Multiple Heat Exchangers for Automotive Systems - A Design Tool

A single radiator cooling system architecture has been widely applied in ground vehicles for safe equipment (e.g., engine block, electronics, and motors) temperature control. The introduction of multiple smaller heat exchangers provides additional energy management features and alternate pathways for continued operation in case of critical subsystem failure. Although cooling performance is often designed for maximum thermal loads, systems typically operate at a fraction of the peak values for most of their life cycle. In this project, a two-radiator configuration with variable flow rates and valve positions has been mathematically modelled and experimentally validated to study its performance feasibility. A multi-node resistance-capacitance thermal model was derived using the ε−NTU approach with accompanying convective and conductive heat transfer pathways within the system. This engineering model provides an analytical description of the system behavior that can be leveraged for engineering studies including initial radiator sizing and thermal management system (TMS) design. To demonstrate the concept, the EPA urban and highway driving cycles were used for low and high thermal loads. In the numerical study, the twin radiators dissipated 10% more heat in both driving cycles when compared to single radiator for equivalent surface areas. Further, operating one of the two smaller radiators with reduced thermal loads led to a 56% drop in energy consumption as compared to the single radiator solution due to fan and pump operating adjustments. This research established an engineering path for multiple radiators in a cooling system design configuration to actively control heat dissipation.