CFD simulation of air–steam flow with condensation

Highlights: • Condensation model for CFD code Fluent. • Suitable for flow of air–steam mixture with additional non-condensable gases. • Suitable for both compressible and incompressible flow. • Successfully tested on the CONAN experiments and PANDA Test 9bis experiment. - Abstract: This article presents a custom condensation model for commercial CFD code Fluent. The condensation model was developed for the species transport model in Fluent code and it is suitable for both compressible and incompressible flow of air–steam mixture with additional non-condensable gases. The condensation model consists of two parts: condensation in volume and condensation on the wall. Condensation in volume is modeled by "return to saturation in constant time scale" method. Condensation on the wall is calculated from diffusion of steam through a layer of non-condensable gases near the wall. The performance of the condensation model was tested on the CONAN experiments. In these experiments, air–steam mixture flows downwards through a vertical channel with square cross section. One vertical wall of the channel is cooled and the steam condenses on it. The same model was then applied in simulation of PANDA Test 9bis experiment with condensation. In this test, two vessels connected with a pipe were filled with air; and steam was released into the first vessel. As the steam concentration increased in the vessels, the steam started condensing on the walls. The results of CFD simulations of both CONAN and PANDA experiments compared well with the measured data