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DITEFA (DIvertor TEst FAcility) is a small multipurpose liquid metal test facility for thermo-hydraulic investigations related to solar, fusion and nuclear energy. Currently, DITEFA is under construction and scheduled to be online in 2016. For the first experimental campaigns, the focus is on the flow in vertical rectangular channels. Thereby, the transition from forced convection to free convection will be studied. The transition between the different flow regimes is important due to its impact on the safety and general operational performance of a plant or a facility. During start-up or shut-down phases, as well as during accidents, it is possible to have a disbalance between heat production and heat removal. Such a scenario can occur if, e.g., the pump fails while the heat source cannot be switched off in a timely manner. Therefore, it is important to assess the natural circulation capabilities of the plants or facilities in order to demonstrate that enough flow can be established to maintain a minimal heat removal to protect exceeding temperatures. The information concerning the descripted scenarios is sparse which makes it necessary to perform comprehensive experimental studies. That is also the reason why numerical tools have major problems when dealing with transitional flow and heat transfer regimes. To improve CFD and system codes and their models, experimental data must be provided. Besides the general transition between the flow regimes it is important to obtain information on a smaller scale. As mentioned before support for the development and improvement of numerical tools will be given. Thereby, detailed information on the velocity and temperature fields is eminent. In the present case, measurement devices consisting of thermo-elements in connection with small strong permanent magnets are inserted into the flow. The cross section of that device is in the range of 2 mm and does not perturb the flow (at least keep the perturbations minimal). By means of the Ohms law it is possible to obtain velocity information directly from the thermo-elements due to the electrical conducting liquid metal coolant. In addition to the temperature and velocity information on a global and a local level, qualitative and quantitative statements concerning the velocity as a function of the transition time and the flow regime will be made. Furthermore, operational guidelines can be developed for a safe operation of facilities during flow regime transition. With the help of the information gained during the experiments it is not only possible to improve numerical tools, but this information is also of great value for the future designs of experimental facilities or real plant components [1].


[1] Wadim Jaeger, Wolfgang Hering, Florian Trimborn, Balazs Pritz and Martin Gabi, “Thermo-hydraulic investigation of a vertical rectangular duct with liquid metal flow by means of system and CFD code predictions” Proceedings of the International Congress on Advances in Nuclear Power Plants 2016, San Francisco, U.S.A., 2016 [under preparation]