# OpenFOAM® v1906: New and updated solvers and physics

27/06/2019

## Heterogeneous reacting cloud

New heterogeneous reacting cloud functionality has been added to the Lagrangian library. This cloud is initially formed of a single solid component which reacts with the gas phase to create a solid product in the particles through a reaction of the type

solid + gas -> product
The rate of the reaction follows the model of Papanastassiou and Bitsianes for the noncatalytic reaction MUCS approach, where a reaction of the type

nuFuel*Fe3O4 + nuOx*O2 => nuProd*Fe2O3
is specified in the reactingCloud1Properties dictionary as:

heterogeneousReactingModel  MUCSheterogeneousRate;

MUCSheterogeneousRateCoeffs
{
D12         2.724e-4;
epsilon     0.41;
gamma       3.07;
sigma       1;
E           1;
A           3.14e4;
Aeff        0.7;
Ea          1.651e5;
O2          O2;

nuFuel      2.0;
nuProd      3.0;
nuOx        0.5;
fuel        Fe3O4;
product     Fe2O3;
}

The initial particle composition is specified in the reactingCloud1Properties dictionary:

singleMixtureFractionCoeffs
{
phases
(
gas
{
}
liquid
{
}
solid
{
Fe3O4 1;
Fe2O3 0;
}
);
YGasTot0        0;
YLiquidTot0     0;
YSolidTot0      1;
}

Source code
$FOAM_SRC/lagrangian/intermediate/submodels/HeterogeneousReactingModel Solver$FOAM_SOLVERS/lagrangian/reactingParcelFoam/reactingHeterogenousParcelFoam
Tutorial
Solver
Tutorial
$FOAM_TUTORIALS/heatTransfer/overBuoyantPimpleDyMFoam/movingBox ## chtMultiRegionTwoPhaseEulerFoam The new chtMultiRegionTwoPhaseEulerFoam solver combines the functionality of reactingTwoPhaseEulerFoam and chtMultiRegionFoamfor solving solid/fluid coupled systems. Region interfaces are coupled using the turbulentTemperatureTwoPhaseRadCoupledMixed boundary condition. Transitional and film boiling regimes now complement the earlier single phase and nucleating boiling regimes available in the alphatWallBoilingWallFunction boundary condition to model the heat transfer coefficient for boiling flows in general. The wall function uses a partition method to transfer heat either to the liquid or vapour phase. Currently this function works in a fixed wall temperature mode. i.e, there is no consideration for the sudden change of heat transfer coefficient (burn out) after reaching the deviation from nucleate boiling temperature, . See Srinivasan et al. (2010). For the single phase non-boiling regime the standard Jayatilleke wall function is used. For the sub-cooled nucleate boiling regime the following run-time selectable sub-models are available: • nucleation site density • bubble departure frequency • bubble departure diameter This is based on a version of the well-known RPI wall boiling model (Kurul and Podowski, 1991). The implementation is similar to the model described by Peltola and Pattikangas (2012) but enhanced with the wall heat flux partitioning models. The transition boiling regime flux () is modelled following a temperature based linear interpolation between the Critical Heat Flux () and the Minimum Heat Flux () in such a way that when the wall temperature is between the range of Deviation From Nucleate Boiling () and the Leidenfrost Temperature () a linear interpolation is used between and . The following models are required: • Leidenfrost Temperature Model • Model • SubCool Model • Model • Model • Film Boiling Model The linear interpolation is as follows for the TBF regime is calculated as: where : where is a model constant (default 1) and the wall temperature. The film boiling regime is applied when is larger than . In this regime the correlation from the film Boiling Model is used for calculating the cht from the wall. The sub-cooled model modifies when sub-cooled conditions are present. The following sub-models are implemented: • Critical heat flux (CHF) correlation. See Zuber (1958) • Film Boiling Model. See Bromley (1950) • Minimum heat flux (MHF) model. See Jeschar et. al. (1992) • Leidenfrost temperature model. See Spiegler et. al. (1963) • Critical heat flux for Sub-Cool boiling flows. See Hua and Xu (2000) • Departure from Nucleate Boiling Correlation. See Thelera and Freisba () Source code$FOAM_SRC/phaseSystemModels/reactingEulerFoam/derivedFvPatchFields/alphatWallBoilingWallFunction
$FOAM_SRC/heatTransfer/chtMultiRegionFoam/chtMultiRegionTwoPhaseEulerFoam Tutorial$FOAM_TUTORIALS/heatTransfer/chtMultiRegionTwoPhaseEulerFoam/solidQuenching2D
References
• Numerical simulation of immersion quenching process of an engine cylinder head Vedanth Srinivasan, Kil-Min Moon, David Greif, De Ming Wang, Myung-hwan Kim. Applied Mathematical Modelling 34 (2010) 2111-2128
• On the modeling of multidimensional effects in boiling channels, Kurul, N., Podowski, M.Z., ANS Proceedings, National Heat Transfer Conference, Minneapolis, Minnesota, USA, July 28-31, (1991)
• Development and validation of a boiling model for OpenFOAM multiphase solver, Peltola, J., Pattikangas, T.J.H., CFD4NRS-4 Conference Proceedings, paper 59, Daejeon, Korea, September 10-12 (2012)
• A. Bromley, Heat transfer in stable film boiling, Chem. Eng. Prog. 58 (1950) 67-72.
• N. Zuber, On the stability of boiling heat transfer, Trans. ASME 80 (1958) 711
• Jeschar, E. Specht, C. Kohler, Heat Transfer during Cooling of Heated Metallic Objects with Evaporating Liquids, Theory and Technology in Quenching, Springer, (1992). Chapter 4.
• Spiegler P., Hopenfeld J., Silberberg M., Bumpus J. and Norman A., Onset of stable film boiling and the foam limit, International Journal of Heat and Mass Transfer, 6,11, pp.987-989, (1963)
• T.C. Hua, J.J. Xu, Quenching boiling in subcooled liquid nitrogen for solidification of aqueous materials, Mater. Sci. Eng. A 292 (2000) 169-172.
• Theoretical Critical Heat Flux Prediction Based Non-Equilibrium Thermodynamics Considerations The Subcooled Boiling Phenomenon Thelera G. and Freisba D.. TECNA Estudios y Proyectos de Ingeniera S.A. Encarnacion Ezcurra 365, C1107CLA Buenos Aires, Argentina Westinghouse, Electric Germany GmbH, Dudenstrasse 44, 68167 Mannheim, Germany

## Reflective radiation model extension

The solar load model now incorporates reflecting radiative fluxes, enabling reflections to be calculated on specular surfaces.

Reflection effects are enabled by the new useRefectedRays entry in the radiationProperties dictionary, i.e.

useReflectedRays    yes;

reflecting
{
nPhi                10;
nTheta              10;
}
where the reflecting sub-dictionary is used to determine the solid angles resolution of the reflected rays. Note that only a single reflection is considered, and these entries are not related to the number of rays in the ray tracing method, but are used as discretisation angles for the search algorithm of the reflected rays from the target surface to the source. The example below shows the primary heat flux (left) and the reflected solar load on an object from a mirror panel (right) for band 0:

Tutorials
$FOAM_TUTORIALS/heatTransfer/buoyantSimpleFoam/simpleCarSolarPanel$FOAM_TUTORIALS/heatTransfer/chtMultiRegionFoam/externalSolarLoad