This paper presents a CFD-based optimization workflow for the simulation and
development of automotive cooling circuits, integrating three-dimensional
steady-state analyses with one-dimensional transient modeling. The objective of
the activity is to establish a robust methodology that links detailed
component-level thermal characterization to system-level dynamic simulations,
enabling the assessment of cooling performance under both driving and charging
operating conditions.
The thermal behavior of the cooling circuit components was first investigated
using three-dimensional steady-state simulations performed with Ansys Fluent.
For each relevant operating point, the fluid flow and heat transfer were
resolved in full 3D, and temperatures were monitored at multiple locations
within the components and along the circuit. The steady-state analyses provided
spatially resolved temperature fields and heat transfer characteristics for a
range of boundary conditions representative of real operating scenarios. From
these results, temperature and performance maps were generated, describing the
relationship between operating conditions, heat loads, and thermal responses of
the components.
These maps were then used for the calibration of one-dimensional models
implemented in GT-Suite. The calibrated 1D models reproduce the thermal behavior
observed in the 3D CFD simulations while allowing efficient simulation of the
entire cooling system under transient conditions. This multi-level approach
enables the combination of detailed local physics from CFD with the
computational efficiency required for system-level dynamic analyses. Transient
simulations were carried out in GT-Suite to evaluate the thermal response of the
cooling circuit during both driving and charging phases. The driving phase
accounts for variable thermal loads and flow conditions associated with vehicle
operation, while the charging phase represents operating conditions specific to
battery recharging scenarios. The calibrated 1D models were used to simulate the
evolution of temperatures throughout the system over time, considering the
interactions between components and the overall thermal inertia of the
circuit.
The results show that the designed cooling system is capable of maintaining
component temperatures within the targeted limits across the analyzed operating
conditions. The thermal containment is achieved for all components included in
the cooling circuit under both dynamic driving and charging scenarios. The
electric motor is oil-cooled and therefore is not part of the water-based
cooling circuit addressed in this study.
The proposed CFD-to-1D workflow provides a consistent and transferable
methodology for the thermal development of cooling systems of high power density
electrified powertrains. The novel contribution lies in (i) the application of
the multi-level framework to a heavy-duty platform with SiC-based power modules
and dedicated on-board charger developed within the Horizon Europe POWERDRIVE
project, (ii) a DOE-based map generation strategy that preserves the conjugate
heat transfer interactions between actively cooled components (power modules,
OBC) and passively cooled neighbors (busbar, capacitors) within the
reduced-order representation, and (iii) the integration of the reduced-order
maps within a single transient system-level model covering both vehicle-at-rest
charging and dynamic driving operating modes. This activity is carried out
within the framework of the Horizon Europe project POWERDRIVE.