DE102016120202A1 - Water separator for a fuel cell system, method for measuring a level in such - Google Patents

Abstract

The invention relates to a water separator (41) for a fuel cell system and a method for level measurement in such a. It is provided that the water separator (41) for level measurement has a hot wire (50) inside its housing (45).

Description

The invention relates to a water separator for a fuel cell system, and a method for measuring a level in such.

Fuel cells use the chemical transformation of a fuel with oxygen to water to generate electrical energy. For this purpose, fuel cells contain as a core component the so-called membrane electrode assembly (MEA for membrane electrode assembly), which is a microstructure of an ion-conducting (usually proton-conducting) membrane and in each case on both sides of the membrane arranged catalytic electrode (anode and cathode). The latter mostly comprise supported noble metals, in particular platinum. In addition, gas diffusion layers (GDL) can be arranged on both sides of the membrane-electrode arrangement on the sides of the electrodes facing away from the membrane.

As a rule, the fuel cell is formed by a multiplicity of stacked MEAs whose electrical powers add up. As a rule, bipolar plates (also called flow field plates or separator plates) are arranged between the individual membrane electrode assemblies, which ensure that the individual cells are supplied with the operating media, ie the reactants, and are usually also used for cooling. In addition, the bipolar plates provide an electrically conductive contact to the membrane-electrode assemblies.

During operation of the fuel cell, the fuel (anode operating medium), in particular hydrogen or a hydrogen-containing gas mixture, is supplied to the anode via a flow field of the bipolar plate and electrochemically oxidized to protons with release of electrons (H ₂ → 2 H ⁺ + 2 e ^- ). About the electrolyte or the membrane, which gas-tight and electrically isolated from each other, the reaction chambers, a transport of protons from the anode compartment into the cathode compartment. The electrons provided at the anode are supplied to the cathode via an electrical line.

The cathode is supplied during operation of the fuel cell, oxygen or an oxygen-containing gas mixture (for example air) as a cathode operating medium, so that a reduction of O ₂ to O ^2- with absorption of the electrons takes place (½ O ₂ + 2 e ^- → O ^2-). At the same time, the oxygen anions in the cathode compartment react with the protons transported via the membrane to form water (O ^2- + 2 H ⁺ → H ₂ O).

In order to supply a fuel cell stack with the operating media, this has an anode supply and a cathode supply. The anode supply includes an anode supply path for supplying the anode operating medium into the anode chambers of the fuel cell and an anode exhaust gas path for discharging an anode exhaust gas out of the anode chambers. In addition, a recirculation line is arranged in the anode supply in order to feed unused and discharged from the fuel cell stack hydrogen in the stack again. The cathode supply includes a cathode supply path for supplying the cathode operating medium into the cathode chambers of the fuel cell and a cathode exhaust path for discharging a cathode exhaust gas out of the cathode compartments.

During operation of the fuel cell system, product water and nitrogen reach the anode sides of the fuel cells and eventually accumulate in the anode supply, particularly in the anode exhaust path. The product water may cause damage to a conveyor arranged in the recirculation line and block flow paths. Therefore, a water separator is usually disposed downstream of the stack and upstream of the recirculation conveyor in the anode exhaust path. The separated in the water from the gaseous anode exhaust gas liquid water is discharged through an exhaust system. As the nitrogen content of the recirculated anode operating medium increases, the amount of hydrogen available for the fuel cell reactions decreases. The recirculated anode operating medium is therefore usually blown out of the anode supply or "purged" at regular intervals.

In other words, a water separator is needed in a fuel cell system in the anode circuit. In this separator, liquid water that has been separated from the fuel cell stack outlet is temporarily stored in a reservoir. The separated water can be drained from the separator via a separator valve. It must be ensured that a water seal is always present above the valve to prevent the escape of hydrogen. For this reason, a level sensor is used to determine when a critical level of water is reached and the valve can be opened. By means of this level sensor, the valve is then activated.

In current systems, a capacitive level sensor is used which detects a water level at a certain level, so-called dis- or non-continuous measurement. This sensor has the disadvantage that it often has false alarms, which have their cause in condensate, which is in the form of drops on the inner wall of the Precipitator from or in the gas flow precipitates. Alternatively, a float switch is used. However, these level sensors are very frost-resistant, since the float switch can freeze. Float switches are also not suitable for continuous level measurements.

The level sensors used in conventional internal combustion engines in the coolant tank are unsuitable for fuel cell systems, since they exploit the electrical conductivity of the liquid. However, these are unsuitable in fuel cell systems, since distilled water is collected in the water and in the coolant circuit of a fuel cell system, which is not electrically conductive.

The object of the invention is therefore to provide a level sensor that reliably measures the level in a water separator. In particular, a water separator is to be provided with level sensor, which allows a continuous level measurement.

This object is achieved by a water separator having the features of the first independent claim. Thus, a first aspect of the invention relates to a water separator for a fuel cell system comprising a housing having a wall, a bottom portion and a lid portion, and an anode operating gas supply line, an anode operating gas discharge line, and a sewage drain located in the bottom portion of the housing. According to the invention, a hot wire for level measurement is arranged in an interior of the housing. The advantage of the inventive design of a water separator is in particular that false triggering by condensate are significantly reduced and also a continuous measurement is possible. Furthermore, the water separator according to the invention can not be deactivated by icing, as it would be deiced in the case of icing in a deactivated mode by commissioning the hot wire. The hot wire for level measurement arranged according to the invention in the water separator is used analogously to a hot wire for speed measurement (hot wire geometry). In other words, the hot wire is integrated into the water separator. The hot wire is preferably in direct contact with the medium within the water separator. The medium is depending on the level of gas, in particular hydrogen gas, and or water. In operation, the hot wire is energized, so acted upon by an external electrical connection with power. Depending on the method of measurement, a continuous temperature is set, for example, whose height is dependent on the resistance of the hot wire and the supplied current. For this purpose, a certain power must be supplied to the wire, since heat is released to the medium in the separator. The emitted heat flow is highly dependent on which medium is in contact with the hot wire. The heat loss from the hot wire to the medium is significantly higher with liquid water than with gas. Thus, the power needed to hold the temperature can be used to determine which medium is in contact with the hot wire or what the ratio of gas to water is on the surface of the hot wire.

In a preferred embodiment, the hot wire extends along an inner side of the wall of the housing. This has the advantage that the hot wire is in direct contact with the medium. This allows a reliable result, which is not influenced by the resistance or the heat conduction of another material, which is arranged between hot wire and medium.

With particular advantage, the hot wire is arranged in the housing such that a continuous level measurement takes place. The particular advantage is that the deposited in the separator amount of water can be accounted for. Such data can then be used in models for describing the fuel cell stack.

A continuous level measurement is made possible in particular when the hot wire extends between the bottom area and the lid area. This allows continuous measurement because the hot wire is in contact with the separated water over a wide fill level range. In this case, the ratio between a proportion of the surface of the hot wire, which is in contact with water or with gas changes. Accordingly, as the level increases, a larger surface area of the hot wire is cooled with water and as a result, a higher power supply to the hot wire is required to ensure a constant hot wire temperature. For this purpose, a part of the hot wire is preferably in contact with the bottom area, since thus a minimum fill level is already detected.

In a further preferred embodiment of the invention, it is provided that the hot wire is arranged in the housing such that reaching of a predefined filling level is detected by means of the hot wire. In other words, a discontinuous level measurement takes place, which indicates in contrast to the continuous level measurement when a certain level is reached, but does not allow statements about intermediate levels. The advantage of this design is, in particular, a simplified measurement setup. The control of the hot wire, as well as the evaluation of the delivered measurement results are much less demanding compared to the continuous measurement.

Advantageously, the discontinuous level measurement takes place in which the hot wire is arranged at a defined distance parallel to the bottom region, which corresponds to the defined fill level, wherein the hot wire extends substantially transversely to the height of the housing. Such an arrangement has the advantageous consequence that upon reaching the defined level 54 abruptly the entire surface of the hot wire is in contact with water and thus the entire hot wire is cooled by the medium of water. This in turn results in a sudden and thus stepwise change, especially increase, in the power that must be supplied to the hot wire to maintain a constant temperature. Thus, the measurement of the level in this embodiment of the invention is particularly reliable and less error prone.

In a further preferred embodiment of the invention, it is provided that the hot wire is integrated in an insert element and the insert element is arranged variably or fixed in the housing. This has the advantage that the hot wire is not permanently installed in the housing and in particular can be retrofitted. In addition, the hot wire in this embodiment is easier to maintain and the defined level can be varied for example via a mounting height of the insert element 53 in the housing. The insert element is preferably a thin as possible rod-shaped element, which is made for example of a ceramic. The hot wire is advantageously outside, in particular arranged circumferentially around the element. The supply lines of the hot wire are preferably guided in the interior of the element and emerge in a region of the element, which is in the mounted state outside the housing of the water separator.

With particular advantage, the hot wire is guided over several turns or loops or spirally along a circumference. This leads to a significantly increased surface area of the hot wire with as little space as possible and thus to more reliable measurement results and less susceptibility to droplet formation. As a circle circumference, for example, the outer wall of a cylindrical insert element or the inner wall of a circumferential wall of the housing can be understood.

Another aspect of the invention relates to a method for determining a level of water in a water separator according to the invention of a fuel cell system. It is provided that depending on an electrically determinable cooling effect of water on the hot wire, a level of the water is determined. This has the advantage that the water does not freeze and in particular is not dependent on electrically conductive properties of the surrounding medium.

With particular advantage, it is provided that the hot wire is determined continuously and consistently and a decrease in a measured voltage of the hot wire is proportional to a level of the water in the water. Alternatively, instead of a continuous and constant energization of the hot wire, current is applied at intervals. With this measuring method both a continuous and a discontinuous level measurement is possible, in a continuous level measurement, a continuous measurement signal is output and evaluated and in a discontinuous measurement, a signal is issued only when a critical voltage is reached.

For the mentioned continuous electrothermal level measurement is based on a measuring arrangement, in which a hot wire is arranged perpendicular or at a certain angle within the water separator. The length of the hot wire is chosen so that both at maximum and at minimum level of the measuring range of the wire is not exceeded or fallen below. The resistance of the hot wire is proportional to the temperature of the wire, thus has PTC characteristic. The hot wire is heated for level measurement with a time-limited current pulse with a constant current. The falling at the beginning of the current pulse and at the end of the current pulse on the hot wire voltages are measured and used for level measurement. At a high level, the electric heating power supplied to the wire is largely released to the surrounding water. The wire heats up accordingly only insignificantly, so that only a small increase in resistance is measurable. At low level, however, the wire is mostly in the gas, which is a poorer heat conductor. Thus, only a little electric heating power is delivered and the heating wire cooled to a lesser extent. Thus, the wire heats up comparatively strong. The greater warming in turn results in a larger voltage difference. The voltage difference is therefore inversely proportional to the level height. In an alternative measuring method, a measuring current is presented to the measuring voltage and measured after heating of the heating wire caused by a heating current for calculating an electrical resistance of the heating wire. In this embodiment, a distinction is made between a heating current and a sensor or measuring current. In particular, the Heating current an unregulated, comparatively high current, while the measuring current is a regulated and very low current, which serves only a resistance measurement outside a heating of the hot-wire it.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

• 1 eine schematische Darstellung eines Brennstoffzellensystems gemäß dem Stand der Technik;
• 2 eine schematische Schnittzeichnung eines Wasserabscheiders nach dem Stand der Technik mit zwei unterschiedlichen Methoden zur Füllstandsmessung,
• 3 eine schematische Schnittzeichnung eines Wasserabscheiders in einer ersten Ausgestaltung der Erfindung,
• 4 eine schematische Schnittzeichnung eines Wasserabscheiders in einer zweiten Ausgestaltung der Erfindung,
• 5 eine schematische Schnittzeichnung eines Wasserabscheiders in einer dritten Ausgestaltung der Erfindung,
• 6 eine schematische Schnittzeichnung eines Wasserabscheiders in einer vierten Ausgestaltung der Erfindung,
• 7 eine schematische Schnittzeichnung eines Wasserabscheiders in einer fünften Ausgestaltung der Erfindung,
• 8 eine schematische Schnittzeichnung eines Wasserabscheiders in einer sechsten Ausgestaltung der Erfindung,
• 9 eine schematische Schnittzeichnung eines Wasserabscheiders in einer zehnten Ausgestaltung der Erfindung,
• 10 eine schematische Schnittzeichnung eines Wasserabscheiders in einer elften Ausgestaltung der Erfindung,
• 11 eine schematische Schnittzeichnung eines Wasserabscheiders in einer zwölften Ausgestaltung der Erfindung, und
• 12 eine schematische Schnittzeichnung eines Wasserabscheiders in einer weiteren Ausgestaltung der Erfindung,

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

• 1 a schematic representation of a fuel cell system according to the prior art;
• 2 a schematic sectional view of a water separator according to the prior art with two different methods for level measurement,
• 3 a schematic sectional view of a water separator in a first embodiment of the invention,
• 4 a schematic sectional view of a water separator in a second embodiment of the invention,
• 5 a schematic sectional view of a water separator in a third embodiment of the invention,
• 6 a schematic sectional view of a water separator in a fourth embodiment of the invention,
• 7 a schematic sectional view of a water separator in a fifth embodiment of the invention,
• 8th a schematic sectional view of a water separator in a sixth embodiment of the invention,
• 9 a schematic sectional view of a water separator in a tenth embodiment of the invention,
• 10 a schematic sectional view of a water separator in an eleventh embodiment of the invention,
• 11 a schematic sectional view of a water separator in a twelfth embodiment of the invention, and
• 12 a schematic sectional view of a water separator in a further embodiment of the invention,

1 shows a schematic representation of a generally designated 100 fuel cell system according to the prior art. This is part of an electric or hybrid vehicle, not shown, having an electric traction motor driven by the fuel cell system 100 is supplied with electrical energy.

The fuel cell system 100 comprises as a core component a fuel cell stack 10 containing a plurality of stacked single cells 11 which are formed by alternately stacked membrane-electrode assemblies (MEA) 14 and bipolar plates 15 (see detail). Every single cell 11 Thus, each comprises an MEA 14, which has an ion-conducting polymer electrolyte membrane not shown here, and arranged on both sides of catalytic electrodes, namely an anode and a cathode, which catalyze the respective partial reaction of the fuel cell reaction and in particular can be formed as coatings on the membrane.

The anode and cathode electrodes comprise a catalytic material, such as platinum, supported on an electrically conductive high surface area support material, such as a carbon based material. An anode space 12 is thus formed between a bipolar plate 15 and the anode, and the cathode space 13 is formed between the cathode and the next bipolar plate 15. The bipolar plates 15 serve to supply the operating media to the anode and cathode compartments 12, 13 and further interpose the electrical connection the individual fuel cells 11 ago. Optionally, gas diffusion layers are disposed between the MEA 14 and the bipolar plates 15.

To the fuel cell stack 10 to supply with the operating media, the fuel cell system 100 on the one hand, an anode supply 20 and on the other hand, a cathode supply 30 on.

The anode supply 20 of in 1 shown fuel cell system 100 includes an anode supply path 21 which feeds an anode operating medium (the fuel), for example hydrogen, into the anode spaces 12 of the fuel cell stack 10 serves. For this purpose, connect the anode supply paths 21 a fuel storage 23 with an anode inlet of the fuel cell stack 10 , The anode supply 20 further includes an anode exhaust path 22 containing the anode exhaust gas from the anode chambers 12 via an anode outlet of the fuel cell stack 10 dissipates.

The anode operating pressure on the anode side 12 of the fuel cell stack 10 is about a first actuating means 24 in the anode supply path 21 adjustable. In addition, the anode supply points 20 of in 1 shown fuel cell system as shown, a recirculation line 25 on which the anode exhaust path 22 with the anode supply path 21 combines. The recirculation of fuel is common in order to return and utilize the fuel, which is mostly used in excess of stoichiometry, in the stack. In the recirculation line is a recirculation conveyor 26 , preferably a recirculation blower, arranged.

Further, in the anode exhaust path 22 downstream of the fuel cell stack 10 and upstream of the recirculation line 25 a water separator 41 installed to with the anode exhaust gas from the fuel cell stack 10 discharge discharged liquid water. The liquid water is removed from the water separator 41 over the first derivative 40 an exhaust system A as the most downstream portion of the cathode exhaust gas line 32 fed. The first derivative 40 is by means of a controllable or adjustable valve 42 closable.

In the anode exhaust gas line 22 of in 1 shown fuel cell system 100 is upstream of the water separator 41 a second derivative 60 or a purine line 60 for discharging gas from the anode exhaust gas line 22 arranged. This second derivative 60 is also with a controllable or adjustable valve 61 closable and becomes the cathode exhaust gas line 32 downstream of the fuel cell stack 10 at a stack outlet S and in particular before the actuating means 38 fed.

The cathode supply 30 of in 1 shown fuel cell system 100 includes a cathode supply path 31 , which the cathode compartments 13 of the fuel cell stack 10 supplying an oxygen-containing cathode operating medium, in particular air which is drawn in from the environment. The cathode supply 30 further includes a cathode exhaust path 32 , which the cathode exhaust gas (in particular the exhaust air) from the cathode compartments 13 of the fuel cell stack 10 dissipates and this the exhaust system A supplies. For conveying and compressing the cathode operating medium is in the cathode supply path 31 a compressor 33 arranged.

In the illustrated embodiments, the compressor 33 as a mainly electric motor driven compressor 33 designed, the drive via a with a corresponding power electronics 35 equipped electric motor 34 he follows. The compressor 33 may also be through a in the cathode exhaust path 32 arranged turbine 36 (optionally with variable turbine geometry) are supported by a common shaft (not shown) driven.

This in 1 shown fuel cell system 100 also has a humidifier module 39 on. The humidifier module 39 on the one hand is in the cathode supply path 31 arranged so that it can be flowed through by the cathode operating gas. For this purpose, the humidifier module has a gas inlet and a gas outlet. On the other hand, it is so in the cathode exhaust path 32 arranged so that it can be flowed through by the cathode exhaust gas.

The cathode supply 30 also has a first shut-off means 37 and a second shut-off means 38 on, with the shut off the fuel cell stack 10 can be isolated from the environment. All adjusting means 24 . 37 . 38 . 42 . 61 of the fuel cell system 100 can be designed as controllable or controllable valves or flaps.

2 shows a schematic representation of a water separator 41 According to the state of the art. In the shown water separator 41 the arrangement of two level sensors is shown, usually only one of the two in the water 41 is provided. One is a float switch 52 shown starting from a minimum level on the water surface inside the water separator 41 on floats and when reaching a maximum rise height of the float a signal to reach the level 54 gives. Alternatively, a capacitive level switch 51 shown at a certain height of the water separator 41 is arranged, the a defined level 54 corresponds and detects depending on an electrical conductance the achievement of the water level of this height.

The following figures each show a cross section of a water separator according to the invention 41 in the longitudinal direction, as well as a cross section of the water separator 41 in the transverse direction at the height of a plane in which the water separator 41 is arranged, the level AA. In some partial representations, there is also a cross section through the water separator 41 shown along the plane BB.

3 shows a schematic sectional view of the water separator according to the invention 41 in a first preferred embodiment. Shown is that the hot wire 50 from the outside to the inside of the surrounding wall 46 of the housing 45 of the separator is guided. The wire used for detection is particularly short, which simplifies the production. The embodiment shown allows a discontinuous level measurement, that is, it is detected when the water has a defined level 54 has reached the height of the arrangement of the hot wire 50 equivalent.

In 4 is a further preferred embodiment of the invention in a schematic sectional view of a water separator 41 shown. This embodiment is also suitable for a discontinuous measurement. Compared to the design of the 3 extends the hot wire 50 but not only over a small area of the inner wall of the housing 45 of the water separator 41 , Rather, it extends to the detection of the level 54 inside the case 45 arranged hot wire 50 almost over the entire inner peripheral area of the wall 46 at a defined distance to the ground area. The distance to the ground area 43 defines the fill level to be defined 54 , The hot wire 50 can run both parallel to the floor area as well as at a certain angle to the floor area. In the latter case, a larger range of level measurement is accessible, but blurred the boundaries between discontinuous measurement and continuous measurement, that is, when reaching the level 54 not the entire surface of the hot wire 50 is washed with water, but initially only a part. The particular advantage of the embodiment of 4 is that even tilting the vehicle does not prevent the detection of reaching the mind, as the hot wire 50 on the inside of the separator 41 is guided around in the entire inner radius. In addition, this configuration is due to the much larger surface of the hot wire 50 in comparison to 4 less sensitive to dripping.

5 shows the schematic sectional view of a water separator 41 for continuous level measurement in a preferred embodiment of the invention. The hot wire 50 is not parallel to the ground in comparison to the embodiments described above, but rather extends between the floor area 43 and lid area 44 of the water separator 41 , Preferably, the hot wire is 50 while perpendicular to the ground area 43 arranged, as well as in 5 shown.

Another embodiment for continuous measurement is in 6 shown. 6 corresponds essentially to the execution of the 5 However, the surface of the hot wire is 50 inside the case 45 enlarged by the hot wire 50 in sweeping or grinding 55 is placed, with several sections of the hot wire 50 run parallel and these parallel sections by U-forming the hot wire 50 connected to each other.

7 to 9 and 11 show the arrangement of the heating wire inside the housing 45 using an insert element 53 , In the 7 . 9 and 11 is the insert element 53 in the bottom area of the housing 45 introduced. The individual figures show the arrangement of the hot wire 50 on the insert element 53 , In this case, alternatives are preferred that the largest possible contact surface of the hot wire 50 with the water in the water separator 41 enable. The shown embodiments of 9 and 11 are especially designed for continuous level measurement. In 8th is the insert element 53 from the lid area 44 in the case 45 brought in. The peculiarity of in 8th the embodiment shown is that of the hot wire 50 is arranged free floating at a defined distance from the ground area. As a section through the plane AA shows, the part of the hot wire, which can be in contact with the water, extends parallel to the bottom area. This will cause the achievement of a certain level 54 detected. So there is a non-continuous level measurement instead. The supply lines of the hot wire are inside the insert element 53 led to the outside. Also for non-continuous measurement serve the embodiments of 7 and 10 ,

Another embodiment of a non-continuous level measurement is in 10 shown schematically. 10 shows a schematic sectional view of a water separator according to the invention 41 in a further embodiment. It is at a defined distance to the bottom area similar to the in 3 shown embodiment, a small portion of the inner wall of the housing 45 with a hot wire 50 Mistake. Unlike the in 3 However, the embodiment shown is the contact surface of the hot wire 50 increased by forming loops or bends by a factor of four.

The 11 and 12 show preferred embodiments of a continuous level measurement, wherein 11 the use of an insert element 53 Provides which of the hot wire 50 is arranged and in 12 the hot wire 50 along the inner wall of the housing 45 extends. Both designs have in common that the hot wire 50 is arranged to increase the contact surface spirally along a Kreisbeziehungsweise cylinder circumference.

The operation of the level measurement in the embodiments shown follows in each case the same principle. The hot wire 50 is supplied via an outer line with a current and thus heated. Depending on the medium with which the surface of the hot wire inside the housing 45 is in contact, the hot wire 50 cooled so that increased power is required to maintain a constant temperature. Due to the different heat capacity or the different thermal conductivity of a gaseous and a liquid medium of the hot wire 50 depending on whether and how much of the surface is in contact with water, cooled to different degrees. If the surface is in contact with water, the cooling effect is greater and higher performance is required. Depending on the measuring method, the necessary power or a changing resistance in the hot wire 50 determines and determines the presence of water at a certain height of the housing 45 closed. In a non-continuous measurement, almost the entire surface of the hot wire abruptly 50 enclosed with water, so that a sudden strong cooling of the hot wire 50 through the water and a gradual change in measured value takes place. In a continuous level measurement, however, is due to the cooling effect on a level of water wetted surface of the hot wire 50 closed and depending on the arrangement of the hot wire in the housing 45 a current level is determined.

LIST OF REFERENCE NUMBERS

100

The fuel cell system

10

fuel cell stack

11

single cell

20

anode supply

21

Anode supply line

22

Anode exhaust gas line

23

fuel tank

24

first actuating means

25

recirculation

26

recirculation conveyor

30

cathode supply

31

Cathode supply line

32

Cathode exhaust gas line

33

compressor

34

electric motor

35

power electronics

36

turbine

37

first shut-off device

38

second shut-off device

39

humidifier

40

procedure

41

water

42

Abscheideventil

43

floor area

44

cover region

45

casing

46

wall

48

Supply line from the anode exhaust gas path

49

Supply line to the anode exhaust gas path

50

hot wire

51

Capacitive level sensor

52

float switch

53

insert element

54

defined level

55

Sweeping / grinding

60

second derivative

61

purge valve

Claims (10)

A water separator (41) for a fuel cell system (100), comprising a housing (45) having a wall (46), a bottom area (43) and a lid area (44), and an anode operating gas inlet (48), a drain (49) for anode operating gas and a drain (41) for waste water arranged in the bottom region (43) of the housing (45), characterized in that a hot wire (50) for level measurement is arranged in an interior of the housing (45). Water separator (41) according to any one of the preceding claims, characterized in that the hot wire (50) extends along at least a portion of an inner side of the wall (46). Water separator (41) according to claim one of Claims 1 and 2 , characterized in that the hot wire (50) is arranged in the housing (45), that a continuous level measurement takes place. Water separator (41) after Claim 3 , characterized in that the hot wire (50) extends between bottom region (43) and cover region (44). Water separator (41) according to one of Claims 1 or 2 , characterized in that the hot wire (50) arranged in the housing (45) in that a reaching of a predefined fill level (54) is detected by means of the hot wire (50). Water separator (41) after Claim 5 , characterized in that the hot wire (50) at a defined distance parallel to the bottom portion (43) is arranged, which corresponds to the defined level (54) and the hot wire (50) extends substantially transversely to the height of the housing (45). Water separator (41) according to any one of the preceding claims, characterized in that the hot wire (50) is integrated in an insert element (53) and the insert element (53) is arranged variable or fixed in the housing (45). Water separator (41) according to any one of the preceding claims, characterized in that the hot wire (50) over several turns / loops (55) or spirally guided around a circumference. Method for determining a fill level of water in a water separator (41) according to one of the preceding claims, wherein a fill level of the water is determined as a function of an electrically determinable cooling effect of the water on the hot wire (50). Method according to Claim 9 , characterized in that the hot wire (50) is energized continuously and constantly and a decrease in a measured voltage of the hot wire (50) is proportional to the level of water in the water separator.

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