Conceptual Design and Preliminary Testing of an Organic Rankine Cycle Thermal Architecture

Waste heat recovery is a key path in improving the overall thermal efficiency, and hence, reducing CO2 emissions in the mid to large scale internal combustion engines. However, realisation of the cost-effective deployment of Organic Rankine Cycles (ORC) are hindered by several key factors. Amongst these are the, utilisation of low-grade ORC practice for high-grade applications, disconnect between parameters considered in simulation studies to those demonstrated experimentally, and integrating multiple heat recovery sources.
To investigate and address these challenges, a programme of ‘concept-to-demonstration’ is in progress at the University of Brighton. This paper describes some of the key features of a new ORC test facility that can contribute towards reduced system costs and increased overall conversion efficiency. These features include, firstly, a variable heat source setup, allowing the potential to replicate a wide range of realistic gaseous heat source quality and quantity levels. Secondly, the direct utilisation of the High-Temperature (HT) exhaust gases, which is expected to reduce the overall system cost when compared to a system utilising an intermediate thermal-oil loop. Thirdly, deployment of HT blends, this is estimated to increase the overall conversion efficiency when compared to a system employing a conventional organic working fluid. Fourthly, a flexible thermal architecture, offering a dual source heat recovery for effective heat utilisation and internal heat recuperation for increased thermal efficiency. Finally, the HT and high-pressure cycle operating capability, offering a near-optimal process condition. The potential benefits of the above features are quantified using a combination of literature survey, simulation results and experimental measurements. The paper concludes with a brief overview of the research direction intended to be undertaken in the next phase of the work.