Specifying Thermal Conductance of a Gasket Element
The thermal conductance between the top and bottom surfaces of a
three-dimensional coupled temperature-displacement gasket element can be
specified for gasket behavior defined by a material model or a gasket behavior
model.
Modeling Conductance between the Top and Bottom Surfaces of a Gasket Element
The conductive heat transfer between the top and bottom surfaces of a gasket
element is assumed to be defined by
where q is the heat flux per unit area crossing the
gasket from point A on the top surface to point
B on the bottom surface,
and
are the temperatures of the points on the surfaces, and k
is the gap conductance. Point A is a node on the top
surface; and point B is the corresponding node on the
bottom surface.
You can define k directly or, in
Abaqus/Standard,
in user subroutine
GAPCON.
Defining Gap Conductance Directly
When defining k directly, define it as
where
c
is the closure between A and B,
p
is the pressure transmitted across the gasket between A
and B,
is the average of the surface temperatures at A and
B,
is the average of the magnitudes of the mass flow rates per unit area. This
variable is not considered here and should be set as zero.
is the average of any predefined field variables at A
and B.
Defining Gap Conductance as a Function of Closure
You can create a table of data defining the dependence of
k on the variables listed above. The default in
Abaqus
is to make k a function of the closure
c. When k is a function of closure,
c, the tabular data must start at zero closure and define
k as c increases. At least two pairs
of
points must be given to define k as a function of the
closure. The value of k drops to zero immediately after
the last data point, so there is no heat conductance when the closure is
greater than the value corresponding to the last data point.
Defining Gap Conductance as a Function of Contact Pressure
You can define k as a function of the pressure,
p. When k is a function of pressure
in gasket elements, the tabular data must start at zero pressure and define
k as p increases. The value of
k remains constant for pressures outside of the interval
defined by the data points.
Gap Conductance as a Function of Both Closure and Contact Pressure
If both closure-dependent and pressure-dependent conductances are
specified, the pressure-dependent curves are used to evaluate the conductance.
Defining Gap Conductance to Be a Function of Predefined Field Variables
In addition to the dependencies mentioned previously, the gap conductance
can be dependent on any number of predefined field variables,
.
To make the gap conductance depend on field variables, at least two data points
are required for each field variable value.
Defining the Gap Conductance Using User Subroutine GAPCON
In
Abaqus/Standardk can be defined in user subroutine
GAPCON. In this case there is greater flexibility in specifying
the dependencies of k. It is no longer necessary to define
k as a function of the average of the two surface's
temperatures, mass flow rates, or field variables:
The mass flow rates in user subroutine
GAPCON are not used to model conductance in gasket elements, and
the variables should be set to zero.