RELATED APPLICATIONS The present application is a continuation-in-part of and claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Applications Nos. 60/591,646, filed July 28, 2004, entitled, "HEAT EXCHANGER AND LIQUID RESERVOIR," 60/604,952, filed August 27, 2004, entitled, "HEAT EXCHANGER AND LIQUID RESERVOIR," and 60/634,621, filed December 9, 2004, entitled, "HEAT EXCHANGER AND LIQUID RESERVOIR," all three of the aforementioned applications being incorporated herein by reference to the extent not inconsistent with the present disclosure.

BACKGROUND OF THE DISCLOSURE The present disclosure relates generally to the field of fluid reservoirs and more particularly, to use of the fluid reservoirs in appliances having water systems. Fluid reservoirs of the present disclosure can provide for first-in/first-out flow providing beneficial performance characteristics such as, for example, prevention of stagnant flow and improved heat transfer for providing chilled water. For the interface of a water reservoir with an appliance, such as a refrigerator, there are a number of design tradeoffs. Such tradeoffs include, but are not limited to, the fluid reservoirs placement within the appliance, the avoidance of contamination of the water in the fluid reservoirs, the fluid reservoirs fluid capacity, and the efficiency of a heat exchange component are balanced in the design of a fluid reservoir. Among the design criteria for the placement of a water or other liquid reservoir within an appliance such as a refrigerator generally is the desire to occupy the least amount of the storage space within the appliance as possible. For example, prior water system designs have made use of tank-style fluid reservoirs and coiled tube-type fluid reservoirs. One disadvantage of prior known tank-style fluid reservoirs can be the creation of significant un-swept or "dead" volumes with little or no flow. These dead volumes can lead to stagnant flow conditions that can result in stale, poor tasting liquid and/or microbial contamination of the liquid. One known disadvantage of prior coiled tube tanks is that they can have a relatively poor thermal exchange efficiency due to the small portion of the tank surface that is accessible to thermal exchange when mounted in certain configurations. Coil tube fluid reservoirs can also be difficult to manufacture, require large amounts of polymer or other material to manufacture, and can result in bad tasting water due to fluid contact with the large surface area associated with prior known coil tube fluid reservoir materials. Further, prior coil tube fluid reservoirs often exhibit significant internal friction that can result in large pressure drops during operation.

SUMMARY OF THE DISCLOSURE Improved fluid reservoirs of the present disclosure comprise structure to eliminate low flow conditions so as to have little or no un-swept or dead volumes within the fluid reservoir, hi addition, the improved fluid reservoirs of the present disclosure can provide for relatively high efficient thermal exchange so as to provide a desirable chilled fluid product for use and consumption, hi some representative, presently preferred, embodiments, improved fluid reservoirs can comprise a serpentine fluid flow passage having a cross-section configured such that the fluid flow within the flow passage sweeps the entire cross-sectional volume of the flow passage without leaving significant amounts of dead or un-swept volume therein. The cross-sectional shape of the flow passage can be configured to have a larger heat transfer surface than known prior coiled tube reservoirs, which can allow the fluid to be chilled through placement of improved fluid reservoir in proximity to a cooling environment such as, for example, within or in proximity to a refrigeration or freezer compartment in a refrigerator. In some representative embodiments, the improved fluid reservoirs can be operatively assembled, such as, for example, from two sheets of molded polymer material that are operatively joined to form the fluid reservoir, as will be described below, hi other representative embodiments, the fluid reservoir can be operatively assembled, such as, for example, from flexible polymer materials that are bonded along seams to establish a flow channel. In some representative embodiments, improved fluid reservoirs can comprise non- rigid designs in which, contours of a flow channel or flow passage may not form until fluid flow deforms the flexible polymer along the flow channel. In further representative embodiments, the fluid reservoir can be operatively assembled, such as, for example, through the use of blow molding techniques or the like, as is known in the art. The fluid reservoir can be connected to a filtering system to provide chilled filtered liquid. The fluid reservoir and/or filtration systems can be associated with an appliance, such as a refrigerator. hi one aspect, the fluid reservoirs of the present disclosure can have a thin profile for convenient placement along and/or within the walls/floor/ceiling and/or mullions of an appliance. This thin profile is consistent both with very good thermal exchange and flow with little or no dead volume. The fluid reservoir can be placed in thermal contact with the cooling compartment. Due to the thermal contact, liquid delivered from the fluid reservoir can be chilled, and the configuration provides for good chilling efficiency. Fluid Reservoir design of the present disclosure combine some of the advantages of a coil tube fluid reservoir with those of a tank-style fluid reservoir, while eliminating many of the drawbacks associated with either the coil tube fluid reservoir or the tank-style fluid reservoir. In another aspect, the fluid reservoirs of the present disclosure can be designed and fabricated to yield desirable flow properties through the fluid reservoir so as to provide for a fully swept area with little or no dead volume, while at the same time possessing a wider flow area than a tube tank or the like, as would be understood by those skilled in the art. More specifically, representative fluid reservoirs of the present disclosure can be fabricated to have desirable cross-sectional configurations wherein the fluid reservoir conduit comprises a Reynolds number of about 800 to about 2500 at a flow rate of about 0.50 gallons per minute, in other representative embodiments the fluid reservoir can comprise a Reynolds number from about 1000 to about 2000 at a flow rate of about 0.50 gallons per minute, and in further representative embodiments the fluid reservoir can comprise a Reynolds number from about 1300 to about 1900 at a flow rate of about 0.50 gallons per minute. Generally, presently preferred representative embodiments of fluid reservoirs of the present disclosure comprise an inlet, an outlet and an elongated passageway connecting the inlet and the outlet. In some presently contemplated representative embodiments, the elongated passageway has a serpentine shape in order to compactly configure the elongated passageway. The elongated shape and the corresponding length of the passageway generally comprises many times the diameter across the cross-section of the passageway providing for the desired fluid storage volume while having little or no dead volume with first in-first out flow. In some representative embodiments, the passageway is operatively assembled, such as, for example, from two contoured sheets of material that are then operatively joined together by appropriate methods known in the art. The contoured sheets can be operatively formed from a generally rigid material, such as, for example, a plastic that maintains the shape of the contour to form flow channels with a selected shape. A seam between the sheets separates adjacent sections of passageway. In some representative embodiments, one sheet can comprise a generally planar surface wherein the generally planar sheet and a contoured sheet can be operatively connected to form the flow passages. In other presently contemplated representative embodiments, the top and/or bottom sheets of the fluid reservoir can be operatively formed from a flexible material, such as, for example, from a flexible polymer or other resilient material that is capable of performing the required function, as would be understood by those skilled in the art. hi these flexible representative embodiments, the shape of the flow channel can result from the fluid pressure within the flow channels. Generally, the flow channel configuration with fluid present in the channel is, presently preferably, roughly circular with some distortion near the seam, although the thickness of the flow channel walls can be varied radially along the cross-section of the flow channel so that the flow channel configuration expands to a different shape upon exposure to the fluid pressure, if desired. In some presently preferred representative embodiments based on contoured rigid materials, fluid reservoirs of the present disclosure can have a generally planar expanse with a thickness no more than, presently preferably, about 10 percent of the longest edge-to-edge distance across the generally planar surface of the fluid reservoir, in other representative embodiments no more than about 5 percent and in further representative embodiments from about 0.2 percent to about 3 percent of the longest edge-to-edge distance. If both surfaces are contoured, the planar projection of the surface with the greatest area can be used for evaluating distances across the surface. The elongated passageway, presently preferably, generally has a length at least a factor of three times the longest edge-to-edge distance across the planar surface. More details of suitable cross-sectional properties of the passageway with respect to rigid materials are described below. For some presently contemplated representative embodiments based on flexible polymers, the shape of the fluid reservoir can be similarly evaluated in the expanded form with fluid pressure within the fluid reservoir. In the expanded form, the fluid reservoir would generally have comparable dimensions as the fluid reservoirs formed with contoured rigid materials as described herein. While the flexible materials may be somewhat elastic such that the shape can vary depending on the pressure, the difference in shape generally is not significant over the range of standard residential water pressures. For evaluating the shape and properties of a flexible fluid reservoir as described herein, the fluid reservoir flow channels are subjected to a pressure that supplies a fluid flow rate of about 0.5 gallon per minute. Suitable dimensions for providing desired flow properties are described. Also, for mounting in a desired location, a flexible fluid reservoir can be bent providing that the flow channel is not blocked. However, it is to be noted that the dimensions and other properties of the fluid reservoir are evaluated in the flat configuration for convenience and definitiveness. hi some presently contemplated representative embodiments, the fluid reservoirs of the present disclosure can operatively interface with an appropriate dispenser. Generally, operation of the dispenser can be triggered by a user requesting a desired amount of fluid such as, for example, water, hi some presently contemplated representative embodiments, water can be dispensed through a dispenser in an appliance door such as, for example, a refrigerator door, hi some alternative representative embodiments, the dispenser can be located internal to an appliance such as, for example, within a refrigerated compartment of a refrigerator, as described further in copending U.S. Provisional Application No. 60/537,781 to Meuleners et al, entitled "WATER FILTER AND DISPENSER ASSEMBLY," the disclosure of which is herein incorporated by reference to the extent not inconsistent with the present disclosure. Placement and orientation of the fluid reservoirs of the present disclosure within an appliance can allow for practical considerations during installation as well as providing effective venting of air that may be contained within a fluid filtration system and/or the fluid reservoir itself prior to connection to a fluid supply. Fluid reservoirs of the present disclosure can have flow passage cross-sections selected to be small enough as to allow air to be pushed out of the flow passage due to the surface tension of the fluid regardless of the fluid reservoir orientation. In another aspect, representative fluid reservoirs of the present disclosure can be connected to a filtration system. For example, water from a city water supply, well or other water supply into a house or other structure can be filtered prior to being dispensed to the user. Generally, the fluid reservoir can be operatively positioned either upstream or downstream from the filtration system. If placed upstream, the fluid reservoir would then contain water or other liquid along with any anti-microbial agents, such as chlorine, found in the water/liquid supply, although these agents may be removed from the liquid by subsequent filtration prior to being dispensed. Thus, proliferation of microbes, such as bacteria or molds, may be inhibited prior to use and/or consumption by the user. Examples of representative filtration systems having a water fluid reservoir upstream from a filtration system are described further in copending U.S. Patent Application No. 10/445,372 to Fritze et al., entitled, "WATER FILTER ASSEMBLY," filed on May 23, 2003 and claiming priority to U.S. Provisional Application 60/383,187, filed on May 23, 2002, the disclosure of each is herein incorporated herein by reference to the extent not inconsistent with the present disclosure. When the fluid reservoir is placed upstream from a filter system and the fluid reservoir is located between two valves, the fluid reservoir can be subjected to constant or intermittent house line pressure. Alternative representative configurations providing relatively more flexibility and versatility with respect to placement of the filtration system can be realized when fluid reservoirs of the present disclosure are located downstream from a water filtration system. In some representative presently contemplated embodiments, the water filtration system can be located externally of a refrigeration unit, such that the potential for water flow blockage due to complete or partial liquid freezing within the filtration system, and more specifically internal of the filter element itself, is effectively, if not completely, eliminated, hi these representative embodiments, the fluid reservoir can be subjected to intermittent fluid line pressure, if located between two valves, or the fluid reservoir can be always at lower pressures than line pressure by exposure to an open line to atmosphere, for example, as described in copending U.S. Patent Publication No. 2005/0103721A1 to Fritze, entitled, "Reduced Pressure Water Filtration System," file September 23, 2004 and claiming priority to United States Provisional Application 60/505,152, filed September 23, 2003, the disclosure of each is herein incorporated herein by reference to the extent not inconsistent with the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of one possible representative fluid reservoir, in accordance with the present disclosure, having a serpentine flow passage with a cross- sectional area larger than a cross-sectional area of an inlet port and an outlet port. Figure 2 is an end view of the representative fluid reservoir of Figure 1. Figure 3 is a top view of the representative fluid reservoir of Figure 1. Figure 4 is a section view of the representative fluid reservoir of Figure 1 taken at line 4-4 of Figure 3. Figure 5 is a detail view of the representative fluid reservoir of Figure 1 taken at detail 5 of Figure 4. Figure 6 is a bottom perspective view of one possible representative embodiment of a fluid reservoir having a serpentine flow passage with a cross-sectional area larger than a cross-sectional area of an inlet port and an outlet port. Figure 7 is a top perspective view of the representative fluid reservoir of Figure 6. Figure 8 is a side view of the representative fluid reservoir of Figure 6. Figure 9 is a side view of the representative fluid reservoir of Figure 6 depicting an inlet port and an outlet port. Figure 10 is a top view of one possible representative embodiment of a fluid reservoir having a serpentine flow passage with a cross-sectional area equal to a cross-sectional area of an inlet port and an outlet port. Figure 11 is a bottom view of the representative fluid reservoir of Figure 10. Figure 12 is a side view of the representative fluid reservoir of Figure 10. Figure 13 is a bottom view of one possible representative embodiment of a fluid reservoir having a constant cross-sectional area for a serpentine flow passage, an inlet port and an outlet port. Figure 14 is a top view of the representative fluid reservoir of Figure 13. Figure 15 is a side view of the representative fluid reservoir of Figure 13. Figure 16 is an exploded, perspective view of one possible representative embodiment of a fluid reservoir having tube fittings integral to an inlet port and an outlet port. Figure 17 is a detail exploded, perspective view of the inlet port and the outlet port of the representative fluid reservoir of Figure 16. Figure 18 is a bottom view of one possible representative embodiment of a flexible fluid reservoir having a serpentine flow passage with a cross-sectional area larger than a cross-sectional area of an inlet port and an outlet port. Figure 19 it a detail bottom view of the inlet port and the outlet port of the representative flexible fluid reservoir of Figure 18. Figure 20 is a bottom view of one possible representative embodiment of a flexible fluid reservoir having an integral inlet port and an integral outlet port oriented generally perpendicular to the plane of the flexible fluid reservoir. Figure 21 is a bottom view of the representative flexible fluid reservoir of Figure 20. Figure 22 is a section view of possible representative flow channels for use with representative embodiments of either a rigid fluid reservoir or a flexible fluid reservoir. Figure 23 is a section view of possible representative flow channels for use with representative embodiments of either a rigid fluid reservoir or a flexible fluid reservoir. Figure 24 is a section view of possible representative flow channels for use with representative embodiments of either a rigid fluid reservoir or a flexible fluid reservoir. Figure 25 is a section view of possible representative flow channels for use with representative embodiments of either a rigid fluid reservoir or a flexible fluid reservoir. Figure 26 is a graph of Reynolds numbers for possible representative flow channel diameters suitable for use in household fluid flow applications.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS Improved fluid reservoirs described herein combine features of coiled tubes and tank fluid reservoirs to achieve desirable features of both types while exhibiting fewer drawbacks that are representative of each. New, improved, desirable processing approaches have made these previously commercially impractical fluid reservoirs practical on a commercial scale. In some presently preferred representative embodiments, the fluid reservoirs are designed to have flow that provides first in-first out flow without low flow or dead volume areas that can lead to stale liquid. At the same time, some presently preferred representative embodiments of fluid reservoirs can have a larger flow passage cross section than conventional coiled tubes so that less material is used and the pressure drop is less for a given tank volume, hi some representative embodiments, the fluid reservoirs are in the form of a monolithic structure with a curved flow path and adjacent flow channels separated with a seam or the like. The monolithic structures can be formed through a molding process or through the joining of two or more sheets of material. The improved fluid reservoirs can be incorporated into a filtration system and/or within an appliance, such as a refrigerator, to supply cooled water. hi some representative embodiments, the fluid reservoirs described herein involve a monolithic polymer structure with two ports and a flow passage between the ports. The flow passage can form a circuitous passage. Seams formed within the polymer structure can establish boundaries between adjacent sections of the flow passage. In some representative embodiments, the flow passage has an approximately constant diameter over most of the passage relating to contours of a material to establish desired flow properties through the passage. With respect to monolithic structures formed from rigid materials, the flow passages correspond with contours of the rigid material. In other representative embodiments, the flow passage corresponds to expandable sections of flexible materials with seams forming boundaries of the flow passage. The overall monolithic structure can have a generally planar aspect with at least one contoured surface forming the flow passage. Furthermore, the structure can be attached to a filtration system via appropriate fluid connections such as, for example, tubing fittings or other suitable connection methods known to one of skill in the art. The fluid reservoir with or without a filtration system can be mounted within an appliance, such as a refrigerator, and/or the fluid reservoir can be connected to a household water supply. In some representative embodiments, fluid reservoirs can be incorporated into an appliance having a liquid supply fluidly connected to a flow passage defined within the fluid reservoir. Fluid reservoirs can be fabricated such that the flow passage has a Reynolds number from about 800 to about 2500 at a flow rate of about 0.5 gallons per minute. In addition to having advantageous flow characteristics, the fluid reservoir of the present disclosure can simultaneously serve a dual function as a heat exchanger where the fluid reservoir can be positioned within an appliance wall, mullion or partition so as to be in thermal contact with a refrigeration compartment allowing for cooling of the fluid as it flows through and/or resides within the flow passage. The flow rate of 0.5 gallons per minute is specified for evaluation purposes, although the liquid fluid reservoir can be used at alternative flow rates. In some representative embodiments, a monolithic fluid reservoir structure can be formed by bonding two generally rigid polymeric sheets, wherein at least one sheet is contoured. When joined, the contour defines a flow passage between two ports in the resulting monolithic fluid reservoir structure. The bonding of the two sheets can be accomplished with a variety of fabrication methods such as, for example, using sonic welding, heat bonding, RF bonding or adhesive bonding, or any other connecting means that is capable of effectively accomplishing the intended function. The contour can be formed, such as, for example, by vacuum forming and/or pressure forming. In other representative embodiments, the contouring of at least one of the sheets and the bonding of the sheets is accomplished without requiring repositioning of the sheets between fabrication steps. In other representative embodiments, a monolithic fluid reservoir can be formed by joining a first flexible polymer surface to an adjacent flexible polymer surface so as to define a continuous flow channel fluidly interconnecting at least two flow ports. The adjacent flexible polymer surfaces can be arranged for bonding by stacking two flexible polymer sheets, or by folding a single polymer sheet to form the first flexible polymer surface and the second flexible polymer surface. The adjacent flexible polymer surfaces can be operatively attached using a suitable bonding process such as, for example, using sonic welding, heat bonding, RF bonding or adhesive bonding or any other connecting means that is capable of effectively accomplishing the intended function. Through the use of adjacent flexible polymer surfaces, the monolithic fluid reservoir structure can be inherently flexible allowing for ease of installation and assembly when used with an appliance. As illustrated in Figures 1-5, a presently preferred representative embodiment of a fluid reservoir 100 can comprise a monolithic structure with a flow channel 102 operably, fluidly interconnecting a flow inlet 104 and a flow outlet 106. Flow channel 102 comprises a generally serpentine flow arrangement defined by a plurality of flow legs 108 operably interconnected through a plurality of left hand bends 110 and a plurality of right hand bends 112. hi this representative embodiment, the bends are round, although other shapes of the bends can yield suitable flow properties. While other passage configurations can be used for flow channel 102, the generally serpentine structure provides for compact placement of the extended passages while providing for little or no dead volume, large overall volumes and high surface areas for thermal exchange. Fluid reservoir 100 comprises a fluid reservoir body 114 providing a generally rigid structure to fluid reservoir 100 so as to assist in manufacturing, storing, handling and installing fluid reservoir 100 within a fluid circuit. Fluid reservoir body 114 can comprise a handling portion 116 and a plurality of seams 118. Handling portion 116 provides for a convenient grasping or handling location during fabrication and/or installation of the fluid reservoir 100. Seams 118 can provide for interconnection and attachment of adjacent flow legs 108 to provide strength and rigidity to fluid reservoir 100. Seams 118 are fluid-tight so as to prevent flow directly between adjacent flow legs 108 but instead forcing flow to sequentially, serpentine through the flow channel 102. As illustrated in Figures 1 and 3, flow channel 102 forms a generally serpentine passage that involves bends back on itself. In contrast with coiled tubes, the flow channel resides substantially within the same plane and does not cross or double-up itself. However, if desired, the monolithic structure can comprise a flow channel that crosses or doubles up on itself while having flow with desired properties such as, for example, little or no dead volume, large overall volumes and high surface areas for thermal exchange. Nevertheless, flow channels that cross themselves are not presently preferred since they generally involve more complex processing approaches and can present complications for mounting due to the increased thickness at the crossing point. The serpentine passage can be configured to have any of a range of structures with a plurality of segments that may or may not have the same lengths and the number of segments can be selected to yield a desired volume consistent with the footprint of the structure for mounting. As illustrated in Figures 2 and 4, seams 118 can be arranged in a substantially planar orientation defining a medial plane 120 residing substantially parallel to and between a top surface 122 and a bottom surface 124 in which said top and bottom surfaces are generally defined by the flow channel 102. In other words, the flow channel corresponds with the contours of the monolithic structure. It should be noted that the designation of top and bottom surfaces throughout the disclosure is for convenience and ease of understanding and may not relate to the mounting orientation of fluid reservoir 100 during use. Fluid reservoir 100 as well as other representative embodiments of the fluid reservoir described herein can be formed from one or more appropriate materials, as described below. Generally, it is desirable to form fluid reservoir 100 from a polymer, although metals including blends thereof can be suitable. Selection of an suitable material, such as, for example, polymer may be based on a variety of factors such as, for example, cost, processing ability, durability and compatibility with potable liquids. Suitable polymers include, but are not limited to, for example, polyolefϊns, such as polyethylene, polypropylene, and polyethylene copolymers, Dowlex®, polyurethane, polystyrene, nylons (polyamides), and polyesters (such as polyethylene terephthalate, including, for example, Mylar®). The particular molecular weights of the polymers and particular formulations can be selected by methods known to those skilled in the art. hi some instance, polymers can be selected that possess either rigid, semi-rigid or flexible characteristics based upon the manufacturing methods employed and the desired physical or installation characteristics of the fluid reservoir such as, for example, wall thickness and overall dimensions. With respect to rigid materials, suitable metals including blends thereof, such as, for example, stainless steel, can be used in place of polymers. Suitable fittings can be incorporated into the flow inlet 104 and flow outlet 106 for connection of the fluid reservoir to piping, tubing or the like. Fittings can be selected to be compatible with respect to process and composition with the material of fluid reservoir 100 and the material of the tubing connecting fluid reservoir 100 to an associated fluid system. In particular, if crosslinked polyethylene or PEX tubing (genetically referring to either PEX-a, PEX-b or PEX-c tubing) is used, a fitting that mechanically grips the tubing is desirable since the crosslinked nature of the polymer in the tubing is not conducive to thermal or sonic welding. However, an adhesive can also be used to fix the tubing at the flow inlet 104 and flow outlet 106. Other materials can be selected to provide for thermal or sonic welding. While the polymers used to form the fluid reservoir 100 may or may not be initially crosslinked, the polymer can be further crosslinked following the forming process. In general, physical process such as, for example, an electron beam as used to crosslink PEX-c, ultraviolet radiation and/or a corona discharge as well as other physical processes, including, but not limited to, for example, other processes known in the art, can be used to perform the crosslinking. hi some representative embodiments, chemical crosslinking agents such as, for example, liquid peroxide used to crosslink and form PEX-a with the Engel method, as well as catalysts and/or exposure to air and moisture can trigger crosslinking of the polymer such as, for example, the use of a tin catalyst and moisture curing (water bath or steam sauna) in silane crosslinking technology to crosslink and form PEX-b. While polymers are convenient, cost effective and efficient materials for forming fluid reservoirs, many polymers have low thermal conductivity. The thermal conductivity of selected polymers can be increased by loading the polymer with a material with increased thermal conductivity. Suitable thermally conductive materials include, but are not limited to, for example, particles/powders of metal, such as copper flakes, aluminum and/or iron powders, and/or carbon particles, such as carbon black and/or graphite and any other materials capable of performing the intended function in the intended environment. The particles can have any reasonable shape and size that results in suitable mechanical properties of the resulting composite. For some representative embodiments, the loading of the particles can be no more than about 40 weight percent and in other representative embodiments from about 2 weight percent to 35 weight percent. A person of skill in the art will recognize that additional ranges within the above specified ranges of particle loading are contemplated by the present disclosure. With respect to the description herein of sheets or the like, such references can refer to laminates comprising a plurality of layers that may or may not have different compositions from each other. Another representative embodiment of a fluid reservoir 200 based on rigid materials is shown in Figures 6-9. Fluid reservoir 200 can comprise a monolithic rigid body 202 having a bottom surface 204 which, can be a generally flat, planar surface while a top surface 206 can be contoured to form a fluid flow passage 208 between fluid inlet 210 and fluid outlet 212. Rigid body 202 can comprise similar materials and be manufactured using similar fabrication techniques, as well as other manufacturing processes known to one skilled in the art, as previously described with respect to fluid reservoir 100. While being generally planar, bottom surface 204 can be partially contoured to form fluid inlet 210 and fluid outlet 212 as illustrated in Figure 7. In this representative embodiment, fluid flow passage 208 has a serpentine shape with eleven 180-degree bends 214 and two 90-degree bends 216 for connection to fluid inlet 210 and fluid outlet 212. Though described as fluid inlet 210 and fluid outlet 212, it will be understood that either port can be used interchangeably as the fluid inlet 210 and fluid outlet 212 based upon ease of orientation and installation of fluid reservoir 100. As illustrated in Figures 6 and 7, inlet tubing 218 and outlet tubing 220 can be secured at fluid inlet 210 and fluid outlet 212 to provide for flow into and out of the fluid reservoir 100. If formed from appropriate materials, inlet tubing 218 and outlet tubing 220 can be welded to fluid inlet 210 and fluid outlet 212, although other bonding approaches can be used, such as adhesive bonding, heat bonding, mechanical gripping and the like. Other positions of fluid inlet 210 and fluid outlet 212 along either bottom surface 204 or top surface 206 can be used, and, in particular, it will be understood that fluid inlet 210 and fluid outlet 212 need not be positioned next to each other. When fluid reservoir 200 is positioned and mounted in an appliance such as, for example, within an appliance wall, mullion or partition as described in United States Patent Application No. 10/975,193 to Meuleners et al., filed October 28, 2004 and entitled, "IMPROVED DESIGNS FOR FILTRATION SYSTEMS WITHIN APPLIANCES", which is herein incorporated by reference to the extent not inconsistent with the present disclosure, or in a refrigerated portion of an appliance, generally flat bottom surface 204 can be placed directly against an appliance wall to maximize the amount of physical contact between the fluid reservoir 200 and the appliance so as to increase overall heat transfer between the appliance and fluid reservoir 200, which can ultimately chill the fluid in fluid flow passage 208 prior to use and consumption of the fluid. An alternative variation on fluid reservoir 200 is illustrated as a fluid reservoir 250 in Figures 10, 11 and 12. Fluid reservoir 250 can substantially resemble fluid reservoir 200 with the inclusion of similar features such as, for example, rigid body 202 having generally flat bottom surface 204 and contoured top surface 206. Fluid reservoir 250 can further comprise fluid flow passage 208 having effectively 180-degree bends 214 and effectively 90- degree bends 216. Of course, suitable designs can incorporate bends with other angles. Fluid reservoir 250 can differ from fluid reservoir 200 in that a fluid inlet 252 and fluid outlet 254 each have a cross-sectional area that is substantially, approximately constant from fluid inlet 252 to fluid outlet 254 including the fluid flow passage 208. hi contrast, fluid flow passage 208 as illustrated in Figures 6, 7, 8 and 9 flares out to a larger cross-sectional area between fluid inlet 210 and fluid outlet 212. Fluid reservoir 250 can comprise similar materials and be manufactured using similar fabrication processes as previously described with respect to the previously discussed representative embodiment of fluid reservoir 100. Another representative, alternative embodiment of a fluid reservoir 300 based on the selection and fabrication of rigid materials is illustrated in Figures 13, 14, 15, 16 and 17. hi this representative embodiment, fluid reservoir 300 can comprise a fluid reservoir body 302 having both a contoured top surface 304 and a contoured bottom surface 306 to form a fluid flow passage 308 between a fluid inlet 310 and a fluid outlet 312. Thus, fluid reservoir 300 comprises a flow passage cross-section that is generally symmetric through a central plane 314 of the fluid reservoir body 302, although alternative representative embodiments can have asymmetric contoured surfaces. As depicted, fluid flow passage 308 has a generally uniform cross-section between fluid inlet 310 and fluid outlet 312, though it will be understood that the cross-section of fluid flow passage 308 could alternatively be larger than similar cross-sections of fluid inlet 310 and fluid outlet 312 depending upon design considerations such as, for example, fluid flow rate, desired fluid reservoir storage capacity, desired fluid velocities within fluid flow passage 308 and overall heat transfer properties of fluid reservoir 300. Fluid flow passage 308 comprises a generally serpentine configuration with fifteen 180-degree bends 314 and two 90-degree bends 316. Referring to the exploded views of fluid reservoir 300 illustrated in Figures 16 and 17, appropriate tube fittings 318 can be secured into fluid inlet 310 and fluid outlet 312 to facilitate connection to and gripping of inlet tubing 320 and outlet tubing 322. Tube fittings 318 can comprise any of a variety of suitable tube fitting known one skilled in the art such as, for example, push-style tube fittings available from a variety of manufacturers including John Guest International, Ltd., of Middlesex, United Kingdom, or barb-less style tubing fittings such as, for example, those described in copending U.S. Patent Publication No. 2004/0201212A1 filed on April 11, 2003, to Marks, entitled, "Plastic Tube Joint." Tube fittings 318 can be appropriately secured within fluid inlet 310 and fluid inlet 312 through the use of suitable attachment methods such as, for example, integral molding, adhesive bonding and or thermal and sonic welding methods. Tube fittings 318 can be used to securely hold inlet tubing 320 and outlet tubing 322 formed from a tubing material that does not easily directly bond to the heat exchanger material, such as highly crosslinked polymers. A representative embodiment of a flexible fluid reservoir 400 is illustrated in Figures 18 and 19. Flexible fluid reservoir 400 has a fluid reservoir body 402 having a primarily serpentine flow channel 404 between a fluid inlet 406 and a fluid outlet 408. Flow channel 404 is generally defined by eleven 180-degree bends 410 and two 90-degree bends 412. Welded seams or sections 414 mark the boundaries between adjacent sections of the flow channel 404. A perimeter seam 416 is provided near the outer edge of the fluid reservoir body 402 in the roughly planar structure of the un- inflated configuration illustrated in Figures 18 and 19. In this representative embodiment, the overall shape of fluid reservoir 400 is generally rectangular with an extension portion 418 at one corner to provide for fluid inlet 406 and fluid outlet 408, although any convenient shape generally can be used as appropriate. With reference to the detailed view illustrated in Figure 19, tubes 420 can be operably connected, for example by welding or adhesive bonding, to fluid inlet 406 and fluid outlet 408 for operably interconnecting flow channel 404 with a supply fluid source and an outlet point-of-use. As discussed with respect to previous representative embodiments, fluid reservoir 400 can be configured and fabricated to incorporate tubing connectors similarly welded and/or bonded into fluid inlet 406 and fluid outlet 408 for fluidly interconnecting flow channel 404 with a supply fluid source and an outlet point-of-use. Another representative, alternative embodiment of a flexible fluid reservoir 500 is illustrated in Figures 20 and 21. Flexible fluid reservoir 500 comprises a generally serpentine flow channel 502 fluidly interconnecting a fluid inlet 504 with a fluid outlet 506. Flow channel 502 is generally defined by eleven "squared" corners 508 at eleven 180-degree bends 510. Both fluid inlet 504 and fluid outlet 506 include an integral flow port 512 attached directly through a wall 514 of fluid reservoir 500 such that the integral flow ports 512 are generally perpendicular to a generally planar surface defined by wall 514. Integral flow ports 512 can be formed by welding and/or bonding a tubing connector, such as those previously described with respect to other fluid reservoir representative embodiments, into the fluid inlet 504 and fluid outlet 506. Thus, apart from having openings in fluid inlet 504 and fluid outlet 506 to connect with the integral flow ports 512, flow channel 502 is not otherwise shaped to form the integral flow ports 512, in contrast with the representative embodiment of flexible fluid reservoir 400 illustrated in Figures 18 and 19. In addition to the aforementioned and described fluid reservoirs, alternative representative fluid reservoir embodiments can be fabricated so as to comprise both rigid and flexible components in a single monolithic fluid reservoir. For example, a representative monolithic fluid reservoir can comprise a combination of monolithic rigid body 202 and fluid reservoir body 402 so as to fine a rigid first surface and a flexible second surface. A rigid first surface and a flexible second surface can be operably joined to define a continuous, serpentine fluid channel using suitable fabrication processes such as, for example, adhesive bonding, thermal welding and a variety of molding processes, as would be understood by those skilled in the art. The flow passageways associated with the various previously discussed fluid reservoirs can comprise a wide range of cross-sectional shapes and sizes. While these shapes can especially be applicable with respect to the fluid reservoirs formed with rigid materials such as, for example, fluid reservoir 100, fluid reservoir 200 and fluid reservoir 300, some of these cross-sectional shapes can also be formed for the flexible fluid reservoirs such as, for example, flexible fluid reservoir 400 and flexible fluid reservoir 500, in addition to roughly circular cross-sections by selectively varying the sheet thickness of the flexible fluid reservoir. Some representative examples of cross-sectional shapes are illustrated in Figures 22, 23, 24 and 25. Referring to Figure 22, these flow passages have a flat bottom 600 and a curved top 602 corresponding to fluid reservoir 200 and fluid reservoir 250 discussed previously with respect to Figures 6-12 above. Four contoured shapes are illustrated in Figure 22 as follows: stretched semi-circle 604, semi-circle 606, stretched ellipse 608 and ellipse 610. Referring to Figure 23, representative embodiments of the flow passage have a contoured top surface 620 and a contoured bottom surface 622. As illustrated in Figure 23, contoured top surface 620 and contoured bottom surface 622 share substantially the same contour which generally corresponds to the contours of Figures 1-5, 13-17 depicting fluid reservoir 100 and fluid reservoir 300 respectfully. The respective top and bottom shapes illustrated in Figure 23 are as follows: stretched semi-circle 624, semicircle 626, stretched ellipse 628 and ellipse 630. Alternatively, contoured top surface 620 and contoured bottom surface 622 can comprise different contours such as, for example, contoured top surface 620 comprising stretched semi-circle 624 while contoured bottom surface 622 comprises ellipse 630. Alternative representative embodiments of cross-sectional shapes and sizes for increasing surface area and thermal transfer efficiency of fluid passages are illustrated in Figures 24 and 25. The flow passage illustrated in Figure 24 comprises a curved top surface 700 and a curved bottom surface 702. Curved bottom surface 702 can be contoured as shown in the various frames of Figures 24 and 25. Curved top surface 702 can be similarly arched to the configurations depicted for curved bottom surface 702, which can have advantages for certain flow applications such as, for example, inward dimples 703 of the contours of curved top surface 700 and curved bottom surface 702 can help to prevent rupture upon freezing through the outward bulging of the inward dimple 703 in response to expansion of freezing water. Depending upon the material selected for curved top surface 700 and curved bottom surface 702, the inward dimples 703 can reform upon release of the expansion pressure as frozen water melts to form a liquid. Various alternative cross-sectional shapes of the passage can be formed based on the representative examples illustrated in Figures 22, 23, 24 and 25. A particular shape can be selected to have desired heat exchange and fluid flow properties, as well as convenience for processing. In some presently preferred representative embodiments, the fluid reservoir can be formed as a single integral piece. For example, the fluid reservoir can be formed using blow molding. Blow molding is generally accomplishing by inflating a softened tube of polymer within a mold wherein the polymer expands against the mold walls thereby causing the polymer to assume the shape of the mold. The polymer is then cooled so as to retain this molded shape. However, in alternative processing approaches, the fluid reservoir can be formed from two sheets, for example, contoured top surface 304 and contoured bottom surface 306 as illustrated in Figure 16, that are bonded together. Thus, in these representative embodiments, there are two steps to the process, a contouring step for one or both sheets and a bonding step, although the steps may or may not be separated in time. Other additional steps can be used. The contouring can be performed, for example, using blow molding or pressure molding. In these approaches, a sheet of polymer is thermally softened and contoured on a form. In vacuum forming, softened sheets are sucked onto a male or female form, hi pressure molding, the softened sheet is blown onto the male or female form. A combination of suction and pressure can be used. The two sheets can be sealed together using sonic welding, heat welding/staking, radio-frequency RP heating/bonding, adhesive bonding or the like. Various tools for performing these bonding processes are known in the art. The contoured pieces are positioned and sealed. After bonding the sheets, the structure can be trimmed, smoothed or similarly finished. Manufacturing of representative fluid reservoirs of the present disclosure can be accomplished in a generally continuous and simultaneous twin sheet forming process with respect to the sheets being essentially positioned for bonding at the time of the contouring. In this twin sheet forming process, the sheets can be positioned together at the start of the process with one or two forms adjacent the appropriate sheet(s). The sheets can then be heated wherein the contouring step, accomplished with vacuum/suction, and the heat boding step are performed in combination. The precise timing of the bonding and contouring steps can be generally simultaneous. The significant feature of the twin sheet forming process is that the sheets are aligned one time for both the contouring and bonding of the sheets without requiring significant translation and repositioning of the sheets once the processing is underway. This improves reproducibility while making the processing more efficient. Furthermore, with a twin sheet forming process, the sheets can comprise a plurality of layers. In some representative embodiments, the layers can provide different functionalities to the composite sheet. For example, a layer can provide antimicrobial functionality, resist favor migration, limit oxygen migration, and/or increase thermal conductivity. The plurality of layers can be laminated together prior to performing the twin sheet forming process. When manufacturing flexible fluid reservoirs, the fluid reservoir structure can be formed, for example, from two sheets or from a single folded sheet, although more sheets can be used to form the fluid reservoir if the edges between the sheets are positioned along seems. The forming process involves the bonding of adjacent sheets to form the seams between flow channels. For many flexible polymers, the bonding can be performed with heat bonding or other thermal bonding process. However, adhesive bonds or other bonding processes can be similarly used to form the seams. In some representative embodiments, the cross-sectional area can be selected to yield desired flow properties for the fluid reservoir so as to provide for a continually swept area having little or no dead volume, but have a wider area than a tube tank or the like. In some representative embodiments of interest, the fluid reservoir can be manufacture to have a flow passageway with a Reynolds number of about 800 to about 2500 at a flow rate of about 0.50 gallons per minute, in other representative embodiments from about 1000 to about 2000, and in further representative embodiments from about 1300 to about 1900 at a flow rate of about 0.50 gallons per minute. The Reynolds number is a parameter that is related to the character of a fluid flow. It is defined as the product of the density, the velocity and a characteristic length divided by the viscosity. The flow rate of 0.50 gallons per minute is within standard ranges for household use and is a convenient reference point for evaluating the flow. The flow passages can be evaluated at a flow rate of 0.50 gallons per minute, although in actual use they may be used at different flow rates. These evaluations can be similarly performed for fluid reservoirs formed with rigid or flexible materials. Evaluation of the flow passages based on a selected flow is a convenient approach for evaluating the flow passages without reference to specifics of the cross-sectional shape. Calculated Reynolds numbers are tabulated in Table 1 below and

plotted in Figure 26 for various diameter tubes for water at a viscosity at 40 degrees F.

Table 1: Reynolds Numbers For Various Flow Passage Diameters Flow Rate Reynolds Numberatvarious diameters gpm 0.17" 0.23" 0.375" 0.5" 0.75" 1.0" 1.25" 1.5" 0.10 1203 889 545 409 273 204 164 136 0.20 2406 1778 1090 818 546 408 328 272 0.30 3609 2667 1635 1227 819 612 492 408 0.40 4812 3556 2180 1636 1092 816 656 544 0.50 6015 4445 2725 2045 1365 1020 820 680 0.60 7218 5334 3270 2454 1638 1224 984 816 0.70 8421 6223 3815 2863 1911 1428 1148 952 0.80 9624 7112 4360 3272 2184 1632 1312 1088 0.90 10827 8001 4905 3681 2457 1836 1476 1224 1.00 12030 8890 5450 4090 2730 2040 1640 1360 1.10 13233 9779 5995 4499 3003 2244 1804 1496 1.20 14436 10668 6540 4908 3276 2448 1968 1632 1.30 15639 11557 7085 5317 3549 2652 2132 1768 1.40 16842 12446 7630 5726 3822 2856 2296 1904 1.50 18045 13335 8175 6135 4095 3060 2460 2040 1.60 19248 14224 8720 6544 4368 3264 2624 2176 1.70 20451 15113 9265 6953 4641 3468 2788 2312 1.80 21654 16002 9810 7362 4914 3672 2952 2448 1.90 22857 16891 10355 7771 5187 3876 3116 2584 2.00 24060 17780 10900 8180 5460 4080 3280 2720

For comparison, at a flow rate of 0.5 gallons per minute, a standard commercial tank

with cross-sectional inner diameters of 1.25 to 1.5 inches have Reynolds numbers of about

680. Reynolds numbers for commercial tanks are calculated and listed in Table 1 in bold font

in the upper right-hand portion of the table. These tanks also can have un-swept volume and

thermal stratification resulting in mixing. Thus, these tanks generally do not have first-in-

first-out flow, which can result in undesirable properties with respect to taste and

contamination. However, tube tanks generally have Reynolds numbers above 4000 and are

calculated and listed in Table 1 in bold font in the lower left-hand portion of the table.

While tube tanks generally have first-in-first-out flow, these can have other undesirable

features relating to excessive surface area, for example, large pressure drops, high

manufacturing costs, and undesirable taste with respect to stored fluid. The designs described

herein overcome these issues through a fluid reservoir design that combines many of the

desirable features of the tank design and the coil tube design. For example, fluid reservoirs

can be specifically designed to have first-in- first-out flow similar to the coil tube design while

having engineered conduit cross-sections for increasing storage volume similar to the tank design, all while maintaining the Reynolds number within the range of about 680 to about 4000. The representative embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the inventive concepts herein. Although the present inventive concepts has been described with reference to particular representative embodiments, workers skilled in the art will recognize that a variety of changes, modifications and substitutions may be incorporated without departing from the spirit and scope of the concepts described herein and the present claimed in the present disclosure.