This graduation thesis is concerned with a thermal exchange unit issue whereof one working substance complies with a two-phase mode of a flow. This unit is made for the steam generation. The thesis is supposed to solve operation problems causes of the given unit and to make a proposal of an appropriate solution that is supported by performed calculations. Part of the the work is strength calculation. This work also introduces the thermal-hydraulic processes issue of the steam generation equipment. There are also performed thermal-hydraulic control calculations in consideration of newly set-up operation parameters of the given equipment‘s working substances.