Methodology to design a bottoming Rankine cycle, as a waste energy recovering system in vehicles. Study in a HDD engine

► A study for the optimization of a bottoming cycle for recovering various waste heat sources is presented and applied in a HDD engine. ► Water and R245fa are selected as working fluid in the proposed solutions. ► The cycles with water as working fluid produces a higher power output than the solution with R245fa in almost all the operative points. ► The cycle with R245fa as working fluid is the most feasible solution from the point of view of space requirements. ► The effect of the expander machine irreversitibities is discussed.