Effect of spatially periodic heating or an abrupt contraction at inlet on transitional and turbulent heat transfer in a duct

A three-part investigation of convective heat and mass transfer from a one-sided-heated flat rectangular duct with fully developed transitional and turbulent flow was performed both experimentally and numerically. Quasi-local mass transfer results were obtained via the napthalene sublimation technique. The heat/mass transfer analogy permitted conversion into heat transfer results. First, the duct active wall is held isothermal. Experimental and numerical mass transfer results were generated for Sc = 2.5, supplemented by numerical results for heat transfer to air (Pr = 0.7). Second, the duct active wall is spatially periodically heated (i.e., successive adiabatic and heated segments). Experimental and numerical results were also obtained. Finally, experimental results are obtained for a duct with an unsymmetric contraction of the flow cross section. For the first case, the experimental Sherwood number distributions displayed typical entrance region variations. The fully developed data agreed very well with well-established correlations.