Introduction to Engineering Heat Transfer

Chapter 2 considered problems that were truly one-dimensional. Energy transfer occurred only in one coordinate direction and therefore temperature varied only in that direction. In this chapter, we will examine problems that are only approximately one-dimensional, referred to generally as extended surfaces. Extended surfaces are typically thin pieces of conductive material that can be approximated as being isothermal in two dimensions and having temperature variations in only one direction. In an extended surface, energy is transferred laterally (i.e., across the thickness) but the temperature change induced by the energy transfer is sufficiently small that it can be neglected. The extended surface approximation greatly reduces the complexity of the problem and can often be applied with little loss in accuracy.