Engine heat transfer

The peak burned gas temperature in the cylinder of an internal combustion engine is of order 2500 K. Maximum metal temperature for the inside of the combustion chamber space are limited to much lower value by a number of consideration, and cooling for the cylinder head, cylinder liner, and piston must therefore be provided. These conditions lead to heat fluxes to the chamber walls that can reach as high as 10 MW/m2 during the combustion period.
Heat transfer affects engine performance, efficiency and emissions. For a given mass of fuel within the cylinder, higher heat transfer to the combustion chamber wall will lower the average combustion gas temperature and pressure, and reduce the work per cycle transferred to the piston.
Modes of heat transfer:
1. Conduction:
Heat is transferred by conduction through the piston ring to the cylinder wall, through the engine block and manifolds.
2. Convection:
Heat is transferred through fluid in motion and between a fluid and solid surface in relative motion.
Heat is transferred by forced convection between incylinder gases and cylinder head, valves, cylinder walls and piston during induction, compression, expansion and exhaust strokes.
Heat is transferred by forced convection from the cylinder walls and head to the coolant and from the piston to the lubricant or other piston coolant.