Experiment on Heat Transfer Enhancement for a Double Pipe Heat Exchanger with Air Injection of Perforated Turbulator

In this study, an attempt is made to evaluate the performance of a double pipe heat exchanger (DPHE) through an experiment.The outside surface of the inner pipe of the DPHE is surrounded with perforated helical tube, where the perforations allow air to enter the annulus.The air injection and the turbulator itself are expected to increase the number of vortices in the boundary layer of the inner pipe (annulus side) and expand the heat transfer regions.Due to the bouncy effect, the small air bubbles within the cold water promote flow eddies and hence increase the thermal performance.The Reynolds number based on the hydraulic diameter of the annulus is ranged from 5,000 to 17,000.The findings demonstrate that for a flow affected by an air injector, performance varies with Reynolds number.Both the Nusselt number and efficiency increase percentages are approximately 27 for each.However, the friction factor raises to 43% compared to the plain case, which only increases the performance evaluation criteria (PEC) by 8%.