Current Problems of Heat and Mass Transfer in the Cryopreservation of Biomaterials: Interactions among Coupled Multiscale Transport Processes

1998 ◽  
Vol 25 (1-3) ◽  
pp. 295-304
Author(s):  
Kenneth R. Diller
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Transport Processes ◽  
Multiscale Transport

The Kinetics Effect in SOFCs on Heat and Mass Transfer Limitations: Interparticle, Interphase and Intraparticle Transport

2011 ◽  
Author(s):  
Hedvig Paradis ◽  
Martin Andersson ◽  
Jinliang Yuan ◽  
Bengt Sunde´n
Keyword(s):  
Mass Transfer ◽  
Kinetic Parameters ◽  
Heat And Mass Transfer ◽  
Electrochemical Reaction ◽  
Catalyst Particle ◽  
Reaction Rates ◽  
Transport Processes ◽  
Effect Of Temperature ◽  
Parameter Study ◽  
Time Saving

The transport processes in the porous, micro-structured electrodes are one of the least understood areas of research of the solid oxide fuel cell (SOFC). To enhance the knowledge of the transport process’ impact on the performance in the electrodes, the micro-structure needs to be modeled in detail. But at these smaller scales, it can be both cost and time saving to first conclude at which scales, the limiting action on the transport processes occurs. This study investigates the limiting effect of the kinetic parameters’ on the heat and mass transfer at interparticle, interphase and intraparticle transport level. The internal reaction and the electrochemical reaction rates are studied at three levels in the microscopic range or even smaller. At the intraparticle level the effect of temperature distribution, i.e., heat transfer, within a catalyst particle is often less limiting than the internal mass diffusion process, while at the interphase level the former is more limiting. In this study, no severe risk for transport limitations for the anode and the cathode of the SOFC was found with the chosen kinetic parameters. It was found that the reaction rates constitute the largest risk. A parameter study was conducted by increasing the steam reforming and the electrochemical reaction rates by a factor of 100 without any transport limitations for the same kinetic parameters. The result of this study provides one type of control of the kinetic parameters which in turn have an impact on the reforming reaction rates and the cell performance.

scholarly journals Pulsed Multiphase Flows—Numerical Investigation of Particle Dynamics in Pulsating Gas–Solid Flows at Elevated Temperatures

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 815
Author(s):  
Arne Teiwes ◽  
Maksym Dosta ◽  
Michael Jacob ◽  
Stefan Heinrich
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Multiphase Flows ◽  
Gas Flow ◽  
Elevated Temperatures ◽  
Process Intensification ◽  
Particle Dynamics ◽  
Transport Processes ◽  
Pulse Combustion ◽  
New Processing

Although the benefits of pulsating multiphase flows and the concomitant opportunity to intensify heat and mass transfer processes for, e.g., drying, extraction or chemical reactions have been known for some time, the industrial implementation is still limited. This is particularly due to the lack of understanding of basic influencing factors, such as amplitude and frequency of the pulsating flow and the resulting particle dynamics. The pulsation generates oscillation of velocity, pressure, and temperature, intensifying the heat and mass transfer by a factor of up to five compared to stationary gas flow. With the goal of process intensification and targeted control of sub-processes or even the development of completely new processing routes for the formation, drying or conversion of particulate solids in pulsating gas flows as utilized in, e.g., pulse combustion drying or pulse combustion spray pyrolysis, the basic understanding of occurring transport processes is becoming more and more important. In the presented study, the influence of gas-flow conditions and particle properties on particle dynamics as well as particle residence time and the resulting heat and mass transfer in pulsating gas–solid flows are investigated.

Heat and Mass Transfer in Advanced Batteries

1999 ◽  
Author(s):  
C. Y. Wang ◽  
W. B. Gu ◽  
R. Cullion ◽  
B. Thomas
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Materials Science ◽  
Lithium Ion ◽  
Rechargeable Batteries ◽  
Transport Processes ◽  
Nickel Metal ◽  
Nickel Metal Hydride ◽  
Power Sources ◽  
Penn State

Abstract This paper presents an overview of heat and mass transfer issues in advanced rechargeable batteries such as nickel-metal hydride (Ni-MH) and lithium-ion (Li-ion) batteries. These batteries are important power sources for ultra-clean, fuel-efficient vehicles and modern portable electronics. Recent demands for environmentally responsible vehicles and strong portable power have prompted fundamental studies of heat and mass transport processes in battery systems in conjunction with electrochemistry and materials science. In this paper, discussions are presented on what are the critical heat and mass transfer issues present in advanced batteries and how these issues affect the battery performance, safety, life cycle, and cost. A theoretical framework describing the transport phenomena with electrochemical reactions is provided. Selected results are presented to illustrate the importance of coupled electrochemical and thermal modeling for advanced batteries. The recent progress is also reviewed in developing and validating battery models at Penn State GATE Center for Advanced Energy Storage.

Heat and Mass Transfer in Granular Potash Fertilizer With a Surface Dissolution Reaction

1999 ◽  
Author(s):  
Shi-Wen Peng ◽  
Robert W. Besant ◽  
Graeme Strathdee
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Electrolyte Solution ◽  
Air Flow ◽  
Mass Gain ◽  
Electrolyte Solutions ◽  
Liquid Electrolyte ◽  
Transport Processes ◽  
Transient Temperature ◽  
Non Equilibrium

Abstract Potash is a widely used granular fertilizer and when exposed to high humidities it readily adsorbs water forming a liquid electrolyte solution on each particle. Heat and mass transfer due to air flow through granular potash beds is studied experimentally and numerically. A one dimensional experimental set-up is used to measure the temperature and air humidity response and mass gain of a potash bed subject to a step change in air flow. A porous media mathematical model is developed to predict the transient temperature and moisture content distributions. The transport processes are modelled as non-equilibrium heat and mass transfer between the porous solid and air flow gaseous phases. The state of the surface electrolyte solution is modelled by the thermodynamics of electrolyte solutions. Experimental and numerical results shows that when there is a strong surface heat source due to phase change, especially near the entrance region, non-equilibrium internal moisture and heat transfer processes exist. The temperature difference between potash granules and the air flowing through the potash bed is significant.

Modelling of Hygro-Thermal Processes in Steel-Concrete Composite Columns Exposed to High Temperatures

2016 ◽  
Vol 249 ◽  
pp. 246-252 ◽  
Author(s):  
Radek Štefan ◽  
Jaroslav Procházka
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Mathematical Models ◽  
Heat And Mass Transfer ◽  
Composite Structures ◽  
Transport Processes ◽  
Thermal Processes ◽  
Moisture Migration ◽  
Composite Columns ◽  
Thermal Distribution

In the paper, transport processes in heated steel-concrete composite columns are analyzed. Mathematical models of heat transfer and coupled heat and mass transfer are described with respect to the specific parameters of composite structures. Numerical formulations of the models are implemented into MATLAB environment and the applicability of the models is depicted on an illustrative example. It is shown that not only the thermal distribution, but also the moisture migration as well as the pore pressure built-up are of particular interest.

Heat and Mass Transfer and Wall Contact for Laminar Vortices in Microreactors

2008 ◽  
Author(s):  
Simon Dreher ◽  
Matthias Kronsbein ◽  
Peter Woias
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Chemical Reactions ◽  
Characteristic Parameter ◽  
Transport Processes ◽  
High Mass ◽  
Number Range ◽  
Exothermic Reactions ◽  
Dean Vortices ◽  
Fast Reactions

In microreactors, interactions between fluid and channel wall affect many chemical reactions. Due to a good heat and momentum transfer, highly exothermic reactions can be quenched and so combustion is inhibited. On the other hand, reactions on catalyst-coated walls call for a high mass transport to and from the walls which is one of the parameters determining the reaction rate for fast reactions. In this contribution, heat and mass transfer towards the walls are investigated in bent microchannels. Laminar flow in the Reynolds number range of 100 < Re < 1000 is studied, where Dean vortices are induced by bends. Optimized geometries of the bends are found with numerical fluid simulations and compared experimentally using chemical reactions. As characteristic parameter, the contact time distribution is calculated which is defined by the distribution of the residence time in regions near the wall. For the characterization of the reactors, also simulations of heat flux are performed. Various optimized reactors are fabricated and experimentally compared by a luminol reaction catalyzed at the copper-plated walls. In other experiments, heat transfer into the fluid is measured. The experimental results are compared to the simulated transport processes.

Energy Transport and Thermal Stress Formation in Hybrid Laser-MIG Welding

2013 ◽  
Author(s):  
Jun Zhou ◽  
Amir Khalilollahi ◽  
Hai-Lung Tsai
Keyword(s):  
Residual Stress ◽  
Mass Transfer ◽  
Thermal Stress ◽  
Laser Welding ◽  
Heat And Mass Transfer ◽  
Welding Process ◽  
Transport Processes ◽  
Formation Mechanisms ◽  
Mig Welding ◽  
Stress Formation

This study is focusing on understanding the thermal stress formation in hybrid laser-MIG welding which has been gaining a lot of interests due to its many advantages over laser welding. Thermal stress formation is tightly associated with heat and mass transfer in hybrid laser welding, so accurate analysis of heat transfer process in the welding process is critical to correctly predict thermal stress information and residual stress in hybrid laser welds. In this study, a comprehensive heat and mass transfer model analyzing the energy, mass, and momentum transport processes in hybrid laser-MIG welding is successfully integrated with a mechanical model to study thermal stress formation in hybrid laser-MIG welding and residual stress in final welds as well. High compressive stress is found to exist on the top surface of the weld which might cause irregular welds topology and high tensile residual stresses were found in some locations in the final weld. This proposed study can be used as a foundation to further understand the thermal stress formation mechanisms in welding and to provide an efficient way to optimize the hybrid laser-arc welding process.

Transient magneto-micropolar free convection heat and mass transfer through a non-Darcy porous medium channel with variable thermal conductivity and heat source effects

2009 ◽  
Vol 223 (10) ◽  
pp. 2341-2355 ◽  
Author(s):  
S Rawat ◽  
R Bhargava ◽  
Renu Bhargava ◽  
O A Bég
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Porous Medium ◽  
Free Convection ◽  
Heat And Mass Transfer ◽  
Chemical Engineering ◽  
Variable Thermal Conductivity ◽  
Transport Processes ◽  
Convection Heat ◽  
Free Convection Heat

The laminar, fully developed, transient magnetohydrodynamic (MHD) free convection heat and mass transfer of an electrically conducting micropolar fluid between two vertical plates containing a non-Darcy porous medium with heat generation/absorption and asymmetric wall temperature and concentration has been discussed in this article. A similarity transformation is used to render the problem into a system of coupled, partial, differential equations, which are solved using the finite-element method (FEM). The solutions are validated with a robust finite difference method (FDM) solver. The present work examines the effect of Darcian parameter, Forchheimer parameter, heat absorption/generation parameter, vortex viscosity parameter, buoyancy ratio parameter, magnetic parameter, and variable thermal conductivity parameter on velocity, angular velocity, temperature and concentration profiles. Space—time graphs of velocity and microrotation are also plotted to provide a better perspective of the flowfield evolution with respect to time. Applications of the study may arise in, for example, packed-bed chemical reactors, materials processing, magnetic field control of chemical engineering transport processes in filter media, purification of hydrocarbons with electromagnetic fields, etc.

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