In heat transfer, radiation is one of the three fundamental modes of energy transport, alongside conduction and convection. Unlike the other two, which require matter to carry energy, radiation involves the transfer of thermal energy via electromagnetic waves (Bergman, Lavine, and Incropera, 2019, chapter 12). All matter above absolute zero emits thermal radiation, and this phenomenon is particularly significant at high temperatures or in environments where conduction and convection are minimal (such as in a vacuum).
The analysis of radiative heat transfer involves understanding both the physics of emission and the geometrical relationships between surfaces. Surfaces emit radiation according to their temperature, emissivity, and surface area. The amount of energy emitted per unit area is governed by the Stefan–Boltzmann Law (Bergman, Lavine, and Incropera, 2019, equation 12.37, p. 729): \[ E = \varepsilon \sigma T^4, \] where:
Most real surfaces do not emit as much energy as a perfect blackbody (\(\varepsilon = 1\)), and their emissivity depends on the material, surface finish, and temperature (Bergman, Lavine, and Incropera, 2019, figure 12.19). This makes radiation a powerful but sometimes unintuitive mode of heat transfer to measure or predict.
In this lab, we introduce thermal imaging as a tool for visualizing radiative heat transfer. A thermal imager (or infrared camera) detects infrared radiation emitted by objects and converts it into temperature data. This allows us to observe spatial temperature distributions in real time and non-invasively—an advantage when physical contact is difficult or would alter the system being measured.
We will explore how different materials radiate and retain heat, how friction generates detectable thermal signatures, and how temperature measurements depend critically on properties like emissivity. The lab also connects heat transfer with practical sensing technology used in engineering diagnostics, maintenance, and design.
By the end of this lab, you should be able to: