+44 203 286 8189 steve.jones@westside-int.com

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 moisture in a cabinet changes. The drying curves published by the manufacturer reflect this information.

Drying curves for Rosahl dehumidifying membranes

 

Absolute dehumidifying capacity

As an example, a size 10 membrane M-10J1R. The published capacity of this device is 29g/day. This assumes ambient conditions of 30° C and 60% RH. Under these conditions, the absolute humidity is 18.21g/m3 (from table below).

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

At 30℃・40RH

Absolute humidity is 12.1g/m3 → 29*(12.1/18.2) =20.2g/day membrane capacity.

At 30℃・90% RH

Absolute humidity is 27.2g/m3 → 29*(27.2/18.2) =44.2g/day membrane capacity.

At 20℃・60RH

Absolute humidity is 10.4g/m3 → 29*(10.4/18.2) =16.6g/day membrane capacity.

At 40℃・60% RH

Absolute humidity is 30.6g/m3 → 29*(30.6/18.2) =48.8g/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 lower than 30° C the membrane removes less moisture, and when temperature is above 30° C it removes more moisture than the published capacity.

 

Membrane dehumidifying capacities

ModelDehumidifying capacity
PD4, PD542 mg/day
PD2, PD3, RD3, RD484 mg/day
RS1, RS2210 mg/day
M-1J1R1 mg/day
M-2J1R2 g/day
M-3M1R2.9 g/day
M-3M1R, MDL-34 g/day
M-5J1R, MDL-5, S-5T19 g/day
M-7J1R, MDL7, S-7T116g /day
M-10J1R, S-10T129 g/day

 

Moisture per cubic metre of air

g/m310%20%30%40%50%60%70%80%90%100%
50°C8.3
16.624.833.141.449.75866.274.582.8
45°C6.513.119.626.132.639.245.752.258.765.3
40°C5.110.215.320.425.530.635.740.845.951
35°C47.911.815.819.723.727.631.635.539.5
30°C36.19.112.115.118.221.224.227.230.3
25°C2.34.66.99.211.513.816.118.420.723
20°C1.73.55.26.98.610.412.113.815.517.2
15°C1.32.63.85.16.47.7910.211.512.8
10°C0.91.92.83.84.75.66.67.58.49.4
5°C0.71.422.73.44.14.85.46.16.8
0°C0.511.51.92.42.93.43.94.44.9
-5°C0.30.711.41.72.12.42.73.13.4
-10°C0.20.50.711.21.41.71.92.12.4
-15°C0.20.30.50.60.811.11.31.51.6
-20°C0.1
0.20.30.40.50.70.80.911.1