ABSTRACT
An experimental investigation of heat transfer in a rectangular channel (aspect ratio AR equal to 5) with angled rib turbulators, inclined at 45 deg, is presented. The angled ribs (of square section, size e) were deployed with parallel orientations on one or two surfaces of the channel. Four values of the rib pitch p were considered in order to investigate the range of the rib pitch-to-height ratio p/e from 6.66 to 20.0. The convective fluid was air, and the Reynolds number varied from 9000 to 35500.
Experiments were based on the use of heating foils (for the attainment of uniform heat flux condition) and of the steadystate, liquid crystal thermography (for the identification of isotherm lines and the reconstruction of local heat transfer coefficient). This technique provides very detailed distributions of the local heat transfer coefficient between ribs.
Spatially-resolved, regionally averaged and full-surface averaged Nusselt numbers are presented and discussed. Results showed that a periodic fully developed regime is generally achieved after a relatively short distance from the test section entrance. Distributions of local heat transfer coefficient h present features typically affected by the rib pitch-to-height ratio and only marginally by the Reynolds number and the rib installation (on one side of the channel or on two opposite walls). These last parameters generally influence the extent of h values rather than the form of their spanwise and streamwise distributions.
