How important is the estimation of minor head loss in transport of fluids

 It depends on several factors. In some cases minor head losses may be too small to waste time in its calculations but in some other it may not.

A discussion and some guidlines can be given about this matter.

Two pipe design cases

Head loss $h_L$, head added $h_A$ and head removed $h_R$ are adjustments to the Bernoulli equation so that these only make sense when the piping components are such that need to be taken into account. For example,

• when control valves are present in a pipe or branch,
• when the piping design is a network,
• when pumps or turbines are part of the pipe,
• among other cases,

heads need to be calculated for a proper balance. Head losses could be of the order of two digits.

However, if the pipe is not too long or intricated then heads could be expected to be small. In this case, head loss could be of the order of one digit.

Factors incresing/decreasing the head loss $h_L$

Head losses may be increased by some factors. Here are some:

• large pipe sections,
• pipe length to diameter ratio larger than three digits,
• pipe accesories such as: elbows, high pressure drop valves, invasive flow meters (orifice plate, venturi meter, etc.),
• pipe elevations.

Warning

You should always estimate head losses to give a reliable result and reasonable design. However, rough estimations discarding some head losses could only be possible in early design stages to have a quick idea of the overall piping.

Any question? Write in the comments and I shall try to help.

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Ildebrando.

How to make sure the fluid goes in the direction it suppose to go?

 For short, the answer lies in a concept widely used in pipe engineering: hydraulic load or just load. Unfortunately, this concept is not well understood. 

The hydraulic load can be understood as the amount of energy available to drive a fluid through a pipe or conduit. And if you compare the load at two different points along a pipe you could easily check for the direction in which the fluid travels.

The hydraulic load can be, mathematically, written as:

$H_L=\dfrac{p}{\gamma}+z$        Eq. (01)

where:

$H_L$ stands for the  hydraulic pressure at a given point along th pipe,

$p$ for pressure at that point along the pipe,

$\gamma$ for specific weight of the fluid,

$z$ vertical height of that point along the pipe.

As you may  have already noticed: the hydraulic load only makes sense when talking about a given location along a certain pipe.

Fig. 01 Flow direction cases according to the hydraulic load $H_L$ at two different locations.

In case 1 in Fig. 01 the flow travels upward and the only way of making sure this is so is by checking that $H_{L1}$ is greater than $H_{L2}$. Otherwise, the fluid will travel backwards.

 This concept is a mechanical balance coming from the Bernoulli equation. However, estimations on how greater $H_{L1}$ is with respect to $H_{L2}$ depends on some pipe features and equipments taken into account in the general energy balance equation.

Any question? Write in the comments and I shall try to help.

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Ildebrando.