EP1457750A1 - Liquid drain for fluid conducting devices - Google Patents

Abstract

The fluid collection process collects fluid from a fluid conveying device (1), the output device (200) of which is on the outlet end of the conveying device. The distance between the output device and the outlet end of the conveying device is either eliminated altogether, or is at least reduced to less than would be required for a state in which droplets would escape spontaneously.

Description

The invention relates to the removal of liquid from fluid-carrying devices, in particular from such facilities that are at least along one spatial direction have narrow channel cross sections and in which the fluid flow is limited driving forces (e.g. small pressure differences).

Background of the Invention

In fluid-carrying devices with - compared to the drop size or thickness of a liquid film - large channel cross sections become the fluid-carrying properties hardly affected if liquid condenses inside the channels (as a film or in drops) or drops at the outlet end of the channels form.

Even with smaller channel cross sections, the removal of liquid from the fluid-carrying Channels, especially of liquid, that are on the inner walls of these channels has usually not been a problem if the fluids with a high pressure difference between fluid inlet and fluid outlet through the fluid guide structure to be driven. The correspondingly high flow rates of the (laminar or turbulent) flowing fluid can then "carry away" liquid, which, for example, condenses on the inner walls, so that liquid is not appreciably on the inner walls or on the Can accumulate outlet ends.

If, on the other hand, the pressure drop between the fluid inlet and the fluid outlet is small, then: the forces exerted by the fluid flowing past on those deposited on the inner wall Liquid act, may not be sufficient to the interior walls liquid deposited or accumulating at the outlet ends to drive out of the channels. If this is the case, then this fluid carries, for example due to the formation of drops, at least in some areas to a narrowing of the channel cross section and / or to a constriction at the outlet end of the Channel. This reduces the effective flow cross-section within the channel and / or at the outlet end of the channel, whereby the flow properties of the fluid guide structure be deteriorated, causing impairment and possibly can even lead to a complete stoppage of a fluid flow.

A typical example of fluid routing structures affected by such problems are plate heat exchangers like those used in many areas of technology for heating, Cooling, evaporation and condensing can be used.

Such a plate heat exchanger consists of an arrangement of parallel plates, that define alternating flow areas for two fluids, for example a warmer fluid to be cooled (primary fluid) by a colder fluid (secondary fluid) is cooled without the two fluids coming into contact with one another. The fluids can be liquids, gases, or gas / liquid mixtures.

When using a plate heat exchanger as a condenser, the primary fluid lies at the heat exchanger inlet gaseous or as a two-phase mixture (Gas / liquid) and is partially or fully condensed in the heat exchanger. The fluid can also be a multi-component fluid from which only one or more components are partially or fully condensed. A typical example is humid air, which is cooled, part of the Water vapor is converted into liquid water.

In the simplest case, the plates of a plate heat exchanger can be plane-parallel and be spaced from each other. But you can also use a channel structure at least one side, either as a meandering structure or as parallel channels is formed so that the plates of the plate heat exchanger directly against each other can be stored. Miniature heat exchangers can have cross sections in the duct On the order of millimeters or fractions thereof. If heat exchanger with such small structures with a low volume flow and a low Pressure drop operated as condensers, condensate drops in the channels or at their ends. This phenomenon also occurs in particular Outlet end of the channels.

Due to the surface tension, it adheres to a wettable material Drops energetically cheaper than a free drop of the same size. Therefore must applied energy to detach the drop from the outlet end of the channel, i.e. Work to be done. This work is done by the droplets flowing through Fluid attacking forces and gravitational force. Because these forces are all the greater are, the larger the drop, it comes from a certain drop size a drop detachment.

Especially in the case of small channel cross-sections that counteract the drop detachment Capillary forces and / or small pressure differences (i.e. small Fluid flow velocities) this can be necessary for droplet detachment Drop size but should be so large that undissolved drops are of this size have not yet reached or due to the geometric restrictions can either block the entire channel or the channel cross-section severely restrict. In these cases, the flow of additional fluids becomes strong impaired to prevented. By blocking or restricting individual channels the total active heat exchanger area is reduced, which ultimately leads to a Failure of the functionality of the heat exchanger can result.

It is an object of the present invention to find solutions to avoid the above To provide problems. This object is achieved by the invention Method and the devices according to the invention solved. Advantageous further training are specified in the subclaims.

According to the method according to the invention for removing liquid from a fluid guide device becomes a liquid drain device at an outlet end the fluid guide device is provided such that the distance between the liquid drain device and the outlet end of the fluid guide disappears or less than that required for automatic droplet detachment Distance.

"Automatic droplet detachment" refers to the state in which the drop is solely under the influence of the flowing fluid and / or the gravitational force would detach from the outlet end.

When the distance between the liquid drain device and the outlet end of the fluid guiding device disappears, it is caused that at the outlet end No drop forms at all and the liquid immediately as a creeping film is transferred to the liquid drain device. If the liquid drain device within the distance required for automatic droplet detachment is arranged, it causes a drop that forms to be in contact arrives with the liquid drain device and detached from the outlet end by this without being the size required for automatic droplet detachment can reach. In this context, it should be noted that the for a automatic droplet detachment generally requires a distance from the geometry and orientation of the arrangement and the shape of the drops depends on and is orientation-dependent. At a distance smaller than that for an automatic droplet detachment is required for a given distance Orientation generally relates to a positioning of the liquid drain device to understand the outlet end at which at least part of the liquid drain device is within the volume range that one is going through not yet replacing drop would be taken.

The inventive method can constrict the outlet end be significantly reduced by liquid and occlusion of the outlet end can be avoided by drops of liquid.

According to a preferred development of the method, the liquid drain device and / or the fluid guiding device with a wetting promoting Provide coating.

In the channels of the fluid guiding device, this causes that instead of Drops on the walls form thin films of liquid that extend the flow profile affect less than drops. A causes at the liquid drain device wetting-promoting coating a faster drainage of liquid. These If the liquid is water or aqueous solutions, it is said to promote wetting Coating particularly advantageously used hydrophilic substances; preferred lipophilic substances for oily liquids. Alternatively, the appropriate facilities made entirely of wetting-promoting materials his.

It should be noted that all conventional devices as a liquid drain device can be used according to the above Procedures can be used.

In particular, a sponge-like material can advantageously be used as the liquid drain device be used at the outlet end of the fluid guide is provided such that the distance between the sponge-like material and the outlet end of the fluid guide device disappears or is smaller than the distance required for automatic droplet detachment. Because of the capillary effect the sponge-like material suppresses droplet formation particularly effectively and thereby promotes fluid drainage. Under "spongy" in Porous materials may also be included in the description of this invention.

Especially for fluid guidance devices with an arrangement of outlet ends However, the inventors propose specially designed liquid drainage devices, such a liquid drain device an arrangement of drain elements includes, which is designed according to the arrangement of free outlet ends is.

According to the method according to the invention, the drain device can be: the outlet ends of the fluid guide are arranged so that each Drain element is provided at an outlet end of the fluid guide device is that the distance between each drain element of the liquid drain device and the corresponding outlet end of the fluid guide device disappears or less than that required for automatic droplet detachment Distance. Several drain elements can also be provided for each outlet end be, which can be particularly advantageous if the outlet end has no highly symmetrical cross-sectional profile, for example elongated is, and / or if the fluid drainage also with different orientations of the Fluid guide device should function reliably.

In a preferred development of the drain device, the drain elements comprise a wetting-promoting surface. As a result, the liquid drain can the fluid guide device can be improved.

Accordingly, it is the case with a fluid guide device with water or water-containing liquid mixtures particularly advantageous, the drain elements with a hydrophilic Form surface.

In a preferred development of the liquid drain device, the Drain elements slats that are provided at the outlet ends, be it that they be attached there later, be it that they are integral with the corresponding Devices of the fluid guide device are formed. With this training there is a vanishing distance between each drain element of the liquid drain device and the corresponding outlet end of the fluid guide device before, so that liquid from the outlet end to the immediately following Slats can be removed and thus blocking the outlet end can be avoided.

In an alternative development, the liquid drain device is not physical connected to the outlet ends of the fluid guide device, but represents an independent Element, for example a mat, the drain elements in the Forms of pins that correspond to the arrangement of the outlet ends of the Fluid guide device are arranged. This liquid drain device can are arranged below the outlet ends of the fluid guide device in such a way that the distance between each pin of the liquid drain device and the corresponding outlet end of the fluid guide device is smaller than that for a automatic droplet detachment required distance. Drops on the outlet ends form and grow, come into contact with the pins and then become immediately derived by this. The distance between the pins and the outlet ends must be chosen so that the drops cannot reach a size, in which they noticeably narrow the omissions.

In a particularly preferred development, the liquid drain device comprises a sponge-like material, the entire liquid drainage device can be formed from the sponge-like material, or just the drain elements. Due to the capillary effect, the sponge-like material suppresses the Drop formation and promotes fluid drainage particularly effectively.

The invention also provides plate elements for a plate heat exchanger. According to the invention, drain elements are on the outlet-side edge of this plate element provided for liquid, preferably integral with the plate member are trained. The use of such plate elements for construction a plate heat exchanger automatically leads to the formation of a liquid drain device, so that it does not have to be used afterwards. Also here is a vanishing distance between each drain element of the liquid drain device and the corresponding outlet end of the fluid guide device (Plate heat exchanger) so that liquid from the outlet end over the immediately following drain elements can be discharged without Thaw the outlet end.

According to the invention, fully assembled fluid guiding devices are also integrated Liquid drainage facilities provided, so that a subsequent installation a liquid drain device is not required.

The integrated liquid drain device can be an inventive one described above Be liquid drain device, the drain elements of the drain device so arranged with respect to the outlet ends of the fluid guide device are that the distances between the drain elements of the liquid drain device and the corresponding outlet ends of the fluid guide device disappear or less than that required for automatic droplet detachment Distance.

The integrated liquid drain device can also be a sponge-like material be arranged with respect to the outlet ends of the fluid guide device that the distances between the outlet ends of the fluid guide and the spongy material disappears or is smaller than that for one automatic droplet detachment required distance. The benefits of sponge-like Materials for liquid drainage have already been mentioned several times and require no repetition here.

In particular, heat exchangers with integrated liquid drain devices provided, in which the problems described above no longer exist.

To better illustrate the invention, it will now be described with reference to the accompanying Figures of particularly preferred embodiments explained.

figure description

Figure 1

shows a section through a conventional plate capacitor;

Figure 2

shows a first preferred embodiment of a drain device for a plate condenser;

Figure 3

shows a second preferred embodiment of a drain device for a plate capacitor;

Figure 4

shows a third preferred embodiment of the invention, in the drain elements is integrated in a plate for a plate capacitor;

Figure 5

shows an application of the inventive method to the conventional Plate capacitor of Figure 1

Figure 1 shows a plate capacitor 1 in a conventional mode of operation in a schematic Sectional view: plates 2 arranged in parallel form alternating flow areas for a primary fluid (fluid to be cooled) and a secondary fluid (cooling Fluid). These plates 2 are closed with end pieces 3 so that the fluids are not can come into direct contact with each other. The heat exchange takes place via the the flow separating plates 2. To the effective heat exchanging To increase area, the plates 2 of the heat exchanger 1 can be substructures have, for example in the plate wall milled channels or ribs on the Panel walls.

The condenser 1 has an inlet 4 on its upper side (top left in the figure) an outlet 5 for the primary fluid 6 and on the underside (bottom left in the figure) for the cooled primary fluid and for the liquid condensed out of the primary fluid on. The inlet and outlet for the secondary fluid 7 are not in the sectional view displayed. The flow of the secondary fluid 7 takes place in the example outlined Plate capacitor perpendicular to the plane of the drawing.

To simplify the description, but without restricting generality, It is subsequently assumed that the fluid to be cooled is warm, humid air and the cooling fluid is cooling air, for example ambient air.

When flowing through the condenser 1, the moist air is cooled and thereby a Part of the gaseous phase of the air to be cooled is converted into liquid water. The water condenses on the walls of the condenser and becomes under the action of gravity and / or the air flowing past in the direction of the Missing driven. The condensate is collected in a drain pan 8 and passed to the outlet 5 and can there to a water separator or Intermediate tank are performed.

The sketched illustration of FIG. 1 further shows liquid drops 9 at the outlet end of channels. The shape of the drops depends on the cross-sectional shape of the channels so that their shape is very different from an ordinary round teardrop shape, e.g. the shape of a free-falling drop or the shape of a drop on a flat surface adhering drop.

The liquid drops 9, in particular at the edge region of the outlet end, held and grow due to the surface tension (interfacial tension) there until the surface tension is due to the weight of the drops and overcompensates forces that the flowing fluid exerts on the drops becomes.

The surface tension and thus the drop size at which detachment occurs depend on the liquid and the wall material, but also on the geometric Conditions (e.g. channel shape and diameter, radii of curvature of the edges at the outlet end), the surface roughness of the channels and the temperature.

The liquid that collects at the outlet end causes small duct cross-sections a non-negligible narrowing of the duct cross-section at the outlet end and leads to an increase in flow resistance for the flowing past Fluid. This leads to a reduction in the volume flow and thus to reduce the effectiveness of the capacitor.

With very small channel cross sections, it can even be completely closed of the dropouts come and, depending on the number of closed channels, to a severe impairment until the functional capacity is abolished of the capacitor.

To a certain extent, droplet formation can be caused by a hydrophilic coating or another surface treatment that increases wetting become. However, the above-mentioned problems cannot be completely solved be eliminated.

Figure 2 now illustrates a first embodiment of a solution according to the invention of this problem.

In the drain pan 8 of the heat exchanger 1, which is otherwise with the heat exchanger 1 is identical, a drain device 200 according to the invention is provided, which has an arrangement of drain elements 210 which correspond to the Arrangement of free outlet ends of the channels for the fluid to be cooled is formed is.

The drain elements 210 are designed as pins that are in place when the drain device is inserted 200 in the drain pan 8 of the heat exchanger 1 just as far extend above that the distance between the pins of the liquid drain device and the respective outlet end of the fluid guide device is smaller than that distance required for automatic droplet detachment. In contrast to the figure 1, the liquid drops 9 in the arrangement of FIG. 2 at the outlet end do not grow until they reach a size at which an automatic, i.d.R. drop detachment essentially caused by the weight. Rather, the surfaces of the growing drops come before they are reached this size in contact with the pins, with each corresponding drop (or at least most of the amount of liquid in the drop) from the outlet end detached and fed through the drain elements 210 of the floor pan.

The drain device 200 is shown in a top view in the lower part of the figure. Since the An elongated rectangular cross-sectional profile at the outlet ends of a plate capacitor , there are several for each outlet end (in the sketched example: three) drainage elements (pins) 200 are provided to prevent excessive drop growth prevent along the entire cross-sectional profile.

A second embodiment of the invention to solve the above The problem is outlined in FIG. 3.

In this embodiment, the drain device 300 is formed by lamella-like drain elements 310 which are provided at the outlet ends of the channels and extend into the floor pan 8 of the plate capacitor 1. Because these slats are attached directly to the outlet ends, the distance between the liquid drain device and the outlet end of the fluid guide device.

As the right part of Figure 3 shows, these slats extend the panels in sections beyond the actual outlet end into the floor pan 8, so that Water can be continuously discharged through the slats to the floor pan and does not have to come loose from the outlet end in the form of free drops. At plate spacing the lamellae are in the order of magnitude of the diameter of liquid drops Adjacent plates are preferably arranged opposite one another, so that a Drop can run between a pair of slats.

The lamellar drain elements 310 can (subsequently) on the plates of the Capacitor can be attached, alternatively - and particularly preferred - but can the individual plates of the condenser including drain elements 310 be made in one piece.

In addition, the rectangular tongue shape of the drain elements 310 of FIG. 3 is only an example to understand. For a channel to function properly, it is important that at least a portion of the outlet end is permeable to the inflowing gas remains, i.e. remains above the fluid play in the floor pan and not through Drops are clogged. An alternative form of drain elements is shown in FIG. 4.

FIG. 4 shows a plate element 402 according to the principles of the present invention, a plurality of such plate elements 402 for forming a plate capacitor be used.

The plate element 402 has tapered drain elements on its underside 410, the drain elements 410 being an integral part of the plate element 402 are. When the plate elements 402 are arranged in a capacitor For example, the triangle tips on the bottom 8b of the floor pan of the capacitor. The liquid level is indicated by a dashed horizontal Line indicated. Between the outlet end and the liquid level Free triangular areas are formed, through which gas exits the channels can, while liquid over the drain elements partially immersed in the liquid 410 can run out of the channels.

Structures 415 are also provided in the walls of the sketched plate 402, which promote that which condenses on the plate walls and runs downwards Liquid flows off in the direction of the sections with drain elements 410, whereby overall a faster drainage of the condensate can be achieved.

5 outlines the application of the method according to the invention to the conventional one Plate capacitor of Figure 1

A liquid drain device 510 is positioned across the bottom of the channels the outlet ends in the floor pan (not shown), so that they with the lower edges of the plates 2 are in contact or there is a distance from them, which is smaller than the distance required for automatic droplet detachment.

Should drip formation on the condensation plates themselves be avoided or the drainage properties of the condensate on the plates are improved a liquid-absorbing substance on the plates. When condensing instead of drops, a thin film of liquid forms on this layer further condensate flows down without droplet formation, and there via the drainage structure is derived. These layers can be made using conventional thin film techniques (e.g. vapor deposition) or by appropriate mechanical application become. The same effect can also be applied by applying thin absorbent Materials such as absorbent membranes or fleece can be achieved. As Materials for the drainage structure are particularly suitable for fabrics that have a high wettability with the condensate, for example hydrophilic ceramics in water, Sponges or materials with well wettable coatings.

Even if many of the above ideas regarding a heat exchanger come in Form of a plate capacitor have been explained, it is nevertheless pointed out that the invention is not limited to this application, but also to others fluid-carrying structures can be applied. Examples are e.g. the flow channels So-called flow fields, as used in fuel cell stacks become. Here, too, the liquid is passed through under a low pressure gradient.

The invention is based on the following physical principles: To make a drop To expel a canal, the drop must be pushed out at the end of the canal become. In doing so, its surface area is increased until it reaches its mass and so that the gravitational force acting on the drop is large enough to cohesive forces and overcome surface tension and thereby the drop replace. If now a drain device with a suitable surface (advantageous promoting wetting, e.g. hydrophilic) on the lower edge of the channels or slightly is spaced e.g. if tips protrude into the channels, the condensate comes already in contact with the drain device during the initial formation of the drop and causes the condensate to drain without the channel being closed becomes. If there is a gap between the drain and the channels, a drop forms that bulges out of the channel and when touched with the drain device running on this.

The scope of the invention is not to be described by the description of the preferred ones Embodiments limited, but only by that in the following claims described circumstances.

Claims (13)

Method for removing liquid from a fluid guiding device, wherein
a liquid drain device is provided at an outlet end of the fluid guide device such that the distance between the liquid drain device and the outlet end of the fluid guide device disappears or is smaller than the distance required for automatic droplet detachment. The method of claim 1, comprising: Provide the liquid drain device and / or the fluid guide device with a wetting-promoting coating. Method according to one of the preceding claims, wherein the liquid drain device comprises a sponge-like material. A liquid drain device for a fluid guide device with an arrangement of outlet ends, comprising: an arrangement of drain elements, which is designed according to the arrangement of outlet ends. Liquid drain device according to claim 4, wherein the drain elements a include wetting promoting surface. Liquid drain device according to claim 5, wherein the drainage elements a include hydrophilic surface. A liquid drain device according to any one of claims 4 to 6, in which the drain elements include fins provided at the outlet ends are. A liquid drain device according to any one of claims 4 to 6, in which the drain elements include pins. A liquid drain device according to any one of claims 4 to 8, comprising: a sponge-like material. Plate element for a plate heat exchanger, being on the outlet side Edge of the plate element drain elements for liquid are provided. A fluid guide device with an arrangement of outlet ends, comprising: a liquid drain device according to any one of claims 3 to 8, wherein the drain elements of the drain device are arranged with respect to the outlet ends of the fluid guide device so that the distances between the drain elements of the liquid drain device and the corresponding outlet ends of the fluid guide device disappear or are smaller than the distance required for automatic droplet detachment , A fluid guide device with an arrangement of outlet ends, comprising: a sponge-like material which is arranged with respect to the outlet ends of the fluid guide device in such a way that the distances between the outlet ends of the fluid guide device and the sponge-like material disappear or are smaller than the distance required for automatic drop detachment. Fluid guide device according to claim 11 or 12, wherein the fluid guide device comprises a heat exchanger.

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