Patent Publication Number: US-11656010-B2

Title: Evaporator with feed tube flow distributors for random gravitation and acceleration fields

Description:
BACKGROUND 
     The subject matter disclosed herein relates generally to the field of evaporators, and specifically to an evaporator for terrestrial and microgravity environments. 
     Evaporators utilize latent heat of a fluid to absorb waste heat from a heat source. As such, in order to operate efficiently, an evaporating surface of an evaporator should be covered by a layer of a liquid phase of a working fluid as much as possible during operational conditions. 
     The liquid phase of a working fluid (i.e., liquid) tends to accumulate and move in the direction of gravity in a terrestrial environment. In a microgravity environment, liquid distribution is randomized and tends to move freely if undisturbed. Therefore, in each of these terrestrial and microgravity environment cases, it is often critical to replenish evaporating surfaces of evaporators with liquid. 
     BRIEF SUMMARY 
     According to one embodiment, an evaporator assembly is provided. The evaporator assembly includes an inlet header, an outlet header, and an evaporator body extending from the inlet header to the outlet header. The evaporator body defining a channel fluidly connected to the outlet header. The evaporator assembly further includes a feed tube including: an adapter fluidly connected to the inlet header and a perforated tube fluidly connected to the inlet header through the adapter. The perforated tube including a first end attached to the adapter, a second end opposite the first end, and a plurality of orifices fluidly connecting the perforated tube to the channel. The perforated tube extends within the channel. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the second end of the perforated tube is located in the outlet header. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the second end of the perforated tube is sealed off. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices extend circumferentially around the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices extend longitudinally along a selected length of the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the selected length is less than or equal to a length of the evaporator body. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices start proximate the adapter and terminate before the outlet header. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices extend helically around the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices are arranged circumferentially around the perforated tube at a plurality of locations longitudinally along a selected length of the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the channel includes grooves respectively delimited by first and second interior facing sidewalls of the evaporator body which form a base and an apex with an apex angle opposite the base and defined such that, for a fluid flow moving through the channel in a microgravity environment: a portion of the fluid flow in a liquid phase within a groove of the channel will move in the groove from the base to the apex, and a portion of the fluid flow in a vapor phase within a groove of the channel will move in the groove from the apex to the base. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the groove circumferentially arrayed to extend outwardly from an open central region where the perforated tube is located. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the apex angle is 2β and β is less than 90° minus a solid-liquid contact angle. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include a fluid pump fluidly connected to the inlet header. The fluid pump being configured to deliver a working fluid at a selected pressure to maintain the working fluid through an entirety of the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the adapter is configured to block working fluid from migrating from the channel into the inlet header. 
     According to another embodiment, a feed tube for an evaporator assembly is provided. The feed tube including an adapter and a perforated tube connected to the adapter. The perforated tube including a first end attached to the adapter, a second end opposite the first end, and a plurality of orifices. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the second end of the perforated tube is sealed off. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices extend circumferentially around the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices extend longitudinally along a selected length of the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices extend helically around the perforated tube. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include that the plurality of orifices are arranged circumferentially around the perforated tube at a plurality of locations longitudinally along a selected length of the perforated tube. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, that the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG.  1    is a perspective view of an evaporator assembly, in accordance with an embodiment of the present disclosure; 
         FIG.  2    is a cutaway view of the evaporator assembly, in accordance with an embodiment of the present disclosure; 
         FIG.  3    is an enlarged cutaway view of an inlet header of the evaporator assembly of  FIG.  2   , in accordance with an embodiment of the present disclosure; 
         FIG.  4    is an enlarged cutaway view of an outlet header of the evaporator assembly of  FIG.  2   , in accordance with an embodiment of the present disclosure; 
         FIG.  5    is an isometric view of a feed tube of the evaporator assembly, in accordance with an embodiment of the present disclosure; 
         FIG.  6    is an isometric view of a feed tube of the evaporator assembly, in accordance with an embodiment of the present disclosure; 
         FIG.  7    is a perspective view of a body and channels of the evaporator assembly of  FIG.  1   , in accordance with an embodiment of the present disclosure; 
         FIG.  8    is an axial view illustrating a configuration of grooves of the channels of  FIG.  7   , in accordance with an embodiment of the present disclosure; 
         FIG.  9    is an illustration of an operation of the groove channels of  FIG.  7    in a microgravity environment, in accordance with an embodiment of the present disclosure; and 
         FIG.  10    is an illustration of an operation of the groove channels of  FIG.  7    in a gravity field, in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Movement of a working fluid of an evaporator in a microgravity environment is mainly dictated by a surface tension of the working fluid, characteristics of a surface the working fluid is intended to be in contact with and external disturbances applied to the system. In a terrestrial environment, the working fluid will tend to pool and flow in the direction of gravity. In either case, in a properly designed groove, working fluid can be replenished into the groove and vapor can be expelled out of the groove at similar rates which is useful in the replenishment of working fluid on an evaporating surface of an evaporator. As such, as will be described below, a groove geometry in which working fluid can be replenished into the groove and vapor can be expelled out of the groove at similar rates in integrated into an evaporator design. The evaporator design, according to one or more embodiments, is therefore suitable for both terrestrial and microgravity environments. 
     Additionally for a long evaporator oriented against gravity or under an adverse acceleration load, the working fluid may not be able to wet the entire length of the evaporator, and thus the evaporator will not have the designed efficiency of the temperature uniformity. The embodiments disclose herein seek to correct this inefficiency by allowing the working fluid to wed the entire length of the evaporator using a perforated tube installed along the length of the evaporator. 
     Referring now to  FIG.  1   , an isometric view of an evaporator assembly  100  is illustrated, according to an embodiment of the present disclosure. The evaporator assembly  100  includes an inlet header  110 , an evaporator body  130 , and an outlet header  120 . The evaporator body  130  is interposed between the inlet header  110  and the outlet header  120  and extends from the inlet header  110  to the outlet header  120 . The evaporator body  130  is the evaporating element of the evaporator assembly  100 . A fluid pump  400  is fluidly connected to the inlet header at the inlet  111 . The pump  400  is configured to deliver a working fluid  200  to the evaporator assembly  100  at a selected pressure. The working fluid  200  enters the inlet header  110  at an inlet  111 . The working fluid  200  then flows from the inlet header  110  to the outlet header  120  through the evaporator body  101  in a flow direction  104 . The working fluid  200  absorbs heat  103  from a heat source while flowing through the evaporator body  130 . The fluid then exits the outlet header  120  through an outlet  121  at the outlet header  120 . 
     Referring now to  FIGS.  2 - 4   , with continued reference to  FIG.  1   , a cutaway view of the evaporator assembly  100  is illustrated, according to an embodiment of the present disclosure. The working fluid  200  is conveyed from the inlet header  110  to the evaporator body  130  through a feed tube  300 . It is understood that, although discussed herein in the singular tense, the evaporator assembly  100  may include multiple feed tubes  300 , as illustrated in  FIGS.  2 - 4   . The feed tube  300  is composed of an adapter  310  and a perforated tube  330 . The adapter  310  fluidly connects the feed tube  300  to the inlet header  110 . 
     The perforated tube  330  may be tubular in shape as illustrated in  FIGS.  2 - 4   . The perforated tube  330  includes a first end  332  and a second end  334  opposite the first end  332 . The perforated tube  330  extends within and through a channel  140  formed within the evaporator body  130 . The perforated tube  330  is fluidly connected to the adapter  310  at the first end  332  such that the working fluid  200  may flow from the inlet header  110  into the first end  332  of the perforated tube  330  through the adapter  310 . The first end  332  is attached to the adapter  310 . In an embodiment, the second end  334  of the perforated tube  330  is located in the outlet header  120 , as illustrated in  FIG.  4   . In an embodiment, the second end  334  is sealed off or closed, such that no working fluid  200  exits the perforated tube  330  at the second end  334 . 
     The perforated tube  330  extends within the evaporator body  130  through a channel  140  defined in the evaporator body  130 . The evaporator body  130  is formed to define channels  140  that may be arranged in a linear formation  141  across a width W of the evaporator body  130 . Each of the channels  140  can have a substantially same shape as the others. 
     The perforated tube  330  includes a plurality of orifices  336  along a selected length L 1  of the perforated tube  330 . The selected length L 1  may be less than an overall length of the perforated tube  330 . As illustrated in  FIGS.  2 - 4   , the selected length L 1  does not extend from the first end  332  to the second end  334  but rather the selected length L 1  is about equal to or less than a length L 2  of the evaporator body  130 . The plurality of orifices  336  start proximate the adapter  310  or right after the adapter  310  but terminate before the outlet header  130 . There are no orifices  336  located in a portion of the perforated tube  330  that is located in the outlet header  120 , as illustrated in  FIG.  4   . In other words, the orifices  336  stop or cease to exist once the perforated tube  330  enters the outlet header  120 . The orifices  336  fluidly connect the perforated tube  330  to the channel  140 . The orifices  336  are configured to provide the working fluid  200  to the channels  140  of the evaporator body  130 . The orifices  336  are configured to provide the working fluid  200  to the channels  140  in liquid form, where the heat  103  may transform at least a portion of the working fluid  200  to vapor form. The working fluid  200  then migrates from the channels  140  into the outlet header  120  at a channel outlet  146 . The channel outlet  146  fluidly connects the channel  140  to the outlet header  120 . The adapter  310  prevents or blocks the working fluid  200  from migrating from the channel  140  into the inlet header  110 . In other words, the adapter  310  fluidly separates the channel  140  and the inlet header  110 . 
     In order to ensure that the evaporator assembly  100  can operate as efficiently as possible under any gravitational or acceleration load from any direction, the evaporative surfaces within the channel  140  of the evaporator body  130  may be continuously supplied with the working fluid  200  in a liquid phase. 
     The pump  400  (see  FIG.  1   ) is configured to deliver the working fluid  200  into the inlet  111 , then to the inlet header  110 , then into the adapter  310 , and then into the perforated tube  330  at a selected pressure in a liquid form. The selected pressure is high enough to maintain working fluid  200  throughout an entirety of the perforated tube  330  at all times. In other words, the perforated tube  330  is always filled with working fluid  200  (i.e., completely filled). 
     Advantageously, since the perforated tube  330  is always filled with working fluid  200 , the gravitation and the acceleration loads of any magnitude from any direction will not have any significant effect to the fill condition of the perforated tube  330  as long as the pump  400  is capable of generating enough pressure head to overcome the total system pressure drop. 
     Referring now to  FIGS.  5  and  6   , different patterns of orifices  336  are illustrated, in accordance with an embodiment of the present disclosure. It is understood that while two patterns of orifices  336  are illustrated in  FIGS.  5  and  6   , the embodiments disclosed herein may be applicable to any pattern of orifices  336 . Some examples for other patterns may include but are not limited to a single row, multiple one-sided rows, partial areal coverage, or any other pattern conceivable by one of skill in the art. 
       FIG.  5    illustrates a plurality of orifices  336  arranged circumferentially C 1  around the perforated tube  330  at a plurality of locations  338  longitudinally L 3  along the selected length L 1  of the perforated tube  330 . In other words, at each location  338  there the orifices  366  arranged circumferentially C 1  around the perorated tube  330 . There may be any number of orifices  336  at each location  338 . In an embodiment, there may be six orifices  336  at each location  338 , but it is understood that the embodiments disclosed herein may be applicable to more or less than six orifices at each location  338 . The number of orifices  336  at each location may be equivalent to a number of grooves  142  (See  FIGS.  7 - 10   ) in each channel  140 . The orifices  336  may be aligned with each groove  142  such that working fluid  200  from the orifices  336  may be directed into the groove  142 . The number of orifices  336  may vary but there may be enough orifices  336  such that the working fluid  200  can cover the evaporative surfaces of the channel  140 . The orifices  336  are sized such that the flow of working fluid  200  is high enough to reach the evaporative surfaces of the channel  140 . The evaporative surfaces includes the grooves  142 . The orifices  336  may be intermittently spaced or regularly spaced circumferentially C 1  around the perforated tube  330  at each location  338 . The locations  338  may be intermittently spaced or regularly spaced (e.g., D 1  is the same between each location) longitudinally L 3  along the selected length L 1  of the perforated tube  330 . 
       FIG.  6    illustrates a plurality of orifices  336  arranged in helically H 1  around the perforated tube  330 . There may be one orifices  336  at each location  338  as the plurality of orifices  336  winds helically H 1  around the perforated tub  330 . In other words, the plurality of orifices  336  are arranged in a line that winds circumferentially C 1  around the perforated tube  330  while traversing longitudinally L 3  along the selected length L 1  of the perforated tube  330 . 
     Advantageously, the orifices  336  within the perforated tube  330  can be designed to have any pattern as long as the liquid stream of working fluid  200  emanating from the orifices  336  can cover the channel  140 , which is a heat input surface of the evaporator body  130 . 
     Referring now to  FIGS.  7  and  8   , with continued reference to  FIGS.  1 - 6   , grooves  142  formed within the channels  140  of the evaporator body  130  are illustrated, according to an embodiment of the present disclosure. The evaporator body  130  is formed to define channels  140  that may be arranged in a linear formation across a width W of the evaporator body  130 . Each of the channels  140  can have a substantially same shape as the others and includes grooves  142  that are circumferentially arrayed to extend radially outwardly from an open central region  143  where the perforated tube  330  is located. 
     Each of the grooves  142  has a same shape as the others and is immediately adjacent to neighboring grooves  142 . In addition, each of the grooves  142  is delimited by first and second interior facing sidewalls  144  of the evaporator body  130 . The first and second interior facing sidewalls  144  are tapered toward each other to form a base B and an apex A. The apex A is opposite the base B and has an apex angle 2β where β is less than 90° minus a solid-liquid contact angle. That is, the apex angle 2β is defined such that, for a fluid flow moving through one of the channels  140  in a microgravity environment where a portion of the fluid flow is in a liquid phase and another portion of the fluid flow is in a vapor phase, the portion of the fluid flow in the liquid phase within a particular groove  142  of the channel  140  will move in the particular groove  142  from the base B to the apex A and the portion of the fluid flow in the vapor phase within the particular groove  142  will move in the particular groove  142  from the apex A to the base B. 
     Referring now to  FIG.  9   , with continued reference to  FIGS.  1 - 8   , an operation of the channels  140  and the grooves  142  in a microgravity environment is illustrated, in accordance with an embodiment of the present disclosure. As shown in  FIG.  9   , in the microgravity environment, once liquid contacts the first and second interior facing sidewalls  144  of each of the grooves  142 , the liquid moves in the direction from the base B and to the apex A. After vaporization by exposure of the evaporator body  130  to heat  103 , the vapor is expelled from the apex A toward the base B and to the open central region  143  where the perforated tube  330  is located. 
     Referring now to  FIG.  10   , with continued reference to  FIGS.  1 - 9   , an operation of the channels  140  and the grooves  142  in a gravity field G 1  is illustrated, in accordance with an embodiment of the present disclosure. As shown in  FIG.  10   , the gravity field G 1  does not affect the distribution of the working fluid  200  to grooves  142  of the channels  140  because the working fluid  330  is pressurized and is directed out of the perforated tube  330  towards the grooves  142 . Therefore, more heat transfer may occur between the evaporator body  130  and the working fluid  330  because the working fluid  200  is not susceptible to the gravity field G 1 . 
     Technical effects and benefits of the features described herein include utilizing pressurized perforated tubes to more equally distribute a working fluid in liquid form across a heat transfer surface of an evaporator in both microgravity environments and terrestrial environments. 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.