described graphically in the investigation. The physical quantities of interest containing the drag coefficient and the heat transfer rate are predestined versus fundamental parameters, and their outcomes are elucidated. It is witnessed that both drag coefficient and Nusselt number have greater magnitude for Cu-water followed by hybrid nanofluid and Al2O3-water. Moreover, the value of the drag coefficient declines versus the enlarged solid volume fraction. To emphasize the originality of the current analysis, the outcomes are compared with quoted works, and excellent accord is achieved in this consideration.

scholarly journals Computational Analysis of the Hydrodynamic Behavior for Different Air Distributor Designs of Fluidized Bed Gasifier

2021 ◽  
Vol 9 ◽  
Author(s):  
Naveed Raza ◽  
Muhammad Ahsan ◽  
Muhammad Taqi Mehran ◽  
Salman Raza Naqvi ◽  
Iftikhar Ahmad
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Perforated Plate ◽  
Column Height ◽  
Thermochemical Conversion ◽  
Open Area ◽  
Slotted Plate ◽  
Distributor Plate

Fluidized bed gasification has proven to be an appropriate technique for converting various biomass feedstocks into helpful energy. Air distributor plate design is one of the critical factors affecting the thermochemical conversion performance of fluidized bed gasifiers. The present study is proposed to investigate the mixing pattern and pressure drop across different configurations of air distributors using a two-fluid model (TFM) of finite volume method-based solver ANSYS FLUENT. The pressure drop across the bed and mixing pattern have been investigated through qualitative and quantitative analysis of CFD results using three diverse distributor plate designs: perforated plate, 90° slotted plate, and 45° swirling slotted plate. The pressure drop by employing the perforated distributor plate reveals the highest pressure drop due to the smallest open area ratio. However, the pressure drop in the case of 90° slotted plate is found to be 7% and 4% lesser than perforated and 45° slotted plate respectively due to a smaller velocity head developed through the wider open area of the straight slotted plates. The distributor design configuration having a 45° slotted plate exhibits considerable pressure drop compared to the 90° slotted plate due to the longer path length of the slot. Numerical pressure drop results across the bed with different types of distributor plates prove reasonable agreement with the experimental results available in the literature. Mixing behavior in perforated distributor plates exhibits lower portion solid volume fraction of around 0.58. However, it falls rapidly as go up the riser (7.7% of column height); 90° slotted plate shows bottom region solid volume fraction of around 0.5. In addition, it exhibits an even broader range of sand volume fraction and column height (13.46% of column height). Finally, the 45° distributor plate reveals the highest range of volume fraction through the riser height (17.3% of column height), indicating the better mixing characteristics of the fluidized zone.

Computational Fluid Dynamics Studies of Gas-Solid Flows in a Horizontal Pipe, Subjected to an Adiabatic Wall, Using a Variable Gas Properties Eulerian Model

2019 ◽  
Vol 14 (3) ◽  
Author(s):  
Brundaban Patro ◽  
K. Kiran Kumar ◽  
D. Jaya Krishna
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Solid Loading ◽  
Eulerian Model ◽  
Adiabatic Wall ◽  
Horizontal Pipe ◽  
Loading Ratio ◽  
Gas Properties

Abstract In the present paper, a variable gas properties Eulerian model is employed to model the gas-solid heat transfer in a three-dimensional horizontal pipe, subjected to an adiabatic wall. The numerical model has been validated with the benchmark experimental data and other theoretical results available in the literature, and found satisfactory agreements. Moreover, the numerical heat transfer results considering the variable gas properties (i. e. density, dynamic viscosity, thermal conductivity, and specific heat) and constant gas properties are compared. It is noticed that the variable gas properties significantly affect the heat transfer, when compared to the constant gas properties. Therefore, the consideration of constant gas properties for the prediction of heat transfer may not be suitable in gas-solid flows, subjected to an adiabatic wall. Moreover, the temperature profiles, solid volume fraction profiles, and gas-solid Nusselt number are discussed. Finally, the pressure drop prediction with respect to the solid loading ratio is studied, and found that the pressure drop slightly decreases with increasing the solid loading ratio.

scholarly journals Numerical analysis of mixed convection characteristics inside a ventilated cavity including the effects of nanoparticle suspensions

2017 ◽  
Vol 21 (5) ◽  
pp. 2205-2215
Author(s):  
Ehsan Sourtiji ◽  
Mofid Gorji-Bandpy
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Solid Volume Fraction ◽  
Maximum Heat ◽  
Outlet Port ◽  
Maximum Heat Transfer

A numerical study of mixed convection flow and heat transfer inside a square cavity with inlet and outlet ports is performed. The position of the inlet port is fixed but the location of the outlet port is varied along the four walls of the cavity to investigate the best position corresponding to maximum heat transfer rate and minimum pressure drop in the cavity. It is seen that the overall Nusselt number and pressure drop coefficient vary drastically depending on the Reynolds and Richardson numbers and the position of the outlet port. As the Richardson number increases, the overall Nusselt number generally rises for all cases investigated. It is deduced that placing the outlet port on the right side of the top wall is the best position that leads to the greatest overall Nusselt number and lower pressure drop coefficient. Finally, the effects of nanoparticles on heat transfer are investigated for the best position of the outlet port. It is found that an enhancement of heat transfer and pressure drop is seen in the presence of nanoparticles and augments with solid volume fraction of the nanofluid. It is also observed that the effects of nanoparticles on heat transfer at low Richardson numbers is more than that of high Richardson numbers. <br><br><font color="red"><b> This article has been retracted. Link to the retraction <u><a href="http://dx.doi.org/10.2298/TSCI190625278E">10.2298/TSCI190625278E</a><u></b></font>

scholarly journals In Situ Determination of Solid Fraction from the Measured Hydrate Slurry Flow Rate and Pressure Drop across Orifice

2020 ◽  
Vol 10 (20) ◽  
pp. 7035
Author(s):  
Muhammad Usman ◽  
Zabdur Rehman ◽  
Kwanjae Seong ◽  
Myung Ho Song
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Volume Fraction ◽  
Hydration Number ◽  
Solid Volume Fraction ◽  
Solution Procedure ◽  
Pharmaceutical Chemical ◽  
Flow Loop ◽  
Two Phase

Two-phase flow is encountered in various engineering areas, including the pharmaceutical, chemical, and food industries, desalination facilities, and thermal energy storage systems. Cost-effective and non-invasive monitoring of the solid volume fraction, which governs the thermos-physical properties of two-phase medium, is important for flow assurance. The flow loop having an inner diameter of 21.5 mm and length of about 12.2 m was equipped with square-edged orifice and slash plate pump. Tetrafluroethane (R134a) hydrate slurry of the specified solid volume fraction could be formed within the flow loop by removing an appropriate amount of water, and simultaneously injecting the pertinent amount of R134a while chilled at 275 K. The uncertainty in the thus-obtained solid volume fraction was smaller than 9%, with the largest contribution originating from the uncertain hydration number. The near power-law relationship between the orifice pressure loss coefficient and Metzner–Reed Reynolds number was recognized. However, the nonlinear nature of the Reynolds number with respect to the solid volume fraction inevitably makes the solution procedure iterative. The short span pressure differences across the orifice were regressed to yield empirical correlation, with which the solid volume fraction of R134a slurry could be determined from the measured pressure drop across the orifice and the flow rate. The uncertainty was less than 12% of the thus determined solid volume fraction.

scholarly journals MATHEMATICAL OPTIMIZATION: APPLICATION TO THE DESIGN OF OPTIMAL MICRO-CHANNEL HEAT SINKS

2009 ◽  
Vol 8 (1) ◽  
pp. 58 ◽  
Author(s):  
F. U. Ighalo ◽  
T. Bello-Ochende ◽  
J. P. Meyer
Keyword(s):  
Pressure Drop ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Thermal Conductance ◽  
Mathematical Optimization ◽  
Heat Sinks ◽  
Dynamics Simulation ◽  
Micro Channel ◽  
Dimensionless Pressure ◽  
Gradient Based

This paper documents the geometrical optimization of a micro-channel heatsink embedded inside a highly conductive solid, with the intent of developing optimal solutions for thermal management in microelectronic devices. The objective is to minimize the peak wall temperature of the heat sink subject to various constraints such as manufacturing restraints, fixed pressure drop and total fixed volume. A gradient based multi-variable optimization algorithm is used as it adequately handles the numerical objective function obtained from the computational fluid dynamics simulation. Optimal geometric parameters defining the micro-channel were obtained for a pressure drop ranging from 10 kPa to 60 kPa corresponding to a dimensionless pressure drop of 6.5 × 107 to 4 × 108 for fixed volumes ranging from 0.7 mm3 of 0.9 mm3. The effect of pressure drop on the aspect ratio, solid volume fraction, channel hydraulic diameter and the minimized peak temperature are reported. Results also show that as the dimensionless pressure drop increases the maximised dimensionless global thermal conductance also increases. These results are in agreement with previous work found in literature.

Modeling Flows in Porous Media Using Immersed Boundary Based Lattice Boltzman Method

2012 ◽  
Author(s):  
Zhi-Gang Feng ◽  
Maria Andersson
Keyword(s):  
Porous Media ◽  
Drag Coefficient ◽  
Solid Fraction ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Immersed Boundary ◽  
Face Centered Cubic ◽  
Flows In Porous Media ◽  
Random Arrays ◽  
Arrays Of Spheres

Flows in porous media of fixed arrays of spheres have been studied numerically in the present work. The flow velocity and pressure fields are solved by the lattice Boltzmann method; the no-slip boundary condition at the solid-fluid interface is enforced by the immersed boundary method with the direct forcing scheme. This numerical method, which we call Proteus and initially was developed for simulations of particles in motion, has been extended to study flow over fixed arrays of spheres. The method is validated by comparing the simulated drag coefficient on a single sphere to the one obtained using an empirical drag law. The present method is then applied to obtain the dimensionless drag force on a sphere in both ordered face-centered cubic arrays of spheres and random arrays of spheres. Our results at low solid volume fraction for ordered arrays of spheres show good agreement with the theoretical solution of Hasimoto (1959). A correlation on the drag coefficient at solid fraction ranging from 0 to 0.66 has been derived based on our simulation results. This will help improve the modeling of particulate flows. The case of flow over random arrays of spheres at the solid fraction of 0.345 and flow Reynolds numbers up to 57 has also been studied. Our results agree well with the Ergun’s empirical correlation.

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