Patent Publication Number: US-10330361-B2

Title: Passive liquid collecting device

Description:
BACKGROUND 
     This application relates to a passive liquid collecting device for separating and collecting liquid from a mixture of liquid and vapor. 
     In microgravity and zero gravity environments, fluids tend to distribute throughout the reservoir storing the fluid. Some of the fluid, such as liquid, will attach to a wall of the reservoir, and the rest of the fluid will float throughout a cavity defined by the reservoir. The distribution of fluids attached to the reservoir wall and floating in the cavity can raise challenges when drawing a liquid phase of the fluid from the reservoir. 
     Two phase chiller systems, sometimes called thermal control loops, frequently have accumulators which collect both liquid and vapor refrigerant. The two phase chiller systems may be damaged or operate less efficiently if they draw a mixture of liquid and vapor from the accumulator instead of drawing liquid. Specifically, delivery of vapor to a pump within a chiller system may cause pump cavitation. 
     In addition to chiller systems, vapor-liquid phase separation is used in the oil and gas industry, various chemical manufacturing and treatment processes, fuel management systems, and numerous other applications. For example, in many chemical manufacturing and treatment processes, liquid and vapor phases are separated and directed along different paths for further individual processing or treatment. 
     A known solution for separating liquid from vapor is a structure that operates through capillary material. The capillary material collects liquid, but not vapor. The capillary material can be arranged within a reservoir to gather dispersed liquid and channel it to a desired location. 
     Capillary materials function in large part by porosity. The use of the material requires certain design considerations to guide liquid to a specific location instead of simply collecting and retaining the liquid. One known approach to guide the liquid is to construct the capillary material such that pores decrease in size as they approach the desired collection location. Systems operating on this principle can be difficult to design and manufacture such that they work efficiently. 
     SUMMARY 
     A passive liquid collecting device includes a reservoir including a reservoir exit line and at least one rigid structure disposed within the reservoir configured to collect a liquid and direct the liquid to the reservoir exit line. A first porous capillary media is supported by the at least one rigid structure and a vapor-liquid separator in contact with at least one of the at least one rigid structure and the first porous capillary media. The vapor-liquid separator includes a guide member extending along a guide member axis having a guide inlet and a guide outlet connected by a spiral conduit. A second porous capillary media is located radially outward from the spiral conduit on an exterior surface of the guide member. A thermal control loop is also disclosed. 
     These and other features may be best understood from the following drawings and specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically represents a thermal control loop. 
         FIG. 2A  illustrates an accumulator. 
         FIG. 2B  is a cross-sectional view of the accumulator along plane  2 B of  FIG. 2A . 
         FIG. 2C  is a cross-sectional view of the accumulator along plane  2 C of  FIG. 2A . 
         FIG. 3  illustrates a rigid structure suspending porous capillary media. 
         FIG. 4A  is an enlarged view of a rigid structure. 
         FIG. 4B  is an enlarged view of a pocket in the rigid structure. 
         FIG. 4C  is an enlarged view of a corner groove in the rigid structure. 
         FIG. 5  is a schematic depiction in a perspective view of an example embodiment of a vapor-liquid separator. 
         FIG. 6  is a perspective cross-section view of the vapor-liquid separator along plane  6  of  FIG. 5 . 
         FIG. 7  is an enlarged view of an inlet to the vapor-liquid separator of  FIG. 6 . 
         FIG. 8  is an enlarged view of a mid-portion of the vapor-liquid separator of  FIG. 6 . 
         FIG. 9  is a cross-sectional view of a schematic representation of a multilayer porous capillary media. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic representation of a thermal control loop  10 , which may also be referred to as a two phase chiller system. The thermal control loop  10  circulates a refrigerant to remove heat from objects or systems adjacent the thermal control loop  10 . In the illustrated embodiment, the thermal control loop  10  is driven by a pump  14 , but it should be understood that thermal control loops  10  operating without a pump  14  may also benefit from this disclosure. In the illustrated non-limiting embodiment, the operating capacity of the pump  14  is adjusted by a controller  46  that monitors conditions around the thermal control loop  10 . The refrigerant in the thermal control loop  10  cools one or more heat sources  18 . In one embodiment, the heat sources  18  are electrical components in a spacecraft  19  that may sometimes operate in a microgravity or zero gravity environment. 
     The heat sources  18  are cooled with evaporators  22 . The evaporators  22  cool the heat sources  18  by evaporating liquid refrigerant. In evaporators  22  the refrigerant undergoes a phase change from a liquid to a vapor. Some heat from the vapor may be communicated to liquid refrigerant earlier in the loop through a recuperator or preheater  26 . The preheater  26  exchanges heat from refrigerant in vapor form exiting the evaporators  22  to refrigerant in liquid form upstream of the evaporators  22 . The preheater  26  contributes to efficient operation of the thermal control loop  10  by bringing the liquid refrigerant close to an evaporating temperature before it reaches the evaporators  22 . The refrigerant in vapor form that exited the evaporators  22  is converted back into liquid by a condenser  30  downstream from the evaporators  22 . In one embodiment, the condenser  30  comprises a heat exchanger  34  and a radiator  38  which, respectively, take heat from the refrigerant in vapor form and convey the heat out of the thermal control loop  10 . 
     During steady state operation of the thermal control loop  10 , refrigerant in liquid form will exit the condenser  30 . During transient conditions when a thermal load on the evaporators  22  is increasing, such as caused by a sudden increase in a temperature of the heat sources  18 , more refrigerant in vaporous form will remain in vaporous form after passing through the condenser  30 . The increase in refrigerant in vaporous form downstream of the condenser  30  occurs until a new steady state condition is reached in the thermal control loop  10 . The new steady state is reached by the controller  46  monitoring the temperature and pressure of an accumulator  42  and the preheater  26  and adjusting a flow of the refrigerant through the thermal control loop  10  with the pump  14 . 
     In the illustrated embodiment, the thermal control loop  10  includes the accumulator  42  downstream of the condenser  30  for separating liquid refrigerant from vaporous refrigerant that passed through the condenser  30  without condensing into liquid form. After passing through the condenser  30 , the refrigerant enters the accumulator  42  through a refrigerant inlet passage  11 . As detailed below, the accumulator  42  collects refrigerant in liquid form to exit through a refrigerant outlet passage  12 . Most of the refrigerant that exits through the refrigerant outlet passage  12 , as measured by mass flow rate, is in liquid form. 
     The thermal control loop  10  also incorporates a recirculation line  16  to accommodate for transient conditions. The recirculation line  16  is fed from a portion of the thermal control loop  10  downstream from the pump  14  and upstream of pre-heater  26  and the evaporator  22 . The recirculation line  16  includes a recirculation valve  17  in communication with the controller  46  to maintain internal pressure of the accumulator  42  within acceptable bounds in response to conditions detected within the thermal control loop  10 , or to ensure that the accumulator continues to deliver an uninterrupted flow of liquid refrigerant regardless of changing load and transient conditions introduced into the thermal control loop  10 . An acceptable pressure and flow of refrigerant is achieved by controlling a volume of pumped liquid refrigerant that the recirculation line  16  returns to the accumulator  42 . 
     The thermal control loop  10  may contain a filter  50  in the refrigerant outlet passage  12  as well for maintaining quality of the liquid refrigerant. The filter  50  is downstream of the accumulator  42  and upstream of the pump  14 . 
       FIG. 2A  depicts the accumulator  42 . A volume of the accumulator  42  is defined by walls of a reservoir  54 . Although the end of the accumulator  42  is shown open, a cap (not shown) could cover the accumulator  42 . Within the reservoir  54  are a group of rigid structures  56  arranged circumferentially around a liquid collection tube  60 . During operation of the thermal control loop  10 , liquid may flow continuously from the liquid collection tube  60 , which is made of a porous material, through the refrigerant outlet passage  12 . The porous material of the liquid collection tube  60  contributes to a flow of liquid in the reservoir  54 . In one embodiment, the rigid structures  56  are constructed from a material chosen to not be reactive with the refrigerant used in the thermal control loop  10 . 
     The reservoir  54  shown in this embodiment has a cylindrical shape, with an axial component extending along a reservoir axis X, and a radial component R extending outward from the reservoir axis X. The group of rigid structures  56  in this embodiment is arranged to also define a roughly cylindrical shape. The rigid structures  56  extends along at least a majority of a length of the reservoir  54  along the reservoir axis X. Each rigid structure  56  also has legs  63  extending from a point where the rigid structure  56  contacts the liquid collection tube  60  to an outermost rib  62 . In the illustrated embodiment, the legs  63  extend along a radial direction and extends across at least a majority of a radius of a circular section of the reservoir  54 . Because of the axial and radial extension of the rigid structures  56 , the cylindrical shape defined by the group of rigid structures  56  in this embodiment extends throughout a significant portion of the reservoir  54 . A porous capillary media  64  is wrapped around the rigid structure  56 . 
     It should be understood that, although the reservoir  54  and arrangement of the rigid structures  56  shown in this embodiment are both cylindrical, the reservoir  54  and arrangement of the rigid structures  56  could be of any shape suitable for facilitating liquid travel toward the liquid collection tube  60  without departing from the scope of this disclosure. As an example, the reservoir  54  and the volume defined by the extremities of the rigid structures  56  could define a shape that is rectangular in section. 
     A cross-sectional view taken along plane  2 B of  FIG. 2A  is shown in  FIG. 2B . The refrigerant inlet passage  11  and refrigerant outlet passage  12  are connected to a reservoir entry line  111  and reservoir exit line  121 , respectively, within the reservoir  54 . The reservoir entry line  111  in the illustrated embodiment is connected to a vapor-liquid separator  110 , which contributes to the separation of vapor and liquids and will be discussed further below and the reservoir exit line  121  is in communication with the liquid collection tube. 
     The recirculation line  16  is also connected to the liquid collection tube  60  by a recirculation delivery line  161  within the reservoir  54 . The recirculation delivery line  161  accommodates for transient conditions in the thermal control loop  10  when a pressure within the reservoir  54  changes and the amount of refrigerant needed traveling through the thermal control loop  10  is changing. Specifically the recirculation delivery line  161  maintains liquid in the liquid collection tube  60  regardless of system conditions. The recirculation delivery line  161  is connected to the liquid collection tube  60  at an opposite end from the reservoir exit line  121 . 
     In addition to the reservoir entry line  111 , reservoir exit line  121 , and recirculation delivery line  161 , the accumulator  42  according to this embodiment has a test port  144 . The test port  144  is used to monitor and regulate pressure inside the reservoir  54 . To accomplish the monitoring and regulation, the test port may be fitted with apparatus such as a pressure monitoring device and/or pressure relief valve. The test port  144  can also be used to pressurize the accumulator  42  during startup of the thermal control loop  10 . 
       FIG. 2C  is a cross-sectional view of the accumulator  42  taken along plane  2 C of  FIG. 2A . Flow paths for example droplets or particles P of liquid refrigerant show how liquid refrigerant may flow from a radially outer area of the reservoir  54  to the liquid collection tube  60 . The rigid structures  56  have features which will be discussed further below that facilitate liquid movement across the legs  63 . The legs  63 , ribs  58 ,  59 ,  74 ,  62 , and porous capillary media  64  cooperate to cause liquid to disperse across the rigid structures  56 . However, because of flow from the liquid collection tube  60  and liquid collecting features such as corner grooves  72  of the rigid structures  56  near the liquid collection tube  60  that will be detailed below, overall liquid travel will generally go from radially outer portions of the rigid structures  56  to radially inner portions of the rigid structures  56 . 
     As shown, particles P of liquid refrigerant floating in the reservoir  54  may contact the rigid structure  56 . If the particle P contacts the rigid structure, it will disperse across the legs  63  or ribs  58 ,  59 ,  74   62 . If the particle P contacts porous capillary media  64 , it will disperse throughout the porous capillary media  64 . In either case, dispersion of liquid across the rigid structures  56  or porous capillary media  64  will eventually cause the liquid refrigerant to be collected in the corner grooves  72 , which are in fluid communication with the liquid collection tube  60 . Because the porous capillary media  64  wrap around the rigid structures  56 , parts of the porous capillary media  64  are disposed between the rigid structures  56  and the liquid collection tube  60 , putting them in direct contact with the liquid collection tube  60 . Because of the direct contact between the porous capillary media  64  and the liquid collection tube  60 , liquid refrigerant may also be communicated to the liquid collection tube  60  directly through the porous capillary media  64 . 
     Particles P that contact the rigid structure  56  or porous capillary media  64  between the legs  63  will flow towards a leg  63 . Once at the legs  63 , the liquid moves radially inwardly along the legs  63  to the liquid collection tube  60 . 
     The vapor-liquid separator  110  is situated near, or attached to, the rigid structures  56  to further facilitate efficient travel of liquid to the liquid collection tube  60 . The proximity of the vapor-liquid separator  110  to the rigid structures  56  puts another porous capillary media  122 , such as a liquid coalescing medium, on an exterior surface of the vapor-liquid separator  110  into contact with the porous capillary media  64 , providing an efficient flow path for liquid refrigerant through the reservoir  54  that will be further detailed below. In the illustrated non-limiting embodiment, the vapor-liquid separator  110  is located between an adjacent pair of rigid structures  56  such that the vapor-liquid separator  110  is in contact with the adjacent pair of rigid structures  56  and the adjacent pair of rigid structures  56  are spaced from each other. 
     As shown in  FIGS. 2C, 3, and 4A , the rigid structures  56  are pie shaped in that they have a generally triangular shape except for one arcuate side. The pie shape defines an inner corner  61 . The rigid structures  56  include the legs  63  that extend in a radial direction and ribs  58 ,  59 ,  74 ,  62  that extend in a circumferential direction between adjacent legs  63 . There are innermost ribs  58 , inner middle ribs  59 , outer middle ribs  74 , and outermost ribs  62 . Wrapped around at least a portion of each of the rigid structures  56  is porous capillary media  64  constructed from porous media. Because the porous capillary media  64  is wrapped around portions of rigid structures  56 , a shape of the porous capillary media  64  is defined by a shape of the rigid structures  56 . In the embodiment shown, the porous capillary media  64  are supported in a group of pie shapes because of the pie shaped rigid structures  56 . 
     In one embodiment, the porous capillary media  64  is formed of multilayer screen mesh, felt, sintered metallic powder, or ceramic. Material for the porous capillary media  64  may be chosen to not be reactive with the refrigerant. 
     The legs  63  are connected by arms extending in the axial direction. There is an innermost arm  65   a , inner middle arms  65   b , outer middle arms  65   c , and outermost arms  65   d . In the embodiment shown, the porous capillary media  64  is wrapped around the innermost arm  65   a  and the outer middle arms  65   c . Thus, porous capillary media  64  enclose the inner middle arms  65   b , but not the outermost arms  65   d . In another embodiment, the porous capillary media are wrapped around the inner middle arms  65   b  and innermost arm  65   a  only. Because there is a single innermost arm  65   a  forming a point, the porous capillary media  64  will have a portion near the liquid collection tube  60  with an angle equal to an angle of the inner corner  61 . 
     Faces of the ribs  58 ,  59 ,  74 ,  62 , legs  63 , and arms  65  of the rigid structure  56  in connection with the porous capillary media  64  form an absorbent system spanning an interior of the reservoir  54 . A drop of liquid anywhere in the reservoir  54  should be close to one of the ribs  58 ,  59 ,  74 ,  62 , legs  63 , arms  65 , or porous capillary media  64 . Thus, liquid floating in the reservoir  54  will likely come into contact with the rigid structure  56  or the porous capillary media  64  without any outside excitation. 
     Because the porous capillary media  64  is wrapped on the rigid structure  56 , the porous capillary media  64  can maintain a desired shape even if it is flexible or lacks rigidity. The rigid structures  56  provide support for the porous capillary media  64 . 
     One consideration in designing an arrangement of the rigid structures  56  is a contact angle of the liquid refrigerant and an angle of the inner corner  61  of the rigid structures  56  defined by the legs  63 . The rigid structure  56  will collect refrigerant if the sum of the liquid refrigerant&#39;s contact angle plus half of the angle defined by the inner corner is less than 90°. For example, if the refrigerant is water, and the contact angle of water is 70°, the rigid structure  56  will collect liquid refrigerant if the angle A of the inner corner  61  is less than 40°. Angle A is defined by an extension of the legs  63 . Liquids with smaller contact angles would attach to rigid structures  56  a greater angle at the inner corner  61 . Thus, the reservoir  54  could be formed with relatively fewer rigid structures  56 . In the illustrated embodiment, the angle of the inner corner  61  is 36°. 
     A contact angle of a liquid varies depending on the surface the liquid is in contact with. Contact angles between many common liquids and surfaces are readily available in technical literature and would be known to a skilled person. Where angles between particular liquids and surfaces are not known or documented in readily available resources, they may be measured by known methods. 
       FIG. 4A  is an enlarged view of a portion of the rigid structure  56  with the porous capillary media  64  removed. Pocket  70  ladders on edges of the legs  63  collect liquid and facilitate fluid movement in a radial direction. The pockets  70  on the left hand side legs  63  are shown cut in half. 
     An exemplary pocket  70  is depicted in a further enlarged view in  FIG. 4B . The pockets  70  are shaped to facilitate fluid movement radially inwardly along legs  63 . The pockets  70  are wider at an end  70   e  spaced away from their relatively narrow openings  70   o . In the disclosed example, they have a trapezoidal cross-sectional shape. Further, angles  71  are acute to collect refrigerant. The pockets  70  hold a greater quantity of liquid, and with a greater force, than a flat surface with square edges would. Because the pockets  70  are near each other, liquid will climb from overflowing pockets  70  to adjacent, relatively empty pockets  70  through porous capillary media  64 . This is shown schematically at F. In this way, the pockets  70  move liquid radially along the rigid structures  56  even in the presence of adverse external forces, such as gravity. 
     Corner grooves  72 , side grooves  76 , holes  80 , and holes  84 , shown in another enlarged view in  FIG. 4C  facilitate fluid movement toward the liquid collection tube  60 . The side grooves  76  are in fluid communication with the corner grooves  72  through holes  80 . Each corner groove  72  feeds into a hole  84  that is aligned with a trough  85  of the corner groove  72 . The holes  84  communicate liquid collected in the corner grooves  72  to the porous tube of the liquid collection tube  60 . 
     Angles  73  defined by the corner grooves  72  and angles  77  defined by the side grooves  76  affect the grooves&#39;  72 ,  76  efficacy in collecting refrigerant in a liquid state in the same manner as described above with respect to the angle A at the inner corner  61  and the rigid structures  56 . To collect refrigerant in a liquid state, the grooves  72 ,  76  may have acute angles and be constructed such that the sum of a liquid refrigerant contact angle, plus half of the angle  73 ,  77  defined by the grooves  72 ,  76  is less than 90°. Phrased another way, if half of either angle  73  or  77  is subtracted from 90°, the difference may be greater than the contact angle of the liquid refrigerant. For example, if the liquid refrigerant is water with a contact angle of 70°, the difference between 90° and the contact angle of the refrigerant is 20°. If the difference is 20°, the angles  73 ,  77  should each be less than 40°, because 20° is half of 40°. In one embodiment, the angles  73 ,  77  are 36°. 
     The rigid structures  56  and porous capillary media  64  work together to create a flow of liquid to the liquid collection tube  60 . As liquid near the liquid collection tube  60  is drawn into the liquid collection tube  60 , and out of the reservoir  54 , the continuous flow will drive liquid collected elsewhere on the rigid structure  56  toward the liquid collection tube  60 . The flow of liquid from the liquid collection tube  60  is accomplished without requiring any external power to excite the liquid. 
     The above described structure will result in the great bulk of refrigerant leaving the reservoir  54  refrigerant outlet passage  12  to be refrigerant in a liquid form, but other apparatus could facilitate more efficient collection of liquid by the accumulator. For example, as shown in  FIG. 2B , the mixture of liquid and vaporous refrigerant could enter the accumulator  42  through a vapor-liquid separator  110  that uses momentum of a flowing mixture to separate vapor from liquid. 
       FIGS. 5-8  schematically depict the details of a non-limiting embodiment of the vapor-liquid separator  110 .  FIG. 5  shows an exterior surface of a vapor-liquid separator  110 , having a plurality of radial channels  120  and the porous capillary media  122 .  FIG. 6  is a cross-sectional view taken along plane  6  of  FIG. 5 . As shown in  FIG. 6 , a fluid mixture  112  comprising a vapor and a liquid from the condenser  30  enters a guide inlet  119  of a guide member  114 . The fluid mixture  112  then passes through the guide member  114  to produce a relatively liquid-depleted mixture  124  at a guide outlet  128  of the guide member  114 , shown in  FIG. 5 . 
     The plurality of radial channels  120  extend radially through the exterior surface of the guide member  114  such that an interior space, such as an elongated spiral conduit  118  ( FIG. 6 ) within the guide member  114  is in fluid communication with the porous capillary media  122  disposed on the exterior surface of the guide member  114 . In the illustrated non-limiting embodiment, the radial channels  120  are in a spiral arrangement on the guide member  114  and follow the spiral of the spiral conduit  118  ( FIG. 6 ). The guide member  114  according to the illustrated embodiment also has axial grooves  126  facilitating dispersal of liquid along the exterior surface of the guide member  114 . 
     The length of the spiral conduit  118 , the number and configuration of the radial channels  120 , and the configuration of the porous capillary media  122  can be specified according to design parameters to produce the desired degree of vapor and liquid depletion in the fluids exiting the vapor-liquid separator  110  at anticipated operating conditions. 
       FIG. 6  is a cross-sectional view taken along plane  6  of  FIG. 5 . As shown in the illustrated embodiment, a path between the guide inlet  119  for the fluid mixture  112  and the guide outlet  128  for liquid-depleted mixture  124  generally extends along a guide member axis  116 . In the illustrated embodiment, the guide member axis  116  extends longitudinally through a center of the vapor-liquid separator  110 . 
     An interior structure  117  of the guide member  114  is disposed along the guide member axis  116  and defines a spiral conduit  118  within the guide member  114 . The spiral shape of the spiral conduit  118  is disposed along the guide member axis  116 , and aligns with the spiral arrangement of the radial channels  120 . In the illustrated non-limiting embodiment, the interior structure  117  only defines a single spiral conduit  118 . However, in another embodiment, the vapor-liquid separator  110  could include more than one spiral conduit  118  offset from each other defined by the interior structure  117  within the guide member  114 . 
     The spiral conduit  118  imparts a centrifugal momentum to the flowing fluid mixture  112  to separate the liquid component from the vapor in the fluid mixture  112  in microgravity or zero gravity environments. Because a liquid phase of most substances will have greater mass density than the vapor phase, the liquid will generally have more momentum than the vapor. Accordingly, the greater momentum of the liquid flowing through the spiral conduit  118  will tend to force the liquid to gather toward the radially outer side of the spiral conduit  118  and travel through the radial channels  120  and come into contact with the porous capillary media  122 . Conversely, the portion of the fluid mixture  112  that is relatively vapor-rich and fluid-depleted will remain near the radially inner side of the spiral conduit  118  and will become the relatively liquid-depleted mixture  124  leaving the guide outlet  128  of the vapor-liquid separator  110 . 
     The vapor-liquid separator  110  contributes to more efficient collection of liquid by the accumulator  42  when employed to process the refrigerant entering the reservoir  54 . The vapor-liquid separator  110  described herein can be utilized in a variety of environments and applications. The vapor-liquid separator  110  can be disposed in a microgravity environment, where it can in some embodiments provide phase separation without moving parts and without assistance from gravity. Further, the vapor-liquid separator  110  would have utility in a two-phase heat transfer system. 
       FIG. 7  is an enlarged view of  FIG. 6  showing the fluid mixture  112  entering the vapor-liquid separator  110 . Guide vanes  115  at the inlet to the spiral conduit  118  deflect the fluid mixture  112  from the relatively linear path at the guide inlet  119  to a rotating path or spiral path into the spiral conduit  118 . The guide vanes  115  introduce a rotating vector smoothly, creating less turbulence and pressure drop than would result from sending a linear flow of the fluid mixture  112  directly into the spiral conduit  118 . In another embodiment, the guide vanes  115  could be eliminated and the fluid mixture  112  could enter the vapor-liquid separator  110  in a direction perpendicular or transverse to the guide member axis  116  to induce rotation into the fluid mixture  112  and encourage the fluid mixture  112  to follow the spiral conduit  118 . 
       FIG. 8  is an enlarged view of the interior structure  117  from  FIG. 6 . As shown, the radial channels  120  open into the spiral conduit  118 . Further, the spiral conduit  118  is tapered such that it is narrower at its radially outward side adjacent the radial channels  120 . If the spiral conduit  118  tapers enough, it could create a liquid wicking corner according to principles discussed above regarding the angles  73 ,  77  of various features of the rigid structures  56 . The surfaces of the spiral conduit  118  may be composed of or coated with a material wettable by the liquid in the fluid mixture  112 . The centrifugal force, tapered shape, and wettable surface of the spiral conduit  118  all contribute to efficient collection of liquid from the fluid mixture  112  at the radially outer side of the fluid conduit  118  and, as a result, communication of the liquid from the spiral conduit  118  through the radial channels  120  to the porous capillary media  122  on the exterior of the vapor-liquid separator  110 . 
     A wide variety of options for structure and composition of the porous capillary media  122  is contemplated herein. The porous capillary media  122  can be selected from any of a wide variety of porous media, including but not limited to mesh screens or pads made of various materials such as metal or plastic, woven or non-woven fiber pads, open-cell foams made of various materials such as metal, plastic, or composite materials. The dimensions of the porous capillary media  122  can vary depending on the specific properties of the liquid (e.g., density, surface tension properties, etc.) and the vapor, and on process design parameters including but not limited to mass flow rates and flow velocities. In some embodiments, the dimensions or materials of the porous capillary media  122  can vary radially relative to the guide member axis  116 . For instance, the porous capillary media  122  can have larger openings (e.g., coarser mesh) relatively closer to the guide member axis  116  and smaller openings (e.g., finer mesh) relatively farther from the guide member axis  116 . 
     As depicted in  FIG. 9 , the porous capillary media  122  includes a first screen mesh layer  123 , and a second screen mesh layer  125  radially outward from the first screen mesh layer and having a finer mesh size than the first screen mesh layer. In the illustrated embodiment, the porous capillary media  122  also includes a third screen mesh layer  127  disposed between the first and second screen mesh layers  123 ,  125 . The third screen mesh layer  127  includes a finer mesh size than the first screen mesh layer  123  and a courser mesh size than the second screen mesh layer  125 . The first, second, and third screen mesh layers  123 ,  125 , and  127  can have any mesh sizes suitable for a given application, but in one exemplary embodiment the first screen mesh layer  123  has a mesh size of 20 μm to 50 μm, the second screen mesh layer  125  has a mesh size of 1 μm to 5 μm, and the third screen mesh layer  127  has a mesh size of 5 μm to 20 μm. Any of the above described radial variations could also be applied axially relative the guide member axis  116  to accommodate different conditions as the fluid mixture  112  flows along the spiral conduit  118 . 
     During operation of the thermal control loop  10 , a mixture of liquid and vapor forming the fluid mixture  112  can exit the condenser  30  and enter the accumulator  42 . Because vaporous refrigerant can damage the pump  14 , the accumulator  42  is utilized to separate the vapor from the liquid and provide a liquid refrigerant to the pump  14 . The fluid mixture  112  will initially pass through the vapor-liquid separator  110  in the accumulator  42  which will direct the fluid mixture  112  through the spiral conduit  118 . A liquid portion of the fluid mixture  112  will flow out of the spiral conduit  118  through the radial channels  120  and the liquid-depleted mixture  124  will exit the vapor-liquid separator  110  through the guide outlet  128 . The liquid-depleted mixture  124  collects in the reservoir  54 . The vapor-depleted or mostly liquid phase of the fluid mixture  112  in the axial grooves  126  and the radial channels  120  disposed on the outer surface of the vapor-liquid separator  110  is collected by the porous capillary media  122 . The liquid-depleted mixture  124  collected by the reservoir  54 , will be further processed by the rigid structures  56  and/or porous capillary media  64  as discussed above. 
     The liquid in the porous capillary media  122  will transfer to the rigid structures  56  because of the proximity of the porous capillary media  122  to the rigid structures  56  and the porous capillary media  64  located on the rigid structures  56 . In one embodiment, the porous capillary media  64  includes a finer mesh size than mesh size of the porous capillary media  122 , causing liquid within the porous capillary media  122  to travel to the porous capillary media  64  due to capillary forces. From the rigid structures  56 , the liquid travels to the liquid collection tube  60  and out the reservoir exit line  121  towards the pump  14 . 
     Additionally liquid refrigerant enters the accumulator  42  through the recirculation delivery line  161 , which is in communication with the recirculation line  16 . The recirculation delivery line  161  allows liquid refrigerant to pass through the liquid collection tube  60  with at least a portion of the liquid leaving the accumulator  42  through the reservoir exit line  121  depending on the transient needs of the thermal control loop  10 . 
     Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.