The internal energy of which body decreases during the operation of the turbine model?

A steam turbine is a heat engine with a continuous process of sequential conversion of the energy supplied by the working fluid into the mechanical energy of the turbine rotor rotation. In general, a steam turbine unit (STU) operates in a closed cycle. A steam generator is a heat exchanger designed to convert the “fuel” energy supplied from outside into thermal energy of the working fluid. Fuel energy is supplied from the outside due to fuel combustion, part of the energy is spent on losses to the environment, therefore, the internal energy of alcohol decreases.