This sample problem demonstrates two possible ways to model a mass flow controller (MFC) in the FloCAD® module of Thermal Desktop®.

If an MFC maintains the same mass or volumetric flow rate perfectly, a simple SetFlow device would be the answer. However, there are several reasons why a more complex method may be needed.

As a demonstration, two different types of MFC controllers are presented:

1. A SetFlow with a by-pass path for representing a lower control limit. (An upper limit could be added as an extension.) This is a simple representation, with minimal user logic:

2. A PID-controlled Orifice (valve model), which exhibits both upper and lower limits to its control, along with a finite response rate. It requires PID tuning and sizing of the orifice’s range of motion:

These examples represent just two possibilities. Many more methods are possible, especially if details of the valve construction, the flow measurement method, and the electronics and control algorithm are available.

For more information and to see sample solutions, click here to visit our Tips and Samples page, which includes links to the detailed problem description and drawing files in the CRTech User Forum.