Heat TransferHeat transfer describes the process of transporting thermal energy as 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 in which thermal energy is transported from more energetic particles to less energetic particles. The basic equation describing heat transfer through conduction is Fourier's law, as shown below. Convection Heat Transfer Convection is a mode of heat transfer in which thermal energy is transported from a solid object to a liquid or gas passing over its surface while 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. Furthermore, depending on whether the fluid flows over or through a channel, convection can also be classified as external or internal. Heat transfer by natural convection The movement of the fluid on the surface of the object is induced by buoyancy effects resulting from the change in density. This change is due to differences in fluid temperature during thermal energy transfer. Forced Convection Heat Transfer The movement of the fluid on the surface of the object is induced by mechanical means. This is introduced externally via a pump or fan. Heat transfer by radiation Thermal energy is transported in the form of electromagnetic waves or photons. This occurs due to changes in the electronic configurations of the atoms or molecules within the object. All solids, liquids, and gases above absolute zero emi… half of the paper… 1904 also introduced the concept of a 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 a flowing fluid. When a fluid of a specific temperature flows through an adjacent surface of a different temperature, 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 surface temperature and reach thermal equilibrium. This thermal energy will then travel through the rest of the fluid where it will result in a temperature profile within the flow field ranging from surface temperature (T_w ) to room temperature (T_∞ ), (Cengel, Cimbala, & Turner, 2012 ) , this is shown in figure XX below.