Figure 20. Exhaust Valve

    The air and fuel mixture inducted into the cylinder is convectively heated by the intake manifold and valve. The heat transfer from the valve is modeled as flow over a cylinder, and the heat transfer in the intake manifold is modeled as entry length turbulent flow in a curved pipe.

    The hot exhaust gases convect heat to the exhaust manifold and the exhaust valve. The exhaust manifold conducts a portion of this heat to the head and radiates to the engine block. The exhaust heat transfer from the gas to the valve port, due to the pulsing flow, is about 50% greater than given by steady flow correlations.

    A correlation from Malchow (Malchow et al., 1979, "Heat transfer in the straight section of an exhaust port of a spark ignition engine", SAE Paper 790309) for the exhaust port heat transfer is:

    where the characteristic length for the Nusselt and Reynolds numbers is the exhaust port diameter.