Evaporation cooling system comprising at least one heat exchanger for fuel cell system, and fuel cell system comprising such evaporation cooling system and use of such fuel cell system for vehicle

Abstract

To enable use of fuel cell water for a fuel cell cooling heat exchanger and at least reduce corrosion of the heat exchanger when supply fluid is supplied.SOLUTION: An evaporation cooling system comprises at least one heat exchanger for a fuel cell system. The evaporation cooling system includes a closed cooling circuit inside which coolant for cooling a fuel cell circulates. Inside the closed cooling circuit, at least one heat exchanger for cooling the coolant is in fluid connection. The evaporation cooling system includes a supply device inside which supply fluid for cooling the heat exchanger flows. The supply fluid is water discharged from the fuel cell. The heat exchanger includes a cooling tube having a core. The core of the cooling tube of the at least one heat exchanger is composed of aluminum alloy and contains an anti-corrosion component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an evaporative cooling system with at least one heat exchanger for a fuel cell system, a fuel cell system with such an evaporative cooling system and the use of such a fuel cell system in a motor vehicle according to the preambles of the independent claims.

[0002] In fuel cells, the chemical reaction that takes place when hydrogen reacts with oxygen generates waste heat, necessitating system cooling. However, cooling circuits for fuel cells, or cooling circuits in fuel cell-powered vehicles, are significantly different from conventional cooling circuits in vehicles with internal combustion engines. In particular, in internal combustion engines, a large portion of the waste heat is dissipated via the exhaust gases, and the maximum allowable coolant temperature is typically approximately 90°C to 100°C. In contrast, in fuel cell-powered vehicles, only a very small portion of the waste heat, typically only about 5% of the waste heat, is dissipated via the exhaust gases, and the maximum allowable coolant temperature is often not allowed to exceed approximately 60°C to 80°C, depending on the exact fuel cell system. This is because otherwise the fuel cell would be damaged. This means, on the one hand, that the temperature difference between the coolant and, for example, the ambient air, is smaller in fuel cell-powered vehicles than in internal combustion engines, which makes heat transfer with high power density more difficult, and, on the other hand, that a greater amount of heat power must be dissipated. Therefore, a high power system is needed to remove the heat absorbed from the fuel cell by the coolant.

[0003] In configurations known from the prior art, the cooling power of the heat exchanger can be significantly increased by sparging with a sparging fluid. Such a sparging system is described, for example, in DE 10 2020 208 710 A1.

[0004] However, to avoid the need to prepare larger tanks for the fluid, it seems important to use the water discharged from the fuel cell as the supply fluid for the heat exchanger. Hereinafter, this water formed in the fuel cell will also be referred to as "fuel cell water." Fuel cell water is extremely pure water with a very low conductivity, for example, less than 200 μS / cm or even less than 10 μS / cm. When fuel cell water comes into contact with air, CO2 present in the air dissolves in the fuel cell water, forming carbonic acid, which oxidizes the fuel cell water. A pH value of approximately 4 to 5 is typically found. Therefore, fuel cell water has a strong corrosive effect on metal surfaces, due in part to its pH value and also to the fact that it is deionized water.

[0005] Against this background, the problem underlying the present invention is to provide an innovation in the development of evaporative cooling systems that allows the use of fuel cell water in the supply system while at the same time at least reducing corrosion of the heat exchanger when supplied with a supply fluid.

[0006] This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0007] According to the present invention, there is provided an evaporative cooling system for a fuel cell system, comprising at least one heat exchanger, the system comprising: - The evaporative cooling system has a closed cooling circuit in which a refrigerant circulates to cool the fuel cell, - in a closed cooling circuit, at least one heat exchanger for cooling a refrigerant is fluidly connected, - at least one heat exchanger has cooling tubes; - at least one heat exchanger can be circulated by air from an air inlet face to an air outlet face and by a refrigerant through cooling tubes; - the evaporative cooling system has a supply device through which a supply fluid flows for cooling at least one heat exchanger; the supply device has an outlet opening for the supply fluid, through which the supply fluid is supplied to the cooling tubes of the at least one heat exchanger; In evaporative cooling systems, - the supply fluid is water discharged from the fuel cell; - the cooling tube of the at least one heat exchanger has a core, and the core of the cooling tube of the at least one heat exchanger is made of a first aluminum alloy, the first aluminum alloy including a minimum of about 0.0 wt. % and a maximum of about 1.0 wt. % Si, a minimum of about 0.5 wt. % and a maximum of about 2.0 wt. % Mn, a minimum of about 0.3 wt. % and a maximum of about 1.0 wt. % Cu, a minimum of about 0.0 wt. % and a maximum of about 0.6 wt. % Fe, a minimum of about 0.0 wt. % and a maximum of about 0.2 wt. % Ti, a minimum of about 0.0 wt. % and a maximum of about 0.5 wt. % Mg, a minimum of about 0.0 wt. % and a maximum of about 0.5 wt. % Zn, and less than 0.05 wt. % other elements; It is specified to provide an evaporative cooling system characterized by:

[0008] The evaporative cooling system of the present invention, which has the features of independent claim 1, has the important advantage of being able to effectively dissipate the heat generated by the fuel cell, thereby effectively avoiding a reduction in output or damage to the fuel cell.

[0009] Another important advantage of the evaporative cooling system of the present invention is that it avoids the need for a larger space or increased weight of the cooling system. Alternatively, a greater cooling output could be achieved by using a larger air volume when cooling the refrigerant with air, but this would require a larger heat exchanger, which would increase its size and weight. Furthermore, legal regulations for pedestrian protection prohibit the construction of arbitrarily large heat exchangers for automobiles. The evaporative cooling system of the present invention also makes it possible to use the fuel cell water that is generated in any case in a fuel cell-powered automobile. This avoids the need to install an additional tank for water supply, for example.

[0010] Furthermore, an important advantage of the present invention is that, due to the aluminum alloy selected for the cooling tube core according to the present invention, pretreatment of the fuel cell water, such as neutralization and addition of a controlled ion load, is not required to reduce the corrosive effect of the fuel cell water. Furthermore, passivation of the cooler with a passivating solution before the first operation is also not required. This saves materials, space, and costs.

[0011] In this connection, it is also advantageous that the present invention allows the useful life of at least one heat exchanger to be significantly extended with respect to conventional systems, thereby avoiding replacement costs.

[0012] This is particularly achieved according to the present invention by using water discharged from a fuel cell (fuel cell water) to supply at least one heat exchanger, the cooling tubes of the at least one heat exchanger having a core, the core of the cooling tube of the at least one heat exchanger being made of a first aluminum alloy, the first aluminum alloy containing a minimum of about 0.0 wt. % and a maximum of about 1.0 wt. % Si, a minimum of about 0.5 wt. % and a maximum of about 2.0 wt. % Mn, a minimum of about 0.3 wt. % and a maximum of about 1.0 wt. % Cu, a minimum of about 0.0 wt. % and a maximum of about 0.6 wt. % Fe, a minimum of about 0.0 wt. % and a maximum of about 0.2 wt. % Ti, a minimum of about 0.0 wt. % and a maximum of about 0.5 wt. % Mg, a minimum of about 0.0 wt. % and a maximum of about 0.5 wt. % Zn, and less than 0.05 wt. % other elements.

[0013] By means of the composition according to the invention of the core of the cooling tubes of the heat exchanger, protection against corrosion caused by fuel cell water is achieved.

[0014] In the following, an evaporative cooling system with at least one heat exchanger for a fuel cell system, a fuel cell system with such an evaporative cooling system, and the use of such a fuel cell system in a motor vehicle are described in more detail. The figures used within the framework of and in connection with the description of the evaporative cooling system according to the invention are likewise reasonably applicable to the figures used in connection with and for the use of a fuel cell system, and vice versa.

[0015] The present invention is based on the general idea of ​​providing a cooling system that can effectively dissipate the heat generated in a fuel cell, while at the same time requiring relatively little space and having good corrosion resistance.

[0016] The cooling system has a closed cooling circuit in which a coolant for cooling the fuel cell circulates. A closed cooling circuit means that the coolant is not removed during operation and no other coolant is added to the cooling circuit. However, it is possible to replace the coolant at regular maintenance intervals, for example once or twice a year, and this is excluded.

[0017] The refrigerant may be essentially any refrigerant commonly used for cooling in automobiles, particularly fuel cell-powered automobiles. For example, the refrigerant may be a refrigerant mixture containing water and monoethylene glycol. Such refrigerant mixtures may contain small proportions of auxiliary substances, such as silicates or organic acids. In particular, such refrigerant mixtures may contain less than 2% by weight of each auxiliary substance.

[0018] For example, it is conceivable to use a refrigerant mixture consisting of Glisantin® concentrate and water. Typically, depending on, for example, the ambient temperature and the selected Glisantin® concentrate (e.g., Glisantin® G30® or Glisantin® G40®), a minimum of about 30% by volume to a maximum of about 60% by volume of Glisantin® concentrate and a maximum of about 70% by volume to a minimum of about 40% by volume of water are mixed together to obtain the refrigerant mixture. Of course, it is clear that the total percentages by volume must add up to 100% by volume. Alternatively, it is possible to use a product that has already been premixed by the manufacturer, such as a Glisantin® Ready Mix product.

[0019] Furthermore, at least one heat exchanger for cooling the refrigerant is fluidly connected within the closed cooling circuit. The at least one heat exchanger has cooling tubes through which the refrigerant can flow and which serve to cool the refrigerant or to release heat previously absorbed by the refrigerant. The cooling tubes may be configured, for example, as elliptical, flattened, or circular tubes. In this context, an elliptical tube refers to a tube having an elliptical or approximately elliptical cross section. It is also conceivable that the cooling tubes at least partially have turbulators that can serve to induce vortex flow in the refrigerant. Such heat exchangers are well known to those skilled in the art, and it is equally well known to those skilled in the art that the size of the heat exchanger and, for example, the number of tubes, depend on various factors, such as the required cooling power or total surface area of ​​the heat exchanger.

[0020] At least one heat exchanger is passable by air from the air inlet face to the air outlet face, and therefore the cooling tubes are typically spaced apart from one another to allow air to flow therethrough.

[0021] It has proven to be practical if the cooling tubes are further provided with fins, for example corrugated fins, which are spaced apart so that they can also be circulated by air and further improve heat dissipation. The use of fins in heat exchangers is also well known to those skilled in the art. The fins may comprise, for example, a metal or alloy. Alternatively, the fins may consist of, for example, a metal or alloy, in particular, the fins may consist of an aluminum alloy.

[0022] The at least one heat exchanger preferably has at least one tube bottom, particularly preferably two tube bottoms, which are connected to the cooling tubes, for example, by brazing or gluing. The use of tube bottoms in heat exchangers is well known to those skilled in the art. The at least one tube bottom may, for example, comprise a metal or alloy. Alternatively, the at least one tube bottom may, for example, consist of a metal or alloy. In particular, the at least one tube bottom may consist of an aluminum alloy.

[0023] Furthermore, the closed cooling circuit advantageously has at least one refrigerant container to which the cooling pipes are fluidly connected via at least one pipe bottom, and preferably the closed cooling circuit has two refrigerant containers to which the cooling pipes are fluidly connected via two pipe bottoms.

[0024] The coolant container may be configured, for example, in the shape of a box. For example, the coolant container may be configured as both a collection container for collecting the coolant from the cooling pipes and a distribution container for distributing the coolant to the cooling pipes. In such a configuration, the coolant flows from the distribution container to the collection container, and the coolant flows in the same direction in all of the cooling pipes. Alternatively, for example, the coolant container may be configured as both a collection and distribution container and a redirection container. In such a configuration, the coolant flows from the collection and distribution container through some of the cooling pipes toward the redirection container, where it is redirected and flows back from the redirection container through the remaining pipes toward the collection and distribution container. The coolant container is further connected to the fuel cell via another pipe so that heat generated in the fuel cell can be dissipated via the coolant.

[0025] The collection or distribution container may comprise, for example, a plastic. In this regard, it is clear that the selection of a suitable plastic depends on the application conditions. Considerations should be taken into account, for example, the melting temperature of the respective plastic or its chemical resistance to the selected refrigerant. Examples of suitable plastics include polypropylene and polypropylene blends, polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polyamide (PA), and polyoxymethylene (POM). Furthermore, the plastic may contain fillers and reinforcing agents. Examples of fillers for thermoplastics include glass beads, glass fibers, mineral fillers such as talc, carbon fibers, and carbon black. In particular, glass or carbon fibers can also serve as reinforcement in this context. Furthermore, the plastic may contain additives such as stabilizers and impact modifiers. For example, glass-fiber-reinforced polyamides PAGF30 and PA6 GF35 are advantageously suitable.

[0026] According to the invention, the evaporative cooling system further comprises a supply device through which a supply fluid flows for cooling the at least one heat exchanger. The supply device has, for example, passages forming a distribution grid. Alternatively, the supply device can also comprise an atomizing device. A supply device with an atomizing device is described, for example, in DE 10 202 2 202 648 A1.

[0027] If the supply device has a passageway, it is conceivable that the passageway comprises a metal, alloy, or plastic, or alternatively, the passageway may consist of a metal, alloy, or plastic. Particularly preferably, the passageway consists of a flexible tube or flexible tubes fluidly connected to one another. In this context, the passageway may consist of a plastic, such as plasticizer-free polyvinyl chloride (PVC-U) or polyethylene (PE). The passageway may be fixed to the at least one heat exchanger, for example, via a holding device. For example, the passageway may be fixed to the at least one heat exchanger by two holding devices, each of which may have multiple fixing possibilities.

[0028] To be able to supply the supply fluid, the supply device has an outlet opening, such as an outlet nozzle or an outlet hole, whereby the supply fluid can be supplied to the supply device via a line that is fluidly connected to the supply device.

[0029] The supply device is an open system. That is, the supply fluid is extracted from the supply device for cooling, and the supply device must be constantly replenished with new supply fluid from the outside. The supply is effected via outlet openings, e.g., outlet nozzles or outlet holes. For example, a channel structure with a plurality of channels forming a supply grid is fluidly connected to the supply device. The channel structure is arranged parallel to and immediately adjacent to the air inlet face of at least one heat exchanger, and each channel typically has a plurality of outlet openings. The spray fluid can be supplied to the cooling tubes of at least one heat exchanger through the outlet openings.

[0030] During the supply of the supply fluid to the cooling tubes of the at least one heat exchanger, the at least one heat exchanger is passed by air from its air inlet face to its air outlet face. That is, the air inlet face is advantageously arranged upstream of the air outlet face in the direction of travel when the cooling system is installed in a motor vehicle. In this arrangement, the at least one heat exchanger can be passed by the driving wind, so that droplets of the supply fluid emerging from the outlet opening of the supply device are also carried into the at least one heat exchanger. This results in a particularly effective supply of the supply fluid to the cooling tubes of the at least one heat exchanger. The combination of cooling by the driving wind and cooling by the supply results in particularly effective cooling.

[0031] According to the invention, fuel cell water is used as the supply fluid. For example, it is conceivable to bring the fuel cell water directly from the fuel cell into the supply device. This can be done by a pipe connecting the fuel cell and the supply device. Alternatively, it is conceivable, for example, to guide the fuel cell water through one or more additional structural units before entering the supply device. For example, it is conceivable to guide the fuel cell water through an additional temperature regulation unit.

[0032] Furthermore, it is also conceivable, for example, for a pumping device, such as a gear pump, to be arranged between the fuel cell and the supply device, which would be appropriate, for example, if the fuel cell is arranged below the supply device in relation to the direction of gravity during operation of the fuel cell system.

[0033] According to the present invention, at least one heat exchanger cooling tube has a core, and the core of the at least one heat exchanger cooling tube is made of a first aluminum alloy, the first aluminum alloy containing a minimum of about 0.0 wt % and a maximum of about 1.0 wt % Si, a minimum of about 0.5 wt % and a maximum of about 2.0 wt % Mn, a minimum of about 0.3 wt % and a maximum of about 1.0 wt % Cu, a minimum of about 0.0 wt % and a maximum of about 0.6 wt % Fe, a minimum of about 0.0 wt % and a maximum of about 0.2 wt % Ti, a minimum of about 0.0 wt % and a maximum of about 0.5 wt % Mg, a minimum of about 0.0 wt % and a maximum of about 0.5 wt % Zn, and less than 0.05 wt % of other elements.

[0034] This ensures that the at least one heat exchanger to which it is supplied has good corrosion resistance against corrosion caused by fuel cell water.

[0035] In this context, the core of the cooling tube refers to the tube material on the side facing the coolant. Of course, it is clear that the cooling tube can be circulated with coolant through its interior. The supply side corresponds to the side opposite the inside, which is in contact with the supply fluid.

[0036] A magnesium proportion that is as small as possible leads to improved brazing possibilities.

[0037] An aluminum alloy is an alloy in which aluminum serves as the base material and other alloying elements are added to the aluminum to affect the material properties of the resulting alloy. Therefore, those skilled in the art will recognize that the primary component of an aluminum alloy is aluminum, with all components totaling 100% by weight. Furthermore, those skilled in the art will recognize that such alloys typically contain minor percentages of other elements depending on the starting materials and manufacturing process. For example, but not by way of limitation, such impurities may be minor percentages of Ga, O, Bi, or V.

[0038] Typically, the components of such aluminum alloys can be identified by chemical analysis. A standard method for chemical analysis of aluminum alloys, which can also be used for the analysis of materials of interest, is optical optical emission spectroscopy, which can be either spark discharge optical emission spectroscopy (spark OES) or glow discharge optical emission spectroscopy (GDOES).

[0039] Furthermore, it has proven advantageous if the cooling tubes of at least one heat exchanger have a wall thickness of at least about 0.20 mm and at most about 0.50 mm, which allows for good heat transfer and at the same time good stability.

[0040] Additionally, it is also conceivable to further improve the corrosion resistance by means of a surface plating or coating.

[0041] In this context, it has proven advantageous if the cooling tube core has at least one first plating layer on the supply side. In particular, it has proven advantageous if the at least one first plating layer consists of a second aluminum alloy containing at least about 6.8% by weight and at most about 12.0% by weight of Si, at least about 0.0% by weight and at most about 0.8% by weight of Fe, at least about 0.0% by weight and at most about 0.25% by weight of Cu, at least about 0.5% by weight and at most about 3.5% by weight of Zn, and less than 0.05% by weight of other elements. A low iron content and a suitable tin content have proven effective in preventing pitting corrosion.

[0042] The plating of metals or aluminum or aluminum alloys is known from the prior art. Basically, all conventional methods for plating aluminum or aluminum alloys are conceivable. For example, plating can be carried out by rolling thin metal foils, welding, ion plating, immersion plating, explosive plating or electroplating. Plating by rolling (roll plating) has proven to be particularly advantageous. In this case, a material prepared for plating can be placed on the material to be plated, and both materials can be heated and rolled under pressure.

[0043] Furthermore, at least one first coating layer is made of a second aluminum alloy, which is in a semi-hardened, non-homogenized heat-treated annealed state. Those skilled in the art will appreciate that heat treatment of an alloy affects its material properties. Heat treatment designations for aluminum alloys can be found in standard data sheets.

[0044] In a further preferred embodiment, at least one heat exchanger has fins, the fins preferably having a thickness of about 0.05 mm minimum to 0.20 mm maximum.

[0045] It is further proven reasonable that the fins of the at least one heat exchanger are comprised of a third aluminum alloy, the third aluminum alloy containing a minimum of about 0.5 wt.% to a maximum of about 2.0 wt.% Si, a minimum of about 0.3 wt.% to a maximum of about 2.0 wt.% Mn, a minimum of about 0.3 wt.% to a maximum of about 2.0 wt.% Cu, a minimum of about 0.0 wt.% to a maximum of about 0.7 wt.% Fe, a minimum of about 0.0 wt.% to a maximum of about 0.1 wt.% Mg, a minimum of about 1.0 wt.% to a maximum of about 2.0 wt.% Zn, and less than 0.05 wt.% other elements.

[0046] More preferably, the at least one heat exchanger further has at least one bottom, preferably two bottoms, and the at least one bottom preferably has a thickness of at least about 0.5 mm to at most about 3 mm.

[0047] Furthermore, it has proven advantageous if at least one bottom has a core or if at least one bottom has a core and also has at least one second plating, at least on the supply side.

[0048] In particular, it has been proven reasonable that at least one bottom has a core, the core of the at least one bottom being made of a fourth aluminum alloy, the fourth aluminum alloy including a minimum of about 0.0 wt. % and a maximum of about 1.0 wt. % Si, a minimum of about 0.5 wt. % and a maximum of about 2.0 wt. % Mn, a minimum of about 0.3 wt. % and a maximum of about 1.0 wt. % Cu, a minimum of about 0.0 wt. % and a maximum of about 0.7 wt. % Fe, a minimum of about 0.0 wt. % and a maximum of about 0.2 wt. % Ti, a minimum of about 0.0 wt. % and a maximum of about 0.5 wt. % Mg, a minimum of about 0.0 wt. % and a maximum of about 0.5 wt. % Zn, and less than 0.05 wt. % other elements.

[0049] Alternatively, it has proven advantageous if the at least one bottom has a core, and the at least one bottom further has at least one second plating at least on the feed side, the at least one second plating consisting of a fifth aluminum alloy, the fifth aluminum alloy containing a minimum of about 6.8 wt.% to a maximum of about 12.0 wt.% Si, a minimum of about 0.0 wt.% to a maximum of about 0.8 wt.% Fe, a minimum of about 0.0 wt.% to a maximum of about 0.25 wt.% Cu, a minimum of about 0.0 wt.% to a maximum of about 0.5 wt.% Zn, and less than 0.05 wt.% other elements.

[0050] Further alternatively, at least one bottom has a core, and the at least one bottom further has at least one second plating on at least the feed side, the bottom core being made of a fourth aluminum alloy, the fourth aluminum alloy having a minimum of about 0.0 wt % to a maximum of about 1.0 wt % Si, a minimum of about 0.5 wt % to a maximum of about 2.0 wt % Mn, a minimum of about 0.3 wt % to a maximum of about 1.0 wt % Cu, a minimum of about 0.0 wt % to a maximum of about 0.7 wt % Fe, a minimum of about 0.0 wt % to a maximum of about 0.2 wt % Ti, a minimum of about 0 wt % to a maximum of about 0.5 wt % Mn, g, a minimum of about 0.0 wt. % to a maximum of about 0.5 wt. % Zn, and less than 0.05 wt. % other elements, and the at least one second plating is comprised of a fifth aluminum alloy containing a minimum of about 6.8 wt. % to a maximum of about 12.0 wt. % Si, a minimum of about 0.0 wt. % to a maximum of about 0.8 wt. % Fe, a minimum of about 0.0 wt. % to a maximum of about 0.25 wt. % Cu, a minimum of about 0.0 wt. % to a maximum of about 0.5 wt. % Zn, and less than 0.05 wt. % other elements has proven particularly advantageous.

[0051] Additionally, at least one heat exchanger of the evaporative cooling system comprises: a) preparing a heat exchanger to be inspected, optionally together with a supply device fixed to the heat exchanger; b) optionally providing a feeding device; c) optionally, fixing the supply device to the heat exchanger to be tested; d) placing the heat exchanger to be tested and the supply device in a climate chamber, the climate chamber being equipped with a device for generating an air flow, the climate chamber being thermostated at approximately 35°C, the surface to be supplied being arranged at an angle α to the vertical, the angle α having a value of approximately 20°; e) attenuating the heat exchanger to be tested to a heat exchanger temperature of about 85°C, the attenuation being achieved via a refrigerant guided through the tubes of the heat exchanger; f) supplying a feed fluid to the heat exchanger to be tested while simultaneously passing an air flow through the heat exchanger for about 10 seconds, the air flow being about 25 g / (s *m 2 ), wherein the feed fluid is deionized water, and the deionized water has a conductivity of less than 10 μS / cm; g) at least partially drying the heat exchanger to be inspected by passing an air flow through it for about 30 seconds, the climate chamber having a relative air humidity of at least about 35% and at most about 65% during step g), and repeating steps f) and g) alternately about 180,000 times, the air flow having an average air velocity of at least about 2 m / s and at most about 3 m / s during steps f) and g); h) removing the heat exchangers and feeders to be inspected from the weather chamber, wherein at least one heat exchanger has a minimum remaining wall thickness of about 100 μm after treatment of all tubes. It has proven advantageous that the cellulose is suitable for being subjected to a treatment comprising

[0052] The process according to steps a) to h) serves to simulate corrosion that may occur during operation. Essentially, during operation, an evaporative cooling system always supplies coolant when the cooling output of a conventional cooling system without supply is insufficient, i.e., when the inherently permissible refrigerant temperature is exceeded. At an ambient temperature of 25°C, this corresponds, for example, to approximately 22% of the running time. Of course, this also depends on various factors, such as the outside air temperature and speed. The selected conditions are therefore suitable for reliably and reproducibly simulating the corrosion behavior of an evaporative cooling system during operation. It has been shown that corrosion behavior in a thinning, drying water film can be particularly well simulated, as demonstrated here by the alternating supply and drying phases. The corrosion process is particularly accelerated by a thin water film, since the atmospheric oxygen involved in corrosion can reach the component surface very close (via diffusion processes). Therefore, for corrosion testing, it is particularly advantageous to completely dry the water film. Furthermore, in a thinning water film, salts dissolved in the water may become concentrated. This process will be explained in more detail below.

[0053] First, in step a), a heat exchanger whose corrosion properties it is desired to test is prepared. If the heat exchanger is already prepared and configured with a supply device typically desired for use in an evaporative cooling system, the additional preparation of the supply device in step b) and the fixing of the supply device to the heat exchanger in step c) are of course omitted, as will be explained in more detail below.

[0054] If the heat exchanger is prepared without a feed device in step a), then in optional step b), which may be performed subsequent to or parallel to step a), a feed device is prepared. The feed device is reasonably the feed device that is also desired to be used during operation of the respective evaporative cooling system. However, alternatively, any feed device that serves the purpose of supplying the heat exchanger with a feed fluid during corrosion testing may be used.

[0055] Following optional step b), in optional step c) the supply device is fixed to the heat exchanger in such a way that it can reliably supply the heat exchanger with supply fluid for the entire duration of the supply to be carried out.

[0056] In step c) or step a) followed by step d), the heat exchanger with the supply device is inserted into the weather chamber. It is clear that the supply device must be connected to at least one supply line for the supply fluid, so that the supply fluid can be continuously routed through the supply device during the supply. The supply line can be connected to the supply device, for example, via a quick coupling.

[0057] The heat exchanger with the supply device is installed in the weather chamber so that the surface to be supplied is inclined in the direction of the air flow, and the surface to be supplied is arranged at an angle α to the vertical, the angle α having a value of approximately 20°.

[0058] A weather chamber is a specific device, which, on the one hand, has temperature-regulating interiors and, on the other hand, has supply and discharge ports for air, a supply fluid and, optionally, a coolant, and, optionally, a connection for an electric heating device, by means of which, for example, a desired temperature of the weather chamber or heat exchanger can be adjusted or a desired relative air humidity can be set. It is clear, of course, that the weather chamber also has corresponding devices for measuring the temperature and relative air humidity. The dimensions of the weather chamber are reasonably selected so that the entire heat exchanger, including the supply device, can be installed in the weather chamber.

[0059] The weather chamber further comprises a device for generating an air flow, for example a heatable blower. Depending on the design and in particular the dimensions of the weather chamber, it is conceivable that the device for generating an air flow is located outside the weather chamber, and that the weather chamber has an air supply line through which the generated air flow can be led into the weather chamber. Alternatively, it is also conceivable that the device for generating an air flow is located inside the weather chamber.

[0060] The climate chamber is thermostated at approximately 35°C, which allows testing under reproducible conditions.

[0061] In step e), the heat exchanger is then thermostated to a heat exchanger temperature of approximately 85°C. The thermostation serves to simulate operation with a heated coolant, for example, which extracts waste heat from the fuel cell. In some cases, the climate chamber itself must be cooled to keep the temperature constant at approximately 35°C, since, for example, a heated heat exchanger to be tested can be a source of energy input. Cooling of the climate chamber can be achieved, for example, by supplying and mixing fresh air.

[0062] The temperature regulation is achieved by connecting the heat exchanger to a refrigerant circuit through which a correspondingly temperature-regulated refrigerant, heated, for example, outside the climate chamber, is led through the heat exchanger. Such a refrigerant may be, for example, a refrigerant mixture comprising water and monoethylene glycol. The temperature regulation of the heat exchanger is maintained during steps f) and g) described below.

[0063] Once the heat exchanger is brought to the desired heat exchanger temperature of about 85°C in step e), a feed fluid is fed to the heat exchanger in step f). The feed fluid is deionized water, which has a conductivity of less than 10 μS / cm. The deionized water can be obtained, for example, by a mixed-bed ion exchanger, distillation, or reverse osmosis. This allows for particularly good simulation of the fuel cell water chemistry.

[0064] The measurement of conductivity is well known to those skilled in the art. It is based on the determination of ohmic resistance. Conductivity typically serves as a measure for the total amount of dissolved ions in water.

[0065] The supply fluid is supplied to the heat exchanger, for example, via outlet openings provided in the supply device. It is reasonable to wet at least about 70%, more preferably at least about 80%, of the surface area of ​​the heat exchanger. However, this will, of course, depend on the total surface area of ​​the test specimen to be tested. Furthermore, it is advantageous for at least about 85% of the outlet openings to remain functional during the entire test. That is, it is advantageous for less than about 15% of the outlet openings to become blocked or otherwise malfunction, for example, during the test.

[0066] At the same time, the heat exchanger to be tested is passed by an air flow, which is generated, for example, by the heatable fan mentioned above and preferably has a temperature of about 35° C. The air flow can also be used to temperature-condition the climate chamber, for example, to about 35° C., if necessary, or can at least contribute to this.

[0067] The air flow can for example pass through the intermediate spaces between the cooling tubes or between the fins, and is advantageously directed towards the heat exchanger in such a way that the droplets of feed fluid emitted from the feed device are carried towards the heat exchanger by the air flow.

[0068] The supply fluid and air flow are performed simultaneously for approximately 10 seconds.

[0069] The supply of the feed fluid is then stopped and in step g) the heat exchanger to be tested is further at least partially dried with a flow of air for about 30 seconds, in this connection it should be noted that for the drying step only the supply of the feed fluid is interrupted, however the air flow is continuously carried out during steps f) and g).

[0070] The incoming air flow preferably has a temperature of approximately 35°C when it enters the climate chamber. It is, of course, conceivable that the incoming air flow is heated as it passes through the heat exchanger to be tested. This means, for example, that the climate chamber itself may have to be cooled in order to maintain a constant temperature of approximately 35°C in the climate chamber. The cooling of the climate chamber can be achieved, for example, by adding fresh air. In this regard, it is, of course, also possible for the temperature of the incoming air flow to differ from a temperature of 35°C, particularly if this is necessary for temperature regulation of the climate chamber, for example, if the climate chamber would otherwise be overheated due to heat input by a heated heat exchanger.

[0071] Furthermore, it is reasonable to monitor the relative air humidity in the weather chamber and, in some cases, at least partially ventilate the weather chamber to reduce the relative air humidity, especially when it exceeds about 65% relative air humidity, with the caveat being that the relative air humidity should not be reduced below about 35%.

[0072] Steps f) and g) are alternately repeated approximately 180,000 times. After the final drying process, i.e., after the last execution of step g), the heat exchanger and the supply device are removed from the climate chamber in step h). A corrosion inspection is then carried out.

[0073] It is, of course, conceivable that the heat exchanger and supply device to be inspected may be removed from the climate chamber for a short time, for example for a visual inspection, during the repeated performance of steps f) and g), or the inspection process may be interrupted or paused for other reasons. This does not constitute a change in the inspection process, as long as steps f) and g) are performed for the determined full number of cycles and under the set conditions.

[0074] Basically, any inspection method is suitable, which can identify corrosion of metals or alloys. In particular, it is reasonable that the inspection method can distinguish between surface corrosion or recess corrosion and pit corrosion, and measure the depth of the corrosion layer. Particularly preferably, the inspection is carried out using an optical microscope. Typically, the wall thickness can be determined by making a cross section, thus making a cross section sample and then evaluating it under a microscope.

[0075] For example, elements, such as tubes, that conduct refrigerant during normal operation of the heat exchanger are removed from the heat exchanger, cleaned of corrosion products and deposits, and the depth of corrosion is then measured using an optical microscope. The type of corrosion (pit, recess, or surface corrosion) can be examined by metallographic examination using an optical microscope.

[0076] If high magnification is required, the use of a scanning electron microscope is also conceivable, for example, alternatively or additionally.

[0077] In particular, the heat exchanger to be inspected preferably has a minimum remaining wall thickness of about 100 μm for all tubes after the above-described treatment including steps a) to h). This is reasonable, in particular, because, for example, light surface corrosion may not be a problem, but pitting corrosion will almost always force leakage. Alternatively, it is advantageous if the heat exchanger to be inspected does not have pitting corrosion for all tubes after the above-described treatment including steps a) to h), and the minimum remaining wall thickness of all elements of the heat exchanger is not less than 50% of the starting wall thickness.

[0078] It is understood that the minimum remaining wall thickness of a tube refers to the wall thickness of the corresponding tube at its thinnest point after the method for testing corrosion properties has been carried out. The starting wall thickness refers to the wall thickness before corrosion.

[0079] In this context, recess corrosion or surface corrosion refers to corrosion that occurs in a planar manner over most or all of the surface, but does not form deep, point-like structures. Conversely, pit corrosion, also called pit corrosion, refers to corrosion in which, for example, point-like holes form on the surface of a material, and these holes do not extend across the surface at all, but may extend significantly in depth, for example, in the form of grooves. Therefore, within the scope of this application, pit corrosion is defined to exist when the depth of the corrosion-formed hole measured at its deepest point divided by the width of the hole measured at its widest point on the surface is 1 or greater.

[0080] Correspondingly, recess corrosion or surface corrosion refers to a situation where the depth of a corrosion hole measured at its deepest point divided by the width of the corrosion hole measured at its widest point on the surface is less than 1. This indicates that the corrosion is surface-wide and only slightly deep. Surface corrosion damage can be identified, for example, by comparing it with a reference grinding on an uncorroded pipe. Surface corrosion usually does not cause leakage unless it exceeds a certain depth or falls below a certain remaining wall thickness. This means that surface corrosion is usually within the acceptable range as long as it does not fall below a remaining wall thickness of 100 μm.

[0081] This also means that, excluding the presence of pitting corrosion, the material is free of pits where the depth measured at the deepest point divided by the width measured at the widest point of the pit at the surface is equal to or greater than 1.

[0082] Alternatively, at least one heat exchanger of the evaporative cooling system comprises: a) providing at least a portion of a heat exchanger to be inspected; b) optionally providing a feeding device; c) optionally fixing a supply device to at least a portion of the heat exchanger to be inspected; d) placing at least part of the heat exchanger to be inspected and the supply device in a weather chamber, the weather chamber being configured with a device for generating an air flow, the surface to be supplied being arranged at an angle α to the vertical, the angle α having a value of approximately 20°; e) thermostating the climate chamber to a climate chamber temperature of approximately 35°C and thermostating at least a portion of the heat exchanger to be tested to a heat exchanger temperature of approximately 85°C, the thermostating being carried out by heating via heat conduction by a heating device, in particular by electrical heating of the heating device; f) supplying a feed fluid to at least a portion of the heat exchanger to be tested and simultaneously supplying an air flow to at least a portion of the heat exchanger to be tested for about 10 seconds, * m 2 ), wherein the feed fluid is deionized water, and the deionized water has a conductivity of less than 10 μS / cm; g) at least partially drying at least a portion of the heat exchanger to be inspected by supplying an air flow for about 30 seconds to at least a portion of the heat exchanger to be inspected, the climate chamber having a relative air humidity of at least about 35% and at most about 65% during step g), the air flow having an average air flow velocity of at least about 2 m / s and at most about 3 m / s in steps f) and g), and repeating steps f) and g) alternately about 180,000 times; h) removing at least a portion of the heat exchanger to be inspected and the supply device from the climate chamber, wherein at least one heat exchanger has a minimum remaining wall thickness of about 100 μm after treatment of all tubes. It has been found to be advantageously suitable for being subjected to a treatment comprising

[0083] In this context, at least a part of the heat exchanger to be inspected means that, depending on the dimensions of the heat exchanger to be inspected, it may be reasonable to prepare the entire heat exchanger or, alternatively, to prepare only a part of the heat exchanger, which can be achieved by cutting out a representative part from the heat exchanger, i.e., at least the elements that conduct the refrigerant during normal operation of the heat exchanger, such as the cooling tubes, or, for example, additionally a part of the tube bases, for example by means of a metal saw.

[0084] For this embodiment, there is also the possibility of inspecting only a portion of the heat exchanger for corrosion, in particular because the adjustment of the temperature of at least the portion of the heat exchanger to be inspected to the heat exchanger temperature is carried out by heating via heat conduction by a heating device, in particular by electrical heating of the heating device. This heating device can be, for example, a heating mat or an electrically heatable wire that can be fixed to the heat exchanger by wrapping it around the cooling pipes. This makes it unnecessary to prepare the entire system of closed cooling pipes for inspection.

[0085] It is further apparent that heating via a heating device in the form of a heating mat, which is typically positioned on the opposite side of the heat exchanger to the air flow that contacts it, may result in the air not flowing completely through the heat exchanger, but possibly being redirected by the heating mat.

[0086] For the implementation of steps a) to h), what has already been said otherwise applies.

[0087] The invention further relates to a fuel cell system equipped with such an evaporative cooling system, the fuel cell system having at least one fuel cell which discharges fuel cell water during operation.

[0088] Furthermore, the invention also relates to the use of such a fuel cell system in a motor vehicle.

[0089] Further important features and advantages of the invention are set out in the dependent claims, the drawings and the accompanying description of the drawings.

[0090] It is of course clear that the features mentioned above and further described below cannot be used only in the respective given combinations, but can also be used in other combinations or independently, without departing from the scope of the invention. [Brief explanation of the drawings]

[0091] [Figure 1]FIG. 1 is a front view illustrating one embodiment of an evaporative cooling system. [Figure 2] FIG. 1 is a simplified plan view of this embodiment of an evaporative cooling system. [Figure 3] FIG. 1 is a schematic diagram of a portion of an apparatus for determining corrosion characteristics of a heat exchanger in an evaporative cooling system for a fuel cell system.

[0092] FIG. 1 shows a front view of one possible embodiment of an evaporative cooling system 100. FIG. 2 shows the system in a corresponding plan view from above. The evaporative cooling system 100 is intended for use in a fuel cell system in a motor vehicle. The evaporative cooling system 100 comprises a closed cooling circuit 101 with a heat exchanger 102. In FIGS. 1 and 2, the closed cooling circuit 101 is not further illustrated. It is clear that the closed cooling circuit 101 may also comprise other components, such as additional pipes, compensation vessels, pumps, valves, or sensors. The closed cooling circuit serves to cool the fuel cell. The heat exchanger 102 comprises refrigerant vessels 103a, 103b. Furthermore, the heat exchanger 102 comprises cooling tubes 105 and corrugated fins 106, which are alternately stacked one on top of the other. The corrugated fins 106 are connected to the cooling tubes 105, for example, by soldering or gluing. In FIGS. 1 and 2, the individual cooling tubes 105 are arranged in the form of a tube block 104. The cooling pipe 105 is circulated by a refrigerant and is fluidly connected on one side to the refrigerant container 103a via the pipe bottom 107a and to the refrigerant container 103b via the second pipe bottom 107b. In the embodiment shown in FIGS. 1 and 2, the refrigerant flows from one refrigerant container 103a to the other refrigerant container 103b. That is, in the illustrated embodiment, the refrigerant container 103a is a distribution container, and the refrigerant container 103b is a collection container. The heat exchanger 102 is circulated by air. The air flows into the heat exchanger 102 through the air inlet surface 108a. Ideally, the heat exchanger 102 is oriented approximately at the motor so that the running wind impinges on the air inlet surface 108a approximately perpendicularly. The air leaves the heat exchanger again on the opposite side through the air outlet surface 108b. This means that the refrigerant flowing through the cooling pipe 105 is cooled by the air. The evaporative cooling system 100 further includes a supply 109 through which a supply fluid 110 flows, which, according to the present invention, is water discharged from the fuel cell. The supply 109 serves to cool the refrigerant in addition to the air cooling described above.1 and 2, a channel structure 111 is shown in a simplified form, which includes a number of channels 112 with outlet nozzles 113 by means of which the feed fluid can be supplied to the cooling tubes 105 of the heat exchanger 102. In this connection, it is advantageous if the outlet nozzles 113 are arranged so that the outgoing feed fluid 110 can be entrained by the incoming air and brought into the heat exchanger 102. This allows for supplemental cooling, in particular by evaporation. The feed fluid 110 enters the channel structure 111 via distribution lines 114a, 114b. The supply of the feed fluid 110 from the fuel cell is not further illustrated in FIGS. 1 and 2. By continuously removing the feed fluid 110 from the supply device 109 via the outlet nozzles 113, the supply device 109 must simultaneously be continuously replenished with fresh feed fluid 110 from the fuel cell.

[0093] FIG. 3 shows a schematic diagram of a portion 200 of an apparatus for determining the corrosion characteristics of a heat exchanger in an evaporative cooling system for a fuel cell system. Incoming air 201 and outgoing air 202 are also shown. The incoming air and outgoing air are generated using a device for generating airflow. Furthermore, in the embodiment shown in FIG. 3, a test specimen (of the heat exchanger to be tested) is heated using a heated refrigerant. To this end, the test specimen has an inlet 203 for the refrigerant into the cooling / heating circuit of the test specimen and an outlet 204 for the refrigerant into the cooling / heating circuit of the test specimen. In addition to the embodiment shown in FIG. 3, configurations in which the inlet and outlet of the cooling / heating circuit of the test specimen are interchanged are of course also conceivable, i.e., the refrigerant can be passed either downward or upward. The refrigerant can be, for example, a refrigerant mixture containing water and monoethylene glycol, or, for example, a water-Glisantin® mixture. The test specimen 205, i.e., the heat exchanger to be tested, is shown in a highly simplified form in FIG. 3. The test specimen 205 is equipped with a supply device 206, through which a supply fluid 207, here deionized water, can be delivered to the surface to be tested. In the embodiment shown in Figure 3, the supply device is, for example, a flexible tube or a supply grid with passages made of flexible tubes fluidly connected to each other. Of course, other forms of supply device are also conceivable, such as, for example, a spraying device. The test specimen 205 is arranged so that the surface to be supplied is positioned at an angle α with respect to the vertical direction 208, where the angle α is assumed to be approximately 20°. [Explanation of symbols]

[0094] 100 Evaporative cooling system in one embodiment 101 Closed cooling circuit 102 Heat exchanger 103a,103b Refrigerant container 104 Pipe Block 105 Cooling pipe 106 Wave Fin 107a,107b Tube bottom 108a Air inlet surface 108b Air outlet surface 109 Feeding device 110 Supply fluid 111 Passage structure 112 Passage 113 Outlet nozzle 114a,114b Distribution pipe 200 Part of an apparatus for determining the corrosion characteristics of heat exchangers in evaporative cooling systems 201 Intake air 202 Outflow Air 203 Inlet of cooling / heating circuit for specimen 204 Specimen cooling / heating circuit outlet 205 test specimens 206 Feeding device 207 Supply fluid 208 Vertical α Angle between the test piece surface to be fed and the vertical direction

Claims

1. 1. An evaporative cooling system for a fuel cell system, comprising at least one heat exchanger, the evaporative cooling system has a closed cooling circuit in which a refrigerant for cooling the fuel cell circulates; at least one heat exchanger fluidly connected within the closed cooling circuit for cooling the refrigerant; the at least one heat exchanger has a cooling tube; the at least one heat exchanger can be flowed by air from an air inlet face to an air outlet face and by the refrigerant through the cooling tubes; the evaporative cooling system includes a supply device through which a supply fluid flows for cooling the at least one heat exchanger; the supply device has an outlet opening for the supply fluid, through which the supply fluid is supplied to the cooling pipes of the at least one heat exchanger; In evaporative cooling systems, the supply fluid is water discharged from the fuel cell; The cooling tubes of the at least one heat exchanger have cores, and the cores of the cooling tubes of the at least one heat exchanger are made of a first aluminum alloy, the first aluminum alloy including a minimum of about 0.0 wt. % to a maximum of about 1.0 wt. % Si, a minimum of about 0.5 wt. % to a maximum of about 2.0 wt. % Mn, a minimum of about 0.3 wt. % to a maximum of about 1.0 wt. % Cu, a minimum of about 0.0 wt. % to a maximum of about 0.6 wt. % Fe, a minimum of about 0.0 wt. % to a maximum of about 0.2 wt. % Ti, a minimum of about 0.0 wt. % to a maximum of about 0.5 wt. % Mg, a minimum of about 0.0 wt. % to a maximum of about 0.5 wt. % Zn, and less than 0.05 wt. % other elements. An evaporative cooling system comprising:

2. 10. The evaporative cooling system of claim 1, wherein the cooling tubes of the at least one heat exchanger have a wall thickness of from about 0.20 mm minimum to about 0.50 mm maximum.

3. 3. The evaporative cooling system of claim 1, wherein the core of the cooling tube of the at least one heat exchanger has at least one first plating layer on the supply side.

4. 4. The evaporative cooling system of claim 3, wherein the at least one first plating layer is comprised of a second aluminum alloy having a minimum of about 6.8 wt.% to a maximum of about 12.0 wt.% Si, a minimum of about 0 wt.% to a maximum of about 0.8 wt.% Fe, a minimum of about 0.0 wt.% to a maximum of about 0.25 wt.% Cu, a minimum of about 0.5 wt.% to a maximum of about 3.5 wt.% Zn, and less than 0.05 wt.% other elements.

5. 5. The evaporative cooling system of claim 1, wherein the heat exchanger further comprises fins, the fins preferably having a thickness of about 0.05 mm minimum to 0.20 mm maximum.

6. 6. The evaporative cooling system of claim 5, wherein the fins are comprised of a third aluminum alloy comprising: a minimum of about 0.5 wt. % to a maximum of about 2.0 wt. % Si; a minimum of about 0.3 wt. % to a maximum of about 2.0 wt. % Mn; a minimum of about 0.3 wt. % to a maximum of about 2.0 wt. % Cu; a minimum of about 0 wt. % to a maximum of about 0.7 wt. % Fe; a minimum of about 0.0 wt. % to a maximum of about 0.1 wt. % Mg; a minimum of about 1.0 wt. % to a maximum of about 2.0 wt. % Zn; and less than 0.05 wt. % other elements.

7. 7. The evaporative cooling system of claim 1, wherein the heat exchanger further comprises at least one bottom, preferably two bottoms, the at least one bottom preferably having a thickness of at least about 0.5 mm to at most about 3 mm.

8. 8. The evaporative cooling system of claim 7, wherein the at least one bottom has a core, or the at least one bottom has a core and further has at least one second plating on at least the supply side.

9. the bottom core is made of a fourth aluminum alloy, the fourth aluminum alloy including about 0.0 wt. % minimum to about 1.0 wt. % maximum Si, about 0.5 wt. % minimum to about 2.0 wt. % maximum Mn, about 0.3 wt. % minimum to about 1.0 wt. % maximum Cu, about 0.0 wt. % minimum to about 0.7 wt. % maximum Fe, about 0 wt. % minimum to about 0.2 wt. % Ti, about 0.0 wt. % minimum to about 0.5 wt. % Mg, about 0.0 wt. % minimum to about 0.5 wt. % Zn, and less than 0.05 wt. % other elements; and / or the at least one second plating is comprised of a fifth aluminum alloy, the fifth aluminum alloy including a minimum of about 6.8 wt. % to a maximum of about 12.0 wt. % Si, a minimum of about 0.0 wt. % to a maximum of about 0.8 wt. % Fe, a minimum of about 0.0 wt. % to a maximum of about 0.25 wt. % Cu, a minimum of about 0.0 wt. % to a maximum of about 0.5 wt. % Zn, and less than 0.05 wt. % other elements.

9. The evaporative cooling system of claim 8.

10. The at least one heat exchanger of the evaporative cooling system comprises: a) preparing the heat exchanger to be inspected, optionally together with a supply device fixed to the heat exchanger; b) optionally providing a feeding device; c) optionally fixing said supply device to said heat exchanger to be tested; d) placing the heat exchanger to be tested and the supply device in a climate chamber, the climate chamber being equipped with a device for generating an air flow, the climate chamber being thermostated at approximately 35°C, the surface to be supplied being arranged at an angle α to the vertical, the angle α having a value of approximately 20°; e) attemperating the heat exchanger to be tested to a heat exchanger temperature of about 85°C, the attemperating being performed via a coolant guided through the tubes of the heat exchanger; f) supplying a supply fluid to the heat exchanger to be tested and simultaneously passing an air flow through the heat exchanger to be tested for about 10 seconds, ＊ m ２ ) a supply fluid of a supply amount of 0.01 MPa (0.01 MPa), the supply fluid being deionized water, the deionized water having a conductivity of less than 10 μS / cm; g) at least partially drying the heat exchanger to be inspected by passing an air flow through it for about 30 seconds, wherein the climate chamber has a relative air humidity of at least about 35% and at most about 65% during step g), and alternately repeating steps f) and g) about 180,000 times, wherein the air flow in steps g) and f) has an average air flow velocity of at least about 2 m / s and at most about 3 m / s; h) removing the heat exchanger to be inspected and the supply device from the climate chamber, wherein the at least one heat exchanger has a minimum remaining wall thickness of about 100 μm after treatment of all tubes.

10. An evaporative cooling system according to any one of claims 1 to 9, characterized in that it is suitable for being subjected to a treatment comprising

11. A fuel cell system comprising an evaporative cooling system according to any one of claims 1 to 10.

12. Use of the fuel cell system according to claim 11 in a motor vehicle.

Images