Knowra Transport phenomena Transport phenomena Transport phenomena describe how momentum, heat, and chemical species move through fluids and materials. Their shared mathematical structure links fluid flow, thermal conduction, and diffusion.
Conservation law : A rule stating that a quantity remains constant in a closed system, though it may move or change form. Transport equations track conserved quantities as they cross boundaries and move through space.
Newton's law of viscosity : A constitutive law relating shear stress to the velocity gradient in a Newtonian fluid. It describes momentum transport by viscous shear.
Heat exchanger : A device that transfers heat between fluid streams while keeping them physically separate. Its design balances thermal transport against pressure loss and equipment size.
Molecular diffusion : The net spreading of particles caused by random molecular motion and concentration differences. It is distinct from bulk transport by advection, though both often act together.
Constitutive equation : A relation that specifies how a material responds to physical conditions such as stress, temperature gradients, or concentration gradients. Constitutive laws connect fluxes to driving forces, closing transport equations.
Fourier's law : A constitutive law stating that heat flux in a conducting medium is proportional to the negative temperature gradient. It describes heat transport by conduction and defines thermal conductivity.
Chemical reactor : Equipment in which chemical reactions are carried out under controlled conditions. Reaction rates compete with heat and species transport, shaping reactor performance.
Turbulent transport : The redistribution of momentum, heat, or matter by fluctuating motions in a turbulent flow. It can greatly exceed molecular transport and requires additional modeling.
Flux : The rate at which a physical quantity passes through a unit area, often expressed per unit time. Flux quantifies the momentum, energy, or matter crossing a surface.
Fick's laws of diffusion : Laws relating diffusive matter flux to concentration gradients and describing how concentration evolves over time. They describe mass transport driven by concentration differences.
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