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The Solid option specifies that the heat flux q0 is defined in the material frame. Because the heat transfer variables and equations are defined in the spatial frame, the inputs are internally converted to the spatial frame. See Conversion Between Material and Spatial Frames for details.
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The default option for the Heat Flux node is Nonsolid, which defines q0 in the spatial frame. No frame conversion is needed.
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The From material option uses the option selected in the Material type list of the Material Properties section of the material applied on the domain on which the node is active.
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Wall height L.
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Wall height L and the Tilt angle ϕ. The tilt angle is the angle between the wall and the vertical direction, ϕ = 0 for vertical walls.
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Characteristic length (area/perimeter) L. The characteristic length is the ratio between the surface area and its perimeter.
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When Water, Benzene, n-Pentane, or Ethanol is selected, the material properties of the liquid and vapor phases required in the correlation are predefined (at saturation temperature and pA=1 atm). Depending on the selected fluid, different materials and finishings are available in the Surface list. For each option, the empirical constants Csf and s are predefined.
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When From material is selected in the Fluid list, first choose materials available on the boundary from the Liquid materials and Vapor materials lists, to define ρl, Cp,l, kl, μl, and ρv. Then set the Ambient pressure, pA, the Saturation temperature, Tsat, the Latent heat of evaporation, Lv, and the Liquid-vapor surface tension, σ. Finally, enter values or expressions for the Rohsenow’s correlation parameters: the Prandtl number exponent, s, and the Liquid-surface combination factor, Csf, which accounts for surface roughness, that tends to increase the number of active nucleation sites for boiling.
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This boundary condition will give incorrect results if T < Tsat and should only be used in a limited interval of validity Tsat + T1 < T < Tsat + T2. Typically, for water T1=10 K and T2=30 K.
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