Generate time-varying volumetric flow rate

Thermal Liquid/Sources

The Controlled Volumetric Flow Rate Source (TL) block generates a time-varying volumetric flow rate through its outlet. The source is ideal. It maintains the specified flow rate regardless of the pressure differential between the inlet and outlet. Losses due to friction are assumed negligible.

The flow rate input is a physical signal that you connect to port V. This input controls the volumetric flow rate at the outlet. The rate at the inlet can differ from the input signal if the specific volume changes within the source. However, due to mass conservation, the mass flow rates at the inlet and outlet are always identical.

The ports representing the inlet and outlet change with the flow rate sign. If the flow rate is positive, fluid flows from port A to port B and the outlet is at port B. If the flow rate is negative, fluid flows from port B to port A and the outlet is at port A.

The volumetric and mass flow rates at the source outlet are related through the expression

$$\dot{V}=\{\begin{array}{cc}\dot{m}{v}_{B},& \dot{V}\ge 0\\ \dot{m}{v}_{A},& \dot{V}<\text{\hspace{0.17em}}0\end{array},$$

*$$\dot{V}$$*is the volumetric flow rate.*$$\dot{m}$$*is the mass flow rate from port A to port B.*v*_{A}is the specific volume at port A.*v*_{B}is the specific volume at port B.

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:

$${\varphi}_{A}+{\varphi}_{B}+{\varphi}_{work}=0,$$

*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

$${\varphi}_{work}=\dot{m}\left({p}_{B}-{p}_{A}\right){v}_{avg},$$

*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.*v*_{avg}is the average of the specific volumes at ports A and B,$${v}_{avg}=\frac{{v}_{A}+{v}_{B}}{2}.$$

Use the **Variables** tab in the block dialog
box (or the **Variables** section in the block Property
Inspector) to set the priority and initial target values for the block
variables prior to simulation. For more information, see Set Priority and Initial Target for Block Variables.

The source is ideal. Losses due to friction are assumed negligible.

The source is adiabatic. Heat exchange with the surroundings is assumed negligible.

Work done by the source is isentropic—that is, reversible and adiabatic.

**Cross-sectional area at ports A and B**Area normal to the direction of flow at the source inlet and outlet. The two cross-sectional areas are assumed identical. The default value is

`0.01`

m^2.**Characteristic longitudinal length**Average distance the fluid traverses in the source before it reaches the outlet. The default value is

`0.1`

m.

A — Thermal Liquid conserving port representing source inlet A

B — Thermal Liquid conserving port representing source inlet B

V — Physical signal input port for specifying the volumetric flow rate

Controlled Mass Flow Rate Source (TL) | Mass Flow Rate Source (TL) | Volumetric Flow Rate Source (TL)

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