Selecting the correct membrane
The precise drying time will depends on a number of variables such as starting and target humidity, air temperature, volume, leakage and so on. The following tables have been prepared to give users an indication of drying times. We recommend you undertake your own tests. If you are interested in scientific models for estimating drying times use the contact us section to obtain the relevant links.
We provide a number of graphs and tables to aid selection of the correct Rosahl element. They are provided for guidance only as every application is different. See notes on humidity
Rosahl has a half-life of about six years when operated 24/7. This is extended when operating time for shorter periods ot time. We recommend over-sizing the membrane where practicable to allow for a decline in performance over time.
Economy of selection
For different enclosure sizes we recommend different models or Rosahl. If the initial drying time is not critical, and the enclosure remains closed for the majority of time, or you have a lower starting humidity, it is often possible to use a smaller membrane.
It is also important to consider the volume of air inside the enclosure rather than the external dimension. For example if your enclosure is 50% full by volume of non porous material, then the space to be dehumidified will be reduce by a similar amount.
Selection of membrane by volume and target humidity
Catalogue selection chart for Rosahl membranes only
Rosahl membrane only (no power supply or humidity controller)
|Applicable volume m³ *1||<0.002||<0.002||<0.5||<1||<2|
|Element Terminal Voltage||3VDC|
|Power Consumption (W) *2||0.08||0.08||2||3||4|
|Operating temperature (°C)||-10 to +50|
Notes: *1 Assumes sealed state enclosure. *2 Average power consumption over a year. *3 M12 x P0.5 thread
The following graphs provide an indication of drying performance under different conditions. The characteristics of the graphs may vary depending on the material in the container and the degree of air-tightness. If the container contains absorbent material the membrane induces release of moisture from the material, which may slow de-humidification inside the container. The dehumidifying capacity of the membrane varies according to the absolute water amount inside the container.
Typical drying curve for RD & PD series
Typical drying performance for a 50 litre container
Typical drying performance for the MDL-5 membrane