Understanding the flow of compressible fluids in pipes is necessary for a robust design of process plants. The main difference between incompressible fluid, like water, and compressible fluid, vapor, is the greater change in pressure and density. This makes the calculations for compressible fluids slightly more difficult. Understanding how the fluid properties change is critical when dealing with these fluids. The ability of compressible fluids, unlike incompressible fluids, to "choke" further complicates matters.

Terminology is critical when we speak of Special Cases. Literature is inconsistent in referring to the various areas of the Moody Diagram. As stated previously, I will strive to use terminology consistent with the original article of Moody (1944) and the Moody Diagram shown in that paper.

As an alternative to solving Colebrook using iteration, User Defined Functions (UDFs) can be written that use a variety of methods to solve Colebrook. In this series, we will examine the use of an iterative-like approach that doesn't require the initiation of the built-in Iteration Function (Goal Seek).

In 1944 Lewis F. Moody, Professor, Hydraulic Engineering, Princeton University, published "Friction Factors for Pipe Flow". The work of Moody, and the Moody Diagram on page 672 of the published transactions, has become the basis for many of the calculations on friction loss in pipes, ductwork and flues. While there are modified versions of the original Moody Diagram, I will strive to use the original diagram as the basis for terminology used here.

A typical chemical process plant involves fluid flow devices such as pipes and valves. Fluid transport equipment such as pumps, compressors are employed for moving fluid from one unit operation to another. Drying equipment such as fluidized beds, cyclone driers, spray driers form an essential part of many processes.

Operating a pump under the condition of cavitation for even a short period of time can have damaging consequences for both the equipment and the process. Operating a pump at low flow conditions for an extended duration may also have damaging consequences for the equipment.

The operating manual of any centrifugal pump often starts with a general statement, "Your centrifugal pump will give you completely trouble free and satisfactory service only on the condition that it is installed and operated with due care and is properly maintained."

In 1994, the Belgian company Domo, a leading European manufacturer of floorings, took over the caprolactam complex in Leuna. The reasons were self-evident: The caprolacta produced in Leuna is the chemical feedstock for manufacturing the chemical fibres which are then woven into carpets.