Temperature and void fraction distribution in a side wall heated tank

• Main Authors: Aszodi, Attila, Krepper, Eckhard
• Other Authors: Forschungszentrum Rossendorf, Institut für Sicherheitsforschung
• Format: Others
• Language: English
• Published: Forschungszentrum Dresden 2010
• Online Access: http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30102; http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30102; http://www.qucosa.de/fileadmin/data/qucosa/documents/3010/3068.pdf

Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. Storage tanks for fluids are widely used industrial facilities. 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 boiling tests with water tanks were performed both with heating from the bottom and with heating from the side walls. In different test tanks for the different heating modes the time dependency of the temperature field was determined by thermocouples. In recent tests for investigation of the side wall heating, in addition to the thermocouples the tank was equipped with needle probes for measuring of the local void fraction. The experiments have shown that the liquid inventory behaves very differently depending on the mode of heating. Bottom heating leads to an irregular thermoconvective motion of the liquid, which causes good mixing, so that saturation is reached at all places inside the tank approximately at the same time. The maximum enthalpy of the liquid always remains close to the average value. If the vessel is heated from the side, a stable temperature stratification is observed leading to large temperature gradients. Evaporation can start much earlier than the average temperature reaches saturation. In order to clarify the physical nature of the details of the heating-up and the evaporation process in simple geometrical boundary conditions, a two-dimensional mathematical model was developed, which includes also evaporation and two-phase flow. The measurement of the temperature and of the void fraction makes physical phenomena evident, which could be explained by the own 2D model. The gained experimental results may be used for the validation of boiling models in 3-D CFD codes.