Patent Publication Number: US-2021164736-A1

Title: Fluid heat exchange systems

Description:
RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 60/954,987, filed on Aug. 9, 2007, pending U.S. patent application Ser. No. 12/189,476, filed on Aug. 11, 2008, and U.S. Provisional Patent Application No. 61/512,379, filed on Jul. 27, 2011, which applications are hereby incorporated by reference in their respective entireties, for all purposes. 
    
    
     BACKGROUND 
     The innovations and related subject matter disclosed herein (collectively referred to as the “disclosure”) generally pertain to fluid heat exchange systems. Some systems are described in relation to electronics cooling applications by way of example, though the disclosed innovations may be used in a variety of other applications. 
     Fluid heat exchangers are used to cool electronic and other devices by accepting and dissipating thermal energy therefrom. 
     Fluid heat exchangers seek to dissipate to a fluid passing there through, thermal energy communicated to them from a heat source. 
     Despite the existence of many previously proposed fluid heat exchange systems, there remains a need for heat exchange systems configured to provide improved thermal performance. As well, there remains a need for systems configured for existing and developing small form factors, and more particularly. For example, there remains a need for low-profile heat exchange assemblies (e.g., integrated heat sink and pump assemblies) having a vertical component height of about 27 mm, such as between about 24 mm to about 27.5 mm, or less. There also remains a need for integrated components and systems having fewer fluid connections. In addition, there is a need for low-pressure-loss flow transitions in integrated heat exchange components. 
     SUMMARY 
     The innovations disclosed herein overcome many problems in the prior art and address the aforementioned, as well as other, needs. The innovations disclosed herein pertain generally to fluid heat exchange systems and more particularly, but not exclusively, to approaches for integrating components in such systems. For example, some innovations are directed to low-profile pump housings. Other innovations are directed to heat sink designs that deliver improved heat-transfer and/or pressure-loss performance. And other innovations are directed to approaches for eliminating system components while retaining their respective functions. 
     In accordance with a broad aspect of the innovations disclosed herein, there is provided a fluid heat exchanger comprising: a heat spreader plate including an intended heat generating component contact region; a plurality of microchannels for directing heat transfer fluid over the heat spreader plate, the plurality of microchannels each having a first end and an opposite end and each of the plurality of microchannels extending substantially parallel with each other microchannel and each of the plurality of microchannels having a continuous channel flow path between their first end and their opposite end; a fluid inlet opening for the plurality of microchannels and positioned between the microchannel first and opposite ends, a first fluid outlet opening from the plurality of microchannels at each of the microchannel first ends; and an opposite fluid outlet opening from the plurality of microchannels at each of the microchannel opposite ends, the fluid inlet opening and the first and opposite fluid outlet openings providing that any flow of heat transfer fluid that passes into the plurality of microchannels, flows along the full length of each of the plurality of microchannels in two directions outwardly from the fluid inlet opening. 
     In accordance with another broad aspect of the disclosed innovations, there is provided a method for cooling a heat generating component comprising: providing a fluid heat exchanger including a heat spreader plate; a plurality of microchannels for directing heat transfer fluid over the heat spreader plate, the plurality of microchannels each having a first end and an opposite end and each of the plurality of microchannels having a continuous channel flow path between their first ends and their opposite ends; a fluid inlet opening for the plurality of microchannels and positioned between the microchannel first and opposite ends, a first fluid outlet opening from the plurality of microchannels at each of the microchannel first ends; and an opposite fluid outlet opening from the plurality of microchannels at each of the microchannel opposite ends; mounting the heat spreader plate onto the heat generating component creating a heat generating component contact region where the heat generating component contacts the heat spreader plate; introducing a flow of heat exchanging fluid to the fluid heat exchanger; urging the flow of heat exchanging fluid through the fluid inlet into the plurality of microchannels first to a microchannel region between the ends of the microchannel; and, diverting the flow of heat exchanging fluid into a plurality of subflows that each flow away from the other, a first of the plurality of subflows flowing from the fluid inlet toward the first fluid outlet and a second of the plurality of subflows flowing from the fluid inlet toward the opposite fluid outlet. 
     According to another broad aspect of the disclosed innovations, heat exchange systems are disclosed. 
     Some described heat exchange systems have a heat sink with a plurality of juxtaposed fins defining a corresponding plurality of microchannels between adjacent fins, and a recessed groove extending transversely relative to the fins. A manifold body at least partially defines an opening generally overlying the groove. 
     The manifold body and the groove can together define a portion of an inlet manifold. The inlet manifold can be configured to hydraulically couple in parallel each of the microchannels to at least one other of the microchannels. 
     The heat sink can have a heat spreader, with each of the fins extending from the heat spreader. The fins and the heat spreader can form a unitary construction, in some heat sink embodiments. Each of the fins can define a corresponding distal edge spaced from the heat spreader, and the groove can be recessed from the respective plurality of distal edges. In some heat sink embodiments, a lowermost extent of the recessed groove is spaced from the heat spreader. In other heat sink embodiments, a lowermost extent of the recessed groove is substantially coextensive with the heat spreader. As described below, each of the respective distal edges can define a corresponding recessed portion, thereby defining the recessed groove. 
     In some embodiments, the recessed groove comprises a first groove positioned adjacent a first end of the fins and a second groove positioned adjacent a second, opposing end of the fins. For example, the first groove and the second groove can define respective portions of an exhaust manifold. 
     The cross-sectional profile of the recessed groove can have any of a variety of shapes. For example, in some heat sink embodiments, a cross-sectional profile of the recessed groove comprises a selected one or more of the group consisting of a v-shaped notch, a semi-circle, a parabola, a hyperbola, and a notch having at least one substantially straight edge. 
     In some heat sink embodiments, a ratio of a representative height of the plurality of fins to a representative depth of the groove is between about 10:1 and about 10:7. For example, the ratio of the representative height to the representative depth can be between about 3:1 and about 2:1. 
     The opening in the manifold body can have a recessed region and an aperture extending through the manifold body from the recessed region. In some instances, the recessed region in the manifold body is a tapered recessed region having at least one cross-sectional dimension that diminishes with increasing depth of the recessed region. A slope of the recessed groove adjacent the manifold body can be substantially continuous with a slope of the recessed region in the manifold body adjacent the groove. The recessed region, the aperture and the groove can together define a flow transition having a characteristic length scale between about 150% and about 200% greater than a corresponding characteristic length scale of the aperture. 
     In some heat exchange systems of the type described herein, the inlet manifold can be configured to deliver a flow of a fluid to each of the microchannels in a transverse direction relative to a longitudinal axis of the respective microchannels. Some heat exchange systems have q body defining an inlet plenum. The inlet plenum and the inlet manifold can together be configured to deliver a fluid flow to in a direction generally transverse to the fins. For example, the inlet manifold can be configured to deliver an impingement flow of the fluid to each of the microchannels. 
     In some heat sink embodiments, each of the fins in the plurality of fins defines a corresponding beveled distal edge. 
     Some heat exchange systems also have a unitary body defining a first side and a second side positioned opposite the first side. A portion of the inlet plenum and a portion of the inlet manifold can be respectively recessed from the first side. A recess from the second side can define a pump volute, and the portion of the inlet plenum recessed from the first side can be positioned adjacent the pump volute. The recess defining the pump volute can be a substantially cylindrically-shaped recess having a longitudinal axis extending substantially perpendicularly to the second side. The unitary body can define an opening extending generally tangentially of the cylindrically-shaped recess and hydraulically couple the pump volute to the inlet plenum. 
     The body can define a second recessed region adjacent the inlet manifold recess and a wall separating the second recessed region from the inlet manifold recess. The manifold body can be configured to straddle the inlet manifold recess and matingly engage the body such that the manifold body so occupies a portion of the second recessed region as to define an exhaust manifold that generally overlies a respective portion of each of the microchannels. The respective portions of the plurality of microchannels can be spaced from the inlet manifold. 
     In accordance with yet another broad aspect of the disclosed innovations, some described heat exchange systems have a heat sink with a plurality of juxtaposed fins defining a corresponding plurality of microchannels between adjacent fins. Each of the fins can define a respective beveled distal edge. A manifold body can overlie at least a portion of each of the beveled distal edges and define an opening configured to deliver a flow of fluid to the microchannels in a direction transverse to the microchannels. 
     A distance between a respective beveled distal edge and the heat spreader can define a height of the respective fin. Each respective fin can define a first end and a second end, and extend longitudinally in a spanwise direction relative to the heat spreader between the first and the second end. The respective fin height of one or more of the plurality of fins can vary along the spanwise direction. The manifold body can have a compliant portion urging against at least a portion of each of the distal edges. For example, the variation in fin height along the spanwise direction can define a non-linear contour of the respective distal edge, and the compliant portion of the manifold body can generally conform to the non-linear contour. 
     A recessed groove can extend transversely relative to the fins and the opening can generally overlie the groove. Each of the respective distal edges can define a corresponding recessed portion, thereby defining the recessed groove. 
     A ratio of a representative height of the plurality of fins to a representative depth of the groove can be between about 10:1 and about 10:7. For example, the ratio of the representative height to the representative depth can be between about 3:1 and about 2:1. 
     According to another broad aspect of the disclosed innovations, unitary constructs are described. For example, a unitary construct can have a first side, a second side positioned opposite the first side, and a substantially continuous perimeter wall extending between the first side and the second side. A floor can generally separate the first side from the second side. The first side can define a substantially cylindrically-shaped recess and the second side can define a recess having a region positioned radially outward of the substantially cylindrically-shaped recess defined by the first side. 
     In some instances, the unitary construct can define an aperture extending between the substantially cylindrically-shaped recess and the portion of the recess from the second side positioned radially outward of the substantially cylindrically-shaped recess. 
     The perimeter wall can define one or more perimeter recesses. The construct can define an aperture in the floor extending between one of the perimeter recesses and the substantially cylindrically-shaped recess. The construct can define an aperture extending between one of the perimeter recesses and the recess defined by the second side. The construct can define an aperture extending between one of the perimeter recesses and the portion of the recess from the second side positioned radially outward of the substantially cylindrically-shaped recess. 
     The one or more perimeter recesses can include a first perimeter recess and a second perimeter recess. The construct can define an aperture extending between the second perimeter recess and the recess defined by the second side. The perimeter wall can also define a third perimeter recess and the construct can define an aperture extending between the third perimeter recess and the portion of the recess from the second side positioned radially outward of the substantially cylindrically-shaped recess. 
     Some embodiments of the construct generally define a housing. The substantially cylindrically-shaped recess can define a pump volute, and the recess from the second side can define a plenum. The plenum can be a heat sink inlet plenum defined by the portion of the recess from the second side positioned radially outward of the substantially cylindrically-shaped recess. The recess from the second side can define a portion of a heat-sink inlet manifold, a portion of a heat-sink outlet manifold, and a portion of a heat-sink outlet manifold. 
     It is to be understood that other innovative aspects will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments are shown and described by way of illustration. As will be realized, other and different embodiments are possible and several details are capable of modification in various other respects, all without departing from the spirit and scope of the principles disclosed herein. 
     Accordingly the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Unless specified otherwise, the accompanying drawings illustrate aspects of the innovative subject matter described herein. Referring to the drawings, wherein like reference numerals indicate similar parts throughout the several views, several aspects of the presently disclosed principles are illustrated by way of example, and not by way of limitation, in detail in the drawings, wherein: 
         FIG. 1  shows a fluid circuit configured to transfer heat from one region to another with a circulatable working fluid. 
         FIG. 2  shows a top plan view of a fluid heat exchanger having a top cap cut away to facilitate viewing internal components; 
         FIG. 3  shows a sectional view along line I-I of  FIG. 2 ; 
         FIG. 4  shows a sectional view along line II-II of  FIG. 3 ; 
         FIG. 5  shows an exploded, perspective view of another fluid heat exchanger; 
         FIG. 6  shows a top plan view of the fluid heat exchanger shown in  FIG. 5  assembled with its top cap removed; 
         FIG. 7  illustrates an exploded view of an embodiment of an integrated pump and heat exchanger assembly. 
         FIG. 8  illustrates an isometric view of an exploded subassembly of the integrated housing and pump impeller shown in  FIG. 7 . 
         FIG. 9  illustrates a partial cross-sectional view from above the integrated housing shown in  FIGS. 7 and 8 . 
         FIG. 10  illustrates an isometric view from below of the integrated housing shown in  FIGS. 7, 8 and 9  with a flow path of a fluid shown as a dashed line. 
         FIG. 11  illustrates an exploded view of a subassembly comprising the heat sink, the integrated housing and the manifold insert shown in  FIG. 7 . 
         FIG. 12  illustrates an isometric view from above the insert shown in  FIGS. 7 and 11 . 
         FIG. 13  illustrates an isometric view of a heat sink as shown in  FIG. 7 . 
         FIG. 13A  shows a magnified view of a portion of the heat sink shown in  FIG. 13 . 
         FIG. 14  illustrates an isometric view of another embodiment of a heat sink shown in  FIG. 7 . 
         FIG. 14A  shows a magnified view of a portion of the heat sink shown in  FIG. 14 . 
         FIG. 15  illustrates a typical cross-sectional view of a heat sink as shown in  FIG. 7 , e.g., as taken along Section  15 - 15  in  FIG. 13  or in  FIG. 14 . 
         FIG. 16  illustrates an example of beveled fins. 
         FIG. 17  illustrates an example of blunt fins. 
         FIG. 18A  illustrates a cross-sectional view of a heat sink having a v-shaped, transverse groove in its fins as taken along section line  18 - 18  in  FIG. 14 . 
         FIG. 18B  illustrates a cross-sectional view of a heat sink having a generally parabolic, transverse groove in its fins as taken along section line  18 - 18  in  FIG. 14 . 
         FIG. 19  illustrates a cross-sectional view of a heat sink as shown in  FIG. 18A  with the manifold insert shown in  FIG. 12  overlying the fins of the heat sink. 
         FIG. 19A  illustrates a cross-sectional view of a heat sink as shown in  FIG. 18A  having the manifold insert shown in  FIG. 12  overlying the fins of the heat sink. 
         FIG. 19B  illustrates another cross-sectional view of a heat sink defining a transverse groove and having the manifold insert shown in  FIG. 12  overlying the fins. 
     
    
    
     DETAILED DESCRIPTION 
     The following describes various innovative principles related to heat exchange systems by way of reference to specific examples. However, one or more of the disclosed principles can be incorporated in various system configurations to achieve any of a variety of corresponding system characteristics. The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the principles disclosed herein. However, it will be apparent to those skilled in the art after reviewing this disclosure that one or more of the claimed inventions may be practiced without one or more of the illustrated details. 
     Stated differently, systems described in relation to particular configurations, applications, or uses, are merely examples of systems incorporating one or more of the innovative principles disclosed herein and are used to illustrate one or more innovative aspects of the disclosed principles. Thus, heat exchange systems having attributes that are different from those specific examples discussed herein can embody one or more of the innovative principles, and can be used in applications not described herein in detail, for example to transfer heat to or from components in a data center, laser components, light-emitting diodes, chemical reactions, photovoltaic cells, solar collectors, electronic components, power electronics, opto-electronics (e.g., used in switches) and a variety of other industrial, military and consumer devices now known or hereafter developed. Accordingly, such alternative embodiments also fall within the scope of this disclosure. 
     Fluid Circuit 
     The schematic illustration in  FIG. 1  shows several functional features common among disclosed fluid-based heat exchanger systems. For example, the fluid circuit  10  has a first heat exchanger  11  configured to absorb heat from a heat source (not shown in  FIG. 1 ) and a second heat exchanger  12  configured to reject heat from the circuit  10 . As indicated in  FIG. 1 , a working fluid, or coolant, can circulate between the heat exchangers  11 ,  12  to carry the energy absorbed by the working fluid in the first heat exchanger to the second heat exchanger  12  where energy can be rejected from the fluid. One or both of the heat exchangers  11 ,  12  can be a microchannel heat exchanger. 
     As used herein, “microchannel” means a fluid conduit, or channel, having at least one major dimension (e.g., a channel width) measuring less than about 1 mm, such as, for example, about 0.1 mm, or several tenths of millimeters. 
     As used herein, “fluidic” means of or pertaining to a fluid (e.g., a gas, a liquid, a mixture of a liquid phase and a gas phase, etc.). Thus, two regions that are “fluidicly coupled” are so coupled to each other as to permit a fluid to flow from one of the regions to the other region in response to a pressure gradient between the regions. 
     As used herein, the terms “working fluid” and “coolant” are interchangeable. Although many formulations of working fluids are possible, common formulations include distilled water, ethylene glycol, propylene glycol, and mixtures thereof. 
     As used herein, the terms “heat sink” and “heat exchanger” are interchangeable and mean a device configured to transfer energy to or from a fluid through convection (i.e., a combination of conduction and advection) heat transfer. 
     Referring again to  FIG. 1 , the working fluid typically enters a first manifold  13  (sometimes after passing through an inlet plenum, which is omitted from  FIG. 1  for ease of illustration). From the manifold  13 , the fluid can be distributed among a plurality of fluid passages  14  configured to transfer heat from a heat-transfer surface, e.g., a wall in the heat exchanger  11 , to the working fluid. In some embodiments, such as the examples described below, the fluid passages  14  are configured as microchannels and the walls are configured as extended heat-transfer surfaces, or fins. 
     During operation of the circuit  10 , energy conducts (e.g., diffuses) from the walls of the first heat exchanger into adjacent fluid particles within the passages  14 , and the adjacent fluid particles are swept away from the wall, or advected, carrying the energy absorbed from the walls. The swept-away particles are replaced by other, usually cooler fluid particles, which more readily absorb energy from the walls (e.g., by virtue of their usually lower temperature). Such a combination of conduction and advection (i.e., convection) provides an efficient approach for cooling devices having a relatively high heat flux, such as, for example, electronic devices. 
     After passing through the plurality of passages  14  in the first heat exchanger  11 , the heated working fluid collects in an exhaust manifold  15  and passes to the second heat exchanger  12 , carrying with it the energy absorbed from the first heat exchanger  11 . As the heated fluid passes through the second heat exchanger  12 , energy is rejected from the fluid (e.g., to another working fluid, such as, for example, the air or a building&#39;s water supply) through convection processes similar to those described above. From the second heat exchanger, the cooled working fluid passes through a pump  16  and back to the first heat exchanger  11 . 
     The dashed box in  FIG. 1  indicates that several functional components of the circuit  10  can be integrated into a single subassembly. As an example, the subassembly  20  includes the pump  16 , the manifolds  13 ,  15  and the passages  14 , as well as, for example, conduits between the pump and the manifold  13 . An inlet  21  and an outlet  22  operatively couple the subassembly  20  to the second heat exchanger  12 . A working embodiment of such a subassembly  20  is described below in connection with  FIG. 7 , et seq. 
     Each of the innovative features described herein can be incorporated, either singly or in combination, in connection with the first heat exchanger  11 , the second heat exchanger  12 , or both. 
     Heat Exchanger Example 
     With reference to  FIGS. 2 to 4 , a fluid heat exchanger  100  is shown. Fluid heat exchanger  100  includes a heat spreader plate  102 , an arrangement of fluid microchannels  103  defined between walls  110 , a fluid inlet passage  104 , and a fluid outlet passage  106 . A housing  109  operates with heat spreader plate  102  to form an outer limit of the heat sink and to define fluid flow passages  104 ,  106 . 
     As shown in  FIGS. 3 and 4 , in use the heat exchanger  100  is coupled to a heat source  107 , such as an electronic device, including, but not limited to a microchip or an integrated circuit. The heat exchanger may be thermally coupled to the heat source by a thermal interface material disposed therebetween, by coupling directly to the surface of the heat source, or by integrally forming the heat source and at least the heat spreader plate  102  of the fluid heat exchanger. The heat exchanger  100  may take various forms and shapes, but heat spreader plate  102  is formed to accept thermal energy from heat source  107 . Heat spreader plate  102  includes an intended heat generating component contact region  102   b  positioned in a known location thereon. In the illustrated embodiment, heat spreader plate  102  includes a protrusion at region  102   b  that controls the positioning of the heat spreader plate relative to the heat source, but such a protrusion need not be included. Heat spreader plate  102  may include a portion of more conductive material to facilitate and control heat transfer, if desired. In any event, heat spreader plate is formed to fit over and thermally communicate with a heat source in a region  102   b , usually located centrally relative to the edges of the heat spreader plate. 
     Microchannels  103  are formed to accept and allow passage therethrough of the flow of heat exchanging fluid such that the fluid can move along heat spreader plate  102  and walls  110  and accept and dissipate heat energy from them. In the illustrated embodiment, microchannels  103  are defined by walls  110  that are thermally coupled to the heat spreader plate to accept thermal energy therefrom. For example, heat spreader plate  102  may include an inner facing, upper surface  102   a  and a plurality of microchannel walls  110  may extend upwardly therefrom, whereby the channel area, defined between upper surface  102   a  and the microchannel walls  110 , channels or directs fluid to create a fluid flow path. The channel area may be open or filled with thermally conductive porous material such as metal or silicon foam, sintered metal, etc. Thermally conductive, porous materials allow flow through the channels but create a tortuous flow path. 
     Surface  102   a  and microchannel walls  110  allow the fluid to undergo exchange of thermal energy from the heat spreader plate to cool the heat source coupled to the heat spreader plate. The upper surface  102   a  and walls  110  have a high thermal conductivity to allow heat transfer from the heat source  107  to fluid passing through channels  103 . The surfaces forming channels  103  may be smooth and solid, formed with a porous structure, such as of sintered metal and/or metal or silicon foam or roughened, for example, including troughs and/or crests designed to collect or repel fluid from a particular location or to create selected fluid flow properties. Facing microchannel walls  110  may be configured in a parallel configuration, as shown, or may be formed otherwise, provided fluid can flow between the microchannel walls  110  along a fluid path. It will be apparent to one skilled in the art that the microchannel walls  110  may be alternatively configured in any other appropriate configuration depending on various factors of desired flow, thermal exchange, etc. For instance, grooves may be formed between sections of microchannel walls  110 . Generally, microchannel walls  110  may desirably have dimensions and properties which seek to reduce or possibly minimize the pressure drop or differential of fluid flowing through the channels  103  defined therebetween. 
     The microchannel walls  110  may have a width dimension within the range of 20 microns to 1 millimeter and a height dimension within the range of 100 microns to five millimeters, depending on the power of the heat source  107 , desired cooling effect, etc. The microchannel walls  110  may have a length dimension which ranges between 100 microns and several centimeters, depending on the dimensions of, and the heat flux density from, the heat source. In one embodiment, the walls  110  extend the full length (which may be a width) dimension of the heat spreader plate passing fully through region  102   b . These are exemplary dimensions and, of course, other microchannel wall dimensions are possible. The microchannel walls  110  may be spaced apart by a separation dimension range of 20 microns to 1 millimeter, depending on the power of the heat source  107 , although other separation dimensions are contemplated. 
     Other microporous channel configurations may be used alternatively to, or together with, microchannels, such as for example, a series of pillars, fins, or undulations, etc. which extend upwards from the heat spreader plate upper surface or tortuous channels as formed by a foam or sintered surface. 
     Fluid heat exchanger  100  further includes a fluid inlet passage  104 , which in the illustrated embodiment includes a port  111  through the housing opening to a header  112  and thereafter a fluid inlet opening  114  to the microporous fluid channels  103 . 
     Fluid Distribution 
     The port and the header can be formed in various ways and configurations. For example, port  111  may be positioned on top, as shown, side or end regions of the heat exchanger, as desired. Port  111  and header  112  are generally of a larger cross sectional area than opening  114 , so that a mass flow of fluid can be communicated substantially without restriction to opening  114 . 
     Although only a single fluid inlet opening  114  is shown, there may be one or more fluid inlet openings providing communication from the header to the fluid microchannels  103 . 
     Fluid inlet opening  114  may open to microchannels  103  opposite the heat spreader plate such that fluid passing through the opening may pass between walls  110  toward surface  102   a , before being diverted along the axial length of the channels, which extend parallel to axis x. Since most installations will position the heat spreader plate as the lowermost, as determined by gravity, component of heat exchanger  100 , the fluid inlet openings  114  can generally be described as being positioned above the microchannels  103  such that fluid may flow through opening  114  down into the channels in a direction orthogonal relative to the plane of surface  102   a  and towards surface  102   a  and then change direction to pass along the lengths of channels  103  substantially parallel to surface  102   a  and axis x. Such direction change is driven by impingement of fluid against surface  102   a.    
     Fluid inlet opening  114  may be positioned adjacent to the known intended heat generating component contact region  102   b  since this region of the heat spreader plate may be exposed to greater inputs of thermal energy than other regions on plate  102 . Positioning the fluid inlet opening adjacent region  102   b  seeks to introduce fresh heat exchanging fluid first and directly to the hottest region of the heat exchanger. The position, arrangement and/or dimensions of opening  114  may be determined with consideration of the position of region  102   b  such that opening  114  may be placed adjacent, for example orthogonally opposite to, or according to the usual mounting configuration above, the intended heat generating component contact region  102   b  on the heat plate. The delivery of fresh fluid first to the region that is in direct communication with the heat generating component to be cooled seeks to create a uniform temperature at the contact region as well as areas in the heat spreader plate away from the contact region. 
     In the illustrated embodiment, opening  114  is positioned to have its geometric center aligned over the center, for example the geometric center, of region  102   b . It is noted that it may facilitate construction and installation by intending, and possibly forming, the heat sink spreader plate to be installed with the heat generating component positioned on the plate substantially centrally, with respect to the plate&#39;s perimeter edges, and then opening  114  may be positioned also with its geometric center substantially centrally with respect to the perimeter edges of the heat spreader plate. In this way, the geometric center points of each of opening  114 , the heat spreader plate and the heat generating component may all be substantially aligned, as at C. 
     Opening  114  may extend over any channel  103  through which it is desired that heat exchange fluid flows. Openings  114  may take various forms including, for example, various shapes, various widths, straight or curved edges (in plane or in section) to provide fluid flow features, open area, etc., as desired. 
     Heat exchanger  100  further includes a fluid outlet passage  106 , which in the illustrated embodiment includes one or more fluid outlet openings  124  from the microporous fluid channels  103 , a header  126  and an outlet port  128  opening from the housing. Although two fluid outlet openings  124  are shown, there may be one or more fluid outlet openings providing communication to the header from the fluid channels  103 . 
     The port and the header can be formed in various ways and configurations. For example, port  128  may be positioned on top, as shown, side or end regions of the heat exchanger, as desired. 
     Fluid outlet openings  124  may be positioned at the end of microchannels  103 . Alternately or in addition, as shown, fluid outlet openings  124  may create an opening opposite heat spreader plate  102  such that fluid passing through the channels pass axially along the length of the channels between walls  110  and then changes direction to pass away from surface  102   a  out from between the walls  110  to exit through openings  124 . Since most installations will position the heat spreader plate as the lowermost, as determined by gravity, component of heat exchanger  100 , the fluid outlet openings  124  will generally be positioned above the microchannels  103  such that fluid may flow from the channels upwardly through openings  124 . 
     Fluid outlet openings  124  may be spaced from fluid inlet openings  114  so that fluid is forced to pass through at least a portion of the length of channels  103  where heat exchange occurs before exiting the microchannels. Generally, fluid outlet openings  124  may be spaced from the known intended heat generating component contact region  102   b.    
     In the illustrated embodiment, where heat exchanger  100  is intended to be mounted with heat source  107  generally centrally positioned relative to the perimeter edges of heat spreader plate  102 , and thereby the ends  103   a  of channels, openings  124  may be positioned at or adjacent channel ends  103   a.    
     At least one opening  124  extends over any channel  103  through which it is desired that heat exchange fluid flows. Openings  124  may take various forms including, for example, various shapes, various widths, straight or curved edges (in plane or in section) to provide fluid flow features, open area, etc. as desired. 
     Fluid inlet opening  114  may open away from the ends of the microchannels, for example along a length of a microchannel between its ends. In this way, fluid is introduced to a middle region of a continuous channel  103  rather than fluid being introduced to one end of a channel and allowing it to flow the entire length of the channel. In the illustrated embodiment, heat exchanger  100  is intended to be mounted with heat source  107  generally centrally positioned relative to the perimeter edges of heat spreader plate  102 . As such, in the illustrated embodiment, opening  114  is positioned generally centrally relative to the edges of the heat plate  102 . Since the channels, in the illustrated embodiment extend substantially continuously along the length of the heat plate between opposing side perimeter edges thereof, opening  114  opens generally centrally between ends  103   a  of each channel. For example, opening  114  may be positioned in the middle 50% of the heat exchanger or possibly the middle 20% of the heat exchanger. The delivery of fresh fluid to the central region where the heat generating component is in direct communication with the heat spreader plate, first before passing through the remaining lengths of channels seeks to create a uniform temperature at region  102   b  as well as areas in the heat spreader plate adjacent to the intended mounting position. The introduction of fluid to a region along a middle region of the microchannels after which the flow splits into two sub flows to pass outwardly from the inlet towards a pair of outlets, each of which is positioned at the ends of the channels reduces the pressure drop of fluid passing along the channels over that pressure drop that would be created if the fluid passed along the entire length of each channel. Splitting the fluid flow to allow only approximately one half of the mass inlet flow to pass along any particular region of the microchannels creates less back pressure and less flow resistance, allows faster fluid flow through the channels and lessens the pump force required to move the fluid through the heat exchanger. 
     In use, heat spreader plate  102  is positioned in thermal communication with heat source  107  at region  102   b . Heat generated by heat source  107  is conducted up through heat spreader plate  102  to surface  102   a  and walls  110 . Heat exchanging fluid, as shown by arrows F, enters the fluid heat exchanger through port  111 , passes into the header  112  and through opening  114 . The heat exchanging fluid then passes down between walls  110  into channels  103 , where the fluid accepts thermal energy from the walls  110  and surface  102   a . The heat exchanging fluid, after passing down into the channels, then impinges against surface  102   a  to be diverted toward ends  103   a  of the channels toward outlet openings  124 . In so doing, in the illustrated embodiment, the fluid is generally split into two subflows moving away from each other and away from inlet  114  toward openings  124  at the ends of the microchannels. Fluid passing through channels becomes heated, especially when passing over the region in direct contact with the heat source, such as, in the illustrated embodiment, the central region of the heat spreader plate. Heated fluid passes out of openings  124 , into header and thereafter through port  128 . The heated fluid will circulate through a heat sink where its thermal energy is unloaded before circulating back to port  111 . 
     The individual and relative positioning and sizing of openings  114  and  124  may allow fluid to circulate through the heat exchanging channels  103  while reducing the pressure drop generated in fluid passing through heat exchanger  100 , when compared to other positionings and sizings. In the illustrated embodiment, for example, the central region  124   a  of outlet openings  124  are scalloped to offer an enlarged outlet region from the centrally located channels, relative to those on the edges. This shaping provides that the outlet openings from some centrally positioned channels  103 , relative to the sides of the heat exchanger, are larger than the outlet openings from other channels closer to the edges. This provides that fluid flowing through the more centrally located channels encounters less resistance to flow therethrough, again facilitating flow past the central mounting region  102   b  on heat spreader plate  102 . 
     A seal  130  separates fluid inlet passage  104  from fluid outlet passage  106  so that fluid must pass through the microporous channels  103  past heat spreader plate surface  102   a.    
     Methods of Manufacture 
     With reference to  FIGS. 5 and 6 , a useful method for manufacturing a fluid heat exchanger is described. A heat spreader plate  202  may be provided which has heat conductive properties through its thickness at least about a central region thereof. 
     Microchannels may be formed on the surface of the heat spreader plate, as by adding walls or forming walls by building up or removing materials from the surface of the heat plate. In one embodiment, skiving is used to form walls  210 . 
     A plate  240  may be installed over the walls  210  to close off the channels across the upper limits of walls  210 . Plate  240  has portions removed to create inlet and outlet openings  214  and  224 , respectively, in the final heat exchanger. Tabs  242  may be used to assist with the positioning and installation of plate  240 , wherein tabs  242  are bent down over the two outermost walls. 
     Seal  230  may be installed as a portion of plate  240  or separately. 
     After plate  240  and seal  230  are positioned, a top cap  244  can be installed over the assembly. Top cap  244  can include side walls that extend down to a position adjacent heat spreader plate. The parts may be connected during assembly thereof or afterward by overall fusing techniques. In so doing, the parts are connected so that short circuiting from inlet passage to outlet passage is substantially avoided, setting up the fluid circuit as described herein above wherein the fluid flows from opening  214  to openings  224  through the channels defined between walls  210 . 
     System Integration 
     Referring now to  FIG. 7 , a working example of an integrated subassembly  20  ( FIG. 1 ) is described. The illustrated subassembly  300  comprises a pump  310  (e.g.,  312  and  313 , exclusive of retention mechanism  302 ) and a heat exchanger  320 , as well as housing  330  with integrated fluid conduits extending therebetween. The subassembly  300  is but one example of an approach for integrating several elements of the fluid circuit  10  shown in  FIG. 1  (e.g., the pump  16  and the first heat exchanger  11 , including the inlet manifold  13 , the fluid passages  14 , the exhaust manifold  15 ) into a single element while retaining the several elements&#39; respective functions. The illustrated housing  330  is configured to convey a working fluid from an inlet port  331  to a pump volute  311 , from the pump volute to an inlet  321  ( FIG. 11 ) to the heat exchanger  320 , and from an outlet  322  ( FIG. 11 ) of the heat exchanger to an outlet port  332 . 
     The pump impeller  312  can be received in the pump volute  311 . The impeller can be driven in rotation by an electric motor  313  in a conventional manner. A cap  301  can overlie the motor  313  and fasten to the housing  330  to provide the subassembly  300  with a finished appearance suitable for use with, for example, consumer electronics. 
     The side  333  of the housing  330  positioned opposite the pump volute  311  can receive an insert  334  and the heat exchanger  320 . A seal (e.g., an O-ring)  323  can be positioned between the housing  330  and the heat exchanger  320  to reduce and/or eliminate leakage of the working fluid from the interface between the heat exchanger  320  and the housing  330 . 
     The heat exchanger  320  defines a lower-most face of the assembly  300 , as well as a surface configured to thermally couple to an integrated circuit (IC) package (not shown). A retention mechanism  302  can mechanically couple the assembly to a substrate, such as a printed circuit board to which the IC package is assembled. 
     As with the subassembly  20  shown in  FIG. 1 , a fluid conduit, or other fluid coupler, can fluidicly couple an outlet port of a remotely positioned heat exchanger to the inlet port  331  of the housing  330 . As well, a fluid conduit, or other fluid coupler, can fluidicly couple the outlet port  332  of the housing  330  to an inlet port of the remotely positioned heat exchanger. In a cooling application, the respective fluid conduits convey relatively higher-temperature fluid from the outlet port  332  to the remote heat exchanger and relatively lower-temperature fluid from the remote heat exchanger to the inlet port  331 . 
     Integrated Housing 
     An embodiment of a unitary housing  330  is now described by way of reference to  FIGS. 7, 8, 9, 10 and 11 . The illustrated housing  330  has a first side  340 , a second side  333  positioned opposite the first side, and a substantially continuous perimeter wall  348  extending between the first side and the second side. A floor, or lower wall,  341  ( FIG. 9 ) generally separates the first side from the second side. The opposed first side  340  and second side  333  define respective recessed features that, when combined with corresponding components, define integrated fluid conduits and chambers operable to convey a working fluid within a small form factor (e.g., within a volume having a maximum vertical dimension of less than about 1.5 inches, such as, for example, between about 0.75 inches and about 1.4 inches). 
     For example, the housing has an inlet port  331 , a pump volute  311 , an inlet plenum  335  ( FIG. 10 ), an inlet manifold portion  336  corresponding to the inlet plenum, an exhaust manifold portion  337 , an exhaust (or outlet) plenum  338  corresponding to the exhaust manifold portion, and an outlet port  332  fluidicly coupled with each other. 
       FIGS. 8 and 9  show that the perimeter wall can define a recessed inlet port  331 . The first side  340  of the housing  330  defines a substantially cylindrically-shaped recess forming the pump volute  311 , and a floor of the recessed volute  311  is defined by a substantially circular lower wall  341 . An aperture  342  in the lower wall forms an inlet to the pump volute  311  from the inlet port, with an inlet passage  343  extending between the inlet port  331  and the inlet  342  to the pump volute  311 , fluidicly coupling the pump volute and the inlet port to each other. 
     The opposite (e.g., a second) side  333  of the housing  330  defines a second recessed region  350  defining the inlet (e.g., first) plenum  335  and the inlet manifold region  336 . An opening  344  extends through a common wall  345  separating the inlet plenum  335  from the pump volute  311  (not shown in  FIG. 10 ), fluidicly coupling the pump volute and the first plenum with each other. In some embodiments, the opening  344  extends generally tangentially of the cylindrically-shaped pump volute  311 . 
     A charge port  349  can extend through the perimeter wall  348  and into the inlet plenum  335 , allowing an assembled system to be charged with a working fluid after assembly is complete. After charging, a plug (not shown) can be inserted into the charge port  349  to seal it. 
     As shown in  FIG. 10 , a depth of the inlet manifold  336  can taper from a relatively deeper region adjacent the inlet plenum  335  to a relatively shallower region spaced from the inlet plenum. As shown in  FIG. 11  and described more fully below, a manifold insert  334  can be positioned adjacent, e.g., “overlie”, as shown in  FIG. 7 , the sloped recess of the manifold region  336 , at least partially forming an inlet manifold to the heat sink  320  and having a tapering cross-sectional area along a flow direction. The tapered manifold can distribute a substantially even mass-flow rate of working fluid among a plurality of channels in the heat sink  320 . 
     The second side  333  of the housing  330  can define a third recessed region  351  ( FIG. 10 ) defining respective portions of an exhaust manifold  337  ( FIG. 11 ). As described more fully below, the third recessed region  351  can overlie a portion of the heat exchanger  320  and thereby receive a discharged working fluid from the microchannels. 
     A fourth recessed region  352  ( FIG. 10 ) can define, at least in part, an outlet plenum  338 . The third recess  351  and the fourth recess  352  can be fluidicly coupled to each other and separated by a wall  346  from the second recessed region  350 . An opening  347  ( FIG. 9 ) can extend between the outlet plenum  338  and the outlet port  332 . 
     A manifold housing, or integrated housing, as described above can have a unitary construction formed using, for example, an injection molding technique, a machining technique, or other suitable process now known or hereafter developed. Also, any suitable material can be used in the construction of the housing, provided that the material is compatible with other components of the subassembly  300  and the working fluid. For example, common materials from which an injection-molded housing can be formed include polyphenylene sulfide (commonly referred to as “PPS”), polytetrafluoroethylene (commonly referred to as “PTFE” or the trade name TEFLON by the DuPont Company), and acrylonitrile butadiene styrene (commonly referred to as “ABS”). 
     Although the housing described above has a unitary construction, other embodiments of the housing  330  can comprise an assembly of subcomponents. Nonetheless, a unitary construction typically has fewer separable couplings from which a working fluid can leak. 
     Manifold Insert 
     As noted above and shown in  FIGS. 7 and 11 , an insert  334  can be positioned between the heat exchanger  320  and the housing  330 . Additionally, the insert  334  can have a contour generally corresponding to the configuration of one or more of the recessed regions  350 ,  351 ,  352  in the second side  333  of the housing  330 . When the insert  334  is mated with the housing  330 , the recessed regions  350 ,  351  and  352 , in combination with the contoured insert  334 , can define several conduits, or fluid couplers, suitable for conveying a working fluid so as to fluidicly couple the heat exchanger  320  with the pump volute  311  and the outlet port  332 . 
     For example, the insert  334  can define an opening extending through the body  360  and generally overlying the tapered manifold portion  336  defined by the housing  330 . The opening can include a recessed region  365  and an aperture  361 . The recessed region  365  and the tapered recess  336  in the housing together define a chamber of the inlet manifold. As described below, the manifold can distribute working fluid among the several microchannels within the heat sink. 
     The body  360  of the insert  334  can matingly engage with one or more features of the housing  330 . For example, the body  360  can define a plurality of spaced apart members  362   a, b, c, d  and a trough-shaped recess  363  extending transversely relative to the aperture  361 . The trough-shaped recess  363  can extend between the members  362   a, c  and between the members  362   b, d . When the insert  334  is assembled with the housing  330 , the members  362   a, b, c, d  are positioned in corresponding portions of the second recessed region  351 , and a corresponding ridge  339  ( FIG. 10 ) is positioned within the trough-shaped recess  363 . By straddling features defined by the housing, the insert is configured to align the aperture  361  with the tapered manifold region  336  in a generally repeatable fashion. 
     The insert body  360  also defines a contoured tab  364  configured to overly the recessed inlet plenum  335 . In addition, a shoulder  366  within the second recessed region  365  of the insert urges against the wall  346  ( FIG. 10 ), providing a seal separating the inlet manifold from the exhaust manifold and outlet plenum. 
     In a working embodiment, the recessed region  365  ( FIG. 19 ) is tapered, having at least one cross-sectional dimension that diminishes with increasing depth of the recess. As explained more fully below, the recess  365  and the aperture  361  in the insert can generally overlie a groove  325  ( FIG. 19 ) in the heat sink fins. In some instances, a slope of a wall defining the tapered recess  365  adjacent the aperture  361  can be matched to (e.g., can correspond to, or, alternatively, be the same as) a slope of the recessed groove  325  adjacent a distal end of the heat sink fins, providing a relatively smooth and continuous flow transition. 
     The insert can have one or more (e.g., a pair) of generally conformable, flat surfaces  367  laterally flanking the aperture  361  ( FIG. 11 ). As shown in  FIG. 19 , the surfaces  367  can generally overlie respective portions of the heat exchanger  320  (e.g., the distal ends  401  of heat sink fins  400  ( FIGS. 16 and 17 )), defining an upper flow boundary of the microchannels extending between adjacent fins, similar to the plate  240  shown in  FIGS. 5 and 6 . The conformable surfaces  367  can urge against the respective distal ends, and conform to variations in height among the plurality of fins, and within a given fin (e.g., a fin having a non-linear longitudinal contour resulting from variations in fin height h 2  ( FIGS. 18A and 18B )). The conformable surfaces  367  can reduce or eliminate the need for secondary machining operations used to make the respective distal ends of the fins generally coplanar and compatible with, for example, a rigid plate. As well, conformable surfaces  367  urging against the distal ends  401  of the fins  400  ( 400 ′) can form a seal with the fins and prevent a working fluid from bypassing the channels defined between adjacent fins. 
     The insert body  360  can be formed using, for example, an injection molding technique, a machining technique, or other suitable process now known or hereafter developed. In a working embodiment, the body  360  is formed of a compliant polymeric material that generally conforms to and seals against adjacent surfaces. Any suitable material can be used to form the insert body  360 , provided that the selected material is compatible with other components of the subassembly  300  and the selected working fluid. For example, common materials from which the insert body can be formed include silicone or any other suitably compliant material. 
     Flow Distribution 
     Flow of a working fluid through the integrated assembly  300  is now described. From a remotely positioned heat exchanger (not shown), a working fluid passes into the inlet port  331  and into the channel  343  extending between the inlet port and the inlet  342  to the pump volute  311 . A floor  341  of the pump volute defines a wall separating the channel  343  from the pump volute. From the channel  343 , the working fluid passes through the aperture  342  and into the volute  311 . An impeller  312  positioned in the pump volute  311  rotates and increases a pressure head in the working fluid before the fluid passes from the pump volute through the opening  344  and into the inlet plenum  335 . 
     As indicated by the arrows in  FIG. 10 , the working fluid can pass from the inlet plenum  335  and into a chamber formed between the second recessed region  365  in the insert  334  and the inlet manifold portion  336  of the housing. From the chamber, the working fluid passes through the aperture  361 . 
     As described above in connection with  FIGS. 2, 3 and 4 , the heat exchanger shown in  FIGS. 7, 11, 13 and 14  can comprise a heat transfer region  324  defining a plurality of microchannel passages. The aperture  361  can overlie the heat transfer region  324 , and the flow of working fluid can be distributed among the plurality of microchannel passages in the heat sink. As with the assembly shown in  FIGS. 5 and 6 , a flow of working fluid within the microchannel can generally be an impinging flow divided into a first portion and a second portion flowing outwardly from the impingement region in generally opposite directions. 
     In the illustrated assembly  300  ( FIG. 7 ), the insert  334  (e.g., the members  362   a,b,c,d ) partially occupies the third recessed region  351 , leaving a pair of opposed portions of the region unfilled and defining opposed exhaust manifold portions  337  overlying end regions of the microchannels and flanking the central region adjacent the aperture  361  ( FIG. 11 ). The outwardly directed flow of coolant can exhaust from the microchannel passages into a respective one of the exhaust manifold portions  337 . From the manifold portions  337 , the working fluid passes into the outlet plenum  338  ( FIG. 11 ), and through the conduit  347  to the outlet port  332 . 
     Additional Heat Exchanger Configurations 
     Additional heat sink embodiments are described with reference to  FIGS. 13, 13A, 14, 14A, 15, 16, 17, 18A and 18B and 19 . As with the heat sink illustrated in  FIG. 2  through  FIG. 6 , the heat sinks  320 ,  320 ′ shown in  FIGS. 13 and 14  define respective heat transfer regions  324 ,  324 ′ having a plurality of juxtaposed fins (e.g., fins  400 ) defining a corresponding plurality of microchannels (e.g., microchannels  404 ,  404 ′) between adjacent fins. 
     Each of the fins  400 ,  400 ′ extend from a heat spreader, or base,  326 , to a respective distal end  401 ,  401 ′. Flanking grooves  322 ,  322 ′ ( FIGS. 13 and 14 ) can extend orthogonally relative to opposed outer ends of the microchannels  404 ,  404 ′, forming a portion of an exhaust manifold. When incorporated in the assembly  300 , the grooves  322 ,  322 ′ are generally positioned adjacent opposed exhaust manifold portions  337 . 
       FIG. 15  shows a typical cross-sectional view of the heat sinks  320 ,  320 ′ along section line  15 - 15  ( FIG. 13 ) or  15 ′- 15 ′ ( FIG. 14 ), respectively.  FIGS. 16 and 17  show alternative fin configurations from the circled portion “A” of a typical heat transfer region shown in cross-section in  FIG. 15 . 
     The distal ends of the fins can have a variety of configurations, as indicated in  FIGS. 16 and 17 . For example, the blunt distal ends  405 ′ are shown as being relatively flat and generally coplanar. Alternatively, the distal ends  401  are shown as being beveled, giving each fin  400   a  a comparatively shorter face and a comparatively taller face, with a relatively sharp apex  405  positioned therebetween. 
     It is believed that the relatively sharp apex  405  formed by the beveled distal ends  401  can improve transition of a flow direction (e.g., a 90-degree bend) from being generally parallel to the base  326  and orthogonal to the fins  400  to a direction being generally orthogonal to the base  326  and generally parallel to the fins. Accordingly, it is surmised that fins  400  having sharp apices  405  formed by beveled distal ends can reduce head losses in the working fluid as it passes from the insert manifold  365  to the microchannels  404  as compared to, for example, fins  400 ′ having generally blunt distal ends  405 ′. It is believed that positioning the relatively taller face of a given fin upstream of the relatively shorter face of the same fin (e.g., placing the sharp apex in an upstream position relative to the respective fin), provides a relatively larger reduction in head loss than if the flow approaches the beveled fin from an opposite direction. 
     The beveled distal ends  401  can be formed using any suitable technique for beveling thin walls. For example, such bevels can be produced when forming the fins  400  using a skiving technique. Other, e.g., proprietary, techniques can be used to form the bevels. For example, it is believed that the fin-forming technique employed by Wolverine Tube, Inc. can be used to produce microchannel heat sinks having beveled fins. However, it is also believed that the respective distal ends of such “raw” fins may not be coplanar (apart from a recessed region forming a portion of a transverse groove). By incorporating the compliant insert  334 , which can urge against and form a seal with uneven fins, secondary machining operations that would tend to dull the sharp apices  405  can be eliminated, saving costs and improving performance. Maintaining sharp apices  405  and forming a seal with the manifold insert can reduce head losses in the coolant, while still reducing or eliminating leakage between adjacent microchannels  404  that might otherwise occur through gaps that would otherwise be formed between the “raw” fins and, e.g., a generally planar, rigid plate. 
     As shown in  FIG. 14 , a transverse groove  325  can extend transversely relative to the fins  400 . As noted above, the aperture  361  in the manifold insert  334  can generally overlie the groove  325 , defining a flow transition that hydraulically couples in parallel each of the microchannels  404  to at least one other of the microchannels. 
       FIG. 19  shows a cross-sectional view of one example of such a flow transition. The recessed region  365  defined by the insert body  360  and the recessed groove  325  together define a substantially larger characteristic length, e.g., hydraulic diameter, than the aperture  361  does alone. For example, the recessed region  365 , the aperture  361  and the groove  325  can together define a flow transition having a hydraulic diameter between about 150% and about 200% larger than the corresponding hydraulic diameter of the aperture  361  alone, which can provide a substantially lower head-loss coefficient for the assembled flow transition. 
     Increasing the characteristic length scale of the transition from the inlet manifold to the microchannels of the heat sink  320  can reduce pressure losses in a fluid passing through the transition and increase the flow rate of the fluid in correspondence with the pump&#39;s performance. The increase in fluid flow rate resulting from a lower head-loss coefficient can improve local heat transfer rates from the fins compared to a configuration in which the aperture  361  overlies an array of uniform height fins. The combination of the tapered recess  365  and the heat sink groove  325  (e.g., in  FIG. 19A ) allows the working fluid to penetrate relatively deeper in the microchannels in a region adjacent the aperture  361  than the fluid otherwise would in the absence of the groove (e.g., in the case of an array of uniform height fins shown in  FIG. 19A ). 
     The groove  325  can be formed by defining a respective recess in each of the plurality of fins  400 . The plurality of recessed regions can be so juxtaposed as to define the groove  325 . 
     In  FIGS. 18A and 18B , the lowermost extent of each recessed groove  325   a ,  325   b  is spaced a distance h 1  from the heat spreader  326 . In other embodiments, the lowermost extent of the recessed groove  325  is substantially coextensive with the heat spreader  326  (i.e., h 1 ≤0). In some embodiments, a ratio of a representative height h 2  of the fins to the distance h 1  can be between about 10:1 and about 10:7, such as, for example, between about 3:1 and about 2:1. 
     Although a v-shaped notch is shown in  FIG. 18A , and a generally parabolic recess is shown in  FIG. 18B , other recessed groove configurations are possible. For example, the groove can have a generally hyperbolic cross-sectional shape, or a cross-section with at least one substantially straight edge (e.g., an L-shaped recess, a flattened “V”-shaped grove as shown in  FIG. 19B ). As noted above, a slope of the groove  325  adjacent the manifold body can be substantially continuous with a slope of a wall defining the recessed region  365  in the manifold body  360  adjacent the groove, when the integrated assembly  300  is assembled. Such a continuous slope can provide generally lower head losses through the transition than in transitions having a discontinuity in wall slope (e.g., between the recess in the insert and the groove). 
     Other Exemplary Embodiments 
     The examples described above generally concern fluidic heat transfer systems configured to cool one or more electronic components, such as integrated circuits. Nonetheless, other applications for disclosed heat transfer systems are contemplated, together with any attendant changes in configuration of the disclosed apparatus. Incorporating the principles disclosed herein, it is possible to provide a wide variety of systems configured to transfer heat using a fluid circuit. For example, disclosed systems can be used to transfer heat to or from components in a data center, laser components, light-emitting diodes, chemical reactions, photovoltaic cells, solar collectors, and a variety of other industrial, military and consumer devices now known and hereafter developed. 
     Directions and references (e.g., up, down, top, bottom, left, right, rearward, forward, etc.) may be used to facilitate discussion of the drawings but are not intended to be limiting. For example, certain terms may be used such as “up,” “down,”, “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” and the like. Such terms are used, where applicable, to provide some clarity of description when dealing with relative relationships, particularly with respect to the illustrated embodiments. Such terms are not, however, intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” surface can become a “lower” surface simply by turning the object over. Nevertheless, it is still the same surface and the object remains the same. As used herein, “and/or” means “and” or “or”, as well as “and” and “or.” Moreover, all patent and non-patent literature cited herein is hereby incorporated by references in its entirety for all purposes. 
     The principles described above in connection with any particular example can be combined with the principles described in connection with any one or more of the other examples. Accordingly, this detailed description shall not be construed in a limiting sense, and following a review of this disclosure, those of ordinary skill in the art will appreciate the wide variety of fluid heat exchange systems that can be devised using the various concepts described herein. Moreover, those of ordinary skill in the art will appreciate that the exemplary embodiments disclosed herein can be adapted to various configurations without departing from the disclosed principles. 
     The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the disclosed innovations. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of this disclosure. Thus, the claimed inventions are not intended to be limited to the embodiments shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are know or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or “step for”. 
     Thus, in view of the many possible embodiments to which the disclosed principles can be applied, it should be recognized that the above-described embodiments are only examples and should not be taken as limiting in scope. I therefore reserve all rights to the subject matter disclosed herein, including the right to claim all that comes within the scope and spirit of the following claims, as well as all aspects of any innovation shown or described herein.