Application of exergy balances for the optimization of non-adiabatic small turbomachines operation

► This paper deals with current problems concerning the performance optimisation of engines. ► It addresses the influence of heat transfer on small-scale machines such as turbochargers micro gas turbines. ► More representative parameters (entropic temperature, exergetic analysis) for non-machines are introduced and used to assess performance. ► Turbomachine characteristic curves taking into account heat transfer are established. ► The performance generally given in adiabatic maps is found to be overestimated.