This information is part of the Modelica Standard Library maintained by the Modelica Association.

This Real type defines the absolute roughness of the inner surface of a pipe or fitting, i.e., the absolute average height of surface asperities. It has usually to be estimated. In [Idelchik 1994, pp. 105-109, Table 2-5; Miller 1990, p. 190, Table 8-1] many examples are given. As a short summary:

Type of pipe		Roughness
Smooth pipes	Drawn brass, copper, aluminium, glass, etc.	0.0025 mm
Steel pipes	New smooth pipes	0.025 mm
	Mortar lined, average finish	0.1 mm
	Heavy rust	1 mm
Concrete pipes	Steel forms, first class workmanship	0.025 mm
	Steel forms, average workmanship	0.1 mm
	Block linings	1 mm

References

Idelchik I.E. (1994):

Handbook of Hydraulic Resistance. 3rd edition, Begell House, ISBN 0-8493-9908-4

Miller D. S. (1990):

Internal flow systems. 2nd edition. Cranfield:BHRA(Information Services).

Real	Quantity: Length Unit: m Display Unit: mm Restricted Range: 0 to +Inf