GunnsThermalRadiation
This link extends GunnsBasicConductor and models radiative heat transfer between two nodes. Heat flux between the two nodes, with temperatures T0 and T1, is:
The product of Emissivity * Stefan-Boltzmann Constant * Effective Area is the link conductance, which the user provides as configuration data. The View Scalar is given an initial value as input data and can be changed in run-time as the radiating surfaces are hidden from or exposed to each other due to rotations or intervening objects, etc. These terms are described in further detail below.
Two bodies radiating between each other via this link causes their temperatures to tend to approach each other, just like with a basic conductor, except the heat flux is a function of the 4th power of their temperatures.
Thermal radiation links can be connected in the same ways that a GunnsBasicConductor can.
Port Connection Rules (These are limitations on the port connection to nodes that the link enforces in run-time):
- Same as GunnsBasicConductor.
Other Rules (These are extra rules you should always try to follow):
- Apart from heat flux being to the 4th power of temperature, this links acts just like the regular GunnsBasicConductor and can be connected and combined in the same ways.
- One link represents one radiative path between two surfaces, with one surface on each node's lump mass. There is no limit to how many radiation links can attach to a node. Multiple links on a node may represent the same physical surface, or multiple surfaces. The same physical surface can have multiple radiative paths to other nodes, and even multiple paths to the same node.
- The ground node represents empty space, so connecting one port to Ground models the other port node's surface radiating to empty space.
- Note that this link only models a portion of a surface's total radiated heat - just the portion exchanged with the other facing surface. Unless the facing surface covers 100% of this surface's field of view, a complete model of the radiated heat from this surface requires other thermal radiation links to model the radiation between the other visible surfaces, and one thermal radiation link connected to ground to model the radiation to free space.
Configuration Data Parameters:
-
defaultConductivity (default = 0.0 (W/K4), must be >= 0 and in general you should limit non-zero values
to be between 1.0E-15 and 1.0E+15): This is the product, which you must calculate
and enter here, of 3 terms:
- Emissivity: a unitless property of the surface materials, it should have a value between (0-1).
- Stefan-Boltzman Constant: always use the SI value of 5.670373E-8 (W/m2/K4).
- Effective Area: this is the projected area in (m2) between the two surfaces at the given initial viewScalar.
Input Data Parameters:
- malfBlockageFlag (default = false): Initial state of the blockage malfunction activation flag. This malfunction reduces the effective conductivity from the defaultConductivity value.
- malfBlockageValue (default = 0.0, must be (0-1)): Initial state of the blockage malfunction activation value. A value of 0.0 is the same as no blockage at all, and 1.0 completely blocks all flux and isolates the port nodes from each other (although parallel flow paths still apply). A blockage of 1.0 represents complete shading between the two surfaces.
- viewScalar (default = 1.0): this is the initial value of the unitless parameter, also called "view factor". A value of 0.0 creates full shading between the two surfaces, the same as a blockage malfunction value of 1.0.
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