A synthetic jet is caused by the periodic motion of a diaphragm within a cavity. There is one or more orifices or outlets in this cavity. The main advantage of this type of jet compared to a continuous jet is that the synthetic jet is composed of transverse flow, and therefore, it does not need a continuous source of fluid, unlike the continuous jet. In recent years, synthetic jets have received a great deal of attention so that they have been used in a wide range of applications such as controlling separation and turbulence, besides, the cooling of electronic equipment and propulsion. In the present study, the jet is placed perpendicular to the flat plane with constant heat flux, thereafter, the effect of some geometric parameters were evaluated numerically such as the ratio of the distance between the jet and the impinging plate to the nozzle width, the ratio of the impinging plate length to the jet nozzle width, the ratio of cavity width of the synthetic jet to the nozzle width, the ratio of the cavity height to the nozzle width, the angle of the impinging plate, besides, the diaphragm specifications including amplitude and frequency of the jet diaphragm in heat transfer using OpenFOAM open-source software. The results show that the frequency and the length of the impinging plate are the most effective parameters, respectively, in terms of the diaphragm and geometry.