Consistent initialization of system of differential-algebraic equations for dynamic simulation of centrifugal chillers

Abstract

For simulation of centrifugal chiller system with differential algebraic equations, consistent initial conditions are difficult to obtain due to the two-phase refrigerant cycle and the connections between several components. Existing rigorous initialization methods are not suitable for the particular problems in centrifugal chiller simulation, such as the surge instability. In this paper, the dynamic model of a water-cooled centrifugal chiller is developed in Modelica with Dymola and the TLK/IfT Library (TIL). A preprocessing scheme and a direct initialization method are proposed for the consistent initialization of chiller DAE system. Simulation results have shown the effectiveness of the proposed modelling framework and the initialization method.