EP1203190B1 - Ice generator for the production of an aqueous ice-crystal suspension - Google Patents

Abstract

The invention relates to an ice generator for the production of an aqueous ice-crystal suspension. The inventive ice generator consists of a heat exchanger with several pipes (2) for an aqueous refrigerating agent, whereby said pipes extend side by side inside a container for said refrigerating agent in an approximately straight line. The inventive device is also provided with a mechanism for removing ice deposits from the inner walls of the pipes (2). The mechanism is fitted with wiper devices (1), which extend into the pipes (2), and a drive unit (9) for said wiper devices. According to the invention, the wiper devices are made up of interconnected wiper elements along the axes of the pipes, whereby the circumference thereof corresponds in a substantial manner to the inner circumference of the pipes (2), and a passage is provided for the cooling agent. The wiper devices (1) are connected to the drive unit (9) which enables them to create a recurrent lifting movement along the axes of the pipes.

Description

The invention relates to an ice generator for Generation of an aqueous suspension from ice crystals according to the preamble of claim 1.

In the field of refrigeration technology, water plays as Coolant due to the favorable availability and Environmental compatibility plays a major role. Special The use of so-called Ice slurry, an aqueous suspension of small Ice crystals. Because this suspension is in flowable Condition is present, ice slurry can be like a liquid be pumped through pipes. On the other hand, points this refrigerant due to the phase change the ice crystals required to melt water a high energy density. Ice slurry is therefore an ideal medium for the transport and distribution of Cold.

Exemplary areas of application of this medium are the air conditioning of buildings, the use in Local cooling networks, the cooling of storage rooms and the Cooling of production processes, for example in Milk plants.

For the distribution of the cold to the respective ones cooling objects is usually an extensive one Pipe network required. Because of the high energy density of Ice-slurry requires the use of this medium as Coolant significantly smaller pipe diameter Transport lines than when using pure water as a coolant. This leads to savings in the Construction costs of the cooling network. Furthermore, these allow Water-ice suspensions are very even Cooling process, since the phase change at a near constant temperature.

The cooling or cooling systems used for cooling consist mainly of the ice generator or ice maker, an ice storage container, one Stirrers, circulating pumps and the one for cold transfer the heat exchangers required to be cooled various designs.

There are currently different types of technology Concepts for the production of ice slurry known.

In large refrigeration systems, for example, vacuum ice generators often become used at the triple point of the water work. That to be cooled or that to a water-ice suspension Water to be transformed is used in vacuum ice makers to the pressure of the Triple point relaxed. Evaporated through expansion part of the water and extracts heat from the system. As a result, finely divided particles form in the water phase Ice crystals.

Because of the high deployment costs of this Systems, however, they are only used in plants, that require high cooling capacities. On Another disadvantage of vacuum ice makers is that the temperature of the water-ice suspension in the Must be close to the triple point of water. Suspensions with lower temperatures, for example So far -10 ° C cannot be provided.

In another known concept, which is under the term "super cooler" is introduced Water slowly supercooled and ice crystal formation in the Evaporator first by as uniform as possible, suppressed undisturbed flow. In a flow direction following turbulent area crystallized then the ice - comparable to the crystallization process at the vacuum ice maker - in the water phase.

However, there is a disadvantage to this system in the fact that the hypothermia is only possible to a limited extent only a small amount per flow volume of the system can be formed on ice crystals.

The present invention is based on another known methods for producing ice slurry from whose ice generators with the generic term ice scraper can be described. Ice scrapers exist in the Usually from a heat exchanger on one side of evaporating refrigerant and on the other hand of water or an aqueous medium as a coolant is flowed through. Form on the heat exchanger surface itself due to the heat removal by the evaporating Refrigerant ice crystals that are scratched or Scraper mechanism from the heat exchanger wall be removed. Here the ice crystals accumulate in the water or aqueous medium and flow with it this from the ice maker. The stripping mechanism can, for example, by rigid scratches or flexible Wipers can be realized. The stripping mechanisms are from the outside, for example by an electric motor, driven.

An advantage of the ice scraper is mainly in their immunity to interference and the flexible Applications.

Ice scrapers are essentially of two types known. One of these designs is based on one Double-pipe heat exchanger. The liquid refrigerant will evaporated in the annular gap between the two tubes. The aqueous liquid flows through the inner tube pumped, which freezes on the chilled surface and there forms ice crystals. Before there is a solid layer of ice can form, the ice crystals from im Removed inner scraper rotating scraper and form with the flowing aqueous liquid an aqueous suspension. The rotating scraper will driven by an electric motor.

An example of such a design Ice scraper can be found in DE 19707635 A1. at In this configuration, the ice crystals from the Inner wall of the central tube using a Screw conveyor used as an Archimedean screw trained, scraped.

GB 2 232 469 describes an ice machine in Form of a double-tube container, with the inside cylindrical volume the aqueous medium and in the outer jacket the refrigerant are provided. The ice is removed from the inner wall with the help one rotating along the axis Rotor arrangement scraped off with side ice scrapers. However, the rotor takes up a lot of space.

Double tube heat exchangers are also for others Areas of application known. The US shows 3,328,972 Processes for producing extracts, such as of coffee extracts, from aqueous solutions by crystallizing the water in one Double-pipe heat exchanger. This procedure is designed to however just the formation of ice crystals on the Inner wall of the heat exchanger can be avoided. To For this purpose, it is rotatory and vertical moveable device used in the inner tube, which from a central rotor axis arranged thereon Sufficient to generate elements there is turbulent flow on the inner wall of the pipe, to prevent the separation of ice crystals.

Because the ice making performance of an ice scraper however approximately linear from the heat exchanger surface depends on the one with the double tube heat exchanger achievable cooling capacity for many areas of application too low.

Greater achievements can only be done either Parallel connection of several of these double tube heat exchangers or by increasing the pipe diameter to reach. Quadrupling the pipe diameter however, increases the heat exchanger area only by a factor 4, while at the same time the volume by a factor of 16 increases. This leads to a size that for the practical use is not suitable. The parallel connection multiple double tube heat exchanger due to the cost of each double tube heat exchanger mostly for economic reasons uninteresting.

To generate higher cooling capacities with more acceptable Frame sizes are therefore usually tube bundle heat exchangers or evaporator used as they for example in H.L. by Cube et al., "Textbook of Kältetechnik ", Vol. 1, 4th edition, Müller Verlag Heidelberg, Pp. 298-300. These consist of several pipes running parallel to each other for the aqueous coolant contained in a container for the refrigerant run. With a vertical tube bundle evaporator the aqueous liquid is at the top The tube sheet is fed in and forms on the inside of the tube a falling film. In the mantle space, i.e. the space between the tubes and the container wall introduced a refrigerant that evaporates there, so that itself on the inside of the pipe due to the heat removal precipitate ice crystals through the evaporation process. Metallic rods hang in the tubes be moved over eccentric plates so that they Touch the inside of the pipe all the time and touch the Knock off ice crystals. These slingshots or the eccentric plates connected to them driven by a common electric motor. Such tube bundle heat exchangers have the advantage one compared to double tube heat exchangers significantly larger heat exchanger area with more compact Size. Due to the Functional principle, however, somewhat massive be executed and need by their eccentric Drive additional space, so a certain one The minimum diameter of the pipes is not undercut can be. This prevents the use of very small and thus in terms of ice production performance effective inner tubes, so that on the apparatus volume performance of such ice makers not can be increased.

GB 2 285 500 discloses an ice generator of the a heat exchanger with several in one container arranged tubes. With this ice generator if the aqueous coolant is in the container, as the refrigerant flows through the pipes. By this mode of operation the ice crystals attach to the Outer walls of the pipes. For stripping the Ice crystals become plate-shaped Scraper, the openings for the pipes has, applied with a recurring stroke movement.

An alternative concept is known from US 5,488,836 to create an ice-water mixture with a Tube bundle heat exchanger specified. The proposed one Device does not use a stripping device Scraping ice crystals off the inside of the pipe one, but flexibly attached to a rotor axis Threads that form a kind of brush for the separation to prevent ice crystals on the inner wall. The ice crystals are said to be direct in this technique form in the flow.

The object of the present invention is therein an ice generator for generating an aqueous To provide a suspension of ice crystals, the one high performance per construction volume. The ice generator should continue to be simple and inexpensive be feasible.

The task is carried out with the ice generator Claim 1 solved. Advantageous embodiments of the Ice generators are the subject of the subclaims.

The ice generator according to the invention consists of a heat exchanger, preferably in the form of a Tube bundle heat exchanger, with several tubes for an aqueous coolant that is approximately rectilinear side by side in a container for a refrigerant run. There is also a removal mechanism of ice deposited on the inner walls of the pipes intended. The mechanism includes those running in the tubes Scraper devices and a drive for the stripping devices. The stripping devices are together according to the invention along the tube axes connected stripping elements, the Circumference essentially the inner circumference of the pipes corresponds, and which is a central passage for the Have coolants so that they have the flow of Only slightly hamper the coolant through the pipes. The scrapers are with the drive connected, this to the recurring lifting movement drives along the tube axes.

The stripping elements are designed so that they move with their outer limits on the inner wall of the pipes Strip off any ice that has formed. For this it is necessary that the diameter of the stripping elements in the plane perpendicular to the pipe axis essentially the diameter which corresponds to pipes. Of course, this must Condition not exactly adhered to. It can rather small spaces between the stripping elements and the pipe inner wall exist as long the function of stripping ice crystals is fulfilled. Adjusting the scope of the stripping elements on the inner circumference of the pipes means that the stripping elements in plan view in the direction of Pipe axis have the circumferential shape of the inner tube. The stripping elements continue to have a generous size Passage for the coolant so that it is almost can flow freely through the pipe.

It goes without saying that through the Drive generated stroke movement a sufficiently large Hub must generate so that a space between individual stripping elements of the stripping devices is swept by the stroke movement.

The stripping elements can be along the Pipe axis different mutual distances to each other, but are preferably in equidistant from each other.

In a particularly advantageous embodiment the stripping devices have the shape of a Coil spring on, with one turn of the coil spring corresponds to a stripping element.

The material of the coil spring can be such be rigid that this has no elasticity along the Has tube axis. However, the coil spring can also be elastic so that the stripping device a natural vibration during the lifting movement performs.

One designed in the form of a coil spring Scraper has in particular the Advantage of the simple manufacture and the optimal Actuation of the inner tube wall with a small space requirement. Due to the low material volume of the coil spring and the generous central passage the flow of the coolant through the tube is not with special needs. The lifting movement is related to the pitch adjusted the coil spring - or 'vice versa - so that with a low pitch even a small stroke is required.

The use of a tube bundle heat exchanger ensures a high ice production capacity compact design: the jacket space becomes vaporized Refrigerant from a conventional condenser replacement flows through. The tubes of the tube bundle are made by flows through the aqueous phase of the refrigerant. The Coolant can be made from pure water or from Water with freezing additives Fabrics exist as they are from the prior art are known. Formed by the evaporating refrigerant an ice crystal layer in the pipes due to the removal of heat, the permanent through the stripping devices Will get removed. Located in each tube one of these scrapers, the outside diameter essentially the inside diameter of the pipe equivalent. By the movement of the stripping devices along the pipe axes, this will be on the pipe inner walls adhering ice stripped.

The stripping devices preferably occur on End of the tube bundle out of the inner tubes and are connected to a common drive plate.

Due to the special design of the stripping devices in connection with the drive, the one recurring stroke movement of the stripping devices created along the pipe axes, the pipes themselves be carried out with a very small diameter. So ice generators with inner tube diameters can be easily installed less than 10 mm.

Be to the stability of the wipers no high demands. these can can also be made elastic along the tube axes. It is only necessary that the stripping elements with its outer circumference the inner tube wall touch or almost touch. The entire space between the outer boundaries of the stripping elements is available for the passage of the coolant.

By contrasting with the present invention possible reduction of the state of the art Pipe inside diameters allow higher ice production capacities realize. With the invention Ice generator can thus have a higher ice production capacity per construction volume or size. The reduction in pipe inside diameter is due to the flow cross section according to the invention only allows a minimally narrowing stripping mechanism. The Design of the stripping mechanism, for example by using a coil spring, with realize comparatively low costs.

Another advantage of the ice generator according to the invention is that the tubes due to the Stripping mechanism according to the invention not necessarily must have a circular cross-section, but that to increase the surface-volume ratio also non-circular, such as angular or oval cross sections can be provided.

In a preferred embodiment, the Scrapers not from an external drive, such as an electric motor, but by the pulsating flow of the coolant is driven. This takes place via a in the flow of the coolant provided plate that vibrates against the pipe ends is stored and by the pulsation of the Flow is vibrated. The vibration movement is directly on the scraper transfer. This makes the ice crystals continuous stripped from the pipe wall and with the Current carried out. This technology not only saves Drive unit, but also increases the system inherent Safety because the stripping mechanism is automatic with the flow through the ice maker or suspends.

Are the stripping devices in the longitudinal direction designed to be elastic so that they have natural vibrations can perform, so the natural vibrations occur reinforcing these stripping devices to the drive vibrations.

A pulsation of the flow for driving the Scraper direction is when using a displacement pump in the refrigerant circuit of the refrigeration network or the refrigeration system is generated automatically. Should be in the cooling network a centrifugal pump can be used, so the Pulsation are generated by pipe fittings that the Release or close the pipe cross-section alternately. These internals can be swinging or rotating systems. The drive of the pipe internals can in turn by the flow itself or from outside, e.g. with an electric motor.

However, it goes without saying that instead of Above described pulsation drive of the stripping devices also a corresponding mechanism with an external drive, such as an electric motor can be.

Figur 1

schematisch ein erstes Beispiel für eine Abstreifeinrichtung des erfindungsgemäßen Eisgenerators;

Figur 2

schematisch ein zweites Beispiel für eine Abstreifeinrichtung des erfindungsgemäßen Eisgenerators;

Figur 3a/b

zwei Beispiele für die mögliche Rohrquerschnitte des Eisgenerators;

Figur 4

ein Beispiel für einen erfindungsgemäßen Eisgenerator mit einem pulsierenden Antrieb im Querschnitt; und

Figur 5

ein weiteres Beispiel für einen erfindungsgemäßen Eisgenerator mit einem pulsierenden Antrieb im Querschnitt.

The ice generator according to the invention is explained again below using exemplary embodiments in conjunction with the drawings. Here show:

Figure 1

schematically a first example of a stripping device of the ice generator according to the invention;

Figure 2

schematically shows a second example of a stripping device of the ice generator according to the invention;

Figure 3a / b

two examples of the possible tube cross-sections of the ice generator;

Figure 4

an example of an ice generator according to the invention with a pulsating drive in cross section; and

Figure 5

another example of an ice generator according to the invention with a pulsating drive in cross section.

Figure 1 schematically shows an example of the Design of a stripping device 1 in a tube 2 of the tube bundle heat exchanger. The scraper has the form of a in this example cylindrical coil spring, preferably from a Metal, which extends along the pipe axis. The diameter of the coil spring corresponds to this Example exactly the inside diameter of the pipe wall. Here, each stripping element of the stripping device 1 by a full turn of the coil spring formed so that of each stripping element the full inner circumference of the pipe is covered. This Shape of the scraper leaves the coolant sufficient space to flow through the pipe as it hardly reduced the pipe cross-section:

The drive for such a stripping device moves it along the tube axis with one stroke and forth, the at least the pitch of the coil spring equivalent. The lifting movement is in the figure by the Arrow indicated. Through this movement it becomes connected with the shape of the scraper each Area on the inner wall of the pipe with one stroke movement: The ice crystals can move accordingly be scraped off or scraped off efficiently.

Another example of the design of the Scraper devices is schematic in Figure 2 shown. In this example, the stripping elements are the stripping device 1 formed as rings 3, the along the tube 2 via connecting elements 4 in shape from thin bars to a cylindrical ring grid are interconnected. The rings show the same scope as the inner wall of the tube 2 and are equally spaced along the Pipe arranged. The central opening of the rings leaves the coolant enough space so that the tube diameter through the stripping devices 1 not are limited and can be chosen to be very small. The In this case, the drive stroke corresponds at least to that Distance of the stripping elements in this case too the entire inner surface of the tube with each stroke can be scraped off.

3a and 3b are two in plan view Embodiments for the possible design and Arrangement of the tubes 2 of the tube bundle heat exchanger in Container 5 shown for the refrigerant.

While in Figure 3a the usual design with circular pipe cross sections is shown, which includes Design of Figure 3b tubes 2 with elliptical or oval cross sections. With such a configuration can also be stripped use as that of Figures 1 and 2, the Coil spring (Fig. 1) or the annular stripping elements (Fig. 2) here a correspondingly adapted not circular, but elliptical cross section would have.

This embodiment is in the present Invention enables the stripping devices not rotating, but axially to Pipe guide are driven. This allows any - also angular - pipe cross sections realize.

The oval cross section shown in this example the tube allows against a circular Cross section of an overall larger pipe inner surface and thus a larger ice maker performance with the same size of the ice generator. Through the Possibility of free design of the pipe cross section can also be the flow in the tubes 2 and Optimize jacket space 6.

Figures 4 and 5 finally show schematically two embodiments of an ice generator, in which the pulsating flow of the coolant as a drive is being used. In both embodiments, of course the pipes 2 and the stripping elements 1 as in the previous examples.

Both embodiments have a tube bundle heat exchanger with a container 5 in which several Pipes 2 are arranged parallel to each other. In both Figures are the inlet 7 and the outlet 8 for the Mantle space 6 evaporating refrigerant and in the Pipe stripping devices shown schematically 1 recognizable. The aqueous coolant flows through the tubes 2 in these examples correspondingly provided openings at the tube ends of left to right, as indicated by the arrows.

The tube bundle heat exchanger is preferred however stored upright, being from the aqueous Phase is flowed from bottom to top. hereby the ice discharge with the flow through the buoyancy which supports ice crystals.

The stripping devices 1 occur at one end of the tube bundle out of the tubes and are at one Tube plate 9 attached. The tube sheet 9 is vibratable by means of springs 11 relative to the tubes 2 stored. If there is a pulsating Flow of the aqueous entering the ice generator Refrigerant and the ice-water suspension emerging from the pipes (Ice slurry) becomes the tube plate 9 due to the pulsation of the flow to vibrations excited on the stripping 1 transfer. The stroke generated in this way depends on the one hand of the flow properties and on the other hand of the Design and the vibration properties of the Bottom plate 9 and can be targeted by the latter to adjust. When using vibratable Coil springs as wipers Wiping effect additionally reinforced.

The scraped off from the pipe wall in this way Ice crystals become with the flow from the ice generator discharged.

In the embodiment of Figure 4 is the tube sheet 9 provided with holes 10 which with the The outlet openings of the pipes 2 are aligned.

The tube sheet plate 9 can also be used with non-aligned Bores 10 may be provided, as in Figure 5 is shown as an example. At this Design increases the forced flow diversion the pressure on the base plate 9 so that the force on the stripping devices 1 is increased.

However, it can also completely drill holes can be dispensed with in the base plate 9. Here will the diameter of the tube plate 9 is reduced, so that the aqueous coolant through the resulting Gap between the base plate 9 and the side walls of the Ice generator can flow. This also increases the Pressure on the tube sheet in comparison to the embodiment Figure 4. A combination of these Design variations of the base plate are a matter of course also possible.

The simple structure, the low cost and the less space requirement of the ice generator according to the invention represent significant benefits that the Development of new areas of application for water-ice suspensions enable in the future.

Claims (9)

1. Ice generator for the production of an aqueous ice-crystal suspension, comprising

   a heat exchanger having a plurality of pipes (2) for an aqueous cooling agent, which run approximately rectilinearly beside one another in a container (5) for a refrigerant, and

   a mechanism for removing ice deposited on internal walls of the pipes (2), the mechanism comprising wiping devices (1) in the pipes (2) and a drive for the wiping devices (1), and the wiping devices (1) being formed of wiping elements which are connected to one another along the pipe axes and whose circumference substantially corresponds to the internal circumference of the pipes (2), characterized in that the wiping devices (1) have a central passage for the cooling agent and the drive (9) is configured for the repeated reciprocating movement of the wiping devices (1) along the pipe axes.
2. Ice generator according to Claim 1, characterized in that the wiping devices (1) have the shape of a helical spring, one turn of the helical spring corresponding to one wiping element.
3. Ice generator according to Claim 1, characterized in that the wiping elements (1) are arranged at the same mutual spacing along the pipe axes.
4. Ice generator according to Claim 1 or 3, characterized in that the wiping elements (1) have the shape of rings (3) or discs, which are connected to one another by one or more connecting elements (4) running along the pipe axes.
5. Ice generator according to one of Claims 1 to 4, characterized in that the wiping devices (1) are formed resiliently along the pipe axes.
6. Ice generator according to one of Claims 1 to 5, characterized in that the pipes (2) have an elliptical internal circumference.
7. Ice generator according to one of Claims 1 to 6, characterized in that the drive is configured to produce a periodic reciprocating movement.
8. Ice generator according to one of Claims 1 to 7, characterized in that the drive comprises a plate (9) to which the wiping devices (1) are fixed, the plate (9) being arranged at one end of the pipes (2) and being mounted such that it can oscillate with respect to the pipes, in such a way that it can be set oscillating by means of a pulsating flow of the cooling agent entering the pipes or emerging from the pipes, in order to produce the reciprocating movement.
9. Ice generator according to Claim 8, characterized in that the plate (9) has openings (10) for the passage of the cooling agent.

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