Hausner ratio

The Hausner ratio is a number that is correlated to the flowability of a powder or granular material. It is named after the engineer Henry H. Hausner (1900–1995).[1][2]

The Hausner ratio is calculated by the formula

${\displaystyle H={\frac {\rho _{T}}{\rho _{B}}}}$

where ${\displaystyle \rho _{B}}$ is the freely settled bulk density of the powder, and ${\displaystyle \rho _{T}}$ is the tapped bulk density of the powder. The Hausner ratio is not an absolute property of a material; its value can vary depending on the methodology used to determine it.

The Hausner ratio is used in a wide variety of industries [3][4][5][6][7] as an indication of the flowability of a powder.[8] A Hausner ratio greater than 1.25 - 1.4[9] is considered to be an indication of poor flowability. The Hausner ratio (H) is related to the Carr index (C), another indication of flowability, by the formula ${\displaystyle H=100/(100-C)}$. Both the Hausner ratio and the Carr index are sometimes criticized, despite their relationships to flowability being established empirically, as not having a strong theoretical basis. Use of these measures persists, however, because the equipment required to perform the analysis is relatively cheap and the technique is easy to learn.