EFFECTIVE HUMIDITY CONTROL
IS ESSENTIAL IN INDUSTRIAL
ENVIRONMENTS -
FOR PROCESSES AND PEOPLE.
John Barker of Humidity Solutions explains
Pharma dehum – desiccant dehumidifier being
installed into a pharmaceutical application to
provide low humidity control “20%rh)
umidity control is essential
in any indoor environment
for the health of the
occupants and the building
fabric. In a manufacturing
environment it can also affect the
integrity of stored materials and impair
the reliability of machinery.
H
In terms of measuring humidity, we use
the term ‘relative humidity’ – or RH - to
describe the relationship between the
temperature of air and the amount of
moisture it can hold.
When there are problems with RH in
UK industrial environments it is usually
because the RH is too low, potentially
leading to dehydration and drying out of
eyes and respiratory surfaces. Low RH also
increases the spread rate of pathogens
such as the influenza virus and has been
linked with the intensity of chemical
pollution caused by gases from materials
used inside the buildings.
These issues are reflected in the
environmental variables identified in
HSE Guidance note 194 (4) - in relation to
maintaining workplace health, safety and
welfare.
Low RH will also cause various materials
(e.g. timber) to dry out very quickly.
Additionally, it makes occupants feel
colder, so they turn the heating up, which
increases energy consumption. Ironically,
raising the temperature reduces the RH
even further, exacerbating the problem.
Taking control
Therefore, it makes commercial sense
to ensure effective humidity control
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PECM Issue 30
Hydrojet – Airtec high pressure water humidifier
installed at a plastic production facility
to prevent static
in industrial environments, wi th a
view to maintaining RH between 40%
and 60%. This will usually mean using
humidification to raise the RH and
choosing the right system is essential.
Energy consumption, maintenance
requirements and location of the
humidification plant should all be
considered. Traditionally, the solution
has been to heat water to produce steam
and this is still an appropriate option for
some projects. However, high pressure,
low energy systems using cold water
are becoming increasingly popular in
industrial applications.
Steam humidification
SKE – Steam humidifier installed in a clean room air
handling unit to provide sterile humidity control
Another consideration is where to locate
the humidification plant. Gas-fired units
tend to have a relatively small footprint
and can be skid-mounted for installation
outside the building. Electric units can
also be weatherproofed.
Low energy, high pressure
A lower energy alternative to steam
generation is to spray water through
nozzles, at low or high pressure, directly
into the space or into ductwork. Such
systems also need to incorporate anti-
bacterial measures such as ultra violet
disinfection and can be combined with
demineralised or reverse osmosis water.
There are several ways of generating
steam for humidification and the
optimum solution will depend on the
project. For example, electrode boilers will
not supply more than 90kg/hr. of steam,
while resistive generators can provide up
to 120kg/hr for a single unit and modular
gas-fired humidifiers will deliver up to
400kg/hr. All forms of adiabatic humidification use
less energy than self-generating steam
humidifiers. Low pressure nozzles use
pressurised air, so energy is consumed by
the air compressor. High pressure nozzles
take the energy for atomisation from
high pressure water, so the high pressure
pump is the main energy consumer, albeit
very low.
As a rule of thumb, it takes 0.73kW of
heat to produce 1kg of steam, though
distribution and other losses might add
as much as a further 20%. In most cases,
gas-fired humidifiers will offer higher
efficiency with a lower carbon footprint,
compared to mains electricity. Gas fired
units may also prove less costly to install
because electric humidifiers have heavy
cabling requirements. Summary
In hard water areas the potential for
limescale formation cannot be ignored
and demineralised water is often
recommended. Further information:
www.humiditysolutions.co.uk
Given all of the factors discussed here, it is
clear that achieving acceptable humidity
control depends on addressing a number
of variables within each project. For that
reason, it makes sense to team up with
companies that have a comprehensive
range of different humidity solutions and
the expertise to apply them to optimum
effect.