Homogeneity index

A high homogeneity index corresponds to a short humidification distance.

A small homogeneity index corresponds to a long humidification distance.

The homogeneity index is a dimensionless measure of the quality of steam distribution systems. The homogeneous moisture distribution is crucial for avoiding moisture stratification in subsequent components and enabling short humidification distances . The introduction of steam is the better, the finer the steam is dosed and the larger it is distributed over the existing air cross-section. The number and arrangement of the steam distributors as well as the type, number and surface distribution of the steam nozzles play a decisive role.

calculation

The homogeneity index is calculated according to the following formula:

${\displaystyle H_{INX}=n_{DA}\cdot n_{DV}\cdot n_{D}\cdot {\frac {A_{Luft}}{{\dot {m}}_{Dampf}}}}$

The individual symbols stand for the following quantities:

• ${\displaystyle H_{INX}}$ - homogeneity index [dimensionless number]
• ${\displaystyle n_{DA}}$- Steam outlet constant: for one-sided; for two-sided. ${\displaystyle n_{DA}=1{\frac {kg}{m^{2}\cdot h}}}$ ${\displaystyle n_{DA}=2{\frac {kg}{m^{2}\cdot h}}}$
• ${\displaystyle n_{DV}}$ - Number of steam distributors
• ${\displaystyle n_{D}}$ - Number of nozzles
• ${\displaystyle A_{Luft}}$ - air cross section [m²]
• ${\displaystyle {\dot {m}}_{Dampf}}$ - humidification performance [kg / h]

example

Humidification system 1:

• Model Esco DR73-A5.10-8 : 5 nozzle assemblies with 20 nozzles each, so 100 nozzles in total; two-sided steam outlet.
• Steam output: 100 kg / h
• Air cross-section: 4 m²

${\displaystyle \Rightarrow H_{INX}=2\cdot 5\cdot 100\cdot {\frac {4}{100}}=40}$

Humidification system 2:

• Alternative model: 2 nozzle holders with 45 nozzles each, i.e. 90 nozzles in total; one-sided steam outlet.
• Steam output and air cross-section as under humidification system 1.

${\displaystyle \Rightarrow H_{INX}=1\cdot 2\cdot 90\cdot {\frac {4}{100}}=7{,}2}$

Because of the higher number of nozzle holders and nozzles and their arrangement, the homogeneity of the steam introduction of the humidification system 1 is therefore significantly higher, which results in a short humidification distance.

literature

• Ernst-Rudolf Schramek (Eds.), Hermann Recknagel , Eberhard Sprenger: Pocket book for heating + air conditioning technology. 76th edition, Oldenbourg Industrieverlag, Munich 2005, ISBN 978-3-8356-3301-8 .