Heat transfer enhancement technologies of heat sinks or heat exchangers has been a particular interest in the compact design of thermal systems. Aluminum foam materials have attracted much attention due to its inherent characteristics of an extensive contact area between fluid and solid and an increased thermal dispersion. Heat transfer enhancement by using low resonance can be another solution. The natural frequency exists in any thermal systems, which is changed according to flow geometry, flow rate, temperature, and so forth. If the frequency of an external forcing is in tune with the natural shedding frequency, the flow mixing inside a thermal system becomes intense and results in higher heat transfer rate.