Direct Condensation and Entrainment Installation for Steam Experiments TOPFLOW-DENISE: Stratified Steam Condensation Experiments

1. MOTIVATION
In a hypothetical Small Break Loss of Coolant Accident (SB-LOCA) in a Pressurized Water Reactor (PWR), the Reactor Pressure Vessel wall (RPV) may be exposed to thermal stress, since Emergency Core Cooling Systems (ECCS) injects cold water. The loads on the primary loop and RPV walls are determined by mixing processes with the surrounding hot water and by the condensation of steam on the surface (see Bestion 2010 and Lucas 2005)
For the development and validation of CFD-models, experiments have to meet a high standard of reproducibility, measurement certainty and temporal and local resolution. The pressure tank technology of the TOPFLOW facility allows conducting such experiments at reasonable effort.
2. TOPFLOW-DENISE FACILITY
The Direct Condensation and Entrainment Installation for Steam Experiments (DENISE) is made for CFD-grade condensation experiments at up to 50 bars pressure (see Figure 1). Subcooled water is injected into the DENISE-basin in three different configurations for experimental investigation:
A) Stratified flow
B) Subcooled water Jet
C) steam bubble entrainment with a jet falling on a stratified surface
The experimental facility is equipped with a dense instrumentation. The flow inside is observed and controlled with a high speed camera and an infrared camera, coriolis flow meters and a set of micro thermocouples. The facility is supplied with a 4 MW electrical boiler, saturated water pumps, a 30 kW electrical heater and a 2 MW water cooler.
3. FIRST EXPERIMENTAL SERIES
The first series contains stratified flow experiments comparable to non-adiabatic flow inside hot and cold legs of PWRs. Measurement results can be compared to CFD simulations. Recently 56 experiments have been carried out according to the test matrix in Table 1.
The observed high speed and infrared images from the reference experiment are shown in Figure 2. The surface is slightly wavy and a small increase of water temperature is observable between inlet (left) and outlet (right). Processed data from these measurements, like the temperature plots shown in Figure 3 will provide comparable results for the development and validation of CFD-models.
4. OUTLOOK
Experiments with stratified steam-water surfaces have been carried out in August 2013. They are being analyzed till end of 2013. For the next experiments, a jet injector will be added to the facility and plunging jet experiments with bubble entrainment will be measured. Finally, there will be experiments with a subcooled water jet falling through the steam atmosphere. A special movable thermo sensor will be used to measure temperature profiles inside the jet.