Effective Thermal Conductivity of Rough Spheres Packed Bed

2003 ◽  
Author(s):  
G. Buonanno ◽  
A. Carotenuto ◽  
G. Giovinco ◽  
L. Vanoli
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Matrix Material ◽  
Packed Bed ◽  
Volume Averaging ◽  
Numerical Results ◽  
Solid Particles ◽  
Solid Matrix ◽  
Geometrical Shape

The effective thermal conductivity, ke, rigorously defined on the basis of the local volume averaging method, is an important parameter in porous media. The experimental and numerical results available in literature demonstrate that the kevalue is influenced by several parameters such as thermal and mechanical properties of the multiphase porous medium, phase volumetric fractions, geometrical shape and spatial distribution of the solid matrix and, in particular, contact area between the solid particles. In the present paper, a numerical method to evaluate the effective thermal conductivity from the packing structure of a packed bed of mono-sized spheres is validated through the comparison with experimental data, obtained by the authors from an apparatus designed and build up for this purpose. The effects of the spheroid surface roughness is examined as the applied contact load and the solid matrix material vary. In particular packed beds of steel and aluminum spheroids saturated by a static gas (air) have been studied. Unfortunately, the lack of published results including an accurate measurement of the particle roughness does not allow the authors to compare their numerical results with other researchers’ experimental data.

Evaluation of the Temperature Oscillation Technique to Calculate Thermal Conductivity of Water and Systematic Measurement of the Thermal Conductivity of Aluminum Oxide – Water Nanofluid

2004 ◽  
Author(s):  
P. Bhattacharya ◽  
S. Nara ◽  
P. Vijayan ◽  
T. Tang ◽  
W. Lai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Oxide ◽  
Effective Thermal Conductivity ◽  
Base Fluid ◽  
Suspended Solid ◽  
Temperature Oscillation ◽  
Solid Particles ◽  
Systematic Measurement ◽  
Experimental Setup ◽  
Suspended Solid Particles

A nanofluid is a fluid containing suspended solid particles, with sizes of the order of nanometers. The nanofluids are better conductors of heat than the base fluid itself. Therefore it is of interest to measure the effective thermal conductivity of such a nanofluid. We use temperature oscillation technique to measure the thermal conductivity of the nanofluid. However, first we evaluate the temperature oscillation technique as a tool to measure thermal conductivity of water. Then we validate our experimental setup by measuring the thermal conductivity of the aluminum oxide-water nanofluid and comparing our results with previously published work. Finally, we do a systematic series of measurements of the thermal conductivities of aluminum oxide-water nanofluids at various temperatures and explain the reasons behind the dependence of the enhancement in thermal conductivity of the nanofluid on temperature.

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

scholarly journals Measurement of Thermal Conductivity along the Radial Direction in a Vertical Cylindrical Packed Bed

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Swaren Bedarkar ◽  
Nurni Neelakantan Viswanathan ◽  
Nidambur Bharatha Ballal
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Crucial Role ◽  
Iron Ore ◽  
Radial Direction ◽  
Thermal Response ◽  
Packed Bed ◽  
Lumped Parameter ◽  
Scientists And Engineers

Heat transfer in packed beds and their thermal response have been of great interest for scientists and engineers for the last several years, since they play a crucial role in determining design and operation of reactors. Heat transfer of a packed bed is characterised through lumped parameter, namely, effective thermal conductivity. In the present studies, experiments were performed to investigate the thermal conductivity of a packed bed in radial direction. The packed bed was formed using iron ore particles. To determine the effective thermal conductivity a new transient methodology is proposed. The results obtained were compared with the models proposed by ZBS and Kunii and Smith.

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.

Beating the Thermal Conductivity of Air Using Packed Nanoparticle Bed

2006 ◽  
Author(s):  
Ravi Prasher
Keyword(s):  
Thermal Conductivity ◽  
Surface Energy ◽  
Effective Thermal Conductivity ◽  
Free Path ◽  
Packed Bed ◽  
Mean Free Path ◽  
Low Thermal Conductivity ◽  
Pressure Surface

Thermal conductivity of packed bed of nanoparticles is calculated in this paper. Results show that effective thermal conductivity of nanoparticle bed can be very low. Thermal conductivity of the nanoparticle bed can be smaller than the thermal conductivity of air. Thermal conductivity depends on pressure, surface energy of the nanoparticle, and phonon mean free path.

A Simplified Model for Effective Thermal Conductivity of Highly Porous Ceramic Fiber Insulation

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Nicholas P. G. Lumley ◽  
Emory Ford ◽  
Eric Minford ◽  
Jason M. Porter
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Effective Thermal Conductivity ◽  
Research Effort ◽  
Porous Ceramic ◽  
Ceramic Fiber ◽  
Chemical Process Industry ◽  
Thermophysical Model ◽  
Highly Porous

Highly porous ceramic fiber insulations are beginning to be considered as a replacement for firebrick insulations in high temperature, high pressure applications by the chemical process industry. However, the implementation of such materials has been impeded by a lack of experimental data and predictive models, especially at high gas pressure. The goal of this work was to develop a general, applied thermophysical model to predict effective thermal conductivity, keff, of porous ceramic fiber insulation materials and to determine the temperature, pressure, and gas conditions under which natural convection is a possible mode of heat transfer. A model was developed which calculates keff as the sum of conduction, convection, and radiation partial conductivities. The model was validated using available experimental data, including laboratory measurements made by this research effort. Overall, it was concluded that natural convection is indeed possible for the most porous insulations at pressures exceeding 10 atm. Furthermore, keff for some example insulations was determined as a function of temperature, pressure, and gas environment.

Sign in / Sign up

Export Citation Format

Share Document