DE202016005844U1 - Heat storage with hot water heat exchanger - Google Patents

Abstract

Heat storage with storage container (1) and a heat exchanger for heating process water, wherein the heat exchanger includes at least two parts, of which the first part heat exchanger (2) is arranged in the upper region of the storage container and this region (3) is separated from the rest of the storage container and a second partial heat exchanger (4) is connected in series, wherein the second partial heat exchanger (4) is formed so that the entering into it storage water is removed from the separated storage area (3) and the cooled by the domestic water heating storage water by a Pipe (5) in the lower storage area (6) is transported, wherein the hot water to be heated first flows through the second part of the heat exchanger (4) and then the first part of heat exchanger (2), wherein the separated storage area (3) via at least one Channel (7) communicates with the directly underlying area, characterized in that the mindes least one channel (7) is guided at least up to the height of the first part heat exchanger (2) and between the first part heat exchanger (2) and the second part heat exchanger (4) has a connection (8) for the hot water Circulation return is, further characterized in that at the separated storage area (3) at least one connection (9) is located on the over longer periods of the day, in which usually the hot water circulation is running, a heating by a heat generator ( 10) takes place, which compensates for the cooling of the storage area (3) by the hot water circulation.

Description

The invention relates to heat storage in which heat energy can be stored and removed to form a thermal stratification in liquid storage medium, in particular for the production of hot water and heating heat. It relates in particular to stores filled with heating water with a designed for a stratified discharge heat exchanger for hot water.

From the DE 197 03 722 A1 is a hot water tank with freely immersed in the upper storage tank hot water heat exchanger coil known. Such heat exchangers have the disadvantage that when the domestic water is heated, the entire underlying storage contents are cooled uniformly. The temperature at which the process water escapes from the heat exchanger decreases continuously during the removal and the possible dispensing quantity is thereby greatly reduced compared to a stratified discharge. The efficiency is low and changing tap flows have a direct effect on temperature fluctuations.

Furthermore, heat storage with freely immersed heat exchangers - z. B. formed from stainless steel corrugated pipe - which extend from below in the memory up to the top known. With these stores, heat is removed from all areas of the store during removal. As a result, the lower storage area is cooled, which is advantageous for the efficiency of different heat generator. But even the upper storage area is gradually cooled, so that after a certain time this area must be reheated to ensure the desired hot water temperature.

Of the DE 42 21 668 Heat exchangers are known which allow a stratified loading and unloading of hot water stratified storage. These heat exchangers are installed in the reservoir and consist of finned tube spirals, which are arranged within flow guide structures so that the cooled or heated storage water flows around the finned tubes due to density differences in the countercurrent flow. The Entladewärmetauscher (usually for heating drinking water) is located in the upper part of the memory, and the cooled storage water is passed through a discharge pipe in the lower part of the memory. The upper storage area is not cooled by the discharge.

In the patent DE 101 21 842 is a thermosiphon heat exchanger after the DE 42 21 668 C2 described downstream of which a dipped in the storage water DC heat exchanger downstream in the upper region of the memory. This causes a more uniform DHW tapping temperature at different Zapfraten and Speicherladezuständen. A disadvantage of this invention is that the uppermost layer of water gradually cools when taking hot water, albeit to a lesser extent than in the above described heat storage tank with stainless steel corrugated pipe from bottom to top.

In the DE 20 2004 003 055.1 a construction for the improvement of thermosiphon heat exchangers is described in particular with downstream DC heat exchangers. The thermosyphon heat exchanger is mounted on an annular disc with a peripheral edge. Above the thermosyphon heat exchanger is a downstream coiled tubing analogous to DE 101 21 842 , Between annular disc and wall of the storage container there is a channel-shaped gap. During discharge operation, storage water is cooled in the thermosyphon heat exchanger and flows down in a discharge pipe. This storage water is sucked in at the inlet openings of the thermosyphon heat exchanger. The storage water, which is cooled above the thermosyphon heat exchanger through the downstream coiled tubing, thus flows directly into the thermosyphon heat exchanger and does not mix with the hot water layers below the thermosyphon heat exchanger.

All of the described inventions for thermosyphon heat exchangers have the disadvantage that the discharge process must continue for a certain time, so that the thermosiphonic flow with good cooling of the storage water gets going. Furthermore, at the beginning of each discharge, first the storage water, which is located in the outflow pipe and has not yet or has not yet cooled down to the maximum, is pushed by the incipient downflow into the lower storage area.

This disadvantage is in the DE 195 48 816 A1 avoided: In addition to the arranged in the upper storage area, taken in a Strömungsleitstruktur heat exchanger an analogously constructed heat exchanger is mounted in the lower storage area. With a small withdrawal flow, the water to be heated is already preheated in the lower part of the heat exchanger by the outflowing storage water and thus enters the upper part, where the remaining heating takes place. This creates a passive control effect for the storage water flow, which can be actively reinforced by appropriate interconnection with a thermostatic mixing valve (hot water mixer).

A disadvantage of this arrangement is the relatively large expense in that not only one, but both heat exchangers are arranged within a flow guide, wherein the lower heat exchanger contributes only very little to the total heat transfer performance at full power requirement.

Another disadvantage of all arrangements described is the operation in connection with hot water circulation circuits. Usually, in the heat accumulators described above, the return of the hot water circulation is connected to the cold water inlet of the storage or heat exchanger or to a separate outlet of the heat exchanger in the middle to upper region. This works in conjunction with an appropriate regulation of the circulation pump, which ensures that the circulation runs only in limited time windows per day and only until the circulated warm water has arrived at the last tapping point or at the latest, until it reaches the memory again , In practice, however, it can often not be ensured that such a control system is installed and operating correctly. Often the hot water circulation runs for longer periods, possibly at intervals, and triggers in conjunction with the above-described thermosiphon and smooth-tube coil heat exchangers - but also external counter-flow heat exchangers - a successive cooling of the upper storage area. This is in conjunction with advanced heat generators such. As solar thermal energy, or fuel cells, which are operated in combination with conventional heat generators such as oil or gas boiler or Elektroheizstäben disadvantageous, since an undesirable reheating is triggered by the conventional heat generator. Rather, what is desired here is that the advanced heat generator - ie z. B. a fuel cell - can store its energy priority - i. d. R. with small but continuous power - and the introduction of conventional energy - i. d. R. with great power, z. B. by a gas boiler - is minimized.

Even with heat pumps as heat generators, the cooling of the upper storage area by hot water circulation is disadvantageous because the heat pump must then often the upper, i. d. R. for the hot water preparation reserved storage area with higher temperatures and thus higher power consumption reheat.

Object of the invention is to make a hot-water stratified storage, in which a continuous heating with low power over long periods of the day, so that the cooling of the upper storage area is minimized by hot water heating and in particular by hot water circulation. Furthermore, the heat storage should be designed so that - even if it contains a thermosiphonically operated Entladewärmetauscher - the lower storage area is cooled even during short discharges.

The task is solved with the features of claims 1-3.

• a) größere Warmwasser-Entnahmemengen
• b) Wärmeentzug durch Warmwasser-Zirkulation
• c) kleine, kurze Warmwasser-Entnahmen

The basic idea is that the heat exchanger is designed so that its function differs depending on the case occurring:

• a) larger hot water withdrawal quantities
• b) heat removal by hot water circulation
• c) small, short hot water withdrawals

In case a), the hot storage water should be cooled in the upper part of the storage, conveyed downwards and layered there, so that the lower, cooler water layers grow and the uppermost storage layers remain hot until completely discharged.

In case b), the storage water cooled only slightly by the hot water circulation should not be transported into the lower storage area and mix there. Instead, the continuous heating of the storage to compensate for the heat extraction.

In case c), as in case a), storage water should be cooled down and conveyed downwards, but only a small amount corresponding to the removal, which is cooled well.

The basic structure and the three modes of operation are described below with reference to 1 . 2a . 2 B and 2c described:

The heat exchanger for hot water preparation is similar to the construction of the DE 20 2004 003 055.1 divided into at least two partial heat exchangers: the first partial heat exchanger 2 is in the upper area of the storage tank 1 arranged and this area 3 is separated from the rest of the storage tank. The second part heat exchanger 4 is connected in series and constructed so that the memory water entering it the separated memory area 3 is removed and the cooled by the domestic water heating storage water through a pipe 5 in the lower memory area 6 is transported. The separated storage area 3 communicates via at least one channel 7 that extends at least to the top of the first part heat exchanger 2 is guided, with the area directly below it. The hot water to be heated first flows through the second partial heat exchanger 4 and then the first part of the heat exchanger, with a connection between the two heat exchangers 8th located. The DHW circulation return is connected here: The DHW circulation pump 13 promotes Hot water from the outlet of the first partial heat exchanger 2 near the tapping point and from there back to the port 8th ,

At the separated storage area 3 There is at least one connection 9 , over which for longer periods of the day, in which usually also the hot water circulation runs, a heating by a heat generator - z. As a fuel cell - takes place. The storage water, which is cooled by the hot water circulation, remains in the separated area 3 because the opening of the channel 7 is too high, and since the storage water density at low cooling is too low to a drop through the second partial heat exchanger 4 to trigger at the bottom. The cooling of the separated storage area 3 through the hot water circulation can thus simultaneously or - if the cooling takes place in intervals with initially stronger cooling - delayed by the heating of the heat generator 10 be compensated: If the temperature of the heating is slightly above the required temperature without circulation, the cooling is compensated by the circulation and so the heated up, shifted down storage layers have at least set temperature.

The heat generator 10 removes colder storage water for heating at a lower point of the storage tank - usually at the very bottom. This shifts the storage layers down. Through the channel 7 , through which the separated upper storage area communicates with the underlying area, hot water enters this area. In the heat generator, it may be z. B. to a fuel cell, a micro CHP a solar thermal or photovoltaic solar system or a base load heat pump. The heat generator or parts thereof may also be inside the heat accumulator 1 be arranged, for. B. a heat exchanger. The heat generator 10 Usually includes a circulation pump for the promotion of the storage water, it is not shown here.

The second part heat exchanger 4 can be used both as an external or internal countercurrent heat exchanger in which the storage water by means of a pump 14 through the heat exchanger and then conveyed down, be constructed (see 1 ), as well as a thermosiphon heat exchanger (see 2a ). If it is constructed as a thermosiphon heat exchanger, is advantageously in the lower storage area 6 a freely submerged third part heat exchanger 11 , which is connected in series with the first and second partial heat exchangers, wherein the hot water to be heated first the lower heat exchanger 11 flows through. Thus, for small withdrawals hot water from the upper part heat exchangers 2 and 4 removed and the lower heat exchanger 11 filled with cold water. This causes the lower memory area 6 is cooled, even if a thermosiphon flow is not yet in motion. In the connecting pipe between the lower DC heat exchanger and the thermosiphon heat exchanger above flows in the process first of all the water, which has assumed the temperature of the lower storage area, ie a higher temperature than that of the cold water. As a result, the thermosiphon flow is only slightly excited at low removal rates, which correspond approximately to the contents of the lower DC heat exchanger, since the water in the tube leading downwards from the thermosyphon heat exchanger 5 Less is cooled than it would be without the lower heat exchanger 11 the case would be, that is, less water flows down. In this way, with small withdrawals, the transport of storage water in the lower area 6 reduced and the lower storage area is additionally cooled at each hot water extraction - regardless of whether large or small.

2 B shows schematically the movement of the storage water during the heating by the heat generator 10 ,

2c schematically shows the movement of the storage water during the final charge by hot water.

• – dass der Wärmeentzug über den ersten Teil-Wärmetauscher 2 und damit die Abkühlung des Speicherwassers oben auf das notwendige Minimum reduziert wird,
• – dass die Abkühlung durch den oberen Teil-Wärmetauscher 2 des Speicherwassers entweder – falls es sich um eine geringe Abkühlung wie bei Warmwasserzirkulation handelt – durch die Beheizung ausgeglichen wird, oder dass das Speicherwasser im zweiten Teil-Wärmetauscher 4 möglichst stark weiter abgekühlt und unten im Speicher eingeschichtet wird.
• – dass die niedrigen Temperaturen von Kaltwasser, das in einem Brauchwassermischer zugemischt wird, maximal zur Abkühlung des unteren Speicherbereichs genutzt werden.

By the interconnections described below the heat exchanger unit with an external hot water mixer, the task of the invention can be particularly well met. It should be achieved with this:

• - that the heat extraction via the first part heat exchanger 2 and so that the cooling of the storage water is reduced to the necessary minimum,
• - that the cooling through the upper part heat exchanger 2 the storage water either - if it is a small cooling as in hot water circulation - is compensated by the heating, or that the storage water in the second partial heat exchanger 4 cooled down as much as possible and layered down in the memory.
• - That the low temperatures of cold water, which is mixed in a domestic water mixer, maximum be used to cool the lower storage area.

A domestic water mixer is a thermostatic mixing valve and serves to equalize the hot water outlet temperature and is usually provided at heat storage for hot water heating. In particular, at the beginning of a tap water with high temperature, namely that of the storage water above, to which the content of the has equalized the upper heat exchanger in the downtime.

Advantageously, the cold water connection of the hot water mixer is not to the cold water, but to a connection between the lower part heat exchanger 11 and the first part heat exchanger 2 connected.

In the 1 and 2 is the connection between the second partial heat exchanger 4 and the upper part heat exchanger 2 , In 2 this flows in the water heater 12 initially mixed cold water through the lower part heat exchanger 11 and cools the storage area 6 off there. It then flows through the second partial heat exchanger 4 - Here is a thermosiphon heat exchanger. This leads to a faster start of the thermosiphon flow than if only the non-mixed cold water flow would flow through this heat exchanger. However, it may then initially come to high hot water temperatures in this interconnection, since the water in the thermosiphon heat exchanger is usually already too hot above. With small hot water content of this heat exchanger, however, this effect is small and generally acceptable.

This interconnection with a thermosiphon heat exchanger is useful if the memory is not heated to very high temperatures, because the reduction of the temperature with this interconnection is limited, because the already mixed in the second part of the heat exchanger 4 be heated to impermissibly high temperatures.

Is it like in 1 around an external heat exchanger with circulating pump 11 with appropriate precautions to avoid the high temperatures of the storage water in the heat exchanger at a standstill (eg., Position in the lower part of the heat accumulator), then there is the problem of temporarily too high temperatures. The speed of the circulation pump 14 is controlled so that the set temperature is reached.

This mixes the hot water mixer 12 with the target temperature set at the same time, the water from the second partial heat exchanger is usually the same 4 via the cold water connection to and the first partial heat exchanger 2 will only be at peak power when the bleed line is too big for the heat exchanger performance of the second part heat exchanger 4 is, flows through. A safe limitation of the hot water temperature is possible even at high storage temperatures.

In hot water circulation is by the cold water connection of the hot water mixer 12 the return of the circulation mixed in, so that the permissible flow temperature is maintained safely. At the same time, only a small amount of water needs to pass through the first part heat exchanger 2 flow in the memory and thus leads there to a reduced cooling.

The advantage of the interconnection is that the first partial heat exchanger is only flowed through as much as necessary in order to reach the setpoint temperature, in particular at high tap rates. Thus, the storage water becomes in the separated area 3 With small withdrawals and weak Zapfraten not or only slightly cooled, which is compensated by the continuous reheating of this area. In addition, the second part of the heat exchanger, which is more expensive as countercurrent heat exchanger but also more efficient than the first part of the heat exchanger, can be designed for the average PTO and thus be cheaper than if it had to cover the peak load.

In 3 with thermosiphon heat exchanger is the cold water connection for the hot water mixer 12 between lower part heat exchanger 11 and the second part heat exchanger 4 , Thus, the cold water added in the service water mixer first flows through the lower third part heat exchanger 11 and thus cools the lower storage area 6 from. As a result, the desired effect of cooling the lower storage area is intensified, especially with small hot water withdrawals.

In hot water circulation is by admixing the cold water connection of the hot water mixer, the second part heat exchanger 4 flows through the return of the circulation in the opposite direction to the normal service water flow. The warm circulation return does not cause thermosiphon flow and there is little or no heating of the lower storage area. However, if the heat accumulator is largely charged (eg three quarters of the volume from above), then the circulation flow temperature may not be reduced sufficiently.

4a and b show a further Verschaltungsmöglichkeit for a heat storage with thermosiphon heat exchanger where the disadvantage of the interconnection according to 2 - that the hot water temperature can be reduced only limited - does not exist. At the connection 8th between the first and second partial heat exchanger is a second thermostatic hot water mixer 16 whose cold water connection is connected to the cold water, the hot water connection to the outlet of the second partial heat exchanger 4 and the mixing outlet to the cold water connection of the first thermostatic water mixer 12 , Both water heaters are on the same Value set. As long as the setpoint temperature is reached in the second partial heat exchanger, the first dhw mixer shuts off 12 the passage through the first part heat exchanger 2 from.

With hot water circulation, the hot water flows out of the first partial heat exchanger. In the first service water mixer 12 a part of the circulation return is admixed to obtain set temperature. The temperature of the circulation return is below the set temperature of the second hot water mixer 16 , Thus, this opens its hot water connection, and the circulation return flows through the hot water connection in the first part of the heat exchanger. Instead of connecting the circulation return between the two dhw mixers, it can also be done before the hot water connection of the second dhw mixer 16 be connected. Also in this case, the mixer provides 16 a passage between the hot and mixing port ago, so that the circulation return both in the first part of the heat exchanger 2 can occur as well as through the first dhw mixer 12 can be mixed.

4b the thus optimized wiring branches, that the cold water connection of the dhw mixer 16 between the third partial heat exchanger 11 and the second part heat exchanger 4 connected. As a result, the mixed cold water always first cools the lower storage area 6 ,

Different designs are especially for the first partial heat exchanger 2 possible: z. B. smooth-tube spiral, corrugated tube spiral, immersed in the reservoir container bubble.

Instead of the described embodiments, other embodiments are possible according to the invention: z. B., the separated memory area 3 , which is deprived of heat for hot water circulation, and which is heated for longer periods of the day, not be located at the top but in the central region of the memory.

LIST OF REFERENCE NUMBERS

1

storage container

2

First partial heat exchanger (top, immersed)

3

Separated storage area above

4

Second partial heat exchanger (flowed through by storage water)

5

pipe

6

Lower memory area

7

channel

8th

Connection between first and second partial heat exchanger

9

Storage connection above for heating

10

heat generator

11

Third partial heat exchanger (below, immersed)

12

Thermostatic hot water mixer

13

Hot water circulation pump

14

Circulation pump for second partial heat exchanger

15

Temperature sensor for speed control circulation pump

16

Second Thermostatic water heater

KW

cold water

WW

hot water

K

Cold water connection of the dhw mixer

H

Hot water connection of the hot water mixer

M

Mixed water connection of the dhw mixer

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19703722 A1 [0002]
• DE 4221668 [0004]
• DE 10121842 [0005, 0006]
• DE 4221668 C2 [0005]
• DE 202004003055 [0006, 0019]
• DE 19548816 A1 [0008]

Claims (8)

Heat storage with storage tank ( 1 ) and a heat exchanger for heating process water, wherein the heat exchanger includes at least two parts, of which the first part heat exchanger ( 2 ) is arranged in the upper region of the storage container and this region ( 3 ) is separated from the remaining storage tank and a second partial heat exchanger ( 4 ) is connected in series, wherein the second partial heat exchanger ( 4 ) is formed so that the storage water entering it the separated storage area ( 3 ) and cooled by the hot water heating storage water through a pipe ( 5 ) into the lower memory area ( 6 ), wherein the hot water to be heated first the second partial heat exchanger ( 4 ) and then the first part heat exchanger ( 2 ), wherein the separated memory area ( 3 ) over at least one channel ( 7 ) communicates with the directly underlying region, characterized in that the at least one channel ( 7 ) at least up to the height of the first part heat exchanger ( 2 ) and between the first part heat exchanger ( 2 ) and the second part heat exchanger ( 4 ) a connection ( 8th ) for the hot water circulation return, further characterized in that at the separated storage area ( 3 ) at least one connection ( 9 ), over which for a long time on the day, in which usually also the warm water circulation runs, a heating by a heat generator ( 10 ) takes place, the cooling of the storage area ( 3 ) compensated by the hot water circulation. Heat accumulator according to claim 1, characterized in that the second partial heat exchanger ( 4 ) is designed as a thermosiphon heat exchanger, in which the cooled by the domestic water heating storage water by a thermosiphonic effect through the pipe ( 5 ) into the lower memory area ( 6 ) flows. Heat storage according to claim 2, characterized in that in the lower storage area ( 6 ) a freely submerged third part heat exchanger ( 11 ), which is connected in series with the first and second partial heat exchangers, wherein the hot water to be heated first the lower heat exchanger ( 11 ) flows through. Heat accumulator according to claim 1, 2 or 3, characterized in that at the outlet of the first part heat exchanger ( 2 ) a thermostatic hot water mixer ( 12 ), whose cold water connection at the connection ( 8th ) is connected between the first and second partial heat exchanger. Heat accumulator according to one of the claims 4, characterized in that at the connection ( 8th ) between the first and second partial heat exchangers, a second thermostatic hot water mixer ( 16 ), whose cold water connection is connected to the cold water, the hot water connection to the outlet of the second partial heat exchanger ( 4 ) and the mixing outlet to the cold water connection of the first thermostatic hot water mixer ( 12 ). Heat accumulator according to one of the claims 4, characterized in that at the connection ( 8th ) between the first and second partial heat exchangers, a second thermostatic hot water mixer ( 16 ), whose cold water connection between the third partial heat exchanger ( 11 ) and the second part heat exchanger ( 4 ), the hot water connection to the outlet of the second partial heat exchanger ( 4 ) and the mixing outlet to the cold water connection of the first thermostatic hot water mixer ( 12 ). Heat accumulator according to claim 1, 2 or 3, characterized in that at the outlet of the first part heat exchanger ( 2 ) a thermostatic hot water mixer ( 12 ) whose cold water connection between the third partial heat exchanger ( 11 ) and the second part heat exchanger ( 4 ) connected. Heat accumulator according to claim 1 or 4, characterized in that it is in the second partial heat exchanger ( 4 ) to an external countercurrent heat exchanger with variable-speed circulating pump ( 14 ) and the speed of the circulation pump ( 14 ) is set to approximately the same desired temperature as the hot water mixer ( 12 ).

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