DE102023120333A1 - hot water tank - Google Patents

Abstract

Hot water storage tank (1), at least comprising a container (2) with a volume (4) enclosed by a container wall (3) for storing hot water (5) and a supply line (6) for cold water (7), wherein the supply line (6) extends from outside the container (2) over the container wall (3) into the volume (4) as far as an outlet (8) of the supply line (6), characterized in that the supply line (6) has a smaller first flow cross-sectional area Q1 (9) upstream of the outlet (8) and a larger second flow cross-sectional area Q2 (10) between the first flow cross-sectional area Q1 (9) and the outlet (8).

Description

The invention relates to a hot water storage tank.

Systems for providing hot water can have a hot water tank to store the heated water. Particularly when using renewable energies such as solar thermal energy, good conditions for heat generation and a demand for hot water can exist at different times. In order to be able to deliver the amount or temperature of water heated by solar thermal energy requested by a user, hot water tanks are used with which the heated water can be stored until it is used. Cold water is fed into the hot water tank and heated there, e.g. via a heat exchanger. For energy-efficient use of the hot water stored in the hot water tank, the mixing of the cold water supplied with the already heated hot water should be as minimal as possible. The volume of the hot water tank intended for storing the hot water extends from a lower area to an upper area. The hot water settles in the upper area in the known manner, while the cold water is arranged in the lower area due to its higher density.

It is known that cold water is supplied via a downpipe. The downpipe extends from the outside into the volume of the hot water tank and then runs to a lower area of the hot water tank. The cold water is thus transferred directly into the area of the hot water tank, in which the cold water stored in the hot water tank settles over time. The piece of pipe used is usually cylindrical, i.e. the flow cross-section of the piece of pipe is essentially constant. Due to the high flow speed of the incoming cold water, the cold water is mixed with the hot water in a fairly large part of the volume of the hot water tank.

It is also known to perforate the wall of the downpipe in order to reduce the flow rate of the cold water. The perforated pipe does indeed minimize the flow rate with the help of its holes, but this requires a defined length of pipe over which the holes are distributed. The cold water flows into the heated hot water over the length of the perforated area and mixes it over the height of the perforated pipe, resulting in increased mixing of the hot water.

The solutions mentioned above each lead to a certain mixing of the water, on the one hand due to the high flow velocity present, and on the other hand due to the outflow via the holes of the perforation along the extension of the downpipe.

Based on this, the object of the invention is to propose a hot water storage tank that at least partially overcomes the problems of the prior art described. In particular, the hot water storage tank is intended to achieve a lower level of mixing of the water stored in the hot water storage tank.

These objects are achieved by the features of independent patent claim 1. Further advantageous embodiments of the solution proposed here are specified in the independent patent claims. It is pointed out that the features listed in the dependent patent claims can be combined with one another in any technologically reasonable manner and define further embodiments of the invention. In addition, the features specified in the patent claims are specified and explained in more detail in the description, with further preferred embodiments of the invention being presented.

A hot water storage tank contributes to this, at least having a container with a volume enclosed by a container wall for storing hot water and a supply line for cold water. The supply line extends from outside the container over the container wall into the volume up to an outlet of the supply line. The supply line has a smaller first flow cross-sectional area Q1 upstream of the outlet (e.g. in the area of the container wall or downstream thereof) and a larger second flow cross-sectional area Q2 between the first flow cross-sectional area Q1 and the outlet.

The hot water tank is in particular a hot water tank for supplying hot water, for example to a building. The hot water tank can be designed as a buffer tank and/or a layered tank. It can comprise a heat exchanger for transferring a heat flow, for example for heat exchange with a heating circuit of a heating system. The heat exchanger can be designed, for example, as a pipe coil, which (when assembled or set up) is usually can be arranged in a (geodetically) lower area of the hot water tank.

The hot water tank can be designed to hold heated drinking water or domestic water or water to be heated, or to hold a heat transfer medium for the heating circuit. The volume of the hot water tank or container can be completely filled with water or at least partially filled with air (as an internal expansion volume).

In order to refill the hot water that has been drawn off, hot water tanks usually have a cold water supply (supply line), i.e. a supply of fresh water, often connected to a domestic water system or a water network. The cold water supply or its outlet is usually arranged in the lower area of the hot water tank to support the formation of a temperature stratification in the water volume. The supply line extends from outside the tank over the tank wall into the volume to an outlet of the supply line, with the flow direction of the cold water running through the supply line to the outlet. Accordingly, in the flow direction of the cold water, the first flow cross-sectional area Q1 is arranged upstream of the second flow cross-sectional area and upstream of the outlet.

In the present case, it is proposed that the supply line be designed at least partially in the manner of a diffuser, in which the flow speed of the cold water supplied to the volume is reduced to such an extent by increasing the flow cross-sectional area that mixing of the supplied cold water with the heated hot water within the volume is as low as possible. This makes it possible to provide a higher quality of temperature stratification and thus a larger usable hot water volume.

In particular, the cold water can only flow out of the supply line via one outlet, so a perforation of the supply line is not provided for.

In particular, a ratio Q2/Q1 is at least two, preferably at least three, particularly preferably at least four. In particular, the ratio Q2/Q1 is at most 20, preferably at most 10.

In particular, a third flow cross-sectional area changes continuously in a section of the supply line which is arranged between the first flow cross-sectional area and the second flow cross-sectional area.

In particular, the third flow cross-sectional area increases continuously in the section. In particular, the supply line is designed such that the flow cross-sectional area increases exclusively in the section.

In particular, the section extends exclusively in a straight line, i.e. straight, not bent or curved. In particular, the supply line extends from the outside through the tank wall to the inside and then extends with the section in a straight line downwards to the (geodetically) lower area of the volume. In particular, in the area of the section in which the flow cross-sectional area changes (continuously), the supply line runs exclusively parallel to the direction of gravity (if the hot water tank is installed as intended).

In particular, the supply line widens conically in the section, so the section is designed in the manner of a cone. In particular, the opening angle of each wall of the cone is between 5 and 12 degrees, preferably between 7 and 10 degrees, compared to a parallel arrangement of the walls.

In particular, a laminar/stationary flow of the supplied cold water should be maintained. The laminar/stationary flow is maintained by the section acting as a diffuser and the flow velocity is thus reduced in accordance with the conservation of mass at the outlet or at the second flow cross-sectional area (continuity equation for stationary flows for incompressible fluids). The length of the expanding section can be determined via the opening angle and the desired flow velocity at the outlet or at the second flow cross-sectional area.

In particular, the first flow cross-sectional area is the smallest flow cross-sectional area of the supply line (at least of the part of the supply line that is arranged within the volume). In particular, the second flow cross-sectional area is the largest flow cross-sectional area of the supply line (at least of the part of the supply line that is arranged within the volume). In particular, the outlet has the largest flow cross-sectional area.

In particular, the volume extends from a lower area to an upper region of the container, wherein the outlet is arranged in the lower region and an inlet of a withdrawal line for the hot water arranged in the volume is arranged above the outlet in the upper region.

In particular, a heat exchanger line is arranged at least in the lower region and within the volume, wherein the heat exchanger line extends spirally around the supply line at least in the lower region.

As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, sizes or processes, and in particular do not necessarily specify a dependency and/or sequence of these objects, sizes or processes. If a dependency and/or sequence is required, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described design. If a component can occur multiple times ("at least one"), the description of one of these components can apply equally to all or part of the majority of these components, but this is not mandatory.

A hot water tank with a specially designed supply line for cold water is proposed here. The supply line is designed in the manner of a diffuser (e.g. as a funnel-shaped pipe) in at least one section, so that the flow speed of the cold water in the supply line, i.e. in that section, is reduced to such an extent that mixing with the already heated hot water is minimal. This makes it possible to achieve a high layer quality within the hot water tank, so that more usable volume of hot water is available.

• 1: einen Warmwasserspeicher in einer perspektivischen Ansicht;
• 2: den Warmwasserspeicher nach 1 in einer Seitenansicht im Schnitt;
• 3: den Warmwasserspeicher nach 1 und 2 in einer weiteren Seitenansicht;
• 4: den unteren Bereich des Warmwasserspeichers nach 1 bis 3 in einer Seitenansicht im Schnitt;
• 5: den Warmwasserspeicher nach 1 bis 4 in einem ersten Zustand, in einer Seitenansicht im Schnitt;
• Fig: 6: einen bekannten Warmwasserspeicher in einem ersten Zustand, in einer Seitenansicht im Schnitt;
• 7: den Warmwasserspeicher nach 5 in einem zweiten Zustand, in einer Seitenansicht im Schnitt; und
• 8: den Warmwasserspeicher nach 6 in einem zweiten Zustand, in einer Seitenansicht im Schnitt.

The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments given. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description. In particular, it should be noted that the figures and in particular the size relationships shown are only schematic. They show:

• 1 : a hot water tank in a perspective view;
• 2 : the hot water tank after 1 in a side view in section;
• 3 : the hot water tank after 1 and 2 in another side view;
• 4 : the lower part of the hot water tank 1 to 3 in a side view in section;
• 5 : the hot water tank after 1 to 4 in a first state, in a side view in section;
• Fig: 6: a known hot water tank in a first state, in a side view in section;
• 7 : the hot water tank after 5 in a second state, in a side view in section; and
• 8 : the hot water tank after 6 in a second state, in a side view in section.

1 shows a hot water tank 1 in a perspective view. 2 shows the hot water tank 1 after 1 in a side view in section. 3 shows the hot water tank 1 after 1 and 2 in another side view. 4 shows the lower area 13 of the hot water tank 1 after 1 to 3 in a side view in section. The 1 to 4 are described together below.

The hot water tank 1 has a container 2 with a volume 4 enclosed by a container wall 3 for storing hot water 5 and a supply line 6 for cold water 7. The supply line 6 extends from outside the container 2 over the container wall 3 into the volume 4 up to an outlet 8 of the supply line 6. The supply line 6 has a smaller first flow cross-sectional area Q1 9 upstream of the outlet 8, also in the area of the container wall 3 (and downstream thereof), and a larger second flow cross-sectional area Q2 10 between the first flow cross-sectional area Q1 9 and the outlet 8.

The volume 4 of the container 2 extends from a lower region 13 to an upper region 14 of the container 2, wherein the outlet 8 is arranged in the lower region 13 and an inlet 15 of a withdrawal line 16 arranged in the volume 4 for withdrawing hot water 5 from the container 2 is arranged above the outlet 8 in the upper region 14.

The hot water tank 1 has a heat exchanger in the form of a heat exchanger line 17 for heat exchange with a heating circuit of a heating system (not shown). The heat exchanger is designed as a pipe coil (heat exchanger line 17) which (in the assembled or built-up state) is arranged in a (geodetically) lower region 13 of the hot water tank 1. The heat exchanger line 17 extends spirally around the supply line 6 at least in the lower region 13.

The supply line 6 extends from outside the container 2 over the container wall 3 into the volume 4 up to an outlet 8 of the supply line 6, wherein the flow direction of the cold water 7 runs through the supply line 6 towards the outlet 8. Accordingly, in the flow direction of the cold water 7, the first flow cross-sectional area Q1 9 is arranged upstream of the second flow cross-sectional area Q2 10 and upstream of the outlet 8.

The supply line 6 is at least partially designed in the manner of a diffuser, in which, due to an (increasing) enlargement of the third flow cross-sectional area 11, the flow velocity of the cold water 7 supplied to the volume 4 is reduced to such an extent that mixing of the supplied cold water 7 with the heated hot water 5 within the volume 4 is as low as possible (see 4 to 8 This allows a higher quality of temperature stratification and thus a larger usable volume of hot water to be made available.

A third flow cross-sectional area 11 of the supply line changes continuously in a section 12 of the supply line 6, which is arranged between the first flow cross-sectional area 9 and the second flow cross-sectional area 10.

The third flow cross-sectional area 11 in the section 12 increases continuously and is designed conically. The supply line 6 is designed in such a way that in the section 12 the third flow cross-sectional area 11 increases exclusively up to the second flow cross-sectional area 10. The opening angle 18 of each wall of the cone is between 5 and 12 degrees compared to a parallel arrangement of the walls.

The section 12 extends exclusively in a straight line, i.e. straight, not bent or curved. The supply line 6 extends from the outside through the tank wall 3 to the inside of the tank 2 and then extends with the section 12 in a straight line downwards to the (geodetically) lower area 13 of the volume 4. The supply line 6 runs exclusively parallel to the direction of gravity in the area of the section 12, in which the flow cross-sectional area 11 changes continuously (if the hot water tank 1 is installed as intended).

The first flow cross-sectional area 9 is thus the smallest flow cross-sectional area 11 of the supply line 6. The second flow cross-sectional area 10 is the largest flow cross-sectional area 11 of the supply line 6. The outlet 8 has the largest flow cross-sectional area 10, 11.

5 shows the hot water tank 1 after 1 to 4 in a first state, in a side view in section. 6 shows a known hot water tank 1 in a first state, in a side view in section. 7 shows the hot water tank 1 after 5 in a second state, in a side view in section. 8 shows the hot water tank 1 after 6 in a second state, in a side view in section. The 5 to 8 are described together below. Please refer to the explanations on the 1 to 4 is referred to.

5 and 7 show the hot water tank 1 with the expanding supply line 6. 6 and 8 show a known hot water tank with a known supply line 6. In the first state ( 5 and 6 ) shows the mixing of the water 5, 7 in the container 2 when the level of the cold water 7 is low. In the second state ( 7 and 8 ) the mixing of the water 5, 7 in the tank 2 is shown when the level of the cold water 7 is high.

The supply line 6 of the hot water tank 1 to 5 and 7 is designed in a section 12 in the manner of a diffuser (e.g. as a funnel-shaped pipe), so that the flow speed of the cold water 7 in the supply line 6, i.e. in the section 12, is reduced to such an extent that the mixing with the already heated hot water 5 is minimal. This makes it possible to achieve a high layer quality within the hot water tank 1, so that more usable volume of hot water 5 is available.

list of reference symbols

1

hot water tank

2

container

3

container wall

4

volume

5

hot water

6

supply line

7

cold water

8

outlet

9

first flow cross-sectional area Q1

10

second flow cross-sectional area Q2

11

third flow cross-sectional area

12

Section

13

lower area

14

upper area

15

inlet

16

extraction line

17

heat exchanger line

18

opening angle

Claims (9)

Hot water storage tank (1), at least comprising a container (2) with a volume (4) enclosed by a container wall (3) for storing hot water (5) and a supply line (6) for cold water (7), wherein the supply line (6) extends from outside the container (2) over the container wall (3) into the volume (4) as far as an outlet (8) of the supply line (6), characterized in that the supply line (6) has a smaller first flow cross-sectional area Q1 (9) upstream of the outlet (8) and a larger second flow cross-sectional area Q2 (10) between the first flow cross-sectional area Q1 (9) and the outlet (8). Hot water tank (1) after claim 1 , characterized in that a ratio Q2/Q1 is at least two. Hot water tank (1) according to one of the preceding claims, characterized in that a third flow cross-sectional area (11) changes continuously in a section (12) of the supply line (6) which is arranged between the first flow cross-sectional area (9) and the second flow cross-sectional area (10). Hot water tank (1) after claim 3 , characterized in that the third flow cross-sectional area (11) in the section (12) continuously and exclusively increases. Hot water tank (1) according to one of the preceding Claims 3 and 4 , characterized in that the section (12) extends exclusively in a straight line. Hot water tank (1) according to one of the preceding Claims 4 and 5 , characterized in that the supply line (6) widens conically in the section (12). Hot water tank (1) according to one of the preceding claims, characterized in that the outlet (8) has the largest flow cross-sectional area (11). Hot water tank (1) according to one of the preceding claims, characterized in that the volume (4) extends from a lower region (13) to an upper region (14) of the container (2), wherein the outlet (8) is arranged in the lower region (13) and an inlet (15) of a withdrawal line (16) for the hot water (5) arranged in the volume (4) is arranged above the outlet (8) in the upper region (14). Hot water tank (1) after claim 6 , characterized in that at least in the lower region (13) and within the volume (4) a heat exchanger line (17) is arranged, which extends spirally around the supply line (6) at least in the lower region (13).

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