Thermal Capacitor
This feature models a two-port passive component of the thermal system. It connects two nodes, by creating a difference in the temperatures of its two connecting ports. It models heat storage in a domain.
It adds equations for the heat rates Pp1 and Pp2 and the temperatures Tp1 and Tp2 at the connecting ports p1 and p2 of the component, and defines the following relation between the heat rate P and the temperature difference ΔT:
(6-20)
where C (SI unit: J/K) is the thermal capacitance, defined as
with V the volume (SI unit: m3), ρ the density (SI unit: kg/m3), Cp the heat capacity at constant pressure (SI unit: J/(kg·K)), and m the mass (SI unit: kg).
For a steady-state problem the temperature difference does not change with time and P = 0.
See Theory for the Thermal Capacitor and Thermal Mass Components for more details on the underlying theory.
Identifier
Enter a Component name for the thermal capacitor. The prefix is C.
Node Connections
Set the two Node names for the nodes connected by the thermal capacitor.
Component Parameters
The thermal capacitance used in Equation 6-20 should be set in this section.
Depending on the option selected in the Specify list, different settings are required:
•
With Thermal capacitance (default), set directly a value or expression for C.
•
With Density and heat capacity, set values or expressions for the Volume, V, the Density, ρ, and the Heat capacity at constant pressure, Cp. Select any material from the Material list to define the properties From material. For User defined enter values or expressions.
•
With Mass and heat capacity, set values or expressions for the Mass, m, and the Heat capacity at constant pressure, Cp. Select any material from the Material list to define Cp From material. For User defined enter a value or expression.
Initial Values
Set user defined values or expressions for the Initial temperature at node 1, T1,init, and the Initial temperature at node 2, T2,init, to be used at initialization, in particular to evaluate the heat storage term.
Results
Select appropriate options in the Add the following to default results in order to include the following global variables (space-independent) in the default plots:
•
 Heat rate
•
 Temperature at node 1
•
 Temperature at node 2
Location in User Interface
Context Menus
Lumped Thermal System>Thermal Capacitor
Ribbon
Physics tab with Lumped Thermal System selected:
Global>Thermal Capacitor