The energy and the exergy performance of a dual-loop Organic Rankine Cycle (ORC), which harvests exhaust heat from a two-stroke slow-speed main marine diesel engine of a bulk carrier is examined herein. An energy analysis is adopted to calculate the energy flows to the components of the high-temperature (HT) and the low-temperature (LT) loops of the bottoming ORC and through them, to calculate the energy efficiency of the ORC and the generated power from both expanders. Also, an exergy analysis is implemented to predict the irreversibility rates of the components of both HT and LT loops of the ORC system. Various organic fluids are examined for the HT and the LT ORC loops and the optimum combination is selected based on the results of a parametric analysis. The effect of ambient conditions on the energetic and exergetic performance of the dual-loop ORC is examined. The energy analysis of the bottoming dual-loop ORC is projected to a specific mission operational profile of a bulk carrier for predicting the benefits in fuel cost saving and CO2 and SO2 emission reduction compared to conventional vessel operation.

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