DE10010400C2 - Device and method for heating and / or evaporating liquid or gaseous media - Google Patents

Description

The present invention relates to a device for heating and / or evaporation liquid or gaseous media according to the preamble of claim 1. The invention further relates to a method for heating and / or evaporation liquid or gaseous media according to the preamble of claim 16. Finally, the invention also relates to a special use of the device and of the procedure.

Devices for heating and / or evaporating liquid or gaseous media are already known and are used for different tasks. A advantageous, exemplary application for evaporators is in the range Fuel cell technology. Fuel cells have been known for a long time and have significantly in the automotive industry in particular in recent years gained in importance.

Similar to battery systems, fuel cells generate electrical energy chemical way, but the individual reactants from the outside continuously fed and the reaction products are continuously removed. Here lies the Fuel cells are based on the functional principle that there are electrically neutral molecules or connect atoms and exchange electrons.

This process is called the redox process. With the fuel cell, the Oxidation and reduction processes spatially separated from each other via a membrane Cut. The membranes used have the property of protons  exchange, but retain gases. The given in the reduction Electrons can be conducted as electrical current through a consumer, for example the electric motor of an automobile.

As gaseous reactants for the fuel cell, for example Hydrogen is used as fuel and oxygen as oxidant. Do you want that Fuel cell with an easily available or easy to store fuel such as Operate natural gas, methanol, gasoline or the like, you have to Hydrocarbons in an arrangement for producing / processing a fuel first convert to a hydrogen-rich gas. At least one of the Reactor elements of the arrangement for generating / processing the fuel is it is an evaporator. The evaporator has the task of being the raw material (Fuel and / or water) to obtain the suitable for the fuel cell Evaporate fuel before it is in the vapor state further treatment in the next reactor element, for example in one Reformer is initiated.

The known devices for heating and / or evaporating liquid or vaporous media, but have a number of disadvantages, especially when when used as an evaporator.

The known devices usually have at least one Flow device for the medium to be treated with one or more Flow-through layers, the flow-through layer each having a number of Flow channels are provided. The flow channels have their Entry side via an entry opening and on their exit side via an exit opening. The medium to be evaporated or heated passes over the An entry opening into the flow channels, flows through them, it being by means of a Heater is heated or evaporated, and then occurs at the Exit side via the outlet opening from the respective flow channel. The Through-flow channels are connected via their inlet openings to the supply line medium which is to be heated and / or to be evaporated and via its outlet openings a corresponding derivative connected. There is usually one in this supply line Conveying device, for example a pump, provided that the medium in the Flow channels pumped into it. This conveyor is usually like this  designed that they have only a slight overpressure compared to the pressure at the Outlet openings of the flow channels created.

The provision of those required for heating and / or evaporating the medium Thermal energy takes place via at least one heating device which consists of or several layers is formed and which with the flow device in the sense of a Heat exchanger is connected. The heating device can, for example have a number of electrically operated heating cartridges. The heating cartridges are all driven with the same power, so that the heating cartridges in the Flow channels generated surface temperature over which the Medium flowing through flow channels is heated or evaporated, along the entire flow device through the flow channels approximately is the same if the medium is not yet flowing through the flow channels.

Due to the low overpressure of the pump, especially when Start-up of the device in the entry area around the entry openings of the Flow channels form a vapor bubble, because the medium due to the high Surface temperatures already in the inlet area of the flow channels starts to evaporate. The pressure in the vapor bubble can result from the Flow resistance in the upstream part of a flow channel, in which, for example, may not yet have vaporized droplets, so high that it reaches or even exceeds the pump pressure. This can take under Circumstances of the liquid column against the actual flow direction be pushed back or come to a standstill. The smaller the cross section of the Flow channels, the greater the flow resistance and thus the Danger that the flow rate through the device is significantly reduced. in the At worst, the situation may arise that the flow through the device is even completely prevented.

This also means that the thermal energy generated by the heating cartridges is not can be derived to a sufficient extent so that the entire device undesirably overheated.

The present invention is based on the cited prior art Task based on a device and a method of the type mentioned to further develop such that the disadvantages described are avoided.  

In particular, an apparatus and a method are to be provided with heating in a simple yet reliable manner and / or Evaporation of a liquid or gaseous medium is made possible.

This object is achieved according to the first aspect of the present invention by a device for heating and / or evaporating liquid or gaseous Media, with at least one flow device, the one or more Flow layers with one or more flow channels for each Medium, wherein the flow channels each have an inlet opening and Have outlet opening and the inlet opening with a feed line and the Outlet opening can be connected to a discharge line for the medium, and with at least a heating device formed from one or more layers for Provide those needed to heat and / or evaporate the medium Thermal energy generated by the flow device in the sense of a heat exchanger connected is. This device is characterized in that the heating device is designed such that the surface temperature of the Flow channels at least in individual areas of the flow channels in Flow direction (D) of the medium can be set independently of other areas are.

The adjustability of the surface temperature in the flow direction of the Medium through the flow channels can be reliably prevented the disadvantageous vapor bubble described above in the area of the inlet openings the flow channels can form. Avoiding such a vapor bubble can are particularly advantageously prevented if that Surface temperature profile is designed such that the temperature in Entry area of the throughflow channels is significantly smaller than in the rest of them Areas. Advantageous embodiments, such as a suitable temperature profile can be set will be explained in more detail later in the description.

The device according to the invention is basically suitable for heating media and / or evaporate. It is particularly advantageous if the Flow-through layer each in micro technology with micro-channels for the passage of the medium to be treated is formed.  

For example, the device according to the invention can be used to to heat gaseous or liquid media. The media is heated in such a way that over the heating device along the flow device on the Such a temperature profile is set on the surfaces of the flow channels that A sufficiently low temperature in the inlet area of the flow channels Medium prevails in which the formation of a vapor bubble is reliably prevented. In the areas of the throughflow channels following the inlet area, a higher temperature can be set so that the gaseous or liquid medium is heated to the desired temperature.

Another possible application of the device according to the invention is for example in their use as an evaporator for a liquid medium. In In this case, the temperature profile on the surfaces of the flow channels again set so that the temperature in the inlet area of the throughflow channels so it is small that the formation of a vapor bubble is prevented. In the subsequent Areas are located at a sufficient distance from the entrance area over the Heating device provided so much heat energy that the Medium flowing through channels can be evaporated. In it Subsequent areas then heat energy according to the required Outlet temperature of the steam supplied.

In the following, the invention is based on a vaporizer Device described. However, it goes without saying that the invention is not based on this special configuration is limited.

The evaporator has at least one throughflow device through which the evaporating liquid medium is passed through. The flow device comprises one or more flow layers, each with one or more Flow channels. The liquid medium to be evaporated appears on the Inlets of the flow channels, flows through and leaves the Flow channels through their outlet openings. During that to be evaporated liquid medium the flow channels of the at least one flow device flows through, it is provided by the at least one further Heater heats and evaporates.  

The heating device, which is connected to the flow device, exists from one or more layers and can be formed in different ways his. In principle, the invention is not based on a specific embodiment of the Heating device limited. Rather, this only has to be suitable for Heating and / or evaporation of the medium required thermal energy available to deliver.

Advantageously, more than one throughflow device and one Heating device may be provided. Each is preferably one Flow device and a heating device alternately one above the other arranged so that a layer sequence arises. The number of for the device, for example the evaporator, flow devices used and Heating devices result in particular from the performance requirements for the Contraption.

The throughflow device and the heating device are thus together connected that the thermal energy generated by the heating device on the Flow channels of the medium flowing through the flow device can be.

According to the heating device is designed such that in the Flow channels along the flow device Surface temperature independent of others, at least in some areas Ranges is adjustable. Since the medium from a supply line at the inlet openings the flow channels enter them, the flow channels over their entire length Flows through and then at the outlet openings at the end of the The flow profile emerges through a drainage pipe again Heat absorbing medium also over the length of the flow channels influenced.

Due to the inventive design of the device, the supply of the Heating and / or evaporation of the thermal energy provided in a targeted manner be controlled that a vapor bubble in the area of the inlet openings of the Flow channels is safely prevented, the medium nevertheless on the desired temperature can be brought.  

As has already been stated with regard to the prior art, joined known evaporators the case that during the heating of the Evaporator before this formed a kind of steam plug. This was through Evaporation of the medium generated directly at the inlet area of the flow channels. The steam thus generated was not immediately along the flow direction dissipated, but dammed up in front of the canals. Against this stopper, the one Formed overpressure, the conveyor arrived only to a limited extent, so that the delivery rate set on the conveyor was drastically reduced. As part of the further development of the well-known evaporator has now been surprisingly found that after switching off the Heating device of the entry area of the device or the Flow channels quickly cool down so that no steam plug in front of the Flow channels is built up more. The medium is so far from Entry area away inside the evaporator that evaporates it Evaporator leaves in the direction of flow without any significant Obstruction of the liquid supply leading overpressure of the steam, is built up, for example, by liquid drops in microchannels. The Conveyor can therefore the set flow rate through the evaporator conduct. This effect was used in the device according to the invention.

To avoid the heater being actuated first and then must be switched off so that trouble-free heating and / or evaporation of the medium, the device is according to the invention in this regard have been further developed that on the surface of the flow channels Temperature profile in the direction of flow can be set so that a continuous operation of the device is possible.

Advantageous embodiments of the device result from the Dependent claims.

The flow layers in microstructure technology and the Flow channels can be designed as microchannels. By designing the Device in microstructure technology is achieved that this at high Performance can be trained to save space. It is in  generally provided that in a small space in the cubic centimeter range a large number of several thousand microchannels is arranged. Through this Microchannels, each with a height and width of only a few µm, are large specific surfaces, i.e. high ratios of channel surface to Channel volume created through which the heat exchange takes place particularly effectively. This makes such devices, especially when used as evaporators become extraordinarily powerful.

When an evaporator is connected to a fuel cell system, such as one Fuel cell system for a vehicle that is to be used is usually only available a small amount of space is available. For this reason, the individual Components of the fuel cell system are made as small as possible. To an evaporator using microstructure technology can be used for this purpose, for example become.

The heating device is regularly designed such that the temperature of the Inner surface free and at least in individual areas of the flow channels is adjustable independently of other areas. This allows the temperature profile be adapted to the current conditions. With conventional Heat exchangers and evaporators can be the performance of the heat source usually affect only as a whole, so that in the event of a throttling Surface temperature lowered over the entire length of the flow channels becomes.

According to the heating device is designed such that in the Flow channels along the flow device a temperature profile in the Medium is adjustable according to the relationship T1 <T2 <T3, with T1 = temperature in Entry area of the flow channels, T3 = temperature in the exit area of the Flow channels and T2 = temperature in the area between the inlet area and the outlet area of the flow channels. This is done through an appropriate choice of Surface temperature in the flow channels reached and should be based on a Example are clarified.

If, for example, water is to be evaporated in the device, the such a surface temperature generated by the heating device  Temperature profile can be set in the medium that in the entry area of the Flow channels prevailing temperature T1 is so small that a Vapor bubble can not form in front of the inlet openings of the flow channels. For example, the temperature T1 can be chosen so that the water in the The inlet area of the flow channels does not exceed a temperature of 80 ° C. in the the flow of the flow channels must open the water Boiling temperature T2 are heated and evaporated. For this, the Surface temperature of the flow channels in the area that corresponds to the The inlet area of the flow channels clearly connects the evaporation temperature exceed. For example, the surface temperature can be chosen so that the water or the water vapor already formed up to depending on the pressure a temperature T2 of 150 ° C is heated.

The length of the entry area and the second area are selected preferably such that the evaporation of the water only as far as possible Inside the flow channels takes place. This ensures that always a sufficient amount of liquid in the flow channels can flow in, so that there is no excess pressure in the inlet region of the channels can build up, which reduces the flow rate.

In order to overheat the now evaporated water so that the escaping steam has a temperature T3 required for further process steps, the im Outlet area of the flow channels set surface temperature clearly can be set higher. For example, heating the steam in the Flow channels are aimed at a temperature T3 of about 230 ° C, for which purpose the channel surface in the outlet area are heated to, for example, 350 ° C. would.

The example described above is purely exemplary Values that reflect the basic idea of setting a temperature profile should clarify. However, the invention is not based on the temperature values mentioned limited. Rather, the setting of the required temperatures depends of the media to be heated and / or evaporated and the structure of the Flow channels. About the structure of the flow channels, preferably as Microchannels are formed, the surface is fixed, which with the  heating or evaporating medium comes into contact. The bigger the area of contact between the medium and the surface, the better heat can be be transmitted.

The heating device advantageously has a plurality of layers in which the Setting the temperature profile, an electric heating device, in particular two or more electric heating elements are provided. Such heating elements can, for example, but not exclusively, as Heating wires, heating cartridges or the like may be formed. When operating one with the Electric power source connected heating elements is in the heating elements Generates heat, which then to be heated or evaporated Medium can be transferred.

At least individual heating elements are free and independent of the others Adjustable heating elements. This makes a simple yet accurate setting the temperature profile in different areas of the flow channels in medium flowing through the existing surface temperature in the Flow channels possible.

This will be described using an example. In this example, in Based on the three temperatures T1 to T3 used a total of three electrical heating elements. However, it is of course, that the invention is not limited to a certain number Heating elements or different to be set Temperature ranges of the temperature profile is limited. Rather, it results Number of heating elements required, such as the number of different ones Temperature ranges of the temperature profile according to the respective specific requirement to the device.

If, as described, three heating elements are used, the first is Heating element preferably arranged in the heating device such that the heat energy given off the temperature T1 of the medium in Entry area of the flow channels influenced. The third heating element is preferably arranged in the heating device such that it is the temperature T3 of the temperature profile in the outlet area of the flow channels is determined. The  second heating element is preferably between the first and third Heating element arranged and determines the temperature T2 of the temperature profile of the Medium, which is set in that area of the flow channels that is located between the entry area and the exit area.

To prevent the formation of a harmful vapor bubble at the inlet openings of the To prevent flow channels, the first heating cartridge should be comparatively low heat output can be operated. In this way it is achieved that medium to be heated or evaporated in the inlet area of the Flow channels do not reach the evaporation temperature and in liquid State remains. A solution can also be provided in which a Heating element in the entry area is completely dispensed with. The third heating element can be subjected to high heating power, while by a Performance variation in the middle, second heating element, the temperature profile varies can be so that the entry of the medium to be evaporated in the Evaporation area in the throughflow channels targeted and individually as required can be moved along the longitudinal axis of the channel.

In such an embodiment, the second heating element is advantageously freely controllable trained, while the first and the third heating element each not adjustable can be trained. However, it is also possible that all heating elements are free and so that they can be regulated independently of each other. This leaves a very precise and targeted Setting the temperature profile and the steam outlet temperature too.

The heating elements can preferably be transverse, in particular perpendicular to Flow direction of the medium extend over several flow channels.

According to another embodiment, the heating device can be one or have several layers, each one for setting the temperature profile Include number of channels for a heat transfer medium.

These layers are preferably in microstructure technology and the corresponding ones Channels designed as micro-channels. The advantages are based on the above Versions in connection with the flow device for the medium directed.  

In this embodiment, it is used to heat and / or evaporate the medium required heat energy not via electrical heating elements but via a Corresponding heat transfer medium, for example as a liquid such as oil or the like can be provided. If that is to be heated or the medium to be evaporated, the flow channels of the Flows through, it is through the channels of the layers of Heating device flowing through the heat transfer medium and heated if necessary evaporated.

The channels of the layers and the flow channels of the Flow layers be angled, preferably perpendicular to each other ( "Cross-flow design"). If the device is used as an evaporator, this means that the liquid to be evaporated flows in one direction the corresponding flow channels flow perpendicular to the orientation of the Channels in which the heat transfer medium is located are aligned.

However, it is also conceivable that the channels of the layers and the flow channels the flow layers are aligned parallel to one another. In one The medium to be heated or evaporated can be constructed the heat transfer medium, if it is, for example, liquid or gaseous flow through the respective channels in parallel or in the "countercurrent principle".

The individual channels of the layer can be used to set a temperature profile are flowed through with heat transfer media of different temperatures. at the channels of the layers and the Flow channels of the flow layers, preferably in "cross-flow construction" aligned. For setting the respective temperature ranges of the temperature profile is in the flowing medium along the flow device in this case provided that in the corresponding areas of the heating device intended channels with different names, the respective Heat transfer media adapted to temperature requirements are flowed through.

The provision of different heat transfer media can be different Way. For example, it is possible to use different sources  to provide different heat transfer media. With such a Embodiment then becomes the respective channels with the corresponding sources the heat transfer media connected.

However, it is also conceivable that only a single heat transfer medium source is provided with all channels through which the heat transfer medium flows should be connected. The heat transfer medium can then outside of Device in the respective supply line to the various channels of the Heating device heated by a suitable heating source and in need differently heated condition through the dedicated channels of the Heating device can be passed. The from the heat transfer medium Stored thermal energy is added to the one to be heated or evaporating medium released. The heating of the heat transfer medium to the the required temperature can be achieved, for example, using electrical heating elements, suitable heat exchangers or the like.

In a further embodiment, the channels of the layers can be coated catalytically his. In this case, a heat transfer medium under the influence of catalytic coating provided exothermic reaction medium his. When this reaction medium flows through the channels, the appropriate coating of the channel walls triggered a reaction, causing heat arises. This heat can affect what is to be heated or evaporated Medium that flows through the flow channels of the flow device, be transmitted.

If the required thermal energy is provided in this way, are the channels of the heating device and the flow channels of the Flow device preferably according to the "counterflow principle" aligned. In this case, the outlet area of the throughflow channels corresponds with the entrance area of the channels of the heating device. If that Reaction medium flows through the catalytically coated channels, it is in the The entrance area of the channels initially leads to a very violent reaction, in which a lot of heat is released. In this way, in the flow channels whose outlet area a very high temperature can be set. If that Reaction medium the catalytically coated channels in the further course  flows through, the intensity of the reaction occurring and thus the amount of resulting heat energy is becoming weaker and weaker. In the exit area the catalytic coated channels, the response is weakest because much of the Reaction medium has already reacted. In the exit area the catalytic Coating channels is therefore only one relative to the requirements small amount of thermal energy provided.

Since the catalytically coated channels and the flow channels are preferably in Flowing through "countercurrent principle", this means that the Medium flowing through flow channels in the inlet area of the flow channels only a little heat energy is supplied, the amount of the supplied Thermal energy in the further flow of the medium through the Flow channels becomes increasingly larger. In the end area of the flow channels the greatest available thermal energy. This allows the With regard to the electrical heating elements already described advantageous effects be achieved with regard to the setting of the temperature profile.

The channels of the layers can preferably have one or more regions each have a different catalytic coating. The temperature profile can by such a variation of the catalytic coating, for example one Variation in the heating device in the direction of the longitudinal axis of the channels, targeted to be influenced.

At least one can be in the feed line to the inlet opening of the flow channels Conveying device, in particular a pump, may be provided. Through the Possibility according to the invention, a temperature profile freely in the flow channels adjust, a conveyor can be used, which is opposite the Ambient pressure generated only a slight excess pressure. Such funding institutions are easy and inexpensive to manufacture.

In a further embodiment, the. In the feed line in the area of the inlet opening Flow channels and / or in the discharge in the area of the outlet opening Flow channels, a temperature sensor may be provided. About this Temperature sensor or these temperature sensors can Temperatures of the medium when entering the device and when leaving the device  Device can be detected. The setting can be made by recording the temperatures controlled the appropriate surface temperature in the flow channels become. If the temperature in the inlet area of the flow channels is too high by means of appropriate control of the heating device, for example, the respective electrical heating elements, the temperature in Entry area can be lowered. In a corresponding way, the temperature profile can also be varied to higher temperatures if necessary. A heating device can also be provided within the scope of the invention except in the sense of a heating device operated with a heat transfer medium an additional heater also includes an electric heater. In this way could advantageously be a base load of heating via the heat transfer medium be introduced while the required higher temperatures in some areas can be generated via the particularly easy-to-control electrical auxiliary heating.

According to a second aspect of the present invention, a method for Heating and / or evaporating liquid or gaseous media using a device according to the invention as described above provided at the medium to be heated and / or evaporated one or more Flow channels flow through at least one flow device and thereby via at least one heating device for providing thermal energy, the with the at least one flow device in the sense of a heat exchanger is connected, heated and / or evaporated. The method is according to the invention characterized in that the heating device for influencing the Surface temperature in the flow channels in the direction of flow of the medium at least in individual areas among independently adjustable Operating conditions. The medium is therefore different Areas of the flow channels in the flow direction of different heights Exposed to temperatures.

In this way, a method is created with which liquid or gaseous Media heated in a simple yet reliable manner can be evaporated without occurring in the prior art can form disadvantageous vapor bubbles in the inlet area of the flow channels. To the advantages, effects, effects and the functioning of the invention  The method is based on the above statements on the invention Device fully referenced and hereby referenced.

The invention provides that the temperature profile of the medium at least in individual Areas of the flow channels freely and independently of other areas varied can be. The surface temperature of the flow channels can be advantageous be set so that in the entrance area of the flow channels Lowest temperature prevails with regard to the desired temperature profile.

To set the required surface temperature in a range of An electrical heating device can also flow through channels accordingly electrical power can be operated in different areas. In case of a with a heat transfer medium operated heating device Heat transfer medium with a correspondingly different in some areas Start temperature in the respective inlet opening of the flow channels become. Also by varying the flow rate of the Heat transfer medium in individual flow channels compared to others an influence on the surface temperature in an area along the Flow-through device for forming a desired temperature profile in the effect treating medium. Of course, as above already mentioned with regard to the device, by an additional electrical heater by a heating device operated with a heat transfer medium available surface temperature can be raised locally, if necessary especially in the exit area of the flow channels.

An inventive as described above can be particularly advantageous Device and / or a method according to the invention as described above for heating and / or vaporizing a fuel and / or a fuel be used.

Such a fuel and / or fuel can be used, for example, to operate a Fuel cell system can be used. A fuel cell system consists of Usually made up of one or more fuel cells that have at least one supply line and at least one discharge line for a fuel and at least one supply line and  have at least one derivation for an oxidizing agent. Still is usually a device for generating / processing the fuel provided in which the fuel from a starting material (fuel) initially is manufactured or processed.

The device for producing / processing the fuel can advantageously be a Have number of reactor elements, for example an evaporator, one Reformer, a shift reactor and a selective oxidation reactor. The individual reactor elements are connected to one another via corresponding lines connected so that the fuel during its generation respectively Processing flows through the individual reactor elements one after the other. At least one of the reactor elements, preferably the evaporator, is as one as above described inventive device formed. Such an evaporator is about required if hydrogen from methanol, gasoline, natural gas, ethanol or other liquid hydrocarbons to be reformed. The evaporator must heat is supplied for operation.

A fuel cell system as described above can be advantageous in one or used for a vehicle. Due to the rapid development in the Fuel cell technology in the automotive sector currently offers such use particularly good uses. Still there are others Possible applications. Examples include fuel cells for mobile devices such as computers or the like to stationary facilities such as Power plants. Fuel cell technology is also particularly suitable for decentralized energy supply of houses, industrial plants or the like.

Preferably, the present invention is in connection with Fuel cells with polymer membranes (PEM) are used. These fuel cells have a high electrical efficiency, cause minimal emissions, have optimal part-load behavior and are essentially free of mechanical wear.

The invention will now be described by way of example using exemplary embodiments explained in more detail with reference to the accompanying drawing. Show it:  

Fig. 1 in a highly schematic and simplified view of an inventive device for heating and / or evaporation of media as well as various peripheral devices,

Fig. 2 shows a schematic, side view of an inventive device for heating and / or evaporating media and

Fig. 3 is a schematic plan view of the entrance area of the device according to the invention, as shown in Fig. 2.

In Fig. 1, an apparatus 10 is illustrated for heating and / or evaporation of media that is formed in the present embodiment as an evaporator for liquid media. The evaporator 10 can, for example, be part of a device (not shown) for producing / processing a fuel for a fuel cell system (also not shown). However, the invention is not restricted to this special application form, so that the device 10 can basically be used for all applications in which a liquid or gaseous medium is to be heated and / or evaporated.

The device 10 is connected on its input side 11 to a feed line 13 via which the liquid medium to be evaporated, for example a fuel such as methanol, ethanol, gasoline or the like, which serves as the starting material for the fuel of a fuel cell, is introduced into the evaporator 10 . On its outlet side 12 , the evaporator 10 is connected to a discharge line 14 , via which the fuel converted into the vapor state is discharged from the evaporator 10 and fed to other reactor elements, such as a reformer (not shown). In order to set a predetermined delivery rate, a delivery device 15 , designed as a pump, is provided in the feed line 13 , with which a low overpressure compared to the ambient pressure can be generated.

A temperature sensor 16 , 17 is provided in the feed line 13 and in the discharge line 14 for temperature measurement at the inlet and at the outlet of the evaporator 10 .

The evaporator 10 and its mode of operation will now be described in more detail in connection with FIGS. 2 and 3.

The evaporator 10 is designed using microstructure technology. It has a total of three throughflow devices 20 , each of which has two throughflow layers 21 with a number of throughflow channels 22 . The throughflow layers 21 are in microstructure technology and the throughflow channels 22 are in the form of microchannels. On the upper and lower side, the evaporator 10 is closed off with an upper cover element 40 and a lower cover element 41 , respectively. Heating devices 30 are provided between the individual flow devices 20 . In the present example, the heating devices 30 each consist of a layer 31 in which a number of heating elements, in the present case three electrical heating elements 32 , 33 , 34 , are arranged.

The heating elements 32 , 33 , 34 , the z. B. can be designed as heating coils, heating cartridges or the like are connected to an electrical power source, not shown. When electrical power is received from the electrical power source, the heating elements 32 , 33 , 34 heat up. The thermal energy generated in this way can be released to the through-flow channels 22 and there ensure a correspondingly high surface temperature.

Even if three heating elements are provided per layer 31 in the example according to FIGS. 2 and 3, the invention is not restricted to this special number of heating elements. Likewise, as has already been explained in detail in the description above, the use of electrical heating elements can be dispensed with. Instead, different layers with channels can be provided, the structure of which corresponds approximately to the flow-through layers 21 and the flow-through channels 22 . A correspondingly suitable heat transfer medium with the temperature required for the desired surface temperature can then be passed through these channels.

In the exemplary embodiment according to FIGS. 2 and 3, a total of two heating devices 30 are provided, which are arranged between the throughflow devices 20 , so that an alternating layer sequence of in each case one throughflow device 20 and one heating device 30 results. The number and arrangement of the required throughflow devices 20 and heating devices 30 for the evaporator 10 are determined depending on the need and application.

The operation of the evaporator 10 will now be described.

The medium to be evaporated enters the flow channels 22 as a medium inflow 42 from the feed line 13 shown in FIG. 1 via corresponding inlet openings 26 . It then flows through the flow channels 22 in the flow direction D, that is to say in the direction of the longitudinal axes of the flow channels 22 . During the flow through the flow channels 22 , the initially liquid medium is evaporated. The medium which has passed into the vapor state leaves the evaporator 10 or the flow channels 22 as a medium outflow 43 via corresponding outlet openings 27 of the flow channels 22 . The now vaporous medium is then passed on via the derivation 14 shown in FIG. 1.

In order to avoid that a as described in the prior art adverse vapor bubble in the region of the inlet openings of the flow channels may form 22 26, whereby a flow through the flow channels 22 can be hindered or with the medium to be evaporated even prevented, the invention provides that on the heating means 30 in the flow passages 22 of the medium a profile of surface temperatures is set in a flow direction D, so that the flow channels 22 by flowing medium 22 is exposed to high temperatures in sections different in different areas of the flow channels.

In the exemplary embodiment, this is achieved by the heating elements 32 , 33 , 34 . These heating elements are aligned perpendicular to the flow channels 22 and each extend over all flow channels 22 of the associated flow layers 21 . In this way, an evaporator 10 is created in which the thermal energy generated and provided by the heating elements 32 , 33 , 34 is transferred in sections to the medium to be evaporated flowing through the through-flow channels 22 . This corresponds roughly to a "cross-flow design" with the difference that the electrical heating elements can emit the same high heat output over their entire length, while in an evaporator heated by means of a heat transfer medium the heat output decreases continuously from flow channel to flow channel due to the decreasing temperature of the heat transfer medium ,

The individual heating elements 32 , 33 , 34 are freely and independently controllable. Via the heating elements 32 , 33 , 34 , a temperature profile of the medium in the flow direction D through the flow channels 22 can be set according to the relationship T1 <T2 <T3, with T1 the temperature in the inlet area 23 of the flow channels 22 , with T3 the temperature in the outlet area 24 of the flow channels 22 and T2 denotes the temperature in the area 25 between the inlet area 23 and the outlet area 24 of the flow channels 22 .

In order to prevent the formation of a vapor bubble in front of the inlet openings 26 of the through-flow channels 22 , the heating element 32 is heated only slightly, so that the lowest temperature with regard to the temperature profile is set in the inlet region 23 . This temperature T1 is to be selected so that the medium to be evaporated is heated but not already evaporated. In this way, the medium to be evaporated can be preheated, but can enter the flow channels 22 while still in a liquid state. Furthermore, it is ensured that the liquid medium remains in the liquid state in the entire inlet area 23 of the flow channels 22 . The heating element 34 corresponding to the outlet area 24 of the throughflow channels 22 can be subjected to very high heating power, while the temperature profile in the area 25 of the throughflow channels 22 can be varied by a power variation in the middle heating element 33 . In this way, the location where the medium, which was still liquid by then, begins to change into the vapor state can be shifted forwards or backwards within the through-flow channels 22 , as required. If the heating element 33 is subjected to only a low heating power, this means that the surface temperature prevailing in the flow channels 22 and consequently also the temperature T2 of the medium is low, as a result of which the evaporation of the liquid medium is reduced or suspended. If, on the other hand, the heating element 33 is subjected to a high heating line, the surface temperature in the throughflow channels 22 will also increase, so that a larger proportion of the liquid medium is evaporated in the region 25 .

The setting and control of the respective heating elements 32 , 33 , 34 can take place via corresponding control signals which are generated via temperature measurements with the aid of the temperature sensors 16 , 17 .

In order to be able to achieve complete and trouble-free evaporation of a liquid medium, the heating element 32 is subjected to such a heating power that the still liquid medium flowing through the flow channels 22 is exposed to a surface temperature at which it heats up to a temperature T1, however is not yet evaporated. After the still liquid medium has left the inlet area 23 of the flow channels 22 , it comes into the area of influence of the heating element 33 . This heating element 33 is subjected to an increased heating power, so that the still liquid medium in the area 25 of the throughflow channels 22 following the entry area 23 is exposed to a surface temperature above the evaporation temperature T2 so that it is evaporated. Since liquid medium always flows in from the inlet area 23 , it is reliably prevented that a disturbing vapor bubble can form in front of the inlet openings 26 of the throughflow channels 22 . In order to ensure that the vaporous medium outflow 43 emerging from the throughflow channels 22 via the outlet openings 27 has the temperature required for the further process steps, it may be necessary to overheat the vaporous medium in the outlet region 24 of the throughflow channels 22 . For this purpose, the heating element 34 corresponding to the outlet area 24 of the throughflow channels 22 is acted upon with very high heating power. In this way, a correspondingly high surface temperature is generated, to which the already evaporated medium in the outlet region 24 of the throughflow channels 22 is exposed, so that it heats up to the superheating temperature T3. The gaseous medium outflow 43 which has been overheated in this way can be fed via the discharge line 14 to further process steps or reactor elements, such as, for example, a reformer.

LIST OF REFERENCE NUMBERS

10

Device for heating / evaporating media (evaporator)

11

input side

12

output side

13

supply

14

derivation

15

Conveyor (pump)

16

temperature sensor

17

temperature sensor

20

throughflow

21

Durchströmschicht

22

flow-through

23

entry area

24

exit area

25

Area between entrance area and exit area

26

inlet opening

27

outlet opening

30

heating means

31

layer

32

heating element

33

heating element

34

heating element

40

Cover element (top)

41

Cover element (bottom)

42

Medium-influx

43

Medium effluent
D flow direction

Claims (20)

1. Device for heating and / or vaporizing liquid or gaseous media, with at least one throughflow device ( 20 ) which has one or more throughflow layers ( 21 ), each with one or more throughflow channels ( 22 ) for the medium, the throughflow channels ( 22 ) each have an inlet opening ( 26 ) and an outlet opening ( 27 ) and the inlet opening ( 26 ) can be connected to a feed line ( 13 ) and the outlet opening ( 27 ) to a discharge line ( 14 ),
and with at least one heating device ( 30 ) formed from one or more layers ( 31 ) for providing the thermal energy required for heating and / or evaporation of the medium, which is connected to the throughflow device ( 20 ) in the sense of a heat exchanger,
characterized by
that in order to set a desired temperature profile on the surfaces of the flow channels, at least in individual areas ( 23 , 24 , 25 ) of the flow channels ( 22 ) in the flow direction (D), the heating power of the heating device ( 30 ) can be set in certain areas independently of other areas. 2. Device according to claim 1, characterized in that the flow-through layers ( 21 ) in microstructure technology and that the flow-through channels ( 22 ) are designed as micro-channels. 3. Apparatus according to claim 1 or 2, characterized in that the heating device ( 30 ) has one or more layers ( 31 ), in each of which an electrical heating device is provided for setting the temperature profile. 4. The device according to claim 3, characterized in that the electric heating device has two or more electric Heizele elements ( 32 , 33 , 34 ) and at least individual heating elements ( 32 , 33 , 34 ) are freely and independently controllable from the other heating elements. 5. The device according to claim 3 or 4, characterized in that the heating elements ( 32 , 33 , 34 ) extend transversely to the direction of flow (D) of the medium over a plurality of flow channels ( 22 ). 6. Device according to one of claims 1 to 2, characterized in that the heating device ( 30 ) has one or more layers ( 31 ) which each comprise a number of channels for a heat transfer medium for setting the temperature profile. 7. The device according to claim 6, characterized in that the layer (s) ( 31 ) in microstructure technology and that the channels are / are designed as microchannels. 8. The device according to claim 6 or 7, characterized in that the channels of the layer (s) ( 31 ) and the flow channels ( 22 ) of the flow layers ( 21 ) are angled, in particular perpendicular, to each other. 9. Device according to one of claims 6 to 8, characterized in that individual channels of the layer (s) ( 31 ) for setting the temperature profile with heat transfer media of different temperatures are flowed through or can be flowed through. 10. The device according to claim 6 or 7, characterized in that the channels of the layer (s) ( 31 ) and the flow channels ( 22 ) of the flow layers ( 21 ) are aligned parallel to each other. 11. Device according to one of claims 6 to 10, characterized in that the channels of the layer (s) ( 31 ) are coated catalytically and that a reaction medium which exothermically reacts under the influence of the catalytic coating is provided as the heat transfer medium. 12. The device according to claim 11, characterized in that the channels of the layer (s) ( 31 ) have one or more areas, each with a different catalytic coating. 13. Device according to one of claims 1 to 12, characterized in that in the feed line ( 13 ) at least one conveyor ( 15 ), in particular a pump, is provided. 14. The apparatus according to claim 1 to 13, characterized in that in the feed line ( 13 ) in the region of the inlet opening ( 26 ) of the flow channels ( 22 ) and / or in the discharge line ( 14 ) in the region of the outlet opening ( 27 ) of the flow channels ( 22 ) a temperature sensor ( 16 , 17 ) is provided. 15. Device according to one of claims 1 to 14, characterized in that the heating device ( 30 ) comprises a heating device operated with a heat transfer medium and additional at least in individual areas along the flow channels ( 22 ) in the sense of an additional heating also comprises an electric heating device. 16. Process for heating and / or evaporating liquid media under Use of a device according to one of the claims 1 to 15, in which the medium to be heated and / or evaporated is a or several flow channels of at least one flow device flows through and at least one heating device for Providing thermal energy with the at least one flow device is connected in the sense of a heat exchanger, heated and / or is evaporated characterized, that the heating device for influencing the surface temperature in the flow channels in the flow direction of the medium at least in  individual areas under independently adjustable operating areas conditions is operated. 17. The method according to claim 16, characterized, that the electrical heating device with different areas electrical power is operated. 18. The method according to claim 16, characterized, that the heating device operated with a heat transfer medium in some areas with different temperatures and / or with below of different flow velocities in the respective inlet opening of the Flow channels is guided. 19. The method according to claim 16, characterized, that the surface temperature in the flow channels through the heated with a heat transfer medium heated device are set in some areas by an additional electrical heater. 20. Use of a device according to one of claims 1 to 15 and / or of a method according to one of claims 16 to 19 for heating and / or Vaporizing a fuel and / or a fuel.