Experimental and numerical investigation of one and two phase natural convection in large pools

Natural circulation is a basic physical principle for a lot of industrial applications. The paper describes two examples of investigations of natural circulation phenomena. The first example is drawn from the task of the safety assessment of the danger of storage tanks of hazardous fluids under the influence of an external heat source. Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external. As a consequence of an external fire, the heat-up of the inventory may lead to the evaporation of the liquid and to release of significant quantities of dangerous gases into the environment. Several tests were performed both with heating from the bottom and with heating from the side walls. The paper presents experimental and numerical investigations of single and two phase heating up processes of tanks with side wall heating. The measurement of the temperature and of the void fraction makes interesting phenomena evident, which could be explained by an own 2D model.
The second example concerns with investigations of the investigation of passive heat removal systems in advanced designs of nuclear power plants. The heating up processes on the large pool on the secondary side of a test facility NOKO were analysed using the CFD code CFX.