Power and cogeneration plants can offer flexibility for plant operators by including control components such as diverter valves in the early design stages to reduce the economical impact of purchasing power during overhauling periods. Sometimes engineers or owners decide to exclude these components from the project outset, in their intention to reduce investment, but as time goes by it is realized that shutting down the plant and purchasing power represent a non economical operational strategy. This paper presents a case study for a combined cycle cogeneration plant that plans to integrate a diverter valve in the gas turbine - heat recovery steam generator transition to allow the switching between combined cycle cogeneration and Brayton power cycle. The selected valve is already prepared with silencer and stack but it's larger in size than the plant equipment connections. Moreover, there is space limitation and therefore connecting ducts are aggressive barriers to the exhaust gas flow; making the evaluation of both cycle performances an important challenge. The analysis is conducted by combining power and heat cycle simulations with computational fluid dynamics.