Development of Combined Particle Image Velocimetry and Particle Image Thermography for Air Flows

Simultaneous measurements of instantaneous velocity and temperature fields of air flows by means of Particle Image Velocimetry (PIV) and Particle Image Thermography (PIT) enables highly demanded studies on thermal plumes, their dynamics and the resulting heat transfer for Pr ≈ 0.7. Thereby, small particles of thermochromic liquid crystals (TLCs), which reveal temperature depending reflection properties are used as tracer particles for combined PIT and PIV. The feasibility of the method is demonstrated in a Rayleigh-Be´nard convection experiment in a cubical enclosure. Furthermore, a new particle generator being able to produce continuously very small monodisperse droplets of TLCs has been designed. The improvement of the developmental process for mixed and Rayleig-Be´nard convection studies is discussed. Thereby, special focus is laid on the production process of small TLCs, the generation of monodisperse acetone-TLC droplets and the temperature depending colour play of the produced particles.