Test section circuit
The task of the test section circuit is to investigate the evolution of flow structure, void fraction profiles, bubble size and gas velocity distributions, as well as coalescence and fragmentation effects of bubbles in stationary and transient two-phase flows (air/water or steam/water). In addition, the steam drum can be used for component tests and investigations of thermo-hydraulic phenomena in big water pools under high pressure and temperature conditions.
The test section circuit connects the vertical test sections in different designs with the steam drum and the test section pump.
One design of the test sections is the so-called Variable Gas Injection System illustrated in the figure. The Variable Gas Injection consists of a test section with a nominal diameter of 200 mm in which at 18 different height positions gas or steam can be injected through orifices in the wall with diameters of 1 and 4 mm, respectively. The injection chambers which are supplied with air or steam via a gas riser can be blocked separately.
In addition, experiments on "Vertical test sections" with nominal diameters of 50 mm and 200 mm have been performed in order to investigate the wall's influence on the flow design.
During execution of test section experiments, the steam drum serves as a water reservoir, as well as for the separation of the air/water or steam/water mixtures coming from the test sections. Additionally, during condensation experiments, the steam drum of the test section circuit can be used as buffer to stabilise the steam pressure in the condenser bundle.
The water mass flow necessary for execution of the experiments is sucked from the steam drum by the test section pump and injected into the lower part of the test sections. Each of them can be blocked separately. The adjustment of the water mass flow in the range between 0.05 and 50 kg/s is carried out by means of three parallel arranged control valves and with the help of the test section pump, which is controlled by a frequency converter. The injection of the gaseous phase also takes place in the lower part of the test sections using exchangeable injection heads. Different injection heads allow a variation of number and size of the injection nozzles. Therefore, different forms and sizes of steam and gas bubbles can be produced.
The steam required for the experiments is generated in the electrical steam generator circuit, separated by the separator and led via a steam line to the injection heads. The control of the steam mass flow is carried out with two control valves, which allow an adjustment in the range between 0.03 kg/s and 1.5 kg/s.
The air volume flow rate required for the execution of air/water experiments is provided by the compressed air system.
To protect the test section circuit against overpressure, a safety valve opening at 8.4 MPa is installed. The pressure in the circuit is adjusted by a blowing off system from the steam drum into the blow off tank by means of two control valves.
Filling the circuit with fully desalinated water is carried out with the feed water pump.