We study an array of streamwise-oriented Dielectric Barrier Discharge (DBD) plasma actuators as an active control technique in turbulent flows. The analysis aims at elucidating the mechanism of interaction between the structures induced by the DBD-plasma actuators and the convective heat transfer process in a fully developed turbulent boundary layer. The employed flush-mounted DBD-plasma actuator array generates pairs of counter-rotating, stationary, streamwise vortices. The full three-dimensional, velocity field is measured with stereoscopic PIV and convective heat transfer at the wall is assessed by infrared thermography. The plasma actuator forcing diverts the main flow, yielding a low-momentum region that grows in the streamwise direction. The suction effect promoted on top of the exposed electrodes confines the vortices in the spanwise direction. Eventually, the pair of streamwise vortices locally reduces the convective heat transfer with a persistence of several outer lengthscales downstream of the actuation.