Heat Transfer Papers

Heat Transfer

Heat Transfer describes the process of heat energy being transported when a system moves from one equilibrium state to another. Heat Transfer is divided into three modes: Conduction, Convection, and Radiation

Conduction Heat Transfer

Conduction is a mode of heat transfer where heat energy is transported from more energetic particles to less energetic particles. The basic equation that describes heat transfer through conduction is Fourier’s law, as shown below.

Convection Heat Transfer

Convection is a mode of heat transfer where heat energy is transported from a solid object to a liquid or gas that passes over its surface while it is in motion. The amount of heat energy transferred through this mode can be described using Newton’s law of cooling, as shown below. It is important to note that the Convective Heat Transfer Coefficient (h) is always positive.

Convection can be classified into two main types, forced or natural convection. Additionally, depending on whether the fluid is flowing over or through a channel, convection can also be classified as external or internal.

Natural Convection Heat Transfer

Fluid motion over the objects surface is inducted by buoyancy effects that have resulted from the change in density. This change is due to the differences in temperature of the fluid as heat energy is transferred.

Forced Convection Heat Transfer

Fluid motion over the objects surface is inducted by mechanical means. This is externally introduced by way of a pump or fan.

Radiation Heat Transfer

Heat energy is transported as electromagnetic waves or photons. This occurs due to the changes in the electronic configurations of the atoms or molecules within the object. All solids, liquids, and gases above absolute zero emi...

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...1904 also introduced the concept of the boundary layer (Cengel, Cimbala, & Turner, 2012). The equation for the Prandtl Number is shown below.

Thermal Boundary Layer

The Thermal Boundary Layer describes the interaction and exchange of thermal energy between a surface and flowing fluid. When a fluid at a specific temperature flows across an adjacent surface of different temperature, the interactions between the two surfaces will result in the formation of a boundary layer. At this point the particles of the fluid will assume the temperature of the surface and reach thermal equilibrium. This thermal energy will then travel through the remainder of the fluid where it will result in a temperature profile within the flow field ranging from the surface temperature (T_w ) to the ambient temperature (T_∞ ), (Cengel, Cimbala, & Turner, 2012), this is shown in figure XX below.