Patent Publication Number: US-9895669-B2

Title: Interaction chamber with flow inlet optimization

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit as a continuation application of U.S. patent application Ser. No. 13/085,939, filed Apr. 13, 2011, entitled “Interaction Chamber with Flow Inlet Optimization”, the entire disclosure of which is hereby incorporated by reference herein. Any disclaimer that may have occurred during the prosecution of the above-referenced application is hereby expressly rescinded, and reconsideration of all relevant art is respectfully requested. This application also expressly incorporates by reference, and makes a part hereof, U.S. patent application Ser. No. 12/986,477, entitled “Low Holdup Volume Chamber”, and U.S. patent application Ser. No. 13/085,903, entitled “Compact Interaction Chamber with Multiple Cross Micro Impinging Jets”, filed on behalf of the same inventors. 
    
    
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the photocopy reproduction of the patent document or the patent disclosure in exactly the form it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND OF THE INVENTION 
     For certain pharmaceutical applications, manufacturers need to process and mix expensive liquid drugs for testing and production using the lowest possible volume of fluid to save money. Current mixing devices operate by pumping the fluid to be mixed under high pressure through an assembly that includes two mixing chamber elements secured within a housing. Each of the mixing chamber elements provides fluid paths through which the fluid travels prior to being mixed together. The fluid paths at the discharge end of each of the mixing chamber elements mix with one another under high pressure, resulting in the high energy dissipation. As the fluid is more efficiently pumped through the fluid paths, the amount of energy dissipated and the thoroughness of the mixing of the fluid in the mixing chamber increases. Due to the geometry of the fluid paths, current mixing chambers have increased flow resistance and therefore decreased exit fluid flow rates. As a result, these mixing chambers require higher energy and pressure at the input of the mixing chamber to overcome the flow inefficiencies and achieve acceptable mixing conditions. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a cross-sectional view of an example assembled interaction chamber taken along line X-X of  FIG. 2 , according to one example embodiment of the present invention. 
         FIG. 2  is a top view of the assembled example interaction chamber according to one example embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of the first housing of the example interaction chamber taken along line X-X of  FIG. 2  according to one example embodiment of the present invention. 
         FIG. 4  is a cross-sectional view of the second housing of the example interaction chamber taken along line X-X of  FIG. 2  according to one example embodiment of the present invention. 
         FIG. 5  is a cross-sectional view of the retaining element of the example interaction chamber taken along line X-X of  FIG. 2  according to one example embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of a prior art mixing device. 
         FIG. 7  is a perspective cross-sectional view of an inlet mixing chamber element of a prior art device. 
         FIG. 8  is a perspective cross-sectional view of an outlet mixing chamber element of a prior art device. 
         FIG. 9  is a side cross-sectional view of the inlet and outlet mixing chamber elements of the prior art device taken along line IX-IX of  FIGS. 7 and 8 . 
         FIG. 10  is a perspective cross-sectional view of an inlet mixing chamber element according to one example embodiment of the present invention. 
         FIG. 11  is a perspective cross-sectional view of an outlet mixing chamber element according to one example embodiment of the present invention. 
         FIG. 12  is a side cross-sectional view of the inlet and outlet mixing chamber elements taken along line XII-XII of  FIGS. 10 and 11  according to one example embodiment of the present invention. 
         FIG. 13  is a chart plotting pressure and flowrate of one example embodiment of the present invention. 
         FIG. 14  is a chart plotting pressure and fluid averaged velocity of one example embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is generally directed to an interaction chamber that includes mixing chamber elements with curved flow inlets to reduce flow resistance and increase discharge fluid flow rate. The curved flow inlets result in the superior mixture of fluid using less energy than current mixing devices. By decreasing the flow resistance in the curved inlet of the mixing chamber elements, the fluid flow rate entering the mixing chamber elements can be increased as well, resulting in significant energy savings without sacrificing quality and consistency of the mixing. 
     The curved inlets are part of an interaction chamber, as described in U.S. patent application Ser. No. 12/986,477, which is incorporated herein by reference. Also incorporated herein by reference is U.S. patent application Ser. No. 13/085,903 directed to a mixing chamber with an impinging micro fluid flow path configuration. It should be appreciated, however, that the curved inlets of the present disclosure described in greater detail below can be implemented into any suitable mixing device, and are not limited to the interaction chamber illustrated or discussed in U.S. application Ser. No. 12/986,477 or the interaction chamber illustrated and discussed in U.S. patent application Ser. No. 13/085,903. 
     The interaction chamber of the present disclosure includes, among other components: a first housing; a second housing; an inlet retaining member; an outlet retaining member; an inlet mixing chamber element; and an outlet mixing chamber element. When assembled, the inlet retaining member and the outlet retaining member are situated facing one another within a first opening of the first housing. The inlet and outlet mixing chamber elements reside adjacent one another and between the inlet and outlet retaining members within the first opening. The second housing is fastened to the first housing such that a male protrusion on the second housing is inserted into the first opening making contact with the second retaining member. When the first and second housings are fastened together, the first retaining member and second retaining member are forced toward one another, thereby compressing the inlet and outlet retaining members and properly aligning the inlet and outlet mixing chamber elements together. The mixing chamber elements are further secured for high pressure mixing by the hoop stress exerted on the inlet and outlet mixing chamber elements by the inner wall of the first opening, as will be explained in further detail below. 
     As discussed below, in the interaction chamber of the present disclosure, the mixing chamber elements are secured using both compression from the torque of fastening two housings together as well as hoop stress of the inner walls of the first housing directed radially inwardly on the mixing chamber elements. However, rather than using a tube member that would need to be stretched to hold the mixing chamber elements radially, the first housing is heated prior to insertion of the mixing chamber elements, and allowed to cool and contract once the mixing chamber elements are inserted and aligned. By securing the mixing chamber elements with the hoop stress of the first housing applied as a result of thermal expansion and contraction, the torque required to compress the mixing chamber elements together is significantly reduced. Therefore, the interaction chamber can be reduced in size, number of components, and complexity that results in a significant reduction in holdup volume. 
     Referring now to  FIGS. 1 to 5 and 10 to 12 , various example embodiments of the interaction chamber are illustrated.  FIG. 2  illustrates a cross-sectional view of the assembled interaction chamber assembly  100  taken along the line X-X of the top view shown in  FIG. 2 .  FIG. 3  illustrates the first housing  102  in detail,  FIG. 4  illustrates the second housing  104  in detail and  FIG. 5  illustrates the inlet/outlet retainer  108 / 110  in detail.  FIG. 10  illustrates the inlet mixing chamber element  112  in detail and  FIG. 11  illustrates the outlet mixing chamber element  114  in detail.  FIG. 12  illustrates a cross-sectional side view of the inlet mixing chamber element  112  and the outlet mixing chamber element  114  assembled together. 
     As seen in  FIG. 1 , the assembled interaction chamber  100  may include a generally cylindrically shaped first housing  102  and a generally cylindrically shaped second housing  104 . The first housing  102  is configured to be operably fastened to the second housing  104  using any sufficient fastening technology. In the illustrated example embodiment, the first housing  102  is fastened to the second housing  104  with a plurality of bolts  106  arranged in a circular array around a central axis A. It should be appreciated that the generally cylindrically shaped first housing  102  and the generally cylindrically shaped second housing  104  share central axis A when assembled. 
     Between the first housing  102  and the second housing  104  resides an inlet retainer  108 , an outlet retainer  110 , an inlet mixing chamber element  112  and outlet mixing chamber element  114 . The inlet retainer  108  is arranged adjacent to the inlet mixing chamber element  112 . The inlet mixing chamber element  112  is arranged adjacent to the outlet mixing chamber element  114 , which is arranged adjacent to the outlet retainer  110 . When the interaction chamber  100  is assembled, bolts  106  clamp the first housing  102  to the second housing  104 , thereby compressing the inlet mixing chamber element  112  and outlet mixing chamber element  114  between the inlet retainer  108  and the outlet retainer  110 . 
     After assembly, an unmixed fluid flow is directed into inlet  116  of the first housing  102 , and through an opening  118  in inlet retainer  108 . As discussed in more detail below, the unmixed fluid flow is then directed through a plurality of small pathways in the inlet mixing chamber element  102  in the direction of the fluid path. The fluid then flows in a direction parallel to the face of the inlet mixing chamber element  112  and the face of the adjacent outlet mixing chamber element  114  through a plurality of microchannels formed between the inlet mixing chamber element  112  and the outlet mixing chamber element  114 . The fluid is mixed when the plurality of micro channels converge. The mixed fluid is directed through a plurality of small pathways in the outlet mixing chamber element  114 , through an opening  120  in outlet retainer  110 , and through outlet  122  of the second housing  104 . 
     It should be appreciated that the plurality of bolts  106  used to fasten the first housing  102  to the second housing  104  provide a clamping force sufficient to compress the inlet mixing chamber element  112  and the outlet mixing chamber element  114  so that the microchannels formed between the two faces are fluid tight. However, due to the high pressure and the high energy dissipation resulting from the mixing taking place between the inlet mixing chamber element  112  and the outlet mixing chamber element  114 , the compression force applied by the torqued bolts  106  alone may not be sufficient to hold the mixing chamber elements static within the first opening of the first housing  102  during mixing. Thus, in addition to the compressive force applied by the bolts  106 , the mixing chamber elements  112 ,  114  are held circumferentially by the inner wall  117  of the first opening  115  of the first housing  102 , which applies a large amount of hoop stress directed radially inwardly on the mixing chamber elements, as will be further discussed below. This secondary point of retention and security reduces the required amount of compressive force to hold the mixing chamber elements in place during high pressure and high energy mixing and prevents the mixing chamber elements cracking at high pressures. 
     For example, due to the hoop stress applied to the mixing chamber elements, each of six bolts  106  in one embodiment need only a torque force of 100 inch-pounds to hold the mixing chamber elements together to create a seal. Prior art devices that use primarily compression to secure the mixing chamber elements as discussed above, however, tend to require significantly higher amounts of torque force to hold the mixing chamber elements together to create a seal (about 130 foot-pounds of torque). Because the prior art devices use a tube member that must be stretched to decrease its diameter and clamp down on the mixing chamber elements, the prior art devices require larger housings, more components and therefore, a higher hold-up volume of approximately 0.5 ml. In one embodiment of the present disclosure, the mixing chamber elements are secured within the first opening of the first housing and achieve the high hoop stress imparted from the inner wall of the first housing onto the outer circumference of the mixing chamber elements, the present disclosure takes advantage of precision fit components and the properties of thermal expansion. The hold-up volume of the interaction chamber of the present disclosure is around 0.05 ml. 
     An example procedure for assembling one embodiment of the interaction chamber of the present disclosure are now described with reference to the assembled interaction chamber in  FIG. 1  and each individual component illustrated in  FIGS. 3 to 5 and 10 to 12 . 
     First, the inlet retaining member  108 , as shown in  FIG. 6 , may be inserted into the first opening of the first housing, as shown in  FIG. 3 . The inlet retaining member  108  has a substantially cylindrical shape, and fits concentrically within the first opening of the first housing. When inserted, the inlet retaining member  108  includes a chamfered surface  130  that is configured contact a complimentary chamfered interior surface  119  of the first housing  102 . This chamfered mating between the first housing  102  and the inlet retaining member  108  ensures that the inlet retaining member  108  self-centers within the first opening and lines up properly and squarely to the inner wall  117  of the first opening  115 . It should be appreciated that the inlet retaining member  108  includes a concentric passageway  132  which allows fluid to flow through the inlet retaining member  108 . The passageway  132  lines up with flow path  116  of the first housing  102 , through which the unmixed fluid is pumped from a separate component in the mixing system. 
     Second, the first housing  102  may be heated to at least a predetermined temperature, at which point the first opening  115  expands from a first opening diameter to at least a first opening expanded diameter. In some example embodiments, the first housing is made of stainless steel, and the first housing is heated using a hot plate or any other suitable method of heating stainless steel. In one such embodiment, the predetermined temperature at which the first housing is heated is between 100° C. and 130° C. It should be appreciated that, when the first opening  115  is at the first diameter, the mixing chamber elements  112 ,  114  are unable to fit within the first opening  115 . However, the mixing chamber components  112 ,  114  are manufactured and toleranced such that, after the first housing  102  is heated and the first diameter expands to the first expanded diameter, the mixing chamber elements  112 ,  114  are able to fit within the first opening  115 . In one embodiment, the first expanded diameter is between 0.0001 and 0.0002 inches larger than the first diameter. 
     Third, the inlet mixing chamber element  112  is inserted into the first opening  115  of the heated first housing  102 . The top surface  304  of the inlet mixing chamber element  112  is configured to be in contact with the bottom surface  132  of inlet retaining member  108 . Because the inlet retaining member  108  is self-aligned with the chamfered mating surfaces of  119  and  130 , the inlet mixing chamber element  112  is also properly aligned when surface  304  makes complete contact with surface  132  of inlet retaining member  108 . 
     Fourth, the outlet mixing chamber element  114  is inserted into the first opening  115  of the heated first housing  102 . The top surface  310  of the outlet mixing chamber element  114  is configured to be in contact with the bottom surface  306  of the inlet mixing chamber element  112 . It should be appreciated that in some embodiments, the surface  306  and surface  310  include complimentary features that ensure the inlet mixing chamber element  112  is properly oriented and aligned with the outlet mixing chamber element  114 . For example, in one embodiment, the inlet mixing chamber element  112  includes one or more protrusions that fit one or more complimentary recesses in the outlet mixing chamber element  114  so as to ensure proper rotational alignment of the two mixing chamber elements. 
     Fifth, once the mixing chamber elements  112 ,  114  are arranged within the first opening  115  of the heated first housing  102 , the outlet retaining member  110  may be inserted into the first opening  115 . The outlet retaining member  110  is substantially similar in structure to the inlet retaining member  108 . Similar to the inlet retaining member  108 , surface  132  of the outlet retaining member  110  is configured to make contact with surface  312  of the outlet mixing chamber element  114 . 
     Sixth, the second housing  104  is aligned with the first housing  102  and the assembled first and second housings are operatively fastened together. As seen in  FIG. 3 , the second housing  104  includes protrusion  125  extending from top surface  126 . When the first housing  102  is aligned with the second housing  104 , protrusion  125  fits into the first opening  115 . Similar to the opposite end of the first opening  115 , the protrusion  125  includes a complimentary chamfered surface  123 , which is configured to contact the chamfered surface  130  of the outlet retaining member  110 . Also similar to the first housing&#39;s contact with the inlet retaining member  108 , the chamfered surface  123  of protrusion  125  ensures that the outlet retaining member  110  is square to the inner surface  117  of opening  115 . When both the inlet retaining member  108  and the outlet retaining member  110  are properly aligned by the first housing  102  and the protrusion  125  of the second housing  104  respectively, the inlet mixing chamber element  112  and the outlet mixing chamber element  114  are correctly aligned within the first opening  115 . If the mixing chamber elements  112 ,  114  are even slightly misaligned, the elements may be damaged due to incorrect holding forces and the high pressure of the mixing. Additionally, the mixing results will be less consistent and reliable if the mixing chamber elements are not perfectly aligned by the retaining members and the first and second housings. 
     Seventh, the first housing may be operatively fastened to the second housing so that the inlet retainer, the inlet mixing chamber element, the outlet mixing chamber element, the outlet retainer, and the male member of the second housing are in compression. In the illustrated embodiment, six bolts  106  may be used to fasten the first housing  102  to the second housing  104 . To ensure equal clamping force between the first housing  102  and the second housing  104 , the bolts  106  are spaced sixty degrees apart and equidistant from central axis A. As discussed above, the fastening of six bolts  106  provides sufficient clamping force to seal surface  306  of the inlet mixing chamber element with surface  310  of the outlet mixing chamber element. It will be appreciated that any appropriate fastening arrangement or numbers of bolts may be used. 
     Eighth, the first housing is allowed to cool down from its heated state. In various embodiments, the first housing is cooled down by allowing it to return to room temperature or actively causing it to cool with an appropriate cooling agent. When the first housing is cooled, the material of the first housing contracts back, and the first housing expanded diameter is urged to contract back to the first housing diameter. Because the mixing chamber elements are already arranged and aligned inside of the first opening of the first housing, the contracting diameter of the first opening exerts a high amount of force directed radially inwardly on the mixing chamber elements. This force, in combination with the compressive force applied from the six bolts  106 , is sufficient to hold the mixing chamber elements in place for the high pressure mixing. It should be appreciated that the mixing chamber elements can be made of any suitable material to withstand the radially inward stress of 30,000 pounds per square inch applied when the first opening diameter contracts. In one embodiment, the mixing chamber elements are constructed with 99.8% alumina. In another embodiment, the mixing chamber elements are constructed with polycrystalline diamond. 
     In operation, when the inlet mixing chamber element  112  and the outlet mixing chamber element  114  are secured and held in the first housing between the inlet and outlet retaining members, surface  306  makes a fluid-tight seal with surface  310 . The unmixed fluid is pumped through flow path  116  of the first housing  102 , and through inlet retainer  108  to inlet mixing chamber element  112 . At inlet mixing chamber element  112 , the fluid is pumped at high pressure into ports  300  and  302 , and then into the plurality of microchannels  308 , described in more detail below. Due to the decrease in fluid port size from flow path  116  to ports  300 ,  302  to microchannels  308 , the pressure and shear forces on the unmixed fluid becomes very high by the time it reaches the microchannels  308 . As discussed above, and because of the secure holding between the inlet and outlet mixing chamber elements, microchannels  308  and  318  combine to form micro flow paths, through which the unmixed fluid travels. When the micro flow paths converge on one another, the high pressure fluid experiences a powerful reaction, and the constituent parts of the fluid are mixed as a result. After the fluid has mixed in the micro flow paths, the mixed fluid travels through outlet ports  314 ,  316  of outlet mixing chamber element  114 . 
     Referring now specifically to  FIGS. 6 to 9 , a prior art mixing chamber is illustrated and discussed. As seen in  FIG. 6 , a prior art mixing assembly is illustrated. The mixing assembly  200 , which includes an inlet cap  202  and an outlet cap  204 . The inlet cap  202  includes threads that are configured to engage complimentary threads on the outlet cap  204 . The mixing assembly  200  also includes an inlet flow coupler  220 , an outlet flow coupler  222 , an aligning tube  221 , an inlet retainer  224 , an outlet retainer  226 , an inlet mixing chamber element  228  and an outlet mixing chamber element  230 . 
     The inlet flow coupler  220  is arranged within the inlet cap  202 , and the outlet flow coupler  222  is arranged within the outlet flow cap  204 . When assembled, the tube  221  stays aligned with both the inlet flow coupler  220  and the outlet flow coupler  222  with the use of a plurality of pins  229 . The inlet retainer  224  and the outlet retainer  226  are arranged within the tube  221 , and serve to align and retain the inlet mixing chamber element  228  and the outlet mixing chamber element  230 . The inlet and outlet retainers  224  and  226  make contact with the inlet flow coupler  220  and the outlet flow coupler  222  respectively. 
     When the device is fully assembled, a flow path is formed between the inlet flow coupler  220 , the inlet retainer  224 , the inlet mixing chamber element  228 , the outlet mixing chamber element  230 , the outlet retainer  226  and the outlet flow coupler  222 . The unmixed fluid enters the inlet flow coupler  220  and travels through the inlet retainer  224  and to the inlet mixing chamber element  228 . Under high pressure and as a result of the high energy reaction, the unmixed fluid is mixed between the inlet mixing chamber element  228  and the outlet mixing chamber element  230 . The mixed fluid then travels through the outlet retainer  226  and the outlet flow coupler  222 . As will be described in greater detail below and illustrated in  FIGS. 7 to 9 , the pre-mix flow of the fluid follows a substantially right-angular flow path as it travels from the inlet of the ports downward and makes an approximately ninety degree turn toward the mixing chamber. 
     In  FIG. 7 , a prior art inlet mixing chamber element  228  corresponds to the inlet mixing chamber element  228  depicted in  FIG. 6 . The illustrated prior art inlet mixing chamber element  228  includes a top surface  404 , a bottom surface  412  and a plurality of ports  406 ,  408  extending from the top surface  404  toward the bottom surface  412 . On bottom surface  412  of the inlet mixing chamber element  228 , one or more microchannels  410  are etched. The ports  406 ,  408  are in fluid communication with microchannels  410 . 
     Similar to the prior art inlet mixing chamber element  228 , a prior art outlet mixing chamber element  230  illustrated in  FIG. 8  corresponds to the outlet mixing chamber element  230  depicted in  FIG. 6  and discussed briefly above. The prior art outlet mixing chamber element  230  includes top surface  414 , bottom surface  426  and a plurality of ports  422 ,  424  extending from top surface  414  to bottom surface  426 . On top surface  414 , one or more microchannels  418  are etched. The ports  422  and  424  are in fluid communication with the microchannels  416 . It should be appreciated that the microchannels  418  of the outlet mixing chamber element  230  and the microchannels  410  of the inlet mixing chamber element  228  complement one another such that, when the inlet mixing chamber element  228  and the outlet mixing chamber element  230  are pressed sealingly together in the mixing assembly, as shown in  FIG. 1 , microchannels  410  and  418  create fluid pathways. In the illustrated prior art embodiment, three fluid pathways are arranged on either side of the mixing chamber. Each fluid pathway has a complementary fluid pathway directly opposite the mixing chamber. 
     In one example of the assembled prior art device, the fluid is pumped under high pressure through the fluid pathway defined from the top surface  404  of the inlet mixing chamber element  228  through ports  406  and  408  to the microchannels formed by  410  on the inlet mixing chamber element  228  and microchannels  418  on the outlet mixing chamber element  430 . The fluid discharged from each of the fluid pathways flows under high pressure and high speed so that when it collides with fluid flowing from its complementary fluid path, the two fluid streams mix in the mixing chamber  401 . In the mixing chamber  401 , the fluid is broken down into small particles and mixed. The mixed fluid then exits the output mixing chamber element  230  through ports  422  and  424 . 
     Referring now to  FIG. 9 , a side cross-sectional view of the inlet mixing chamber element  228  and the outlet mixing chamber element  230  of a prior art device are illustrated. As more clearly illustrated in  FIG. 9 , the cross section of the microchannels  410  exiting from the ports  406  and  408  follow a right angular pathway. The fluid passes through port  406  and  408  of the inlet mixing chamber element  228  until it encounters the top of the outlet mixing chamber element  230 . When the fluid flow reaches the top of the outlet mixing chamber element, it is interrupted and is forced to flow through the microchannels  410 / 418  into the mixing chamber. In the prior art device, the microchannels  410 / 418  have a constant cross-sectional shape, and terminate at the outer radial end of port  406  and port  408  respectively. This prior art construction of the microchannels  410 / 418  creates a corner  430 ,  432  where the port meets the microchannels. The corner  430  is created between the base of port  406  and the top base of the microchannel  418  of outlet mixing chamber element  230 . The corner  432  is created between the base of port  408  and the top base of the microchannel  418  of outlet mixing chamber element  230 . 
     As illustrated in  FIGS. 7 to 9 , the prior art devices include a flow path that continues through the inlet ports  406 ,  408  and redirects the fluid to the outlet mixing chamber element  230  through an abrupt right angle turn into the microchannels  410 / 418  at corners  430 ,  432 . It should be appreciated that, when the fluid is pumped at high pressure into the right angle flow path inlets of the prior art device, flow resistance is increased as the particles get trapped and are unable to flow freely into the microchannels and the mixing chamber  401  when the flow path changes direction. As a result of increased flow path resistance, the corresponding discharge coefficient is reduced. As discussed above, when the fluid to be mixed is discharged at a higher rate, the particle size decreases upon impact in the mixing chamber, thereby resulting in a more efficient and consistent mixture. Therefore, it is advantageous to decrease the flow resistance of the mixing inlet configuration and increase the discharge coefficient. 
     Referring now to  FIGS. 10 to 12 , an example mixing chamber embodiment of the present invention is discussed and illustrated. In  FIG. 10 , the inlet mixing chamber element  112  includes a top surface  304 , configured to contact the inlet retaining element  108  when inserted into the first opening  115  of the first housing  102 . The inlet mixing chamber element  112  also includes a plurality of ports  300 ,  302  extending from surface  304  toward bottom surface  306 . Ports  300 ,  302  are small, and it should be appreciated that  FIGS. 10 to 12  have been drawn out of scale for illustrative and explanatory purposes. On bottom surface  306  of the inlet mixing chamber element  112 , a plurality of microchannels  308  are etched. The ports  300 ,  302  are in fluid communication with microchannels  308 . 
     In  FIG. 11 , the outlet mixing chamber element includes a top surface  310 , a bottom surface  311  and a plurality of ports  314 ,  315  extending from top surface  310  to bottom surface  311 . In one embodiment, a plurality of microchannels  312  are etched into top surface  310  of the outlet mixing chamber element  114 . The microchannels  312  are in fluid communication with outlet ports  314  and  315  through mixing chamber  301 . 
     In operation in one embodiment, the inlet mixing chamber element  112  and the outlet mixing chamber element  114  are abutted against one another under high pressure in the mixing assembly. In one embodiment, the microchannels  308  of the inlet mixing chamber element  112  and the microchannels  312  of the outlet mixing chamber element  114  complement one another to create fluid-tight micro flow paths when the mixing chamber elements  112 ,  114  are fully assembled. Microchannels  312  on surface  310  of the outlet mixing chamber element  114  are configured to line up with microchannels  308  on surface  306  of the inlet mixing chamber element  112  of  FIG. 10  when the two mixing chamber elements are aligned and sealingly abutted against one another. The micro flow paths created by microchannels  308  and  312  provide a fluid path leading from the top surface of the inlet mixing chamber element  112 , through the ports  300 ,  302 , through the micro flow paths, into the mixing chamber, and out the ports  314 ,  315  of the outlet mixing chamber element  114 . 
     As discussed generally above and illustrated in detail in  FIGS. 10 to 12 , the microchannels  308  and  312  are specifically constructed in the inlet mixing chamber element  112  and the outlet mixing chamber element  114  respectively to encourage a low-turbulence flow of the liquid from the ports  300 ,  302  toward the outlet mixing chamber element  314 . In  FIG. 12 , a side cross-sectional view of the inlet mixing chamber element  112  and the outlet mixing chamber element  114  of one example embodiment of the present invention are illustrated. In various embodiments, after the fluid is pumped into the ports  300 ,  302  of the inlet mixing chamber element, it travels downward toward the top surface  310  of the outlet mixing chamber element  114 . When the fluid flow encounters the outlet mixing chamber element  114 , it changes direction and is discharged out of the plurality of micro flow paths defined by microchannels  308  and  312  into mixing chamber  301 , where the fluid is mixed with the discharged fluid flow originating from the opposing micro flow path. 
     As seen in  FIG. 12 , one example embodiment of the present invention includes flow paths that do not follow a totally linear horizontal path from the ports  300 ,  302  to the mixing chamber  301 . In various embodiments, the microchannels are etched into the inlet mixing chamber element  112  to create a sweeping cross-sectional shape with a curved radius leading from the inlet port  300  to the mixing chamber  301 . In the inlet mixing chamber element  112 , the depths of the microchannels  308  etched on the bottom surface  306  are adjusted to create the curved cross section. In one embodiment, the etching is deeper on the bottom surface  306  at the outer radial portion where the microchannel meets the base of port  300 ,  302 , and gradually shallower toward the inner radial portion of the inlet mixing chamber element  112 . Correspondingly, on the outlet mixing chamber element  114 , the microchannels  312  etched onto the top surface  310  are adjusted to complement the microchannels  108  on the inlet mixing chamber element  112  to create curved micro flow paths when the two mixing chamber elements are sealingly abutted against one another. In one embodiment, the etching is shallower on the top on the top surface  310  at the outer radial portion of where ports  300  and  302  line up with outlet mixing chamber element  114 . The depth of the etching for the microchannels  312  of outlet mixing chamber element  114  gradually increases toward the inner radial portion of the outlet mixing chamber element  114 . In one embodiment of the present invention, the micro flow paths have a generally rectangular cross-section. In another embodiment, the micro flow paths have a generally round cross-section. 
     It should be appreciated that in various embodiments, when the inlet mixing chamber element  112  and the outlet mixing chamber element  114  are sealingly pressed together, the variable-depth microchannels in each of the bottom surface  306  and the top surface  310  create a micro fluid flow path that is curved. In one embodiment, the combination of the two mixing chamber elements  112 ,  114  results in fluid flow paths of substantially consistent cross-sectional shape, due to the precise microchannel variable depth control exercised in manufacture. The curved micro fluid flow path provides a route for fluid to be pumped from the ports  300 ,  302  to the mixing chamber  301  without encountering a sharp right angle turn, present in the prior art of  FIGS. 7 to 9 . As will be discussed in more detail below, the gradual introduction of the fluid from a first direction to a substantially second perpendicular direction advantageously results in significantly less flow resistance, and therefore a higher discharge rate of the fluid. 
     Referring now to  FIG. 12 , a cross-sectional view of an assembly showing  FIGS. 10 and 11  abutting against one another, along line XXII-XXII. The cross sectional view is taken along a line that bifurcates the mixing chamber elements  112  and  114  through the middle of the center microchannel  308 / 312 . In one embodiment illustrated in  FIG. 12 , the curved inlets leading from the base of ports  300  and  302  to the micro flow paths  308 / 312  has a flared shape. In various embodiments, this flared shape is shaped substantially similar to a horn, with a significantly wider opening than the dimensions of the micro flow path. 
     In one embodiment, as the fluid is pumped through the curved micro fluid flow paths, the flow rate can be calculated according to the formula Q=vwh, where Q is the flow rate, v is the velocity of the fluid in the micro fluid flow path, w is the width of the microchannel, and h is the height or depth of the microchannel. The velocity, v, is calculated according to the formula 
             v   =       C   d     ⁢         2   ⁢   Δ   ⁢           ⁢   P     ρ               
where C d  is the discharge coefficient, ΔP is the process pressure and ρ is the fluid density. As can be appreciated from the velocity formula, the closer that the discharge coefficient is to 1, the higher the velocity of the fluid exiting the micro fluid flow paths. Similarly, if the discharge coefficient is lower, to achieve a certain flow rate, the process pressure has to increase.
 
     It should be appreciated that, as evidenced by tests, an example prior art embodiment with right-angle micro fluid flow paths results in a discharge coefficient C d  of between 0.62 and 0.68. As a result of the inefficient flow path and the corners present where the ports  406 ,  408  meet the top surface  414  of the outlet mixing chamber element  230 , flow resistance is significant, and the fluid discharges at a lower velocity assuming constant process pressure and fluid density. 
     In contrast, as evidenced by tests, one example embodiment of the present invention with curved micro fluid flow paths results in a discharge coefficient C d  of between 0.76 and 0.83. Due to the curved micro fluid flow path inlets, the fluid to be mixed has a more efficient route from the ports  300 ,  304  to the mixing chamber  301 , and the interruption of an abrupt right angular change in direction present in the prior art is removed, thereby increasing the discharge coefficient. The increased discharge coefficient allows the mixing assembly to achieve higher levels of fluid velocity and fluid flow rate than the prior art under the same pressure. As discussed above, higher levels of fluid flow rate result in more efficient mixing and breakdown of the molecules into smaller particles. It should be appreciated that, in various example embodiments, the flow rate of the present invention is 20 to 50% higher than the flow rate of the prior art embodiment illustrated and described, with the same pressure and fluid density. 
     It should be appreciated that, by conserving energy as it flows in and maximizing the discharge coefficient and discharge velocity, the energy release is concentrated to the mixing chamber, rather than being wasted by resistance in the micro flow paths. As will be appreciated, when the energy and velocity is maximized in the mixing chamber, the mixture is optimized. Local turbulence in a confined micro flow path mixing chamber is promoted by increasing the micro flow path flow rates. Higher local turbulence brings about smaller length and time scales which means fast micro-mixing. For a set of fast precipitation reactions, if micro-mixing is very fast at which chemical reaction occurs, high local supersaturation of chemical reactive species is generated, which leads to a fast local nucleation rate and therefore small precipitate particle size with limited diffusional growth. 
     Besides achieving superior mixing, the shear rate of the fluid can also be maximized. In one embodiment, the shear rate is calculated according to the formula: 
               γ   =         2   ⁢   v     h     =       2   ⁢   Q         C   d     ⁢     wh   2             ,         
where v is the velocity of the fluid in the microchannel, h is the depth of the microchannel, Q is the flow rate, C d  is the discharge coefficient and w is the width of the microchannel. As described above, the discharge coefficient of micro fluid mixers is significantly affected by the cross-sectional geometry of the micro fluid flow path inlet leading from the inlet ports to the mixing chamber. An increased flow rate also increases the shear rate inside of the micro fluid flow paths, which helps to reduce the particle size of the fluid for a top-down approach because the shear rate makes the particle experience different velocities at different portions which deforms it and tears it apart.
 
     Referring now to  FIGS. 13 and 14 , two charts showing the comparison between present curved inlet embodiments and the prior art embodiments are disclosed and discussed. The graph of  FIG. 13  displays the results of a test in which the pressure of the fluid in pounds per square inch is plotted on the horizontal axis and the flow rate of the fluid in millimeters per minute is plotted on the vertical axis. The plotted curves each correspond to flow rates of two different fluid flow inlet geometries for pressures from 10,000 psi to 30,000 psi. The lower curve represents predicted flow rate data of a right-angle fluid flow inlet embodiment, and the upper curve represents measured flow rate data from the curved fluid flow inlet embodiment of the present disclosure. Given the slot size of the measured curved fluid flow inlet embodiment, the flowrate of a simulated right-angle fluid flow inlet embodiment with the same dimension flow paths can be easily calculated. It should be appreciated that the flow rates of the curved fluid flow inlets at given pressures are consistency higher than the predicted flow rates for right angle fluid flow inlets at the same corresponding pressures with the same cross-sectional sized fluid flow paths. 
     For example, see Tables 1 to 4 reproduced below, which include the data used to create the  FIG. 13  chart. As can be appreciated, the size of the slot with the right angle inlet in Table 1 is the same as the size of the slot with the curved inlet in Table 3. As seen in Table 2, the flow rate, shear rate and jet velocity (depicted in  FIG. 14  discussed below) for the right angle inlet are predicted for the pressures of 10,000 psi, 15,000 psi, 20,000 psi, 25,000 psi and 30,000 psi. Similarly, as seen in Table 4, the flow rate, shear rate and jet velocity for the curved angle inlet as measured in the test are shown for pressures of 10,000 psi, 15,000 psi, 20,000 psi, 25,000 psi and 30,000 psi.  FIG. 13  shows the improved performance of fluid flow rate between the curved fluid flow inlet embodiment and the prior art right angle fluid flow inlet embodiment.  FIG. 14  shows the improved performance of fluid averaged velocity in meters per second compared to pressure in pounds per square inch between the curved fluid flow inlet embodiment and the right-angle fluid flow inlet embodiment. As discussed above, due to the increased fluid flow efficiency of the disclosed curved inlet embodiment, the fluid can flow at a higher flow rate and velocity, thereby resulting in maximum energy released and optimum mixing. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Size of single-slot with right angle inlet 
               
            
           
           
               
               
               
            
               
                 Depth (μm) 
                 Width (μm) 
                 Area (μm 2 ) 
               
               
                   
               
               
                 94 
                 274 
                 25756 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Flow rate, shear rate and jet velocity 
               
               
                 of single-slot with right angle inlet 
               
            
           
           
               
               
               
               
            
               
                 Pressure (psi) 
                 Flow rate (ml/min) 
                 Shear rate (s −1 ) 
                 Jet velocity (m/s) 
               
               
                   
               
               
                 10000 
                 361 
                 4965525 
                 233 
               
               
                 15000 
                 446 
                 6134693 
                 288 
               
               
                 20000 
                 515 
                 7083782 
                 333 
               
               
                 25000 
                 577 
                 7936587 
                 373 
               
               
                 30000 
                 633 
                 8706863 
                 409 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Size of single-slot with curved inlet 
               
            
           
           
               
               
               
               
            
               
                 Depth (μm) 
                 Width (μm) 
                 Area (μm 2 ) 
                 Inlet radius (μm) 
               
               
                   
               
               
                 94 
                 274 
                 25756 
                 150 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Flow rate, shear rate and jet velocity 
               
               
                 of single-slot with curved inlet 
               
            
           
           
               
               
               
               
            
               
                 Pressure (psi) 
                 Flow rate (ml/min) 
                 Shear rate (s −1 ) 
                 Jet velocity (m/s) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 10000 
                 434 
                 5969634 
                 281 
               
               
                 15000 
                 539 
                 7413900 
                 348 
               
               
                 20000 
                 628 
                 8638088 
                 406 
               
               
                 25000 
                 701 
                 9642197 
                 453 
               
               
                 30000 
                 770 
                 10591286 
                 498 
               
               
                   
               
            
           
         
       
     
     It will be understood that the mixing chamber elements of the present disclosure succeed in reducing the flow resistance of fluid to be mixed by creating a curved micro fluid inlet from the ports of the inlet mixing chamber element to the mixing chamber. The reduced flow resistance results in a higher discharge coefficient and therefore higher fluid flow rates. In addition to higher fluid flow rates, the shear rate increases, which helps to reduce particle size and promote efficient mixing. These features improve the quality of mixing and also allow for lower pressures to achieve higher flow rates than the prior art mixing devices. In addition to saving cost and resources, the present disclosure performs consistently and reliably, and can advantageously be configured to operate with current machines needing no modification. In various embodiments, the microchannels  308 ,  312  are etched into the respective mixing chamber elements  112 ,  114  using laser micromachining. It should be appreciated that using laser micromachining ensures repeatability of manufacture and provides significant cost savings over alternative forms of manufacture. 
     In one example embodiment of the present disclosure, the mixing chamber assembly includes a first mixing chamber element and a second mixing chamber element sealingly aligned with the first mixing chamber element. The first and second mixing chamber elements are configured to accept a high pressure fluid flow along a flow path. The flow path extends in a first direction through a plurality of ports in the first mixing chamber element and then extends through a curved transitional portion of the first mixing chamber element from the plurality of ports to a plurality of micro fluid paths defined by the first and second mixing chamber elements. Following the curved transitional portion, the flow path leads through the plurality of micro fluid paths in a second direction from the curved transitional portion to the mixing chamber defined by the first and second mixing chamber elements, the second direction substantially perpendicular to the first direction. The flow path then extends into the mixing chamber through a second plurality of ports in the second mixing chamber element in the first direction. 
     In another example embodiment of the present disclosure, a method of mixing a fluid is disclosed. The method comprises pumping a fluid in a first direction through a plurality of inlet fluid ports defined in a mixing assembly into a plurality of micro fluid flow paths in a second substantially perpendicular direction. The micro fluid flow paths include a transition portion curved from the first direction of the inlet fluid ports to the second substantially perpendicular direction of the micro fluid paths. The method then includes discharging the fluid from the micro fluid flow paths into a mixing chamber and mixing the fluid in the mixing chamber. The fluid is mixed by directing paths of the discharged fluid to a specific location in the mixing chamber. The mixed fluid is then evacuated from the mixing assembly through a plurality of outlet ports in the first direction. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.