Introduction to Engineering Heat Transfer

From a thermodynamic perspective, thermal energy can be transferred across a boundary (i.e., heat transfer can occur) by only two mechanisms: conduction and radiation. Conduction is the process in which energy exchange occurs due to the interactions of molecular (or smaller) scale energy carriers within a material. The conduction process is intuitive; it is easy to imagine energy carriers having a higher level of energy (represented by their temperature) colliding with neighboring particles and thereby transferring some of their energy to them. Radiation is a very different heat transfer process because energy is transferred without the involvement of any molecular interactions. Radiation energy exchange is related to electromagnetic waves and therefore can occur over long distances through a complete vacuum. For example, the energy that our planet receives from the Sun is a result of radiation exchange. This chapter presents an introduction to radiation heat transfer with a focus on providing methods for solving radiation problems.