Thermal and flow processes are ubiquitous in mechanical, aerospace and chemical engineering systems. Experimental methods including thermal and flow diagnostics are therefore an important element in preparation of future engineers and researchers in this field. Due to the interdisciplinary nature of experimentation, a fundamental guidance book is essential in the engineering curriculum and as a technical reference. Thermal and Flow Measurements provides a synthesis of the basic science and engineering of diagnostic methods that students and engineers need to understand, design and apply to measurements in mechanical, aerospace and chemical engineering processes. A clear exposition is given on the basic concepts and application aspects of a wide range of thermal and flow diagnostics, starting from basic sensors, flow visualization, velocimetry, laser optical diagnostics, particle sizing methods, gas sampling methods, to micro-, nano-scale sensors and lidars. The presentation of topics allow readers to see the fundamental principles behind each methodology as well as the application details.