Abstract:
A water tank as part of a system that limits the pressure in the system and eliminates the need for a separate expansion tank. The water tank includes a hot water pipe with an inlet positioned a first distance below the top of the water tank, the first distance is determined so that the volume above the hot water pipe inlet exceeds a volume that water in the tank will expand when changing from a first low temperature to a second higher temperature. In a closed loop hydronic system embodiment, when dissolved air in the water separates, the separated air is caught by the volume of air at the top of the water tank which prevents the separated air from traveling through the closed loop system.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. provisional application No. 62/101,779 filed on Jan. 9, 2015 which is incorporated by reference herein in their entirety. 
     
    
     FIELD 
       [0002]    Embodiments relate to the field of liquid storage tanks and more particularly to hot water pressurized tanks. 
       BACKGROUND 
       [0003]    Storage tank water heaters have long been used to supply heated potable water to be dispensed at sinks, showers, baths, laundry facilities, dishwashing and various other human needs within a structure. These storage tanks are pressure resistant vessels capable of safely withstanding the pressures typical in heated water systems. The temperature in the storage tank can vary over time for many reasons including standby loss of heat through the tank walls themselves as well as instances when water is drawn from the tank for any of the uses detailed above. When heated water is drawn from the tank, it is typically replaced with lower temperature water from sources such as wells and distributed water systems, which will cause the tank temperature to drop for a period of time. When the temperature drops to a certain set point, heat is added to the tank from various sources such as combustible fuels, resistive electric elements, or heat exchangers, which exchange heat from separate boilers, heat pumps or other commonly available heat sources. This added heat causes the temperature to rise to a somewhat higher set point. 
         [0004]    Another use of storage tank water heaters is as a heat source for hot water based (hydronic) space heating. Again, in these instances, there is a range of temperatures over which the tank (pressure vessel) will operate, and pressures which must be withstood. In this case, the variation is due both to standby heat loss through the wall of the tank as well as the changing heat load of the structure being heated. As the heat load of the structure varies, control systems may be employed to cause the temperature set points of the tank to vary upward or downward. 
         [0005]    Water that changes in temperature changes in volume. Whether being used for their more common purpose of heating potable water or the less common purpose of heating water for hydronic space heating systems, these tanked systems must allow for the changing volume of the stored water in the tanks themselves as well as the changing volume of the water contained in piping connected to these tanks. Because water is an incompressible fluid, unless this changing volume is allowed for, tanks, piping or both may rupture. 
         [0006]    To mitigate the issues related to the changing volume of stored water when the temperature of that water changes, many devices have been developed to allow for the temperature related change of volume. Two general approaches have been taken to mitigate this change of volume. 
         [0007]    A typical solution has been to have a separate pressure vessel (expansion tank) attached either directly or indirectly to a heated water storage tank. A commonly used example of this approach has been a pressure vessel with a bladder inside separating two volumes within the pressure vessel. On one side of the bladder is a pressurized volume of gas and the other side is a volume of water connected directly or indirectly to the water heater&#39;s storage tank. As the volume of water in the system expands with rising temperature, this excess volume flows into the water side of the expansion tank causing the volume on the gas side of the bladder to decrease with a resulting increase in pressure, thereby mitigating the increase in volume of water in the heated water system. Because these bladders must be able to be flexible, they are typically made out of elastomeric materials, which tend to lose their elastomeric properties over time. Bladder failure can be a cause of periodic replacement of the expansion tank. If the failure is not noticed, the system itself may fail and rupture due to expansion of the water volume without a properly operating expansion tank. 
         [0008]    Other approaches have employed separate tanks that employ moveable bellows, moving pistons or other mechanical means that offset the changing volume. These approaches also fail from time to time because the bellows fatigue or because the seals at the pistons fail. 
         [0009]    Another approach has been to incorporate the expansion mitigation within the pressure vessel of the storage tank itself. This avoids some of the cost of manufacturing a separate pressure vessel of sufficient strength. 
         [0010]    There have been examples of this approach that utilize immersed pressurized bladders. These suffer from the same flaw other elastomeric bladder based systems suffer from, namely, loss of elastomeric properties over time. When these bladders fail, because they are contained within the primary pressure vessel of the storage tank, they are harder to replace than expansion devices, which are distinct from the storage tank. 
         [0011]    There have been immersed versions of the piston type or bellows type expansion devices, similar in many respects to those expansion devices that have been utilized outside of the tank. They suffer from the same flaws of failure of the seals at the pistons, or fatigue of the bellows and like other immersed devices are difficult to service when there is a failure. At least one solution uses a cylinder attached to the top of the tank, which is open at the bottom of the cylinder, and utilizes trapped air expanding and contracting within the inverted cylinder to provide an ability to mitigate thermal expansion of the water in the system. But due to the changing solubility of gases in water due to temperature or pressure changes, in such a device the volume of trapped air can vary to a degree that insufficient expansion volume is maintained at needed levels. The general flaw with all of these inside-of-tank solutions is failure over time combined with difficulty in mitigating the eventual failure. 
         [0012]    In addition to the volume of water changing with temperature, the water in these systems often contains air as a dissolved gas, as well as air bubbles of various sizes. In potable water systems the dissolved air or air bubbles are of little consequence because they are continuously purged from the system as water flows out of the system at faucets and other outlets. But hydronic systems are typically closed loop systems and this air, when contained in closed loop systems, can cause a variety of problems, most notable being noise. This contained air can also cause pumps to malfunction and/or can cause air locks at high points in a piping system that can prevent proper flow through the system. To prevent these problems, air eliminators are typically employed to remove air that may be contained in these systems. These devices tend to have internal structures that cause bubbles to be arrested as they travel through the device. Bubbles thus arrested rise to the top of the devices and are purged through various valve configurations located at the top of these devices. 
       SUMMARY OF THE EMBODIMENTS 
       [0013]    Embodiments include a storage device for holding and heating water, comprising: a container designed to hold a first amount of water, having a side, a floor and a ceiling; a first pipe having a first outlet positioned within said container for bringing cold water into said container; a second pipe having a first inlet positioned within said container at a level above said first outlet, for transferring heated water out of said container, said first pipe passing through said ceiling; and a heating device for heating the water in said container; wherein said first inlet is positioned at a first distance from said ceiling such that a first volume of said container being the volume between said first inlet and said ceiling exceeds a second volume being a difference in volume between said first amount of water at a first temperature and said first amount of water at a second temperature. 
         [0014]    The storage device may further comprise seals between said container and the first and second pipes prevent air from leaving said container through said seals. In addition the storage device may receive water from said first pipe at a temperature at or above said first temperature and the storage device may heat the water to a temperature at or below said second temperature and wherein no portion of said container substantially moves in response to a pressure changes within said container. 
         [0015]    In an embodiment the storage device further includes a water level indicator. The 
         [0016]    water level indicator may include a tube having a closed end, an open end, and a transparent portion; and an indicator device, positioned in said open end and in said transparent portion to identify the water level in said container where the indicator device has a floating device positioned in said open end and an extender having an portion visible in the transparent portion and coupled to said floating device, the position of the extender indicative of the water level in said container. 
         [0017]    The storage device may also include a valve for at least one of releasing air from said container or adding air to said container and a pressure gauge to identify the air pressure in said container. 
         [0018]    The water level indicator may include a first opening positioned below the level of said first inlet; a second opening positioned above a water level in said container; a transparent portion, between said first and second openings, wherein the water level is visible when the water level is above the first opening. The first and second openings may be connected to the container and include water level indicator seals that prevent air from escaping the combination of said container and water level indicator. 
         [0019]    Embodiments include a closed loop hydronic system comprising: a storage device for holding and heating water, comprising: a container designed to hold a first amount of water, having a side, a floor and a ceiling; a first pipe having a first outlet positioned within said container for bringing water into said container; a second pipe having a first inlet positioned within said container at a first inlet level above said first outlet, for transferring heated water out of said container, said first pipe passing through said ceiling, said water level in the container being above said first inlet level; and a heating device for heating the water in said container; wherein said first inlet is positioned at a first distance from said ceiling such that a first volume of said container being the volume between said first inlet and said ceiling exceeds a second volume being a difference in volume between said first amount of water at a first temperature and said first amount of water at a second temperature. 
         [0020]    In the system air bubbles in the closed loop system are collected into said first volume and air in said first volume limits the pressure in the closed loop system and eliminates a need for an expansion tank external to said container in the closed loop system. The system may include a water level indicator to provide an indication of said water level in said container and a valve for at least one of releasing air from said container or adding air to said container. For example, if said water level in said container approaches said first inlet level, air can be removed from the system using said valve. The system may also include a pressure gauge to identify the air pressure in said container. 
         [0021]    Advantages of embodiments include: (a) accommodating volume variation caused by temperature variation in a water heater and in a closed loop hydronic system that employ storage tanks, without the use of separate expansion tanks or the use of elastomeric materials, pistons, bellows or other moveable devices that can fail over time; (b) for closed loop heated water systems that employ storage tanks, and are used for hydronic heating, a means to prevent air from circulating through the hydronic circuits of the system; (c) system and methods for using a volume of trapped air at the top of a storage tank type water heater, that includes a device for adjusting the pressure and amount of that trapped air volume, in a manner such that its ability to match the varying volume in a heated water system due to temperature variation can be easily monitored, maintained and thereby optimized without failure over long periods of time; and (d) system and methods for eliminating the need for a separate device to prevent air from circulating in a hydronic heating system. 
         [0022]    The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is an illustration of a water tank that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems in accordance with an embodiment. 
           [0024]      FIG. 2  is an illustration of a water tank that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems with the water/air level at the exit level of exit pipes in accordance with an embodiment. 
           [0025]      FIG. 3  is an illustration of a water tank that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems with the water/air level above the exit level of exit pipes in accordance with an embodiment. 
           [0026]      FIG. 4  is an illustration of a water tank that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems including a water level indicator in accordance with an embodiment. 
           [0027]      FIG. 5  is an illustration of a water tank that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems including a water level indicator in accordance with an embodiment. 
       
    
    
       [0028]    The figures depict various embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Embodiments of the present invention are now described with reference to the figures where like reference numbers indicate identical or functionally similar elements. Also in the figures, the left most digits of each reference number corresponds to the figure in which the reference number is first used. 
         [0030]      FIGS. 1-3  are illustrations of a water tank that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems in accordance with an embodiment. Referring now to  FIGS. 1-3 , in embodiments, there is a pressure vessel, alternatively referred to as a tank ( 1 ) that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems. The tank contains a volume of water or other liquid (referred to as water for ease of description) ( 2 ), and a device for adding heat to the water ( 3 ). In an embodiment there is piping entering the top of the tank that brings cooler water into the tank ( 4 ) and piping that draws heated water out of the tank ( 5 ). One or more additional pipes may be attached to the top or other portion of the tank to allow the installation of pressure relief valves ( 6 ), piping for recirculating potable water systems, water level gauges ( FIG. 4 ) or other purposes. These pipes can be welded, brazed, glued or otherwise bonded and sealed to the top of the tank, in some embodiments the seal ( 7 ) is permanent such that it will not allow air or water to pass at the point where they enter the tank. In embodiments, all pipes attached to the top of the tank have their highest exit/inlet point at or below a level in the tank ( 8 ) that allows for a tank volume ( 9 ) above that level to be greater than whatever may be the needed volume to allow for maximum calculated water volume change, due to thermal expansion, for the system. In an embodiment exit pipes, e.g., pipes  5  and  6  both have inlets at approximately the same level ( 8 ). The water volume change can be based on the water volume contained in the tank when the water level slightly exceeds the pipe inlet level ( 8 ) and the change in temperature can be the difference between the temperature of the coldest water the tank anticipates receiving or becoming (or the temperate of the water at the lowest expected density, e.g., approximately 4 degrees Celsius) and the highest temperature the water is expected to reach. 
         [0031]    When the tank is initially filled with water via pipe  4  ( FIG. 1 ) air ( 10 ) is expelled from the tank through the various exit pipes ( 5 ,  6 ) attached to the top of the tank. This expelled air is removed from the system plumbing at faucets or other valved fixtures in the system at the start up of a plumbing system. In closed hydronic systems, this air can be removed using a valve. As the tank is filled, air and water naturally separate vertically due to the differences in their density. In embodiments, once the air/water separation ( 11 ) level in the tank is even with the level ( 8 ) which is at or above the inlets to the various exit pipes ( 6 ,  7 ) that are also affixed to the top of the tank ( FIG. 2 ), air can no longer exit the tank through those pipes and becomes trapped at the top of the tank. All pipes protruding through the tank are sealed so that no air or water may escape the tank around the seals. Once the water reaches that level ( 8 ), only water, but not air, can exit the tank because all pipes attached to the top of the tank have their openings within the tank, submerged in water. Initially the tank becomes filled to that level, at atmospheric pressure. As the tank continues to fill due to the elevated pressure at which these systems tend to operate, the tank pressure rises above atmospheric pressure by some finite amount, thereby compressing the trapped air and raising the air/water separation level ( 11 ) in the tank above the level of the lower openings of the exit piping ( 8 ) by a finite amount ( 12 )( FIG. 3 ). This will ensure that the trapped air ( 13 ), remains trapped and is prevented from entering the system piping. 
         [0032]    Another embodiment allows for the monitoring and adjustment of the air/water separation level. This may be required because in potable water based tanked systems, varying amounts of gas will dissolve in the tank water as pressure or temperature conditions vary. This air may then be transported out of the tank, and be expelled at faucets or other system outlets. Should this happen, the volume of air trapped may be reduced, and therefore the required expansion volume may become insufficient for system needs. To mitigate this circumstance, in this embodiment, a water level indicator of various configurations, for example, as shown in  FIG. 4  and  FIG. 5 , may be affixed to the tank. 
         [0033]      FIGS. 4 and 5  are illustrations of a water tank that is capable of safely resisting the typical pressures utilized in potable water and hydronic systems including a water level indicator in accordance with an embodiment. In  FIG. 4 , the water level indicator has a clear tube ( 14 ). A float, which is part of the gauge ( 15 ), freely moves up or down with changing water levels. A rod ( 16 ) affixed to the float has an indicator ( 17 ) affixed to the rod. Marks may be placed on the clear tube to indicate the ideal range of water levels within the tank. An additional feature of this water level indicator may be a pressure gauge ( 18 ), which may be affixed directly to the level indicator or to other locations that are part of the water system, where the pressure in the system can be monitored. In combination with this gauge ( 18 ) can be an air valve ( 19 ) that will allow the air pressure to be easily adjusted to the ideal range. This air valve ( 19 ) may be affixed directly to the water level indicator or may alternatively be affixed to the tank directly in a manner that allows air to be pumped under pressure into the volume of trapped air ( 9 ) at the top of the tank ( 13 ). Should pressure rise above an optimum amount, air may be bled out of the air valve ( 19 ) to adjust the pressure downward. By this, the pressure of the system may be maintained in an optimum range. 
         [0034]      FIG. 5  depicts another embodiment of the water level indicator. In this embodiment, the top of the essentially “U” shaped gauge is connected to the tank above the highest expected water level within the tank ( 20 ) and below the highest exit point ( 8 ) of the piping. There is a clear section in the water level indicator ( 21 ) that allows the level of water in the tank to be directly be determined by visually. As in the embodiment depicted in  FIG. 4 , a pressure gauge ( 18 ) and air valve ( 19 ) allow the pressure of the trapped air volume ( 13 ) to be monitored and adjusted as may be needed. As in the embodiment of  FIG. 4 , the pressure gauge and air valve have other possibilities for location. 
         [0035]    These embodiments of the water level gauge, and the system and method for monitoring and adjusting pressure are but two possible embodiments for this function. Electronic water level monitoring as well as other systems and methods known to those of ordinary skill in this field may alternatively be utilized for this function of ensuring that pressure and air volume may be adjusted for optimum performance of the system, and any such embodiments are considered to be within the scope of the embodiments. 
         [0036]    These various systems and methods of monitoring and adjusting water levels as well as pressure levels are a particularly important feature in a tank based, closed-loop hydronic system. In these types of closed loop systems, at startup, it is common for bubbles, both visible and microscopic, as well as other air volumes or dissolved air to be present. Over time, due to the constant recirculating flow of water through these systems, this air contained in the system at startup will pass through to the tank ( 1 ). Upon entering the tank, this air will rise due to its natural buoyancy and be added to the volume of air trapped at the top of the tank ( 13 ). Depending on the volume of air contained throughout the system piping at startup, once it reaches the tank it may eventually cause the volume of air trapped at the top of the tank for expansion purposes, to increase to a point that the air/water separation level approaches or falls below the level of the inlets ( 8 ) to the various pipes attached to the top of the tank, thereby allowing air to re-enter the hydronic system. Should it do so, it will allow air to be re-circulated through the hydronic system causing noise as well as other problems. Having the water level gauge ( 18 ) in combination with an air valve ( 19 ), allows excess air to be removed so that the ideal water level range is maintained. 
         [0037]    Alternatively, if there is an inadvertent leak in the system that allows the volume of air intended for expansion purposes to be less than within the desired range, once such leak is resolved, the air volume can be adjusted by adding air under pressure back into the tank, through the same air valve ( 19 ) until the desired air/water separation level is achieved. Should this be needed, embodiments, which include a pressure gauge ( 18 ) as part of the water level monitoring system, will allow air to be pumped into the tank to adjust the system to an optimum pressure range within the storage tank. 
         [0038]    Reference in the specification to “one embodiment” or to “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment. The appearances of the phrase “in one embodiment” or “an embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
         [0039]    In addition, the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the embodiments, which is set forth in the claims. 
         [0040]    While particular embodiments and applications have been illustrated and described herein, it is to be understood that the embodiments are not limited to the precise construction and components disclosed herein and that various modifications, changes, and variations may be made in the arrangement, operation, and details of the methods and apparatuses of the embodiments without departing from the spirit and scope of the embodiments as defined in the appended claims.