DE10341523A1 - Warm water provider, in particular, for aircraft comprises a water pipe passing through an insulated tank with a heat storage medium, an electric heater, and a temperature sensor - Google Patents

Abstract

The warm water provider, in particular, for aircraft comprises a water pipe (1) passing through an insulated tank (4) with a liquid heat storage medium (2), an electric heater (5), and a temperature sensor (62) connected to a unit (6) controlling heater operation.

Description

The The invention relates to a water heater for vehicles, in particular for aircraft, under Use of an electric heating element and a thermal Insulation container, especially for Applications in which the hot water preparation narrow limits on energy consumption and water storage are set.

to Water heating become conventional in the stationary Operation boilers or water heaters used for their high energy and space requirements or - with low volume and energy consumption - insufficient constant hot water temperatures are known. Such types of hot water heaters are for mobile applications (e.g. Automotive technology or aviation) already therefore unsuitable because there only low electrical power (a few hundred watts) to disposal stand and the water heaters should be compact and frost-proof and high safety standards.

In The aircraft are, for example, hot water boiler Goodrich in use, which are described as a water heater. So far one of the Goodrich website can take, the boiler has a capacity of only 1.5 l, so that the hot water supply should be exhausted very quickly or by inflowing cold water already before removing the specified nominal amount of water, the temperature considerably decreases.

In Patent application US 2003/0021597 A1 describes a water heater for aviation applications, the three closely spaced parallel heating tubes with Contains resistance heating elements, the heating tubes separately connected to a 3-phase power supply and with respect to the Water flow are connected in series. The water heater has in each heating tube over one Temperature sensor, the current when reaching a limit temperature off. In a preferred variant is for the energy flow sensor provided so that the heater in the tubes at water extraction already then turn on again when the temperature sensors are still on show no need. The disadvantage is the immense effort for the Power supply (three-phase circuit), which is not recognizable constant kept water temperature for the Case that the amount of water removed exceeds the tube volume, as well as the energy peak load in the withdrawal period.

The Patent Application US 2003/0012564 A1 discloses a water heater for aircraft, a built-in float switch to prevent power on, if there is no water in the tank and a temperature adjustable between 41 ° C and 85 ° C Thermostat has. With a tank made of polypropylene is the Frost resistance reached. The water heater is based on the boiler principle by a pressure-free tank at the temperature preselected by the thermostat held and the cold water by means of control over the Float switch refilled becomes.

adversely Here is that the kept water volume in the tank limited is and by the inflowing cold water the selected temperature can not be held or with larger volume of the tank Power consumption correspondingly higher must be to the larger volume on the selected one Keep temperature level.

Of the Invention is based on the object, a new way for water heating in vehicles, in particular in aircraft, to find that in a small space with a water heating low power consumption without allowing the removable Amount of water is limited to a stored tank volume.

According to the invention Task with a water heater for vehicles, in particular for aircraft, in which an electric heating element is arranged in a thermal insulation container is and in the isolation tank a first pipe end for the cold water supply and a second pipe end for the hot water outlet are initiated, characterized in that the insulation container is filled with a liquid heat storage medium, that between the first pipe end and the second pipe end a waterproof Pipe to the flow of the heated Water through the liquid Heat storage medium is present, the tube has a large relative surface inside the heat storage medium to achieve faster enthalpy transitions, and that the electric heating element with both the water-carrying pipe and with the Heat storage medium is in thermal contact with a control unit for regulation the power of the heating element as a function of at least one Temperature sensor that detects the temperature of the heat storage medium, is available.

Advantageous is used as a heat storage medium synthetic oil, preferably a synthetic mineral oil or silicone oil is used.

Because of the most required physiological safety for the to be heated Useful water (often drinking water) is the pipe expediently made of stainless steel.

The Pipe is advantageously performed in such a geometry through the insulation container, that the first pipe end for the cold water supply below and the second pipe end for the hot water outlet above each the isolation tank transverse section or part of the tube is arranged, so that when loading or vent of the pipe at the two pipe ends the water in the pipe independent (except for small residues) can proceed. This residual quantity may only be that big that with multiple freezing and thawing of the water residue no mechanical damage of the pipe occurs (frost protection of the water heater).

It proves especially for the operating condition of the water-flow pipe (i.e. as cheap, that between at least one located in the heat storage medium linear section of the tube and the heating element a massive thermal bridge high thermal conductivity to increase of the direct enthalpy transition is arranged by the heating element on the water in the pipe. The material of the thermal bridge should while a thermal conductivity of at least 100 watts per meter and Kelvin. That's why come as thermal bridge appropriate materials, such as copper, aluminum or their alloys used.

The Thermal bridge is preferably formed as a solid perforated plate, wherein the Perforated plate a plurality of recesses for receiving the heating element and has at least one linear portion of the tube. This will be the perforated plate appropriate made of a densely pressed aluminum profile.

It proves to be an advantageous design when the pipe as multiple U-shaped bent tube is formed, wherein at least one vertical U-bend, consisting of two linear sections and a curved section, in the heat storage medium is immersed and another curved part of the tube over the Edge of the cup-shaped thermos guided and connected to the first pipe end below the bottom of the insulating container is.

In another expedient design the tube inside the heat storage medium a surface extension to enlarge the to the enthalpy transition existing surface on. This can be the surface extension advantageous as a coiled tubing in the manner of a heat exchanger or as a section-wise pipe extension for receiving a limited Water supply within the heat storage medium accomplished be. The volume within the pipe extension should be less as a liter, preferably less than three quarters of a liter of water contain. The tube extension can be used to increase the surface area in the heat storage medium as an n-shaped prism-shaped or is designed as a cylindrical extension of the pipe cross-section.

In an advantageous variant of the water heater is along the coiled tubing a resistance heating element mounted so that a direct thermal contact of the heating element to the tube and to the heat storage medium consists.

A Further embodiment of the invention provides as a surface extension expedient a hose coil with integrated resistance heating in front, allowing a more direct thermal Contact of the heating element to the water fed in the pipe and to the heat storage medium consists.

to Improvement of the direct enthalpy transition are heating element and surface extension of the tube arranged in a massive thermal bridge are, with the thermal bridge as a perforated plate is formed and heating element and surface extension fitted in different cylindrical recesses of the perforated plate are.

In a further advantageous embodiment can the surface extension of the tube from a combination of within the heat storage medium successively arranged coiled tube and cylindrical tube extension consist. It is again advantageous if at least the cylindrical pipe extension together with the heating element in one massive thermal bridge arranged is, wherein heating element and tube extension into different cylindrical recesses the thermal bridge fitted are.

The provided for heating element control unit is in addition to in the heat storage medium arranged temperature sensor expediently with further temperature and / or safety switches in conjunction and has a microcontroller for optimum control and regulation of the discharged hot water on. There are additional Safety switch, which are designed as a limit switch advantageous in the control unit directly with means for interrupting the power supply connected to the heating element or serve mainly the redundancy of temperature monitoring in the heat storage medium and at the hot water outlet (second pipe end) and the overtemperature shutdown as well as a fill level monitoring the heat storage medium.

The control unit can also be advantageous with an extraction unit for the extraction of useful water is a connection, wherein the microcontroller is connected via an interface with the extraction unit to take over the control and master function for all contained in the extraction unit electronically controlled components.

With the above-described solution according to the invention, it is possible a Water heating in vehicles, in particular aircraft, to realize that with low space requirement with a reliable water heating low power consumption without allowing the removable Amount of water is limited to a stored tank volume.

The Invention will be explained below with reference to exemplary embodiments. The drawings show:

1 : a schematic diagram of the water heater according to the invention,

2 FIG. 2: a longitudinal section through the hot water heater according to the invention with a double U-shaped pipe run, FIG.

3 : a representation of the water heater according to the invention with surface enlargement in the form of a coiled tubing,

4 a further design of the surface extension of the pipe with a directly heated hose coil,

5 a further embodiment of the surface extension of the tube with a cylindrical tube extension in combination with a coiled tubing according to 3 ,

In a basic version of the water heater according to 1 is a watertight tube 1 , Which contains the water to be heated and if necessary (when opening a faucet) is traversed by this water, with any cross-sectional geometry in a liquid heat storage medium 2 arranged, with the tube 1 the largest possible outer surface to a heat storage medium 2 has that in an isolation tank 4 located. A heating element 5 is also in the heat storage medium 2 submerged and heated the latter to a defined temperature level. In addition, the tube 1 and the heating element 5 through a massive thermal bridge 3 connected for rapid heat transfer, the thermal bridge 3 also in the heat storage medium 2 is submerged and serves faster enthalpy transitions.

The pipe 1 has a first pipe end 11 as cold water inlet and a second pipe end 12 as hot water outlet on. The normal flow direction when removing (heated) water thus goes from the first pipe end 11 to the second pipe end 12 ,

The isolation tank 4 , the heat storage medium 2 thermally shielded from the environment, closes the tube 1 between the pipe ends 11 and 12 and has for this purpose recesses for the inlet and outlet of the pipe 1 ,

The pipe 1 It is designed so that it has the largest possible surface area for the heat storage medium 2 and at the same time can be easily emptied due to gravity (ventilation for frost protection). The gravitational potentials in the course of the pipe 1 are aligned for the shown normal position of the water heater so that when ventilation of the pipe ends 11 and 12 to the environment in the pipe 1 located water can run independently of small residues. The remaining water remains between the pipe ends 11 and 12 Freeze and defrost as often as you like, without the structure of the tube 1 irreversibly damage.

The thermal bridge 3 consists of a material with high thermal conductivity (> 100 watts per meter and Kelvin, such as aluminum or copper). It serves as an intensified heat conductor between the water-filled pipe 1 , the heat storage medium 2 and an active heating element 5 , For this purpose, the thermal bridge encloses the active heating element 5 and one or more sections 13 of the pipe 1 ,

The heating element 5 , which may for example consist of conventional heating tubes or PTC heating elements, must meet the aviation or vehicle technology usual safety requirements, low weight and volume and low power consumption (eg in aviation: 200 - 400 VA of a single AC phase of the on-board power supply) exhibit.

The temperature of the hot water to be delivered is essentially determined by the temperature of the liquid heat storage medium 2 set. For temperature control and possibly other comfort and / or safety-relevant variables is a control unit 6 present, the at least one control chip and a temperature sensor 62 in the heat storage medium 2 at a suitable location near the cold water inlet 11 is attached, contains and ensures that the heat storage medium 2 constantly has a sufficiently high temperature for heating the water and an upper Does not exceed limit temperature.

With the help of the control unit 6 , which controls a power electronics in a known pulse-pause operation (TRIAC), the output power of the heating element 5 regulated. The control unit 6 evaluates the resistance value of the temperature sensor 62 in the heat storage medium 2 to its temperature on the supplied electric power of the heating element 5 to keep constant.

According to 2 can the pipe 1 bent in a U-shape, in fact a double U-bend is used to the first pipe end 11 , which represents the cold water inlet, below a second pipe end 12 , which acts as a hot water outlet, and below the lower curved part 14 of the pipe 1 to arrange. By "bottom" is meant the direction of natural gravitation.The purpose of this measure is the simple drainage of the useful water during ventilation of the pipe ends 11 and 12 (Frost protection). 2 shows the course of the double U-bow so that only a curved part 14 within the heat storage medium 8th is located while the upper curved part 14 of the pipe 1 serves to the closed vessel wall of the cup-shaped insulation container 4 to overcome. But there are also multiple U-bends within the isolation tank 4 possible.

The thermal bridge 3 (from 1 ) is in the example according to 2 a pressurized solid perforated plate 31 made of aluminum and serves as an intensified heat conductor between the active heating element 5 , the pipe 1 and the heat storage medium 2 , It has three cylindrical recesses 32 in it and encloses two linear sections 13 of the pipe 1 as well as the active heating element 5 where the heating element 5 conveniently between the through the curved part 14 connected linear sections 13 of the U-shaped tube 1 is arranged. Curved parts 14 of the pipe 1 are intended for manufacturing reasons of the thermal bridge 3 be left out, but can also be included if necessary.

The perforated plate 31 On the one hand, it provides quick thermal contact between the active heating element 5 and several (here: 2) sections 13 of the pipe 1 on the other hand - because it is completely from the heat storage medium 2 surrounded - an enlarged effective surface for enthalpy transitions of heating element 5 and pipe 1 to the heat storage medium 2 , This is of importance, as flow of larger amounts of water through the pipe 1 the heating element 5 (because of the limited power consumption) not the necessary enthalpy increase of the water in the pipe 1 can afford, so that the shortfall then from the heat storage medium 2 is supplied. For this purpose, it makes sense that the perforated plate 31 as an embodiment of the thermal bridge 3 not necessarily has a pure plate shape, but also shapes to increase the surface to the heat storage medium 8th may have (eg ribs, pins, additional channels, porous edges, etc.).

The liquid heat storage medium 2 has in addition to the actual memory function nor the task of a thermally dense contact between pipe 1 and the perforated plate 31 and thus fast transition possibilities for the enthalpy between the heat storage medium 2 and the water in the pipe 1 manufacture. The enthalpy may increase during the time without utility water flow since the heating element 5 after the water in the pipe 1 has reached its desired temperature, as long as remains on until an upper limit temperature of the heat storage medium 2 is reached. The control unit takes over 6 Temperature monitoring by means of the temperature sensor 62 and leads by means of a microcontroller 61 a regulation of the power of the heating element 5 by.

In addition, request signals for hot water of a sampling unit 7 (Faucet and / or mixer) via an interface 63 on the microcontroller 61 be transmitted. This allows the microcontroller 61 directly after receiving the request signal for a defined period of time the heating element 5 activate to compensate for a calculated loss of enthalpy as soon as possible.

If the supply of cold water from the first pipe end 11 through a breakthrough in the bottom of the isolation vessel 4 For safety reasons, the upper curved part can 14 and another (bow-free) section 13 of the pipe 1 also within the heat storage medium 2 be arranged to the surface of the pipe 1 for heat absorption from the perforated plate 31 and the heat storage medium 2 to enlarge further.

In 3 is one of 2 deviating geometry of the tube 1 specified at which the cold water inlet from the first pipe end 11 through the bottom of the isolation tank 4 is guided. This measure allows the pipe 1 with a surface extension 15 in the form of a coiled tube 16 (with correspondingly increased volume of water) within the heat storage medium 2 equip so that the desired enlarged surface to the storage medium 2 is present and at the same time for ventilation of the pipe ends 11 and 12 the pipe 1 completely (ie in this case without residual water) can be emptied.

The close coupling of enthalpies of heating elements 5 to the liquid heat storage medium 2 as well as to the useful water in the pipe 1 remain as in the previous variants obtained by the coiled tubing 16 in a perforated plate 31 is admitted.

Following the usual safety requirements in aviation, are in the liquid heat storage medium 2 in addition, a safety temperature switch S1, for example with a 70 ° C switching threshold, and a voltage-safe safety temperature switch S2, eg with a 85 ° C switching threshold, and a level sensor S3 for a sufficient level of the heat storage medium 2 accommodated.

If one of these safety switches S1, S2 or S3 responds, the power supply to the heating element 5 prevented. To the extraction unit 7 (eg on a sink) to avoid too high temperatures (above 48 ° C) is at the second end of the pipe 12 (Hot water outlet) again a safety temperature sensor S4 attached. While the safety switches S1 to S3 are preferably designed as a two-pole temperature switch and directly interrupt the heating circuit (or its control) and thus constitute a kind of emergency shutdown, the safety temperature sensor S4 on the microcontroller 61 be switched to start a control loop in the extraction unit 7 For example, a sensor-controlled mixer tap for increased cold water addition influences.

The one in the control unit 6 included microcontroller 61 can still be used as feedback on via the interface 63 the removal unit 7 received request signals and signals from the sensors 62 and / or S4 optionally also warm water outflow and / or removal time via the interface 63 regulate (limit) if the calculated enthalpy is insufficient for the requested amount of water.

The used microcontroller 61 Can take over the entire control of domestic hot water (eg for one or more sinks in an airplane) and make it more effective by connecting CAN ports to the extraction unit 7 (Mixer and / or faucet and possibly IR sensors as controls) with the microcontroller 61 get connected. The microcontroller 61 is then used as the master controller, so that the number of microcontrollers required to control the entire water heater can be reduced to one. This can be done by programming the microcontroller 61 with regard to the typical removal behavior of the operator in the context of physical possibilities differentiated to different customer requirements.

A modification of the as surface extension 15 provided coiled tubing 16 (of the water heater from 3 ) is in 4 shown. In this example, the surface extension is 15 in the form of a hose coil 17 designed in which the heating element 5 is integrated as resistance heating. The hose coil 17 at the same time provides direct thermal contact with the tube 1 passed through water and the heat storage medium 2 ago, leaving a separate metallic thermal bridge 3 does not need to be used or such in the form of the material of the hose coil 17 integrated exists.

All other elements and functions of the water heater after 4 are - as described in the previous figures - available in the same way.

In 5 is another variation of the water heater 3 indicated at which a surface extension 15 in the form of a watertight cylindrical pipe extension 18 with a defined volume of water in the liquid heat storage 2 is introduced. A in such a "cross-sectional dilated" tube 1 created supply of heated water can at loading or venting the pipe ends 11 and 12 in turn, completely automatically deflated to frost resistance.

The heating of the water supply (suitably not more than a three quarter of a liter) in the cylindrical tube extension 18 has a slightly different type of heat transfer than in the previous examples according to 3 and 4 , Flows as a result of water removal at the extraction unit 7 at the second end of the pipe 12 Hot water from, then flows in the same amount through the first pipe end 11 Cold water and mixes with the in the cylindrical extension 18 already heated water volume, so that there is a direct heat exchange, before by heat input on the as a thermal bridge 3 functioning perforated plate 31 an intensive reheating takes place.

For large quantities of retrieved hot water, the water heater is made even more effective by the Enthalpieübergang on the entire pipe 1 in the heat storage medium 2 in addition to the cylindrical tube extension 18 a pipe or hose coil 16 respectively. 17 (as in 3 or 4 described) is arranged upstream. For hot water extraction at the second pipe end 12 This will be the first pipe end 11 inflowing cold water already preheated, so that the mixing temperature in the cylindrical extension 17 can not sink too much.

Likewise, when combining cylindrical pipe extension 18 and downstream pipe spiral 16 (or hose coil 17 ) from the cylindrical tube extension 18 with (lowered) mixing temperature effluent hot water in the coiled tubing 16 be reheated to the desired discharge temperature. Here is too much follow-up heating due to the arrangement of the coiled tubing 16 in the heat storage medium 2 locked out.

These Design has particular advantages when hot water in large batches with longer breaks is queried.

All other details of the water heater are analogous to how 2 described, present or can be regulated or safety according to 3 be complementary.

Due to the bodies in 1 to 5 For example, multiple drains of warm service water, dosed in quick succession, or alternatively a slow and continuously flowing water volume, can be sufficiently heated over a longer period of time without the water temperature at the hot water outlet (second pipe end 12 ) decreases considerably. The energy required for this, which is not really sufficient by the heating element 5 can be made available, comes from the extracted enthalpy of the liquid heat storage medium 2 , despite the low heating power of the heating element 5 is maintained at a nearly constant temperature level.

1

pipe

11

first pipe end

12

second pipe end

13

pipe section

14

curved part

15

surface extension

16

coiled tubing

17

hose spiral

18

pipe extension

2

Heat storage medium

3

thermal bridge

31

perforated plate

32

recess

4

insulation container

5

heating element

6

control unit

61

microcontroller

62

temperature sensor

63

interface (to the withdrawal unit)

7

withdrawal unit

S1, ... S3

safety switch

S4

Safety temperature sensor

Claims (28)

Water heater for vehicles, in particular for aircraft, in which an electric heating element is arranged in a thermal insulation container and in the insulation container, a first pipe end for the cold water supply and a second pipe end for the hot water outlet are initiated, characterized in that - the insulation container ( 4 ) with a liquid heat storage medium ( 2 ), between the first pipe end ( 11 ) and the second pipe end ( 12 ) a waterproof pipe ( 1 ) to the flow of the water to be heated by the liquid heat storage medium ( 2 ), the pipe ( 1 ) a large relative surface within the heat storage medium ( 2 ) to achieve fast enthalpy transitions, and - the electric heating element ( 5 ) with both the water-carrying pipe ( 1 ) as well as with the heat storage medium ( 2 ) is in thermal contact with a control unit ( 6 ) for controlling the power of the heating element ( 5 ) in dependence on at least one temperature sensor ( 62 ), which determines the temperature of the heat storage medium ( 2 ) is present. Water heater according to claim 1, characterized in that the heat storage medium ( 2 ) is a synthetic oil. Water heater according to claim 2, characterized in that as a heat storage medium ( 2 ) a synthetic mineral oil is present. Water heater according to claim 2, characterized in that as a heat storage medium ( 2 ) Silicone oil is used. Water heater according to claim 1, characterized in that the pipe ( 1 ) consists of stainless steel. Water heater according to claim 1, characterized in that the pipe ( 1 ) in such a geometry through the insulation container ( 4 ) is guided, that the first pipe end ( 11 ) for the cold water supply below and the second pipe end ( 12 ) for the hot water outlet above each the isolation tank ( 4 ) crossing linear portion and curved portion ( 13 ; 14 ) of the pipe ( 1 ) are arranged so that when ventilation of the pipe ( 1 ) at the pipe ends ( 11 . 12 ) in the pipe ( 1 ) water can run independently. Water heater according to claim 6, characterized in that between at least one in the heat storage medium ( 2 ) linear section ( 13 ) of the pipe ( 1 ) and the heating element ( 5 ) a massive metallic thermal bridge ( 3 ) high thermal conductivity to increase the direct enthalpy transition from the heating element ( 5 ) on the in the pipe ( 1 ) located water is arranged. Water heater according to claim 7, characterized in that the thermal bridge ( 3 ) consists of a material with a thermal conductivity of at least 100 watts per meter and Kelvin. Water heater according to claim 8, characterized in that the thermal bridge ( 3 ) is made of copper or a copper alloy. Water heater according to claim 8, characterized in that the thermal bridge ( 3 ) is made of aluminum or an aluminum alloy. Water heater according to claim 7, characterized in that the thermal bridge ( 3 ) as a massive perforated plate ( 31 ) is formed, wherein the perforated plate ( 31 ) several recesses ( 32 ) for receiving the heating element ( 5 ) and at least one section ( 13 ) of the pipe ( 1 ) having. Water heater according to claim 11, characterized in that the perforated plate ( 31 ) is made of a densely pressed aluminum profile. Water heater according to claim 6, characterized in that the pipe ( 1 ) is formed as a multi-U-shaped pipe bend, wherein at least one vertical U-bend, consisting of two linear sections ( 13 ) and a curved part ( 14 ), in the heat storage medium ( 2 ) is immersed and another curved part ( 14 ) of the pipe ( 1 ) over the edge of the cup-shaped insulating container ( 4 ) and with the first pipe end ( 11 ) below the bottom of the insulated container ( 4 ) connected is. Water heater according to claim 6, characterized in that the pipe ( 1 ) with its first pipe end ( 11 ) a surface extension ( 15 ) for enlarging the enthalpy transition surface within the heat storage medium ( 2 ) having. Water heater according to claim 14, characterized in that the surface extension ( 15 ) as a coiled tubing ( 16 ) in the manner of a heat exchanger within the heat storage medium ( 2 ) is executed. Water heater according to claim 15, characterized in that along the coiled tubing ( 16 ) a resistance heating element ( 5 ), so that a direct thermal contact of the heating element ( 5 ) to the pipe ( 1 ) and to the heat storage medium ( 2 ) consists. Water heater according to claim 15, characterized in that the surface enlargement ( 15 ) as a hose coil ( 17 ) with an integrated resistance heating ( 5 ) is carried out so that a direct thermal contact of the heating element ( 5 ) to that in the pipe ( 1 ) and the heat storage medium ( 2 ) consists. Water heater according to claim 14, characterized in that the surface extension ( 15 ) as a section-wise pipe extension ( 18 ) for receiving a limited supply of water within the heat storage medium ( 2 ) is executed. Water heater according to claim 14 or 18, characterized in that the volume within the surface extension ( 15 ; 18 ) of the pipe ( 1 ) contains less than one liter of water. Water heater according to claim 14 or 18, characterized in that the volume within the surface extension ( 15 ; 18 ) of the pipe ( 1 ) contains less than 0.75 liters of water. Water heater according to claim 18, characterized in that the pipe extension ( 17 ) for enlarging the surface as an n-angular prism-shaped extension of the cross section of the tube ( 1 ) is executed. Water heater according to claim 18, characterized in that the surface extension ( 15 ) as a cylindrical pipe extension ( 18 ) of the cross section of the tube ( 1 ) is executed. Water heater according to claim 14, 15 or 22, characterized in that heating element ( 5 ) and surface extension ( 15 ; 16 ; 18 ) in a massive thermal bridge ( 3 ) are arranged to improve the enthalpy transition, wherein the thermal bridge ( 3 ) as a perforated plate ( 31 ) is formed and heating element ( 5 ) and surface extension ( 15 ; 16 ; 18 ) in different cylindrical recesses ( 32 ) of the perforated plate ( 31 ) are fitted. Water heater according to claim 14, characterized in that the surface extension ( 15 ) of the pipe ( 1 ) from a combination of within the heat storage medium ( 2 ) successively arranged coiled tubing ( 16 ; 17 ) and cylindrical tube extension ( 18 ) consists. Water heater according to claim 24, characterized in that the cylindrical pipe extension ( 18 ) together with the heating element ( 5 ) in a massive thermal bridge ( 3 ) is arranged, wherein heating element ( 5 ) and cylindrical tube extension ( 18 ) in different cylindrical recesses ( 32 ) one as a perforated plate ( 31 ) trained Thermal bridge ( 3 ) are arranged. Water heater according to claim 1, characterized in that the control unit ( 6 ) is connected to further temperature or safety switches (S1, S2, S3, S4), whereby a microcontroller ( 61 ) is present for optimum control and regulation of the discharged hot water. Water heater according to claim 26, characterized in that safety switches (S1; S2; S3) which are designed as limit value switches, in the control unit ( 6 ) directly with means for interrupting the power supply of the heating element ( 5 ) are connected. Water heater according to claim 26, characterized in that the control unit ( 6 ) with an extraction unit for hot water extraction ( 7 ) is connected and the microcontroller ( 61 ) via an interface ( 63 ) with the removal unit ( 7 ) is connected to take over the control and master function for all in the withdrawal unit ( 7 ) contained electronically controlled components.