Thermal performances of corrugated channel with skewed wall waves at rolling and pitching conditions

This experimental study investigates the thermal performances of a narrow wavy channel which swings about two orthogonal axes under single and compound rolling and pitching oscillations. Full-field Nusselt number (Nu) images over the wavy channel wall are detected at static and swinging conditions by infrared thermography method and examined comparatively to highlight the influences of rolling and pitching oscillations on heat transfer performances. A set of selected heat transfer data illustrates the individual and interdependent influences of rolling and pitching oscillations on the detailed Nu distributions and the area-averaged Nusselt numbers ((Nu) over bar). Pressure drop coefficients (f) for isothermal flows and thermal performance factors (TPF) at static and swinging conditions are subsequently analyzed. For this particular channel configuration, the single rolling or pitching oscillation elevates (Nu) over bar from the static references; whereas the synergistic effects of compound rolling and pitching oscillations with either harmonic or non-harmonic rhythms suppress the beneficial heat transfer impacts by single rolling or single pitching oscillations. Buoyancy effects in isolation elevate (Nu) over bar but are weakened as the relative strength of swinging force enhances. Pressure drop coefficients (f) consistently increase as the relative strength of swinging forces increases. At the expense of increased pressure drop penalties for heat transfer augmentations by swinging oscillations, the thermal performance factor (TPF) respectively increases and decreases as Reynolds number (Re) increases with laminar and turbulent reference conditions. Empirical heat-transfer and pressure-drop correlations are generated to permit the evaluations of individual and interactive effects of single and compound swinging force effects with buoyancy interactions on (Nu) over bar and f coefficients. By the aid of these (Nu) over bar and f correlations, the favorable and worse operating conditions in terms of the swinging parameters for the TPF properties of this corrugated wavy channel are identified. (C) 2012 Elsevier Ltd. All rights reserved.