A general comment on pipes

The flow of a fluid through a pipe, in several bachelor courses, is studied merely as a theoretical topic. However, in several ocasions instructors tend to use a textbook where flowrate or pressure loss or pipe diameter are unknown and then estimated by means of the energy or Bernoulli equation.

Many textbooks show this. Take for example the following two popular sources:

A more realistic point of view

It comes out that estimation of flow rate or pressure loss or pipe diameter must be complemented with real pipe data that could possibly be installed. In my opinion, these kind of situations must be treated as a design problem. Otherwise, learning is reduced (I think).

In my opinion, it is important that whoever is taking a regular fluid mechanics course should know that there is pipe data indicating its mechanical features. For short, who performs hydraulic calculations should consider the following:

• nature of the working fluid, where densisty, viscosity, volumetric expansion coefficient, consensation temperature and material compatibility, for example;
• maximum and minimum flow rate, at which the pipe could work,
• maximum and minimum pressure expected to be used to move the fluid through the pipe, and
• maximum and minimum temperature that the fluid will have while being transported.

The previous statements are important because no mater the results of the theoretical calculations, in the end a real pipe satisfying the following factors:

• safety,
• life of service y
• available money, for example

must be selected.

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Ildebrando