ABSTRACT
Interfacial phenomena are present in many relevant applications, from food processing to electronics cooling. Accurate measurement of temperatures and heat transfer evaluation at liquid–solid interfaces is a challenging and paramount task toward the description of the complex transport phenomena occurring at such interfaces. This chapter revises the evolution of the measurement techniques available to describe the heat transfer processes occurring at liquid–solid interfaces for single- and two-phase flows (considering liquid phase change). This critical review discusses the challenges and limitations of the various existing techniques, from the use of thermocouples to state-of-the-art micro-sensors, infrared thermography, and laser diagnostic techniques. Besides describing the techniques, particular case studies are addressed discussing the application of the various methods in liquid–solid interfacial flows. The use of these measurement techniques in liquid–solid interfaces considers two specific techniques: a contact technique and a contactless (non-intrusive) technique. Hence, the potential of thermocouples is explored to characterize temperatures and heat fluxes at liquid–solid interfaces. Despite their various limitations, commercial thermocouples are still the most affordable solution available to many researchers. In line with this, adequate calibration and data reduction procedures are discussed to obtain reliable measurements with thermocouples at liquid–surface interfaces. The non-intrusive techniques, on the other hand, are represented by infrared thermography with a high spatial and temporal resolution. However, even if they are non-intrusive techniques, their use in liquid–solid interfacial measurements is difficult because they need an accurate calibration and data reduction procedures rarely described in the literature. Hence, such processes are discussed here, and the application of this technique to droplet–wall interactions and nucleate boiling characterization is illustrated.
