Gas-gas heat exchangers play a vital role in high-temperature thermal control, waste heat recovery, and exhaust gas energy utilization. They support applications such as air-to-air heat transfer, turbine exhaust heat recovery, oxygen and nitrogen preheating, and combustion air preheating. Common types include plate heat exchangers, recuperators, regenerative heat exchangers, microchannel heat exchangers, and shell and tube heat exchangers. Fluid pairings include exhaust gas-to-intake air, compressed air-to-atmospheric air, and hot process gas-to-inert gas.