Application of a new method to quantify local air-side heat transfer coefficient on fundamental geometries

A new optical method based on the analogy between heat and mass transfer is developed to obtain local air-side heat transfer coefficient (HTC). It uses thin-film coatings applied to the heat transfer surface in combination with a tracer gas. Experiments with fundamental geometries were conducted to calibrate the process and evaluate its accuracy. The local air-side HTCs results for laminar flow over a flat plate are within 20% compared to the Blasius solution except for the leading and trailing edges. The mass transfer experiments are conducted in a wind tunnel. Calibration for the flat plate experiments takes into account flow velocity, light source, relative humidity of air, tracer gas concentration, and sample aging effects. Correlations for these parameters have been established. The measurements of the basic geometries such as inclined plates, wedges, and cylinders agree with the experimental results of literatures which employed different methods. These promising validation experiments justify the exploration of more complex geometries and entire heat exchangers using this technique.