DE102007028804A1 - Liquid level measuring system for measuring level of liquid of direct methanol fuel Cells systems, has container of prismatic form, which has inlet and outlet - Google Patents

Abstract

The liquid level measuring system has a container (210) of prismatic form. The container has an inlet (101) and an outlet (103). A unit is provided with measuring points for determining the liquid level (207). The measuring points are located on the axis that reaches the geometrical center of a lower surface (308a) of the container up to the geometrical center of a top surface (308) of the container.

Description

The Invention relates to liquid level measuring system, in particular to liquid level measuring system for Direct methanol fuel cell systems (DMFC).

Technical background of Invention and prior art

A Fuel cell is a galvanic cell, which is the chemical reaction energy a continuously supplied fuel and a Oxidizing agent converts into electrical energy. A fuel cell usually consists of two electrodes passing through a membrane or an electrolyte are separated from each other. The anode will with the fuel, for example hydrogen, methane or methanol, lapped and the fuel is oxidized there. The cathode is lapped with the oxidizing agent, for example oxygen, Hydrogen peroxide or potassium thiocyanate, which reduces at the electrode becomes. The ones used to realize the individual components Materials vary depending on the fuel cell type choose.

compact Direct methanol fuel cell systems (DMFC) are currently in focus the development in many electronics companies. It is expected, that they power the power of mobile electronic devices replace or change because they have longer service times and allow faster charging. Direct methanol fuel cells (DMFC) are low-temperature fuel cells, even at temperatures in the range of approx. 60-120 ° C work. As the electrolyte, this cell type uses a polymer membrane. Methanol (CH3OH) is combined with water without prior reforming supplied directly to the anode and oxidized there. At the anode arises as exhaust gas carbon dioxide (CO2). The cathode as the oxidant supplied oxygen reacts with H + ions and electrodes to water. The advantage of the DMFC is the use of a liquid, very easily storable and extremely cheap energy source, which can be disseminated for example in plastic cartridges. moreover There is a widely branched infrastructure for methanol already in many areas, for example by the use as antifreeze additive in windscreen wiper water for motor vehicles. This fuel cell type can - depending on the design - services in the field from a few mW to a few 100 KW. DMFCs are particularly suitable for portable use in electronic devices as a replacement and supplement to conventional accumulators. Typical applications are in telecommunications and the Power supply of notebooks.

The Oxidation of the methanol at the catalyst of the anode takes place stepwise, having multiple reaction pathways with different intermediates in the discussion stand. To uphold the efficiency of the fuel cell, It is necessary to rapidly remove the reaction products from the environment remove the electrode. Due to the prevailing temperatures and the underlying chemistry creates a liquid / gas mixture from CO2, water, water vapor and unreacted methanol. For this Liquid / gas mixture, the CO2 must be separated to after adjustment of the methanol concentration, the liquid Re-fuel mixture to the anode. The separation The gases are produced with the help of a CO2 separator.

At the cathode is formed from unused air, water and water Water vapor also a liquid / gas mixture. To one To achieve long autarky of the system, one must as possible much of the water is separated from the air and into the Anodenkreislauf be returned. To this The purpose is a heat exchanger behind the cathode outlet the fuel cell arranged to cool the mixture and to achieve a condensation of the water vapor.

the Downstream heat exchanger is arranged an air separator, which separates the air flow from the liquid water to the Return water back to the anode circuit. Accordingly, the separators are primarily used for water management and the removal of CO2 from the equilibrium. conventional Separators separate the phase mixture from liquid and gas or vapor components, whereby the gas or vaporous components to the environment be delivered.

The Separators or separators therefore serve the purpose Water management and the removal of CO2 from the equilibrium. They are mostly realized as separate institutions, the with the actual fuel cell each over one for the liquid / gas mixture common supply connected is. This spatial distance also requires a Temperature gradient and from the slowly cooling Liquid / gas mixture condenses water out. conventional Separators separate the phase mixture from liquid and gas or vapor components, wherein the Gas or vaporous components to the environment be delivered. The present invention also starts here.

It is known to provide a separator for separating the liquid / gas mixture with a porous membrane. The porous membrane faces the liquid / gas mixture with its inside and its outside is in contact with the environment. Furthermore, such membranes in the Re gel coated with hydrophobic materials or consist of these. From the inside of the membrane diffusion channels extend to the outside, which are dimensioned so that located on the inside (liquid) water does not penetrate, but gas can diffuse to the outside.

at the separators or separators of the prior art is the Liquid / gas mixture spent in a cavity at the the gas-permeable membrane is adjacent. One volume of the cavity and one relative position of the membrane depend on the orientation of the Separators in operation and the expected volumes of liquid / gas mixture. The volume of the cavity is set so that the liquid / gas mixture after entering the cavity into a gas and liquid phase can separate and then over the entire volume of the cavity are separated from each other. The membrane will be like this arranged to abut an upper side of the cavity, the is in regular operation with the gas phase in contact. At the Bottom, the liquid phase is discharged. A sufficient functionality of such separators however, only if the orientation of the separator in the Space is noticed. The separator may at most by a few degrees be pivoted from its upright position, thus the gas phase continues to rest against the membrane. Especially for the mobile Use of fuel cells, however, this circumstance is limiting.

Prior art devices combining the functions of a CO2 separator, a water separator and a mixer are all off EP 1 383 190 A1 and EP 1 383 191 A1 known. The inlet flow of water / air is located at the top of the device. The liquid water is separated by gravity and falls to the bottom of the device. The fuel inlet stream is located at the bottom of the device, which operates as a liquid retention tank. The gases of the incoming streams leave the device through a vent, which also consists of a liquid-tight, gas-permeable membrane. The liquid mixture leaves the device through the fuel outlet to be led back to the stack.

In EP 1 383 190 A1 and EP 1 383 191 A1 For example, the devices include a liquid level gauge necessary for the operation of the system. In these patent applications, the liquid level sensor position is not specified and appears to be on the side of the device.

Various principles for liquid level sensors exist based on an electrical capacitance measurement as in FIG US Pat. No. 6,943,566 or on a heat transfer using a combination of a thermocouple and a heating resistor, as in US 6,973,828 disclosed.

The Measurement of the level is for the function of a DMFC system critical: it must be ensured that alone Liquid is led to the stack and therefore must have a predetermined amount of liquid during of the operation.

however are appropriate devices and in particular liquid level measurements not independent of orientation and this can be a problem in portable Generate devices for which operation in inclined Position should be possible.

Summary of the invention

The Basic task of the invention is the disadvantages described above overcome in the prior art. In particular it is An object of the invention is a liquid level measuring system for fuel cell systems indicating the orientation independence of the system increases.

One Liquid level measuring system is according to claim 1 indicated. Further advantageous embodiments of the invention are the subject of the dependent claims which individually or in any combination can be implemented.

As a result, is a liquid level measuring system for measuring a Liquid level of a DMFC fuel cell system specified, wherein the liquid level measuring system a Container of prismatic shape, wherein the container has at least one inlet and at least one outlet, the liquid level measuring system being a means for determining the liquid level comprises, which at least one Having a measuring point for determining a liquid level, wherein the at least one measuring point is located on an axis is that of the geometric center of gravity of a bottom of the container to the geometric center of gravity of a top of the container enough.

advantageously, can by the specified arrangement of the at least one measuring point the System work independently of the orientation, since the Level detection or measurement independent of the orientation is. It ensures that only liquid led to the liquid outlet of the system.

Preferably, at least three measuring points are located along the axis, wherein a first measuring point is related to the maximum possible liquid level, a second measuring point is related to the desired liquid level, and a third Measuring point is related to the minimum allowed liquid level. However, a continuous liquid level sensor may also be located along the axis which has a continuum at measurement points along the axis.

The Means for determining the liquid level is preferred by a sensor with a tubular structure educated.

The container may be a CO2 separator of a direct methanol fuel cell system. The at least one inlet may include a water / air inlet and the at least one outlet comprises a gas outlet and a liquid outlet. The container may further be a water separator of a direct methanol fuel cell system, the container comprising a combination of a CO ₂ separator and a water separator of a direct methanol fuel cell system, the container having a first inlet for receiving an inlet stream from a heat exchanger, and a second inlet for Receiving an inlet stream from a fuel cell stack has.

Prefers the height of the container is larger as the width. This has the advantage that the angle of inclination the container in which the container is still working can, is increased.

Of the Container may have a passage hole in the top of the container for introducing the liquid level determining agent in the container.

In In a preferred embodiment, the fluid level measuring system comprises Furthermore, a voltage source and a measuring circuit for measurement a stream, wherein the means for determining a liquid level comprises: a first wire connected to the voltage source and arranged so that at least one point of contact with the interior of the Container on the surface of the means of determination a liquid level is formed, at least one second wire connected to the measuring circuit and arranged so that a contact point to the interior of the container on the surface the means for determining a liquid level formed is, at a corresponding point of the at least one contact point of the first wire so that the at least first contact point of the first wire and the contact point of the at least one second Wire a pair of liquid level measuring points forms within the container.

In In another embodiment, a first wire three contact points to the interior of the container at three different Heights of the means for determining a liquid level train and three second wires, each one corresponding to one Contact point to the inside of the container at three heights form at the means for determining a liquid level, the heights of the three contact points of the first wire correspond, so that formed three pairs of measuring points of a liquid level which are a first measuring point, the maximum fluid level corresponds, and a second measuring point, the minimum liquid level corresponds, and a third measuring point, which is a liquid level appropriate for the work of the system, include.

According to the Invention are the pairs of contact points along a section the symmetry planes of the container placed so that increased orientation independence is ensured.

The Wires can be wires made of precious metal.

The Voltage of the voltage source can be 5 V or between 1 V vary to 15V.

Of the Container may have two planes of symmetry through the corresponding symmetry axes of the base of the Container, with the means of determination a liquid level along a line is, which forms the intersection line of the symmetry planes.

Of the Container may have a height exceeding twice the size of the width of the container is.

The Measurement can be based on the difference between the conductivity by a gas or a liquid. An output signal of the system generated by a measurement point can be higher if the measuring point is immersed in a liquid, which is contained in the container as if the measuring point immersed in a gas contained in the container is.

Of the Geometric center of gravity is through the intersection of the symmetry axes the bottom or the surface defined. In a other definition is the geometric center of gravity of the bottom or the top defined as a point in which any two Lines showing the corresponding surface in two planes Divide and cut A and B of equal size.

If the mass on the top and / or bottom equally distributed is, the geometric center of gravity of the surfaces is the same the center of gravity of the corresponding area.

Brief description of the drawings

The Invention will be described below with reference to the embodiments the invention and the corresponding drawings in more detail to be discribed.

1 shows a DMFC system of the prior art;

2 shows an embodiment of the mixer with integrated gas separation device of the prior art;

3 shows a container with a liquid level measuring system according to the invention;

4 shows a position of the liquid level sensor or detector points according to the invention in an embodiment of the invention;

5 shows a position of the liquid level sensor or detector points according to the invention in another embodiment of the invention;

6 demonstrates the improved orientation independence of liquid level measurement according to the invention;

7 shows a definition of a minimum height for the work of the system according to the invention;

8th shows an alternative embodiment of the invention with a liquid outlet formed at the bottom of the container containing the liquid level sensing system;

9 shows an alternative embodiment of the liquid level measuring system.

Detailed description the invention

The Liquid level measurement is for devices with an open surface of the liquid (a Container filled with a liquid or a gas) not independent of the orientation, if the shape of the container does not meet some geometric conditions corresponds and if the liquid level sensor position not chosen wisely. For the function of the system is a measurement of the liquid level Some discrete points are necessary, but not necessarily a continuous measurement.

in the The term liquid level sensor is referred to below Definition of a sensor that uses a continuous value returns a liquid level (such as Example capacitive sensors). The term liquid level detector is used for a device that gives information whether a liquid is present or not.

1 serves to illustrate a conventional DMFC system. A DMFC system is as in 1 shown constructed. A fuel cell stack 10 has an air inlet 11 and an air outlet 13 on. An air pump or a fan 12 supplies the stacked cathode through the air inlet 11 with reaction air. A heat exchanger 50 is arranged in the outlet stream of the fuel cell cathode. A fan 55 is used to cool the heat exchanger, resulting in cooling of the outlet stream and condensation of water. This two-phase flow exits the heat exchanger at the outlet 52 , Downstream of the heat exchanger is a water separator 60 arranged, the liquid water separated from the air stream. The separated water is introduced into the anode circuit of the fuel cell system through an optional condensation pump 70 returned, the remaining air is through a vent outlet 61 discharged to the environment.

An indispensable function of the system is the separation or separation of CO ₂ from the outlet stream coming from the stack anode outlet 16 comes out. This outlet stream consists of a mixture of methanol, water and CO ₂ , the depleted fuel mixture. For proper operation of the fuel cells, CO ₂ must be separated or separated from the fuel mixture stream prior to recirculation of the stream into the stack.

An anode circuit for a fuel mixture consists of a CO2 separator / mixer device downstream of the stack fuel outlet 16 is arranged and removes CO ₂ from the reaction stream. The CO ₂ fuel mixture enters the CO ₂ separator / mixer device through a CO ₂ fuel mixture inlet 120 one. Inside the device, CO _{2 is} separated and to the environment through a vent 21 issued. In addition, the CO ₂ separator / mixer device receives condensed water from the water separator 60 / the condensation pump 70 through the condensed water inlet 121 , The CO ₂ separator / mixer also receives concentrated fuel from the fuel tank 30 over the fuel pump 31 through the inlet for concentrated fuel 122 , These liquids are mixed into the depleted fuel mixture to provide a regenerated fuel mixture. A fuel pump 23 removes the regenerated fuel mixture from the CO ₂ separator / mixer device through the fuel mixture outlet 123 and leads him to the anode inlet 15 back of the stack.

2 shows an embodiment of the mixer with integrated gas separation device of the prior art. The inlet flow of water / air 101 is located in the upper part of the device. The liquid water is by gravity 106 separates and falls towards the bottom of the device. The fuel inlet stream is at the bottom of the device 102 provided, which works like a liquid storage tank. The gases from the incoming stream leave the device through a vent 104 , which consists of a liquid-tight, gas-permeable membrane. The liquid mixture exits the device through the fuel outlet 103 to be returned to the stack.

3 shows a container with a liquid level measuring system according to the invention. The device allows for liquid level detection or measurement that is independent of orientation. The device consists of a housing which contains the liquid container 210 formed. The device plays the role of the CO ₂ separator here 20 and the water separator 60 a DMFC system. Therefore, one meets inlet streams from the stack 102 and from the heat exchanger 101 as well as outlets for liquid 103 and for gases 104 at.

A level measuring system is in the container 210 contain and includes a means for detecting a liquid level 207 , which is formed by a sensor tube, which in the container 210 through the top of the container 210 penetrates. The liquid level detection device shown is simply based on the different electrical conductivity between the gas phase and the liquid phase. The circuit includes a voltage source 200 , Wires 201 , which are preferably noble metal wires, the contacts with the environment 202 form a trigger circuit 205 which amplifies a current, and a binary switching signal output 206 , The wires comprise a first wire 201 connected to the voltage source 200 and at least one point of contact 202a to the interior of the container 210 training, and at least a second wire 201b , which is another contact point 202b to the interior of the container 210 forms at a corresponding location on the means for determining the liquid level. This appropriate location may be due to a preferred orientation of the container 210 be defined as here in 3 shown. The means for determining the liquid level 207 extends in the preferred orientation along the vertical axis of the container 210 and the pair of contact points 202a . 202b is in different horizontal positions on the surface of the determining means 207 arranged but at the same vertical position on the surface of the means for determining a liquid level 207 , The contact points are preferred 202a . 202b on opposite sides of the liquid level determining means 207 , here the sensor tube, arranged.

Preferably, a conductive measuring principle is used. The first wire 201 is with the voltage source 200 connected, the current is through a first wire 201 to the at least one contact point 202a inside the container 210 guided and then through the medium inside the container 210 to the corresponding contact point 202b the at least one second wire 201b and then on to the drive or measurement circuit 205b , If the environment of the contact points 202a . 202b surrounded by gas, ie the liquid level 204 is below the contact points 202a . 202b , then the conductivity is insufficient and the output signal from the second wire 201b is low. If the environment of the contact points 202a . 202b surrounded by a liquid, ie the liquid level 203 is above the contact points 202a . 202b , a current can flow through the circuit passing through the voltage source 200 , the wires 201 and the liquid and the drive circuit 205 is formed, and the output signal is high.

The voltage source is typically 5V but may be between 1V and 15V. The output signal, when surrounded by liquid, is of the same order of magnitude (about 5 V). The output signal may also be designed to be inverse to the above description, depending on the requirements of the control circuit that analyzes the signal. This signal inversion can be achieved by an inverter stage within the drive circuit 205 be achieved.

The surface of the sensor tube 207 holding the sensor wires 201 may be treated so as to avoid the presence of a liquid film contacting the two contact points, ie the surface may be hydrophobic.

4 shows an arrangement of the liquid level sensor or liquid level detector points according to the invention in an embodiment of the invention and 5 shows an arrangement of the liquid level sensor or liquid level detector points according to the invention in another embodiment of the invention.

An orientation-independent measurement can be realized by the measuring device (sensor or detector) on a line perpendicular to the geometric center of gravity of the base 308 the container is arranged as in 4 and 5 shown. It should be noted that the geometric center of gravity is not necessarily the real focus is when the material thickness is not constant over the entire base. The geometric center of gravity is here by the intersection of the symmetry axes of the base 308 or 308A defined the container. That is, the geometric center of gravity is equal to the real center of gravity assuming that the base 307 is formed of a single homogeneous material. In the case that the base of the container has two axes of symmetry 305 and 306 must, the liquid measurement along the line 301 be arranged, which lies at the intersection of the planes of symmetry or along the line passing through the center of gravity of the base 307 leads. The case of a non-symmetric base is in 5 shown.

In the case where only one liquid detection is installed, preferably three different levels would be used: a level indicating maximum liquid level 302 , a level to indicate a minimum level 304 and a level at the level necessary for the operation of the system 303 suitable is.

In 4 is the determination of the axis 310 for a prismatic container having a square or rectangular base and tops. In general, a prismatic container means that the side walls of the container are arranged at a right angle to the base of the container, and further that the angle between the side walls and the top is also a right angle. The bottom and the top are parallel to each other.

The axis 310 is the connection of the geometrical emphases 307 . 307a the top 308 or the bottom 308a , The focus 307 the top is determined by the intersection of the main axes of symmetry 305 and 306 the top. The same applies to the center of gravity 307a the bottom. To the same level measurement at different angles of inclination of the container 210 ensure are the measurement points 302 . 303 . 304 along the axis 310 arranged.

In the exemplary embodiment shown, the measuring point corresponds 304 the minimum level in the tank. When the minimum measurement point 304 If there is no signal, the system is turned off to prevent damage to the fuel cell stack.

The intermediate measuring point 303 corresponds to a nominal level. If the measuring point 303 If there is no signal, ie the level is lower, the system should be adjusted to fill the level, eg. B. by increasing the water condensation in the heat exchanger 50 , If 303 outputs a signal, the level should be reduced by the system control. When the maximum level measurement point 302 If a signal is emitted, ie if the level is higher, the system should be switched off to avoid overflowing the container or any other part of the system.

In the same way, a higher number of level measuring points along the axis 310 be arranged to achieve a more accurate level control.

In the limiting case, a continuous level sensor along the axis 310 be arranged to output a continuous level signal. The sensor may be a linearly extending capacitor that measures a change in capacitance when part of it is in contact with the liquid.

The Liquid level measuring system is particularly advantageous if more than one pair of measurement points is used, then all the different measuring points independently of the level can measure from the angle of inclination.

5 shows the determination of the axis 310 if the container is still of prismatic shape but any top 308a . 308 having. In this case, it is not possible to draw symmetry lines. The geometric center of gravity of the bottom 308a or the top 308 is considered the point 307 defined, in which any two lines 309 which divided the corresponding area into two areas A and B of equal size intersect. In other words, you draw a first line, which is the top 308 or the bottom 308a divided into two areas A and B of equal size. Then you draw a second line, which in turn subdivides the corresponding area into two areas A and B of equal size. The intersection of these two lines 309 is the geometric center of gravity. This can be done for any pair of arbitrary lines which divide the corresponding area into two areas A and B of equal size. This definition also applies to the example of a symmetrical top or bottom 308a . 308 ,

The orientation independence of the level measurement for a sensor arranged along the vertical of the center of gravity is in 6 illustrated. The level measurement 400 retains its validity for an inclined position - in this case, the liquid surface is numbered 401 represents - and for a vertical position - the liquid surface would in this case by the number 402 be represented. In any other position, the location of the liquid surface is constant on the axis of symmetry.

7 shows how the shape of the container the maximum operating angle influenced. The maximum operating angle 502 is here between the liquid surface in a vertical position 500 and a tilted position 501 shown. The minimum operating fluid volume is given by a given level 504 Are defined. To ensure that only liquid is fed to the stack, the liquid surface on the side of the container must remain above the feed tube and consequently larger than the height 506 be.

The maximum angle of inclination at which the system is still operational, ie still only liquid to the outlet 103 can be determined as follows, depending on the size of the side of the device: Alpha = arctan [2 * (Hmin - SideMinHeight) / Main_side] where SideMinHeight the reference 506 corresponds, Hmin is 504 , Main_side is 503 and the angle alpha 502 is. The size SideMinHeight preferably includes an additional offset from the top of the outlet 103 To provide a tolerance, but can also equal the size of the bottom of the device to the top of the outlet 103 be.

The possible angle alpha 502 is larger if the base dimension is narrower. The aspect ratio of the device, defined by the total height 507 and the length of the main page 503 must therefore be big enough. For a maximum operating angle of 45 ° an aspect ratio of 2 is required.

In an alternative embodiment, as in 8th shown is the liquid outlet 103 in the bottom of the container 210 arranged. Then the minimum height is zero and the possible angle of inclination 512 is enlarged.

9 shows an alternative embodiment of the level measuring system. Here are three level sensor measurement points 302 . 303 . 304 provided, one corresponding to the minimum level 304 , one corresponding to a middle level 303 and one corresponding to a maximum level 302 , A first wire 201 is with the voltage source 200 connected and arranged so that it to the surface of the means for determining a level 207 is guided at three different vertical positions, thereby three different contact points to the interior of the container 210 ausbildend. Three second wires 201b . 201c . 201d are provided, each corresponding to a current amplifier with a drive circuit 205b . 205c . 205d each having a level signal output 206b . 206c . 206d provides. Every second wire 201b . 201c . 201d becomes the surface of the agent for determining a level 207 guided, in a place that corresponds to the location of a contact point, by the first wire 201 is formed, creating contact points 202b . 202c . 202d to the interior of the container 210 be formed. The corresponding location here is a location on the opposite side of the means for determining a level at the same vertical position on the means for determining a level 207 , The measuring principle is the same as it is in the context of 3 has been described.

The person skilled in the art will find that, for a proper work of the detector, the sensor tube 207 in 3 and 9 must have a sufficiently small diameter to ensure that only corresponding pairs of contact points will reach the level at an inclined position of the container 210 measure up. At a maximum angle of inclination of the container 210 the sensor should still fill level by means of the corresponding pair of contact points z. B. over 202aa of the wire 201 and 202d of the wire 201c and not z. B. via the contact points 202C of the wire 201c measure up. As a result, the diameter of the tube must be sufficiently small to ensure that either the corresponding points of contact are either submerged in the liquid or both are free of liquid. This can also be ensured by arranging the different pairs of contact points with a sufficient distance as a function of the maximum operating angle.

The Sensor housing is preferably molded from plastic. It can from a hydrophobic material, such as. As PTFE or PVDF shaped be an adhesion at a low level, which may be a source of a wrong signal, too avoid.

The invention brings the following advantages into a DMFC system. On the one hand, the level measurement is independent of the orientation of the device within an angle of ± 45 ° or more, in both directions, depending on the ratio of the height to the width of the container 210 , This enables the possibility of reliable operation of the system in an inclined position. Further, a system constructed with a level measurement in accordance with the present invention is simpler than a prior art level measurement system, thereby reducing the cost of the system.

10

fuel cell stack

11

inlet port

12

pump

13

outlet

15

inlet port

16

outlet

20

CO ₂ separator

22

mixer

23

pump

30

fuel tank

31

Valve

50

heat exchangers

52

outlet

55

Fan

60

air separator

61

outlet valve

62

management

70

pump

101

Water / air inlet stream (from the heat exchanger)

102

Fuel inlet stream

103

flow of fuel

104

Outlet opening for gases (CO ₂ and air)

105

Fuel mixture stand

106

Water, falling by gravity

107

Liquid level sensor

200

voltage source for the operation of the liquid level detector

201a, b, c, d

Built (Precious) metal wires

202a, b, c, d

Contact points the wires

203

liquid Level above the detector

204

liquid Level below the detector

205b c, d

current amplifier with drive circuit

206a

Level detector output signal, earth

206b, c, d

Level detector output signal, signal for contact points 202b , c, d

207

Liquid level detector / means for Measuring a liquid level

208

trapped Insulating material for detector wires

209

passage for detector tube

210

container

301

carrier for liquid level sensors / detectors

302

Liquid level measuring point for the maximum level

303

Liquid level measuring point for the operating level

304

Liquid level measuring point for the minimum level

305

First Symmetry axis of the top

305a

First Symmetry axis of the underside

306

Second Symmetry axis of the top

306a

Second Symmetry axis of the underside

307

main emphasis the top

307a

main emphasis the bottom

308

top

308a

bottom

309

Any line on the top 308 that the top 308 divides into two areas of equal size

309a

Any line on the bottom 308a that the bottom 308a divides into two areas of equal size

310

Axis, which are the focal points 307 and 307a combines

400

Liquid level target

401

liquid surface in employed position

402

liquid surface in vertical position

500

liquid surface in vertical position

501

liquid surface with angle

502

angle alpha

503

width the container base

504

liquid height

505

modification the fluid level on the side

506

minimal Height of liquid on the side

507

total height of the container

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1383190 A1 [0010, 0011]
• - EP 1383191 A1 [0010, 0011]
• US 6943566 [0012]
• - US 6973828 [0012]

Claims (23)

Liquid level measuring system for measuring a liquid level of a DMFC fuel cell system, wherein the fluid level measuring system comprises a container ( 210 ) of prismatic shape, the container ( 210 ) at least one inlet ( 101 ) and at least one outlet ( 103 ), wherein the liquid level measuring system comprises a means for determining the liquid level ( 207 ) comprising at least one measuring point ( 302 . 303 . 304 ) for determining a liquid level, characterized in that the at least one measuring point ( 302 . 303 . 304 ) on one axis ( 310 ), which depends on the geometric center of gravity of an underside ( 308a ) of the container ( 210 ) up to the geometric center of gravity of an upper side ( 308 ) of the container ( 210 ) enough. Liquid level measuring system according to claim 1, wherein at least three measuring points ( 302 . 303 . 304 ) along the axis ( 310 ), a first measuring point ( 302 ) in relation to the maximum possible liquid level, a second measuring point ( 303 ) in relation to the desired liquid level, and a third measuring point ( 304 ) is related to the minimum allowed fluid level. A liquid level measuring system according to claim 1, wherein a continuous liquid level sensor along the axis ( 310 ) which is a continuum at measuring points along the axis ( 310 ) having. Liquid level measuring system according to claim 1, wherein the means for determining the liquid level ( 207 ) is formed by a sensor having a tubular structure. Liquid level measuring system according to claim 1, wherein the container ( 210 ) is a CO ₂ separator of a direct methanol fuel cell system. A liquid level measuring system according to claim 1, wherein the at least one inlet ( 101 ) a water / air inlet and the at least one outlet ( 103 ) a gas outlet ( 104 ) and a liquid outlet ( 103 ). Liquid level measuring system according to claim 1, wherein the container ( 210 ) a water separator ( 60 ) of a direct methanol fuel cell system. Liquid level measuring system according to claim 1, wherein the container ( 210 ) a combination of a CO ₂ separator and a water separator ( 60 ) of a direct methanol fuel cell system, wherein the container ( 210 ) a first inlet ( 101 ) for receiving an inlet stream from a heat exchanger ( 50 ), and a second inlet ( 102 ) for receiving an inlet stream from a fuel cell stack ( 10 ) having. Liquid level measuring system according to one of the preceding claims, wherein the height of the container ( 210 ) is greater than the width. Liquid level measuring system according to claim 1, wherein the container ( 210 ) a passage hole ( 209 ) in the top of the container ( 210 ) for the introduction of the liquid level determining agent ( 207 ) in the container ( 210 ) having. Liquid level measuring system according to one of the preceding claims, wherein the system further comprises a voltage source ( 200 ) and a measuring circuit ( 205 ) for measuring a flow, wherein the means for determining a liquid level ( 207 ) comprises: - a first wire ( 201 ) connected to the voltage source ( 200 ) and arranged so that at least one contact point ( 202a ) to the interior of the container ( 210 ) on the surface of the liquid level determining agent ( 207 ), - at least one second wire ( 201b ) connected to the measuring circuit ( 205b ) and arranged so that a contact point ( 202b ) to the interior of the container ( 210 ) on the surface of the liquid level determining agent ( 207 ) is formed at a corresponding point of the at least one contact point ( 202a ) of the first wire ( 201 ), so that the at least first contact point ( 202a ) of the first wire ( 201 ) and the contact point ( 202b ) of the at least one second wire ( 201b ) a pair of measuring points ( 304 ) for the liquid level inside the container ( 210 ) trains. Liquid level measuring system according to claim 11, wherein a first wire ( 201 ) is designed so that it has three contact points ( 202a ) to the interior of the container ( 210 ) at three different heights of the liquid level determining means ( 207 ) and three second wires ( 201b . 201c . 201d ), each corresponding to a contact point ( 202b . 202c . 202d ) to the interior of the container at three levels on the means for determining a liquid level ( 207 ) forming the heights of the three contact points ( 202a ) of the first wire ( 201 ), so that three pairs of measuring points of a liquid level are formed which correspond to a first measuring point ( 302 ), which corresponds to a maximum liquid level, and a second measuring point ( 304 ), which corresponds to a minimum liquid level, and a third measuring point ( 303 ), which corresponds to a liquid level suitable for the work of the system. A liquid level measuring system according to claims 11 or 12, wherein the pairs of contact points ( 202 ) along a section of the symmetry planes of the container ( 210 ) are placed. Liquid level measuring system according to at least one of claims 11 to 13, wherein the wires ( 201 ) Are wires of precious metal. Liquid level measuring system according to at least one of claims 11 to 14, wherein the voltage of the voltage source ( 200 ) Is 5V. Liquid level measuring system according to at least one of claims 11 to 14, wherein the voltage of the voltage source ( 200 ) varies between 1V to 15V. Liquid level measuring system according to at least one of the preceding claims, wherein the container ( 210 ) has two planes of symmetry passing through the respective symmetry axes ( 305 . 306 ) of the base of the container ( 210 ), the means for determining a liquid level ( 207 ) along a line ( 301 ) is arranged, which forms the intersection of the planes of symmetry. Liquid level measuring system according to at least one of the preceding claims, wherein the container ( 210 ) has a height which is more than twice the size of the width of the container ( 210 ) corresponds. Liquid level measuring system according to at least one of the preceding claims, wherein the measurement the difference between the conductivity of a gas or a liquid based. Liquid level measuring system according to at least one of the preceding claims, wherein an output signal ( 206 ) of the system passing through a measuring point ( 304 ) is higher, when the measuring point is immersed in a liquid which is in the container ( 210 ) is immersed as if the measuring point is immersed in a gas which is in the container ( 210 ) is included. Liquid level measuring system according to at least one of the preceding claims, wherein the geometric center of gravity through the intersection of the symmetry axes of the underside ( 308a ) or the surface ( 308 ) is defined. Liquid level measuring system according to at least one of the preceding claims, wherein the geometric center of gravity of the underside ( 308a ) or the top side ( 308 ) as a point ( 307A ) respectively. ( 307 ), in which any two lines ( 309 ), which divide the surface into two surfaces A and B of equal size. Liquid level measuring system according to at least one of the preceding claims, wherein the geometric center of gravity of the surfaces ( 308 ) respectively. ( 308a ) is equal to the center of gravity of the corresponding surface.