This software calculates the pressure drop caused by liquids flowing through circular pipes and fittings. It includes databases for
liquid selection, pipe materials and fittings. It provides all the necessary information so that the designer can easily understand how
each parameter affects to the the final result, providing curves which in turn are a very useful tool to document a project.
**FACTORS AFFECTING PRESSURE DROP
CALCULATION :**

**Changes in flow rate.**

discussed
above
**Changes in roughness .**

The
roughness of a pipe is difficult to determine a priori , especially
considering that different bibliography and papers provide different
values for the same type of material. Ideally we should use the
values provided by the pipe manufacturer, but this is not always
possible or sometimes this information is not available. Besides the
roughness value is not constant throughout the life of the pipeline as
both corrosion and fouling can occur.
**Changes in viscosity. **

The
viscosity of a liquid is dependent on temperature. Therefore, it is
expected that the fluid will have different viscosities depending on
the temperature of the line, which can in turn be affected in some
cases by the ambient temperature. Sometimes the same installation can
work with fluids of different characteristics and therefore there will
be viscosity changes. Other times these variations are not very
important , but in any case it is important to see how they actually
affect the calculations and be able to obtain reports of how this
factor contributes to the total uncertainty of the calculations. The
viscosity affects the value of the Reynolds number inversely , which
also produce a change in the friction factor
**Pressure Losses in fittings**.

They are sometimes also called minor losses since in many cases are
small and can even be neglected. Its accurate calculation may be
difficult because it depends on the exact details of each manufacturer.
Usually they are characterized by the loss coefficient ( K ) . As this
coefficient depends on the actual geometry of the fitting, fittings
from different manufacturers can have different loss coefficients. For
components like valves, filters etc , manufacturers usually provide the
value of Kv or Cv (flow coefficient).
**Transition between laminar flow and turbulent
flow**.

This software performs calculations for both
laminar flow ( Reynolds number (Re) < 2000 ) , and for turbulent
flow ( Re > 4000 ) . The critical zone or transition zone is the
one in which the Reynolds number is between the values 2000 and 4000 .
In this area, it is impossible to predict the behaviour of the flow,
i.e. whether it will be laminar or turbulent , and therefore to know
the pressure drop . This implies a discontinuity in the calculations
since the formulas used for the friction factor are different depending
on the type of flow. The software LFlow solves this problem by
estimating the friction factor for this critical area, so that a
continuity is achieved in the graphs from the zone of turbulent flow to
laminar flow. Additionally , the graphs show the pressure drop in both
cases: considering laminar flow and turbulent flow. The estimated
pressure drop will always be between both values :
**FAQ**:

**How can I calculate the actual operating point
of a pump using LFlow software?**

**Can I enter all the data in
different units?**

**Can I print out a report with the results and
curves? **

**Can
the application be customized so it exactly fits my specific
requirements?**

**What are the requirements that my computer
should have to install LFlow?**

The fittings can be selected from the database or the user can enter manually the values of loss coefficient or flow coefficient.

The calculation of the pressure drop in a pipe, including the so-called minor losses or losses in fittings , usually involves a number of estimations, as all the required information is often not available at the moment of design, at least accurately. For example, the flow rate is often not known with accuracy when designing an installation as it depends on the operating point of the pump , pressure loss in the installation and the actual pump curve that finally will be installed . In addition , there are elements that produce a variable pressure loss, not only valves , but also others like filters whose head loss depends on the level of clogging. This is just an example to highlight the difficulty of accurately estimating many parameters of the system and that it is important to have a tool to make a quick assessment of up to what extent these inaccuracies can be really relevant.

The following chart shows how the pipe diameter affects the pressure drop:

Using the above curves, the pipe diameter can be sectected inmediately. The curves show that the main cause of the pressure difference between the inlet and outlet of the installation is due to the loss in straight runs (blue curve). The head loss in fittings (black curve) is small and varies slightly when changing the diameter. Yellow curve is due to the difference in height between the inlet and outlet and has a constant value equal to the difference of the liquid column.

In the following example the pressure loss is shown against variations of flow rate:

Our recommendation is that if it is possible you should enter into the LFlow application the K , Kv or Cv values provided by the manufacturers as this is the way to get more accurate values. However, this information sometimes is not available for many fittings as elbows , reducers , tees, etc., so it will have to be used the database. The database calculates the loss coefficient for the selected diameter. Using this fittings database has an important advantage, that is the possibility of obtaining a graph showing how the pressure loss changes for different diameters. This is of great interest when designing the installation as it helps for the selection of the diameter of the line. It should be taken as an estimatation since these values have been determined empirically and reflected in different literature and standards, but because of its dependence on factors such as the exact geometry of the element and its diameter, different sources show different values for the same type of fitting. However, as mentioned earlier, in many cases these losses may even be negligible, especially for very long pipes with relatively few accessories. In these cases , the uncertainty introduced will not be relevant.

In practice, most of the installations work with turbulent flows.

L Flow can show a chart for pressure drop as a function of flow rate. This chart includes curves for pressure loss in straight pipe run, pressure loss in fittings and difference in pressure due to elevation. You can compare this curves with the pump curve to see the actual operating point

Yes, the software allow the user for most of the paramenters to select between different engineering units.

Yes, all the reports show a button for printing.

Yes, do not hesitate to contact us and let us know your requirments.

You will need to have installed .NET Framework 4 from Microsoft o any compatible version. This software comes installed by default with Vista, Windows7, Windows8 and sometimes with Windows XP. In case it is not already installed you can download it for free from the Microsoft website.

*------ FOR
MORE INFORMATION DO NOT HESITATE TO CONTACT US ------*