Abstract:

The fundamental definition of a pressure loss coefficient implicitly assumes that the flow at the reference sections is uniform or one-dimensional. In contrast, the interpretation of measurements from experiment or computation uses measurements made in flow that will usually not be uniform at either the measurement sections or the reference section. This Memorandum explores the implications of this dichotomy which leads to the need to make choices in the derivation of a pressure-loss coefficient.

The essential requirement is to define appropriate mean values to represent the profiled flow in a one-dimensional manner. This Memorandum focuses primarily on derivation or application of "standard" pressure loss coefficients for which the flow at the measurement sections is a fully-developed axial flow. The derivation applies to flow of incompressible fluids, the case of compressible fluids is more complex and will be considered elsewhere.