In this paper is described a heat transfer sub-model whose main objective is to help a global 1-D gas dynamic code to calculate reciprocal internal combustion engine performance in steady and transient operation.
From the point of view of heat transfer the engine is divided into four different zones that will show different calculation peculiarities: the intake line, the engine cylinders, the exhaust ports and the exhaust line.
The heat transfer sub-model has been programmed to deal with three different possibilities with respect the engine walls temperature: constant with time, variable but without thermal inertia considerations and variable taking into account walls thermal inertia.
In the paper, the main emphasis will be devoted to explain the temperature calculation of the engine walls, which are mainly ducts in the 1-D calculation codes. In these walls, only radial heat transfer is considered. To solve the computation of this radial heat flux through them, three calculation nodes have been used: one in the inner side, other in the middle and the last one in the outer side of the walls.