Improving 1D simulations of thermal management systems with embedded 3D CFD

Abstract

1D simulation tools have been proven to be very powerful and efficient when dealing with sophisticated cooling systems. They allow thermal analysis of engine cooling or air conditioning systems that incorporate several different components such as radiators, condensers, evaporators, thermostats, coolant pumps, batteries and different cooling cycles. A drawback is the limited simulation of the airflow distribution within a cooling module, as illustrated in figure 1. Simulating the flow through a setup with an obstacle and a heat exchanger in 1D would lead to multiple independent flow paths. However, the obstacle would block the path completely, see fig. 1b, since the flow around the obstacle cannot be considered, due to the path segmentation, see fig. 1c. This can partially be compensated by a pressure loss element for the obstacle or by an inflow profile. But these approaches are still limited, provide only a rough estimate and they are error prone, since the necessary parameters are usually not known and profiles must be measured, pre calculated or extrapolated. This leads to more constraints on the simulation and becomes worse considering a real module. The engine, pipes, bumper, crossbars, shroud, fan, header etc. all interact with the flow field and might result in flow separation, cross flows, increased mixture, recirculation and pressure drop etc., see fig. 1d. For a non trivial case a 3D CFD simulation is necessary to fully consider all relevant effects.