Unsteady Heat Conduction in Granular Materials

2000 ◽  
Vol 627 ◽  
Author(s):  
Watson L. Vargas ◽  
Joseph J. McCarthy
Keyword(s):  
Heat Conduction ◽  
Granular Materials ◽  
Thermal Response ◽  
Transient Heat Conduction ◽  
Packed Bed ◽  
Industrial Applications ◽  
Multiphase Reactors ◽  
Wide Range ◽  
Unsteady Heat Conduction ◽  
Insight Into

ABSTRACTHeat transfer in granular materials impacts a variety of industrial applications, such as calcination, drying kilns, packed bed and multiphase reactors, etc. and may yield insight into the thermal response of some porous materials (in combustion synthesis or sintering, for example). In a dense bed of granular material, conduction occurs almost exclusively through the particle-particle contacts over a wide range of conditions. We have developed a novel Thermal Particle Dynamics (TPD) Simulation technique which incorporates both contact mechanics and contact conductance theories in order to model the dynamics of flow and heat conduction through granular materials. This model is uniquely suited to studying the effects of microstructure and flow on the dynamics of heat conduction in particulate materials. In this paper, we present experimental as well as numerical results of transient heat conduction through a bed of cylinders.

TRANSIENT HEAT CONDUCTION FROM SPHEROIDS

2014 ◽  
Vol 38 (3) ◽  
pp. 373-389 ◽  
Author(s):  
Rajai Alassar ◽  
Mohammed Abushosha ◽  
Mohammed El-Gebeily
Keyword(s):  
Heat Conduction ◽  
Transient Heat Conduction ◽  
Dimensionless Temperature ◽  
Legendre Functions ◽  
Axis Ratio ◽  
Spheroidal Wave Functions ◽  
Implicit Finite Difference Scheme ◽  
Unbounded Medium ◽  
Unsteady Heat Conduction ◽  
Limiting Case

We study the unsteady heat conduction from a spheroid (prolate or oblate) initially heated and then left to cool in an unbounded medium of constant temperature. We present two solutions of the problem. The first makes use of the spheroidal wave functions as basis. The second, which is numerical, is obtained by expanding the dimensionless temperature in terms of Legendre functions and then solving the resulting set of differential equations in the radial direction using an implicit finite difference scheme. The two solutions are further verified by comparing them to the limiting case of a sphere. We study the effect of the axis ratio on the time development of temperature inside the spheroid and the heat flux across the surface.

Nonequilibrium Thermal Response of Porous Media in Unsteady Heat Conduction With Sinusoidally Changing Boundary Temperature

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Huijin Xu ◽  
Liang Gong ◽  
Changying Zhao ◽  
Ying Yin
Keyword(s):  
Porous Media ◽  
Heat Conduction ◽  
Temperature Difference ◽  
Thermal Response ◽  
Porous Solid ◽  
Maximum Temperature ◽  
Maximum Temperature Difference ◽  
Boundary Temperature ◽  
Thermal Disturbance ◽  
Unsteady Heat Conduction

The thermal response of porous foam filled with a solid material was theoretically investigated under unsteady heat conduction with a sinusoidally changing boundary temperature. The local thermal nonequilibrium (LTNE) effect between the porous foam and the infill was obvious, and the two-equation model is employed for the unsteady heat conduction in porous-solid system. The temperature difference, which was defined as the time average of the absolute value of the difference between the temperatures of the porous solid and the infill, was proposed for quantitatively describing the LTNE effect in porous media. The LTNE phenomenon for unsteady heat conduction in porous media is influenced by the fluctuation period of the thermal boundary, foam morphology, and the thermal diffusivities of the porous solid and the infill. The LTNE effect of unsteady porous-media heat conduction was evident in the region near the thermal disturbance boundary. The maximum temperature difference was found on the curve of temperature difference versus fluctuation period, which means that the thermal response characteristics of porous composites resonate with periodically changing thermal disturbance. The fluctuation period corresponding to the maximum temperature difference has positive correlations with thermal diffusion resistance for unsteady porous-media heat conduction.

Finite element implementation of the eigenfunction series solution for transient heat conduction problems with low Biot number

2011 ◽  
Vol 226 (6) ◽  
pp. 1579-1588 ◽  
Author(s):  
A Al-Shabibi ◽  
J R Barber
Keyword(s):  
Finite Element ◽  
Heat Conduction ◽  
Heat Loss ◽  
Biot Number ◽  
Transient Heat Conduction ◽  
Attractive Alternative ◽  
Small Subset ◽  
Element Discretization ◽  
Transient Heat Conduction Problem ◽  
Wide Range

Analytical solutions to transient heat conduction problems are often obtained by superposition of a particular solution (often the steady-state solution) and an eigenfunction series, representing the terms that decay exponentially with time. Here, a finite element realization of this method is presented in which conventional finite element discretization is used for the spatial distribution of temperature and analytical methods for the time dependence. This leads to a linear eigenvalue problem whose solution then enables a general numerical model of the transient system to be created. The method is an attractive alternative to conventional time-marching schemes, particularly in cases where it is desired to explore the effect of a wide range of operating parameters. The method can be applied to any transient heat conduction problem, but particular attention is paid to the case where the Biot number is small compared with unity and where the evolution of the system is very close to that with zero heat loss from the exposed surfaces. This situation arises commonly in machines such as brakes and clutches which experience occasional short periods of intense heating. Numerical examples show that with typical parameter values, the simpler zero heat loss solution provides very good accuracy. One also shows that good approximations can be achieved using a relatively small subset of the eigenvectors of the problem.

Transient Heat Conduction in On-Chip Interconnects Using Proper Orthogonal Decomposition Method

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Banafsheh Barabadi ◽  
Satish Kumar ◽  
Yogendra K. Joshi
Keyword(s):  
Heat Conduction ◽  
Proper Orthogonal Decomposition ◽  
Thermal Response ◽  
Transient Heat Conduction ◽  
Device Fabrication ◽  
Orthogonal Decomposition ◽  
Galerkin Projection ◽  
Full Field ◽  
On Chip ◽  
Proper Orthogonal

A major challenge in maintaining quality and reliability in today's microelectronics chips comes from the ever increasing levels of integration in the device fabrication, as well as from the high current densities. Transient Joule heating in the on-chip interconnect metal lines with characteristic sizes of tens of nanometer, can lead to thermomechanical fatigue and failure due to the thermal expansion coefficient mismatch between different materials. Full-field simulations of nearly a billion interconnects in a modern microprocessor are infeasible due to the grid size requirements. To prevent premature device failures, a rapid predictive capability for the thermal response of on-chip interconnects is essential. This work develops a two-dimensional (2D) transient heat conduction framework to analyze inhomogeneous domains, using a reduced-order modeling approach based on proper orthogonal decomposition (POD) and Galerkin projection. POD modes are generated by using a representative step function as the heat source. The model rapidly predicted the transient thermal behavior of the system for several cases, without generating any new observations, and using just a few POD modes.

New Insight into Old Bacillus Lipase: Solvent Stable Mesophilic Lipase Demonstrating Enzyme Activity towards Cold

2015 ◽  
Vol 25 (5) ◽  
pp. 340-348 ◽  
Author(s):  
Jyoti Khurana ◽  
Rakesh Kumar ◽  
Arbind Kumar ◽  
Kashmir Singh ◽  
Ranvir Singh ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Molecular Mass ◽  
Industrial Applications ◽  
Maximum Activity ◽  
Lipase Gene ◽  
Reading Frame ◽  
Wide Range ◽  
Cold Active ◽  
Solvent Stable ◽  
Insight Into

<b><i>Background:</i></b><i>Bacillus</i> lipases are grouped in subfamily 1.4, which are the smallest known lipases having a molecular mass of 19.6 kDa. Lipases active in a wide range of temperatures, specifically at low temperatures, have an advantage under low water conditions for industrial application. <b><i>Methods:</i></b> The lipase gene was cloned and expressed in <i>Escherichia coli</i>. The protein was purified and biochemically characterized in detail. <b><i>Results:</i></b> A lipase gene was cloned from a mesophilic <i>Bacillus</i> isolate. Sequence analysis revealed an open reading frame of 633 bp in length. The predicted molecular mass of protein was 22.6 kDa. The purified enzyme displayed optimal activity at 35°C and pH 8.0. Interestingly, this mesophilic enzyme was also cold active showing retention of 75 and 55% relative enzyme activity at 20 and 10°C, respectively. The purified lipase was stable in various organic solvents (50% v/v) and ionic liquids (5% v/v). The enzyme displayed maximum activity with paranitrophenyl laurate (C<sub>12</sub>). k<sub>cat</sub>/K<sub>m</sub> values for the purified lipase were calculated to be 5.8 ± 0.6 × 10<sup>-6</sup>. <b><i>Conclusions:</i></b> The lipase showed tolerance to various solvents as well as activity at low temperature. Therefore, this lipase might be of great potential to be employed in various industrial applications.

Non-Ideal Flow in Liquid-Solid Fixed Beds of Irregular-Shaped Particles: A Critical Review

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Vassilis J Inglezakis
Keyword(s):  
Packed Bed ◽  
Industrial Applications ◽  
Packing Material ◽  
Dispersion Coefficients ◽  
Packed Bed Reactors ◽  
Ideal Flow ◽  
Current Review ◽  
Time Dispersion ◽  
Wide Range ◽  
Fixed Beds

Available data and correlations for non ideal flow in liquid-solid fixed beds are summarized and reviewed with focus on irregular-shaped particles as packing material. The reason is that in many industrial applications (adsorption, ion exchange, catalysis, etc.) the particles used are of irregular shape while the vast majority of available data on dispersion and non ideal flow is on non-porous spherical or other ordered-shaped particles (saddles, rings, cylinders, tablets, etc.). In the same time, dispersion plays an important part, for example, in reactant and product transport in packed bed reactors, in adsorption, leaching, etc. In the present review all available correlations and data for liquid-solid fixed beds packed with irregular-shaped particles are collected for the prediction of the dispersion coefficients over a wide range of practical values particle Reynolds number. For the current review, 198 experimental points used and 6 Ped – Rep correlations are presented, all derived for irregular-shaped particles.

A Meshfree Approach for Transient Heat Conduction Analysis of Nonlinear Functionally Graded Materials

2017 ◽  
Vol 15 (02) ◽  
pp. 1850007 ◽  
Author(s):  
Mas Irfan P. Hidayat ◽  
Bambang Ariwahjoedi ◽  
Setyamartana Parman ◽  
Sonny Irawan
Keyword(s):  
Heat Conduction ◽  
Functionally Graded Materials ◽  
Transient Heat Conduction ◽  
Functionally Graded ◽  
Basis Functions ◽  
Spline Collocation ◽  
Graded Materials ◽  
B Spline ◽  
Wide Range ◽  
Spline Basis

In this paper, an alternative meshfree approach is presented for transient heat conduction analysis of nonlinear functionally graded materials (FGMs). The main idea behind the introduced approach is to use collocation in local domains containing of sets of regular or scattered nodes and approximating the solution by B-spline basis functions. It combines the favorable properties of B-spline basis functions in having arbitrary degree for better resolution of solution, partition of unity and the Kronecker delta properties with low computational effort of collocation. The method is called as local B-spline collocation method. It is mathematically simple, efficient to program and truly meshless. The method is applied for analyzing transient heat conduction in a wide range of FGMs with various material gradation models, in both 2D and 3D domains. The results obtained agree well with those computed by analytical solution and other well-known methods, confirming the suitability and efficacy of the presented scheme.

Sentence-Based Experience Logging in New Hearing Aid Users

2020 ◽  
Vol 29 (3S) ◽  
pp. 631-637
Author(s):  
Katja Lund ◽  
Rodrigo Ordoñez ◽  
Jens Bo Nielsen ◽  
Dorte Hammershøi
Keyword(s):  
Hearing Aid ◽  
Patient Experiences ◽  
Online Tool ◽  
Rehabilitation Process ◽  
Hearing Rehabilitation ◽  
Clinical Observations ◽  
Hearing Aid Use ◽  
Wide Range ◽  
Insight Into ◽  
Shed Light

Purpose The aim of this study was to develop a tool to gain insight into the daily experiences of new hearing aid users and to shed light on aspects of aided performance that may not be unveiled through standard questionnaires. Method The tool is developed based on clinical observations, patient experiences, expert involvement, and existing validated hearing rehabilitation questionnaires. Results An online tool for collecting data related to hearing aid use was developed. The tool is based on 453 prefabricated sentences representing experiences within 13 categories related to hearing aid use. Conclusions The tool has the potential to reflect a wide range of individual experiences with hearing aid use, including auditory and nonauditory aspects. These experiences may hold important knowledge for both the patient and the professional in the hearing rehabilitation process.

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