Abstract:
A degassing module is adapted for degassing a liquidous fluid at relatively high throughput flow rates. The degassing module includes a tubular separation membrane that is helically wound within an interior chamber of a degassing module housing. The helically wound tubular separation membrane is disposed in an axial flow gap of predetermined proportions that maximizes fluid flow dynamics in reducing the gas transport resistance from the liquid phase across the membrane. Typically, the helically wound tubular separation membrane is positioned in the gap with radial spacings to surfaces bounding the gap, thereby forming axial flow channels circumaxially inwardly and/or outwardly of the wound tubular membrane.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 61/839,746, filed on Jun. 26, 2013 and entitled “Fluid Degassing Module with Helical Membrane,” the content of which being incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to fluid degassing systems generally, and more particularly to apparatus for removing gasses from a liquid in a relatively high flow rate regime. 
     BACKGROUND OF THE INVENTION 
     The removal of entrained gasses from liquids is an important exercise in a variety of manufacturing and/or analytical processes. An example process in which liquid degassing is widely utilized is in liquid chromatography applications. The presence of dissolved gasses can be undesirable in such applications, wherein the presence of dissolved gasses interferes with the functionality or accuracy of the application. 
     In the case of liquid chromatography, for example, dissolved gasses in the chromatographic mobile phase can manifest itself in the form of bubbles, which can cause noise and drift in the chromatographic detector. Moreover, the existence of gas bubbles can cause erroneous absorption signatures at the detector. 
     As chromatographic analyses diversify, applications with relatively high fluid flow rates (&gt;20 ml/min) are becoming more common, especially for separating and purifying compounds from a mixed solution after a synthesis or from natural extracts. Such flow rate in liquid chromatography is known as “preparative scale” liquid chromatography, and normally involves mobile phase (solvent) flow of at least 20 ml/min, and may, in some cases, be between 100-250 ml/min. Analytical scale liquid chromatography, by contrast, typically involves mobile phase flow rates of 0.1-10 ml/min. A variety of degassing solutions are in place for analytical scale HPLC, with the most common utilizing semi-permeable (liquid-impermeable, gas-permeable) tubing in a flow-through arrangement, wherein the solvent mobile phase is driven through the lumen of the tubing within an environment conducive to the removal of gaseous species from the liquid solvent through the tubing wall. Such degassing systems are described in, for example, U.S. Pat. Nos. 3,751,879; 5,340,384; 5,980,742; 6,248,157; and 6,494,938, the contents of which being incorporated herein by reference. 
     The arrangements described and employed in conventional degassing systems, however, are inadequate to suitably degas the solvent flow rates utilized in preparative scale liquid chromatography. One approach to degassing in high solvent flow rate regimes is to use a plurality of tubular membranes as a hollow fiber bundle in a degassing module, wherein, in some cases, more than 100 hollow fiber separation membranes may be bundled together. Example hollow fiber degassing bundle arrangements are described in U.S. Pat. Nos. 3,339,341; 3,422,008; and 4,351,092. Typically, however, manufacturing of such hollow fiber degassing modules is difficult, particularly in potting the fibers within the housing when the fibers are fabricated from low surface energy materials such as PTFE or Teflon™ AF (which are desired for their membrane properties). 
     Another approach to liquid degassing in high flow rate regimes is the use of a flat membrane in a degassing module. However, manufacturing such flat degassing membrane modules has proven difficult, both to seal the flat membrane within the module, as well as to manufacture a pin-hole free, uniform flat film. 
     It is therefore an object of the present invention to provide a degassing module that is both effective in degassing fluids at high flow rates, and is capable of being economically and reproducibly manufactured. 
     SUMMARY OF THE INVENTION 
     By means of the present invention, relatively high flow rate liquidous fluids may be economically degassed. A degassing module for performing the liquid degassing includes a tubular separation membrane that is helically wound within an interior chamber of a degassing module housing. The wound tubular membrane may be helically positioned in an axial gap between opposed surfaces, with a predetermined spacing between the membrane and one or more of the opposed surfaces. 
     In one embodiment, a degassing module of the present invention includes a housing defining an interior chamber and a housing axis, with the housing having an evacuation port opening to the chamber, and a fluid inlet port and a fluid outlet port each opening to the chamber for permitting flow of the fluid through the interior chamber. The degassing module further includes a cell secured to the housing and having a length extending axially along the housing axis in the interior chamber. A tubular separation membrane is helically wound about the cell in a gap between an inner surface of the housing and an outer surface of the cell. The membrane defines a lumen that is in fluid communication with the evacuation port for evacuating the lumen. The membrane forms a gas-permeable, liquid-impermeable barrier between the interior chamber and the lumen. The degassing module further includes a housing strut extending from the inner surface of the housing to maintain the membrane in a spaced relationship from the inner surface of the housing, with a first spacing being defined radially between the membrane and the inner surface of the housing. A cell strut extends from the outer surface of the cell to maintain the membrane in a spaced relationship from the outer surface of the cell, with a second spacing being defined radially between the membrane and the outer surface of the cell. 
     In another embodiment, a degassing module of the present invention includes a housing defining an interior chamber and a housing axis, and having an evacuation port, a fluid inlet port, and a fluid outlet port. The degassing module further includes a cell secured into the interior chamber and extending axially along the housing axis to form a circumaxial gap in the interior chamber and radially bounded by a first surface and a second surface that is substantially parallel to the first surface. A tubular separation membrane defines a lumen that is in fluid communication with the evacuation port for evacuating the lumen. The membrane forms a gas-permeable, liquid-impermeable barrier between the interior chamber and the lumen. The membrane is helically wound about the cell in the circumaxial gap, and is supported to maintain a first spacing between the membrane and the first surface, and a second spacing between the membrane and the second surface. The first and second spacings are preferably between 50-500 micrometers. 
     A degassing system of the present invention includes a liquidous fluid source and a degassing module having a housing defining an interior chamber and a housing axis, with an evacuation port, a fluid inlet port, and a fluid outlet port. The degassing module further includes a cell secured in the interior chamber and extending axially along the axis to form a circumaxial gap in the interior chamber and radially bounded by the housing and the cell. A tubular separation membrane defines a lumen that is in fluid communication with the evacuation port for evacuating the lumen. The membrane forms a gas-permeable, liquid-impermeable barrier between the interior chamber and the lumen. The membrane is helically wound about the cell in the circumaxial gap, and is supported to maintain a first spacing between the membrane and an inner surface of the housing, and a second spacing between the membrane and an outer surface of the cell. The degassing system further includes a transfer conduit that fluidically couples the liquidous fluid source to the fluid inlet, and a pump for motivating the liquidous fluid from the liquidous fluid source through the interior chamber of the degassing module. A vacuum source is provided in the degassing system for evacuating the lumen through the evacuation port. 
     A method for degassing a liquidous fluid includes providing a degassing module having a housing defining an interior chamber and a housing axis, with an evacuation port, a fluid inlet port, and a fluid outlet port. The degassing module further includes a cell secured in the interior chamber and extending axially along the housing axis to form a circumaxial gap in the interior chamber and radially bounded by the housing and the cell. A tubular separation membrane defines a lumen that is in fluid communication with the evacuation port for evacuating the lumen. The membrane forms a gas-permeable, liquid-impermeable barrier between the interior chamber and the lumen. The membrane is helically would about the cell in the circumaxial gap, and is supported to maintain a first spacing between the membrane and the first surface, and a second spacing between the membrane and the second surface. The degassing method further includes motivating the liquidous fluid through the fluid inlet and into contact with the membrane in the interior chamber, and evacuating the lumen through the evacuation port. The liquidous fluid is then delivered from the interior chamber through the outlet port. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional schematic view of a fluid degassing module of the present invention; 
         FIG. 1B  is a cross-sectional view of the fluid degassing module of  FIG. 1A ; 
         FIG. 2  is a perspective view of a fluid degassing module of the present invention; 
         FIG. 3  is a schematic perspective view of a portion of the fluid degassing module of  FIG. 2 ; 
         FIG. 4  is a schematic perspective view of a portion of the fluid degassing module of  FIG. 2 ; 
         FIG. 5  is a schematic cross-sectional view of a portion of the fluid degassing module of  FIG. 2 ; 
         FIG. 6  is a schematic top cross-sectional view of a portion of the fluid degassing module of  FIG. 2 ; 
         FIG. 7  is a schematic top cross-sectional view of a portion of the fluid degassing module of  FIG. 2 ; 
         FIG. 8  is a cross-sectional schematic view of a portion of the fluid degassing module the present invention; 
         FIG. 9  is a cross-sectional schematic view of a portion of the fluid degassing module the present invention; 
         FIG. 10  is a cross-sectional schematic view of a portion of the fluid degassing module the present invention; 
         FIG. 11  is a cross-sectional schematic view of a portion of the fluid degassing module the present invention; 
         FIG. 12  is a cross-sectional schematic view of a portion of the fluid degassing module the present invention; 
         FIG. 13  is a cross-sectional schematic view of a portion of the fluid degassing module the present invention; and 
         FIG. 14  is a schematic diagram of a fluid degassing system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A degassing module  10  of the present invention may be incorporated in, for example, a liquid chromatography apparatus for degassing the mobile phase being analyzed in the chromatographic column. Degassing module  10  may be employed, however, in a variety of other liquid supply applications that rely upon degassed liquids in order to achieve and preserve consistent and high quality results. Other example applications include, for example, ink delivery systems such as in ink-jet printers, semiconductor wafer manufacturing processes, and pharmaceutical manufacturing. 
     An embodiment of degassing module  10  includes a housing  12  defining an interior chamber  14  wherein the fluid to be degassed may be contacted by a semi-permeable separation membrane  16 . In preferred embodiments, separation membrane  16  may be in the form of one or more lengths of tubing to form a gas-permeable, liquid-impermeable barrier between interior chamber  14  and a lumen of the respective tubular separation membrane  16 . One example of such a membrane is a non-porous fluorinated copolymer, such as a membrane formed from Teflon™ AF, available from DuPont. The separation membrane may be qualified for a specific application as having known permeation rates for certain gaseous species, as well as known selectivity values. Alternative separation membrane materials include microporous materials manufactured from PTFE, ePTFE, PVDF, polypropylene, polymethylpentene, and surface fluorinated versions of polypropylene and polymethylpentene. It is to be understood, however, that tubular separation membrane  16  may be fabricated from a variety of materials to accomplish the gas-permeable, liquid-impermeable barrier utilized in degassing applications. 
     Housing  12  may be formed as a single piece, or multiple-piece body, with the embodiment illustrated in  FIG. 1A  including a housing shell  18  and a housing cap  20  that is sealingly engaged to housing shell  18  at cap interface  22 . To enhance the sealing engagement between housing cap  20  and housing shell  18 , a gasket  24 , such as a rubber O-ring, may be provided in a gasket seat  26  of housing cap  20  to sealingly press between housing cap  20  and housing shell  18 . Housing  12  may preferably be fabricated from one or more relatively strong and inert materials to avoid undesired interactions with mobile phase flow through interior chamber  14 . Example housings  12  may be fabricated from stainless steel or other metals or metal alloys, or various polymer materials. 
     A cell  30  may be disposed in interior chamber  14  as a body about which tubular separation membrane  16  may be wound and/or through which fluid may be distributed into and/or out from interior chamber  14 . Cell  30  may be anchored to housing  12  for desired positioning within interior chamber  14 . In some embodiments, cell  30  may be integrally formed with, or secured to housing cap  20 , with this arrangement being illustrated in  FIG. 1A . Typically, cell  30  may be arranged axially within interior chamber  14  along a housing axis  32 . 
     In the embodiment illustrated in  FIGS. 1A and 1B , housing  12  includes a first evacuation port  40  and a second evacuation port  42  for receiving respective vacuum couplings  44  that fluidly couple a respective lumen of separation membrane tube  16  to a vacuum source for evacuating the lumen of separation membrane tube  16 . In operation, therefore, separation membrane tube  16  may be evacuated to a predetermined extent to generate a driving force for gas to diffuse through the tubular wall of separation membrane  16  from the fluid in interior chamber  14 . Gaseous species that diffuse through the wall of tubular separation membrane  16  may be removed through a respective first and second evacuation port  40 ,  42 . The concept of “vacuum degassing” is well-known in the art, though not typically employed as described above with an evacuation of the lumen of tubular separation membrane  16  and with the gas-containing liquid contacting the outer surface of the membrane wall defined by tubular separation membrane  16 . Such arrangement may be referred to as “outside-in” vacuum degassing. 
     The diffused gas may also or instead be evacuated from the lumen of tubular separation membrane  16  with a sweep gas. In a particular embodiment, an air bleed may be provided at port  42  so that environmental air is drawn through the lumen to sweep diffused gas through evacuation port  40  and to prevent condensation within the lumen of the tubular separation membrane  16 . 
     Housing  12  further includes a fluid inlet port  50  and a fluid outlet port  52  for receiving respective fluid coupling units  54  for communicating fluid into and out from interior chamber  14 . For the purposes hereof, the term “fluid” may include a gas-containing liquid, wherein a concentration of the one or more gaseous species is desired to be maintained below a threshold. The one or more gaseous species may be partially or completely removed from the liquidous fluid through operable contact with tubular separation membrane  16  when the environment in the lumen of separation membrane  16  has a partial pressure(s) of the gaseous species that is less than the partial pressure(s) of the target gaseous species in the liquidous fluid. In some embodiments, such an environment may be achieved by evacuating the lumen to a predetermined extent, in accordance with the well-understood principles of vacuum degassing. In one embodiment, liquidous fluid enters interior chamber  14  through fluid inlet port  50  along direction arrow  56 , and through distribution channel  58  in cell  30 . The flow of fluid between fluid inlet port  50  and fluid outlet port  52  results in fluid contact with separation membrane  16  along length “L” of cell  30 . As will be described in greater detail hereinbelow, the arrangement of separation membrane  16  between cell  30  and housing  12  facilitates an enhanced degassing efficiency, to an extent that liquidous fluid flow rates exceeding 20 ml/min through fluid inlet port  50  may be sufficiently degassed by the time it exits interior chamber  14  at fluid outlet port  52 . 
     Separation membrane tubing  16 A,  16 B may be helically wound about cell  30 , in a space between cell  30  and housing  12 . Preferably, separation membrane  16  may be disposed between an outer surface  31  of cell  30  and an inner surface  13  of housing  12 , which may be defined as gap  60 . In other embodiments, gap  60  comprises the space between substantially opposing surfaces in interior chamber  14 , in which separation membrane  16  is disposed. An aspect of the present invention is the control of the dimensions of gap  60 , and particularly the spacing dimensions between outer surface  31  of cell  30  and separation membrane  16  (first spacing  66 ), as well as between inner surface  13  of housing  12  and separation membrane  16  (second spacing  68 ). Applicant has discovered that control of gap  60  and such separation spacing can dramatically improve degassing proficiency in a flow-through degassing module. 
     To assist in correctly positioning tubular separation membrane  16  in gap  60 , one or more cell struts  62  may extend from outer surface  31  of cell  30  to support and/or maintain tubular separation membrane  16  in a spaced relationship from outer surface  31 , and one or more housing struts  64  may extend from inner surface  13  of housing  12  to support and/or maintain at least a predetermined second spacing  68  between inner surface  13  and tubular separation membrane  16 . The one or more cell struts may support tubular separation membrane  16  in spaced relationship from outer surface  31  of cell  30  to define first spacing  66 , while housing struts  64  may act to maintain a spacing between inner surface  13  of housing  12  and separation membrane  16 , as second spacing  68 . In some embodiments, cell struts  62  are connected to cell  30  and extend from outer surface  31  by one or more dimensions that are substantially equivalent to first spacing  66 . In some embodiments, housing struts  64  may be connected to housing  12 , and extend from inner surface  13  by a dimension that is substantially equivalent to second spacing  68 . 
     To enhance degassing efficiency, gas transport resistance should be reduced. In membrane vacuum degassing applications, transport resistance is primarily derived from the liquid phase and the membrane. To reduce the liquid phase transport resistance, gap  60  (the solvent depth) is reduced. However, a smaller gap  60  increases the flow resistance of the mobile phase through interior chamber  14 , and may also cause difficulties in manufacturability. Thus, a balance is preferably struck among the efforts of reducing the size of gap  60 , while maintaining sufficient first and second spacings  66 ,  68  to limit the corresponding increase in pressure drop in the mobile phase flow through interior chamber  14 . Other configurational details may be employed to help reduce the liquid phase resistance, such as through local mixing in the liquid phase. 
     To calculate the pressure drop along interior chamber  14 , we use the Darcy-Weisbach equation: 
     
       
         
           
             
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               p 
             
             = 
             
               
                 f 
                 D 
               
               × 
               
                 L 
                 D 
               
               × 
               
                 
                   ρ 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     V 
                     2 
                   
                 
                 2 
               
             
           
         
       
     
     Where Δp=pressure drop due to friction
         L=length of interior chamber  14     D=hydraulic diameter of interior chamber  14     ρ=density of the fluid   V=mean velocity of the flow F D =Darcy friction factor       

     Considering the annulus formation of the flow pattern (D=D 1 −D 2 =2 l) (D 1  is the larger cylinder ID, D2 is the smaller cylinder OD, and l is the gap), the pressure drop is 
               Δ   ⁢           ⁢   p     =         f   D     ×     L     2   ⁢   l       ×       ρ   ⁢           ⁢     Q   2         2   ⁢         π   2     ⁡     (       D   2     +   l     )       2     ⁢     l   2           ≈         f   D     ⁢   ρ   ⁢           ⁢     Q   2     ⁢   L       4   ⁢         π   2     ⁡     (     D   2     )       2     ⁢     l   3                 
For laminar flow, which most of the flow is under,
 
                 f   D     =       64   Re     =       32   ⁢           ⁢   v   ⁢           ⁢   π   ⁢           ⁢     D   2       Q         ,         
and the pressure drop becomes:
 
               Δ   ⁢           ⁢   p     ≈       8   ⁢   μ   ⁢           ⁢   QL       π   ⁢           ⁢     D   2     ⁢     l   3               
The pressure drop is therefore inversely proportional to the third power of the gap  60 . Applicant has determined that an appropriate dimension for gap  60  may be derived from first and second spacings  66 ,  68 , as the radial spacing between separation membrane  16  and each of outer surface  31  of cell  30  and inner surface  13  of housing  12 . First and second spacings  66 ,  68  may be controlled by respective height dimensions  63 ,  65  of cell and housing struts  62 ,  64 . Applicant has determined that strut height  63  for cell struts  62  may be between 2-20 mils (5-500 micrometers). Likewise, strut height  65  for housing struts  64  may be between 2-20 mils (50-500 micrometers). While strut heights  63 ,  65  may not be precisely equal to respective first and second spacings  66 ,  68 , the presence and dimensions of cell struts and housing struts  62 ,  64  provide for preferred radial dimensions for first and second spacings  66 ,  68  to achieve a balance between reduction in gas transport resistance, and an increase in pressure drop through interior chamber  14 . First and second spacings  66 ,  68  therefore have a radial dimension of at least about 5 mils, and preferably between about 2-20 mils (50-500 micrometers).
 
     It is to be understood that gap  60  may be defined as a channel or other flow region within which tubular separation membrane  16  is disposed in interior chamber  14 . Specifically, gap  16  is not limited to being defined between outer surface  31  of cell  30  and inner surface  13  of housing  12 . It is contemplated that other structures may be present within interior chamber  14  to define a flow channel for contacting tubular separation membrane  16  with the fluid. 
     Cell struts  62  and housing struts  64  are examples of various structure that is effective in maintaining first and second spacing  66 ,  68  between tubular separation membrane  16  and its radially adjacent structures. Such radial spacing provides fluid flow channels both radially inwardly and radially outwardly of tubular separation membrane  16 . The existence of such flow channels acts to reduce the liquid phase transport resistance of gas to the separation membrane, and the calibrated spacing dimensions maximize such effect within useful pressure drop parameters. 
     Cell struts  62  and housing struts  64 , in some embodiments, may form axially-aligned groups to define axially-oriented flow channels  70 ,  72 , which applicant has determined to aid in mass transport properties of degassing module  10 . That is, groups of cell struts  62  may be axially aligned with one another, and/or groups of housing struts  64  may be axially aligned with one another. Thus, cell struts  62  and housing struts  64  act both to define flow channels for the mobile phase through interior chamber  14 , and to maintain desired first and second spacings  66 ,  68  radially from tubular separation membrane  16 . 
     In some embodiments, tubular separation membrane  16  may be helically wound within interior chamber  14 . In the embodiment illustrated in  FIG. 1A , tubular separation membrane  16  extends continuously between first and second evacuation ports  40 ,  42  and is helically wound in an abutting configuration, wherein the wound tubing coil is in a side-by-side axially abutting relationship along length “L”. Other winding patterns and arrangements for tubular separation membrane  16  are contemplated in the present invention, with example alternative arrangements being illustrated in other drawings in this case. 
     Another example embodiment is illustrated in  FIGS. 2-7 , wherein degassing module  110  includes a housing  112  having a housing shell  118  and a housing cap  120 . In this embodiment, housing cap  120  includes first and second evacuation ports  140 ,  142  that are configured to receive coupling units  144 , and a fluid inlet port and a fluid outlet port  150 ,  152  that are configured to receive fluid coupling units  154 . Tubular separation membrane  116  is helically wound about cell  130 , and particularly about cell struts  162  extending radially outwardly from cell  130 .  FIG. 4  is an isolation view of cell  130  extending axially from housing cap  120 . Cell struts  162  extend substantially axially and substantially in parallel to each other about a circumference at outer surface  131  of cell  130 . Applicant has determined that a plurality of cell struts  162  assist in maintaining a desired first spacing  166  of, for example, 50-500 micrometers. Accordingly, cell struts  162  may be circumferentially spaced apart by a circumferential spacing  180  that is proportional to first spacing  166 , a circumference of cell  130 , and the physical properties of separation membrane  116 . 
       FIG. 5  is a cross-sectional isolation view of housing  112 , illustrating housing struts  164  extending radially inwardly from housing shell  118 . Housing struts  164 , in this embodiment, extend substantially in parallel, and substantially axially along housing shell  118  to provide for a second spacing  168  between tubular separation membrane  116  and housing shell  118 . Similarly to cell struts  162 , Applicant has determined that a plurality of housing struts  164  assist in maintaining a desired second spacing  168 . The circumferential spacing  182  of housing struts  164  about housing shell  118  may be defined similarly to circumferential spacing  180  of cell struts  162 . 
       FIG. 6  illustrates a transparent end view of degassing module  110 , with separation membrane  116  disposed in interior chamber  114  between cell struts  162  and housing struts  164 .  FIG. 7  represents a similar transparent view with the helically wound tubular separation membrane  118  being removed. The illustration of  FIG. 7  reveals that, in some embodiments, housing struts  164  may be circumferentially offset from cell struts  162  to best retain separation membrane  116  at a position within gap  160  that properly maintains the desired first and second spacings  166 ,  168 . Other arrangements and relative arrangements regarding cell struts  162  and housing struts  164 , however, are contemplated as being useful in degassing modules of the present invention. 
       FIGS. 8-13  are cross-sectional schematic illustrations of alternative embodiments of degassing modules of the present invention. Degassing module  210  includes a fluid inlet port  250  and a fluid outlet port  252  in housing shell  218 , and a first evacuation port  240  in housing cap  220 . Fluid inlet port  250  permits conveyance of fluid through fluid coupling unit  254  along direction arrow  256  through cell channel  233  of cell  230 , which distributes the fluid into interior chamber  214  for contact with helically wound tubular separation member  216 . In this embodiment, a single separation membrane tube  216  may be helically wound about cell  230  and sealed at end  217 , so that a lumen of tubular membrane  216  may be sufficiently evacuated by communication with a vacuum source through evacuation port  240 . 
     Degassing module  310 , illustrated in  FIG. 9 , is similar to degassing module  210 , but with fluid inlet port  350 , fluid outlet port  352 , and first evacuation port  340  each being disposed in housing cap  320  of housing  312 . 
     Degassing module  410  illustrated in  FIG. 10  is similar to degassing module  10 , with the exception of two distinct tubular separation membranes  416  being helically wound in axially abutting relationship with respective closed ends  417 A,  417 B. 
     Degassing module  510 , illustrated in  FIG. 11 , depicts an optional arrangement of tubular separation membrane  516  that is helically wound, but not in axially abutting relationship. Instead, at least some coils are axially spaced apart to provide an axial spacing  519  between adjacent coils. Applicant has determined that, in some embodiments, such axial spacing  519  may further reduce transport resistance of the gaseous species to the membrane. The reduction in transport resistance is likely due to increased membrane surface area available to be contacted, as well as the mixing effects upon the fluid flow that result from an axially spaced apart coiling pattern of tubular separation membrane  516 . 
     A further example separation membrane coiling pattern arrangement is illustrated in  FIG. 12 , wherein separation member  616  may have coils that are both axially spaced apart and radially displaced relative to an adjacent coil. Such an arrangement may further aid in the reduction of transport resistance of the gaseous species out of the liquid phase. 
       FIG. 13  illustrates a further alternative embodiment degassing module  710  with a single separation membrane tube  716  having a sealed end  717 . 
     An example degassing system  802  of the present invention is illustrated in  FIG. 14 , and includes a liquidous fluid source  804  and a degassing module  810 . A pump  808  is provided for motivating liquidous fluid from liquidous fluid source  804  through a transfer conduit  806  that fluidically couples liquidous fluid source  804  to a fluid inlet  850  of degassing module  810 . Pump  808  preferably motivates the liquidous fluid from liquidous fluid source  804  through an interior chamber of degassing module  810 . Degassing system  802  preferably further includes a vacuum source  845  for evacuating a lumen of a tubular separation membrane within the interior chamber through an evacuation port  840  in degassing module  810 . Degassed liquidous fluid flows out from degassing module  810  through a fluid outlet port  852  to an operating system, such as a chromatographic column, a liquid analyzer, an ink delivery mechanism, or the like. The liquidous fluid is preferably pumped into contact with the tubular membrane within degassing module  810  at a flow rate exceeding 20 ml/minute. 
     The invention has been described herein in considerable detail in order to comply with the patent statutes, and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the invention as required. However, it is to be understood that various modifications can be accomplished without departing from the scope of the invention itself.