TS EN ISO 80000-11

TS EN ISO 80000-11 is the part of the Quantities and Units series that gives the names, symbols and definitions of characteristic numbers used in describing transport and transfer phenomena. It brings commonly used dimensionless numbers into a shared technical framework, helping engineers and scientists discuss flow, mass transfer, heat transfer and related processes with consistent terminology.

The technical role of characteristic numbers

In general technical use, characteristic numbers express the balance between competing physical effects as a ratio or single measure. Some compare inertial and viscous effects, while others describe the relative importance of convection and diffusion. For that reason, they are central to scaling experimental results, assessing similarity and comparing different systems. The focus of this standard is terminology and symbol consistency; it should not be read as prescribing a calculation method or a design rule.

Why this scope matters in practice

The document is limited to characteristic numbers used for transport and transfer phenomena. That helps users keep terms in textbooks, technical reports and scientific publications aligned in meaning. The standard addresses which names, symbols and definitions to use, not how to compute specific values. In this way it reduces terminological ambiguity across heat, mass and momentum transfer work and supports clearer technical communication.