Investigation of the effects of jets having different structures, produced sequentially, on impinging jet heat transfer

In this study, the heat transfer distributions created by the synthetic jet flow produced sequentially with a loudspeaker-type actuator on a homogeneously heated plane plate were investigated using a thermal camera. Tandem jet flows were obtained by using drive signals obtaine by modifying the square and sinusoidal signals in different structures using the signal generator. The flow field properties and heat transfer distributions of the synthetic jet produced by the signals of fixed 10 Hz frequency consisting of two half square signals or half sinusoidal and half square signals were investigated. In this context, local Nusselt number distributions are presented for 8 different signal structures named from T1 to T8. In velocity measurements, instantaneous velocity changes of the flow field were obtained at positions between 0-15 values of y/D along the jet axis by using hot wire anemometer. Impinging jet heat transfer experiments were performed at the dimensionless distance y/D = 2, 4, 6, 8, 10, 12, 14 and 16, which is the dimensionless distance between the jet outlet and the heated plate. A circular nozzle type jet hole with a fixed diameter of 34 mm is used. When T2 signal with a single square signal structure and T1 signal with two tandem square signal structure were compared, an increase of 17,8% was obtained in the tandem T1 signal Nusselt numbers compared to the single T2 signal for y/D=14 positions where the merger being took place.