Abstract:
An improved dual-pressure dual-compartment tank for transferring heat energy between two solutions while physically isolating the solutions from each other is disclosed. The tank has one fluid compartment positioned within a second fluid compartment such that the transfer of heat energy between the compartments is facilitated. One of the compartments is structured to maintain a substantially higher pressure than the other compartment so that if a physical divider between the compartments were to fail, the lower pressure fluid would not contaminate the higher pressure fluid. Additionally, the divider may take a variety of shapes to improve fluid mixing by accelerating or decelerating the fluid, and/or to provide an amount of surface area between compartments that is inversely proportional to the local temperature gradient between the compartments. These designs may include shapes such as a cone, a corrugated cylinder, a corrugated cone, or a cone with an outer spiral for improving mixing, thermal transfer, or to simplify construction of the dual-compartment tank.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to devices, systems, and methods for providing hot water to a utility use and to a general residential or commercial use. More particularly, the invention relates to devices, systems, and methods in which potable water for human use is heated by placing it in proximity to a hot hydronics solution. 
       BACKGROUND 
       [0002]    Conventional potable hot water heaters are usually of the tank-type having an electric, gas or, other heating element at their bottom. A cold water source such as a well or municipal water supply provides water to the tank, and an outlet from the tank is connected to sinks, dishwashers, washing machines, bath tubs, or other devices that use hot water. 
         [0003]    Hydronic fluid storage and heating compartments are also generally of the tank-type and may be heated by a variety of fuels including natural gas, oil, coal, resistive electric heating, or high efficiency electrically powered heat pumps. Hydronic heating tanks are often connected to a pump that forces water from the tank to radiators that are placed in rooms for which heating is desired. 
         [0004]    Although hot hydronics fluid and hot potable water are both stored in tanks, hydronics fluid is usually stored separately from potable water systems due to the risk of chemicals, bacteria, or other substances contaminating the potable water supply. In addition to increasing heat losses, the use of separate hydronics and potable water tanks requires substantially more materials, such as insulation, for construction. 
         [0005]    Combination potable water and hydronics tanks have been described in publications such as U.S. Pat. Nos. 5,544,645 and 6,032,868. In such systems heated water is typically circulated between a hot water storage tank and a hydronics loop providing heated air to a space. Heated water in the tank is also used to satisfy a demand for domestic hot water (e.g., showers, laundry, dishwasher, etc.). These systems typically employ complex and difficult to construct systems for ensuring that the hydronics solution does not contaminate the potable water supply. 
         [0006]    Attempts have been made to overcome these inefficiencies by using a single burner or heat source for both domestic hot water and space heating requirements such as in U.S. Pat No. 5,074,464. When there is no demand for heated potable water, the water tank of the &#39;464 patent circulates water through a heat exchanger mounted in a blower to heat the air space rather than have the tank sit idle. 
         [0007]    French patent applications FR0607980 and FR00702831 claim to disclose a combined dual tank device for heating both a structure and sanitary hot water. To transfer heat from the sanitary water to the heat-transfer fluid, a first tank is arranged at least in part inside a second tank. 
         [0008]    Despite somewhat improved efficiencies of these dual compartment tanks, these systems substantially increase the complexity and cost of tank fabrication. These previous systems do not provide a tank with a section divider whose construction and design is simplified by using a pressure differential as a containment backup in the event of a tank separator rupture. Additionally, these previous systems do not sufficiently address the problem of temperature gradient stratification within isolated compartments. 
       SUMMARY OF THE INVENTION 
       [0009]    An improved dual-pressure dual-compartment tank for transferring heat energy between isolated solutions is disclosed. The tank has one fluid compartment positioned within a second fluid compartment so that the transfer of heat energy between the compartments is facilitated. One of the compartments is maintained at a substantially higher pressure than the other so that if a divider between the compartments ruptures, the low pressure fluid will not contaminate the high pressure fluid. Additionally, the divider may take a variety of shapes to improve fluid mixing within the compartments by accelerating or decelerating the fluid. Also, the divider may be shaped to provide an amount of surface area between compartments that is inversely proportional to the local temperature gradient between the compartments. These designs may include shapes such as cones, corrugated cylinders, corrugated cones, or cones with outer spirals. The foregoing summary does not limit the invention, which is defined by the claims. Similarly, neither the title nor the abstract is to be taken as limiting in any way the scope of the disclosed invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Each of the drawing figures now described shows an exemplary embodiment of the present invention. 
           [0011]      FIG. 1  is a side cross-sectional view of a dual compartment fluid tank with a cone shaped internal compartment and a cylinder shaped outer compartment. 
           [0012]      FIG. 2  is a top view of a dual compartment fluid tank with a cone shaped internal compartment. 
           [0013]      FIG. 3  is a perspective view of a dual compartment fluid tank with a cone shaped internal compartment. 
           [0014]      FIG. 4  is a side cross-sectional view of a dual compartment fluid tank with an extended cone shaped internal compartment. 
           [0015]      FIG. 5  is a perspective view of a dual compartment tank with a cone shaped internal compartment having a spiral agitation enhancer that improves mixing in the external compartment. 
           [0016]      FIG. 6  is a side cross-sectional view of a dual compartment tank with a cone shaped internal compartment having an external spiral mixing enhancer. 
           [0017]      FIG. 7  is a perspective view of a dual compartment tank with a cylinder shaped internal section. 
           [0018]      FIG. 8  is a side cross-sectional view of a dual compartment tank with a cylinder shaped internal partition. 
           [0019]      FIG. 9  is a perspective view of a dual compartment tank with a corrugated cylinder shaped internal chamber 
           [0020]      FIG. 10  is a side cross-sectional view of a dual compartment tank with a corrugated cylinder shaped internal compartment 
           [0021]      FIG. 11  is a perspective view of a dual compartment tank with a cone shaped internal compartment having a plurality of mixing features that promote mixing in the external compartment. 
           [0022]      FIG. 12  is a front view of a dual compartment water tank with a cone shaped internal compartment having a plurality of mixing features. 
           [0023]      FIG. 13  is a perspective view of a dual compartment water tank with a cone shaped internal compartment having features that promote mixing in both the external and internal compartments. 
           [0024]      FIG. 14  is a side view of a dual compartment water tank with a cone shaped internal compartment having agitating features that promote mixing within both the external and internal compartments. 
           [0025]      FIG. 15  is a perspective view of a dual compartment water tank with an internal compartment having a shape substantially defined by a fifth order polynomial. 
           [0026]      FIG. 16  is a side view of a dual compartment water tank with an internal compartment having a shape substantially defined by a fifth order polynomial. 
           [0027]      FIG. 17  is a perspective view of a dual compartment water tank with an internal compartment having non-symmetric corrugation. 
           [0028]      FIG. 18  is a side view of a dual compartment water tank with an internal compartment having non-symmetric corrugation. 
           [0029]      FIG. 19  is a perspective view of a dual compartment water tank with an internal compartment having a nested tapered shape. 
           [0030]      FIG. 20  is a side view of a dual compartment water tank with an internal compartment having a nested tapered shape. 
           [0031]      FIG. 21  is a perspective view of a dual compartment water tank with an internal compartment having a nested cone shape. 
           [0032]      FIG. 22  is a perspective view of a dual compartment water tank with an internal compartment having a tapered shape. 
           [0033]      FIG. 23   a  is a side view of a dual compartment tank with an internal compartment having a tapered shape. 
           [0034]      FIG. 23   b  is a chart showing the elevation dependence of the hydronics fluid upward velocity within the dual compartment tank shown in  FIG. 23   a.    
           [0035]      FIG. 24  is a perspective view of a dual compartment water tank with an internal compartment having an undulated shape. 
           [0036]      FIG. 25  is a side view of a dual compartment water tank with an internal compartment having an undulated shape. 
           [0037]      FIG. 26  is a perspective view of a dual compartment tank with agitators on the interior of the exterior compartment and on the exterior of the interior compartment. 
           [0038]      FIG. 27  is a side view of a dual compartment tank with agitators on the interior of the exterior compartment and on the exterior of the interior compartment. 
           [0039]      FIG. 28  is a perspective view of a dual compartment tank with an exterior compartment having a rectangular shape. 
           [0040]      FIG. 29  is a perspective view of a dual compartment tank with an exterior compartment having a rectangular shape and an interior compartment having a pyramidal shape. 
           [0041]      FIG. 30  is a side view of a dual compartment tank with an exterior compartment having a rectangular shape and an interior compartment having a pyramidal shape. 
           [0042]      FIG. 31  is a perspective view of a dual compartment tank with a water compartment that is almost completely surrounded by hydronics fluid within a hydronics compartment. 
           [0043]      FIG. 32  is a side view of a dual compartment tank with a water compartment that is almost completely surrounded by hydronics fluid within a hydronics compartment. 
           [0044]      FIG. 33  is a side view of a dual compartment tank system with valves adapted to isolate the potable water tank in the event of a catastrophic decrease in potable water pressure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0045]    The present invention may be used with any type of fluid heat exchange system and is particularly suited for preventing cross contamination of fluids that are in thermal communication with each other. However, for descriptive purposes, the present invention will be described in use with potable water and hydronics heating systems. 
         [0046]      FIG. 1  shows a side view of a dual compartment hydronics fluid and potable water tank  10 . A hydronics compartment  15  or vessel with a hydronics fluid input  20  and a hydronics fluid output  25  may be part of a larger circulation system providing heating to a structure via a plurality of conduits and radiators (not shown). Substantially enclosed within the hydronics compartment  15  is a potable water compartment  30  with a water input  35  and a water output  40 . In the embodiment shown in  FIG. 1 , potable water from a municipal or well source is fed into the water compartment via the water input. Thermal insulation  45  surrounds both of the compartments to reduce the amount of heat lost to the surrounding environment. A conical separator  50  between the hydronics compartment and the water compartment prevents hydronics fluid from contaminating the potable water supply while facilitating the transfer of heat energy from the hydronics solution or other utility fluid to the potable water. Another feature of the conical separator  50  is that it may be structured to exert a substantially greater pressure upon the potable water than the hydronics fluid. For example, structural reinforcements may be added to conical separator to help resist the outward pressure of the potable water.  FIG. 1  shows a relief valve  55  that releases fluid if the pressure in the hydronics compartment exceeds a threshold value. 
         [0047]    The exemplary fluid within the hydronics compartment is mostly liquid water and may also include amounts of other substances such as glycol, sodium titrate, water vapor, NOBURST® Hydronic System Cleaner, E-3 Defoaming Agent, and INHIBITOR BOOST. Other non-potable chemicals may also be added to the hydronics fluid to inhibit corrosion, prevent freezing of the water in the system, increase the boiling point of the water in the system, inhibit the growth of mold and bacteria, and allow for improved leak detection (for example, dyes that fluoresce under ultraviolet light). 
         [0048]    In  FIG. 1 , potable water is provided to the dual compartment at a temperature below the commonly acceptable range for applications such as laundry, dish washing, baths, and showers. The water enters the potable water compartment at a location below the potable water output where the cross-sectional circumference and surface area of the conical separator are relatively small. As a result of the smaller cross section and the substantial temperature difference between the hydronics fluid and the potable water, there is a substantial heat gradient across the conical separator. The large gradient causes heat energy to rapidly flow from the hydronics compartment to the potable water compartment, and depending on flow conditions, may result in a local low temperature region in the hydronics compartment. 
         [0049]    As a water portion continues to flow through the potable water compartment, it moves upwards towards the output where the cross-sectional circumference of the tank is larger relative to the lower portions. As the potable water rises, its temperature increases and the temperature gradient between hydronics and potable fluid decreases. However, the increased surface area of the conical separator at higher elevations helps to maintain the rate of thermal transfer from the hydronics compartment by offsetting the decreased temperature gradient. Additionally, due to the increased circumference, the average upward flow velocity of the water is slower than at lower elevations resulting in an increased chance for thermal mixing. 
         [0050]    In addition to helping to maintain a consistent elevation based thermal transfer between the two compartments in the tank, the conical shape of the separator assists in physically mixing of both the hydronics fluid and the potable water. At lower elevations, the horizontal cross sectional areas of the hydronics compartment are relatively large, but they decrease with elevation. Since the input and output flows of hydronics solution are substantially equal, the average upward speed of hydronics fluid increases at higher elevations as the horizontal flow cross sectional area decreases. The upward acceleration of the fluid results in turbulence that produces additional mixing. Similarly, the conically shaped separator assists in mixing the potable water. 
         [0051]    The cone shape separator forms the interior vessel such that the diameter of the potable water vessel is greater at higher elevations. A larger horizontal diameter results in the horizontal cross sectional area of the interior vessel horizontal cross-section being larger. Due to the flow rate of potable water into and out of the dual compartment tank being substantially equal, the larger area causes the upward velocity of the potable water through the compartment to decrease with elevation that results in mixing. 
         [0052]    The conical separator, or thermally conductive divider, is preferably constructed from a single sheet of material rolled in to a substantially cone shape and sealed along a single linear seam. By minimizing the number of connections and seems in the separator, the likelihood of a seam rupture is decreased over the lifetime of the water storage tank (possibly 20 years or more). Alternatively, in order to simplify construction of the conical separator, two substantially symmetrical half cone sections may be joined together in with two seams. 
         [0053]    The conical separator  50  is preferably made from thermally conductive materials such as copper (380 W/mk thermal conductivity), aluminum (200 W/mk), silver, (429 W/mk), type 304, 316 or 302 stainless steel (16.2 W/mk), type 410 stainless steel (24.9 W/mk), or CoolPoly® E5101 Thermally Conductive Polyphenylene Sulfide (20 W/mk). 
         [0054]    In the event of a catastrophic separator failure, the higher pressure potable water (˜60 PSI) would flow into the hydronics compartment (˜6-15 PSI) while preventing backflow contamination of the potable water. Since the water compartment is continuously fed from a source such as a well or a municipal water supply, the amount of water in the water compartment will remain constant despite the rupture in the separator. Water flowing into the hydronics compartment would raise the pressure of the hydronics fluid to substantially above the standard hydronics operating pressure. The hydronics compartment is equipped with a pressure release valve that will release fluid once the pressure exceeds a threshold level. The threshold level is set between the standard operating pressure of the water and hydronics compartments. The release of fluid via the relief valve prevents the pressure in the hydronics compartment from equalizing with the pressure in the water compartment. Thus the outflow of water would be continuous after the threshold pressure has been reached, and backflow contamination of the potable water compartment would be prevented. In an exemplary embodiment of the invention the pressure release valve is a 30 PSI ASME certified pressure valve. In another exemplary embodiment, during operation of the pressure release valve an audible banging sound is created as the valve relieves the pressure inside of the hydronics compartment. 
         [0055]    In  FIG. 1 , the hydronics compartment forms the outer vessel of the dual-pressure dual compartment tank, however in alternate embodiments the hydronics compartment could be with the water compartment. In  FIG. 1 , the fluids within each compartment flow upwards, however downward flows could also be utilized. Similarly, the cone shown in  FIG. 1  tapers downwards, but an upwardly tapering cone is also within the scope of the invention. 
         [0056]      FIG. 2  shows a horizontal cross-section of a dual compartment water tank with a cylindrical structure. Although a cylinder is an exemplary structure, other shapes such as rectangular are within the scope of the invention. 
         [0057]      FIGS. 3 and 4  illustrate another exemplary embodiment of the invention with a conical separator  50 , a nadir input  60  for the potable water, and a plurality of hydronic fluid outputs  25  to provide hydronics fluid to multiple regions of a hydronics system. Also included is a thermometer port  65  for accessing a temperature measurement device. By inputting the water at the lowest possible region of the potable water compartment, the minimum distance traveled by the water is maximized. To facilitate the process of connecting the dual compartment tank to a potable water supply, the exemplary water tank has a side pipe  70  that extends horizontally from the nadir input to the dual compartment tank exterior. 
         [0058]      FIGS. 5 and 6  show another exemplary embodiment of the invention that includes a flow spiral  75  spiraling around the conical separator  50 . The flow spiral acts to increase the turbulence within the hydronics compartment and reduces the temperature variation within the hydronics compartment. In order to increase the longevity of the conical separator, the flow spiral may be added after the conical separator has been manufactured from a single material sheet. In an exemplary embodiment of the invention, the flow spiral is secured to the conical separator by an adhesive that does not reduce the structural integrity of the conical separator. 
         [0059]      FIGS. 7 and 8  show an example of a dual compartment tank with a cylindrical separator  80  between the hydronics vessel and the potable water vessel. A cylindrical shape further simplifies manufacture of the compartment. 
         [0060]      FIGS. 9 and 10  show an example of a corrugated separator  85  between the hydronics and potable water compartments. The corrugation of the separator acts to improve mixing by providing small regions of vertical fluid deceleration  90  and small regions of vertical fluid acceleration  95 . As with the conical separator, the small regions of deceleration have a horizontal cross section that increases in area with rises in elevation. Since the fluid input to the potable water compartment is essentially equal to the output, increases in cross sectional area cause a decrease in the vertical rise of the potable water resulting in turbulence. Similarly, the vertical speed of the fluid increases with elevation in the small areas of vertical acceleration. 
         [0061]      FIGS. 11 and 12  illustrate an example of a dual compartment tank with concentric agitators  100  in the hydronics compartment. The concentric agitators function similarly to the flow spiral in that they increase turbulence. In this example, the conical separator is formed by rolling two sheets of stainless steel into symmetrical half-cone sections that are welded together with two linear seams. Like the flow spiral, the concentric agitators may be attached after the separator has been fabricated. Placement of the concentric agitators may be simplified during the manufacturing process by inverting the conical separator and securing agitators of decreasing circumference onto the separator. After the agitators have been secured to the conical separator, the completed assembly may be un-inverted and placed into the hydronics compartment of the tank. 
         [0062]      FIGS. 13 and 14  illustrate an example of a dual compartment tank with flow agitating inner rings  105  and flow agitating outer rings  110 . The outer rings  110  may be attached to the conical separator in a manner similar to the concentric agitators. Since the inner rings are to be submerged in potable water for the lifetime of the dual compartment tank, the inner rings are preferably constructed of and secured with substances that are certified safe for contact with potable water. 
         [0063]      FIGS. 15 and 16  illustrate a dual compartment tank with a conical corrugated separator  115 . The conical corrugated separator directs the flow of water through a path similar to the conical separator of  FIG. 1  while also achieving some of the micro-scale fluid accelerations of the corrugated separator of  FIGS. 9 and 10 . 
         [0064]      FIGS. 17 and 18  illustrate a dual compartment tank with a corrugated separator with non-uniform corrugation  120 . The non-uniform corrugation helps to amplify the turbulence within the compartments by significantly accelerating and decelerating the upward flow of fluid. 
         [0065]      FIG. 19 and 20  illustrate an embodiment of the invention with a tri-nested tapered separator  125  between a hydronics compartment and a potable water compartment. The tri-nested aspect of the separator acts to move the liquids in a manner similar to the corrugated separators while the tapered design increases the height of the separator region with having a large temperature gradient between the water and hydronics compartments. 
         [0066]      FIG. 21  shows an alternate embodiment of the invention with a tri-nested conical separator  130  between hydronics and potable water compartments. 
         [0067]      FIGS. 22 and 23   a  show another embodiment with a tapered separator  135  between a hydronics compartment and a potable water compartment.  FIG. 23   b  shows the upward velocity of the hydronics fluid in  FIG. 23   a  relative to elevation. Due to the steady state of fluid in the hydronics compartment and the shape of the tapered separator, the upward velocity increases as the horizontal cross-sectional area of the hydronics compartment decreases. 
         [0068]      FIGS. 24 and 25  show another embodiment of the invention with a bulbous separator  140  between the hydronics and potable water compartments. This type of separator offers a significant surface area between the two compartments while also providing a significant potable water storage volume.  FIG. 25  also highlights a linear column of fluid  142  stored within the dual-compartment tank and extending from a fluid input at a lower elevation to a fluid output at a higher elevation. The linear shape of the column of fluid helps to improve mixing during low flow conditions by decreasing the minimum path a portion of the fluid must travel to mix with the most distant portion of fluid. 
         [0069]      FIGS. 26 and 27  illustrate an example of a dual compartment tank with flow agitating outer rings  110  connected to a separator. Agitating outer compartment rings  145  are attached to the outer casing of the tank. The agitating outer compartment rings further increase the turbulence within the hydronics compartment to homogenize the fluid temperature within the compartment. 
         [0070]      FIG. 28  shows an example of a dual compartment tank with a rectangular outer casing  150 . While water tanks are typically constructed in a cylindrical shape, a rectangular outer casing allows for closer packing of multiple dual compartment tanks. It is also within the scope of the invention to utilize multiple dual compartment tanks linked together in either series or parallel to heat potable water with hydronics fluid. The use of multiple smaller tanks instead of a single large tank allows for easier transport as well as easier replacement of a defective portion of the system. 
         [0071]      FIGS. 29 and 30  illustrate an example of a dual compartment tank with a rectangular inner casing  155  and a rectangular outer casing  150 . The rectangular shapes allow the tank to be constructed without having to roll or spiral materials. Additionally, the pyramidal design of the inner tank allows it to be formed with only linear welds or seams. The inner casing is constructed from four substantially planar sides that are fused together by four substantially linear seams. The top of the inner casing can also be sealed with four linear seems. 
         [0072]      FIGS. 31 and 32  illustrate an example of a dual compartment tank with a suspended inner compartment  160 . The suspended inner compartment is almost completely surrounded by hydronics fluid in the outer compartment except for the inlet and outlet circulating water through the inner compartment. By surrounding the inner compartment, the surface area of fluid contact is increased and the heat transfer from the hydronics fluid to the potable water is increased. Additionally, the use of a suspended type inner tank may assist in the fabrication of the dual compartment tank. With the possible exception of the potable water inlets and outlets, the suspended inner compartment may be fully constructed outside of the outer casing, pressure tested for leaks, and then inserted into the outer casing to form the dual compartment tank. 
         [0073]      FIG. 32  further illustrates the suspended inner compartment having a lower diameter  170  at the same elevation as a fluid input and an upper diameter  175  at the same elevation as the fluid input. Extending from the lower diameter to the upper diameter is a linear cylindrical column of fluid  180 . The upper diameter is substantially larger than the lower diameter which causes the upward velocity of fluid through the compartment to decelerate with increased elevation. In the cross-section shown in  FIG. 32 , the separator of the interior compartment has a conical exterior surface with two linear portions  185  extending from the upper diameter  180  to the lower diameter  175  on either side of the cylindrical fluid column. Only one cross-section of the interior compartment is shown in  FIG. 32 , however due to the structural symmetry of the compartment, multiple orthogonally oriented cross-sections would have a similar structure. 
         [0074]      FIG. 33  illustrates an example of a dual-compartment dual-pressure tank showing cartoon depictions of single acting automatic isolation valves ( 190  and  192 ) and a double acting automatic isolation valve  195  that isolates the potable water compartment in the event of a catastrophic decrease in water pressure. The valves may be designed like  190  to require a manual reset after they have isolated the potable water compartment in response to a decrease in pressure. Valves that require a manual reset help to ensure that a tank user, such as a home owner, is aware that there was a loss of water pressure and corrective actions, such as flushing the potable water system, can be taken before the water is utilized for human consumption. Alternatively, the valves can structured similar to  192  so that after the water pressure has returned to a normal operating level, the valve automatically allows water to flow into and out of the potable water compartment. In the cartoon depictions, the distance the internal sliding component is allowed to move is indicative of whether or not the valve will automatically reset once normal water pressure has been restored. 
         [0075]    Double acting isolation valves  195  may be used so that the potable water compartment is isolated if the water pressure drops below a threshold value relative to the pressure inside of the hydronics compartment. For example, if there is a hole in the compartment separator and there is a substantial decrease in water pressure due to a utility water main freezing and breaking, then the greater pressure in the hydronics compartment will force the dual acting valve into a state that isolates the potable water compartment. Alternatively, if the hydronics fluid has been drained from the system and there is a substantial decrease in water pressure, the potable water compartment will not be isolated because the pressure in the hydronics compartment is not greater than the pressure in potable water compartment. 
         [0076]    While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting. Consequently, variations and modifications commensurate with the above teachings, and with the skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are intended to illustrate best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. 
         [0077]    It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.