Two-phase flows are commonly found incomponents in energy systems such as evaporators and boilers. Theperformance of these components depends among others on thecontroller. Transient models describing the evaporation process areimportant tools for determining control parameters, and fast loworder models are needed for this purpose. This article describes ageneral moving boundary (MB) model for modeling of two-phase flows.The new model is numerically fast compared to discretized modelsand very robust to sudden changes in the boundary conditions. Themodel is a $7^th$ order model (7 state variables), which is asuitable order for control design. The model is also well suitedfor open loop simulations for systems design and optimization.It is shown that the average void fraction has a significant influenceon the system response. A new method to calculate the average voidfraction including the influence of the slip ratio is given. Theaverage void fraction is calculated as a symbolic solution to theintegral of the liquid fraction profile.
|Title of host publication||Modelica'2002 Proceedings|
|Publication status||Published - 2002|
Subject classification (UKÄ)
- Control Engineering