Conductive Heat Transfer
Conductive heat conduction.
blockType: AcausalFoundation.Thermal.Elements.Conduction
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Conductive Heat Transfer Path in the library: |
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Variable Conductive Heat Transfer Path in the library: |
Description
Unit Conductive Heat Transfer represents the transfer of heat by conductive heat transfer between two layers of the same material.
The block icon changes depending on the value of the Conductivity type parameters.
For a flat surface, the transfer is described by the Fourier law:
where:
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- heat flux;
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- thermal conductivity of the material;
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- cross-sectional area perpendicular to the direction of heat flow;
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- the distance between the layers, i.e. the thickness of the material;
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- temperature of layer A;
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- temperature of layer B.
Heat conduction through a cylindrical pipe wall:
Where:
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- is the length of the pipe;
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- internal diameter;
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- outside diameter.
Thermal conductivity can be specified using the Conductivity type parameters:
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Constant- the thermal conductivity remains constant during the simulation. You specify thermal conductivity using the Thermal conductivity parameters. -
Variable input- the thermal conductivity is set using the input signal on the K port, which can be varied during the simulation. The Minimum thermal conductivity parameters sets the lower limit of the signal. -
Tabulated data- thermal conductivity is specified by usage of tabulated data based on temperature. In this case thermal conductivity can also change during modelling.
The Tabulated data option uses the average block temperature to determine the thermal conductivity. For flat wall geometry, the average temperature is equal to
For cylindrical wall geometry, the average temperature is equal to
,
which implies that is inside the cylinder.
A and B are thermal ports corresponding to the material layers. Positive direction of heat transfer from port A to port B, in this case the value of heat flux is positive.
Ports
Input
K - heat conductivity control signal, W/(K*m)
scalar
Input signal that controls thermal conductivity. The signal saturates when the value goes beyond the minimum limit set by the Minimum thermal conductivity parameters.
Dependencies
To use this port, set the Conductivity type parameters to Variable input.
Parameters
Conductivity type - type of heat conductivity properties setting
Constant (by default)| Variable input| Tabulated data
Type of thermal conductivity property assignment:
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Constant- the thermal conductivity remains constant during the simulation. You set the thermal conductivity using the Thermal conductivity parameters. -
Variable input- thermal conductivity is set using the input signal on the K port, which can be varied during the simulation. The Minimum thermal conductivity parameters sets the lower limit of the signal. -
Tabulated data- thermal conductivity is specified by usage of tabulated data based on temperature. In this case thermal conductivity can also change during modelling.
Wall geometry - wall shape for thermal conductivity
Planar (by default)| Cylindrical.
Wall shape for heat conduction:
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Planar- heat transfer is through a flat rectangular wall. The area and thickness of the wall are specified. -
`Cylindrical' - heat transfer is through a cylindrical pipe wall. The internal diameter, external diameter and length of the pipe are specified.
Area - heat transfer area
1e-4 m² (by default) | positive scalar
The area of the cross-section perpendicular to the direction of heat flow.
Dependencies
To use this parameter, set the Wall geometry parameters to Planar.
Thickness is the thickness of the material
0.1 m (by default) | positive scalar
The thickness of the material, i.e. the distance between layers.
Dependencies
To use this parameter, set the Wall geometry parameters to Planar.
Inner diameter - internal diameter of the pipe
0.05 m (by default) | positive scalar
The inner diameter of the pipe, i.e. the diameter of the inner layer of the material.
Dependencies
To use this parameter, set the Wall geometry parameters to Cylindrical.
Outer diameter - outside diameter of the pipe
0.1 m (by default) | positive scalar.
The outer diameter of the pipe, i.e. the diameter of the outer layer of the material.
Dependencies
To use this parameter, set the Wall geometry parameters to Cylindrical.
Length - pipe length
1.0 m (by default) | positive scalar
Pipe length.
Dependencies
To use this parameter, set the Wall geometry parameter to Cylindrical.
Thermal conductivity - material thermal conductivity
401.0 W/(K*m) (by default) | `positive scalar'.
Thermal conductivity of the material.
Dependencies
To use this parameter, set the Conductivity type parameters to Constant.
Minimum thermal conductivity is the lower limit of thermal conductivity
10 W/(K*m) (by default) | `positive scalar'.
The lower limit of the thermal conductivity value. The input signal at the K port saturates at this value to prevent further reduction in thermal conductivity.
Dependencies
To use this parameter, set the Conductivity type parameters to Variable input.
Thermal conductivity vector - vector of thermal conductivity values for usage in the lookup table
[413, 401, 392, 383, 371, 357, 342] W/(K*m) (by default) | a vector of positive values.
A vector of thermal conductivity values corresponding to the values of the Temperature vector parameters. The size of the vector must be the same as the Temperature vector parameters. The block performs a one-dimensional search of the thermal conductivity table using block average temperature, linear interpolation and nearest extrapolation.
Dependencies
To use this parameter, set the Conductivity type parameter to Tabulated data.
Temperature vector - vector of temperature values for usage in the thermal conductivity table
[200, 273, 400, 600, 800, 1000, 1200] K (by default) | `strictly increasing vector'.
A vector of temperature values corresponding to the values of the Thermal conductivity vector parameters. The vector must be strictly increasing. The values may be irregularly arranged. The vector must contain at least two values.
Dependencies
To use this parameter, set the Conductivity type parameters to Tabulated data.