Fuel efficiency for tractor/trailer combinations continues to be a key area of focus for manufacturers and suppliers in the commercial vehicle industry. Improved fuel economy of vehicles in transit can be achieved through reductions in aerodynamic drag, tire rolling resistance, and driveline losses. Fuel economy can also be increased by improving the efficiency of the thermal to mechanical energy conversion of the engine. One specific approach to improving the thermal efficiency of the engine is to implement a waste heat recovery (WHR) system that captures engine exhaust heat and converts this heat into useful mechanical power through use of a power fluid turbine expander.
Several heat exchangers are required for this Rankine-based WHR system to collect and reject the waste heat before and after the turbine expander. The WHR condenser, which is the heat rejection component of this system, can be an additional part of the front-end cooling module. Packaging this WHR condenser as part of the front-end cooling module can be an engineering challenge given the tight underhood environment where the current powertrain cooling components are already near system-capable thermal limits.
This paper shows how Lattice Boltzmann Method based simulations using highly-detailed vehicle geometry were utilized in the development of the heat exchanger architecture used to meet peak cooling needs as well as provide sufficient cooling airflow to the WHR condenser under all operating conditions. Heat exchanger results from the simulations are shown to compare well to cooling test measurements in a fully-climatic vehicular wind tunnel.
