Electrical steam generator
An electrical steam generator with forced circulation is used for steam generation required for the experiments at TOPFLOW facility.
It consists of 24 parallel heating tubes made of stainless steel with a length of approx. 20 m, an inner diameter of 16 mm and a wall thickness of 2 mm. The heating tubes weigh emptily approx. 0.5 t and may have a fluid volume of approx. 0.1 m³. They are heated by direct electrical resistance. The capacity of the steam generator can be controlled into 9 modes between 0.5 and a maximum of 3.9 MW.
The 24 tubes are connected to one inflow and one outflow collector with an inner diameter of 80 mm. To get a regular flow through the heating pipes, throttling orifice plates are fit at the entry of the tubes (borehole Ø = 2.3 mm). In order to avoid a pollution and blockage of these plates (and heating tubes), a filter with a porosity of 2 mm was installed outside the inflow collector.
The energy required for heating is supplied of one oil cooling 6 kV/80-140 V three-phase transformer with a special switch. This transformer is connected via a set up separately 20 kV/6 kV transformer with the net of FZD.
Electro heater and switched transformer form an assembly with a width of 3.8 m, a length of 4.8 m and a height of 2.3 m. The total weight amounts approx. 20 t, where 15 t account for the transformer (including 2.8 m³ oil) and 5 t account for the electrical steam generator including the steel construction and the oil pan.
In addition, the steam generator is surrounded with an electric shock protection made of aluminum sheets. An air exhaust duct contained over the electrical steam generator carries off the heat losses to the environment.
It is equipped with a series of safety shutdown circuits. On the one hand, every individual heating tube is checked to its maximal temperature with each two thermocouples isolated from the heating pipe electrically. On the other hand, a flow meter, and differential pressure check systems are installed at the steam generator, as well as absolute pressure measurements in both collectors. In addition, the transformer is controlled in accordance with the safety-related requirements.