Lesson 10 - Control of Fluid Flow 2

Our study of fluid mechanics has been gradually building lesson upon lesson, to provide us with a better understanding of the principles of fluid mechanics, and also the ability to apply this understanding in many practical situations. To conclude the current topic of controlling fluid flow, we will look at how to ensure that vapour (or dissolved gases) are not produced when a liquid is being pumped. This can cause issues with product quality as well as damage pumping equipment and control valves.

Dissolved gases and vapour

Many brewery liquids contain dissolved gases, where the dissolved gas is a different compound from the liquid which it is dissolved in. Some examples of these would be:

• Carbonated beer: where carbon dioxide gas is dissolved in beer

• Nitrogenated beer: where nitrogen gas is dissolved in beer

• Carbonated dilution water: where carbon dioxide is dissolved in water

By contrast, all liquids can form vapours from themselves. Vapour is merely a differing physical state (solid, liquid or vapour) of the same compound. Some examples of these would be:

• Steam vapour from liquid water: this very common example is slightly confusing as we generally use the term ‘steam’ for water vapour and ‘water’ for liquid water.
• Ammonia vapour from liquid ammonia: a more straightforward example, with the use of the same compound name and the two states of vapour and liquid used.

When such liquids are being transported using pumps and pipe systems, we do not wish the gases, or any other vapours, to come out of solution. Doing so would change the quality of the liquid and, as we will see later, it can also lead to a loss of pump performance or even damage to the pump/piping system.

Why would liquid quality be affected if dissolved gases came out of solution or vapours formed?

Give yourself 5-10 mins to think about this and then click ‘Next’ to continue with this lesson.