In combustion engines, what main purpose does designing a cooling circuit that works under pressure serve?

Question

DentroTest · Accepted Answer

Increasing the pressure a fluid is subjected to raises its boiling point. Pure water at atmospheric pressure boils at 100 ºC; by sealing and pressurizing the closed cooling circuit (through the cap with pressure and vacuum valves), the liquid can exceed 100 ºC without boiling. This prevents the formation of vapor pockets, which would drastically reduce heat dissipation and damage the engine block. Keeping the engine below 80 ºC is not the purpose of pressurizing the circuit: the optimal operating temperature of heavy engines is around 85-90 ºC, and running below it reduces thermal efficiency and produces more residues and wear. Nor is the circuit pressurized to force the engine to run permanently at 120 ºC, but to provide a sufficient thermal safety margin that absorbs overloads without risk of boiling.

In combustion engines, what main purpose does designing a cooling circuit that works under pressure serve?

Want to pass the Permit C and C1 (English) theory test first time?