Stratification tank, water system comprising such a stratification tank, and method of operating such a water system

Abstract

Stratification tank, comprising: an elongate internal volume; a first inlet configured to provide to be heated liquid to a bottom section; a first outlet that is configured to allow to be heated liquid to be extracted from the bottom section; a second inlet that is configured to allow heated liquid to be introduced back into the tank in a middle section; and a second outlet that is configured to allow heated liquid to be extracted from a top section, wherein the stratification tank is configured to be used in a lying orientation and comprises a lower baffle plate that extends in the longitudinal direction of the internal volume and is arranged in the bottom section and downstream of the first inlet, to thereby, during use, deflect a flow of liquid out of the first inlet and promote a uniform inflow of liquid into the bottom section. The invention further relates to a water system comprising such a stratification tank, and to a method of operating such a water system. [Fig. 3]

Description

Title: Stratification tank, water system comprising such a stratification tank, and method of operating such a water system Description: The invention is related to a stratification tank. The invention is furthermore related to a water system comprising such a stratification tank, and to a method of operating such a water system. Thermal stratification is the tendency of a liquid, e.g. water, to form thermal layers of different temperatures in a storage tank. These thermal layers are also known as stratification layers. Stratification results from differences in density caused by temperature variations. When water is heated, its density decreases and it becomes less dense than the cooler water below it. This causes the heated water to rise to the top of the tank, forming a layer of hot water at the top side. At the same time, the cooler water from the bottom of the tank sinks to the bottom, forming a layer of cold water at the bottom side. The layers of water in the tank remain stratified because of the difference in density between the hot and cold water. The density difference creates a barrier to mixing, and the layers will remain separate as long as there is no external force that can cause them to mix, such as stirring or turbulence. This stratification can be maintained for a long time, as long as there is no external disturbance, allowing the temperature difference between the layers to remain significant. Dependent on the type of hot water device, itmay be desirable to prevent mixing of the thermal layers. Such mixing may especially occur when water is introduced into the tank, or when water is withdrawn from the tank. After all, the flow in or out of the tank may cause a turbulence inside the tank, that results in disturbance of the thermal layers that are already present inside the tank. It is therefore desired that the stratification is not disturbed, while at the same allowing water to be introduced into the tank and / or removed via the outlet. In this way, mixing of thermal layers is prevented, and an efficient storage of heat energy is obtained. As becomes clear from the explanation and discussion on stratification above, mixing of water of neighbouring thermal layers is to be prevented in order to maintain stratification and associated beneficial thermal efficiency. In order to reduce the risk of mixing of water of neighbouring thermal layers, it is common practice to place stratification tanks in an upright, i.e. vertical, orientation, thereby minimizing a surface area of an interface between neighbouring stratification layers. However, a disadvantage of an upright orientation of the stratification tank is that it requires sufficient height to be available at the location of installation. This is sometimes a challenge, especially if the stratification tank is to be placed at an upper floor of a building having a gable roof superstructure. There is a need for stratification tanks that allow for more versatile placement. In particular, there is a need for a stratification tanks that may be horizontally oriented, i.e. in a lying orientation. A horizontal oriented stratification tank would allow for a more versatile placement inside the building, such as in a corner section enclosed between the upper floor and the inclined roof. It is even conceivable that such a lying stratification may be installed behind a partition wall, out of sight and not, or only minimally, interfering with floor area where it is high enough for an average adult to stand up. An objective of the present invention is to provide a stratification tank, that is improved relative to the prior art and wherein at least one of the above stated problems is obviated or alleviated. Said objective is achieved with the stratification tank, configured to create and maintain stratification of a heated liquid, in particular tap water, that is receivable in said tank, according to claim 1 of the present invention, said stratification tank comprising: - an elongate internal volume that is configured to receive and store the heated liquid in thermal layers, wherein said internal volume has a length and a width, and comprises a bottom section, a middle section, and a top section; - a first inlet that is configured to provide to be heated liquid to the bottom section of the internal volume; - a first outlet that is configured to allow to be heated liquid to be extracted from the bottom section; - a second inlet that is configured to allow heated liquid to be introduced back into the tank in the middle section; - a second outlet that is configured to allow heated liquid to be extracted from the top section, - wherein the stratification tank is configured to be used in a lying orientation, wherein a lower interface between the bottom section and the middle section, and an upper interface between the middle section and the top section, extend in a longitudinal direction of the internal volume; and - wherein the stratification tank comprises a lower baffle plate, that extends in the longitudinal direction of the internal volume, wherein said lower baffle plate is arranged in the bottom section and downstream of the first inlet, to thereby, during use, deflect a flow of liquid out of the first inlet and promote a uniform, and preferably laminar, inflow of liquid into the bottom section. The stratification tank is configured to be used in a lying orientation. As discussed above, this allows for versatile placement in spaces with a limited available height, such as in a corner section enclosed between the upper floor and the inclined roof at an upper floor of a building having a gable roof superstructure. Stratification tanks that are arranged in a lying orientation have a relatively large surface area of interfaces between neighbouring stratification layers. Consequently, it is a challenge to prevent disturbance of the stratification layers. After all, mixing of these thermal layers is prevented to obtain and maintain efficient storage of heat energy in the stratification tank. Such mixing of thermal layers may especially occur when water is introduced into the tank, or when water is withdrawn from the tank. After all, the flow in or out of the tank may cause a turbulence inside the tank, that results in disturbance of the thermal layers that are already present inside the tank. In order to prevent mixing of thermal layers due to the inflow of water into the internal volume, the stratification tank according to the invention comprises a lower baffle plate. This lower baffle plate extends in the longitudinal direction of the internal volume. It is arranged in the bottom section and downstream of the first inlet. As a result water flowing out of the first inlet and into the interior volume is deflected by the lower baffle plate. In this way, the lower baffle plate promotes a uniform, and preferably laminar, inflow of liquid into the bottom section, thereby reducing the risk of mixing of thermal layers caused by the inflow of water via the first inlet. More in particular, the lower baffle plate promotes an inflow of liquid at a substantially reduced and uniform velocity. Thus, despite the stratification tank being configured to be used in a lying, i.e. horizontal orientation, and the resulting large surface area of interfaces between neighbouring stratification layers compared to vertically oriented stratification tanks, the use of a lower baffle plate provides the surprising effect that disturbance of the stratification layers is effectively reduced when water is introduced into the tank, and / or withdrawn therefrom. The stratification tank according to the invention prevents mixing of thermal layers. The lower baffle plate reduces the risk that the stratified layers of water are disturbed by water leaving or entering the stratification tank. Because a high level of stratification is guaranteed in this way, there is no need to anticipate for a large amount of heat loss due to mixing. Consequently, the use of a lower baffle plate allows for a reduction of the volume of the stratification tank, compared to conventional stratification tanks that do need to account for mixing. A stratification tank having a smaller volume is especially advantageous for a stratification tank that is configured to be used in a lying orientation. After all, a smaller stratification tank allows more versatile placement, also in limited spaces. As discussed above, such lying stratification tanks may be placed in a corner section enclosed between the upper floor and the inclined roof, such as behind a partition wall, out of sight and not, or only minimally, interfering with floor area where it is high enough for an average adult to stand up. It is remarked that the stratification tank may be passivated or pickled in an upright orientation, allowing passivation of pickling fluid to pass also along the lower baffle plate and reach all necessary areas. The invention furthermore relates to water system, configured to store water in a stratified manner, comprising: - a stratification tank according to the invention; - a heating circuit with a heat exchanger that is in fluid connection with the first outlet to allow to be heated liquid to be extracted from the bottom section of the tank, and the second inlet to allow liquid, after being heated by the heat exchanger, to be provided back into the tank; and - a controller configured to actively control a flow of liquid through the heating circuit. The invention furthermore relates to a method of operating a water system according to the invention, comprising the steps of: - when heated water is extracted at the top section via the second outlet, simultaneously providing to be heated water to the bottom section via the first inlet; - measuring a temperature of the water inside the interior volume with a temperature sensor that is arranged at a predetermined level; and - actively controlling the flow of liquid through the heating circuit, comprising the step of delaying heating of the to be heated water provided via the first inlet until the temperature sensor measures a predetermined temperature at the predetermined level. When heated water is extracted at the top section via the second outlet, simultaneously to be heated water is provided to the bottom section via the first inlet. As a result of hot water being extracted at the top section and cold water entering, the cold water pushes the hotter water above it gradually upwards. Heating of the to be heated (cold) water in the lower section is delayed until the water temperature at the upper baffle plate has reached a predetermined temperature, e.g. of approximately 25 °C. A temperature of approximately 25 °C is close to an initial loading temperature and supply temperature of a heat pump, that is a preferred embodiment of the heat exchanger in the heating circuit. This delay in heating causes the hot water above the upper baffle plate to remain intact as much as possible, and the water below the upper baffle plate is charged with heat gradually. The charged water returning from the heat pump has a tendency to stay between the hotter upper layer and the colder bottom layer. Only in the final stage of charging, when the temperatures of the supply and the overlying layers come close to each other, water will slowly mix up the hotter layers above and rise to the final temperature through free convection. This ensures that the supply temperature of the heat pump can remain as low as possible. Preferred embodiments are the subject of the dependent claims. The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, and in particular the aspects and features described in the attached dependent claims, may be an invention in its own right that is related to a different problem relative to the prior art. In the following description preferred embodiments of the present invention are further elucidated with reference to the drawing, in which: Figure 1 is a perspective view of a stratification tank according to a first preferred embodiment of the invention; Figure 2 is a perspective view of the stratification tank of Figure 1, that is partially opened to show the interior; Figure 3 is a detailed cross-sectional perspective view of the stratification tank of Figures 1 and 2; Figure 4 is a schematic overview of a water system comprising the stratification tank of Figures 1-3; Figures 5A and 5B show schematic cross sectional side views with a temperature gradient of the water inside the stratification tank when fully charged (Fig. 5A) and when ready to be recharged (Fig. 5B); and Figure 6 is a cross sectional top view of the stratification tank according to a second preferred embodiment, showing the outlines of an alternative upper baffle plate. A stratification tank 1 according to a first preferred embodiment is shown in the perspective views of Figures 1-3. The stratification tank 1 is configured to create and maintain stratification of a heated liquid, in particular tap water, that is receivable in said tank 1. The stratification tank 1 comprises an elongate internal volume 2 that is configured to receive and store the heated liquid in thermal layers. The internal volume 2 has a length L and a width W, and comprises a bottom section B, a middle section M, and a top section T (indicated in Figures 5A and 5B). In the preferred embodiments, the stratification tank 1 comprises is tubular shape, and consequently the widthW of the internal volume 2 corresponds to an inner diameter D of the tank 1. In some embodiments, the length L is larger than the width W. The stratification tank 1 further comprises a first inlet 3, a first outlet 4, a second inlet 5, and a second outlet 6. The first inlet 3 is configured to provide to be heated liquid (e.g., unprocessed liquid, unheated liquid, cold water, tap water) to the bottom section B of the internal volume 2. The first outlet 4 is configured to allow to be heated liquid to be extracted from the bottom section B. The first inlet 3 and the first outlet 4 are only visible in the cross sectional view of Figure 3. The second inlet 5 is configured to allow heated liquid to be introduced back into the interior volume 2 of the tank 1 in the middle section M. The second outlet 6 is configured to allow heated liquid to be extracted from the top section T for use. As can be seen in the Figures, the stratification tank 1 is configured to be used in a lying orientation, wherein a lower interface IL between the bottom section B and the middle section M, and an upper interface lu between the middle section M and the top section T, extend in a longitudinal direction of the internal volume 2. The longitudinal direction extends in the length L direction of the internal volume 2. The lower interface IL and upper interface lu are imaginary planes, schematically indicated in Fig. 5A only. The stratification tank 1 comprises a lower baffle plate 7, that extends in the longitudinal direction of the internal volume 2. The lower baffle plate 7 is arranged in the bottom section B and downstream of the first inlet 3, to thereby, during use, deflect a flow of liquid out of the first inlet 3 and promote a uniform, and preferably laminar, inflow of liquid into the bottom section B. More in particular, the lower baffle plate 7 promotes an inflow of liquid at a substantially reduced and uniform velocity. For example, at a maximum flow rate of 15 L / min at the first inlet 3, the lower baffle plate 7 is able to slow down the incoming stream of cold water at the opposite outflow passages 10 to an average velocity of less than 0,1 m / s. The flow at the opposite outflow passages 10 will therefore be laminar. In the shown preferred embodiments, the lower baffle plate 7 has an elongate shape with a length L7 extending in the longitudinal direction of the internal volume 2, and a width W7 extending in the transverse direction of the internal volume 2. As can be best seen in Figs. 2 and 3, the width W7 of the lower baffle plate 7 in the shown preferred embodiments connects opposite inner wall segments of the interior volume 2 in the bottom section B. In this way, the incoming flow of water via the first inlet 3 cannot leave the area below the lower baffle plate 7 on the longitudinal sides. Instead, the flow of incoming liquid is forced to flow in the longitudinal direction first, thereby increasing the path of travel in an area that is confined below the lower baffle plate 7. If the stratification tank 1 comprises a tubular shape, it has only one continuous inner wall with a circular shape, and the opposite inner wall segments are different segments of the single inner wall. It is remarked that the stratification tank may be passivated or pickled in an upright orientation, allowing passivation of pickling fluid to pass also along the lower baffle plate and reach all necessary areas. lf a similar lower baffle plate, connecting opposite inner wall segments, would be used in a stratification tank that is intended for use in an upright orientation, this could result in difficulties for the pickling and rinsing fluid to reach all areas and not having an optimal pickling / rinsing and passivation result. The detailed view of Fig. 3 shows that the lower baffle plate 7 in the shown embodiment comprises downward directed longitudinal side edges 8. The downward directed side edges deflect the flow of incoming liquid downwards at the longitudinal sides, reducing the risk of a sideward escape of said liquid in between any gaps between successive spot welds 9. The length L7 of the lower baffle plate 7 is shorter than the length L of the internal volume 2 to define at least one longitudinal outflow passage 10 that is oriented in the longitudinal direction of the internal volume 2. In the shown preferred embodiment, two opposite outflow passages 10 are shown. They allow water that has been entered via the first inlet 3, and successively deflected by the lower baffle plate 7, to flow further into the bottom section B of the interior volume 2. Staying first in the area confined below the lower baffle plate 7, promotes a uniform, and preferably laminar, inflow of liquid into the bottom section B. The length L7 is a compromise between two factors. On the one hand, a large length L7 results in a lower baffle plate 7 having a large surface area, thereby forming a barrier that prevents interference between cold water that is introduced via the first inlet 3 below the lower baffle plate 7, and the warmer water above said lower baffle plate 7. On the other hand, with reference to the previous paragraph, the water will flow into the bottom section B at the two opposite outflow passages 10. It is advantageous if there is an offset between the outflow passages 10 and an inner wall of the domes 26 of the interior volume 2 downstream of said outflow passages 10 that is of sufficient length to allow the flow to settle and slow down in a free space before it reaches the domes 26. In this way it is prevented that the domes 26 deflect the flow upwards. In other words: if the outflow passages 10 of the lower baffle plate 7 would end too close to the domes 26, the domes 26 may deflect the flow towards the middle section M. In the shown embodiment, the stratification tank 1 further comprises an upper baffle plate 11. The upper baffle plate 11 is plate shaped and defines an imaginary plane that extends in the longitudinal direction of the internal volume 2. The upper baffle plate 11 defines a boundary between the middle section M and the top section T, and is arranged downstream of the second inlet 5, to thereby, during use, deflect a flow of liquid out of the second inlet 5 and promote a uniform, and preferably laminar, inflow of heated liquid into the middle section M. Both the lower baffle plate 7 and the upper baffle plate 11 may comprise grooves, ridges, or other features to promote an uniform, and preferably laminar, flow. As shown in Figure 3, the upper baffle plate 11 has a top plate 11a and a bottom plate 11b, that are arranged parallel to each other at a vertical offset. The second inlet 5 is attached to the bottom plate 11b of the upper baffle plate 11, so that heated liquid that is introduced back into the interior volume 2 of the tank 1 in the middle section M is introduced in between the top plate 11a and the bottom plate 11b of the upper baffle plate 11. As can be best seen in the cross sectional view of Fig. 3, the second inlet 5 is directed upward, and the upper baffle plate 11 is arranged above the second inlet 5. When the stratification tank is arranged in the lying orientation, the upper baffle plate is arranged in a range of 30 70 % of a height of the internal volume, and preferably in a range of 40 60 % of the height of the internal volume. ln the embodiment shown in Figs. 2, 3, 5A and 5B, the upper baffle plate 11 is arranged substantially halfway the height of the internal volume 2. The above mentioned ranges ensure that the top section T is large enough to provide a sufficient buffer capacity of hot water. Moreover, especially if the stratification tank 1, and the interior volume 2 thereof, comprises is tubular shape, placing the upper baffle plate 11 about halfway provides the most space for the upper baffle plate 11. ln this way, a relatively large upper baffle plate 11 may be applied, thereby increasing the effectiveness of the upper baffle plate 11. ln the first preferred embodiment shown in Figs. 1-3, the upper baffle plate 11 is embodied as a circular plate. However, according to a second preferred embodiment, the plate shaped upper baffle plate 11 has an elongate shape with a length L extending in the longitudinal direction of the internal volume 2, and a width W11 extending in the transverse direction of the internal volume 2. Figure 6 shows a top cross sectional view of the stratification tank 1 according to this second preferred embodiment, that only differs from the first preferred embodiment by the shape of the upper baffle plate 11. Only the contour C of the upper baffle plate 11 is indicated, allowing a free view of the lower baffle plate 7 and the second inlet 5. Similar reference numbers apply to the similar features for both embodiments. The upper baffle plate 11 according to both the first and second preferred embodiment comprise longitudinal sides 12 that end at a transverse offset 13 relative to opposite inner wall segments in the middle section M. The length L11 of the upper baffle plate 11 is shorter than the length L of the internal volume 2. A width W11 of the upper baffle plate 11 decreases towards as least one longitudinal end 14 of said upper baffle plate 11. At least a part of the longitudinal sides of the upper baffle plate 11 comprises downward directed side edges. These edges extend at least in the part where the transverse offset 12 relative to opposite inner wall segments in the middle section M reaches a minimum value. ln Fig. 6, a part where the downward directed side edges may be present is schematically indicated with a solid line 15 The internal volume 2 comprises an elongate shape. lt preferably comprises a transverse cross sectional area extending in a vertical direction that is smaller than 50% of a longitudinal cross sectional area extending in a horizontal direction. The stratification tank 1 preferably further comprises a heating element 23 that is arranged in the middle section M, said heating element 23 having a controller 22. ln Fig. 4, the stratification tank 1 is shown as part of a water system 28 that is configured to store water in a stratified manner. The water system 28 furthermore comprises a secondary heating circuit 29 with a heat exchanger 30 that is in fluid connection with the first outlet to allow to be heated liquid to be extracted from the bottom section B of the tank 2, and the second inlet 5 to allow liquid, after being heated by the heat exchanger 30, to be provided back into the tank; and a controller 19 configured to actively control a flow of liquid through the secondary heating circuit 29. In Figure 3, the position of the heat exchanger 30 is indicated with an arrow pointing towards a cavity wherein the heat exchanger 30 is arranged. The heat exchanger 30 itself is not shown in detail, but it comprises fluidly separate circuits. A first circuit circulates water through the stratification tank 1 from the bottom section B of the stratification tank 1, through the heat exchanger 30, and back to the upper baffle plate 11. A second circuit circulates a working fluid (e.g., water, glycol solution, etc.) from the heat source 16, through the heat exchanger 30 and back to the heat source 16. In the example shown, the second circuit is configured to flow through the heat exchanger 30 in a counter-flow arrangement. ln some embodiments, the first and second circuits may flow through the heat exchanger 30 in a parallel flow arrangement. The method of operating the water system 28 is now described in more detail with reference to the Figures. When heated water is extracted at the top section T via the second outlet 6 (flow indicated with arrow F7 in Figs. 2 and 3), the method simultaneously provides to be heated water (arrow F1 in Fig. 3) to the bottom section B via the first inlet 3. The temperature of the water inside the interior volume 2 is measured with a temperature sensor 31 (Figs. 5A and 5B) that is arranged at a predetermined level. The flow of liquid through the heating circuit 29 is actively controlled, comprising the step of delaying heating of the to be heated water provided via the first inlet 3 until the temperature sensor 31 measures a predetermined temperature Tp at the predetermined level Lp. ln Figs. 5A and 5B, the tank 1 is schematically shown in a cross sectional side view, and the dashed line 27 indicated a temperature profile. For example, in Figs. 5A and 5B, the temperature in the top section TT may be about 55 °C. ln Fig. 5A, the water in the interior volume 2 is fully charged with heat, and the temperature gradient in the middle section M and bottom section B only shows a very limited decline in temperature. For example the temperature in the bottom section TB may still be about 50 °C in Fig. 5A. lf hot water is extracted from the top section T, and cold water is simultaneously introduced into the bottom section B, the temperature in the bottom section B, and eventually also in the middle section M, will gradually decrease. ln Fig. 5B, the temperature in the bottom section TB and in the middle section TM have decreased to about 10 15 °C. If the tank 1 comprises well stratified thermal layers, there is a relatively steep temperature gradient with the decrease in temperature from TT = 55 °C to TM = 10 15 °C , as shown in Fig. 5B. For this reason, the predetermined level Lp at which the temperature sensor 31 is arranged is at a level at or near the upper baffle plate 11. Preferably, the predetermined level Lp at which the temperature sensor 31 is arranged is above the upper baffle plate 11. For example, the predetermined level Lp at which the temperature sensor 31 is arranged may be within 0.1%-10% of the height (or diameter D in the case of a cylinder) of the inner volume of the stratification tank 1 above the upper baffle plate 11. In a specific example, the predetermined level Lp at which the temperature sensor 31 is arranged may be within 1 mm to 50 cm above the upper baffle plate 11. In this way, it may be guaranteed that heating of the water in the middle section M only starts when the water in the middle section M is cold enough. lf heating would start too early, it could occur that cold water retracted from the bottom section B is heated to a temperature that is still below the actual temperature TM in the middle section M at the second outlet 5. Upon the temperature sensor 31 measuring the predetermined temperature Tp at the predetermined level Lp, cold water is extracted from the bottom section B via the first outlet 4 (flow indicated with arrow F2 in Fig. 3) and is pumped by pump 25 via arrow F3 (in Fig. 3) towards the heat exchanger 30. This heat exchanger 30 may be a plate heat exchanger. ln other examples, the heat exchanger 30 may be another type of heat exchanger such as a double-pipe heat exchanger, shell and tube heat exchanger, or any other suitable heat exchanger. ln Fig. 3, the flow F4 of water drawn from the bottom section B of the stratification tank 1 through this heat exchanger 30 is schematically shown. As described in more detail below, the flow of a heated working fluid may flow through the heat exchanger 30 in an opposite direction from conduit 18 to conduit 17 to heat the water. For example, if the temperature sensor 31 measures a temperature decrease of about 5 °C after draw offs, recharging of the stratification tank 1 may be started. At this point in time, the temperature of the water entering the middle section M of the stratification tank 1 at the second outlet 5, le. via the upper baffle plate 11, will be less or ultimately the same as the temperature inside the stratification tank 1 near the upper baffle plate 11. The controller 19 may be configured to actively control a flow of liquid through the primary heating circuit 32 when the temperature sensor 31 measures a temperature drop of 5 °C (e.g. from 55 to 50 oC). The primary heating circuit 32 comprises a heat source 16, such as an external heat pump or other type of heat source (e.g., an electric heating element, a gas burner, or the like). Cold water retracted from the bottom section B, that may be about 10 0C, is heated by about 5 °C by a heat exchanger 30, thereby reaching about the temperature of the water (Le. 15 °C) near the upper baffle plate 11 in the middle section M, where the heated water is successively released into the stratification tank 1. In this example, the temperature profile in fig 5B (dashed line) ideally initially extends between the points of 50 °C at the horizontal level of temperature sensor 31, and 15 °C at the outlet level of the upper baffle plate 11, where recharging of the stratification tank 1 takes place. The water system 28 comprises the stratification tank 1 and two fluidly isolated heating circuits, including a primary heating circuit 32 and a secondary heating circuit 29. The primary heating circuit 32 comprises a heat source 16. As shown in Fig. 4, the heat source 16 of the primary circuit 32 may be an external heat pump or other type of heat source (e.g., an electric heating element, a gas burner, or the like), that is in fluid connection with the conduits 17 and 18. The flow in the primary circuit 32 is indicated with arrows P1 and P2 (Fig. 2). A controller 19 is communicatively connected 20 (either via a wire or wireless) to the temperature sensor 31 inside the stratification tank 1. The controller 19 is configured to control the pump 33 in the primary circuit 32 to circulate a heated working fluid through the heat exchanger 30. The secondary heating circuit 29 also comprises the heat exchanger 30, that is a shared component with the primary heating circuit 32. The secondary heating circuit 29 furthermore comprises a pump 25, and a non-return valve 24. In the preferred embodiment, the secondary heating circuit 29 is also arranged inside a housing 34 of the stratification tank 1, allowing the secondary heating circuit 29 and its components to be insulated and well protected. Thus, in the shown preferred embodiments, the stratification tank 1 comprises the (secondary) heating circuit with a heat exchanger 30 that is in fluid connection with the first outlet 4 to allow to be heated liquid to be extracted from the bottom section B of the tank 1, and the second inlet 5 to allow liquid, after being heated by the heat exchanger 30, to be provided back into the tank 1. Alternatively, and not shown, the water system 28 may comprises such a heating circuit with a heat exchanger that is arranged external of the housing 34 of the stratification tank 1. In a further alternative, the first outlet 4 may directly (or via pump 25 or pump 33) be coupled to the heat source 16 which in turn may directly (or via pump 25 or pump 33) be coupled to the second inlet 5. After water being heated in the heat exchanger 30, it flows via a non- return valve 24 in the direction of arrows F5 and F6 to be introduced back into the middle section M of the interior volume 2 at the second inlet 5. Although they show preferred embodiments of the invention, the above described embodiments are intended only to illustrate the invention and not to limit in any way the scope of the invention. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims. Furthermore, it is particularly noted that the skilled person can combine technical measures of the different embodiments. The scope of protection is defined solely by the following claims.

Claims

1. Stratification tank, configured for creating and maintaining stratification of a heated liquid, in particular tap water, that can enter the tank be received, comprising: - an oblong internal volume configured for receiving and storing the heated fluid in thermal layers, where the internal volume is has length and a width, and a lower part, a middle part and a upper part comprises; - a first inlet configured for supplying to fluid at the lower part of the internal volume; - a first outlet configured in such a way to vent fluid can be extracted from the lower part; - a second inlet configured in such a way that the fluid can be introduced back into the tank in the middle section; - a second outlet configured in such a way that the fluid is heated can be extracted from the upper part; - where the stratification tank is configured to be used in a horizontal orientation, where a lower interface between the lower part and the middle section, and a top interface between the middle section and the upper part, extending in a longitudinal direction of the internal volume; and - where the stratification tank comprises a lower guide plate, which is located extends in the longitudinal direction of the internal volume, with the lower guide plate is installed in the lower section and downstream of the first inlet, in order to, during use, to deflect a fluid flow from the first inlet and a uniform to promote the inflow of fluid into the lower part.

2. Stratification tank in accordance with claim 1, where the lower guide plate a has an elongated shape with a length that extends in the longitudinal direction of the internal volume, and a width extending in the transverse direction of the internal volume.

3. Stratification tank according to claim 2, where the width of the bottom guide plate opposing inner wall segments of the internal volume in the connects the lower part.

4. Stratification tank in accordance with claim 3, where the lower guide plate to includes downward-pointing longitudinal side edges.

5. Stratification tank according to one of claims 2-4, where the length of the lower guide plate is shorter than the length of the internal volume to at least a to define a longitudinal outflow passage that is oriented in the longitudinal direction of the internal volume.

6. Stratification tank in accordance with one of the preceding conclusions, further comprising an upper guide plate, which extends in the longitudinal direction of the internal volume, where the top guide plate: - defines a boundary between the middle part and the top deeHe;en - is installed downstream of the second inlet, in order to, during use, to deflect a fluid flow from the second inlet and a uniform inflow of To promote moist fluid in the middle section.

7. Stratification tank according to conclusion 6, where the second inlet is upwards. directed and the upper guide plate above the second inlet is installed.

8. Stratification tank in accordance with one of claims 6 or 7, where, when the The stratification tank is installed in the horizontal orientation, the top guide plate is applied in a range of 30 - 70% of the height of the internal volume, and at preference in a range of 40 - 60% of the height of the internal volume.

9. Stratification tank according to one of conclusions 6-8, where the top one guide plate has an elongated shape with a length that extends longitudinally direction of the internal volume, and a width extending in the transverse direction of the internal volume.

10. Stratification tank according to one of conclusions 6-9, where the top one guide plate comprises longitudinal sides that terminate at a transverse interval at relative to opposing interior wall segments in the middle section.

11. Stratification tank according to one of claims 6-10, where the length of the top guide plate is shorter than the length of the internal volume.

12. Stratification tank according to one of conclusions 6-11, where a width decreases from the upper guide plate to at least one longitudinal end of the top guide plate.

13. Stratification tank in accordance with one of Conclusions 6-12, where at least one part of the longitudinal sides of the upper guide plate facing downwards includes side edges.

14. Stratification tank in accordance with one of the preceding conclusions, whereby the The stratification tank has a tubular shape.

15. Stratification tank in accordance with one of the preceding conclusions, whereby the internal volume comprises a transverse cross-sectional area that extends into a vertical direction that is smaller than 50% of a longitudinal cross-sectional area that extends in a horizontal direction.

16. Stratification tank in accordance with one of the preceding conclusions, further comprising a venNarming element installed in the middle section.

17. Water system, configured for storing water on a in a stratified manner, comprising: - a stratification tank pursuant to one of the preceding claims; - a heating circuit with a heat exchanger such that in The fluid connection is connected to the first outlet to expel fluid from the bottom. part of the tank is withdrawn, and in such a way with the second inlet that liquid, after to its heat is passed through the heat exchanger, returned to the tank; and - a control unit configured for actively controlling a fluid flow through the heating circuit.

18. Method for operating a water system in accordance with conclusion 17, comprising the steps of: - when fen water is extracted from the upper part via the second outlet, the simultaneous supply of water to the lower outlet part via the first inlet; - measuring the temperature of the water within the internal volume with a temperature sensor installed at a predetermined level; and - actively controlling the fluid flow through the heating circuit, comprising the step of postponing the fenNarmen of the water to fenNarmen supplied via the first inlet until the temperature sensor a predetermined measures temperature at the predetermined level.

19. Method according to conclusion 18, whereby the predetermined level at which the temperature sensor is mounted at a level at or near the top guide plate.

20. Method in accordance with conclusion 18 or 19, whereby the predetermined level on which the temperature sensor is mounted is located above the top guide plate.

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