Simulink Thermal liquid simulation

I always get Error messages for pressure too low but I cant inser a pressure falue. Also i need some tipps how to model this correclty im not sure if this model works as i intendedt it to do.

The Idea is I have some electrical components and I want to liquid cool them. One cooling loop runs on glychol and the other on fresh water un the mitte is an heatexchanger of some form. With this Model I want the tempertures in every component and the presure inside the sytem also at the end ,when I get this running, I want to calculate the ideal dimensions of my heatexchanger.

This curent model is just with some fictional constants and parameter I just want to get it up and running and then, plug and play in the parameters and let it calculate.

I hope you can help me or point me somewhere helpful where I can learn this.

Answer 1

[Yifeng Tang]

Hi Jan,

There are a few things that need attention in your model:

• use of "absolute reference" blocks: this block prescribes an infinite amount of liquid a 0 K and 0 Pa. It's usually used at the B port of pressure and temperature sensors (or any across variable sensors). Having one at the outlet of a heat exchanger or next to a reservoir doesn't make sense at all. And if a pump is trying to pull liquid from such a reference block, the pressure will go below 0 Pa and the simulation will err out.
• Use of pressure & temperature sensors and flow rate sensors. The former is an across variable sensor, which you place over the two points for which you would like to measure the pressure or temperature DIFFERENCE. The flow rate sensor is a through variablesensor and needs to be placed in line with the flow.

Suggestion:

• Go over Simscape Onramp, if you haven't already, to get familiar with Simscape basics.
• Break down your system into subsystems, and validate each using test harness models. You may build test harness models by using reservoirs as boundary conditions and ideal sources to drive the flow. You will need some reference data to properly size the components in each subsystem.
• Look at a few shipping examples in the thermal liquid domain, play with them, and reuse & resize part of the models when appropriate.

Good luck and happy modeling!