Transport process characteristics of catalytically supported thermal combustion systems
Creators: name: Chen, Junjie
Publisher: name: figshare
Year: 2022
Subjects: subject: 90403 Chemical Engineering Design
subject: FOS: Chemical engineering
subject: 90499 Chemical Engineering not elsewhere classified
subject: 90402 Catalytic Process Engineering
subject: 91501 Computational Fluid Dynamics
subject: FOS: Other engineering and technologies
subject: 91502 Computational Heat Transfer
subject: 91505 Heat and Mass Transfer Operations

description: Transport phenomenon, in physics, is any of the phenomena involving the movement of various entities, such as mass, momentum, or energy, through a medium, fluid or solid, by virtue of nonuniform conditions existing within the medium. Variations of concentration in a medium, for example, lead to the relative motion of the various chemical species present, and this mass transport is generally referred to as diffusion. Variations of velocity within a fluid result in the transport of momentum, which is normally referred to as viscous flow. Variations in temperature result in the transport of energy, a process usually called heat conduction. There are many similarities in the mathematical descriptions of these three phenomena, and the three often occur together physically, as in combustion, where a flowing viscous fluid mixture is undergoing chemical reactions that produce heat, which is conducted away, and that produce various chemical species that interdiffuse with one another. Diffusion is a process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration. Heat conduction in fluids involves thermal energy transported, or diffused, from higher to lower temperature. Operation of a nuclear reactor involves the diffusion of neutrons through a medium that causes frequent scattering but only rare absorption of neutrons. The rate of flow of the diffusing substance is found to be proportional to the concentration gradient. For viscous material, there is laminar (slow, smooth, parallel) flow; one must exert a force to maintain motion because of internal frictional resistance to flow, called the viscosity. Viscosity varies with the applied stress, strain rate, and temperature. Thermal conduction is the transfer of energy arising from temperature differences between adjacent parts of a body. Thermal conductivity is attributed to the exchange of energy between adjacent molecules and electrons in the conducting medium. The rate of heat flow in a rod of material is proportional to the cross-sectional area of the rod and to the temperature difference between the ends and inversely proportional to the length; that is the rate H equals the ratio of the cross-section of the rod to its length, multiplied by the temperature difference and by the thermal conductivity of the material. A substance of large thermal conductivity is a good heat conductor, whereas one with small thermal conductivity is a poor heat conductor or good thermal insulator. Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: komcjj@gmail.com, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China