Heat transfer performance of pre-cooler under unsteady inflow pressure condition using dynamic mode decomposition method

The heat transfer performance of a staggered-tube-bundle pre-cooler under unsteady inflow pressure condition was numerically studied with large eddy simulation method, and the dominating flow structures were identified using the dynamic mode decomposition method. The influences of the inflow pressure frequency on the internal flow, heat transfer performance and entropy generation within the pre-cooler were analyzed. Results suggested that the inflow pressure frequency had little impact on both the time-averaged heat transfer performance and the transient heat transfer performance. When the inflow pressure frequency reached the natural frequency of 950 Hz, the flow resonance occurred and the heat transfer fluctuated dramatically. The shear layer and shedding vortexes were the dominating flow structures, and their spatiotemporal evolution determined the transient heat transfer performance. When flow resonance occurred, the evolvement of the shear layer was closely related to the inflow velocity fluctuation. For the upstream cylinders, the period of the shedding vortexes was the same with that of the inflow pressure and velocity, while the period of the shear layer development was twice of the inflow pressure and velocity. Moreover, the entropy generation relied on the dominating flow structures, and its spatiotemporal evolution was in accordance with that of the dominating flow structures.