Thermal Mass
Mass in thermal systems.
blockType: AcausalFoundation.Thermal.Elements.Mass
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Thermal Mass Path in the library: |
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Variable Thermal Mass Path in the library: |
Description
Block Thermal Mass represents the thermal mass. This value reflects the ability of a material or a combination of materials to store internal energy, it depends on the mass of the body and its heat capacity.
The thermal mass is described by the following expression:
,
where:
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— heat flow;
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— specific heat capacity of the mass of the material;
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— mass;
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— temperature;
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— the time.
The Variable mass parameter allows you to specify whether the mass remains constant or changes during the simulation.:
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Turned off— the thermal mass remains constant during the simulation. -
Enabled— the thermal mass may change during the simulation. When this option is selected, the Mass parameter is replaced by the Minimum mass parameter, and the unit has two additional input ports: Mdot, which sets the change in thermal mass, and Tin, which sets the temperature of the incoming mass. The value of the signal on the Tin port does not affect the results if the mass does not change or decreases.
Use the Variable mass option to model systems in which the mass changes, but the geometric effects remain insignificant, for example, a washing machine fills up, heats up, and then empties with different amounts of liquid per cycle.
By default, the unit has one thermal port. Since the positive direction of the unit is from the port to the unit, the heat flow will be positive if it flows into the unit.
In some tasks, it is customary to display the mass sequentially with other elements in the block diagram. To support this option, you can use the Number of graphical ports parameter, which allows you to display another port. The two-port option is purely graphical: both ports have the same temperature, so the unit functions the same way, regardless of whether it has one or two ports. The block icon changes depending on the value of the Variable mass and Number of graphical ports parameters.
Ports
Entrance
Mdot — weight control, kg/s
scalar
The input port that determines the change in thermal mass. Use the high-priority variable Mass to set the initial value of the thermal mass.
Dependencies
To use this port, set the Variable mass parameter to Enabled.
Tin is the temperature of the incoming mass, K
scalar
The input port that determines the temperature of the incoming mass. The value in the Tin port has no effect if the value in the Mdot port is less than or equal to 0.
Dependencies
To use this port, set the Variable mass parameter to Enabled.
Non-directional
M — the port connecting the mass to the thermal network
warm
The thermal port that connects the mass to the heating network.
N — the second graphics port of
warm
The second thermal port allows you to connect the mass in series with other elements of the flowchart. This port has the same temperature as the M port, so the difference between the representations of a block with one and two ports is only graphical.
Dependencies
To use this port, set the Number of graphical ports parameter to 2.
Parameters
Variable mass — specify whether the mass remains constant or changes during the simulation
Disabled (by default) | Enabled
The Variable mass parameter allows you to specify whether the mass remains constant or changes during the simulation.:
-
Turned off— the thermal mass remains constant during the simulation. -
Enabled— the thermal mass may change during the simulation.
Mass — constant mass of
1.0 kg (default) | positive scalar
The value of the mass. The mass is constant during the simulation.
Dependencies
To use this port, set the Variable mass parameter to Turned off.
Specific heat — specific heat capacity of the pass material:q[<br>] 447.0 J/(K*kg) (default) | positive scalar
Specific heat capacity of the material.
Minimum mass — the minimum allowable mass of the
1e−6 kg (default) | positive scalar
The minimum value of the thermal mass.
Dependencies
To use this port, set the Variable mass parameter to Enabled.
Number of graphical ports — the number of visible ports of
1 (default) | 2
Options for connecting the unit to the rest of the circuit:
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1— the unit has one non-directional port that connects it to the heating network. If the unit has one port, connect it to the connecting line between the other two units. -
2— when this option is selected, the second port opens, which allows you to connect the unit in series with other units in the circuit. Since both ports have the same temperature, the unit works the same as if it had a single port.