Theoretical investigation of water vapour condensation in presence of noncondensable gases
Steam condensation phenomenon plays an important role in many industrial applications. Especially in energy sector this process requires deep understanding. When noncondensable gases are taken into consideration description of the entire phenomenon becomes more complicated. If the surface condensation is taken into consideration this additional species accumulates and creates noncondensable layer near the surface on water vapour condenses. Due to this effect heat and mass transfer rates from gas mixture decreases. Also volume condensation (if it occurs) is affected by the presence of inert gases.Several examples where the phenomena described above are important can be taken into consideration: studies of accidents in the nuclear power plants where condensation in the volume and condensation on the cold containment’s structures occurs after steam is released due to the pipe brake in the primary loop (especially this is important for PWR’s containments which in normal operation conditions are filled with air or nitrogen); condensation of steam in the pipe systems of BWR reactors where some amount of hydrogen can be accumulated due to the water vapour condensation in nonvented pipes; condensation of steam in the condensers after low pressure stage turbine; etc. Also in other fields, e.g. chemistry or meteorology, the condensation of water vapour in presence of noncondensable species plays very important role.Diffusion surface condensation model and its implementation into CFX – 4 CFD code has been described in this licentiate thesis. Three different situations have been taken into account: surface condensation of water vapour in presence of air on the vertical wall (computational results have been compared with several commonly used correlations), surface condensation of water vapour in presence of air on the horizontal wall (results have been compared with experimental data), volume condensation in presence of air (known also as spontaneous condensation) – principle of the model has been described and calculation example has been presented and analysed.
School:Kungliga Tekniska högskolan
Source Type:Master's Thesis
Keywords:TECHNOLOGY; Technology; TEKNIKVETENSKAP
Date of Publication:01/01/2005