DE102018126072A1 - Hot water tank - Google Patents

Abstract

A hot water tank (1) with a storage tank (10) with a heating unit (13), a cold water inlet (41) and a hot water inlet (42) is provided. The hot water tank also has a control unit (20) and a sensor unit (30) which has a temperature sensor (32) which detects the temperature of a pipe of the cold water inlet (41). The control unit (20) is designed to use the temperature profile of the pipe temperature determined by the temperature sensor (32) to determine a duration of the tap and an energy content of the hot water within the storage tank.

Description

The present invention relates to a hot water tank and a method for controlling a hot water tank.

A hot water storage tank is used for hot water supply and typically has a storage tank in which hot water can be stored.

In order to reduce the electrical energy requirement for the hot water supply, it is known to determine an energy content of the water within the reservoir by means of a sensor and to make a forecast for the future heat requirement on the basis of the respective temperature changes. Furthermore, e.g. B. an integral sensor can be provided in the memory to determine a residual amount of use for a mixed water amount.

Dabei ist c_p die spezifische Wärmekapazität der Flüssigkeit im Speicher. Die Änderung des Wärmeinhaltes ist ein Maß für den Wärmebedarf. Für diese Art der Wärmebedarfsbestimmung sollten mehrere Sensoren vorhanden sein. Für den Einsatz in modernen Systemen ist diese Art der Wärmebestimmung aufgrund der hohen Kosten für viele Temperatursensoren jedoch nicht geeignet.A temporally resolved determination of the heat requirement of the storage tank is a challenge that is becoming increasingly important for energy-efficient heating systems, even for standard systems. A heat requirement of a storage tank can typically be recorded in two different ways. On the one hand, several N temperature sensors T _i can be introduced into the memory and the heat content can be calculated using the total volume V. The calculation depends on the local distribution of the sensors. With a uniform distribution, for example, the heat content Q results in $$Q=c_p\ast V\ast \frac{1}{N}{\displaystyle \sum _{i=1}^N{T}_i}$$

Here c _{p is} the specific heat capacity of the liquid in the storage. The change in the heat content is a measure of the heat requirement. Several sensors should be available for this type of heat demand determination. However, this type of heat determination is not suitable for use in modern systems due to the high costs for many temperature sensors.

The second way of determining the heat requirement is to use an integral sensor in the memory. Such a sensor traverses a memory vertically and changes its electrical resistance depending on the current material temperature. The integral sensor can represent a series of very many individual temperature sensors that are connected in series. From the measured resistance, conclusions can now be drawn about the total heat in the store. However, the absolute temperature is lost, so that such a sensor is almost always used in combination with another individual temperature sensor. The change in the heat content over time also describes the demand. This pair of sensors is potentially suitable for use in modern systems, but is also not inexpensive to implement.

Both available systems are not well suited for retrofitting existing systems.

It is an object of the present invention to provide a hot water tank and a method for controlling a hot water tank, which enables a more precise determination of an energy content of the water in the tank.

This object is achieved by a hot water tank according to claim 1 and by a method for controlling a hot water tank according to claim 4.

The invention relates to the idea of providing a temperature sensor on a pipe of a cold water inlet and detecting the temperature of the pipe. During a hot water tap, cold water flows into the storage tank and thus cools down the inlet pipe and thus the sensor unit. After the tap is finished, the temperature of the inlet pipe and the sensor unit adapts to the ambient temperature. On the basis of the change in temperature of the pipe of the cold water inlet, an amount of energy of the water in the storage can be determined. According to the invention, the energy content of the water in the reservoir is thus determined based on the temperature of the pipe of the cold water inlet.

The sensor unit according to the invention can thus be used to determine information about tapping operations and about energy withdrawal from the store without intervening directly in the store. Such a sensor unit can thus also be used in existing hot water storage tanks without having to intervene in the storage tank itself. Advantageously, the energy content of the water in the reservoir can be determined more precisely than in the prior art, where typically only a temperature inside the reservoir is measured. The information about the actual energy content of the water in the storage can be used for forecasting demand and thus for more efficient energy management.

According to one aspect of the present invention, the sensor unit has a heating unit for heating the temperature sensor when the Ambient temperature is lower than the cold water inlet temperature.

The present invention relates to all types of liquid stores, in particular water stores, which are used to store thermal energy and are emptied by a downstream system / process. In particular, the invention addresses storage in heating and sanitary engineering. The process is suitable for different designs, sizes and purposes.

Further embodiments of the invention are the subject of the dependent claims.

• 1 zeigt eine schematische Darstellung eines Warmwasserspeichers gemäß einem Aspekt der vorliegenden Erfindung,
• 2 zeigt einen Temperaturverlauf einer Temperatur eines Kaltwasserzulaufes gemäß einem Aspekt der vorliegenden Erfindung,
• 3 zeigt einen Graphen zur Veranschaulichung des Zusammenhangs zwischen der relativen Wärmemenge und der eingetragenen Wärmemenge, und
• 4 zeigt einen Temperaturverlauf einer Temperatur eines Kaltwasserzulaufes gemäß einem Aspekt der vorliegenden Erfindung.

Advantages and exemplary embodiments of the invention are explained in more detail below with reference to the drawing.

• 1 shows a schematic representation of a hot water tank according to one aspect of the present invention,
• 2nd shows a temperature profile of a temperature of a cold water inlet according to an aspect of the present invention,
• 3rd shows a graph to illustrate the relationship between the relative amount of heat and the amount of heat entered, and
• 4th shows a temperature profile of a temperature of a cold water inlet according to an aspect of the present invention.

1 shows a schematic representation of a hot water tank according to an aspect of the present invention. The hot water tank 1 according to the invention has a storage container 10th on which optionally has at least one temperature sensor 11 and a heating unit 13 can have. The heating unit 13 can serve to keep the water inside the storage tank 10th to warm up. Furthermore, the memory 10th a cold water inlet 40 with a cold water inlet pipe 41 and a hot water drain 42 or hot water connection 42 on. The cold water inlet 40 with a cold water pipe 41 serves cold water to the storage tank 10th feed.

There is also a control unit 20th to control the operation of the hot water tank 1 intended. There is also a sensor unit 30th for detecting a temperature T _R of the cold water pipe 41 intended. The sensor unit 30th is on or at the cold water inlet 41 arranged and has a temperature sensor 32 on. Optionally, the sensor unit 30th a heating unit 31 exhibit. The temperature sensor 32 detects the temperature T _R of the pipe 41 of the cold water inlet 40 . The temperature sensor 32 is therefore not in direct contact with the water in the inlet 40 .

If the ambient temperature of the temperature sensor 32 is slightly higher or lower than the cold water inlet temperature, then can be done using the heating unit 31 heating or warming the temperature sensor 32 respectively. Optional insulation 33 around the sensor unit 30th be provided around.

Via a hot water connection 42 can hot water with a temperature T _off from memory 10th be tapped. With such a hot water tap, cold water flows at a temperature T _too then through the pipe 41 in the store 10th . Because cold water through the pipe 41 flows and the cold water has a lower temperature than the sensor 32 has, this leads to a cooling of the pipe 41 and thus the temperature sensor 32 . When the tap is finished, no cold water flows in and the pipe 41 will warm up to ambient temperature again.

The volume flows in the inlet keep the balance with all volume flows in the outlet (continuity law). Heat can be introduced either through additional inlets or outlets or through an integrated heat exchanger.

A precise structural knowledge of the reservoir (e.g. the insulation or pipe diameter) is not required in the method according to the invention. The method according to the invention for determining the heat requirement is based on continuously sampled temperature values of the inlet pipe by means of the second temperature sensor 32 . To determine the heat requirement, it is necessary that the inlet temperature ( T _too ) has a temperature difference to the ambient temperature of the temperature sensor. However, this condition is typically met for hot water systems, since water pipes run in the ground and is therefore colder than at the storage location in the building. Additionally is in the storage tank 10th another heat generator 13 (eg: a heat pump) that supplies the heat exchanger with heat output.

2nd shows a temperature profile of a temperature of a cold water inlet according to an aspect of the present invention. To determine the heat requirement, a temperature measurement is carried out before, during and after a hot water use process in / at the inlet. By using heated water from the storage tank 10th removed and cold water flows in, this is from the temperature sensor 32 directly on the inlet pipe 41 measured. This results in a characteristic due to the heat conduction Temperature profile, which for an exemplary use of ( t ₀ ) to ( t ₁ ) is shown.

In 2nd is not only the strong drop in temperature due to use, but also the characteristic PT1 behavior both during cooling and during reheating driven by the room temperature ( T _dream ) visible. The PT1 behavior results from the step response of the temperature difference between the temperature of the inflowing water ( T _too ) and the room temperature ( T _dream ), which can be regarded as constant for a usage process. The start of the tap t ₀ is determined by the sharp drop in temperature, the end time t ₁ by changing the sign of the temperature change.

bestimmbar und zum zweiten die Zeitkonstante (τ) der Abkühlfunktion (T_ab ) $$T_{ab}=T\left(t_0\right)e^{-\tau t}$$

Die genaue Bestimmung der Zeitkonstante kann dabei durch unterschiedliche Verfahren erfolgen. Beispielsweise kann hier eine Approximation mittels des Least Squares Verfahren genutzt werden. Die Zeitkonstante selber gibt Aufschluss über den relativen Volumenstrom V̇_rel~τ im Zulauf, da dieser direkt mit dem Energiegehalt und damit der Temperatur und der Temperaturentwicklung des durch den Zulauftemperatursensor gemessenen Volumenelements korreliert.By evaluating the temperature profile in the control unit 20th two pieces of information become accessible. On the one hand, the period of use (t _use ) is through $$t_{nut\mathrm{e.g.}}=t_1-t_0$$

determinable and secondly the time constant (τ) of the cooling function ( T _off ) $$T_{ab}=T\left(t_0\right)e^{-\tau t}$$

The exact determination of the time constant can be done using different methods. For example, an approximation using the least squares method can be used here. The time constant itself provides information about the relative volume flow V̇ _{rel ~ τ} in the inflow, since this correlates directly with the energy content and thus the temperature and temperature development of the volume element measured by the inflow temperature sensor.

Dabei ist T_KW die Temperatur des Wassers im Zulauf, die durch eine einzelne längere Nutzung, wie sie im Normalfall mehrfach täglich vorkommt, bestimmt werden kann. Diese Temperatur wird in einem größeren Zeitrahmen (z.B. wöchentlich) beobachtet und aktualisiert.Both information together directly result in the relative heat requirement: $$E_{wÄrme,rel}=t_{nut\mathrm{e.g.}}{\dot{V}}_{rel}{c}_p{\rho }_{wasser}\left(T_{ab}-T_{KW}\right)$$

It is T _KW the temperature of the water in the inlet, which can be determined by a single long period of use, which normally occurs several times a day. This temperature is observed and updated in a larger time frame (eg weekly).

3 zeigt einen Graphen zur Veranschaulichung des Zusammenhangs zwischen der relativen Wärmemenge und der eingetragenen Wärmemenge. Aufgrund von unterschiedlichen baulichen Gegebenheiten, wie zum Beispiel unterschiedliche Rohrdurchmessen oder Rohrquerschnitte), kann zur Bestimmung der absoluten Wärmemenge die relative Wärmemenge mit der insgesamt durch die Heizanlage eigetragen Energiemenge korreliert werden. Dazu wird die durch die Heizanlage täglich die eingetragene Energiemenge mit der relativen Energiemenge verglichen. Da die eingetragene tägliche Energiemenge von Heizanlagen unabhängig erfasst wird, entsteht hierdurch kein zusätzlicher Aufwand. Werden beide Größen über mehrere Tage mit unterschiedlichen Energiebedarfen verglichen ergibt sich ein linearer Zusammenhang, der in 3 gezeigt ist.The total daily requirement of the relative energy results from a summation of E _{heat, rel} for all tapping operations of the entire day. $$E_{taG,rel}={\displaystyle \sum _{i=1}^n{E}_{wÄrme,rel,i}}$$

3rd shows a graph to illustrate the relationship between the relative amount of heat and the amount of heat entered. Due to different structural conditions, such as different pipe diameters or pipe cross sections), the relative amount of heat can be correlated with the total amount of energy entered by the heating system to determine the absolute amount of heat. For this purpose, the amount of energy entered by the heating system is compared daily with the relative amount of energy. Since the daily amount of energy entered by heating systems is recorded independently, there is no additional effort. If the two quantities are compared over several days with different energy requirements, a linear relationship results, which in 3rd is shown.

Damit ist direkt und noch während des Zapfvorgangs der Wärmebedarf bestimmbar. Durch diese Information sind Heizsysteme, insbesondere Energiemanagementsystem, besser in der Lage den Kundenkomfort mit möglichst geringer Aufnahmeenergie zu gewährleisten, denn es lassen sich deutlich bessere Prognosen des zeitaufgelösten Wärmebedarfes erstellen.The slope (k) can be determined by a linear regression and thus a direct functional relationship to the determination of the thermal energy. This connection applies to every single tap. $$E_{wÄrme}=k{E}_{wÄrme,rel}$$

This means that the heat requirement can be determined directly and while the tap is still being drawn. With this information, heating systems, in particular energy management systems, are better able to ensure customer comfort with the lowest possible absorption energy, because significantly better forecasts of the time-resolved heat requirement can be made.

4th shows a temperature curve of a temperature T _R a cold water inlet according to an aspect of the present invention. At the time t ₁ hot water is drawn off via the connection 42 , causing cold water to flow through the pipe 41 runs after and the temperature T _R of the pipe sinks. After the tap is finished, the temperature rises T _R of the pipe back on and at the time t ₂ another tap takes place so that the temperature T _R the pipe sinks again.

According to the invention, the temperature can drop from the gradient T _R a cold water flow can be determined. The duration of the temperature drop provides information about the duration of the tap. If there is a long tap, the temperature will decrease T _R of the pipe up to the temperature of the cold water. An area below the ambient temperature is proportional to the energy supplied to the storage. This information can be determined over a few days using the known information of the energy introduced by the heat generator during the course of the day. With the control unit according to the invention 20th a precise prognosis of the energy demand or progress of the hot water tank can be determined. This information can be used, for example, the heating unit 13 in the store 10th Activate early to increase the amount of hot water inside the storage tank.

According to a further aspect of the present invention, the pipe temperature can be monitored T _R a pipe break can be determined. This is because the pipe temperature T _R is lower than the ambient temperature for a long time.

According to one aspect of the invention, leakage detection can take place. If there is a permanent temperature difference (T _to - dream) without clearly recognizable hot water use, this is an indication of a very small but steady volume flow. After a certain waiting period, this volume flow is recognized as a leak in the water supply system (e.g. a leaky hot water mixer tap).

Claims (5)

Hot water tank (1), with a storage tank (10) with a heating unit (13), a cold water inlet (41) and a hot water outlet (42), a control unit (20), and a sensor unit (30), which has a temperature sensor (32) , which detects the temperature (T _R ) of a pipe of the cold water inlet (41), the control unit (20) being designed to use a temperature profile of the pipe temperature (T _R ) determined by the temperature sensor (32) to determine a duration of the tap and an energy content to determine the hot water within the storage tank (10). Hot water tank (1) after Claim 1 wherein the sensor unit (30) has a heating unit (31) for heating the temperature sensor (32) when the ambient temperature of the temperature sensor (32) is lower than the cold water inlet temperature. Hot water tank (1) after Claim 1 or 2nd , The control unit (20) being designed to detect an area below the ambient temperature in a temperature-time characteristic of the pipe temperature (T _R ) and to determine an energy content of the hot water therefrom. Method for controlling a hot water tank (1), which has a storage tank (10) with a heating unit (13), a cold water inlet (41) and a hot water outlet (42), and a sensor unit (30) with a temperature sensor (32), with the steps : Detecting a pipe temperature (T _R ) of a pipe of a cold water inlet (41) by the temperature sensor (32), and determining a duration of a tap and / or an energy content of the hot water within the storage tank (10) based on the pipe temperature (T _R ). Procedure for controlling a hot water tank after Claim 4 , further comprising the step of: heating the temperature sensor (32) of the sensor unit (30) when an ambient temperature of the temperature sensor (32) is less than the cold water inlet temperature.

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