Pressure Source (TL)

Generate constant or time-varying pressure differential

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Libraries:
Simscape / Foundation Library / Thermal Liquid / Sources

Description

The Pressure Source (TL) block represents an ideal mechanical energy source in a thermal liquid network. The source can maintain the specified pressure differential across its ports regardless of the flow rate through the source. There is no flow resistance and no heat exchange with the environment.

Ports A and B represent the source inlet and outlet. The input physical signal at port P specifies the pressure differential. Alternatively, you can specify a constant pressure differential as a block parameter. A positive pressure differential causes the pressure at port B to be greater than the pressure at port A.

The energy balance at the source is a function of the energy flow rates through ports A and B and the work done on the fluid:

$${\varphi }_A+{\varphi }_B+{\varphi }_{work}=0,$$

where:

• ϕ_A is the energy flow rate into the source through port A.

• ϕ_B is the energy flow rate into the source through port B.

• ϕ_work is the isentropic work done on the fluid.

The isentropic work term is

$${\varphi }_{work}=\frac{\dot{m}\left(p_B-p_A\right)}{{\rho }_{avg}},$$

where:

• ϕ_work is the isentropic work done on the thermal liquid.

• p_A is the pressure at port A.

• p_B is the pressure at port B.

• ρ_avg is the average liquid density,

  $${\rho }_{avg}=\frac{{\rho }_A+{\rho }_B}{2}\text{.}$$

Assumptions and Limitations

• There are no irreversible losses.

• There is no heat exchange with the environment.

Ports

Input

P — Pressure differential control signal, Pa

physical signal

Input physical signal that specifies the pressure differential across the source.

Dependencies

To enable this port, set the Source type parameter to Controlled.

Conserving

A — Source inlet

thermal liquid

Thermal liquid conserving port. A positive pressure differential causes the pressure at port B to be greater than the pressure at port A.

B — Source outlet

thermal liquid

Thermal liquid conserving port. A positive pressure differential causes the pressure at port B to be greater than the pressure at port A.

Parameters

Source type — Select whether pressure differential can change during simulation

Controlled (default) | Constant

Select whether the pressure differential generated by the source can change during simulation:

• Controlled — The pressure differential is variable, controlled by an input physical signal. Selecting this option exposes the input port P.

• Constant — The pressure differential is constant during simulation, specified by a block parameter. Selecting this option enables the Pressure differential parameter.

Pressure differential — Constant pressure differential across the source

0 Pa (default) | scalar

Desired pressure differential across the ports of the source.

Dependencies

To enable this parameter, set Source type to Constant.

Power added — Select whether the source performs work

Isentropic (default) | None

Select whether the source performs work on the fluid flow:

• Isentropic — The source performs isentropic work on the fluid to maintain the specified pressure differential. Use this option to represent an idealized pump or compressor and properly account for the energy input and output, especially in closed-loop systems.

• None — The source performs no work on the flow, neither adding nor removing power, regardless of the pressure differential produced by the source. Use this option to set up the desired flow condition upstream of the system, without affecting the temperature of the flow.

Cross-sectional area at ports A and B — Area normal to flow path at inlet and outlet

0.01 m^2 (default) | positive scalar

Area normal to the direction of flow at the source inlet and outlet. The two cross-sectional areas are assumed identical.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2013b

R2023b: Usability enhancement for thermal liquid sources

In R2023b, separate Pressure Source (TL) and Controlled Pressure Source (TL) blocks have been combined into a single Pressure Source (TL) block that lets you select between generating constant or time-varying pressure differential.

This change has no compatibility impact when you use these Foundation library blocks in your models. When you open an existing model, the Controlled Pressure Source (TL) blocks are automatically replaced by Pressure Source (TL) blocks with exposed input port.

However, if you use these blocks in your custom composite components, you need to update the composite component code.

Source Block to Update	Old Syntax	New Syntax
Controlled Pressure Source (TL)	source = foundation.thermal_liquid.sources.controlled_pressure_source;	source = foundation.thermal_liquid.sources.pressure_source;
Pressure Source (TL)	source = foundation.thermal_liquid.sources.pressure_source;	source = foundation.thermal_liquid.sources.pressure_source(source_type=foundation.enum.constant_controlled.constant);

R2023a: Configure flow conditions without affecting temperature

The block includes the Power added parameter, which lets you specify whether the source performs work on the fluid flow. The default option, Isentropic power, is equivalent to the block behavior in previous releases. Use the new None option to set up the desired flow condition upstream of the system, without affecting the temperature of the flow.