EP1170554B1 - System and method for preparing hot sanitary water - Google Patents

Abstract

The primary circuit (10) comprises an appliance (11) providing warm or hot water, and a fluid-conveyor (14) which has a regulator. A heat exchanger (5) transmits heat from the primary circuit's fluid to the service water in the secondary circuit (20). The primary or secondary circuits contain a temperature sensor (17,27). A branch-point (18) for a branch pipe (19) behind the conveyor in the direction of flow is positioned in the primary circuit in the discharge side pipe (13). The branch pipe leads to a mixer valve (15) on the inlet side pipe (12).

Description

The invention relates to an arrangement for providing hot service water with a primary circuit with a fluid, a hot or hot fluid providing device and a conveyor for the fluid, a secondary circuit for the hot water to be heated, a heat exchanger for transferring the fluid of the primary circuit to the service water in the secondary circuit, a control device for the conveyor, a temperature sensor in the primary or secondary circuit and a circuit in the control device that turns on and / or off upon reaching certain thresholds of temperature and / or temperature gradients on the temperature sensor and / or time-dependent the conveyor. The invention also relates to a method for providing hot service water in which a fluid runs in a primary circuit, a device provides hot or hot fluid and a conveyor promotes the fluid that runs hot water to be heated in a secondary circuit in a heat exchanger from the heat Fluid of the primary circuit is transferred to the service water in the secondary circuit, the conveyor is controlled, a temperature sensor is provided in the primary and / or secondary circuit and when controlling the conveyor this upon reaching certain thresholds of temperature and / or temperature gradients at the temperature sensor and / or Depending on the time this conveyor is turned on and / or off.

The provision of domestic hot water is conventionally by means of a heat source in a water heater, a so-called boiler, which at the same time assumes the task of energy buffering.

However, especially in solar plants hot water preparations are increasingly carried out in the continuous flow principle. In this case, a heat exchanger, for example, a plate heat exchanger, on the one hand warm water from a store and cooled water then back into returned the memory. On the other hand, cold service water or drinking water is fed into the heat exchanger and from there warm drinking water is conveyed to a tapping point to the user.

Such hot water preparation is known in the flow principle, for example from DE 40 35 115 C2. The design proposed there requires a fairly high amount of sensor technology and uses very sensitive components, such as flow switches, to bring about appropriate appropriate control.

Cheaper already generic hot water preparations in the flow principle according to DE 196 19 566 C1, in which these components are no longer required.

In DE 196 42 179 A1 it is proposed to keep the temperature of the primary side flowing heating water after exiting the heat exchanger as possible to a constant value and return too high temperatures of this return water part through a short circuit back into the cycle. This should be set as the actual goal of a constant domestic hot water temperature.

In all three known concepts, the heat exchangers are connected directly to the reservoir, ie a device which provides hot or hot fluid. The heat exchanger is therefore supplied on the primary side water at a very high temperature level, because these high temperature levels, for example, 90 ° C are not only achieved in the solar storage, but there are also quite desirable. However, a direct forwarding of the very hot fluid also leads to high temperatures at the heat exchanger transfer surfaces, which under certain circumstances can lead to undesirable lime failure there.

In post-published EP 1 148 302 A2 a domestic hot water system is proposed, which comprises a heating circuit with a buffer memory and a controllable in their speed circulation pump and a service water circuit with a service water inlet and a process water drain. A heat exchanger is on the primary side in the heating circuit and secondary side involved in the hot water circuit and heated, if necessary, domestic hot water in a water heater principle. To control the discharge temperature of the process water, there is a PID controller which controls the pump drive as a function of the comparison of the secondary outlet temperature of the heat exchanger as the actual value with a predetermined desired value. A temperature sensor in the outlet area of the process water drain from the heat exchanger reads the corresponding temperature values into the controller. The pump drive is controlled by the controller over the entire speed range from speed 0 to rated speed without detection of a flow through the hot water circuit. To improve the control behavior and to avoid calcifications in the heat exchanger, a thermal mixer is installed in the heating circuit with a bypass line that covers the buffer gap.

There remains a need for arrangements and methods that reduce the risk of scale in the heat exchanger.

Object of the present invention is therefore to propose such an arrangement and such a method.

This object is achieved by an arrangement according to claim 1 on the one hand and by a method according to claim 8 on the other.

Thus, according to the invention, a type of bypass is provided in the primary circuit. Originally from the device with the hot or hot fluid, so in particular the memory, derived fluid has after passing through the heat exchanger, a significant portion of its stored heat in discharged the secondary krelslauf and is characterized significantly cooled. In the prior art, this cooled fluid is now returned to the memory. According to the invention by the bypass line is a controllable However, proportion of this fluid again within the primary circuit in the area in front of the heat exchanger, but fed to the memory. At this point it is mixed with the actually hot, for example, 90 ° C amount of fluid directly from the memory, so that a mixing temperature between just this very hot starting temperature on the one hand and after passing through the heat exchanger significantly cooler, albeit still warm fluid amount on the other hand reached ,

The fluid, which now enters the side of the primary circuit in the heat exchanger, so that no longer leading to undesirable lime deposits very high temperature, but a precisely adjustable desired temperature, which still has the desired height to the secondary circuit accordingly with heat too supply.

The supply and mixing of the two fluid quantities before the heat exchanger is preferably carried out by a thermostatic valve. This allows a particularly precise determination of the proportions of the two fluid quantities in the mixture.

An arrangement is particularly favorable if the heat exchanger is arranged outside the insulation of the device providing the warm or hot fluid. As a result, the temperature within the heat exchanger is additionally decoupled from the temperature in the device providing the hot or hot fluid. This device is preferably a buffer memory.

The bypass according to the invention with the thermostatic valve preferably provided can ensure that the heat exchanger inlet in the primary circuit, a critical for calcification and not required for the heat transfer undesirable high temperature of above 65 ° C is avoided.

Preferably, it is further provided that the provided in the primary circuit conveyor, so in particular a pump is regulated. As a result, it is possible to optimize the volume flow in the primary circuit which is necessary for the respective desired hot water tap rate in the secondary circuit and the temperature desired there. The return flow in the primary circuit into the storage tank can be placed close to the chilled water temperature, the electric power consumption of the pump moves at a low level.

The switching on and the regulation of the pumping power for hot water preparation can be done via temperature sensors as proposed in DE 196 19 566 C1. This circuit can also be done in a different form. A corresponding temperature sensor can either pick up directly in the primary circuit the existing there, especially at the output of the Wärtnetauschers temperature of the fluid and work with this or with the temperature gradient. But it is also possible to make such a control by skillful use of the data of a temperature sensor in the secondary circuit, in particular at the output of the heat exchanger in the secondary circuit.

It is a further particular advantage if a circulation line is provided with a circulation pump which branches off from the outlet line of the secondary circuit adjacent to the tapping point and leads back to the inlet side line of the secondary circuit with respect to the heat exchanger.

With such a concept, the economy required by the consumer of water consumption can be achieved. A clear tap of the cooled hot water pipes in the secondary circuit is avoided if, for the first time after a certain period of non-use at the tapping point hot service water is desired, which is not there spontaneously available. The standing in the line water is then simply returned through the circulation line back to the heat exchanger. The simple one Untwisting and "letting" the initially cold water can be avoided.

Such a circulation line is currently gaining in particular advantage if it is switched on and / or off and regulated via a temperature sensor. In a preferred embodiment of the invention, this control is possible by one and the same temperature sensor, which also controls the conveyor in the primary circuit, preferably by a temperature sensor adjacent to the output of the heat exchanger in the secondary circuit.

Sanitary hot water circulation pipes in buildings themselves are known for example from DE 94 16 613 U1. Also there is a. Circulation line arranged parallel to a hot water line, wherein an evaluation device is provided which evaluates an induction voltage in the pump when starting a pump by water removal at the tap. Upon reaching a threshold value of the induction voltage, the pump is disconnected from the evaluation device, connected to the general voltage network and switched off again after a certain time. However, such a design is not intended for use with heat exchangers.

The invention provides an arrangement and a regulation of a hot water preparation in a continuous flow principle, which may also include a circulation control. With simple means it is ensured that when needed fast water of the desired temperature is available at the taps, although temperature losses and water consumption are minimized and created by an intelligent arrangement of simple and reliable and cost-effective sensors, a particularly reliable, but nevertheless cost-effective solution ,

Figur 1

eine schematische Darstellung der Erfindung.

In the following an embodiment of the invention will be explained in more detail with reference to the drawing. It shows:

FIG. 1

a schematic representation of the invention.

The purely schematic, only the essential parts of the entire arrangement reproducing representation shows in the left half of a primary circuit 10, in the right half of a secondary circuit 20th

The primary circuit 10 starts on the left with a device that provides hot or hot fluid, here a buffer 11. From this buffer memory 11 leads a line 12 to a heat exchanger 5. After passing through the heat exchanger 5 and the release of heat energy in the same runs the Fluid in the primary circuit 10 back via an output-side line 13 to the device 11, ie the buffer memory.

In the output-side line 13, a conveyor 14, in particular a pump is provided. This conveyor 14 is arranged relatively close to the outlet of the heat exchanger 5. Between the conveyor 14 and the heat exchanger 5, a temperature sensor 17 is additionally arranged here, which thus measures the temperature and / or the temperature gradient of the fluid in the primary circuit 10 virtually immediately after leaving the heat exchanger 5.

Behind the conveyor 14, a branch point 18 for a branch line 19 is provided in the primary circuit 10. This branch line 19 leads back within the primary circuit 10 in the region of the line 12 from the buffer memory 11 to the heat exchanger 5. It opens there in a mixing valve 15th

This mixing valve 15 is in particular a thermostatic valve. He is supplied on the one hand through the branch line 19 cooled fluid from the heat exchanger 5, on the other hand, but also through the line 12 hot fluid from the buffer memory 11. These two apart from the temperature identical fluids are mixed so that a desired predetermined temperature of below 65 ° C at the outlet of the mixing valve 15 is formed. As a result of the further course of the line 12, this fluid possessing the desired temperature is then supplied to the heat exchanger in turn.

Apart from the fluid guide in the branch line 19 runs in the primary circuit 10, the fluid from the upper portion of the buffer memory 11 to the heat exchanger 5, from there through the line 13 then back to the lower portion of the buffer memory 11, where it is layered or otherwise returned suitable.

The secondary circuit 20 on the right side of the illustration of Figure 1 begins with a cold water supply line 22, with the cold process water (drinking water, washing water, etc.) is fed to the heat exchanger 5. In the heat exchanger 5, the heat energy of the current in countercurrent primary circuit 10 is received. After passing through the heat exchanger 5, the service water leaves this again and flows through an output-side line 23 to the hot water tap, the tapping point. The promotion in the secondary circuit can in principle be effected by the fact that the cold water supply is under pressure and the hot water extraction point by a cock locks this pressure if necessary.

In the line 23, the hot water or actual service water is a temperature sensor 27. This temperature sensor 27 is arranged as close to the outlet of the heat exchanger 5.

In addition, in the secondary circuit 20 is still a. Circulation line 40 is provided. The circulation line 40 branches off adjacent to the tapping point 28 and leads back to the cold water inlet line 22 immediately before the heat exchanger 5. In the circulation line 40, a further circulation pump 44 is provided. Also indicated is a temperature sensor 47, which measures the temperature in the circulation line 40, in particular between the circulation pump 44 and the inflow into the cold water inlet 22.

If now the tap is turned on at the tapping point 28, that is to say the hot water tapping point, then either this process or preferably the output signal of one of the temperature sensors 17, 27, 47 inputs. Signal for the circulation pump 44 to deduct the service water located in the line 23 from the area in front of the tap 28 and to promote by the circulation line 40 again in front of the heat exchanger 5.

The purpose of this measure is not to let the cooled water after a certain life in the line 23 to flow out of the tap 28, since the consumption there wants warm water and not cooled hot water. He would probably just run this cooled service water off the line. By contrast, the water currently flowing out of the heat exchanger 5 is warm because it has received heat energy from the primary circuit 10. The length of the line 23 and the flow behavior are known, so that very precisely the circulation pump 44 can be controlled so that exactly when it reaches the desired heated hot water at the tap 28 this can also flow there.

A preferred embodiment for the regulation of the various conveyors and pumps 14, 44, to which may come if required or if desired, operates as follows:

The temperature sensor 17 determines, inter alia, the standby temperature at the conveyor 14. If this falls below a certain threshold, the conveyor 14 is switched to full power for an adjustable period X. The period will be several seconds. It is chosen so long that the cooled fluid in the primary circuit 10 from the heat exchanger 5 by hot fluid from the upper portion of the device 11, ie from the upper storage area, replaced and returned to the lower storage area.

Subsequently, it takes a time Y (also several seconds) until the temperature at the temperature sensor 27 in the secondary circuit 20 at the hot water outlet of the heat exchanger 5 has also risen due to heat conduction. After this period of time Y, the entire heat exchanger 5, including its water content (fluid in the primary circuit 10 and service water in the secondary circuit 20), has then warmed.

Only after this adjustable period Y, the conveyor 14 can be turned on again to further heat the heat exchanger 5. In practice, a regular, one-time short switching on the conveyor 14, for example, 5 seconds duration sufficient to compensate for the Auskühlverluste the heat exchanger 5. With prolonged running of the conveyor 14 unnecessarily hot water would be conveyed from the upper region of the device 11 in the lower storage area. The inventively preferred regular short switch-on leads to a kind of pulse function.

However, if the heat exchanger is completely cooled, for example, because the hot water was turned off, the pulse function also leads to a desired behavior of the system: the repeated switching on the pump after an interruption of a period Y leads to a warming of the hot water in the heat exchanger 5, without that unnecessary mixing of warm fluid in the primary circuit 10 from the upper region of the device 11 in the lower return takes place.

The above behavior is already working, without in the secondary circuit 20 at all a flow takes place, so without any action of the user and in particular without a consumption of hot water.

If service water is tapped, water flows from the heat exchanger 5 into the hot water pipe 23. This process, in turn, registers the temperature sensor 27 as a temperature change. The hot water directly in the heat exchanger 5 is at least slightly warmer than the previously on the temperature sensor 27 pending service water. If this temperature change exceeds an adjustable value AD of, for example, 0.2 ° C. within a certain very short period of time, then the hot water pump is regulated from 0 to maximum line or alternatively switched on and regulated to maximum power. Via a temperature comparison of a desired value at the temperature sensor 27 and an actual value at the temperature sensor 27, the pump power is then then regulated between 0 and maximum power so that the actual value at the temperature sensor 27 is equal to the desired value.

The temperature of the hot or hot fluid in the primary circuit 10 provided by the device 11 can vary widely, depending on the season or other external conditions. Such a fluctuation can be between 50 ° C and 95 ° C. The tap rates for the process water can vary greatly, for example, between 0 and 15 liters per minute. These strong fluctuations lead to very high demands on the control accuracy of the hot water pump.

Of particular advantage is in particular when the PID portions of this scheme are not fixed, but in turn depending on the temperature at a temperature sensor 37 in the upper region of the device 11, ie in the upper memory area, are selected.

Temperature changes at the temperature sensor 27 due to heat loss or heat conduction are significantly lower than temperature changes due to flow movements in the primary circuit 10 or in the secondary circuit 20. Accordingly, the temperature difference is preferably chosen so large that the value is exceeded only in flowing media.

As has been confirmed in measurements carried out when opening a tap, so the removal of hot water in the secondary circuit 20, first a temperature increase at the temperature sensor 27, then a temperature drop. Basically, both changes can turn on the Hot water pump can be used. But it can also deliberately only one of the two changes, for example, the subsequent drop in temperature, are used as Einschaltkriterium the hot water pump.

The switching off of this pump can be done, for example, if in a switchable period XX no or only defined small temperature changes between two thresholds or defined positive temperature changes are registered at the temperature sensor 27.

Switching off can also take place when a temperature above a predetermined desired value is measured via a sensor 17 at the outlet of the heat exchanger 5 in the primary circuit 10 in the line 13 to the device 11. Namely, such a relatively high temperature means that the warm fluid in the primary circuit 10 is no longer cooled in the heat exchanger 5, since no hot water tap more.

At the same time, the temperature sensor 27 can also be used for switching on the circulation pump 44. If the faucet is opened only briefly at the tapping point 28, then the temperature sensor 27 registers the first, as already described above, by a temperature change, first by a temperature increase, then by a temperature drop. These temperature changes adjust the circulation pump 44 for Z seconds. The period is preferably selected so that the hot water is conveyed straight to the taps 28 in the secondary circuit 20. The user of the system has so after a short opening of the tap at the tap 28 and a short break after hot water immediately at the tap 28, without having to tap the line before empty.

After this measure, the circulation pump 44 is blocked for an adjustable period YY, for example for 10 minutes. This period is chosen so that the secondary circuit 20, the cooling of the service water in the lines 22 and 23 as long as the temperature of the service water is still perceived as pleasant. Basically, of course, the circulation could be blocked for a certain period by means of a clock. A temperature sensor 47 in the circulation circuit 40 may additionally detect the temperature in the circulation return to the tap point 28 and the circulation pump 44 above a certain temperature at the temperature sensor 47 basically block.

For example, this would also be a switch-off criterion or would reduce unnecessary start-up of the circulation pump 44 if the process water in the secondary circuit 20 is still warm contrary to the preset time periods. In principle, however, with a single temperature sensor 27, the entire control is feasible.

The invention provides an arrangement and a regulation of a hot water preparation in a continuous flow principle, which may also include a circulation control. With simple means it is ensured that when needed fast water of the desired temperature is available at the taps, temperature losses and water consumption are minimized and by an intelligent arrangement of simple and reliable and cost-effective sensors a particularly reliable, yet inexpensive solution is created ,

LIST OF REFERENCE NUMBERS

5

heat exchangers

10

primary circuit

11

Device for providing a warm or hot fluid

12

management

13

management

14

Conveyor

15

mixing valve

17

temperature sensor

18

branching point

19

branch line

20

secondary circuit

22

Cold water supply line

23

management

27

temperature sensor

28

tap

40

circulation

44

circulation pump

47

temperature sensor

Claims (12)

1. Arrangement for preparing warm service water, with

   - a primary circuit (10) with a fluid, a device (11) preparing warm or hot fluid and a delivery device (14) for the fluid,

   - a secondary circuit (20) for the service water which is to be heated,

   - a heat exchanger (5) for transferring heat from the fluid of the primary circuit (10) to the service water in the secondary circuit (20),

   - a regulating device for the delivery device (14),

   - a temperature sensor (17, 27) in the primary circuit (10) or secondary circuit (20) and

   - an electric circuit in the regulating device which turns the delivery device (14) on and/or off in time-dependent fashion when the temperature and/or the temperature gradient at the temperature sensor (17, 27) reach(es) certain threshold values,

   
   in which the delivery device (14) is provided in the primary circuit (10) in the line (13) on the outlet side relative to the heat exchanger (5), and a branch-off point (18) for a branch line (19) is provided downstream of the delivery device in the flow direction,
   in which the branch line (19) leads from the branch-off point (18) to a mixing valve (15) which is disposed in the line (12) on the inlet side relative to the heat exchanger (5),
   in which the mixing valve (15) is constructed such that, when the delivery device (14) is operating, it mixes the warm or hot fluid which is fed from the device (11) preparing the warm or hot fluid with the fluid which is fed from the branch line (19) and previously cooled in the heat exchanger (5) to obtain a certain temperature in the line (12) at the inlet of the heat exchanger (5),
   in which a circulation line (40) with a circulation pump (44) is provided, which line branches off the line (23) of the secondary circuit (20) on the outlet side relative to the heat exchanger (5) adjacent to the tapping point (28) and leads back to the line (22) of the secondary circuit (20) on the inlet side relative to the heat exchanger (5),
   in which a temperature sensor (17, 27, 47) turns the circulation pump (44) on and/or off and optionally also regulates it, and
   in which the same temperature sensor (27) turns the delivery device (14) in the primary circuit (10) and the circulation pump (44) on and/or off and optionally regulates these.
2. System according to Claim 1,
   characterised in
   that the mixing valve (15) is a thermostatic valve.
3. System according to Claim 1 or Claim 2,
   characterised in
   that the heat exchanger (5) is disposed outside of the insulation of the device (11) preparing the warm or hot fluid.
4. System according to any one of the preceding Claims,
   characterised in
   that the device (11) preparing the warm or hot fluid is a buffer store.
5. System according to any one of the preceding Claims,
   characterised in
   that the temperature sensor (17) in the primary circuit (10) is disposed closely adjacent to the outlet of the heat exchanger (5).
6. System according to any one of the preceding Claims,
   that the temperature sensor (27) in the secondary circuit (20) is disposed closely adjacent to the outlet of the heat exchanger (5).
7. System according to any one of the preceding Claims,
   characterised in
   that the temperature sensors (17, 27) in the primary circuit (10) and in the secondary circuit (20) are disposed outside of the insulation of the device (11) preparing the warm or hot fluid.
8. Method for preparing warm service water, in which

   - a fluid runs in a primary circuit (10),

   - a device (11) prepares warm or hot fluid and a delivery device (14) delivers the fluid,

   - the service water which is to be heated runs in a secondary circuit (20),

   - the heat is transferred from the fluid of the primary circuit (10) to the service water in the secondary circuit (20) in a heat exchanger (5),

   - the delivery device (14) is regulated,

   - a temperature sensor (17, 27) is provided in the primary and/or secondary circuit,

   - when regulating the delivery device (14), this delivery device (14) is turned on and/or off in time-dependent fashion when the temperature and/or the temperature gradient reach(es) certain threshold values at the temperature sensor (17, 27),

   
   in which cooled fluid is returned after passing through the heat exchanger (5) in the primary circuit (10) to a region of the primary circuit (10) between the device (11) preparing the warm or hot fluid and the heat exchanger (5),
   in which this returned fluid is mixed with the warm or hot fluid from the device (11) to obtain a certain temperature at the inlet of the heat exchanger (5), and
   in which the delivery device (14) in the primary circuit is turned on for a predetermined period X when the temperature falls below a threshold value at one of the temperature sensors (17, 27) and afterwards turned off for a minimum duration Y before optionally being turned on again.
9. Method according to Claim 8,
   characterised in
   that the returned cooled fluid in the primary circuit (10) is mixed with the warm or hot fluid from the device (11) in a thermostatic valve.
10. Method according to Claim 8 or 9,
    characterised in
    that a circulation is provided in the secondary circuit (20), which circulation, adjacent to the tapping point (28), provides a branch-off and return of cooled, unused service water and mixture thereof with fresh supplied service water in the line (22) on the inlet side upstream of the heat exchanger (5).
11. Method according to Claim 10,
    characterised in
    that a pump for this circulation is regulated by a temperature sensor (17, 27, 47).
12. Method according to Claim 11,
    characterised in
    that the circulation pump (44) is turned on when the same temperature sensor reaches threshold values, which sensor turns on the delivery device (14) in the primary circuit (10).

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