WO2020108908A1

WO2020108908A1 - Device for heating a liquid, and corresponding method

Info

Publication number: WO2020108908A1
Application number: PCT/EP2019/079801
Authority: WO
Inventors: Johannes Laging; Daniel Pless; Peter Wickelmaier
Original assignee: Truma Gerätetechnik GmbH & Co. KG
Priority date: 2018-11-29
Filing date: 2019-10-31
Publication date: 2020-06-04
Also published as: DE102018009377A1

Abstract

The invention relates to a device (1) for heating a liquid. The liquid flows from a liquid inlet (10) to a liquid outlet (11) in a flow direction (F) and pushes forward the liquid located in a liquid storage device (2). A heating device (2) transfers thermal energy to the liquid. The liquid storage device (3) receives a specifiable amount of the liquid and is arranged upstream of the heating device (2) in the flow direction (F). A return line (4) forms part of a circulation circuit, an inlet (40) being arranged downstream of the heating device (2) and a mouth (41) being arranged upstream of the liquid storage device (3). A pump (42) moves the liquid, and a check valve (43) lets the liquid in the return line (4) flow only in one direction. A control device (5) controls the pump (42) in dependence of a temperature and/or a flow rate. The invention further relates to a method for heating a liquid.

Description

Device for heating a liquid and corresponding method

The present invention relates to a device for heating a liquid. The device is designed, for example, as a water heater, boiler, combination heater or generally as a heater. Furthermore, the invention relates to a method for heating a liquid.

In the simplest case, gas instantaneous water heaters known from the prior art consist of a burner with fan and gas valve and of a flue gas / water heat exchanger. In the instantaneous water heater there is a volume flow sensor, through which it is recognized when a consumption point, e.g. B. a hot water tap is open and hot water is required. The volume flow signal triggers the burner to start. The use of corresponding sensors discloses, for example, DE 20 2008 005 015 U1.

Gas-operated instantaneous water heaters are mainly used for the decentralized provision of hot water (domestic water) in residential buildings. The advantages are the constant and almost unlimited availability of hot water and the small installation space compared to a water boiler.

When installing in residential buildings, the flue gas connection is made directly to the in-house chimney. In this case the burner can start immediately or after a very short pre-purge time. The pre-purge time is the time during which the combustion air fan is active in order to purge the combustion chamber with fresh air. Flushing can prevent accidental deflagrations when the burner is started. Due to the short delay between hot water request and burner start, it usually only takes a few seconds (so-called dead time) until the hot water reaches z. B. the tap is available as a point of consumption.

In order to cause a short dead time, for example in the case of longer water pipes between the burner and the individual consumption points, as can occur in residential buildings, circulation pipes are known in the prior art. Here, water storage is provided as close as possible to the point of use, some of which also function as heat exchangers, see e.g. B. DE 28 51 169 C2, DE 10 2004 018 034 B4, DE 10 2012 024 578 A1, DE 10 2014 108 147 A1, EP 2 503 252 A2 or EP 2 762 789 A1. Examples include DE 298650 A or CH 232072 A.

It is also known, for example, to integrate egg ne space heating in a system in addition to a water consumption point, see e.g. B. US 5,076,494. This is a so-called combination term.

The above-mentioned framework conditions and possibilities change in the event that, for example, a water heater or a combination heater is to be integrated in a motorhome or caravan. Due to different standards and the significantly different installation conditions, significantly longer pre-rinsing times (e.g. 15 seconds) are sometimes required. Such a pre-rinse time means that from the opening of the hot water tap (as the switch-on signal) no hot water is available for the aforementioned 15 seconds, but the system runs for 15 seconds due to the system. The waste of water is not acceptable due to the limited fresh water supply in a mobile home or caravan and also in terms of ecology and economy.

The invention has for its object to propose a device for heating a liquid speed, which can provide hot water as quickly as possible while observing the prescribed pre-rinsing time or another system-related delay until the burner starts.

The object is achieved by a device for heating a liquid, with a liquid inlet, a liquid outlet, a Heizvorrich device, a liquid storage device, a return line, a Steuerervorrich device, a pump and a check valve, the device in a caravan, a mobile home , a vehicle or a boat can be used, wherein liquid flows into the device via the liquid inlet, liquid flows out of the device via the liquid outlet, the liquid flowing from the liquid inlet to the liquid outlet in a flow direction, the liquid storage device being such is designed such that the inflowing liquid advances the liquid located in the liquid storage device, the heating device transferring thermal energy to the liquid, the liquid speed storage device receives a predeterminable amount of the liquid, the liquid storage device being upstream along the flow direction of the heating device, the return line forming part of a circulation circuit in which the liquid circulates, an inlet of the return line being downstream of the heating device, one of which The mouth of the return line is upstream of the liquid storage device, the pump moving the liquid in the return line, the check valve ensuring that the liquid in the return line only flows in one direction, the device further comprising at least one temperature sensor for measurement a temperature of a liquid and / or at least one flow sensor for measuring a flow of a liquid, and wherein the control device as a function of at least one measured temperature and / or at least one measured flow controls the pump.

The device according to the invention is used to heat a liquid, which is, for example, process water. The heating can also be referred to as heating.

The device is in particular designed so that it can be used in a caravan, a mobile home, a vehicle or in a boat. The Vorrich device is therefore in particular not a device such as that used in a house for providing hot water.

The device has a liquid inlet, via which the - alternative name: cold - liquid to be heated is supplied to the device, and a liquid outlet which, for. B. is connected to a consumption point such as a faucet or a shower, etc. and via which the heated liquid leaves the device.

The liquid mainly flows in one direction from the liquid inlet to the liquid outlet. In the following, configurations are discussed in which the liquid partially flows in the opposite direction as part of a circulation. However, the main direction is in the flow direction. The actual heating is carried out by a heating device which generates thermal energy which is transferred to the liquid.

A bridging of the pre-rinsing time is given by the liquid storage device, in which a predetermined amount of the liquid is stored, and preferably at a correspondingly high temperature. If liquid is requested, i. H. If liquid is withdrawn via the liquid outlet, the liquid arrives at the liquid outlet from the liquid storage device. If, in particular, the case exists that the heating device has not yet heated the liquid, the liquid storage device already allows the removal of heated - e.g. B. at a holding temperature or operating temperature - liquid. The liquid storage device is preferably designed such that the liquid is not mixed in it, but that the inflowing liquid “pushes out” the liquid already in the liquid storage device.

The liquid storage device of the heating device is vorgela in the flow direction. Thus, liquid that flows into the device via the liquid inlet first reaches the liquid storage device and only then flows through the heating device. The arrangement of the heater and liquid storage device takes z. B. Consideration of the sometimes longer pre-rinsing time of the heating device or generally the dead time that results for the heating device or may be predetermined.

This ensures that the liquid flowing into the liquid storage device does not mix with the liquid in the liquid storage device, but rather that the incoming liquid pushes the liquid located in the liquid storage device. The liquid flows in, for example, from the liquid inlet. This preferably relates to the liquid that flows into the liquid storage device. The liquid storage device is therefore in particular not a tank in which the liquid can mix as desired and provide general temperature compensation.

According to the invention, it is provided that the device also has a return line, that the return line forms part of a circulation circuit in which the liquid circulates, that an inlet of the return line in the direction of flow of the heating device Direction is downstream, and that an opening of the return line is upstream in the flow direction of the liquid storage device. It is envisaged that the liquid can circulate in order to receive thermal energy preferably through the heating device. Depending on the design, the circulation circuit runs through the heating device and also through the liquid storage device. Correspondingly, the return line opens in the flow direction in front of the liquid storage device. The return line overall directs the liquid downstream of the heater back to the liquid storage device.

According to the invention, it is provided that the device further comprises a pump, that the pump moves the liquid in the return line, that the device further comprises at least one temperature sensor for measuring a temperature of a liquid and / or at least one flow sensor for measuring a flow of a liquid, that the device further comprises a control device and that the control device controls the pump as a function of at least one measured temperature and / or at least one measured flow. The pump effects the circulation, which is controlled as a function of measured quantities of the liquid (temperature and / or flow).

According to the invention, it is provided that the device also has a check valve and that the check valve ensures that the liquid in the return line only flows in one direction. This ensures that the liquid can only flow in one direction in the return line via a check valve. This direction in the return line is in one embodiment in particular opposite to the direction of flow of the liquid from the liquid inlet to the liquid outlet.

The device according to the invention can in particular also be referred to as a water heater or, in an embodiment with water as a liquid, also as a hot water device.

The device according to the invention makes it possible to dispense immediately warmed up liquid from a standby mode. This takes place in particular regardless of a dead time of the heating device that is required until the heating process begins. In particular, it can be avoided that due to the dead time after the initial When the warm liquid is removed, the cold and refilled liquid reaches the liquid outlet. Above all, there is no drop in temperature.

The instantaneous water heater or hot water device according to the invention makes it possible to obtain a very small and light hot water heater compared to a boiler. This is of particular advantage in confined spaces, such as are often found in caravans or motorhomes.

The instantaneous water heater according to the invention also makes it possible to save water, since there is almost no waiting time between turning on the hot water tap and escaping warm water. Preventing the temperature drop is also much more pleasant for a consumer, for. B. in a shower process.

In one embodiment, the storage volume of the liquid speed storage device and a length and a volume of the liquid lead the line on the one hand and the dead time until the heater is started (for example the pre-rinsing time) on the other hand are compared so that at the latest when liquid stored in the liquid storage device and having at least a holding temperature has been completely replaced by the flowing-in liquid and therefore to be heated, the heating device has started the process of heating the liquid. This means that no cold liquid can get to the liquid outlet and a drop in temperature at the tapping point is prevented. Attention should be paid to the design of the liquid storage device and the dimensioning of a liquid line in which the liquid from the liquid storage device z. B. is transported to the tapping point or to the heating device.

One embodiment is such that an outflow of liquid from the liquid outlet causes an inflow of liquid through the liquid inlet. In one embodiment, the amount of liquid withdrawn and the amount of flowing liquid are coupled to one another. In a concomitant design, the amount of liquid in the device is kept constant overall. If liquid is removed, liquid is automatically refilled from the outside. In one embodiment, there is an overpressure, for example, at the liquid inlet which the liquid is refilled. The overpressure is given, for example, by the line pressure of the city connection or by a submersible or pressure pump.

One embodiment provides that the liquid storage device is thermally insulated. The liquid storage device thus stores only the liquid and a temperature loss, but also the absorption of heat is prevented by the thermal insulation.

One embodiment consists in that the heating device has a burner for combusting an air-fuel mixture and a heat exchanger, and in that the burner undergoes a pre-purging process with air before a burning process for a predefinable pre-purging time. The fuel is, for example, a combustible gas (e.g. propane or butane or a mixture thereof) or is a fuel converted to the gaseous state such as e.g. B. Diesel. Alternatively or in addition, the heating device has an electrical heat source. With an electrical heat source, other effects can cause dead time to occur. In this embodiment, the liquid storage device is preferably upstream of the heat exchanger of the heating device.

In one configuration, the circulation circuit is located completely in the device or in a housing which closes the device from the outside.

In an alternative embodiment, the circulation circuit is partly outside a housing of the device and in one embodiment is partly formed by a pipe or line system which is connected to the device or to the housing. In one embodiment, part of the circulation circuit is thus partially moved outwards and into the surroundings of the device.

One embodiment provides that the device further comprises at least one temperature sensor for measuring a temperature of a liquid and / or at least one flow sensor for measuring a flow of a liquid, and that the control device as a function of at least one measured temperature and / or at least one measured flow controls the heater. In this embodiment, the heating device is controlled as a function of measured quantities of the liquid (temperature and / or flow). The control relates in this case on the starting or ending of a process for generating thermal energy or, for example, also on the power of the heating device, with which different amounts of thermal energy are generated and / or transferred to the liquid.

One embodiment consists of the device further comprising a bypass line and a mixing valve, the bypass line for the liquid connecting the liquid inlet to the mixing valve, omitting the heating device and / or the liquid storage device, and the mixing valve in the direction of flow Heizvorrich device is downstream. In this embodiment, a bypass line is provided, which feeds the liquid which is supplied via the liquid inlet and therefore in most cases also cold to a mixing valve for use. The bypass line runs past the heating device and / or the liquid storage device. There is thus preferably no thermal energy absorbed and the liquid carried in the bypass line maintains its inlet temperature. The mixing valve is furthermore preferably supplied with liquid from the liquid storage device and / or liquid that has passed through the heating device. Thus, in one embodiment, it is provided that the mixing valve allows the liquid heated by the heating device to be mixed down to a lower temperature by the liquid of the liquid inlet or the bypass line and to be dispensed via the liquid outlet. In one embodiment, it is therefore provided that an interface is provided, via which a target temperature of the liquid to be dispensed can be specified for the device, so that the mixing valve can be controlled appropriately.

The following configurations relate to the liquid storage device.

One embodiment provides that the liquid storage device is designed as a concentrically extending coil. In this embodiment, the liquid storage device consists of a tube with a circular diameter, for example. The diameter is preferably less than the length that the liquid speed storage device has. The course of the pipe coil is reminiscent of a concentrically wound garden hose. Therefore, there is only a small interaction area of the liquid itself due to the diameter. A correspondingly large storage volume can be produced by the winding, but the outer one Space requirement remains low. In one embodiment, the winding takes place around an axis that runs along the earth's gravity. Preferably, the inflow to the liquid storage device is further along this axis at a lower point. The inflowing liquid thus acts against gravity.

One embodiment consists of the liquid storage device having at least two liquid connections, the liquid storage device having two liquid-carrying areas between the two liquid connections, the two liquid-carrying areas being assigned different heights along a longitudinal axis of the liquid storage device, the liquid storage device having a liquid-carrying riser area and one has liquid-carrying fall area between the two liquid connections, that the liquid-carrying riser area and the liquid-carrying fall area each extend along the longitudinal axis, and that the liquid storage device allows the liquid to flow in different directions in the fluid-carrying riser area and in the liquid-carrying fall area. In one embodiment, the aforementioned liquid storage device has the shape of the capital letter “L”. The fall area and the climbing area are preferably aligned relative to the gravitational pull. In the two liquid-carrying areas, the liquid preferably flows in a plane. In the rising area, the liquid is preferably moved upward against gravity. In one embodiment, the drop area - apart from a certain deflection area - essentially adjoins the riser area.

In one embodiment, the liquid flows into the liquid storage device via a liquid connection serving as an input and passes through a liquid-carrying region which runs essentially at a height of a longitudinal axis of the liquid storage device. From there, the liquid passes the riser area that extends along the longitudinal axis. This is followed by the falling area, which also extends along the longitudinal axis, but in which the liquid flows in a different direction than in the rising area. The liquid then passes through a further liquid-carrying region which is at a different height along the longitudinal axis than the first-mentioned liquid-carrying region. From there, the liquid reaches the liquid connection serving as an outlet. io

According to a further teaching of the invention, the object is achieved by a method for heating a liquid, the liquid being passed through a liquid storage device, thermal energy being transferred to the liquid in a heating device downstream of the liquid storage device, in a flow direction of the liquid the liquid is repeatedly passed through the liquid storage device and / or through the heating device, and wherein thermal energy is transferred to the liquid until a temperature of the liquid - preferably in the liquid storage device - has exceeded a predetermined lower switching threshold.

The method partially serves to implement the operation of the device described above. Therefore, the designs and explanations also apply accordingly to the process, so that repetition is not required. Conversely, the method or refinements of the method provide implementation options for the device, so that the explanations for the method also apply to the device.

It is provided according to the invention that the liquid is passed several times through the liquid storage device and / or through the heating device. Circulation of the liquid is thus provided.

It is provided that thermal energy is transferred to the liquid until a temperature of the liquid - preferably in the direction of the liquid storage device - has exceeded a predefinable lower switching threshold. The liquid is thus heated until it has a certain minimum temperature. In one embodiment, this is achieved in that the liquid is passed through the heating device several times.

One embodiment of the method consists in that at least one preparation step extending over a dead time is carried out between requesting a heating process of the heating device and starting the heating process. The dead time results, for example, from flushing out a burner.

One embodiment of the method provides that a temperature of the liquid is kept in a predeterminable temperature range. The transfer is, for example controlled so that a lower switching threshold but not an upper switching threshold is exceeded.

One embodiment of the method is that the heated liquid is dispensed, preferably as a function of a user control, and that in the event that the required heating power for the dispensed liquid is below a heating power given by the heating device, a heating ge given excess of heating power is transferred to multiple times through the liquid storage device and / or liquid passed through the heating device. In this embodiment, the heating device provides more power than is required for the liquid dispensed. The resulting excess heating power is transferred to a circulating portion of the liquid. It is not the heating power provided by the heating device that is reduced, but rather a preheating of the liquid is brought about.

In particular, there are a multitude of possibilities for designing and developing the device according to the invention. For this purpose, reference is made on the one hand to the claims subordinate to Pa tent Claim 1, on the other hand to the following description of exemplary embodiments in conjunction with the drawing. Show it:

1 is a schematic representation of a first variant of the device with a consumption point,

2 shows a schematic representation of a second variant of the device with a consumption point,

3 shows a schematic representation of part of a third variant of the device with a consumption point,

4 shows a section through a schematic representation of a first variant of a liquid storage device,

Fig. 5 is a spatial and cut representation of a second variant of a liquid storage device and liquid Fig. 6 is a spatial representation of a third variant of a liquid storage device.

1 shows a first variant of the device 1 for heating a liquid. The liquid is, for example, process water. Therefore, the device 1 is connected here as an example via a line system 7 to a water tap as a point of consumption.

The device 1 has a heating device 2 for actually heating the liquid and a liquid storage device 3 for storing an amount of liquid which is dependent on the shape of the liquid storage device 3. The liquid storage device 3 can in particular also be referred to as a buffer memory.

The liquid flows from a liquid inlet 10 to a liquid outlet 11 mainly in a flow direction F indicated here with an arrow and first through the liquid storage device 3 and then through the heating device 2. Along this first path or main path there are a first T1, a fourth T4 and a third temperature sensor T3 and a first flow sensor V1.

The first temperature sensor T1 and the first flow sensor V1 detect the temperature T1 and the flow V1 of the liquid flowing in via the liquid inlet 10. The value for the flow rate V1 is used here to quantify the amount of liquid flowing off via the liquid outlet 11. This is based on the fact that e.g. B. over an excess pressure at the liquid inlet 10, a loss of liquid speed in the device 1 by the flow at the liquid outlet 11 automatically leads to a reflow of the liquid through the liquid inlet 10. The temperature value T 1 of the fresh liquid or here specifically of the fresh water detected by the first temperature sensor T 1 makes it possible to determine which heating power of the heating device 2 is required in order to heat the liquid to a predetermined value.

The fourth temperature sensor T4 between the liquid storage device 3 and the heating device 2 detects the temperature T4 of the liquid that flows from the liquid storage device. Chervvorrichtung 3 flows and which may need to be heated by the heating device 2. This temperature T4 is preferably also used to control the heating process by the heating device 2.

The third temperature sensor T3 is located upstream of the liquid outlet 11 and therefore measures the temperature value T3 of the heated liquid and the device 1 via the liquid outlet 11 leaving the liquid. In one configuration, this value T3 serves to regulate the behavior of the heating device 2 and the circulation of the liquid in the device 1 described below.

The heater 2 itself has a burner 20 which burns an air-fuel mixture and thereby thermal energy z. B. gives off the flue gas, and a heat exchanger 21 which transfers the thermal energy generated by the burner 20 to the liquid.

Parallel to this described main line of guiding the liquid in the device 1 Vorrich runs a return line 4, in which the liquid is returned against the direction of flow F. Overall, a circulation circle is formed. Here, the circulation circuit in particular runs completely within the housing 6 of the device 1. Therefore, the circulation circuit shown here in FIG. 1 can also be referred to as a “small circle”.

The inlet 40 of the return line 4 is located downstream of the heating device 2 and in front of the liquid outlet 11, so that heated liquid flows back. The mouth 41 of the return line 4 is located upstream of the liquid storage device 3.

The return line 4 is assigned a second flow sensor V2, a second temperature sensor T2, a pump 42 and a check valve 43. The temperature T2 determined by the second temperature sensor T2 is the temperature of the returned liquid. The second flow sensor V2 determines the associated flow value V2. Thus, the measured values of the two sensors T2, V2 can be used to describe the properties of the liquid returned in the return line 4. This in turn serves to control the heating device 2 and the pump 42 Pump 42 moves the liquid through the return line 4 and it can also be specified how much liquid is returned. The check valve 43 ensures that only liquid is returned and that liquid does not vice versa from the liquid speed inlet 10 bypassing the heating device 2 or the liquid storage device 3 to the liquid outlet 1 1.

The first T 1, the second T2, the third T3 and the fourth temperature sensor T2 as well as the first V1 and the second flow sensor V2 are connected to a control device 5 - in the variant shown here wirelessly - in order to determine their respective measured values T1, T2,

T3, T4, V1, V2 to be transmitted. Based on the measured values, the control device 5 controls the heating device 2 and the pump 42.

In the following, several exemplary operating phases of the design shown from the device 1 in FIG. 1 are considered.

1. Initial heating and transition to a standby mode.

This goes hand in hand with a “loading” or “filling up” of the liquid storage device 3, which can be referred to here in particular as a buffer loop.

First of all, no consumer connected to the device 1 is active. So z. B. the hot water tap shown here as an example closed. The device 1 is switched on, for example, via a main switch (not shown here), so that the preparation for the standby mode can take place.

The device 1 is already filled with the liquid which is guided by the pump 42 - for example in the form of a circulation pump - through the small circle of the circulation circuit. This allows the liquid - e.g. B. by running several times through the circulation circuit - to warm.

The second temperature sensor T2 measures the temperature T2 of the circulating liquid, which is usually below a lower switching threshold of the heating device 2 (for example 45 ° C.) when the device 1 is switched on as described here. The burner 20 of the heating device 2 is correspondingly switched on by the control device 5, as a result of which the liquid circulating in the circuit is heated. If the second temperature If T2 has an upper switching threshold (e.g. 55 ° C), the burner 20 is switched off again. If there is only a small amount of circulating liquid due to the geometry, the heating is reduced to a short period of time when the heating device 2, which is designed as a continuous-flow heater (for example 16 kW), has a high output.

In one embodiment, the pump 42 also moves the liquid for a certain time after the heating device 2 has been switched off in order to equalize the temperature in the circuit.

The liquid in the liquid storage device 3 has a predetermined operating temperature range and the liquid storage device 3 itself is, so to speak, “charged”. In one embodiment, the device 1 goes into a standby mode.

In standby mode, the temperature is preferably kept rich in an operating temperature range. For example, if the liquid temperature falls below the lower switching threshold, the burner 20 is started. Conversely, if the liquid temperature exceeds the upper switching threshold, the burner 20 is switched off. Only a very simple two-point control is described here as an example.

2. Tap operation and thereby unloading the buffer loop.

In tap operation, a consumption point, here the hot water tap, is opened by a user and liquid flows out of the liquid outlet 11. Due to an overpressure at the device inlet, for example given here, which is given here by the liquid inlet 11, cold liquid, ie here water in the example, flows into the device 1. B. by a submersible pump or a pressure pump (both are known in caravans or motorhomes) or by connecting to the water fixed network.

Based on the measurement signal of the flow sensor V1, the z. B. is designed as a volume flow sensor, it is recognized that water is removed or flows to. In addition, the amount of liquid refilled is recorded quantitatively. The first temperature sensor T1 measures the temperature of the fresh water and the second temperature tursensor T2 the temperature in the return line 4 or in the small circle formed with it. The third temperature sensor T3 measures the temperature of the liquid at the device outlet or in front of the liquid outlet 11. The control device 5 determines a heat requirement from the respective measurement data and initiates a burner start of the burner 20. There may be a delay as a dead time between the switch-on signal and the burning mode, which can be a few seconds depending on the relevant standard.

Due to the check valve 43 in the return line 4, the fresh water essentially only passes through the buffer loop 3 and through the heat exchanger 21. Figuratively speaking, the fresh water pushes virtually the hot water stored in the buffer loop (as an alternative name for the liquid storage device) 3 forth and through the device for liquid outlet 11th

Due to the liquid storage device 3, water was immediately present at the liquid outlet 11, namely until the water stored in the buffer loop 3 has completely escaped and the cold fresh water flows in. The volume and the length of the buffer loop 3 or the pipeline closing on the buffer loop 3 are preferably dimensioned such that the stored amount of water is sufficient to completely bridge the start time of the burner 20 (dead time here, for example, 15 seconds) .

In particular, such an adjustment is made that at the end of the dead time, no cold water has yet entered the heat exchanger 21. Thus, a smooth transition can be made possible between the heat supply from the buffer loop 3 and the heat supply via the burner 20 with the heat exchanger 21.

After the burner has started, the burner 20 heats the inflowing water to a predetermined control temperature (e.g. 50 ° C.).

3. Spigot end and transition to standby mode. This is initially accompanied by a recharging of the buffer loop 3.

The end of the tap is caused by a user or consumer by closing the hot water tap. The first volume flow sensor V1 in the device device 1 now recognizes that water is no longer flowing and that there is no current demand for hot water. The control device 5 then starts the circulating pump 42 in order to enable circulation in the small circle shown here. Since there is still cold water in the buffer loop 3 from the previous tap operation, the temperature T2 measured by the second temperature sensor T2 in a small circle will generally be below the lower temperature limit for starting the burner 20.

The burner 20, which is still active from the previous tap operation, is not yet switched off, but instead heats the small circuit again to the set temperature or switch-off limit. Only then is the burner 20 switched off. The circulation pump 42 remains active for a while in order to equalize the temperature in the circuit. Overall, the liquid storage device 3 is recharged and the device 1 in standby mode.

The control temperature is, for example, the temperature of the liquid at the liquid speed output 1 1, which is controlled in the tap mode. The dead time is the time between the switch-on signal of the heating device 2 and the actual heat emission to the liquid, here via the heat exchanger 21. The dead time is justified by e.g. B. Before flushing the combustion path, system checks of the control, switching times of the gas valve, ignition times, testing of electronic components etc.

In the embodiment described above, the buffer loop 3 is cold after the tap operation and must first be completely “charged” again. In one embodiment, the circulation pump 42 is not switched on only after the tap operation, but rather already after the burner has started.

The maximum circulation quantity (m ₂ ) depends on whether the burner 20 has enough power reserves to additionally provide the colder water in the circuit of the device 1, and - as explained below - in particular on the maximum burner output Q _B. These power reserves are in addition to the burner power that is required to provide hot water at the liquid outlet 1 1.

The relationship is described in detail: In order to keep the output temperature T3 constant, the burner output must always be greater than or equal to the sum of the dissipated heat flows.

The heat flows are:

The heat sinks are the cold fresh water, the components involved in the circuit of the device 1 and the buffer loop 3.

For the aforementioned relationship, this results in: QB— Qw + Qs

With the following sizes: c _WT = heat capacity heat transfer medium

rh ₂ = mass flow small circle

The maximum circulation volume m _{2 is} calculated as follows:

The following applies to the heat flow:

Heat flow Q _B > c _m * m * (T ₃ - T ₄ )

The following applies to the mass flows: m = m _l + m ₂

This results in:

Example: A fictitious device has a heating output of 16 kW. A hot water consumer (e.g. shower), however, only requires an output of e.g. B. from 12 kW. This means that 4 kW are "left" to heat the circuit in parallel and thus at least partially recharge the buffer loop 3.

In a further mode of operation, the buffer loop 3 is used to smooth fluctuations in temperature at the liquid outlet 11. The water stored in the buffer loop 3 acts here as a heat capacity. In order to achieve temperature smoothing, the circulation pump 42 is switched on in the tap mode.

In a further mode of operation, the circulation pump 42 is briefly switched on in standby mode at certain intervals (intervals) in order to enable an improved temperature measurement of the water in the system.

The design of the device 1 in FIG. 2 differs from the design in FIG. 1 in the type of circulation circuit. Since all other components remain the same, they are not described again here.

The circulation circuit is here partially outside the housing 6 and is in particular also formed by the external line system 7 to which the lines of the device 1 are connected.

In the embodiment shown, the input 40 of the return line 4 and the liquid outlet 11 coincide in particular. In this embodiment, the return line 4 runs outside the housing 6. The circulation circuit can therefore also be referred to as a “large circle” in the embodiment shown because of its extension. The above configurations in connection with the small circle of the Vari ante of FIG. 1 can be transferred accordingly to the device 1 with a large circle. Fig. 3 shows for clarity only a section of the device 1 and is here in comparison with the embodiment of Fig. 1 - so with the small circle - be written. Only the differences between the configurations are explained.

There is a mixing valve 80 downstream of the heating device 2 and here also downstream of the small circulation circuit (thus downstream of the inlet 40 of the return line 4). A bypass line 8 begins upstream of the mouth 41 of the return line 4 and leads the liquid coming from the liquid inlet 10 past the heating device 2 and the liquid storage device 3 to the mixing valve 80, so that cold liquid is available at the mixing valve 80 for mixing.

The mixing valve 80 is set to 50 ° C., for example. The mixing valve 80 could set the temperature in the small circuit somewhat higher, or larger temperature overshoots could be permitted (e.g. 60 ° C). By mixing in the cold liquid, the mixing valve 80 allows the outlet temperature to be limited to the aforementioned 50 ° C., for example.

The third temperature sensor T3 is arranged downstream of the mixing valve 80 and can therefore also be used to control the mixing process.

4 to 6 different variants of the liquid storage device 3 are shown. These variants can also be used independently of the device 1 described and thus as separate inventions.

Many geometries are conceivable for the liquid storage device 3. Suitable are those which enable the best possible separation between the stored warm water and the cold water flowing in.

In the case of the variant of FIG. 4, it is a kind of (wound) hose. Due to the large length in relation to the cross-sectional area, there is only very little mixing here. Such a concentrically wound tube is shown in FIG. 4. As can be seen, the diameter is small compared to the longitudinal extent of the liquid storage device 3.

As the cross-sectional area increases in relation to the length, the mixing generally increases.

In the embodiment of the liquid storage device 3 of FIG. 5, the liquid flows through the lower liquid connection 31 serving here as an input. From there, the liquid flows in the lower liquid-carrying region 33, which here extends over a height region along the longitudinal axis 30. A height can thus essentially be assigned to the area 33 carrying the liquid. Here corresponds - as shown here - the longitudinal axis 30 of the direction of gravity. The liquid moves in the rising region 35 against the gravitational pull of the earth in order to flow down into the falling region 36 at the upper tip. From there, the liquid moves in the upper liquid-carrying region 34 to the liquid connection 32, which functions here as an outlet.

The path of the liquid is intended to prevent the cold inflowing liquid from mixing with the warm liquid already in the liquid storage device 3. The design of the flow channels together results in a shape in the manner of the capital letter “L”.

In the liquid storage device 3 of FIG. 6 there are between the liquid connections 31, 32, which - as indicated by the arrows - serve as an inlet or outlet for the liquid, here four layers, each of which is one height long are assigned to the longitudinal axis 30. The liquid passes through the meandering layers, which are arranged one above the other and each separated by partitions. The partitions are sufficiently distant from one side wall, so that there is a gap for the liquid to rise into the next higher layer. Reference symbol list

1 device

2 heater

3 liquid storage device

4 return line

5 control device

6 housing

7 pipe system

8 bypass line

10 liquid inlet

11 liquid outlet

20 burners

21 heat exchangers

30 longitudinal axis of the liquid storage device

31 Liquid connection of the liquid storage device

32 Liquid connection of the liquid storage device

33 liquid-carrying area of the liquid storage device

34 liquid-carrying area of the liquid storage device

35 fluid-carrying riser area of the fluid storage device

36 liquid-carrying drop area of the liquid storage device

40 Incoming return line

41 Mouth of the return line

42 pump

43 check valve

80 mixing valve

F flow direction

T1 temperature sensor

T2 temperature sensor

T3 temperature sensor

V1 flow sensor

V2 flow sensor

Claims

1. Device (1) for heating a liquid,

With a liquid inlet (10), a liquid outlet (1 1), a heating device (2), a liquid storage device (3), a return line (4), a control device (5), a pump (42) and a check valve (43) ,

the device (1) being usable in a caravan, a mobile home, a vehicle or a boat,

wherein liquid flows into the device (1) via the liquid inlet (10),

wherein liquid flows out of the device (1) via the liquid outlet (1 1),

wherein the liquid flows from the liquid inlet (10) to the liquid outlet (1 1) in a flow direction (F),

wherein the liquid storage device (3) is designed such that the inflowing liquid pushes the liquid in the liquid storage device (2) forward,

wherein the heating device (2) transfers thermal energy to the liquid, the liquid storage device (3) absorbing a predeterminable amount of the liquid,

the liquid storage device (3) being arranged upstream of the heating device (2) along the flow direction (F),

the return line (4) forming part of a circulation circuit in which the liquid circulates,

an input (40) of the return line (4) downstream of the heating device (2) in the flow direction (F),

wherein an opening (41) of the return line (4) in the flow direction (F) of the liquid speed storage device (3) is upstream,

the pump (42) moving the liquid in the return line (4), the check valve (43) ensuring that the liquid in the return line (4) only flows in one direction,

the device (1) further comprising at least one temperature sensor (T1, T2, T3, T4) for measuring a temperature of a liquid and / or at least one Flow sensor (V1, V2) for measuring a flow of a liquid, and

wherein the control device (5) controls the pump (42) as a function of at least one measured temperature and / or at least one measured flow.

2. Device (1) according to claim 1,

wherein an outflow of liquid from the liquid outlet (1 1) causes an inflow of liquid through the liquid inlet (10).

3. Device (1) according to claim 1 or 2,

wherein the heating device (2) has a burner (20) for burning an air / fuel mixture and a heat exchanger (21), and

wherein the burner (20) undergoes a pre-purging process with air before a baking process for a predefinable pre-purging time.

4. Device (1) according to one of claims 1 to 3,

wherein the device (1) further comprises a housing (6), and

wherein the return line (4) at least partially belongs to a line system (7) located outside the housing (6) for carrying liquid.

5. Device (1) according to one of claims 1 to 4,

wherein the device (1) further comprises at least one temperature sensor (T1, T2, T3, T4) for measuring a temperature of a liquid and / or at least one flow sensor (V1, V2) for measuring a flow of a liquid, and

wherein the control device (5) controls the heating device (2) as a function of at least one measured temperature and / or at least one measured flow.

6. Device (1) according to one of claims 1 to 5,

wherein the liquid storage device (3) is designed as a concentric pipe coil.

7. Device (1) according to one of claims 1 to 5,

wherein the liquid storage device (3) has at least two liquid connections (31, 32),

wherein the liquid storage device (3) has two liquid-carrying areas

(33, 34) between the two liquid connections (31, 32),

the two liquid-carrying areas (33, 34) being assigned different heights along a longitudinal axis (30) of the liquid storage device (3),

wherein the liquid storage device (3) has a liquid-carrying riser area (35) and a liquid-carrying drop area (36) between the two liquid connections (31, 32),

wherein the liquid-carrying rising area (35) and the liquid-carrying falling area (36) each extend along the longitudinal axis (30), and

wherein the liquid storage device (3) allows the liquid to flow in different directions in the liquid-carrying riser area (35) and in the liquid-carrying fall area (36).

8. method of heating a liquid,

wherein the liquid is passed through a liquid storage device (3),

wherein in a liquid storage device (3) in a flow direction (F) of the liquid downstream heating device (2) thermal energy is transferred to the liquid,

wherein the liquid is passed several times through the liquid storage device (3) and / or through the heating device (2), and

whereby thermal energy is transferred to the liquid until a

Temperature of the liquid has exceeded a specifiable lower switching threshold.

9. The method according to claim 8,

the preparation step being carried out between a request for a heating process of the heating device (2) and a start of the heating process, which extends over a dead time.

10. The method according to claim 8 or 9,

wherein a temperature of the liquid is kept in a predeterminable temperature range.

11. The method according to any one of claims 8 to 10,

wherein - preferably depending on a user control - the heated liquid is dispensed, and

in the event that a required heating power for the liquid dispensed is below a heating power given by the heating device (2), an excess heating power given by the heating device (2) is repeated by the liquid storage device (3) and / or by the Heating device (2) liquid passed through is transferred.