CFD simulation of conjugated heat transfer with full boiling in OpenFOAM(R)

Abstract

The Computational Fluid Dynamics (CFD) simulation of subcooled and saturated boiling flow with multi-domain thermal coupling is a challenge, and the current methods to solve the exchange of mass, momentum, and energy still require further development and validation. This work addresses the implementation and assessment of a new solver (CHT-2FM) in OpenFOAM(R), which includes the Conjugated Heat Transfer (CHT) model into the two-phase Eulerian method (2FM) in order to solve wall boiling. This solver allows applying the wall heat flux partitioning model (Rensselaer Polytechnic Institute) to solve subcooled and saturated boiling flows coupling two fluid circuits through a solid domain, without impose the heat flux at the heater wall. The solver is experimentally and numerically validated against three tests; First the well-known vertical heated pipe with homogeneous heat flux proposed by Bartolomej et al. (1982) was solved to assess the RPI model, and the interfacial momentum exchange. The test was also solved with RELAPMod3 in order to assess the boiling model implemented in this code. Second, a numerical low-pressure benchmark of a vertical double-pipe evaporator proposed by Abishek et al. (2017) was solved. This allow comparing some RPI model parameters, and the CHT implementation. The third test was proposed by the authors in order to evaluate the CHT-2FM implementation for water operation conditions relevant for nuclear engineering. The test was also solved with RELAPMod3. Based on the first test, the RPI model in OpenFOAM correctly solved the Bartolomej test in terms of void fraction. On the contrary, RELAPMod3 overestimated boiling at the end of the pipe. From the second test it was concluded that the CHT-2FM coupling was correctly implemented. Finally, the use of the developed tool to solve heat coupled fluid systems led to very acceptable solutions compared with RELAPMod3 estimations.