Lecture

Internal Flows and Boundary Layers

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In course

ME-465: Advanced heat transfer

The course will deepen the fundamentals of heat transfer. Particular focus will be put on radiative and convective heat transfer, and computational approaches to solve complex, coupled heat transfer problems. ...

Description

This lecture covers the analysis of internal flows and boundary layers in heat transfer. Topics include hydrodynamic entry length, laminar and thermal entry lengths, mean temperature, heat transfer coefficient, and correlations for the Nusselt number. The presentation delves into the thermal boundary layer, energy balance, and the importance of axial conduction. The lecture also discusses the analytical solutions for laminar flows, the impact of viscous dissipation, and the numerical solutions for flow problems. Various concepts such as the Nusselt number, thermal fully developed flow, and the solution techniques for internal energy balances are explored.

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Official source

Ontological neighbourhood

Physics

Mechanics: Fluid mechanics

Related concepts (32)

Heat transfer coefficient

In thermodynamics, the heat transfer coefficient or film coefficient, or film effectiveness, is the proportionality constant between the heat flux and the thermodynamic driving force for the flow of heat (i.e., the temperature difference, ΔT ). It is used in calculating the heat transfer, typically by convection or phase transition between a fluid and a solid. The heat transfer coefficient has SI units in watts per square meter per kelvin (W/m2/K).

Convection

Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convection is unspecified, convection due to the effects of thermal expansion and buoyancy can be assumed. Convection may also take place in soft solids or mixtures where particles can flow. Convective flow may be transient (such as when a multiphase mixture of oil and water separates) or steady state (see Convection cell).

Forced convection

Forced convection is a mechanism, or type of transport, in which fluid motion is generated by an external source (like a pump, fan, suction device, etc.). Alongside natural convection, thermal radiation, and thermal conduction it is one of the methods of heat transfer and allows significant amounts of heat energy to be transported very efficiently. This mechanism is found very commonly in everyday life, including central heating, air conditioning, steam turbines, and in many other machines.

Convection cell

In the field of fluid dynamics, a convection cell is the phenomenon that occurs when density differences exist within a body of liquid or gas. These density differences result in rising and/or falling currents, which are the key characteristics of a convection cell. When a volume of fluid is heated, it expands and becomes less dense and thus more buoyant than the surrounding fluid. The colder, denser part of the fluid descends to settle below the warmer, less-dense fluid, and this causes the warmer fluid to rise.

Heat transfer

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer.

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