Temperature control device for gaseous media

Abstract

A temperature control device for gaseous media, having a first heat exchanger layer (10) in which a media channel (12) for a gas whose temperature is to be controlled is formed, and a second heat exchanger layer (18; 19) through which heat can be extracted from the first heat exchanger layer (10) and / or through which heat is supplied to the first heat exchanger layer. In order to reliably prevent gas from penetrating into the coolant in the event of a rupture of the first heat exchanger layer (10), according to the invention a diffusion layer (36) is arranged open to the gas whose temperature is to be controlled between the first heat exchanger layer (10) and the second heat exchanger layer (18; 19) for diffusion.

Description

Technical Field

[0001] The present invention relates to a temperature control device for a gaseous medium, having a first heat exchanger layer and a second heat exchanger layer, wherein a medium channel for the gas whose temperature is to be controlled is formed in the first heat exchanger layer, and heat can be extracted from and / or supplied to the first heat exchanger layer through the second heat exchanger layer. Background Technology

[0002] Such temperature control devices are used, for example, in systems for measuring fuel consumption, particularly compressed natural gas or hydrogen consumption, where they form part of a regulating device for adjusting the fuel to a predetermined pressure and temperature to obtain reliable measurement results. Coriolis flow meters are the most commonly used measuring instruments. For example, such a system for measuring consumption is described in WO2020 / 186279A1.

[0003] The problem with known temperature control devices is that most of the heat exchangers used are too slow to allow for rapid temperature changes in a way that is accurately measured by flow sensors in order to achieve a constant fuel temperature.

[0004] To address these issues, temperature control units were proposed in AT 516 611A4 and AT 516 385A4. These units consist of a first heat exchanger layer, a second heat exchanger layer, and a third heat exchanger layer. A spiral flow channel for fuel is formed in the first heat exchanger layer, a thermoelectric element is arranged in the second heat exchanger layer, and a coolant channel is formed in the third heat exchanger layer. When cooling the medium flow to be temperature controlled, heat from the warm side of the thermoelectric element is dissipated through the coolant channel.

[0005] However, a problem with these temperature control units is that capillary cracks can appear on individual heat exchanger layers due to existing stresses, particularly those caused by sometimes high temperature differences. For example, if the gas to be temperature controlled is hydrogen, the possibility of hydrogen diffusing into the coolant must be prevented. However, if two heat exchanger layers are located close to each other on top, it cannot be ruled out that hydrogen could permeate into the coolant despite pressure in the coolant medium lines, which could, for example, make the coolant flammable. This poses a problem for refrigeration units that are designed to cool coolants and are not intended for explosive and / or flammable media. Summary of the Invention

[0006] Therefore, the problem is to provide a temperature control device for gaseous media that reliably prevents the medium to be cooled from permeating into the coolant or permeating in the opposite direction, without negatively affecting heat transfer between different heat exchanger layers. Furthermore, it should be possible to control the temperature of the medium flow as quickly and accurately as possible, regardless of whether heat must be added to or removed from the medium flow.

[0007] This problem is solved by a temperature control device for gaseous media having the features of claim 1.

[0008] The temperature control device for a gaseous medium according to the invention has a first heat exchanger layer, which is designed, for example, as a heat exchanger plate made of stainless steel. Medium channels for the gaseous or liquid gas whose temperature is to be controlled are formed in this first heat exchanger layer. This can be, in particular, natural gas or hydrogen. The medium channels can be inserted into the heat exchanger layer and thus have their own channel walls, or integrally constructed as openings formed by channels inside the heat exchanger plate. Furthermore, the temperature control device has a second heat exchanger layer, which can be designed as a heat exchanger plate and can have channels integrally formed with the plate in the form of internal openings, or the channels can be designed as inserts in the heat exchanger layer. However, the second heat exchanger layer can also extract or supply heat to the first heat exchanger layer in other ways, for example, through thermoelectric elements, such as Peltier elements. Regardless of the design of the second heat exchanger layer, it is therefore used to absorb heat from and / or supply heat to the first heat exchanger layer.

[0009] To minimize the transfer of the medium into the corresponding other layer of the heat exchanger, according to the invention, a diffusion layer is arranged between the first and second heat exchanger layers, and this diffusion layer is open for the diffusion of the gas whose temperature is to be controlled. This results in the gas whose temperature is to be controlled permeating along the diffusion layer to the outside, where it can be detected by a corresponding detector. Therefore, open diffusion means that the gas can move along the diffusion layer with lower flow resistance than the opposing heat exchanger layer. Thus, the gas seeks the easiest exit route. This is also because, for example, when hydrogen is used as the gas whose temperature is to be controlled, it is under high pressure and is therefore also squeezed out of the medium passage through capillary cracks. If the coolant is present in the adjacent heat exchanger layer, since the coolant is also being transported at a pressure higher than atmospheric pressure, the flow resistance will be lower if the diffusion layer is properly selected, allowing hydrogen to be squeezed along the diffusion layer and permeate to the outside. Therefore, unintentional permeation of hydrogen or natural gas into the coolant can be reliably prevented.

[0010] Preferably, the diffusion layer is formed of foil placed between opposing heat exchanger layers, which can then be attached to each other. Thus, the foil creates a flow space between the heat exchanger layers for the medium whose temperature is to be controlled, preventing it from escaping from the medium channels. The different thermal expansions of the two heat exchanger layers can also be compensated for by the foil, as it has a mechanical decoupling effect. This allows materials with approximately different coefficients of expansion to be joined together. This is particularly advantageous for media such as hydrogen, which greatly limits the choice of heat exchanger layer materials. Furthermore, this foil can compensate for non-uniformities on the surface of the heat exchanger layers, resulting in an increased heat transfer contact area compared to a design where the layers are directly attached to each other.

[0011] It is particularly advantageous to make the diffusion layer from graphite. The diffusion layer made from graphite combines high thermal conductivity with very low contact thermal resistance.

[0012] In particular, it is advantageous if the diffusion layer is formed of thermoelectric graphite. In the case of graphite foil designs, there is an additional advantage: they adapt very well to the contact surface, resulting in a large heat transfer surface area and compensating for inhomogeneities. Although thermal conductivity depends on orientation, foils with lower thermal conductivity only in the z-direction (i.e., the thickness direction of the foil) can be produced, but this is not significant because these foils can be produced with layer thicknesses of less than 20 μm, thus still exhibiting sufficiently fast heat conduction. Furthermore, a thermal conductivity greater than approximately 15 W / °C in the z-direction is still significantly higher than that of conventional thermally conductive foils, which have a thermal conductivity of approximately 1 W / °C in the z-direction. These foils therefore do not exhibit significant thermal resistance compared to conventional thermally conductive foils.

[0013] Generally, graphite is non-directional (e.g., pressed amorphous graphite powder). However, thermoelectric graphite has a lower thermal conductivity in the z-direction (perpendicular to the contact area) than metals such as copper or aluminum, but this is not significant because these foils can be produced with layer thicknesses of less than 20 μm. The use of thermoelectric graphite also has the advantage of particularly high thermal conductivity in the contact layer direction (corresponding to the xy plane). In particular, this is 5 times more efficient than copper, and therefore only slightly lower than diamond, which is considered the most well-known thermal conductor. As a result, the overall efficiency of the heat exchanger can be improved by distributing heat more evenly within the heat exchanger layers.

[0014] If the graphite is pyrolytic graphite, it is particularly advantageous. This material has high... It possesses excellent thermal conductivity, being five times higher than that of copper. Furthermore, when using foil, effective heat distribution exists in the x and y directions, i.e., in the extension direction. Therefore, there is excellent full-surface heat transfer between the pyrolytic graphite and the adjacent heat exchanger layer. Moreover, this pyrolytic graphite readily diffuses, thus the space formed by the diffusion layer can be used for the flow of the medium to be cooled.

[0015] For example, the diffusion coefficient of hydrogen in graphite is unsuitable for delivering large quantities of hydrogen to the outside. However, the amount delivered is not a disadvantage due to the availability of highly sensitive gas detectors. Instead, the concentration of process gases in the environment must be limited to a few percent, regardless of the heat exchanger, to prevent explosive atmospheres. Therefore, the detector should respond to a volume of only a few ppm of process gas in the environment, regardless of the heat exchanger.

[0016] The thermal conductivity of the diffusion layer should preferably be higher than that of the diffusion layer. Especially higher This ensures that the diffusion layer does not reduce heat transfer between the two heat exchanger layers.

[0017] In a preferred embodiment, coolant channels are formed in the second heat exchanger layer. Using this coolant, a very large amount of heat can be removed from the medium channels of the first heat exchanger layer in a short time, while simultaneously achieving a correspondingly high coolant flow rate and temperature difference.

[0018] In such an embodiment, the diffusion layer advantageously rests directly against the first and second heat exchanger layers, allowing for compensation of different thermal expansions and non-uniformities, thereby achieving large-area support, which results in very good heat transfer.

[0019] In an alternative embodiment of the invention, thermoelectric elements are arranged between a first heat exchanger layer and a second heat exchanger layer. These elements are primarily used to heat a gas at a controlled temperature very precisely for a short time by applying a voltage to the thermoelectric element. Such thermoelectric elements are, for example, Peltier elements.

[0020] In a continuation of this advantageous embodiment, a diffusion layer is arranged between the thermoelectric element and the first heat exchanger layer, such that hydrogen gas is removed from the temperature control device before it permeates into the thermoelectric element. Furthermore, heat transfer to the thermoelectric element is improved because very good heat conduction occurs along the diffusion layer, thereby effectively compensating for the temperature difference between the region directly adjacent to the thermoelectric element and the region between them.

[0021] Furthermore, it is useful if the diffusion layer is placed between the thermoelectric element and the second heat exchanger layer, which also prevents hydrogen from permeating into the coolant and vice versa, thereby allowing the coolant to escape through the diffusion layer when capillary cracks appear and improving heat transfer to the thermoelectric element.

[0022] If the second heat exchanger layers are arranged on both sides of the first heat exchanger layer, thereby forming a diffusion layer between each second heat exchanger layer and the first heat exchanger layer, even better cooling and / or heating effects are achieved. Furthermore, the medium whose temperature is to be controlled is prevented from seeping into the coolant flow or the second heat exchanger layer on both sides, and a low-pressure-loss flow path is provided for gas escape. Of course, thermoelectric elements can also be placed on both sides between the first and second heat exchanger layers.

[0023] Preferably, the medium passages and / or coolant passages for the gas whose temperature is to be controlled are spiral-shaped. The spiral shape allows for a long cooling distance and a longer residence time of the medium to be cooled, while achieving the most uniform temperature distribution in the heat exchanger, and thus high cooling efficiency. In particular, the counter-rotating spiral portions in the first and second heat exchanger layers are advantageous because this creates a counter-current heat exchanger in which a greater possible temperature difference can be achieved between the inlet and outlet of the medium whose temperature is to be controlled.

[0024] Furthermore, it is advantageous to fabricate the first and / or second heat exchanger layers additively. This eliminates additional heat transfer between the corresponding layers of the heat exchanger itself and the corresponding channel boundary material, for example, the corresponding layers of the heat exchanger itself being the plates in which cooling coils are arranged. The manufacturing process is inexpensive and easy to implement. Additive manufacturing processes are understood to specifically refer to 3D printing.

[0025] Preferably, the coolant passage in the second heat exchanger layer is connected to a coolant pipeline, in which a coolant control valve is arranged. This coolant control valve allows for complete blocking or precise control of the coolant flow, thereby enabling precise control of heat dissipation and allowing the setting of a target temperature for the medium to be controlled.

[0026] The thermoelectric element is preferably supplied with current to heat the medium to be temperature controlled, such that at most the full rated power of the thermoelectric element is provided when the coolant control valve is closed. This means that the control of the flow of the medium for heating the controlled temperature is entirely performed by the thermoelectric element. Since the temperature of the coolant flow is typically low, the coolant flow must be cut off to prevent excessive temperature differences at the thermoelectric element, which in turn leads to a readjustment of the current, resulting in increased heat loss in the Peltier element, which will offset the desired heat transfer output to the first heat exchanger layer.

[0027] In principle, it is advantageous to provide 100% of the rated power of the thermoelectric element, but preferably, the thermoelectric element is supplied with current to cool the medium to be temperature-controlled, such that when the coolant control valve is at least partially open, at most half of the thermoelectric element's rated power is reached. This means that the cooling power is primarily introduced by the coolant. The thermoelectric element is controlled in such a way that it forms minimal thermal resistance and generates as little heat flow as possible, which would otherwise have to be dissipated again. Therefore, the thermoelectric element is used in a supported manner to reduce temperature differences and increase the dynamics of control, which cannot be introduced solely by the coolant flow. It is particularly important that, when energized, the Peltier element reverses the direction of current (warm side to cold side, and vice versa) in the opposite direction to heating operation.

[0028] This results in a temperature control device for gaseous or liquid media, particularly hydrogen or natural gas, which enables highly dynamic control during the heating and cooling of the medium flow while reliably preventing the gas to be cooled from permeating into the coolant flow. A narrow space is created through which the gas to be temperature-controlled can permeate to the outside with low pressure loss, thereby eliminating coolant contamination. Attached Figure Description

[0029] Two embodiments of the temperature control device for gaseous media according to the present invention are shown in the accompanying drawings and described below.

[0030] Figure 1 A top perspective view of the temperature control device according to the present invention is shown.

[0031] Figure 2 It shows Figure 1 The cross-section of the temperature control device.

[0032] Figure 3 A cross-section of an optional temperature control device according to the present invention is shown.

[0033] Figure 4 It shows crossing Figure 1 and Figure 3 The longitudinal section at the center of the temperature control device. Detailed Implementation

[0034] The temperature control device according to the invention includes a first heat exchanger layer 10, within which a spiral medium channel 12 is formed for the medium, particularly hydrogen, whose temperature is to be controlled. Hydrogen is supplied to the spiral channel 12 through a radially outer medium inlet connector 14, and the hydrogen can exit the medium channel 12 again through a radially inner medium outlet connector 16. A pressure of up to 30 bar can exist in this medium channel.

[0035] Above and below each of the first heat exchanger layers 10, the second heat exchanger layers 18 and 19 are attached to the first heat exchanger layers 10 by screws 20 protruding through screw holes 22 on the flange-shaped heat exchanger layers 10, 18 and 19.

[0036] An upper first internal coolant inlet 24 and a radially external first coolant outlet 26 are formed in the upper second heat exchanger layer 18, and they are connected to each other through an internal spiral coolant channel 28 in the upper second heat exchanger layer 18. Similarly, a second internal coolant inlet 30 and a radially external second coolant outlet 32 ​​are formed in the lower heat exchanger layers 18, 19, and they are also connected to each other through an internal spiral coolant channel 34 in the second heat exchanger layer 19. Therefore, the two coolant channels 28, 34 flow in the same flow direction, which is opposite to the flow direction of hydrogen in the medium channel 12, thus forming a counter-current heat exchanger.

[0037] To achieve both sufficient chemical resistance and low weight, temperature control devices constructed in this manner are designed, for example, such that: the first heat exchanger layer 10 is made of stainless steel during additive manufacturing, e.g., 3D printing, and the second heat exchanger layers 18, 19 are made of aluminum or aluminum alloy during additive manufacturing. Besides the potentially different materials, very large temperature differences also occur in the different heat exchanger layers 10, 18, 19. All of this can lead to stress between the heat exchanger layers 10, 18, 19 during temperature changes, or even internal stress within the heat exchanger layers 10, 18, 19, which in turn can lead to the formation of microcracks. Such capillary cracks are also more likely due to the high pressure in the medium channels, and gas is forced through these capillary cracks. In particular, if hydrogen or another combustible gas is used as the gas to be controlled, an urgent situation must be avoided: the gas permeates into the coolant, thereby potentially reaching the cooling unit through the coolant, which is not designed for or approved for combustible or explosive media.

[0038] In the design of temperature control devices constructed in this way, maximizing thermal conductivity is also particularly important. Therefore, the first heat exchanger layer 10 can also be made of silicon. A third possibility is to manufacture the first heat exchanger layer 10 using a special aluminum alloy, such as AlMgSi. These alloys have the best thermal conductivity and are suitable for use with H2. However, copper is often a component of aluminum alloys, making it easier to process.

[0039] Therefore, according to the present invention, it is proposed to arrange a diffusion layer 36 between heat exchanger layers 10, 18, and 19, which is open for the diffusion of the gas whose temperature is to be controlled, allowing the gas to flow through the interior of the diffusion layer 36. Due to the pressure in the medium channel 12, the gas is forced through the diffusion layer 36 into the air surrounding the heat exchanger. This prevents gas from permeating into one of the coolant channels 28 and 34, as overpressure also exists in the coolant channels 28 and 34, which is why the gas seeks the path of least resistance along the diffusion layer 36 and can be detected outside the heat exchanger layers 10, 18, and 19.

[0040] Specifically, pyrolytic graphite foil is used as the diffusion layer 36, which has approximately and The thermal conductivity is within a certain range. In addition to this very high thermal conductivity, the foil also has a certain degree of elasticity, which can compensate for the unevenness of the relative surfaces of the heat exchanger layers 10, 18, and 19, resulting in an increase in contact surface, which in turn leads to an overall improvement in heat exchange between the heat exchanger layers, despite the presence of an additional intermediate layer.

[0041] The coolant flow through the spiral coolant channels 28, 34 is regulated by means of a coolant control valve 38, and the temperature of the medium to be controlled is controlled by means of the coolant temperature. The coolant control valve 38 is arranged in the coolant line 40 leading to the second heat exchanger layers 18, 19. The coolant temperature can be set by means of an external additional heat exchanger and / or a complete cooling unit with a heat pump.

[0042] However, in order to completely abandon coolant temperature control, and to achieve rapid and effective temperature control of the medium flow, while simultaneously cooling and heating the gas to be temperature controlled, such as... Figure 3 As shown, several thermoelectric elements 42, particularly Peltier elements, can be disposed between the first heat exchanger layer 10 and each of the second heat exchanger layers 18, 19.

[0043] By energizing the thermoelectric element 42, the medium flow in the spiral medium channel 12 can be heated, thereby heating the side of the thermoelectric element 42 facing the medium channel 12, while the side of the thermoelectric element 42 facing the second heat exchanger layers 18, 19 is cooled by the applied voltage. In this state, the coolant control valve 38 is closed, so no heat is dissipated through the coolant.

[0044] If the medium to be cooled is to be cooled next, the voltage on thermoelectric element 42 is reduced in the first step, thereby reducing the heat supply. If this is insufficient, coolant control valve 38 reopens, allowing heat to dissipate from thermoelectric element 42, particularly from the gas to be cooled. Here, voltage reversal is performed on thermoelectric element 42, thereby exchanging the warm and cold sides. Importantly, the current is used only to achieve the nominal power of thermoelectric element 42, which is approximately 10% to 30%, because heat losses occur in thermoelectric element 42 and must also be dissipated. The low current flowing through thermoelectric element 42 reduces their thermal resistance, allowing heat to be extracted from the gas to be cooled via the conductive thermoelectric element 42 by the pumped coolant. Rapid temperature changes with small temperature differences can then be achieved by changing the current flowing to thermoelectric element 42.

[0045] In this embodiment, a diffusion layer 36 in the form of pyrolytic graphite foil is arranged between the thermoelectric element 42 and the first heat exchanger layer 10, and between the thermoelectric element 42 and the second heat exchanger layers 18, 19. This has the advantage that hydrogen diffuses again along the diffusion layer 36 and is thus transported to the outside between the first heat exchanger layer 10 and the second heat exchanger layers 18, 19, without permeating into the regions of the coolant channels 28, 34. Therefore, hydrogen or the gas whose temperature is to be controlled can reach the detector without penetrating the coolant.

[0046] Furthermore, the diffusion layer 36 acts as an excellent thermal conductor, which significantly improves the connection between the thermoelectric element 42 and the first heat exchanger layer 10 and the second heat exchanger layers 18 and 19. Most importantly, the excellent thermal conductivity in the direction of graphite foil extension results in a very uniform temperature distribution at the heat exchanger layers 18 and 19, even though the thermoelectric element 42 is not fully surface-connected.

[0047] Therefore, very precise temperature control can be achieved, and existing heat loss is minimized. At the same time, it provides a high level of safety against damage caused by flammable coolants.

[0048] It should be clear that the scope of protection is not limited to the described embodiments, but various modifications are possible. For example, multiple first and second coolant layers may be arranged alternately on top of each other. Furthermore, only the second heat exchanger layer may be used.

Claims

1. A temperature control device for gaseous media, having The first heat exchanger layer (10) has a medium channel (12) formed therein for the gas whose temperature is to be controlled. The second heat exchanger layer (18; 19) can extract heat from the first heat exchanger layer (10) and / or supply heat to the first heat exchanger layer (10) through the second heat exchanger layer. Its features A diffusion layer (36) is arranged between the first heat exchanger layer (10) and the second heat exchanger layer (18; 19). The diffusion layer (36) is formed of a foil made of pyrolytic graphite and is open for the diffusion of the gas to be controlled, so that the gas to be controlled can permeate along the diffusion layer to the outside and can be detected there by a corresponding detector.

2. The temperature control device for gaseous media according to claim 1, Its features The thermal conductivity of the diffusion layer (36) exceeds 700. .

3. The temperature control device for gaseous media according to claim 1 or 2, Its features Coolant passages (28; 34) are formed in the second heat exchanger layer (18; 19).

4. The temperature control device for gaseous media according to claim 1 or 2, Its features The diffusion layer (36) is in direct contact with the first heat exchanger layer (10) and the second heat exchanger layer (18; 19).

5. The temperature control device for gaseous media according to claim 1 or 2, Its features Thermoelectric element (42) is arranged between the first heat exchanger layer (10) and the second heat exchanger layer (18; 19).

6. The temperature control device for gaseous media according to claim 5, Its features A diffusion layer (36) is arranged between the thermoelectric element (42) and the first heat exchanger layer (10).

7. The temperature control device for gaseous media according to claim 5, Its features A diffusion layer (36) is arranged between the thermoelectric element (42) and the second heat exchanger layer (18; 19).

8. The temperature control device for gaseous media according to claim 1 or 2, Its features The second heat exchanger layers (18, 19) are arranged on both sides of the first heat exchanger layer (10), and the diffusion layer (36) is arranged between each second heat exchanger layer (18, 19) and the first heat exchanger layer (10).

9. The temperature control device for gaseous media according to claim 3, Its features The medium passage (12) and / or coolant passage (28, 34) for the gas whose temperature is to be controlled are spiral-shaped.

10. The temperature control device for gaseous media according to claim 1 or 2, Its features The first heat exchanger layer (10) and / or the second heat exchanger layer (18; 19) are additively manufactured.

11. The temperature control device for gaseous media according to claim 5, Its features The coolant passages (28; 34) in the second heat exchanger layer (18; 19) are connected to the coolant line (40), and the coolant control valve (38) is arranged in the coolant line.

12. The temperature control device for gaseous media according to claim 11, Its features The thermoelectric element (42) is energized to heat the gas at the temperature to be controlled, such that when the coolant control valve (38) is closed, the thermoelectric element (42) is provided with at most its full rated power.

13. The temperature control device for gaseous media according to claim 11, Its features The thermoelectric element (42) used to cool the medium at a controlled temperature is energized such that when the coolant control valve (38) is at least partially open, it provides at most half of the rated power of the thermoelectric element (42).

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