Prediction and Control of Steam Accumulation

Abstract

Steam accumulators are applied as buffers between steam generators and consumers in cases of different steam production and consumption rates. The application of the steam accumulator saves energy, reduces pressure fluctuations, and prevents aging of tubes and pressurized vessels in steam generators. In this paper, modes of the steam accumulator operation are analyzed and the general design of the steam accumulator control system is defined. Equilibrium and nonequilibrium thermodynamic models of the steam accumulator are presented with the aim of predicting the steam accumulator capacity and as support to the design of the control system. The equilibrium model is based on the mass and energy balance equations of the total water and steam content in the accumulator, while the nonequilibrium model is based on the mass and energy balance equations for each phase and closure laws of nonequilibrium evaporation and condensation rates. The steam accumulator pressure transients are simulated for constant steam charging and discharging flow rates, and the influence of the nonequilibrium condensation and evaporation rates on the steam accumulator capacity is shown. It is concluded that the commonly used equilibrium thermodynamic approach to the steam accumulator design does not provide accurate results in cases of rapid charging and discharging transients; therefore, there is a need for the application of the nonequilibrium approach.

Steam storage systems for flexible biomass CHP plants - Evaluation and initial model based calculation

“…Including the steam accumulator concepts of Stevanovic et al [15] and the modelling approach of Sun and Smith [17] to calculate the turbine performance, a Matlab/Simulink model of flexible biomass CHP plants is developed. The system consist of a steam accumulator (SA), a concrete thermal store (CS) and an additional storage turbine (ST).…”

“…The modelling of the SA is based on the equilibrium model of Stevanovic et al [15]. This model is selected because of its high accuracy, the ability to calculate the dynamic behaviour of the SA and the scalability to suitable storage volumes.…”

Thermodynamic Assessment of Steam-Accumulation Thermal Energy Storage in Concentrating Solar Power Plants

“…All steam accumulators are thermodynamically modelled using the mass and the energy balance equations of the equilibrium model provided by Stevanovic et al [18]. From Stevanovic et al paper, the equations are solved numerically using Runge-Kutta methods to find the transient steam mass and pressure of the steam accumulator [18]. The volumes, initial water volume ratios, and initial and final pressures of the steam accumulators of both cases are indicated in Table 1.…”

Modeling of a Hybrid Steam Storage and Validation with an Industrial Ruths Steam Storage Line

“…One way is to assume that the two-phase fluid at the internal side of the vessel is in a thermodynamic equilibrium at all times which means that liquid and steam have the same temperature [7,8,12]. Another approach is presented by Stevanovic et al [13,14], in which no equilibrium is assumed to model the RSS. Therefore, the two phases can have different temperatures and the energy and mass balance equations are calculated for each phase separately.…”