Investigation on Underhood Airflow Management - Effect of Airflow Statistics

The objective of this work is to examine the suitability of cooling airflow non-uniformity on radiator frontal surface as a factor to evaluate three attributes: airflow distribution, front fascia geometry and deterioration in heat rejection. In literature, the effect of front end design is investigated by evaluating the volume of cooling airflow passing through the radiator and cooling drag of a vehicle. In this study, it was demonstrated that airflow distribution on radiator frontal surface can also be considered as one of the parameters while choosing the front-end design. Using the basic equations for modeling the cooling airflow through a front-end opening, CFD approach is developed to quantify the airflow distribution over the heat exchanger(radiator) as a function of flow statistics of the upstream cooling air. Further, this work is extended to study the impact of airflow non-uniformity on the thermal performance of radiator using the empirical equation available in literature. The airflow non-uniformity was found to be sensitive to changes in the geometry of fascia particularly around the upper cooling inlet. This study reveals a vehicle level system trade-off between grille opening, cooling air mass flow rate and non-uniformity at design stage itself. The interpretations of this work can serve as a design guideline for the thermal system and styling engineers of automotive domain.