DEVICE AND METHOD FOR COOLING AN EXHAUST AFTERTREATMENT DEVICE

Description

[0001] The invention relates to a device and a method for cooling an exhaust gas aftertreatment device, preferably an additive dosing device.

[0002] So-called SCR (selective catalytic reduction) systems can be used to reduce nitrogen oxide emissions from internal combustion engines. In these systems, a dosing system can be used to add a reducing agent (e.g., an aqueous urea solution) to the exhaust gas, which can then be used to convert the nitrogen oxides into non-toxic compounds in a subsequent process. Depending on the design of the SCR system, temperature-sensitive components are located directly on components that carry hot exhaust gas. To prevent these components from overheating, they must be cooled. This can be achieved, for example, by connecting them to a coolant circuit, e.g., of the internal combustion engine.

[0003] The coolant can be circulated in the coolant circuit by the engine's coolant pump while the engine is running. After the engine is shut down, a potentially prolonged "afterheating" period occurs, resulting in significant heat transfer from the exhaust components to the SCR components installed there. To prevent component damage and reduced service life, the SCR components must be cooled in some form, if necessary, even after shutdown during the "afterheating" period.

[0004] DE 10 2014 221 655 A1 discloses a dosing module for introducing a fluid into a line. The dosing module is connected to a coolant circuit for cooling at least part of the dosing module as needed, and a flow control device is arranged in the coolant circuit. The flow control device is a valve device that controls the coolant inflow into the dosing module and the coolant outflow from the dosing module. The valve device consists of a valve installed on the inlet side of the dosing module and a valve installed on the outlet side of the dosing module.In the event of a shutdown, a forced flow of coolant through the dosing module is ensured after the coolant evaporates in the coolant supply line and thus causes a pressure increase, whereby the coolant escapes through the valve in the drain and subsequently, when the pressure drops, new cooling water is sucked through the valve into the coolant supply line.

[0005] A disadvantage of the system known from DE 10 2014 221 655 A1 may be that the cooling is insufficient. Under certain conditions, the coolant temperature and thus the pressure may rise continuously, and the pressure may not drop again before the permissible component temperatures are exceeded. A continuous coolant flow is not achieved.

[0006] The invention is therefore based on the object of creating an alternative and / or improved technology for cooling an exhaust gas aftertreatment device.

[0007] The problem is solved by the features of the independent claims. Advantageous further developments are specified in the dependent claims and the description.

[0008] The invention provides a device for cooling an exhaust gas aftertreatment device (e.g., SCR exhaust gas aftertreatment device), preferably an additive dosing device (e.g., reducing agent dosing device (e.g., reducing agent injector)). The device has a coolant circuit for conducting a coolant. The coolant circuit has a cooling region (e.g., comprising a cooling coil and / or a heat exchanger) for heat transfer with the exhaust gas aftertreatment device. The coolant circuit has at least one, namely at least two, backflow preventers, preferably check valves. A first backflow preventer is arranged upstream of the cooling region. A second backflow preventer is arranged downstream of the cooling region. The coolant circuit has a cooling section between the cooling region and the second backflow preventer.The second backflow preventer is designed and / or oriented such that it opens (e.g., already) upon a volume change (e.g., without a phase change of the coolant and / or a periodic volume change with alternating volume increases and decreases) of the coolant in the cooling region (and optionally in a section, e.g., a line section, preferably the cooling section, of the coolant circuit between the cooling region and the at least one backflow preventer) that occurs below a boiling point of the coolant. This preferably provides a suitable continuous or quasi-continuous natural circulation of the coolant in the coolant circuit below the boiling point of the coolant.

[0009] The device can enable cooling of the exhaust gas aftertreatment system with coolant, e.g., engine coolant, after a coolant pump in the coolant circuit has been shut off. The device can be implemented cost-effectively and independently of any piping. For example, coolant circulation can be ensured solely by a temperature difference between the exhaust gas aftertreatment system / cooling area and a downstream (line) section of the coolant circuit. Circulation is not dependent on the coolant boiling in the cooling area. Instead, circulation can already take place in a temperature range that lies below the coolant's boiling point.The volume changes of the coolant already occurring in this temperature range can be sufficient to enable the circulation of the coolant through backflow preventers with appropriately adjusted opening pressures. Specifically, for example, an increase in the volume of the coolant in the cooling zone can lead to coolant being pushed into the section downstream of the cooling zone, conveniently passing a backflow preventer. Meanwhile, a backflow preventer in the section upstream of the cooling zone prevents the coolant from being forced upstream. The coolant can also cool down in the section downstream of the cooling zone. This again leads to a decrease in volume, which ensures that coolant is sucked in from the section upstream of the cooling zone.

[0010] The at least one backflow preventer has a suitable first backflow preventer, preferably a check valve, which is arranged upstream of the cooling region. The at least one backflow preventer has a suitable second backflow preventer, preferably a check valve, which is arranged downstream of the cooling region, preferably at a distance from the cooling region. The coolant circuit has a cooling section between the cooling region and the second backflow preventer. The first backflow preventer can allow coolant to flow in, but the coolant cannot be pushed back into the supply line. The second backflow preventer can allow coolant to be discharged, but the coolant cannot be sucked back from the return line.The spaced arrangement of the second backflow preventer can result in the section of the coolant circuit between the cooling area and the second backflow preventer serving as a cooling section. In this section, coolant previously heated in the cooling area can cool down, thereby reducing the coolant volume and thus causing coolant to be sucked in from the supply line.

[0011] The first backflow preventer and / or the second backflow preventer are designed to have an opening pressure for opening the backflow preventer of less than or equal to 10 mbar, preferably less than or equal to 1 mbar, particularly preferably less than or equal to 0.1 mbar or 0.05 mbar. Alternatively or additionally, the first backflow preventer and / or the second backflow preventer are designed to have an opening pressure that leads to the backflow preventer opening when the coolant experiences a volume change that occurs below the boiling point of the coolant. The low opening pressure allows the coolant to pass through the backflow preventer even when the coolant experiences volume changes that occur below a boiling point of the coolant.

[0012] It is also possible that the first backflow preventer and / or the second backflow preventer is designed to be kept open in the event of a, preferably slight, fluid flow caused by a change in volume of the coolant below the boiling temperature.

[0013] In a further embodiment, the first backflow preventer and / or the second backflow preventer are oriented in an ascending, preferably vertical or nearly vertical, installation position. This can have the advantage that the backflow preventer, for example in the form of a ball check valve or a flap check valve, is held in the closed position solely by gravity. The backflow preventer can thus have a comparatively low opening pressure. The low opening pressure can allow the backflow preventer to open even when the coolant's volume changes below its boiling point.

[0014] In one embodiment, the first backflow preventer and / or the second backflow preventer are held in a closed position solely or substantially solely by the weight of a closure element (e.g., a closure ball or closure flap) of the backflow preventer. With a low mass of the closure element, a comparatively low opening pressure for the backflow preventer can thus be achieved. This allows the backflow preventer to open even when the coolant's volume changes below its boiling point.

[0015] In a further embodiment, the first backflow preventer and / or the second backflow preventer are not spring-loaded. By omitting a spring preload for a closure element of the backflow preventer, a comparatively low opening pressure of the backflow preventer can also be achieved. Again, the low opening pressure can allow the backflow preventer to open even with volume changes of the coolant that occur below the coolant's boiling point.

[0016] In one embodiment, the first non-return valve and / or the second non-return valve is a ball check valve. Preferably, the ball check valve can be oriented in an upward, preferably vertical or nearly vertical, installation position, can be non-spring-loaded, and / or can be held in a closed position solely or essentially solely by the weight of a closure ball of the ball check valve.

[0017] In a further embodiment, the first backflow preventer and / or the second backflow preventer is a flap check valve. Preferably, the flap check valve can be oriented in a horizontal or approximately horizontal installation position, can be non-spring-loaded, and / or can be held in a closed position solely or essentially solely by the weight of a check flap of the flap check valve.

[0018] In one embodiment, a portion of the coolant circuit may be oriented approximately vertically or vertically, preferably directly, ascending downstream of the cooling region, preferably to form a vapor bubble pump (mammoth pump).

[0019] The cooling area can expediently be designed and / or arranged to cool the exhaust gas aftertreatment device.

[0020] Preferably, the coolant circuit can include a coolant pump (e.g., an internal combustion engine coolant pump). Thus, during normal operation, the coolant pump can be used to pump the coolant. After the coolant pump is shut off, the coolant can then be circulated by natural circulation using the device disclosed herein.

[0021] It is possible that the coolant circuit is an internal combustion engine coolant circuit, or at least part of one. The coolant can be an internal combustion engine coolant (e.g., engine cooling water). Alternatively, the additive, for example, can also be used as the coolant.

[0022] The invention also relates to a motor vehicle, preferably a commercial vehicle (e.g., a truck or bus). The motor vehicle has an exhaust gas aftertreatment device (e.g., an SCR exhaust gas aftertreatment device), preferably an additive dosing device (e.g., a reducing agent dosing device). The motor vehicle further has a device for cooling the exhaust gas aftertreatment device, as disclosed herein.

[0023] It is also possible to use the device as disclosed herein for passenger cars, large engines, off-road vehicles, stationary engines, marine engines, etc.

[0024] The invention also relates to a method for cooling an exhaust gas aftertreatment device (e.g., an SCR exhaust gas aftertreatment device), preferably an additive dosing device (e.g., a reducing agent dosing device (e.g., a reducing agent injector)). The method comprises cooling the exhaust gas aftertreatment device through a cooling region of a coolant circuit, expediently by heat transfer from the exhaust gas aftertreatment device to the coolant in the cooling region. The method further comprises conveying coolant through the coolant circuit in a natural circulation, which is already brought about by a volume change (e.g., without a phase change) of the coolant in the cooling region below a boiling point of the coolant, preferably after a coolant pump of the coolant circuit has been switched off.The method can achieve the same advantages as the device disclosed herein for cooling an exhaust gas aftertreatment device.

[0025] In one embodiment, the conveying is continuous or quasi-continuous.

[0026] In a further embodiment, the natural circulation is additionally effected by a change in the volume of the coolant in a section of the coolant circuit, preferably directly upstream of the cooling region, and / or in a section of the coolant circuit, preferably directly downstream of the cooling region. Preferably, the section of the coolant circuit upstream of the cooling region can be delimited by a backflow preventer. It is also possible for the section of the coolant circuit downstream of the cooling region to be delimited by a backflow preventer.

[0027] In one embodiment, the volume change of the coolant is a periodic volume change, preferably with alternating volume increase, preferably in the cooling region by heat supply from the exhaust gas aftertreatment device, and volume decrease, preferably in a section of the coolant circuit downstream of the cooling region by heat dissipation to the environment.

[0028] In a further embodiment, a subsequent flow of coolant to the cooling region is effected by cooling and an associated decrease in volume of the coolant in a section of the coolant circuit downstream of the cooling region.

[0029] The method uses the apparatus for cooling an exhaust aftertreatment device as disclosed herein.

[0030] The device and the method disclosed herein can also offer advantages over other possible solutions, but can also be combined with them. For example, an additional electric coolant pump in the coolant circuit can be dispensed with if desired. The additional electric coolant pump can, for example, circulate a coolant in the cooling circuit for a follow-up time after the internal combustion engine and the internal combustion engine coolant pump have been switched off, even after the internal combustion engine has been switched off. By potentially dispensing with this pump, costs for the additional coolant pump and energy for driving the additional coolant pump can be saved, for example. A constantly increasing power transfer can also be dispensed with if desired.When routing lines that rise steadily from the exhaust aftertreatment system to a coolant expansion tank or engine block, a thermosiphon effect occurs due to the significantly higher temperature in the exhaust aftertreatment system. The change in density caused by the heating and evaporation of the coolant causes the coolant to circulate. However, this cost-effective option may be difficult or rarely feasible due to space constraints and installation situations. If desired, a coolant reservoir near and above the exhaust aftertreatment system can be dispensed with. When coolant boils, the coolant reservoir can cause vapor bubbles to condense more quickly and allow more coolant to continue to flow. However, since the circulation of coolant in the rest of the coolant circuit, possibly due to the cooling water being circulated, can lead to a build-up of coolant vapors.Since the flow direction at the exhaust aftertreatment system cannot be predicted in a hot, stationary internal combustion engine, it is possible that the after-run function may not always be guaranteed. Furthermore, the function can be highly dependent on the installation position and vehicle inclination.

[0031] The above-described preferred embodiments and features of the invention can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawings. They show: Figure 1 is a schematic illustration of an exemplary device for cooling an exhaust aftertreatment device according to the present disclosure; and Figure 2 is a schematic illustration illustrating thermodynamic relationships that can be utilized by the method and device for cooling an exhaust aftertreatment device according to the present disclosure.

[0032] The embodiments shown in the figures correspond at least partially, so that similar or identical parts are provided with the same reference numerals and for their explanation reference is also made to the description of the other embodiments or figures in order to avoid repetition.

[0033] The Figure 1shows an exemplary device 10 for cooling an exhaust aftertreatment device 12. The exhaust aftertreatment device 12 can expediently be a metering device, for example, an injector, for supplying a reducing agent into an exhaust system 14 of an internal combustion engine. The device 10, the exhaust aftertreatment device 12, and the exhaust system 14 can be incorporated into an internal combustion engine (e.g., a diesel internal combustion engine). The internal combustion engine can expediently be incorporated into a motor vehicle, preferably a commercial vehicle (e.g., a truck or bus), for driving the motor vehicle.

[0034] For example, the metering device can be used to inject a (for example, aqueous) urea solution into an exhaust gas stream flowing in the exhaust line 14. The metering device can be part of an SCR catalyst system, which additionally has an SCR catalyst in the exhaust line 14 downstream of the metering device. The SCR catalyst system can expediently reduce nitrogen oxides in the exhaust gas stream. The metering device can be actuated, for example, by an electronic control unit.

[0035] The device 10 comprises a coolant circuit 16 with a cooling region 18. The coolant circuit 16 can, for example, be connected to a coolant circuit for cooling the internal combustion engine. The coolant circuit 16 can have a coolant pump (not shown), for example a coolant pump of the internal combustion engine. The coolant pump can be operated during operation of the internal combustion engine. The operation of the coolant pump pumps a coolant (for example, cooling water) through the coolant circuit 16. The cooling region 18, through which coolant flows, cools the exhaust gas aftertreatment device 12. The cooling region 18 can, for example, be designed as a cooling coil or a heat exchanger.

[0036] After the coolant pump is switched off, for example by switching off the internal combustion engine, no more coolant is actively pumped through the coolant circuit 16. Nevertheless, it may happen that still hot components (e.g. pipes, etc.) of the exhaust system 14 continue to heat the exhaust aftertreatment device 12 (see Figure 1 : Q̇ This can lead to component damage and reduced service life of the exhaust aftertreatment device 12. It is explained below that the device 10 has one or more backflow preventers to enable cooling of the exhaust aftertreatment device 12 in situations where the coolant pump is switched off.

[0037] The device 10 has a first check valve 20 as a first backflow preventer and a second check valve 22 as a second backflow preventer. The first check valve 20 is arranged upstream of the cooling region 18. The first check valve 20 is thus arranged in a supply line to the cooling region 18. The line section between the first check valve 20 and the cooling region 18 is also referred to herein as the first section 24 of the coolant circuit 16. The second check valve 22 is arranged downstream of the cooling region 18. The second check valve 22 is thus arranged in a return line with respect to the cooling region 18. The line section between the cooling region 18 and the second check valve 22 is also referred to herein as the second section 26 of the coolant circuit 16.

[0038] The check valves 20, 22 are designed and aligned such that they open even at very low opening pressures. Preferably, the check valves 20, 22 (or generally the at least one backflow preventer) open at an opening pressure of less than or equal to 10 mbar, preferably less than or equal to 1 mbar, particularly preferably less than or equal to 0.1 mbar or 0.05 mbar. The opening pressure must be sufficiently low that the backflow preventer can be kept open even by a minimal flow.

[0039] The low opening pressure of the check valves 20, 22 can be used in the embodiment of Figure 1This can be achieved by installing the check valves 20, 22 as non-spring-loaded ball check valves in a vertical position. This means that the check valves 20, 22 are held in a closed position solely by the weight of a closing ball on the check valves 20, 22. In this case, it is not the entire weight of the closing ball that is used to close the valve, but rather only the portion that is not compensated for by the buoyancy of the closing ball in the coolant. A low weight of the ball can be provided by a low mass of the ball. For example, the ball can be made of a plastic material, e.g., nylon. Ball check valves can also have the advantage of offering very little flow resistance once opened.

[0040] For example, for a vertically aligned ball check valve without spring loading, the opening pressure can be calculated as follows: p = 2 3 ∗ Ortsfaktor ∗ Durchmesser Kugel 3 Dichte Kugel − Dichte K ü hlmedium Durchmesser Ventilsitz 2

[0041] The spatial factor is position-dependent. The average value of the spatial factor can be specified as 9.81 m / s^2.

[0042] In other embodiments, a low opening pressure of a backflow preventer can be achieved with additional and / or alternative measures. In addition to the purely vertical orientation of the backflow preventer, all ascending orientations (ascending from the inlet to the outlet of the check valve) are also possible. For example, it is also conceivable for a check valve to be oriented in a horizontal installation position and to be spring-loaded with a very slight preload in the closed position. Another example of a backflow preventer could be a flap check valve, which, for example, is oriented in a horizontal installation position and whose check flap is held in the closed position only by its weight.

[0043] The fact that the check valves 20, 22 have a very low opening pressure enables natural circulation of the coolant in the coolant circuit 16 after the coolant pump of the coolant circuit 16 is switched off, as explained below. In particular, the very low opening pressure enables natural circulation even in a temperature range for the coolant that is still below the coolant's boiling point. To ensure continuous or at least quasi-continuous flow through the cooling area 18 and thus continuous heat dissipation, periodically occurring volume changes between the check valves 20, 22 can be utilized.

[0044] These are caused by temperature changes experienced by the coolant flowing through it, or in higher temperature ranges by boiling and subsequent condensation.

[0045] As it flows through the cooling area 18, the coolant is heated by the exhaust aftertreatment device 12. The coolant expands. The first check valve 20 in the flow line prevents the coolant from flowing back. Due to the increase in volume, the coolant is forced into the return line, which is cooler than the exhaust aftertreatment device 12, i.e., into section 26. The second check valve 22 opens, and the coolant passes through the second check valve 22. In section 26, the coolant cools down again (see Figure 1 : Q̇ _ ab). As soon as the heat dissipation from section 26 to the environment exceeds the heat flow supplied to the coolant in the cooling area 18, the volume decreases and the coolant is sucked in through the first check valve 20. The second check valve 22 prevents coolant from being sucked out of a section (cooling section) of the coolant circuit 16 downstream of the second check valve 22.

[0046] Natural circulation occurs both in a temperature range below the boiling point of the coolant in the cooling section 18 and in a temperature range above the boiling point of the coolant in the cooling section 18. The thermodynamic processes that cause natural circulation are similar. The heat input in the cooling section 18 reduces the density of the coolant. The volume of the coolant increases. The increase in volume of the coolant due to the heat input in the cooling section 18 leads to the expulsion of coolant through the second check valve 22. A decrease in volume of the coolant in the second section 26 due to cooling leads to the flow of coolant through the first check valve 20 into the first section 24. Since the opening pressure of the check valves is very low, preferably approximately zero, the circulation of the coolant can only be caused by the (periodic) volume change.

[0047] The second section 26 can have an important influence on ensuring that the delivery / natural circulation of the coolant does not come to a standstill. The second section 26 serves as a cooling section for cooling the coolant, with an associated decrease in the volume of the coolant. As a result, coolant is sucked in through the first check valve 20. The second section 26 can be expediently designed for the respective installation situation. Influencing variables to be taken into account here can be a heat transfer from the exhaust system 14 to the exhaust gas aftertreatment device 12, a coolant temperature at the inlet of the cooling region 18, an ambient temperature in the region of the second section 26, a cooling system pressure and / or a coolant composition. In general, two cases can be distinguished. In the first case, a temperature of the exhaust gas aftertreatment device 12 (for example, an inner wall temperature thereof) is below the boiling point of the coolant.No vapor bubbles form in the coolant. In the second case, the temperature of the exhaust aftertreatment device 12 (for example, its inner wall temperature) is above the boiling point of the coolant. Vapor bubbles form in the coolant in the cooling area 18, which can condense again in the downstream section 26.

[0048] In the first case, when no boiling occurs, the coolant can only be conveyed by the (periodic) volume changes caused by the temperature increase in the cooling area 18 and the subsequent cooling in section 26. To ensure that this process does not come to a standstill, the volume reduction between the check valves during the contraction phase must be at least as large as the volume increase in this area during the expansion phase. Here, for example, approximately and with reference to Figure 2 apply: Δ V Exp ≤ Δ V Kon

[0049] After transformation, V KB ∗ T KB t 2 − T KB t 0 ≤ V AS ∗ T AS t 0 − T AS t 2 with: Δ V Exp = Volume increase of the liquid between the check valves during the expansion phase Δ V Kon = Volume decrease of the fluid between the check valves during the contraction phase V KB = Volume of the cooling area 18 V AS = Volume of the cooling section 26 T KB = Average media temperature in the cooling area 18 T AS = Average media temperature in the cooling section 26 t 0 = start of the expansion phase t 1 = beginning of the contraction phase t 2 = End of compression phase

[0050] The average heat flow to be taken into account for the design of the check valves 20, 22, the cooling area 18 and / or the sections 24 and 26 can be calculated with reference to Figure 2 be calculated as follows: Q ˙ Zu = m ˙ ∗ c p ∗ T 2 − T 1 with: Q̇ _zu = heat flow supplied in the cooling area 18 [W] ṁ= supplied / discharged mass flow [kg / s] cpp = specific isobaric heat capacity of the coolant [kJ / kgK]

[0051] The temperature that occurs in section 26 can essentially depend on the ambient temperature in the area of ​​section 26, the pipe outer surface of section 26, the heat transfer coefficient of section 26, the flow velocity of the coolant and the flow type (laminar or turbulent) of the coolant.

[0052] In an optional development of the invention, in the second case, when the temperatures in the cooling region 18 are above the boiling point of the coolant, the continuous heat dissipation in section 26 can, for example, be so great that a temperature below the boiling point of the coolant is established in section 26. The heat transfer that occurs in section 26 can be influenced as described above. Section 26 can expediently be long enough that the vapor bubbles condense at least partially, preferably essentially completely, by the time they reach the second check valve 22.

[0053] As soon as the coolant in the cooling area 18 becomes so hot that vapor bubbles form, two effects can occur: If there is only vapor in the cooling area 18, hardly any more heat can be transferred. As a result, the dissipated heat flow becomes significantly greater than the supplied heat flow, and coolant can flow through the first check valve 20. If vapor bubbles condense again in section 26, there is a sudden decrease in the volume of the coolant, which also causes coolant to flow through the first check valve 20. Due to these effects, permanent, periodic volume changes occur in the area between the two check valves 20, 22, resulting in permanent (passive) pumping and circulation of coolant.

[0054] The design of the check valves can also be crucial for continuous or quasi-continuous coolant circulation. Circulation is achieved solely by the volume changes the coolant experiences during its flow. To minimize interruption of the coolant flow, check valves with very low opening pressure can be used, as previously described. For example, ball check valves, butterfly check valves, or other types of check valves can be used as check valves.

[0055] With reference to Figure 1An embodiment has been described herein in which a backflow preventer is arranged both in the flow to the cooling region 18 and in the return after the cooling region 18. However, in an embodiment not claimed by the invention, it may also be possible to use only a backflow preventer and still effect a conveyance of the coolant. For example, the backflow preventer (e.g. check valve) can be arranged upstream of the cooling region 18. The section 26 downstream of the cooling region 18 can be oriented ascending, approximately vertically, or vertically. In this way, the function of a vapor bubble pump (mammoth pump) can be achieved. The very low opening pressure of the backflow preventer upstream of the cooling region 18 enables a continuous flow of coolant.

[0056] It may also be possible to supplement the device for cooling the exhaust aftertreatment system with a coolant reservoir. The coolant reservoir can, for example, be connected to section 24. Furthermore, a backflow preventer can be arranged downstream of the cooling region 18.

[0057] The present disclosure also relates to a method for cooling an exhaust aftertreatment device. The method uses the device 10 disclosed herein to cool the exhaust aftertreatment component 12.

[0058] The method comprises cooling the exhaust gas aftertreatment device 12 by a cooling region 18 of the coolant circuit 16, preferably after a coolant pump of the coolant circuit 16 has been shut down. The method further comprises a suitable continuous or quasi-continuous conveyance of coolant through the coolant circuit 16 in a natural circulation, which is effected by a preferably periodic volume change (e.g., without phase transition) of the coolant in the cooling region 18, in section 24, and / or in section 26 already below a boiling point of the coolant.

[0059] The volume change of the coolant can expediently be a periodic volume change, with alternating volume increase in the cooling area due to heat supply from the exhaust gas aftertreatment device and volume decrease in section 26 due to heat dissipation to the environment.

[0060] The method may further comprise a subsequent flow of coolant to the cooling region 18 by cooling and an associated decrease in volume of the coolant in the section 26. Reference symbol list

[0061] 10Device for cooling an exhaust aftertreatment device 12Exhaust aftertreatment device 14Exhaust system 16Coolant circuit 18Cooling area 20First check valve (first non-return valve) 22Second check valve (second non-return valve) 24First section 26Second section (cooling section)

Claims

1. A device (10) for cooling an exhaust-gas aftertreatment apparatus (12), preferably an additive metering apparatus, having: a coolant circuit (16) for conducting a coolant, with: - a cooling region (18) for heat transfer with the exhaust-gas aftertreatment apparatus (12); - a first backflow preventer (20), which is arranged upstream of the cooling region (18); - a second backflow preventer (22), which is arranged downstream of the cooling region (18); and - a cooling path section of the coolant circuit (16) between the cooling region (18) and the second backflow preventer (22), wherein the second backflow preventer (22) is configured and / or oriented such that, in the event of a change in volume of the coolant in the cooling region (18) said second backflow preventer (22) opens, characterized in that the change in volume takes place below a boiling point of the coolant, preferably in order to provide a continuous or quasi-continuous natural circulation of the coolant in the coolant circuit (16) below the boiling point of the coolant, wherein the first backflow preventer (20) and / or the second backflow preventer (22) is configured to have an opening pressure for the opening of the backflow preventer (20, 22) of less than or equal to 10 mbar, preferably less than or equal to 1 mbar, particularly preferably less than or equal to 0.1 mbar or 0.05 mbar; and / or the first backflow preventer (20) and / or the second backflow preventer (22) is configured to have an opening pressure which leads to the opening of the backflow preventer (20, 22) if the coolant undergoes a change in volume that takes place below the boiling point of the coolant.

2. The device (10) as claimed in claim 1, wherein: the first backflow preventer (20) is a check valve and / or a second backflow preventer (22) is a check valve and / or is arranged spaced apart from the cooling region (18).

3. The device (10) as claimed in claim 1 or 2, wherein: the first backflow preventer (20) and / or the second backflow preventer (22) is configured to be held open in the presence of a, preferably small, fluid flow caused by a change in volume of the coolant below the boiling point.

4. The device (10) as claimed in one of the preceding claims, wherein: the first backflow preventer (20) and / or the second backflow preventer (22) is oriented in a rising, preferably vertical or approximately vertical, installation position.

5. The device (10) as claimed in any one of the preceding claims, wherein: the first backflow preventer (20) and / or the second backflow preventer (22) is held in a closed position solely or substantially only by a weight force of a closure element of the backflow preventer (20, 22).

6. The device (10) as claimed in any one of the preceding claims, wherein: the first backflow preventer (20) and / or the second backflow preventer (22) is non-spring-loaded.

7. The device (10) as claimed in any one of the preceding claims, wherein: the first backflow preventer (20) and / or the second backflow preventer (22) is a ball check valve, which is preferably: - oriented in a rising, preferably vertical or approximately vertical, installation position; and / or - non-spring-loaded; and / or - held in a closed position solely or substantially only by a weight force of a closure ball of the ball check valve.

8. The device (10) as claimed in any one of claims 1 to 6, wherein: the first backflow preventer (20) and / or the second backflow preventer (22) is a flap check valve, which is preferably: - oriented in a horizontal installation position or in an approximately horizontal installation position; and / or - non-spring-loaded; and / or - held in a closed position solely or substantially only by a weight force of a check flap of the flap check valve.

9. The device (10) as claimed in any one of the preceding claims, wherein: a section of the coolant circuit (16) preferably directly downstream of the cooling region (18) is oriented in a rising, approximately vertical or vertical manner, preferably so as to form a vapor-bubble pump (airlift pump).

10. A motor vehicle, preferably a utility vehicle, having: an exhaust-gas aftertreatment apparatus (12), preferably an additive metering apparatus, and the device (10) as claimed in any one of the preceding claims.

11. A method for cooling an exhaust-gas aftertreatment apparatus (12), preferably an additive metering apparatus, comprising: cooling of the exhaust-gas aftertreatment apparatus (12) by means of a cooling region (18) of a coolant circuit (16); and conveying of coolant through the coolant circuit (16) in a natural circulation, which is caused by a change in volume of the coolant in the cooling region (18) already below a boiling point of the coolant, preferably after a coolant pump of the coolant circuit (16) has been deactivated, wherein the method uses the device (10) as claimed in any one of claims 1 to 9.

12. The method as claimed in claim 11, wherein: the conveyance is continuous or quasi-continuous.

13. The method as claimed in claim 11 or claim 12, wherein: the natural circulation is additionally caused by a change in volume of the coolant in a section of the coolant circuit (16) preferably directly upstream of the cooling region (18) and / or in a section of the coolant circuit (16) preferably directly downstream of the cooling region (18), wherein preferably: - the section of the coolant circuit (16) upstream of the cooling region (18) is delimited by a backflow preventer (20); and / or - the section of the coolant circuit (16) downstream of the cooling region (18) is delimited by a backflow preventer (22).

14. The method as claimed in any one of claims 11 to 13, wherein: the change in volume of the coolant is a periodic change in volume, preferably with an alternating increase in volume, preferably in the cooling region (18) owing to a supply of heat from the exhaust-gas aftertreatment apparatus (12), and a decrease in volume, preferably in a section of the coolant circuit (16) downstream of the cooling region (18) owing to a dissipation of heat to the environment; and / or a follow-on flow of coolant to the cooling region (18) is caused by cooling and an associated decrease in volume of the coolant in a section of the coolant circuit (16) downstream of the cooling region (18).