CorroVenta A15ES, User Manual

Page: 11 / 67

A15ES
© Corroventa Avfuktning AB 2022.05 11 (67)
Dehumidification theory and methods
Relative humidity and its effect on substances
All air contains moisture, sometimes more, sometimes less although the naked eye cannot see it until
it condenses in small droplets on, for instance, a metal or glass surface. Already before it is visible
however, the moisture affects substances and production processes, causes corrosion and micro-
organism growth.
Air humidity is measured and referred to in terms of Relative Humidity (%RH) which is the ratio
between how much water it does contain and how much it can contain at given temperature and
pressure. The higher the temperature, the more water the air can contain but it is still the Relative
Humidity that is important and that needs to be controlled if one wants to prevent corrosion or
mould growth.
At RH 100% the air is saturated – there is fog and the moisture condensates in small droplets.
Already at RH 60% steel corrodes and at 70% there is a risk for mould growth. As a rule of thumb, RH
50% is a good climate for most substances.
How to select dehumidifier type
The adsorption principal has, compared to condensation drying, the advantage of a lower ambient
temperature dependency. Adsorption functions even well below the freezing point while the
capacity of a condensation dehumidifier inevitably decreases rapidly with falling temperature,
something that is depicted in the diagram below to the left.
As a rule of thumb, a general aid in the selection of type, it can be said that adsorption is the primary
choice for drying of unheated spaces or when material is to be dried. Adsorption dehumidifier
produces dehumidifier air, generates a greater reduction of water content measured in grams per
kilogram (Δx), and consequently creates a greater water vapor pressure difference which is directly
correlated to the drying speed. Drying of insulation such as floor structures are dried with combined
use of turbines, high pressure fans, installed for either suction or pressure drying.
Condensation dehumidifiers are, in accordance with the diagram above, used in hot and humid
conditions provided the goal and aim is drying of rooms, ambient air.
Condensation dryer
Superior within blue area.
Functions within yellow area.
Low or no function in red area.
Adsorption dryer with air-cooled
condensor
Functions within dashed area.
Adsorption dryer
Superior within red area.
Functions in yellow and blue area.
Transition zone
Temperature, °C
% RH
Dry air quality, 20°C
Dry air RH%
Process air RH%
Condensation dryer
Adsorption dryer