Experimental Study of Convection Heat Transfer in the Entrance Region of a Rectangular Duct With Transverse Ribs

The paper presents an experimental study on heat transfer coefficients in a straight rectangular channel containing continuous transverse ribs. The ribs were located on one side of the channel which is heated with a uniform heat flux. Three values of the rib pitch-to-height ratio (10, 20 and 30) were considered, with the Reynolds number, based on the channel hydraulic diameter, ranging from 57,000 to 127,000. The studied geometry is relevant for hot internal structures in aircraft engines. The steady state, liquid crystal thermography technique was used to obtain detailed heat transfer coefficients in the inter-rib surface regions. The main purpose of this study was to investigate the heat transfer behavior between the first repeated ribs, i.e., in the regions where the flow and thermal fields are not yet periodically fully developed.