DIFFUSER FOR THERMAL STORAGE TANK

A diffuser is provided for use in a thermal storage tank. The diffuser includes a fluid inlet to receive a flow of liquid into the diffuser, and a fluid outlet to discharge the flow of liquid out of the diffuser into an internal volume of the thermal storage tank. A flow circuit extends between the fluid inlet and the fluid outlet. A plurality of flow sections are sequentially arranged along the flow circuit. Each one of the plurality of flow sections defines a cross-sectional flow area for the flow of liquid. The cross-sectional flow area within any one of the plurality of flow sections is greater than the cross-sectional flow area within any of the plurality of flow sections arranged upstream of said one of the plurality of flow sections.

BACKGROUND

The present invention relates to a diffuser for a thermal storage tank which may, for example, be used as part of, or in conjunction with, a system for heating water.

Thermal storage tanks are used in a hot water system to store water that has been heated prior to a demand for heated water. The use of a thermal storage tank can be beneficial when, for example, the demand for hot water is intermittent. Short duration, high flowrate demands for hot water can be met by heating water over longer durations at slower rates and storing the heated water within one or more thermal storage tanks in order to satisfy the demands as they arise.

A thermal storage tank is loaded or charged with hot water by drawing cold water from the tank's lower portion, flowing the water through a heat engine, heating the water to a desired temperature in the heat engine, and returning the water at the desired temperature to the thermal storage tank through the tank's upper portion. In addition, when hot water is drawn from the upper portion of the thermal storage tank to be used by a user, cold water is discharged into the lower portion of the thermal storage tank to replace the hot water.

A criterion for evaluating the capability of a hot water thermal storage tank is the tank's volume usage efficiency. As the heated water at a desired temperature is drawn from the tank and is replaced with water that is unheated or at a substantially lower temperature, mixing between the stored, heated water and the lower temperature replacement water can occur within the tank. As a result, during a sustained draw of water, the temperature at which the heated water is delivered from the tank will be undesirably reduced. Volume usage efficiency is a measure of the percentage of the tank's total storage capacity that can be delivered as water at a desired temperature during a sustained draw.

Using known techniques, cold water entering the lower portion of a thermal storage tank and hot water returned to the upper portion of the thermal storage tank from a recirculation line are discharged through traditional pipe nipples or other pipe connections. Discharging the cold water into the lower portion and hot water into the upper portion using known techniques leads to a mixing of cold and hot water within the thermal storage tank before the water can gradually stratify in the thermal storage tank during standby.

SUMMARY

A new water diffuser is provided to minimize mixing in the thermal storage tank of cold water entering the lower portion or hot water returned from the heat engine. With minimum mixing, water is significantly stratified between the upper portion and the lower portion of the storage tank. More specifically, water within the upper portion of the tank has a temperature that is uniform and very close to that of water leaving the heat engine; and water within the lower portion has a temperature that is also uniform but much lower than that of water leaving the heat engine. Thus a portion of the thermal storage tank is charged with water at desired temperature and the efficiency of the heat engine can be ensured by the low temperature of inlet water coming from the lower portion of the thermal storage tank.

In one embodiment, the invention provides a diffuser for use in a thermal storage tank. The diffuser includes a fluid inlet to receive a flow of liquid into the diffuser, and a fluid outlet to discharge the flow of liquid out of the diffuser into an internal volume of the thermal storage tank. A flow circuit extends between the fluid inlet and the fluid outlet. A plurality of flow sections are sequentially arranged along the flow circuit. Each one of the plurality of flow sections defines a cross-sectional flow area for the flow of liquid. The cross-sectional flow area within any one of the plurality of flow sections is greater than the cross-sectional flow area within any of the plurality of flow sections arranged upstream of said one of the plurality of flow sections.

In another embodiment, the invention provides a diffuser for use in a thermal storage tank. The diffuser includes a cylindrical inlet pipe to direct a flow of liquid into the diffuser along a first flow direction. The cylindrical inlet pipe defines a first flow section. A second flow section is arranged downstream of the first flow section and fluidly connected thereto to direct the flow of liquid through the diffuser along a second flow direction. The second flow direction is different than the first flow direction. A third flow section is arranged downstream of the second flow section and fluidly connected thereto to direct the flow of liquid through the diffuser along a third flow direction. The third flow direction is different than the second flow direction. A plurality of additional flow sections are sequentially arranged downstream of the third flow section. The third flow section and the plurality of additional flow sections are fluidly connected to one another to direct the flow of liquid through the diffuser alternatingly along the second and the third flow directions. A fluid outlet is arranged downstream of a terminal one of the plurality of additional flow sections and fluidly connected thereto to discharge the flow of liquid out of the diffuser into an internal volume of the thermal storage tank.

In yet another embodiment, the invention provides a method of discharging a thermal storage tank including removing, at a top end of the thermal storage tank, a first flow of liquid from an internal volume of the thermal storage tank at a sustained flow rate. The first flow of liquid is at a first temperature when discharging is initiated. The method also includes receiving a second flow of liquid at a second temperature that is at least 100 degrees Fahrenheit lower than the first temperature into a diffuser arranged at a bottom end of the thermal storage tank at a first kinetic energy state. The method further includes directing the second flow of liquid through a plurality of sequentially arranged flow sections within the diffuser. Each one of the plurality of sequentially arranged flow sections defines a cross-sectional flow area for the second flow of liquid. The cross-sectional flow area of any one of the plurality of flow sections is greater than the cross-sectional flow area of any of the plurality of flow sections arranged upstream of said one of the plurality of flow sections. The method further includes discharging the second flow of liquid from the diffuser into an internal volume of the thermal storage tank at a second kinetic energy state lower than the first kinetic energy state. The first flow of liquid is at a third temperature after a volume of liquid equal to 90% of the internal volume has been discharged by removing the first flow of liquid. The third temperature in degrees Fahrenheit is at least 95% of the first temperature in degrees Fahrenheit.

DETAILED DESCRIPTION

Referring toFIGS. 1-2, the present invention provides a water heater10including a water storage tank20and a heating circuit30external to the tank20. The heating circuit30includes a heat engine34for heating water for storage in the tank20. The heat engine34can be, for example, a gas-fired tankless water heater, an electric element water heater, a heat-pump water heater, or any other type of boiler or water heater. With additional reference toFIG. 2, the water heater10also includes a lower diffuser assembly40A and an upper diffuser assembly40B. The lower and upper diffuser assemblies40A,40B are positioned at least partially within the tank20to control of the delivery of water to the tank20and the drawing of water from the tank20, as will be described in more detail below. In other embodiments, the water heater10may only include one of the lower diffuser assembly40A and upper diffuser assembly40B.

The tank20extends between a first, bottom end52, and a second, top end54. The bottom and top ends52,54are sometimes referred to in the art as top and bottom heads. An outer wall58extends between the bottom and top ends52,54. The tank20defines an internal volume60therewithin between the bottom and top ends52,54and the outer wall58. The internal volume60includes a lower portion64proximate the bottom end52, and an upper portion68proximate the top end54of the tank20. During standby, water in the internal volume60naturally stratifies due to the relative densities of hot and cold water, such that the coldest water sinks to the lower portion64and the hottest water rises to the upper portion68. In reality, this stratification defines a gradient from bottom to top of the coolest water to the hottest water. For the purposes of this disclosure, the term “hot” is used to describe all water at or above a useful temperature which is hot enough for the intended use of a user drawing water from the thermal storage tank. The hot water cannot exceed an upper threshold temperature or it may become unusable by the user without being blended with cold water or otherwise having its temperature lowered to make it useable. The term “cold” is used to describe all water that is below the useful temperature. Temperatures of the hot water may be one hundred degrees Fahrenheit or more above the temperatures of incoming cold water.

The tank20further includes a cold water connector70(FIG. 2) extending horizontally through the outer wall58in the lower portion64and a hot water connector74extending vertically through the top end54. In other embodiments, the cold water connector70may extend vertically through the bottom end52and the hot water connector74may extend horizontally through the outer wall58of the upper portion68. In other embodiments, both the cold water connector70and hot water connector74can be horizontal or vertical.

The cold water connector70and hot water connector74may each be, for example and without limitation, a spud or a pipe nipple. The cold water connector70and hot water connector74each have threads (internal or external) or another plumbing joining feature. The cold water connector70and hot water connector74are permanently and water-tightly affixed (e.g., by welding) to the tank20to provide a rigid connection point. The lower diffuser assembly40A is in fluid communication (e.g., through a threaded connection) with the cold water connector70and the upper diffuser assembly40B is in fluid communication (e.g., through a threaded connection) with the hot water connector74.

A cold water connection pipe78is in fluid communication (e.g., by threaded connection) with the cold water connector70such that the cold water connection pipe78communicates with the lower diffuser assembly40A. The cold water connection pipe78connects to and communicates with a cold water supply line82of the building such that cold water from the cold water supply line82flows through the cold water connection pipe78and cold water connector70to the lower diffuser assembly40A. A cold-side tee84places the lower diffuser assembly40A, cold water connection pipe78, and cold water supply line82in communication with the heat engine34as will be described in more detail below. The cold-side tee may take the form of a switch that toggles between placing the lower diffuser assembly40A and cold water connection pipe78in communication with either the cold water supply pipe78or the heat engine34. In this regard, the term “tee” will be used to broadly cover both a basic tee and a switch.

A hot water connection pipe88is in fluid communication (e.g., by threaded connection) with the hot water connector74, such that the hot water connection pipe88communicates with the upper diffuser assembly40B. The hot water connection pipe88connects to and communicates with at least one hot water delivery line90in the building, such that hot water is drawn from the upper portion68through the upper diffuser assembly40B, hot water connector74, and hot water connection pipe88and delivered to a hot water consuming device for an end user through the hot water delivery line90. The hot water consuming device may be, for example and without limitation, a faucet, shower, or appliance. A hot-side tee94places the upper diffuser assembly40B, hot water connection pipe88, and hot water delivery line90in communication with the heat engine34, as will described below. In other embodiments, the hot-side tee94may take the form of a switch that toggles between placing the upper diffuser assembly40B and hot water connection pipe88in communication with either the hot water delivery line90or the heat engine34. As noted above, the term “tee” is used broadly to include both a basic tee and a switch.

The heating circuit30further includes a pump98for moving the water through the heating circuit30in order to fill the tank20with heated water during a charging event of the thermal storage tank. Cold water from the lower portion64of the tank20is drawn by the pump98through the lower diffuser assembly40A and cold water line84and delivered to the heat engine34where the cold water is heated. The pump98forces the water through the heat exchanger34and returns the heated water to the upper portion68of the tank20as hot water through the hot water connection pipe88and the upper diffuser assembly40B. The heat engine34may be substantially any heat engine (e.g., gas-fired tankless water heater, electric tankless water heater, steam heat exchanger, heat pump) external to the tank20. In some embodiments, the heating circuit30may include multiple pumps98and/or heat engines34connected in series and/or parallel. Furthermore, in some embodiments, one or more heat engines34may be positioned on or within the tank20for heating the water within the tank20. When the water heater10is operating with the pump98activated and moving water from the lower portion64of the internal volume60, through the heat engine34, and back to the upper portion68of the internal volume60, the water heater10is in a charging mode in which it is increasing the volume of hot water in the internal volume60.

When there is a call for hot water by the hot water consuming device, the pressure drops in the hot water delivery line90(e.g., a faucet is opened by a user such that the hot water delivery line90is exposed to atmospheric pressure at the faucet). Cold water from the cold water supply line82is at elevated pressure (e.g., some pressure above atmospheric) and consequently pushes into the lower portion64of the tank20via the cold water supply line82, cold water connection pipe78, and lower diffuser assembly40A to displace hot water from the upper portion68of the tank20through the upper diffuser assembly40B, hot water connection pipe88, hot water delivery line90, and the hot water consuming device. When the water heater10is delivering hot water to the hot water consuming device as described in this paragraph, the water heater10is in a discharging mode in which the volume of hot water in the internal volume60is decreasing.

The cold water connection pipe78and the hot water connection pipe88are configured to allow water to flow in a charging direction when the water heater is in the charging mode and in an opposite discharging direction when the water heater is in the discharging mode. As such, the flow of water through the respective diffuser assemblies40A,40B may be reversed when switching between the charging and discharging modes. In other embodiments, the tank20may include other additional connection ports, separate from the cold water and hot water connectors70,74, respectively, for drawing water out of the tank20during the discharging mode such that the flow of liquid through the respective diffuser assemblies40A,40B is in a single direction into the tank20. The illustrated diffuser assemblies40A,40B have identical diffusers. Multiple embodiments of the diffuser (which can be used in either or both of the lower diffuser assembly40A and upper diffuser assembly40B) will now be described.

FIGS. 3-4illustrate a first example embodiment of a diffuser110. The diffuser110includes a body114, a fluid inlet118, and a fluid outlet122. A flow circuit126(FIG. 4) connects the fluid inlet118and the fluid outlet122. The body114includes a central axis of symmetry130extending therethrough. The flow circuit126is positioned within the body114. Arrows are provided inFIG. 4to illustrate the general flow direction of the water along the flow circuit126in one mode of operation of the diffuser110. It should be understood however, that in some other mode of operation the flow of water along the flow circuit126is reversed from that shown inFIG. 4

The body114extends between a first end134and a second end138. In the illustrated embodiment, the body114includes a pair of spaced apart planar walls142, and a cylindrical outer wall146extending between the pair of spaced apart planar walls142. A first one of the pair of spaced apart planar walls142is positioned at the first end134, and a second one of the pair of spaced apart planar walls142is positioned at the second end138. The pair of spaced apart planar walls142and the outer wall146define an outer boundary of the diffuser110.

A height Y1of the outer boundary of the diffuser110is measured between the first end134and the second end138. In the illustrated embodiment, the pair of spaced apart planar walls142define the height Y1. In addition, the cylindrical outer wall146defines an outer diameter X1of the outer boundary. In some embodiments, the outer diameter X1is in the range of two to five times the height Y1of the diffuser110. For example, in the illustrated embodiment, the height Y1is four inches, and the outer diameter X1is fourteen inches. Accordingly, the outer diameter X1is 3.5 times the height Y1. A diffuser110of such dimensions can be appropriate for a particular size thermal storage tank, for example a thermal storage tank with a water capacity of approximately 200 gallons. In other embodiments, where the diffuser is to be used in a thermal storage tank of greater or lesser capacity, the dimensions of the diffuser may scale up or down in order to be appropriately sized for use in a tank of such capacity, but the ratio between the outer diameter X1and the height Y1can be maintained within a desirable range.

With particular reference toFIG. 4, the fluid inlet118is fluidly connected to the body114. The illustrated fluid inlet118is provided by a cylindrical inlet pipe154extending through the planar wall142at the first end134of the body114. An end158of the inlet pipe154is spaced away from the opposite planar wall142positioned at the second end138of the body114. The fluid inlet118is configured to receive a flow of liquid into the diffuser110. More specifically, the fluid inlet118is connected to the cold water or hot water connection pipe78,88(e.g., via the cold water connector70or hot water connector74, respectively) to receive water from the cold water supply line82or the heat engine34, respectively.

The fluid outlet122of the diffuser110fluidly connects the body114to the internal volume60of the tank20. The illustrated fluid outlet122is provided in the cylindrical outer wall146. More specifically, the fluid outlet122includes a plurality of openings162in the cylindrical outer wall146. The fluid outlet122is configured to discharge the flow of liquid out of the diffuser110into the internal volume60of the tank20.

The direction of a flow of water into the body114of the diffuser110through the fluid inlet118, along the flow circuit126, and out of the body114through the fluid outlet122is defined as being a downstream fluid flow direction. An upstream direction is defined as opposite the downstream fluid flow direction.

With continued reference toFIG. 4, the diffuser110further includes a plurality of flow sections170A-170H sequentially arranged along the flow circuit126(i.e., relative to the downstream fluid flow direction). In the illustrated embodiment, the diffuser110includes a plurality of cylindrical baffles174A-174F, as well as the cylindrical inlet pipe154and the cylindrical outer wall146, to form the plurality of flow sections170A-170H within the body114. More specifically, each one of the plurality of cylindrical baffles174A-174F fluidly separates two sequentially arranged ones of the plurality of flow sections170A-170H. In addition, the pair of spaced apart planar walls142also partially form each one of the plurality of flow sections170A-170H. The plurality of flow sections170A-170H are fluidly connected to each other.

Each of the cylindrical baffles174A-174F extends from one of the planar walls142within the body114toward the opposite planar wall142. In addition, an end178of each cylindrical baffle174A-174F is spaced away from the opposite planar wall142. Each cylindrical baffle174A-174F is spaced radially away from the adjacent cylindrical baffles174A-174F relative to the central axis of symmetry130. The illustrated plurality of cylindrical baffles174A-174F alternately extend from the planar wall142at the first end134and the planar wall142at the second end138in a radial direction relative to the central axis of symmetry130.

The illustrated diffuser110includes six cylindrical baffles174A-174F to form seven flow sections170B-170H. Three of the cylindrical baffles174A,174C,174E extend from the planar wall142at the second end138, and the remaining three cylindrical baffles174B,174D,174F extend from the planar wall142at the first end134. In other embodiments, the diffuser110may include fewer or more cylindrical baffles174A-174F. For example, in some embodiments, the diffuser110may include four or more cylindrical baffles174A-174F. Furthermore, in other embodiments, the baffles174A-174F may have other shapes such as rectangular, triangular, etc. in which each baffle174A-174F may have the same or different shape. The diffuser110may include fewer or more flow sections170A-170H based on the number of cylindrical baffles174A-174F provided.

The cylindrical inlet pipe154defines a first flow section170A of the plurality of flow sections170A-170H. Accordingly, the illustrated diffuser includes eight flow sections170A-170H. The subsequent flow sections170B-170H arranged downstream of the first flow section170A (e.g., a second flow section170B, a third flow section170C, etc.) can be defined by the fluid inlet118and a first one of the cylindrical baffles174A, two of the cylindrical baffles174A-174F, or a terminal one of the cylindrical baffles174F and the cylindrical outer wall146. For example, the second flow section170B is defined between the cylindrical inlet pipe154and the first cylindrical baffle174A. The third flow section170C is defined between the first cylindrical baffle174A and a second cylindrical baffle174B. The eighth flow section170H is defined between the sixth, terminal cylindrical baffle174F and the cylindrical outer wall146.

Each of the plurality of flow sections170A-170H are arranged relative to the central axis130such that the central axis130is a common central axis of symmetry130between the flow sections170A-170H. For example, the illustrated first flow section170A of the cylindrical inlet pipe154is co-axial with the common central axis130, and the remaining flow sections170B-170H are co-axially aligned with the cylindrical inlet pipe154.

Furthermore, each one of the plurality of flow sections170A-170H has a flow area for the flow of liquid to flow therethrough. The flow area of each flow section170B-170H is bounded by two or more of the cylindrical baffle(s)174A-174F, the cylindrical inlet pipe154, the cylindrical outer wall146, and/or the planar walls142. Each flow area has a cross-sectional flow area. In the illustrated embodiment, the cross-sectional flow area within the first flow section170A is a circular shape. The cross-sectional flow area within each one of the remaining flow sections170B-170H (e.g., second flow section170B, eighth flow section170H, etc.) is an annular shape. While in the exemplary embodiment ofFIG. 4each of the flow sections170A-170H has a constant cross-sectional flow area over the length of the flow area, in other embodiments the flow area within one or more of the flow sections may be non-constant.

The cross-sectional flow area within any one of the plurality of flow sections170A-170H is greater than the cross-sectional flow area within any of the plurality of flow sections170A-170H arranged upstream of said one of the plurality of flow sections170A-170H. More specifically, each one of the cylindrical baffles174A-174F is positioned at a predetermined radial position relative to the common central axis of symmetry130such that a size of the cross-sectional flow area of each successive flow section170B-170H increases in the downstream fluid flow direction. In other words, the size of the cross-sectional flow area of the eight flow section170H is greater than the size of the cross-sectional flow area of the seventh flow section170G which is greater than the size of the cross-sectional flow area of the sixth flow section170F, and so on and so forth. Accordingly, the size of the cross-sectional flow area of a terminal one of the flow sections170A-170H (e.g., the eighth flow section170H) is greater than the size of the cross-sectional flow area of the remaining flow sections170A-170H.

Each flow section170A-170H is arranged to direct the flow of liquid through the diffuser110along a predetermined flow direction182A-182C. More specifically, the cylindrical inlet pipe154and the plurality of cylindrical baffles174A-174F are positioned within the body114such that the flow of liquid alternates direction relative to the common central axis of symmetry130. For example, in the illustrated embodiment, the first flow section170A is configured to direct the flow of liquid into the diffuser110along a first flow direction182A that is co-axial with the common central axis of symmetry130. The second flow section170B is configured to direct the flow of liquid into the diffuser110along a second flow direction182B that is different than the first flow direction182A. The third flow section170C is configured to direct the flow of liquid into the diffuser110along a third flow direction182C that is different than the second flow direction182B. In the illustrated embodiment, the second flow direction182B is opposite the first flow direction182A, and the third flow direction182C is aligned with the first flow direction182A. Accordingly, the flow sections170A-170H are arranged such that the flow of liquid through the diffuser110alternates along the second and the third flow directions182B,182C.

The fluid outlet122is configured to direct the flow of liquid along an outlet flow direction182D. The outlet flow direction182D may be the same or different than the first flow direction182A, the second flow direction182B, and/or the third flow direction182C. For example, in the illustrated embodiment, the fluid outlet122is configured to direct the flow of liquid along the outlet flow direction182D that is perpendicular to the first flow direction182A.

In the illustrated embodiment, the openings162that define the fluid outlet122are non-uniformly spaced along the axial direction Yl. Particularly, those ones of the opening162that are located furthest downstream along the flow section170H (i.e. closest to the first end143) are spaced more closely to one another than those located furthest upstream in the flow section170H (i.e. closest to the second end138). Such a non-uniform spacing can provide for a more even distribution of flow among the plurality of openings162. In other embodiments, the flow openings162can have other spacings, including but not limited to a uniform spacing along the height direction Yl.

While the flow of water is moving, it has a kinetic energy head that is proportional to the square of the bulk velocity of the flow. The flow of liquid received by the fluid inlet118has a first kinetic energy state, with a kinetic energy head that is provided by the pump98or by pressure from the cold water supply line82. The flow of liquid being discharged by the fluid outlet122has a second kinetic energy state that is substantially lower than the first kinetic energy state as a result of the increased flow area at the fluid outlet122.

By configuring the size of the cross-sectional flow area of each successive flow section170B-170H to be greater than the upstream flow sections170A-170G, the flow of liquid will progressively lose kinetic energy as it flows through the diffuser110. This results in a generally laminar flow of water into the tank20, which minimizes turbulence or mixing within the tank20. In some embodiments, the first kinetic energy state is at least twenty-five times greater than the second kinetic energy state.

As the heated water is delivered to the internal volume60during a charging event, it is desirable to avoid or minimize any mixing between the hot water at the upper portion68and the cold water at the lower portion64. As described above, the upper diffuser assembly40B decreases the kinetic energy head of the heated water flow, that kinetic energy head having been imparted to the heated water flow by the pump98. By sufficiently decreasing the kinetic energy head of the heated water as it enters the internal volume60, mixing of the heated water at the upper portion68and colder water at the at the lower portion64is prevented. By preventing such undesirable mixing, temperature stratification of the water within the internal volume60can be achieved, with the heated water and the cold water being separated by a horizontal plane or narrow band that progressively travels vertically downward as the water is heated.

Thermally stratifying the water during the charging event as described above can lead to more efficient heating of the water, as it ensures that the water being delivered to the heat engine34by the pump98is always the coldest possible water, thus maximizing the rate of heat transfer and heat exchange effectiveness within the heat engine34. In certain cases, and depending on multiple variables including but not limited to the type of heat engine, the incoming water temperature, and the water set-point temperature, the water can make multiple passes through the heating circuit30during the charging event. In some such cases, the temperature difference between the heated water entering through the hot water connector74and the water at the lower portion64is reduced to the point that the beneficial impact of the diffuser40B is minimal. Thus, in some embodiments, the upper diffuser assembly40B is optional.

When the water heater10is in a discharging mode, such as when there is a relatively sustained call for heated water by the hot water consuming device, heated water at the upper portion68of the tank20will be removed via the hot water delivery line90and will be replaced by colder water entering the lower portion64of the tank20via the cold water connection pipe78. During a sustained draw of hot water, the supply of heated water within the internal volume60will eventually be entirely depleted and replaced with unheated water. The length of time required for such a depletion will vary depending on the specific installation of the water heater10and the associated plumbing system, as well as the volumetric flow rate at which water is drawn from the tank20.

During the discharging event, it is highly desirable to prevent or minimize mixing between the heated water and the colder incoming replacement water. By preventing such undesirable mixing, temperature stratification of the water within the internal volume60can be achieved during the discharge event, with the heated water and the cold water being separated by a horizontal plane or narrow band that progressively travels vertically upward as the heated water is removed and is replaced by unheated water. In this manner, during a sustained draw the temperature of the water removed through the hot water connector74can be held to the storage temperature until nearly the entire volume of heated water is removed from the tank.

The replacement water delivered to the tank20through the cold water connection pipe78has a first kinetic energy state due to the source pressure of the water system. As the replacement water passes through the lower diffuser assembly40A, the kinetic energy head will be reduced from the first kinetic energy state to a second, lower kinetic energy state, so that that flow of water out of the diffuser40A is generally laminar, thereby minimizing the mixing within the tank and creating the desired thermal stratification.

In some embodiments, when the water heater10is in the discharging mode, the flow of heated water is removed from the internal volume60of the tank20at a first temperature, and the flow of replacement water is received in the internal volume60of the tank at a second temperature. While the second temperature will generally be lower than the first temperature, the magnitude of the difference between will vary with several factors, such as the setpoint of the water heater and the source of the incoming water. Typically, the second temperature is between fifty degrees Fahrenheit and one hundred and fifty degrees Fahrenheit lower than the first temperature. For example, the second temperature may be at least one hundred degrees Fahrenheit lower than the first temperature.

When a volume of water equal to 90% of the internal volume60has been discharged, the flow of water removed from the internal volume60is at a third temperature that is close to the first temperature. In some embodiments, the third temperature in degrees Fahrenheit is at least 95% of the first temperature in degrees Fahrenheit when the water is removed from the internal volume60of the tank20.

FIGS. 5-11illustrate variations on the diffuser110illustrated inFIGS. 3-4. Each diffuser210,310,410,510,610, ofFIGS. 5-11includes a plurality of flow sections in which a cross-sectional flow area within any one of the plurality of flow sections is greater than the cross-sectional flow area within any of the plurality of flow sections arranged upstream of the said one of the plurality of flow sections.

FIGS. 5-7illustrate another exemplary embodiment of a diffuser210, with like components and features as the embodiment of the diffuser110shown inFIGS. 3-4being labeled with like reference numerals plus “100.” The diffuser210is similar to the diffuser110and, accordingly, the discussion of the diffuser110above similar applies to the diffuser210and is not restated. Rather, only differences between the diffuser110and the diffuser210are specifically noted herein, such as differences in the construction of the body of the diffuser.

The diffuser210includes a body214, a fluid inlet218, and a fluid outlet222. A flow circuit226(FIG. 7) is connected between the fluid inlet218and the fluid outlet222. The body214includes a central axis of symmetry230extending therethrough. The flow circuit226is positioned within the body214.

The body214includes a first non-planar wall243A and a second non-planar wall243B spaced away from the first non-planar wall243A. In addition, the second non-planar wall243B has a shape complimenting a shape of the first non-planar wall243A. In particular, each of the first and the second non-planar walls243A,243B are provided with a series of concentrically arranged circular crests and troughs255,256, respectively. Each of the first and second non-planar walls243A,243B includes four crests255and four troughs256. The shape of the first and second non-planar walls243A,243B may be formed by metal stamping originally flat plate members.

A cylindrical outer wall246extends between the first and second non-planar walls243A,243B. The first and second non-planar walls243A,243B and the outer wall246define an outer boundary of the diffuser210.

A height Y2of the outer boundary of the diffuser210is measured between the farthest axial ends of the first and second non-planar walls243A,243B relative to the central axis of symmetry230(e.g., the highest crest255of the first non-planar wall243A and the lowest trough256of the second non-planar wall243B). In addition, the cylindrical outer wall246defines an outer diameter X2of the outer boundary.

With particular reference toFIG. 7, the fluid inlet218is fluidly connected to the body214. The illustrated fluid inlet218is provided by a cylindrical inlet pipe254connected to the first non-planar wall243A. An end258of the inlet pipe254is spaced away from the second non-planar wall243B. The fluid inlet218is configured to receive the flow of liquid into the diffuser210.

The fluid outlet222of the diffuser210fluidly connects the body214to the internal volume60of the tank20. The illustrated fluid outlet222is provided in the cylindrical outer wall246. More specifically, the fluid outlet222includes a plurality of openings262in the cylindrical outer wall246. The fluid outlet222is configured to discharge the flow of liquid out of the diffuser210into the internal volume60of the tank20.

With continued reference to FIG.7, the diffuser210further includes a plurality of flow sections270A-270H sequentially arranged along the flow circuit226(i.e., relative to the downstream fluid flow direction). In the illustrated embodiment, the shape of the first and second non-planar walls243A,243B, as well as the fluid inlet218and the fluid outlet222, form the plurality of flow sections270A-270H. More specifically, the series of concentrically arranged circular crests255and troughs256of the first and second non-planar walls243A,243B provide transitions between adjacent ones of the plurality of flow sections270A-270H. The plurality of flow sections270A-270H are fluidly connected to each other. The diffuser210may include fewer or more series of concentrically arranged circular crests255and troughs256such that the diffuser210may include fewer or more flow sections270A-270H.

Similar to the diffuser110ofFIGS. 3-4, the fluid inlet218defines a first flow section270A of the plurality of flow sections270A-270H in which the illustrated diffuser210includes eight flow sections270A-270H. Each of the subsequent flow sections270B-270H arranged downstream of the first flow section270A (e.g., a second flow section270B, a third flow section270C, etc.) are defined by a portion of the first and second non-planar walls243A,243B.

Each of the plurality of flow sections270A-270H are arranged relative to the central axis230such that the central axis230is a common central axis of symmetry230between the flow sections270A-270H. For example, the illustrated first flow section270A of the cylindrical inlet pipe254is co-axial with the common central axis of symmetry230, and the remaining flow sections270B-270H are co-axially aligned with the cylindrical inlet pipe254.

Furthermore, each one of the plurality of flow sections270A-270H has a flow area for the flow of liquid to flow therethrough. The flow area of each flow section270B-270H is bounded by the first and second non-planar walls243A,243B. Each flow area has a cross-sectional flow area. In the illustrated embodiment, the cross-sectional flow area within the first flow section270A is a circular shape. The cross-sectional flow area within each one of the remaining flow sections270B-270H (e.g., second flow section270B, eighth flow section270H, etc.) is a non-planar annular shape.

In contrast to the flow sections170B-170H of the diffuser110, each of the flow sections270B-270H of the diffuser210have a non-constant cross-sectional area. The cross-sectional flow area within any one of the plurality of flow sections270A-270H is, however, greater than the cross-sectional flow area within any of the plurality of flow sections270A-270H arranged upstream of said one of the plurality of flow sections270A-270H. In other words, the size of the cross-sectional flow area anywhere along the eighth flow section270H is greater than the size of the cross-sectional flow area anywhere along the seventh flow section270G which is greater than the size of the cross-sectional flow area anywhere along the sixth flow section270F, and so on and so forth. Accordingly, the size of the cross-sectional flow area anywhere along a terminal one of the flow sections270A-270H (e.g., the eighth flow section270H) is greater than the size of the cross-sectional flow area anywhere along the remaining flow sections270A-270H. As a result, the flow area along the flow circuit226progressively increases, so that the mean fluid velocity progressively decreases as water flows along the flow circuit226.

Each flow section270A-270H is arranged to direct the flow of liquid through the diffuser210along a predetermined flow direction282A-282C. More specifically, the first and second non-planar walls243A,243B are positioned relative to each other such that the flow of liquid alternates direction relative to the common central axis of symmetry230. For example, in the illustrated embodiment, the first flow section270A is configured to direct the flow of liquid into the diffuser210along a first flow direction282A that is co-axial with the common central axis of symmetry230. The second flow section270B is configured to direct the flow of liquid into the diffuser210along a second flow direction82B that is different than the first flow direction282A. The third flow section270C is configured to direct the flow of liquid into the diffuser210along a third flow direction282C that is different than the second flow direction282B. In the illustrated embodiment, the second flow direction282B and the third flow direction282C each have an axial component and a radial component. The axial component of the second flow direction282B is opposite the first flow direction282A, and the axial component of the third flow direction282C is aligned with the first flow direction282A. Accordingly, the flow sections270A-270H are arranged such that the flow of liquid through the diffuser210alternates along the second and the third flow directions282B,282C.

The fluid outlet222is configured to direct the flow of liquid along an outlet flow direction282D. The outlet flow direction282D may be the same or different than the first flow direction282A, the second flow direction282B, and/or the third flow direction282C. For example, in the illustrated embodiment, the fluid outlet222is configured to direct the flow of liquid along the outlet flow direction282D that is perpendicular to the first flow direction282A.

FIGS. 8-9illustrate another exemplary embodiment of the diffuser310, with like components and features as the embodiment of the diffuser110shown inFIGS. 3-4being labeled with like reference numerals plus “200.” The diffuser310is similar to the diffuser110and, accordingly, the discussion of the diffuser110above similar applies to the diffuser310and is not restated. Rather, only difference between the diffuser110and the diffuser310are specifically noted herein, such as differences in the baffles and the position of the plurality of openings defining the fluid outlet.

Rather than three of the cylindrical baffles374B,374D,374F extending from the planar wall342positioned at the first end334, the body314of the diffuser310further includes a plate member352positioned within the body314. Each of the cylindrical baffles374B,374D,374F extend from the plate member352toward the opposite planar wall342, while the cylindrical baffles374A,374C,374E still extend from planar wall342. In addition, the plate member352is spaced axially away from the planar wall342relative to the central axis of symmetry330. As such, it is the plate member352, not the planar wall342positioned at the first end334, that forms a portion of the flow sections370B-370G.

Furthermore, rather than the openings362of the fluid outlet322being positioned on the cylindrical outer wall346, the openings362are positioned on the planar wall342positioned at the first end334. As such, the fluid outlet322is configured to direct the flow of liquid along the outlet flow direction382D that is aligned with the second flow direction382B. In addition, the openings362are of different sizes, and have a uniform spacing in a radial direction relative to the central axis of symmetry330.

FIG. 10Aillustrates another exemplary embodiment of the diffuser410with like components and features as the embodiment of the diffuser310shown inFIGS. 8-9being labeled with like reference numerals plus “300.” The diffuser410is similar to the diffuser310and, accordingly, the discussion of the diffuser310above similar applies to the diffuser410and is not restated. In particular, the diffuser410ofFIG. 10Aillustrates a different position of the openings462on the cylindrical outer wall446, rather than on the planar wall342.

FIG. 10Billustrates another exemplary embodiment of the diffuser110with like components and features as the embodiment of the diffuser110shown inFIGS. 3-4being labeled with like reference numerals plus “400.” The diffuser510is similar to the diffuser110and, accordingly, the discussion of the diffuser110above similar applies to the diffuser110and is not restated. In particular, the diffuser510ofFIG. 10Billustrates a variation in height Y5of the outer boundary of the diffuser510. The height Y5of the diffuser510is less than the height X1of the diffuser110.

FIG. 11illustrates another exemplary embodiment of the diffuser610, with like components and features as the embodiment of the diffuser110shown inFIGS. 3-4being labeled with like reference numerals plus “500.” The diffuser610is similar to the diffuser110and, accordingly, the discussion of the diffuser110above similar applies to the diffuser610and is not restated. Rather, only difference between the diffuser110and the diffuser610are specifically noted herein, such as differences in the construction of the body and the flow sections.

The diffuser610includes a body614, a fluid inlet618, and a fluid outlet622. A flow circuit626is connected between the fluid inlet618and the fluid outlet622. The body614includes a central axis of symmetry630extending therethrough. The flow circuit626is positioned within the body614.

The body614extends between a first end634and a second end638. In the illustrated embodiment, the body614includes a plurality of planar walls644,645spaced apart along the central axis of symmetry. The planar wall644has a circular shape, and the planar walls645have an annular shape. In addition, the body614includes a plurality of cylindrical inner and outer walls647A-647C,648A-648D, respectively, extending between the planar walls644,645. More specifically, each of the cylindrical inner walls647A-647C extend from one of the annular planar walls645toward another of the annular planar walls645. Each of the cylindrical outer walls648A-648D extends from one of the annular planar walls645toward another of the annular planar walls645. Some of the annular planar walls645and a portion of each of the outer walls648A-648D define an outer boundary of the diffuser610. In addition, the circular planar wall644, some of the annular planar walls645, and a portion of each of the cylindrical inner walls647A-647C define an inner boundary of the diffuser610. A size (e.g., diameter) of each of the outer boundary and the inner boundary increases from the first end634to the second end638relative to the downstream fluid flow direction.

A height Y6of the outer boundary of the diffuser610is measured between the first end634and the second end638. In the illustrated embodiment, two of the annular planar walls645spaced farthest apart define the height Y6.

The fluid inlet618are the fluid outlet122are fluidly connected to the body614. The illustrated fluid inlet618is a cylindrical inlet pipe654received through the annular planar wall645at the first end634of the body614. An end658of the fluid inlet618is spaced away from the circular planar wall644. The fluid outlet622may be provided in the cylindrical outer wall648D and/or one of the annular planar walls645. The fluid outlet622may include one or more openings.

The diffuser610further includes a plurality of flow sections670A-670H sequentially arranged along the flow circuit626(i.e., relative to the downstream fluid flow direction). In the illustrated embodiment, the plurality of flow sections670A-670H are formed by the plurality of planar walls644,645and the plurality of cylindrical inner and outer walls647A-647C,648A-648D. More specifically, a portion of one of the cylindrical inner walls647A-647C or a portion of one of the cylindrical outer walls648A-648D fluidly separates two sequentially arranged ones of the plurality of flow sections670A-670H. The plurality of flow sections670A-670H are fluidly connected to each other. The diffuser610may include fewer or more annular planar walls645, cylindrical inner walls647A-647C, and cylindrical outer walls648A-648D such that the diffuser610may include fewer or more flow sections670A-670H.

Similar to the diffuser110ofFIGS. 3-4, the fluid inlet618defines a first flow section670A of the plurality of flow sections670A-670H in which the illustrated diffuser610includes eight flow sections670A-670H. The subsequent flow sections670B-670H arranged downstream of the first flow section670A (e.g., a second flow section670B, a third flow section670C, etc.) may be defined by the fluid inlet618and a portion of the cylindrical inner wall647A, one of the cylindrical inner walls647A-647C and one of the cylindrical outer walls648A-648D, or a portion of the cylindrical outer wall648C and the cylindrical outer wall648D. For example, the second flow section670B is defined between the cylindrical inlet pipe654and a portion of the cylindrical inner wall647A. The third flow section670C is defined between the cylindrical inner wall647A and the cylindrical outer wall648A. The eighth flow section670H is defined between the portion of the cylindrical outer wall648C and the cylindrical outer wall648D.

Each of the plurality of flow sections670A-670H are arranged relative to the central axis of symmetry630such that the central axis of symmetry630is a common central axis of symmetry630between the flow sections670A-670H. For example, the illustrated first flow section670A of the cylindrical inlet pipe654is co-axial with the common central axis of symmetry630, and the remaining flow sections670B-670H are co-axially aligned with the cylindrical inlet pipe654.

Furthermore, each one of the plurality of flow sections670A-670H has a cross-sectional flow area for the flow of liquid to flow therethrough. In the illustrated embodiment, the cross-sectional flow area within the first flow section670A is a circular shape. The cross-sectional flow area within each one of the remaining flow sections670B-670H (e.g., second flow section670B, eighth flow section670H, etc.) is an annular shape.

The cross-sectional flow area within any one of the plurality of flow sections670A-670H is greater than the cross-sectional flow area within any of the plurality of flow sections670A-670H arranged upstream of said one of the plurality of flow sections670A-670H. In other words, the size of the cross-sectional flow area of the eighth flow section670H is greater than the size of the cross-sectional flow area of the seventh flow section670G which is greater than the size of the cross-sectional flow area of the sixth flow section670F, and so on and so forth. Accordingly, the size of the cross-sectional flow area of a terminal one of the flow sections670A-670H (e.g., the eighth flow section670H) is greater than the size of the cross-sectional flow area of any of the remaining flow sections670A-670H.

Each flow section670A-670H is arranged to direct the flow of liquid through the diffuser610along a predetermined flow direction682A-682C. More specifically, the cylindrical inlet pipe654and the plurality of cylindrical inner and outer walls647A-647C,648A-648D are spaced from the respective planar walls644,645such that the flow of liquid alternates direction relative to the common central axis of symmetry630. For example, in the illustrated embodiment, the first flow section670A is configured to direct the flow of liquid into the diffuser610along a first flow direction682A that is co-axial with the common central axis of symmetry630. The second flow section670B is configured to direct the flow of liquid into the diffuser610along a second flow direction682B that is different than the first flow direction682A. The third flow section670C is configured to direct the flow of liquid into the diffuser610along a third flow direction682C that is different than the second flow direction682B. In the illustrated embodiment, the second flow direction682B is opposite the first flow direction682A, and the third flow direction682C is aligned with the first flow direction682A. Accordingly, the flow sections670A-670H are arranged such that the flow of liquid through the diffuser610alternates along the second and the third flow directions682B,682C.

The fluid outlet622is configured to direct the flow of liquid along an outlet flow direction682D. The outlet flow direction682D may be the same or different than the first flow direction682A, the second flow direction682B, and/or the third flow direction682C.

Thus, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following claims.