The conjugate heat transfer characteristics under a normally synthetic jet driven by piston actuator and horizontally forced flow were investigated experimentally. The effects of excitation frequency and orifice shape on the flow and heat transfer characteristics are explored. The piston-driven actuator produces fairly big velocity at higher operating frequency and the time-averaged orifice velocity is almost proportional to the frequency when the piston reciprocates at relatively low frequency (from 8 Hz to 24 Hz). The orifice shape shows very weaker effect on the exit velocity of synthetic jet, given the same orifice exit area, but has an important influence on the interaction between the normally synthetic jet and horizontally forced flow. The convective heat transfer capacity is enhanced under the conjugate action of a synthetic jet and forced flow, especially significant at higher excitation frequency of the synthetic jet. For all the orifice shapes, the peak laterally-averaged convective heat transfer coefficient is increased up to 100% in relative to individual action of the forced flow when the piston reciprocates at 24 Hz. Such detailed heat transfer results about the conjugate heat transfer characteristics have not been reported earlier and are expected to be useful for understanding the effects of excitation frequency and orifice shape on the conjugated heat transfer characteristics. (C) 2012 Elsevier Ltd. All rights reserved.