What type of heat transfer does a regenerative air heater utilize?

A regenerative air heater utilizes heat from previously heated materials, which typically refers to using the waste heat from exhaust gases to preheat the incoming air before it enters the combustion system. This process helps to improve the overall efficiency of the heating system by recovering energy that would otherwise be lost.

In essence, regenerative air heaters use a heat exchanger mechanism where heat is transferred from the hot exhaust gases to the incoming air, thereby reducing the amount of fuel needed for combustion. By effectively using the residual heat from the exhaust, regenerative air heaters enhance energy efficiency, which is crucial for both economic and environmental reasons in power generation systems.

The other forms of heat transfer listed—radiative, convective, and combustion heat transfer—do not accurately describe the main function of a regenerative air heater since it primarily relies on the principle of recovering heat from materials that have already been heated, rather than generating new heat.