Numerical and experimental investigation of heavy-duty EGR cooler thermal performance

Abstract

Exhaust Gas Recirculation (EGR) cooler is a crucial automotive heat exchanger that decreases the temperature of the recirculated exhaust gas fed to engine cylinders to reduce the NOx emissions. The high temperature gradients in the heat exchanger and its varying hot and cold operation makes it necessary to accurately determine the temperature distribution of the EGR cooler to evaluate vulnerability to various thermal failures. This study demonstrates a thermal assessment of EGR cooler using detailed CFD simulation methods developed and validated with comprehensive experimental design and measurements. The experimental data including detailed boiling detection is collected on a gas burner test bench for eight different working conditions of the EGR cooler with conditioned cooling with an average of 3% repeatability error. The detailed and highly resolved CFD model which includes the heat transfer enhancing features of the heat exchanger is validated at these working conditions and resulted in an average of 1% difference in temperature and maximum 5% difference in pressure drop values. The developed detailed CFD methodology reduces the amount of EGR performance and boiling tests significantly and enables assessment of the EGR cooler at engine assembly conditions which affects the hot gas distribution and resulting temperature gradients. Furthermore, the CFD methodology and its correlation with the experiment proved that a coupled CFD methodology can be used instead of the development tests for analytical sign-off purposes as long as the detailed heat exchanger design is included in the CFD model. • A detailed CFD model with all geometrical features was built as essential alternative to EGR cooler tests. • The detailed CFD model does not require any additional numerical approach for pressure drop or heat transfer. • Acoustic Emission sensor was utilized for the more precise assessment of boiling level. • CFD predictions were validated with experimental data by using acoustic emission sensor measurements. • Predicted temperature and pressure change were validated by experimental results with high accuracy.