The characteristic of the heat exchange mechanism by slit resonators is numerically investigated. In general, a rocket engine chamber is filled with hot gas, and slit resonators, which are equipped outside of the chamber wall near faceplate, are filled with cold gas. Therefore, when the resonators work well, the cold gas in the resonator might be exchanged for the hot gas in the rocket engine because of acoustic oscillations or vortex generations and motions. In this paper, the heat exchange mechanism by the slit resonators is numerically evaluated on the effect of intensity of incident wave, slit resonator shapes, and kinematic viscosity. In addition, the new idea of a slit resonator shape for the suppression of the heat exchange and its damping performance are mentioned.