Peter Schütz
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TOPFLOW pressure tank

The pressure tank is one of three test rigs of the TOPFLOW facility that was commissioned in 2005. It is a horizontal cylindrical tank with an inner diameter of 2.4 m and an useable length of 6 m. One front side can be closed with a spherical cover. Inside the pressure tank different horizontal test sections may be used in pressure equilibrium with the tank atmosphere. Thus it is possible to prepare it by thin-walled stainless steel sheets and include large-scaled glass windows if required. So, optical observation of the flow structure inside the test section is possible. Furthermore an infrared camera can be used to determine temperature fields at the test section surface.

The TOPFLOW pressure tank can be operated at pressures up to 5 MPa and inner temperatures of maximal 50 °C, so that as air/water- as steam/water experiments are possible. Steam tests may be conducted up to the saturation temperature of maximal 264 °C. For this reason an effective thermal insulation of the outer test section surface is necessary, to avoid overtemperatures in the tank. However, heat losses appear, wherefore the pressure tank is equipped with a cooling system that releases overheat from the tank atmosphere into the environment.

Bild TOPFLOW Drucktank

TOPFLOW Stickstoff Anlage

TOPFLOW pressure tank with installed test section

High pressure nitrogen supply system

Additionally the tank is equipped with a steam feeding connection that is designed for the maximal steam mass flow of the facility. The steam tests require a condenser, which reliably condenses the residual steam after test section operation and at the same time ensures the pressure equilibrium with the tank atmosphere.

Furthermore the tank is equipped with two circulation loops, which are designed also for pressures up to 5 MPa and temperatures of maximal 264 °C. In it water can circulate with volume flows up to 40 and 7 m³/h respectively. The liquid in the loops can be either cooled or heated-up by steam or electrical energy. Two further connections of the tank are used as feeding and drain line. They can be applied as for cold- as for saturated water from the TOPFLOW facility.

To increase the pressure in the tank, two gas supply systems of the TOPFLOW facility can be used alternatively: On the one hand a three-stage compressor unit pressurizes the total tank volume of app. 33 m³ up to 5 MPa in 5 hours. It is applied for tests at ambient temperatures. On the other hand a high pressure gasification unit fills the tank with nitrogen during steam tests for safety reasons.

For the communication of measurement sensors inside the tank with corresponding non pressure-proof electronic devices outside, licensed printed board flanges with various connections (e.g. Gbit LAN) and two flanges with a total of 28 thermocouple bushings are available. Additionally three glass windows in the tank wall may be used for visual inspection of the test section during operation or e.g. for the transmission of light by optic fibers.

Since the erection of the TOPFLOW pressure tank 3 test units were assembled, equipped with measurements and commissioned:

HSM Versuchsstand

A horizontal test section for investigation of co- and counter-current flows in a model of a hot leg and a steam generator inlet chamber of a pressurized water reactor (TOPFLOW-II project);

PTS Versuchsstand

A test rig for the investigation of pressurized thermal shock phenomena in a model of a downcomer (nuclear reactor vessel) with cold leg and pump simulator (TOPFLOW-PTS project) and

DENISE Versuchsstand

A test basin for the investigation of flow pattern, heat transfer and condensation effects at free surfaces and on an impinging jet (DENISE in the frame of the TOPFLOW-III project).

The first and second test section provided data for nuclear safety research, whereas the experiments in the test basin yield in generic data for general understanding of the flow phenomena. All data are available for CFD model development and code validation.

In the course of project realization a pool of technological solutions were developed and applied:

  • pressure-proof containers for the operation of high speed – and infrared cameras with forced convective air cooling and the required cable communication;
  • thermal insulation of plane and curved surface areas for the application at pressure tank operating conditions;
  • licensed printed board flanges with various shielded bushings;
  • powerful pressure-proof LED light sources for high speed camera capturing and
  • pressure-proof electronic device for fast recording of up to 200 thermocouples type K.