In complex applications, where liquid-based cooling is not an option, cooling by impinging jets is an attractive alternative. Several studies have already observed that coaxial impinging jets improve the rate of heat transfer from a body in comparison to a single jet. The goal of the present research is to achieve a further augmentation in the rate of heat transfer by implementing appropriate jet control strategies, such as pulsation of the coaxial jets and addition of swirl component to velocity. The hypothesis is that this pulsation will modulate the strength and the frequency of the primary toroidal vortices that are generated due to the shear layer instabilities in the mixing regions of coaxial jets, and that heat transfer enhancement can be optimized for specific range of the inner and outer jet diameters ratio and pulsation frequency. The investigation entails a systematic study of the spatio-temporal heat transfer characteristics on a heated thin-foil by high-speed infrared thermography, and its detailed correlations to the flow-field measured by phase-locked tomographic particle image velocimetry. The results of the study are expected to significantly enhance heat transfer coefficients in impinging air jet applications and change the way impinging jet cooling is implemented in modern applications.
