# chtMultiRegionFoam, fixed convection coefficient between fluid and solid

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 September 19, 2012, 14:43 chtMultiRegionFoam, fixed convection coefficient between fluid and solid #1 New Member   Romain Join Date: Aug 2012 Posts: 12 Rep Power: 7 Sponsored Links Hello, I was wondering if I could use a fixed convection coefficient as a boundary condition. Here is my simulation : For now, I use solid_to_air { type compressible::turbulentTemperatureCoupledBaffleMix ed; value uniform 300; neighbourFieldName T; K solidThermo; KName none; as it is done in the tutorial chtMultiRegionHeater. } From what I understand, with this boundary condition, the coefficient of convection h is automatically calculated from the nature of the flow. But is it possible to impose a value ? I tried to use fixed gradient since Q=h*S*DT (q=h*DT, thus DT=q/h), but it does not seem to work. If I use, solid_to_air { type fixedGradient: gradient 5; } and air_to_solid { type fixedValue: value uniform 300; } the gradient does not seem to be taken between the solid and the air, but between the two walls of the solid, and since one of the side of the solid is heated, the simulation does not reach convergence. When I use solid_to_air : fixed value or type compressible::turbulentTemperatureCoupledBaffleMix ed; on both solid_to_air and air_to_solid my simulation is working. If it was an exterior wall, I could have use type externalWallHeatFluxTemperature; K solidThermo; // solidThermo or lookup // q uniform 62500; // Heat flux / [W/m2] Ta uniform 300.0; // Tambient temperature /[K] h uniform 100.0; // Heat transfer coeff /[W/Km2] value uniform 300.0; // Initial temperature / [K] KName none; But with this condition, Ta is fixed and does not use the value of Tair Thanks in advance, Romain Last edited by romain.h; September 25, 2012 at 03:29.

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