Investigation of an ORC System with Integrated Phase Change Engine Cooling

orc2019 Tracking Number 145

The CO2-emissions of on-road vehicles have to be reduced significantly in the upcoming years in order to achieve overall climate goals. ORC applications are an interesting option to contribute to these goals. Due to the high fuel consumption and mileage of long haul trucks they are of special interest for ORC systems since a long time. The upcoming CO2 limits for these vehicles in the EU are an additional driver for this combination. The main reason why ORC systems have not been introduced into the market so far is the very ambitious goal of the shipping companies to achieve a return of invest of these systems within two years. To reach this goal, future systems will have to be either cheaper in production or perform better fuel economy. IAV found an approach to achieve the latter one. Current ORC systems for long haul truck application make use of so far wasted exhaust or exhaust and EGR heat. Another big source of wasted heat, the engine cooling was not in the focus so far, as this energy is only on much lower temperature level available, which has negative impact upon the recuperation efficiency. This drawback can be overcome by replacing the conventional liquid convection cooling by a high temperature phase change cooling system. As this system is integrated into the exhaust heat ORC circuit it promises several advantages at the same time: more heat recuperation, less wall heat losses, and higher exhaust gas temperatures. Due to the integration in the ORC circuit, it does not need additional components but replaces some of them which at the end leads to a much better performance to cost ratio. In a detailed simulation study based on GT-power and Matlab/Simulink models IAV has investigated the potentials of such a combination at three characteristic load points, accompanied by a detailed loss split analysis. In addition also the impact of phase change cooling upon NOx-emissions has been evaluated. As a result it can be said, that the results underline the theoretical potential of this combination in an impressive way.