Experimental setup and preliminary results for the background. Oriented Schlieren technique in heat transfer measurements

In this study, a measurement technique based on the refractive index variation in a compressible flow field is presented. From now on, this concept will be referred as ‘Background Oriented Schlieren’ (BOS) method. The underlying principle of BOS is briefly described by combining the convective heat transfer and optical equations and an equation of state that provides the relation between temperature and refraction index. In the second part the various optical techniques, which can be compared with BOS, will be discussed. Last chapter is dedicated to the experiment setup and the use of the BOS technique. The focus of the study is to investigate in which way the temperature difference between the air and a protruding plate, which is kept at uniform temperature, affects the average heat transfer coefficient and the local heat transfer coefficient.