he THERESA experimental plant is equipped with two upright U-tube preheaters, which are used for feedwater preheating. The task of the preheaters is to raise the temperature of the feed water to a certain temperature level, independent of the feed water mass flow. In this process, the cold feedwater flows through a U-tube register and is heated by steam flowing into the shell space. In this process, the steam feed is completely condensed and the condensate is additionally subcooled. Due to the adjustable condensate level, the target temperature at the register outlet and thus the heat output can be set almost at any desired level.
The steam generator is used for the production and storage of saturated steam and for maintaining pressure in the system. For possible examination of internals, the cover and bottom flanges are designed to be demountable. In connection with the bottom flange, an electric immersion heater with a heating capacity of 200 kW is installed for steam generation. The steam generator operates as a power-to-heat storage unit. It has a volume of 1 m³ and is equipped with 12 universal measuring levels for experimental process investigations as well as 5 central temperature measuring points in axial arrangement over the height. For the optional provision of superheated steam, a controllable electric superheater is connected downstream of the steam generator.
The core of the storage system is a sensitive heat accumulator in the form of a displacement storage with a mixing preheater. This operates as a thermal battery and is designed for process conditions up to max. 60 bar and 350 °C. The accumulator is charged and discharged with saturated water and hot water, which is provided by the mixing preheater by combining superheated steam or saturated steam and feed water. For temperature measurement, 11 axial measuring planes with 6 radial positions each are integrated in the displacement accumulator. The mixing preheater has 3 temperature measurements in axial direction. Due to the availability in thermal industrial plants, the cycle stability and the possibility of direct heat storage, deionized water is used as storage medium.
A discharge vessel with cooling system is used as a heat sink. The main tasks are the condensation of steam, the collection of hot deionized water and active cooling if required. The dissipated heat is utilized in the district heating system of Stadtwerke Zittau.