Relationship of absolute dehumidifying capacity and ambient

Is the absolute dehumidifying capacity affected by ambient temperature and humidity?

Rosahl membranes remove moisture from an enclosure. The manufacturer publishes dehumidifying capacity at 30° C and 60% RH as an indication of performance. This is not the absolute dehumidifying capacity of the membrane

Exactly how much moisture they remove depends on the temperature and absolute humidity (g/m³) in the enclosure. The capacity changes as the absolute moisture in a cabinet changes. This information is reflected in the drying curves published by the manufacturer

Drying curves for Rosahl dehimidifying membranes

Absolute dehumidifying capacity

As an example, we consider a size 10 membrane M-10J1R. The published capacity of this device is 29g/day. This is based on ambient conditions of 30° C and 60% RH. Under these conditions, the absolute humidity is 19.1g/m3 (from tables)

The M-10J1R membrane capacity of 29g/day changes as temperature and humidity change as follows:

At 30℃・40％RH

Absolute moisture is 12.7g/m3 → 29*(12.7/19.1) =19.3g/day membrane capacity

At 30℃・90% RH

Absolute moisture is 28.6g/m3 → 29*(28.6/19.1) =43.4g/day membrane capacity

At 20℃・60％RH

Absolute moisture is 10.5g/m3 → 29*(10.5/19.1) =15.9g/day membrane capacity

At 40℃・60% RH

Absolute moisture is 33.2g/m3 → 29*(33.2/19.1) =50.4g/day membrane capacity

 

Summary

At 30℃, when RH is higher than 60% the membrane will remove more moisture, and when RH is less than 60% it removes less moisture than the published capacity

At 60% RH, when temperature is lowerer than 30° C the membrane removes less moisture, and when temperature is above 30° C it removes more moisture than the published capacity

 

Model	Dehumidifying capacity*
PD4/PD5	42 mg/day
PD2/PD3/RD3/RD4	84 mg/day
M-2J1R	2g /day
M-3M1R	2.9g /day
M-3J1R/MDL-3	4g /day
M-5J1R/MDL-5 S-5J1/S-5T1	8g /day
M-7J1R/MDL-7 S-7J1/S-7T1	16g /day
M-10J1R S-10J1/S-10T1	29g /day
	* Initial dehumidifying capacity of a new membrane at 30C and 60% RH