Water content in the air
For right choice of dehumidification equipment is essential to know your need for air dehumidification. These needs can be determined in the following paragraphs.
An online PsychroCalc is available for quick determination of psychrometric properties.
1. Estimation what clima-conditions are required
What is the problem causing the humidity? It is the problem of relative or absolute humidity? Of course, it is necessary to know the temperature of the air in order to calculate the size dehumidifier.
2. Moisture load from ventilation
Ventilation should be minimized in the process of air dehumidification in the space. Ventilation is normally in every area of opening doors or when people ventilate windows. At very tight rooms can be as low as 0.1 x volume exchange/h or less, small room with frequent door openings with air exchange 0.3 x volume/h. At normal ventilation the air is fresh outdoor air, its parameters must be known.
mV = 1,2 • V • (x1-x2) / 1000
mV = moisture load from ventilation [kg/h]
V = total ventilation [m3/h]
x1 = water content in the air, fresh air [g/kg]
x2 = water content in the air, inside room [g/kg]
3. Moisture load from people
A man is the source of moisture when breathing or when you sweat. A person who is calm, issued approximately 0.05 kg/h, while the working man released from your body up to 0.3 kg/h.
4. Moisture load from open water
The warmer water evaporates more moisture in the ambient air. Also dry air and strong air flow over the surface causes higher evaporation rate.
mw = s • A • (x1-x2) / 1000
mw = moisture load from open water [kg/h]
s = evaporating coeficient, nromally 25 [kg/(m2 h)]
A = water surface [m2]
x1 = water content in saturated air refered to water temperature [g/kg]
x2 = water content in the air, inside room [g/kg]
5. Moisture load from the product
It is very difficult to estiamte moisture amount that evaporates from the product, especially in those cases where it is influenced by many variables. A rough estimation can be done on a case by case basis.
6. Moisture load by diffusion
In some cases, the load of moisture by diffusion processes are provided through building walls. In comparison to the above mentioned loads this source is normally negligible. To clarify this effect, we have a sample calculation, which can determine moisture load.