The disclosure concerns a device suitable for removing air from water under both zero and one 'g' gravity conditions. The device is comprised of a pair of spaced membranes on being hydrophobic and the other being hydrophilic. The air-water mixture is introduced into the space therebetween, and the selective action of the membranes yields removal of the air from the water

Booth, F. W.

Bruce, R. A.

English

NASA Technical Reports Server

Booth et al. 
[54] AIR REMOVAL DEVICE 
[75] Inventors: Franklin W. Booth, Hampton; Robert 
A. Bruce, Newport News, both of 
Va. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[73] Assignee: The United States of America as 
[21] Appl. NO.: 662,181 
[22] Filed: Feb. 27, 1976 
Related U.S. Application Data 
[63] Continuation of Ser. No. 810,576, Mar. 26, 1969, aban- 
doned. 
[51] Int. C l . 3  .............................................. BOlD 53/22 
[52] U.S. Cl. .................................... 55/158; 210/321.1 
Field of Search ................... 55/158, 159; 210/321 [58] 
1561 References Cited 
U.S. PATENT DOCUMENTS 
2,756,206 7/1956 Gobel ............................. 210/321 A 
. 3,523,408 SA970 Rosenberg ............................ 55/159 
Primary Examiner-John Adee 
Attorney, Agent, or Firm-Howard J. Osborn; John R. 
Manning 
P71 ABSTRACT 
This disclosure concerns a device suitable for removing 
air from water under both zero and one “g” gravity 
conditions. The device is comprised of a pair of spaced 
membranes, one being hydrophobic and the other being 
hydrophilic. The air-water mixture is introduced into 
the space therebetween, and the selective action of the 
membranes yields removal of the air from the water. 
3,415,038 12/1968 Merten et al. .................... 55/158 X 
3 Claims, 2 Drawing Figures 
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AIR REMOVAL DEVICE 
ORIGIN O F  THE INVENTION 
The invention described herein was made by employ- 
ees of the U.S. Government and may be manufactured 
and used by or for the Government for governmental 
purposes without the payment of any royalties thereon 
or therefor. 
This is a continuation of application Ser. No. 810,576 
filed Mar. 26, 1969, now abandoned. 
Life support and other systems incorporated into 
manned spacecraft have many points within which 
water is formed, each such point creating the possibility 
of mechanical infiltration or dissolving of air in the 
water system. The frequent changes in water stream 
pressure and/or temperature may result in dissolved air 
being released, and a significant quantity of air bubbles 
may collect in the system. This air may produce a dete- 
rioration in performance in some subsystems, such as 
electrolysis units, wherein it may displace the electro- 
lyte, or in holding tanks where collection of air would 
cut down on the usable volume of the tanks. 
This air must be bled back to the cabin atmosphere 
under zero gravity conditions, and for ground testing 
purposes, any air bleeding device used must operate 
under zero gravity conditions. 
Therefore, it is an object of the present invention to 
provide an air separating device which will remove 
dissolved or entrained air from a water stream under 
zero or one “g” gravity conditions. 
This object is attained by the use of a pair of porous 
membranes, one water-wettable or hydrophilic and the 
other nonwettable or hydrophobic. Introducing the 
air-water mixture under pressure between these mem- 
branes produces a separation due to the selective pas- 
sage of air and water through the membranes. 
The specific embodiment disclosed to illustrate the 
invention may be better understood by reference to the 
drawings wherein FIG. 1 is a plan view of the air sepa- 
ration device and FIG. 2 is a view of the section taken 
along the line 2-2 in FIG. 1. 
Referring to FIG. 2, the device is indicated as 10 and 
includes a housing made up of a pair of plates 12 and 14 
fastened together by screws 16 and sealed about their 
periphery by an appropriate sealing compound. A cav- 
ity 18 is formed between these plates 12 and 14 by cut 
out portions in the inner face of each plate. 
Occupying this cavity are a pair of porous mem- 
branes 20 and 22 secured about their periphery with a 
spacer 23 and three sheets of woven mesh 24,26 and 28 
which serve to position the membranes and have an- 
other function to be hereinafter described. The mem- 
branes are constructed so that membrane 20 is hydro- 
phobic while membrane 22 is constructed so as to be 
hydrophilic. Such membranes are widely available and 
well known in the prior art and may be made of a wide 
variety of materials with a wide variety of surface treat- 
ments to obtain these characteristics. 
These characteristics of the membranes will serve to 
create a selective barrier as the water will not pass 
through the pores of the nonwettable membrane 20 due 
to negative capillary forces, as long as the pressure 
differential motive force across the barrier is lower than 
the negative capillary force. For this purpose, it has 
been found that for a typical nonwettable material hav- 
ing 0.45 micron pores a pressure difference of 6 psi 
between inlet and exhaust air produced satisfactory 
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selective passage of the air with no water transfer. Of 
course, variances in pore size and the contact angle of 
the material with the water would vary this value. 
On the other hand, since the water is attracted to the 
membrane 22, the pores will be occupied by the water, 
and no air can pass through. 
These membranes divide the cavity 18 into three 
chambers 30, 32 and 34. 
Central chamber 34 serves to admit the air-water 
mixture and bring it into contact with the membranes, 
with the screen 26 causing the air bubbles therein to be 
brought into contact with the membrane 20. The air- 
water mixture is introduced from the source via tube 36, 
and enters the annular chamber 38. From thence the air 
passes into the central chamber 32 via openings 40 
through spacer 23. The air passes through the mem- 
brane 20, and is collected by the screen 24 and passes 
into exhaust tube 42, while the water passes through the 
membrane 22, is collected by the screen 28 and passes 
out the tube 44. 
In order to remove dissolved air from the water, a 
degassing device 46 may be placed upstream from the 
device, which may either heat the water to drive out the 
air and create bubbles or may reduce the pressure of the 
water also producing air bubbles from dissolved air 
coming out of solution. Thus, the device may also oper- 
ate to remove both entrained and dissolved air. 
In order to create flow across the membranes, a pres- 
sure differential must be set up, that is the pressure in 
chamber 32 must be greater than that in chambers 30 
and 34, and a pump 48 upstream might be necessary 
depending on the application and the nature of the sys- 
tem incorporating the device. 
In describing the specific embodiment a specific ar- 
rangement has been described for the sake of clarity but 
it is understood the invention may be practiced in other 
forms without departing from the spirit thereof. 
What is claimed as new and desired to be secured by 
Letters Patent of the United States is: 
1. A separator device for separating a mixture of gas 
entrained in water comprising: 
a hydrophilic porous membrane; 
a hydrophobic porous membrane; 
enclosure means forming a fluid chamber including 
portions of said membranes and means spacing said 
membranes parallel to each other including a 
spacer member extending around said portions; 
input means for directing said mixture to said cham- 
ber and including a chamber extending about the 
spacer and also including a plurality of openings 
extending through said spacer into the fluid cham- 
ber; 
means for creating a pressure differential across said 
portion of said hydrophilic porous membrane so as 
to cause outward flow of said water; and 
means for creating a pressure differential across said 
portion of said hydrophobic porous membrane and 
for creating an outward movement of said gas 
without overcoming the negative capillary forces 
which form a water barrier, whereby selective 
transfer of gas and water through said portions 
produces separation of said mixture in both zero g 
and one g environments. 
2. A separator device for separating a mixture of a gas 
entrained in a liquid comprising: 
a hydrophilic porous membrane; 
a hydrophobic membrane; 
4,302,223 
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enclosure means forming a fluid chamber including 
portions of said porous membranes spaced adjacent 
and parallel to each other; 
input means for directing said mixture to said cham- 
ber; 
means for creating a pressure differential across said 
portion of said hydrophilic porous membrane so as 
to cause outward flow of said liquid; 
means for creating a pressure differential across said 
portion of said hydrophobic porous membrane so 10 tioned between said porous membranes is a screen. 
out overcoming the negative capillary forces act- 
ing on said gas; 
means positioned between said porous membranes for 
bringing said mixture into contact with said mem- 
branes whereby selective transfer of gas and water 
through said portions produces separation of said 
mixture in any environment including space. 
3. The separator of claim 2 wherein said means POSi- 
s 
as to create an outward movement of said gas with- * * * * *  
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Air removal device

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