A Homogeneous Dynamic Two-Phase Flow Model of A Vertical Evaporator with Varying Firing Profiles

Axel Ohrt Johansen
Added Values P/S, Vejle, Denmark

Brian Elmegaard
Technical University of Denmark Department of Mechanical Engineering, Lyngby, Denmark

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Ingår i: Proceedings of the 55th Conference on Simulation and Modelling (SIMS 55), Modelling, Simulation and Optimization, 21-22 October 2014, Aalborg, Denmark

Linköping Electronic Conference Proceedings 108:7, s. 64-100

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Publicerad: 2014-12-09

ISBN: 978-91-7519-376-2

ISSN: 1650-3686 (tryckt), 1650-3740 (online)


In this article we would like to demonstrate the ability to simulate the dynamic conditions in a homogeneous two-phase flow model of a power plant evaporator and thus complement the recent years, research efforts in areas related to flexibility of power production. On that basis we can contribute with new knowledge about the flow stability and dynamic effects in power plants, caused by both internal and external physical conditions, resulting in improved power plant flexibility. In this article is developed numerical model for solving a transient one dimensional compressible homogeneous two phase model, for predominantly one-dimensional flows in a vertical heated pipe element. The homogeneous model is based on the assumption of both hydraulic- and thermal equilibrium. The flow model consists of three hyperbolic fluid conservation equations; continuity, momentum and energy and the pipe wall is modelled as a one dimensional heat balance equation. The models is reformulated in the four in-dependent variables: pressure, enthalpy, velocity and wall temperature. We have implemented and tested a fifth-order WENO solver, with simplified weights functions and used it to simulate the dynamic response of evaporator tubes corresponding to SKV3, on the basis of a calibrated model, based on measurements from SKV3. The model is able to describe the entire evaporation process from sub-cooled water to super-heated steam at the outlet and verify the consequences of different firing profiles and evaporator pressure for the boiler of SKV3.


Two-phase flow; evaporator; WENO scheme; heat flux bias; dynamic responce


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