Moving Boundary Models for Dynamic Simulations of Two-Phase Flows

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

Omfang, udvikling og konsekvenser

textabstractWe propose a consistent utility-based framework to jointly explain a household's decisions on purchase incidence, brand choice and purchase quantity. The approach differs from other approaches, currently available in the literature, as it is able to take into account consumption dynamics. In the model, households derive utility from consumption, and they relate their purchase behavior to consumption planning. We illustrate our model for yogurt purchases, and show that our model yields important additional insights. One such insight is that the reservation price of households is not fixed, but depends on the available inventory stock. Furthermore, we find that promotional activities increase sales through more purchases in the product category and brand switching, but the effect through larger purchase quantities is limited

Moving Boudary Models for Dynamic Simulations of Two-phase Flows

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