Assessment of Rankine Waste Heat Recovery Potential on Heavy Duty Trucks Using Direct Condensation

orc2019 Tracking Number 218

Upcoming regulations on CO2 emissions for the heavy duty truck industry [1] and increasing fuel prizes lead the truck manufacturers to adopt new solutions to reduce fuel consumption. The organic Rankine cycle (ORC) is a promising technology to achieve such a goal. Rankine cycle waste heat recovery on heavy duty trucks has been studied in the last decade focusing on fluid selection [2], modelling [3], control and component [4] development. Cost, integration and uptime are also considered as important aspects for a future series production. The objective of this study is to evaluate the performance of a Rankine system by means of road cycle simulations on a complete truck simulation environment (Exhaust after treatment system, as well as cooling system and the energy management of the mild-hybrid driveline are modeled). The Rankine uses exhaust gas flow as heat source, direct condensation radiator as condenser and volumetric expansion machine; selected working fluids for this study are ethanol and cyclopentane. Dynamic equations used for the modelling of the Rankine components are provided and a particular attention is dedicated to the model of the condenser and fan. In order to ensure the complete condensation of the working fluid two controllers are implemented to track a setpoint on subcooling at the outlet of the condenser by acting on the fan speed and condensation pressure. Results show that ethanol is more suitable than cyclopentane using direct condensation and the limitation of the fan power demand can lead to an increase of the Rankine net power.