Infrared thermographic measurements of heat transfer enhancement over ribbed surfaces

The paper presents the experimental results on heat transfer characteristics of air forced convection over two ribbed not-thin plates and a flat plate for comparison, obtained by means of infrared thermography. This technique is attractive because it allows a full-field, non-contact, high spatial resolution, measurement of the surface temperature and heat-transfer-coefficient distribution if heat flux distribution is given. In the present case, heat flux is known but at a some depth from the surface convectively cooled while heat diffusion through the plate being not negligible. In this paper, we first present the procedure for processing thermographic images, then its calibration versus convection data over a flat plate, and finally thermal performances of two roughened surfaces with square cross-section ribs perpendicularly arranged to airflow, with two values of the corrugation pitch to rib side ratio, i.e., 33.3 and 13.3. Convection data are for air flows at room temperature with a speed between 2.3 and 11.6 m/s, corresponding to ReL ranging from 31000 to 155000, and for heat fluxes between 650 and 820 W/m2