Experimental Research On Mixing And Thermal Stratification Inside A Large Space

Thermal stratification is a phenomenon which often occurs in a large space with internal heat source. For the condition of break accident happens in pressurized water reactor, such as LOCA or MSLB, thermal stratification is likely to happen inside the containment space. This phenomenon has great influence on the performance of the heat dissipation from the containment to the environment. For the AP1000 reactor, the passive containment cooling system is a very important way of releasing heat to the environment. It’s important to accurately predict the temperature and density distributions inside a large space for both design and accident analysis.For thermal stratification phenomenon occuring inside the AP1000 containment, based on conservative assumptions, and analysis of test data obtained by international thermal test bench, especially LST, Westinghouse draw the conclusion that the influence of the phenomenon can be ignored in AP600/1000 reactor. But excessive conservative assumptions mean the more investment, and it’s still an unavoidable problem to develop new reactor with more thermal power.At present, the analysis of the temperature field inside the containment is mainly rely on some calculation software like CFX and FLUENT, and problems such as poor calculation accuracy and long computation time exist in most of these softwares, which need to be improved. For the assessment of the reliability of the software and ^the extension of the applicable range, as well as the development of a new calculation model with more accuracy, the test data is necessary as a significant technical reference.The design of the experimental facility and the scaling analysis is introduced in the paper. Through the research of other thermal test benches, the height of nozzle, the diameter of nozzle, the nozzle position, jet angle, the temperature of the jet and flow rate, these six factors were focused by investigation and research. Experiment under the condition of containment exposed to the environment and covered by adiabatic material, is done respectively in the experimental facility. In addition, this article also did study on the influence of the layout of different compartments inside the containment on thermal stratification. By test data obtained from the experiments, the analysis of these factors, some qualitative conclusions are obtained and the empirical heat transfer formula is fitted by the data, which provides some reference for the development and improvement in the future.