# Flow Rate Source (TL)

Generate constant or time-varying mass flow rate or volumetric flow rate in thermal liquid network

*Since R2023b*

**Libraries:**

Simscape /
Foundation Library /
Thermal Liquid /
Sources

## Description

The Flow Rate Source (TL) block represents an ideal
mechanical energy source in a thermal liquid network. The source can maintain the specified
mass flow rate or volumetric flow rate regardless of the pressure differential. There is no
flow resistance and no heat exchange with the environment. You specify the flow rate type by
using the **Flow rate type** parameter.

The block icon changes depending on the values of the **Source type** and
**Flow rate type** parameters.

Ports **A** and **B** represent the source inlet and
outlet. The input physical signal at port **M** or **V**,
depending on the flow rate type, specifies the flow rate. Alternatively, you can specify a
fixed flow rate as a block parameter. A positive flow rate causes gas to flow from port
**A** to port **B**.

The volumetric flow rate and mass flow rate are related through the expression

$$\dot{m}=\{\begin{array}{ll}{\rho}_{B}\dot{V}\hfill & \text{for}\dot{V}\ge 0\hfill \\ {\rho}_{A}\dot{V}\hfill & \text{for}\dot{V}0\hfill \end{array}$$

where:

*$$\dot{m}$$*is the mass flow rate from port**A**to port**B**.*ρ*_{A}and*ρ*_{B}are densities at ports**A**and**B**, respectively.*$$\dot{V}$$*is the volumetric flow rate.

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

### Conserving

## Parameters

## Extended Capabilities

## Version History

**Introduced in R2023b**