Robust optimization of an Organic Rankine Cycle for heavy duty engine waste heat recovery

A robust parametric optimization of Organic Rankine Cycles (ORC) is carried out by taking into account uncertainties in the cycle input parameters. A typical engine driving duty cycle is considered and sampled in order to construct a suitable probability distribution describing the variability of the exhaust gases mass-flow and temperature. Besides, the environmental and condensing temperatures, specific heat ratio of the waste gases, turbine and pump efficiencies are also considered as uncertain. The parameter combination that maximizes the mean cycle efficiency and minimizes its variance is sought as optimal. Six organic fluids have been taken into account, namely R245fa, R245ca, R134a, R11, R113 and Novec649, with the best results provided by R11 and R113.