Experimental and Theoretical Modeling of the Effective Thermal Conductivity of Rough Steel Spheroid Packed Beds

2003 ◽  
Vol 125 (4) ◽  
pp. 693-702 ◽  
Author(s):  
G. Buonanno ◽  
A. Carotenuto ◽  
G. Giovinco ◽  
N. Massarotti
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Solid Mechanics ◽  
Packed Bed ◽  
Elementary Cell ◽  
Upper And Lower Bounds ◽  
Packed Beds ◽  
The Finite Element Method ◽  
Two Phase ◽  
Experimental Apparatus

The upper and lower bounds of the effective thermal conductivity of packed beds of rough spheres are evaluated using the theoretical approach of the elementary cell for two-phase systems. The solid mechanics and thermal problems are solved and the effects of roughness and packed bed structures are also examined. The numerical solution of the thermal conduction problem through the periodic regular arrangement of steel spheroids in air is determined using the Finite Element Method. The numerical results are compared with those obtained from an experimental apparatus designed and built for this purpose.

Bounding of Effective Thermal Conductivity of Two-Phase Materials

2013 ◽  
Vol 336 ◽  
pp. 185-193 ◽  
Author(s):  
Ramvir Singh ◽  
Sajjan Kumar ◽  
Radhey Shyam Beniwal
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Lower Bounds ◽  
Random Distribution ◽  
Volume Fraction ◽  
Correction Term ◽  
Upper And Lower Bounds ◽  
Two Phase ◽  
New Approach ◽  
Phase Systems

In this paper, we propose a new approach to obtain the upper and lower bounds for the effective thermal conductivity of real two-phase systems. The developed expressions are based upon the series and parallel combination of resistors. To incorporate the effect of random distribution of inclusions in the continuous matrix as well as the wide difference in the thermal conductivity of the constituents, a non-linear second-order correction term is introduced. This correction term is used to replace the volume fraction of inclusions in parallel and perpenducular thermal conductivity equations. The obtained upper and lower bounds are then compared with the Hashin and Shtrikman bounds [ and it is found that the modified bounds are narrower as compared to other previously developed bounds for effective thermal conductivity. The modified upper and lower bounds are then used in Chaudhary and Bhandaris model to predict the effective thermal conductivity of real two-phase materials. The predictions of the effective thermal conductivity using the modified relations match well with the experimental results.

Experimental Analysis of Heat Transfer inside Packed Beds of Soybean Seeds

2012 ◽  
Vol 727-728 ◽  
pp. 1818-1823
Author(s):  
G.F.M.V. Souza ◽  
R. Béttega ◽  
R.F. Miranda ◽  
O.S.H. Mendoza ◽  
M.A.S. Barrozo
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Fluid Dynamic ◽  
Fixed Bed ◽  
Packed Bed ◽  
Soybean Seeds ◽  
Packed Beds ◽  
Flow Conditions ◽  
Separation Systems

Several applications in chemical industry use randomly packed bed of particles, such as particulate separation systems, chemical reactors or fixed bed drying. Fluid dynamic behavior, heat and mass transfer, in addition to structural properties of the bed are fundamental issues to design of these processes. Several studies about heat transfer in packed beds aiming drying application have been performed in order to contribute with the process. Seeds drying temperature is especially important for the seeds quality indices and must be carefully controlled in drying process. In this paper temperature profiles experimentally obtained in a packed bed composed by soybean seeds are presented and discussed. Axial profiles of temperature were applied for obtaining effective thermal conductivity following previous studies from literature. The results indicate that thermal homogeneity can be achieved inside the bed for controlled air flow conditions. Axial effective thermal conductivity presented results in agreement with previous studies from literature.

A Boundary Element Method for Evaluation of the Effective Thermal Conductivity of Packed Beds

2006 ◽  
Vol 129 (3) ◽  
pp. 363-371 ◽  
Author(s):  
Jianhua Zhou ◽  
Aibing Yu ◽  
Yuwen Zhang
Keyword(s):  
Thermal Conductivity ◽  
Boundary Element ◽  
Effective Thermal Conductivity ◽  
Fluid Phase ◽  
Packed Bed ◽  
Element Model ◽  
Solid Surfaces ◽  
Packed Beds ◽  
Wide Range ◽  
Radiation Heat Exchange

The problem of evaluating the effective thermal conductivity of random packed beds is of great interest to a wide-range of engineers and scientists. This study presents a boundary element model (BEM) for the prediction of the effective thermal conductivity of a two-dimensional packed bed. The model accounts for four heat transfer mechanisms: (1) conduction through the solid; (2) conduction through the contact area between particles; (3) radiation between solid surfaces; and (4) conduction through the fluid phase. The radiation heat exchange between solid surfaces is simulated by the net-radiation method. Two regular packing configurations, square array and hexagonal array, are chosen as illustrative examples. The comparison between the results obtained by the present model and the existing predictions are made and the agreement is very good. The proposed BEM model provides a new tool for evaluating the effective thermal conductivity of the packed beds.

The Effect of Turbulence on Momentum and Heat Transport in Packed Beds with Low Tube to Particle Diameter Ratio

2018 ◽  
Vol 16 (11) ◽  
Author(s):  
F. I. Molina-Herrera ◽  
C. O. Castillo-Araiza ◽  
H. Jiménez-Islas ◽  
F. López-Isunza
Keyword(s):  
Thermal Conductivity ◽  
Heat Transport ◽  
Mass Flux ◽  
Flow Model ◽  
Particle Diameter ◽  
Packed Bed ◽  
Diameter Ratio ◽  
Packed Beds ◽  
Measured Temperature ◽  
Orthogonal Collocation

Abstract This is a theoretical study about the influence of turbulence on momentum and heat transport in a packed-bed with low tube to particle diameter ratio. The hydrodynamics is given here by the time-averaged Navier-Stokes equations including Darcy and Forchheimer terms, plus a κ-ε two-equation model to describe a 2D pseudo-homogeneous medium. For comparison, an equivalent conventional flow model has also been tested. Both models are coupled to a heat transport equation and they are solved using spatial discretization with orthogonal collocation, while the time derivative is discretized by an implicit Euler scheme. We compared the prediction of radial and axial temperature observations from a packed-bed at particle Reynolds numbers (Rep) of 630, 767, and 1000. The conventional flow model uses effective heat transport parameters: wall heat transfer coefficient (hw) and thermal conductivity (keff), whereas the turbulent flow model includes a turbulent thermal conductivity (kt), estimating hw via least-squares with Levenberg-Marquardt method. Although predictions of axial and radial measured temperature profiles with both models show small differences, the calculated radial profiles of the axial velocity component are very different. We demonstrate that the model that includes turbulence compares well with mass flux measurements at the packed-bed inlet, yielding an error of 0.77 % in mass flux balance at Rep = 630. We suggest that this approach can be used efficiently for the hydrodynamics characterization and design and scale-up of packed beds with low tube to particle diameter ratio in several industrial applications.

scholarly journals The effect of particle shape on the packed bed effective thermal conductivity based on DEM with polyhedral particles on the GPU

2020 ◽  
Vol 219 ◽  
pp. 115584 ◽  
Author(s):  
Nicolin Govender ◽  
Paul W. Cleary ◽  
Mehran Kiani-Oshtorjani ◽  
Daniel N. Wilke ◽  
Chuan-Yu Wu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Particle Shape ◽  
Packed Bed ◽  
Polyhedral Particles
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