In this paper we determine the fundamental relation between global performance and flow configuration (constructal design) in the case of steam power generation with superheater and reheater placed in parallel in the same stream of hot gases of combustion. The superheater heats the steam for the high pressure turbine, and the reheater supplies steam to the low pressure turbine. Both turbines operate irreversibly. We consider superheaters and reheaters with balanced counter flows and unbalanced counter flows. The total heat transfer area (or the overall number of heat transfer units) is finite. We show that the heat transfer area can be allocated to the superheater and reheater such that the overall power output is maximum. The optimal area allocation ratio is reported for two scenarios: designs with and without a maximum allowable steam temperature. (C) 2014 Elsevier Ltd. All rights reserved.