In this article we will discuss about the conditions and significance of heat transfer. Steady and Unsteady Conditions of Heat Transfer: Heat exchange between two systems may take place under steady (stable) thermal conditions or under unsteady (unstable) thermal conditions. Steady state implies that temperature at each point of the system remains constant in the course of time, and it [...]
Many situations are encountered where it is desired to reduce the overall heat transfer between two radiating surfaces. The task is accomplished by placing radiation shields between the emitting surfaces. The shields are thin opaque partitions arranged in the direction perpendicular to the propagation of radiated heat, and made of materials of very low absorptivity and high reflectivity (thin sheets [...]
The radiative heat exchange between two systems (surfaces) is generally calculated from the simplified equation- The factor hr is called the coefficient of radiant heat transfer from solid to solid and is expressed in W/m2-deg temperature difference between the enclosed and enclosing surfaces. The value of hr can be calculated from the heat flux equation for any configuration. For example, [...]
In many engineering situations, means are often sought to improve heat dissipation from a surface to its surroundings. The Newton-Rikhman relation Q = hA (t - ta) reveals that the convective heat flow can be enhanced by increasing the film coefficient h, the surface area A and the temperature difference (f - ta). The convective coefficient is a function of [...]