Flash boiling steam/water flow phenomenon is encountered when a saturation mixture flow of R718 refrigerant experiences a depressurization rapidly inside motive nozzle of ejector. In this work, the phenomenon is modelled via CFD approach through a mixture model with slip velocity between two phases. To account for thermal non-equilibrium, the authors use evaporation/condensation model with evaporation/condensation frequency (time delay of boiling/condensing) is extracted from experimental data. This study tested on a 2D convergent-divergent nozzle with a range of total pressure-inlet (134-189 kPa) and range of inlet liquid mass fraction (0-0.36) for case of saturation vapor/liquid R718 flow. Results of simulation in this case are in agreement with experimental data when maximum relative error is 8.2 % . The same geometry and numerical model is also applied for superheated vapor R718 flow in range of total pressue-inlet (91-141 kPa) and total inlet temperature (378-399 K), maximum relative error between simulation and experimental data in this case is 9.2%.

Simulation of R718 flash boiling flow inside motive nozzle of ejector

MEREU, RICCARDO;BESAGNI, GIORGIO;DOSSENA, VINCENZO;INZOLI, FABIO
2016

Abstract

Flash boiling steam/water flow phenomenon is encountered when a saturation mixture flow of R718 refrigerant experiences a depressurization rapidly inside motive nozzle of ejector. In this work, the phenomenon is modelled via CFD approach through a mixture model with slip velocity between two phases. To account for thermal non-equilibrium, the authors use evaporation/condensation model with evaporation/condensation frequency (time delay of boiling/condensing) is extracted from experimental data. This study tested on a 2D convergent-divergent nozzle with a range of total pressure-inlet (134-189 kPa) and range of inlet liquid mass fraction (0-0.36) for case of saturation vapor/liquid R718 flow. Results of simulation in this case are in agreement with experimental data when maximum relative error is 8.2 % . The same geometry and numerical model is also applied for superheated vapor R718 flow in range of total pressue-inlet (91-141 kPa) and total inlet temperature (378-399 K), maximum relative error between simulation and experimental data in this case is 9.2%.
Refrigeration Science and Technology
9782362150173
9782362150173
CFD; Mixture model; R718; Refrigeration, Ejector Flash boiling; Control and Systems Engineering; Electrical and Electronic Engineering; Mechanical Engineering; Condensed Matter Physics
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/1009645
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