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This paper validates the accuracy of the dynamic heat-exchanger model that deals with any combination of phase states like water and steam inside heat-exchanger tubes. A unique feature of the model is to constrain the mass flow of water and/or steam calculated by momentum balance to satisfy thermodynamic relationships by means of reducing the difference between the density based on a thermodynamic relationship and the density determined on the basis of the deviation of the inlet and outlet mass flows. In this paper, the simulation results are compared with actual operating data in static and transient states of a once-through evaporator in which the water inside tubes is heated to evaporate by high-temperature gas outside tubes. The static simulation results show that the temperatures of the water and/or steam and the gas are predicted with an accuracy of 5% for temperatures, mass flows, and pressures. The simulation successfully reached the balanced equilibrium of the heat flow between the water and/or steam and the gas without numerical oscillations. The transient simulation results show that the proposed model reduced the mean deviation to actual operating data by 77% compared with the conventional model for selected times where the mass flow changed from increase to decrease and vice versa. In short, the proposed model improves the accuracy in dynamic response of mass flow. Key words

Validation of dynamic heat-exchanger model for any combination of water and steam states using actual operating data