What process uses the fuel to manage the thermal load on a liquid engine chamber?

Regenerative cooling

Liquid rocket engines manage the extreme temperatures encountered within the combustion chamber and nozzle through a technique called regenerative cooling. In this process, one of the liquid propellants, usually the fuel, is deliberately circulated through small channels built into the walls of the combustion chamber and nozzle assembly before it is ultimately injected into the chamber for combustion. This circulation path effectively absorbs the intense heat generated by the reaction, using the propellant itself as the cooling agent. This capability ensures that only the chamber and nozzle—the components directly exposed to combustion—must endure the highest thermal stress, allowing the propellant tanks themselves to remain at much lower pressures and temperatures, often built lighter as a result.