A Model for Application of Chen’s Boiling Correlation to a Standard Engine Cooling System

With the increase of specific power, in development of modern engines, also the demand on the cooling system has significantly increased. CFD analysis reveals the occurrence of localized boiling, since often the measured temperature distribution cannot be explained by convective heat transfer alone. The requirement for highest heat transfer rates has led to the very promising concept of a controlled transition from pure convection to subcooled boiling in the critical thermal conditions. However, computational fluid dynamics is still unable to represent boiling flow, while any boiling based strategy requires a right prediction of heat transfer rates on the coolant surface inside IC engines. Chen's heat transfer model for boiling region is widely used today, to predict and compare the predicted heat transfer coefficients in circular and rectangular ducts with experimental results. In spite of this, it's very difficult its application to IC engines cooling passages where the definition of an hydraulic diameter for the model is very impractical.The present work proposes a new application model that, leaving every experimental aspect but taking advantage only from CFD analysis, solves the problems connected with direct application of Chen's model to coolant passages inside an IC engine. This model has been applied to the cylinder head of a 1.4 L 4-cylinder 16-valve Turbo SI engine.The predicted wall temperatures are found in overall agreement with experimental data.