Inside a closed chamber, how can relative humidity be maintained using bubbling technique?
Bubbling normally results in a saturated air at the temperature. So you need another completely dry air flow to be mixed with the saturated air in the chamber for a designed RH. Since the flow rates govern the resulting RH, the chamber has to equip an outlet and becomes unclosed.
If your bubbling means a heat-mass exchange at a saturator with lower water temperatures, the camber remains closed but the attainable RH range will be greatly limited because the lowest dew point temperature has to be at most 4°C.
Thank you Mr. Shinsaku for the valuable information. Is there any reference article or international standard related this ?
The first half of my comment was related to "Flow-division method" and the latter half to "Two-temperature method." Information of each method can be obtained with the internet search. See for instance:
http://info.owlstonenanotech.com/rs/owlstone/images/Humidity%20Generation%20and%20Humidity%20Measurement.pdf
If you want to maintain RH, you need to control humidity (constant dewpoint) and temperature. Dewpoint is generally uniform in a thermostatic chamber, but temperature can be inhomogen.
http://www.npl.co.uk/publications/good-practice-online-modules/humidity/
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