An intrinsically mass conservative switched evaporator model adopting the moving-boundary method

This paper presents a generalized intrinsically mass conservative evaporator model based on the moving-boundary approach. The heat exchanger model is based on a numerical scheme which can switch between the two-zone (two-phase and superheated) and one-zone (two-phase) representations. The switching algorithms adopt pseudo-state equations in order to track the un-active variables and ensure reasonable initial conditions when rezoning, keeping the robustness whenever superheated region appears or disappears. State variables are chosen to have an intrinsically mass conservative model. This choice is well suited when the evaporator operates at low mean void fraction conditions. Numerical results show that the simulation is consistent with integral forms of energy and continuity equations. The numerical stability to changing flow regimes is demonstrated through simulation test cases. A validation case is presented showing that the model transient behaviour can well predict the performance of an experimentally validated finned coil finite-volume evaporator model.

► A mass conservative evaporator moving-boundary model is developed. ► An innovative state variables choice assures an intrinsically mass conservative model. ► The model is consistent with integral forms of energy and continuity equations. ► The model is numerical stable to changing flow regimes. ► The algorithm model showed a good accuracy in predicting transient behaviour.