Abstract

In recent years, R&D has undergone a real transformation and is being rationalized in order to increase its efficiency, reduce its development cycles and costs, and improve its capacity to innovate. Turned towards digitalization, Valeo Thermal Systems relies in particular on digital simulation such as CFD (Computational Fluid Dynamics) to optimize concepts, orient its technical choices, make decisions and engage with customers. Its use is becoming a major asset to offer innovative and competitive automotive heat exchangers. Cost of computational power decreases from year to year and it causes resources to be more accessible for different entities like: corporations, research institutes, universities, smaller companies etc... Despite this fact, car heat exchangers like radiators or intercoolers cooled by water or air, are still very challenging in terms of simulation. These heat exchangers have hundreds or even thousands of very small tiny parts called turbulators or fins increasing the area of heat exchange in a unit of volume. It causes that it is nearly impossible in reasonable time to mesh and simulate detailed geometry. As a simplification, special replacement models are used. Pressure drop is calculated using the so-called porous medium while heat transfer is carried out by the 3D heat exchanger interface model. Both models need input like porous medium pressure drop coefficients or local heat transfer coefficients. This article presents a new numerical method based on a CFD submodeling technique to characterize the pressure losses and the heat transfer coefficients from a small periodic pattern of the heat exchanger. Then, based on CFD submodeling results, special laws are built using dimensionless numbers such as Reynolds number, Nusselt number, Prandtl and Bejan number. Finally, these laws of pressure drop and heat transfer are applied to a full CFD model of the heat exchanger to predict its fields of temperature and flow with its performances.