A Novel Integrated Cooling and Heat Recovery System Using Organic Rankine Cycle for Diesel Engines

Diesel engines offer at least two sources for heat recovery, namely, engine coolant and exhaust gases. The continued trend of cooler engine intake temperatures and engine downsizing now means that the charge air cooling has additionally become a noticeable load on the engine cooling module. There exists key challenges in integrating multiple heat sources, and hence, heat recovery has been typically suggested as an add-on solution using either high temperature heat (i.e. exhaust gases) or low temperature heat (i.e. engine coolant). This paper proposes a novel process integration, termed, the dual process system, to recover exhaust heat and also provide cooling for the charge air. This system is a function of innovative approaches in system architecture (non-isothermal cascade condenser, liquid expander), working fluids (water-organic zeotrope, environment friendly refrigerant) and cycle operation (trilateral flash cycle). The system is simulated using an advanced chemical process modelling tool, Aspen HYSYS. As a case study, steady-state heat recovery was considered at the rated condition from a 12.8 litre engine model. Simulation results showed that the use of the dual process system on new engine platforms can potentially offer 7.2% of additional engine crankshaft power. This corresponded to a 55% increase in power generation compared to the two conventional independent heat recovery cycles targeting the high temperature and the low temperature heat sources.