Pressure in a closed thermal liquid system
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I have a problem regarding pressure in a closed themal liquid system, visible below:
The initial pressure in the pipe is the atmospheric one, but after about 1000s it reaches 8 bars. How is it possible, and why does it happen? I want to build a physical model of a cooling system, but I worry that it will have such high pressures, that I know are not the case in the reality. Thank you in advance!
Yifeng Tang on 21 Sep 2022
You'll need a "tank" to stablize this.
What happens is that the density of the fluid is a function of pressure and temperature. The source will do work to move the fluid, and that work will heat up the fluid. Higher temperature, lower density, so the fluid will try to expand, but it can't because the volume of the whole system is fixed. As a result, pressure goes up.
In fact, depending on if you are using a flow rate source or a pressure source, you may get too high an overall pressure or too low.
The solution is to add a tank component (like this one). Usually these closed loop systems have one. It'll allow the fluid to expand a bit without brining the pressure to a crazy level, as in a real system. If you don't have access to Simscape Fluids, you can try to build a "tank" using the Translational Mechanical Converter (TL) block.