Patent Application
20080314070
The invention concerns sorption cooling elements with a gas-tight film for cooling containers, in which cold is generated by the evaporation of a working medium and sorption of its vapor in a sorption agent under a vacuum, and a method for producing and for starting these cooling elements.
Adsorption devices are apparatus in which a solid adsorption agent sorbs a second lower boiling agent, the vapor working agent, while releasing heat. The working agent in this case evaporates in an evaporator while absorbing heat. After the sorption agent has become saturated, it can again be desorbed by supplying heat at higher temperatures (desorption phase). In doing so, the working medium evaporates from the adsorption agent. The working medium vapor can be re-liquefied and then evaporated anew.
Absorption devices are apparatus in which a liquid absorption agent is used. Both adsorption and absorption systems fall under the term “sorption devices.”
Adsorption apparatus for cooling with solid sorption agents are known from EP 0 368 111 and DE-OS [Offenlegungsschrift Patent Application] 34 25 419. Sorption agent containers filled with sorption agents take up the working agent vapor, which arises in an evaporator, and sorb it while releasing heat. This heat of sorption must then be withdrawn from the sorption agent. The cooling apparatus can be used to cool foods and to keep foods warm in thermally insulated boxes.
WO 01/10738 A1 describes a self-cooling beverage can in which an evaporator is arranged within and a sorber is arranged outside of the can. Cooling is initiated by opening a vapor channel between the evaporator and the sorber. The cold generated in the evaporator is given up via its surfaces to the beverage that is to be cooled within the can. The heat that arises in the sorption agent is stored in a heat buffer. The self-cooling beverage can is highly modified by comparison with an ordinary can and is expensive to make.
Other theoretical designs of self-cooling packaging are summarized in WO 99/37958 A1. None of these devices is cheap to make.
Finally, U.S. Pat. No. 6,474,100 B1 describes a self-cooling element on the outside of a pouch for liquids or bulk goods. The sorption agent in this case is enclosed in a flexible, multilayer film. Contact via the hot sorption filling is reduced to a minimum by insulation and wicking materials and by heat storage masses lying in between. The temperature balance between the hot sorbent filling and the cold evaporator, which face each other over a large area, must be reduced by expensive insulation.
The task of the invention consists of inexpensive, flexible sorption cooling elements, and a method for making them.
This task is solved by the characterizing traits of Claim 1. The dependent claims point to other inventive devices and methods.
In accordance with the invention, the sorption agent and the evaporator are surrounded by a multilayer film. The evaporator contains a nonwoven material and a flexible, vapor-permeable structure material, which together under vacuum have a flat, but flexible geometry that can easily be pressed against any container that is to be cooled. After the initiation of the cooling element the structural material guides the working agent vapor to the sorption agent and leaves open a flow cross section of at least 1 cm2 for the working agent vapor.
Through the use of a low-cost structural material on the one hand, a flexible construction of the evaporator can be realized, one that can optimally be matched in particular to cylindrical geometries, and on the other hand the necessary flow channel from evaporator to sorption agent can be realized in the required cross section. To achieve sufficiently rapid cooling, the flow cross section must have an area of 1 square centimeter (cm2). If water is used as the working agent, a refrigerating capacity of more than 20 watts can be generated.
The multilayer film necessary for the gas-tight vacuum envelope holds all of the components necessary for operation and the storage time. If necessary, it can be made in a single piece and the inner flexible components ensure the required freedom of motion under vacuum. Storage times of over a year are possible with an aluminum shutoff layer in the multilayer film without too great an amount of gas diffusing through the film during the storage time.
For rapid cooling of a liquid in a container in accordance with the invention, the evaporator surface of the cooling element is pressed against the outer surface of the container. The evaporator is designed to be flexible for this and the cold evaporator surface is pressed flat against the outer surface of the liquid container by means of a separate elastic pressure means in order to utilize a large portion of the sometimes highly structured surface of the container for heat exchange.
Adhesive tapes, stretch or shrink films, as well as rubber bands or hook-and-loop closures of any kind, for example, are suitable as pressure means. With this solution it is advantageous that the liquid container can remain partially visible and the cooling element does not have to be opened or removed in order to pour the liquid out. When the cooling element is placed against the container, care must be taken that the heat transfer between the outside of the container and the evaporator surface is not unnecessarily adversely affected by gaps and folds.
Container is understood to mean all conventional vessels such as bottles, cans, drums, pouches, pots, cardboard packages, etc., that are used to hold liquids such as beverages, medications or even chemical products. Of course, the container can also contain solid or bulk products. Basically speaking, the container does not need to be modified from its usual shape and design. Thus, all previously used manufacturing and filling devices can continue to be used without modification.
In principle, the evaporator can have any shape and can be made of any material. During the cooling process it is technically necessary that there be an opening sufficiently large for outflow of the water vapor into the sorption agent, the working agent remain in liquid state at the site to be cooled, entrainment of liquid components into the sorption agent be prevented and that a good thermal connection to the object to be cooled remain.
Especially low-cost cooling elements can be achieved if all of the components are welded together into one-and-the-same gas-tight film. Under vacuum, the flow channels to the sorption agent must continue to exist. For this a vapor-permeable structural material is provided that lets the working agent vapor flow unhindered from the liquid amount of working agent and, at the same time, due to its flexibility, that allows the cold evaporator regions to be in good heat-conductive contact with the outer multilayer film in accordance with the invention.
Flexible structural materials of plastic that are matched to the relevant cooling job can be advantageously used for this. However, a prerequisite is that during the storage time the structural materials do not outgas and thereby degrade the vacuum. It is advantageous if polycarbonate or polypropylene is used as the plastic, since these materials were heated to higher temperatures before or during the manufacturing process and in so doing were degassed.
Structural materials of plastic can be produced at low cost by conventional manufacturing processes like deep drawing, extrusion or blow molding. Value is added by the fact that no substances that outgas later such as plasticizers or dyes are added in the manufacturing process. Also, extruded networks and lattices of polypropylene have proved to be particularly efficient; used in single or multiple layers, these ensure, for one thing, the required flexibility with regard to deformation and, for another, the stiffness with regard to the air pressure applied from outside via the multilayer film. Especially suitable structural materials of polypropylene are sold by Tenax Germany. The product OS 102 is a diamond lattice, which leaves open ideal geometries for the working agent vapor flowing in the plane of the lattice and supports the multilayer film lying on the outside. Two-layer and multiple-layer lattices can be used as structural material with particular advantage.
Sorption agents can reach temperatures of over 100° C. in the sorption process. The multilayer films that are usually used in the packaging sector are less suitable for such high temperatures. In particular, the polyethylene layers that are often used for sealing already become soft at 80° C. and let the envelope become leaky under vacuum. On the other hand, sealing layers of polypropylene can withstand clearly higher temperatures. Their melting point is over 150° C.
In combination with high temperatures, the sharp edges, corners and sharp tips of the sorption agent granulate can generate impermissible leakages. In accordance with the invention, this danger can be combated by means of polyamide and/or polyester layers within the multilayer film. Polyester and polyamide films are especially tear-resistant and puncture-resistant. The actual gas shutoff is established by a layer of thin metal films or metallized layers. For this, thin aluminum foils with a layer thickness of about 8 μm have shown merit. Metallized plastic film are less gas-tight. Nevertheless, for short storage periods, the use of these metallized films is also possible, particularly since they can be made more cheaply than the metal films.
The individual layers of a multilayer film are bonded together by adhesives. Commercial adhesives contain solvents that are not completely removed from the adhesive layer in the gluing process. Over longer periods of time, these solvents then diffuse through the inner layers, especially the polyethylene layer, and have an adverse effect on the vacuum within the cooling element. Diffusion increases at higher temperatures, such as arise in the sorption process and the manufacturing process of the cooling elements. The adhesives that can be used therefore must be designed both for high temperatures and vacuum.
In accordance with the invention, multilayer films with polyester or polyamide layers from 12 to 50 μm thick, an aluminium layer of 8 μm thick and a polypropylene layer of 50 to 100 μm thick can be used. Such films are used, for example, for packaging foods, which are sterilized after packaging at temperatures over 120° C. in order to make them keepable.
Still more stable multilayer films are obtained if an additional approximately 15 μm thick polyester or polyamide layer is bonded between the aluminum and the polypropylene layer. Then sharp or pointy sorption agent particles cannot then penetrate to the gas barrier, the aluminum layer.
Multilayer films in accordance with the invention can be obtained, for example, from Wipf A G in Volketswil, Switzerland. Cooling elements with a leakage rate less than 1×10−7 mbarl/sec are possible when using such films. With that the storage capacity reaches several years without a reduction in the refrigeration effect.
The welding of multilayer films to pouches and filling them with bulk material as well as the subsequent evacuation are prior art in the food industry.
Pouches in a wide range of sizes and shapes are in use for this. One may mention in particular here, stand up pouches, pouches with a pouring spout, pouches with cardboard reinforcement, tear-open pouches, pouches with peel effect for easier opening and pouches with valves. With their specific properties, they can all be of advantage for the cooling elements in accordance with the invention.
When solid sorption agents are filled into pouches, dust forms and can deposit on the inside of the film. Dust on the subsequent welding sites may lead to leakages if the dust layer is too thick by comparison with the polypropylene layer. Polypropylene layers that are 50-100 μm thick are sufficient to melt fine dust particles into the polypropylene layer reliably and vacuum tight.
When using films in accordance with the invention, it is possible to envelope hot, sharp-edged and dust-releasing sorption agent directly under vacuum without additional protective intermediate layers and to store them over a period of several years, without foreign gases getting into the cooling element from the film material itself or passing through it, which can adversely affect the sorption reaction or even suppress it entirely. The sealing seams here should have a width of at least 5 mm, with 10 mm being even better.
Zeolite can advantageously be used as sorption agent. In its regular crystal structure, it can reversibly sorb up to 36% by weight water. When used in accordance with the invention, the technically realizable water uptake amounts to 20 to 25%. Even at relatively high temperatures (over 100° C.), zeolites still have a considerable water vapor sorption capacity and therefore are particularly suitable for use in accordance with the invention.
Zeolite is a crystalline mineral that consists of a regular framework structure of silicon and aluminium oxides. This framework structure contains vacant spaces in which water molecules can be sorbed while releasing heat. Within the framework structure, the water molecules are subjected to strong field forces, the strength of which is dependent on the amount of water already contained in the framework structure and the temperature of the zeolite.
Natural types of zeolite that occur in nature absorb clearly less water. Only 7 to 11 g water is sorbed per 100 g of natural zeolite. This reduced water absorption capacity is due on the one hand to their specific crystal structures and on the other hand to nonactive contaminants in the natural product. For this reason synthetic zeolites with their greater sorption capacity are preferred for cooling elements that also have the capacity of giving up the heat absorption via the envelope during a lengthy cooling period. For cooling elements with high refrigeration capacity and/or short refrigeration time, in which the sorption agent remains relatively hot, it is also possible to use natural zeolites in accordance with the invention. Specifically, synthetic zeolites are no longer advantageous over the natural ones in the case of high sorption agent temperatures. Typically, both types of zeolites can sorb only 4 to 5 g water vapor per 100 g dry sorption agent weight when there is limited release of the heat absorption and the accompanying high sorption agent temperatures of over 100° C. In this case the natural representatives even have an economic advantage, since their price is considerably lower.
Natural zeolites have still another advantage. The nonactive contaminants typically make up 10 to 30% of the zeolite. They do not actively participate in the generation of cold, but nevertheless they become heated by the adjacent zeolite crystals. They thus act like an additional built-in low-cost heat buffer. The result is that the zeolite filling does not become as hot and thus can sorb additional water vapor at lower temperatures.
A natural zeolite granulate consists of broken or crushed fragments and thus has sharp and pointed geometric shapes that can puncture or cut through the envelope under vacuum and at elevated temperatures.
With zeolites there is also the danger that, in each case according to the synthesis process, occurrence, and decomposition process, they will contain admixture components that give up gaseous components in a vacuum and especially at higher temperatures, and these gaseous components can affect the cooling process.
This problem of gas release is solved by heating the zeolites at least to the subsequent sorption agent temperature before making the cooling element and at the same time subjecting them to the vacuum that will prevail then. With this procedure, zeolites in accordance with the invention can give up their problematic components. This thermal treatment is especially efficient if the presorbed water can be evaporated out at the same time. To be able to conduct this treatment at elevated temperatures and to be able to withstand the sharp edges and sharp tips, in accordance with the invention gas-tight multilayer films with an inner polypropylene layer and at least one polyester layer are used. Hot sorption agents can also be filled into these films.
Among the approximately 30 different natural zeolites, the following can be advantageously used for the cooling elements in accordance with the invention: clinoptilolite, chabazite, mordenite and phillipsite. They are very common, are inexpensive to process, and have a sufficiently rapid sorption characteristic.
Substances that occur in nature can also be returned to nature without environmental considerations. After they have been used in cooling elements, natural zeolites can be used, for example, as soil amendments, as liquid binders or to improve the water quality in ponds and other bodies of waters.
Of the synthetic zeolites types A, X and Y, each in the low-cost Na form, are used.
Besides the combination of zeolite and water, other solid sorption agent pairings are also possible for use in cooling elements in accordance with the invention. One may mention in particular bentonites and salts, which likewise represent combinations that are appropriate with water as the working agent. Activated carbon in combination with alcohols can also offer an advantageous solution. Since these substance pairs work even at reduced pressure, they can be welded into multilayer films in accordance with the invention.
In accordance with the invention, the amount of sorption agent should be dimensioned and arranged so that only a minimal pressure drop has to be overcome within the sorption agent for the incoming water vapor. Here, the pressure drop should be less than 5 mbar, especially if water is used as the working agent. Moreover, the sorption agent must offer sufficient surface for storage to the flowing working agent vapor. Sorption agent granulates in particular have shown themselves able to ensure uniform sorption within the sorption agent and a low pressure drop. Granulate diameters between 3 and 10 mm show the best results. These can be packed in film pouches without any problem. After evacuation, they form a hard, pressure-resistant and shape-stable sorption container that retains the shape imposed in the evacuation process. However, stable zeolite blocks that have been preformed from zeolite powder, in which the flow channels are already built-in and the shape of which is matched to the desired cooling element geometry are also advantageous. The stable zeolite blocks can have vacant spaces in the region of the subsequent vapor opening that facilitate the penetration of the film using a cutting tool and can accept the separated piece of film so as not to hinder flow through the vapor channel.
In the sorption reaction, heat absorption is released and heats the sorption agent. The capacity for absorption of working agent drops off sharply at higher sorption agent temperatures. To be able to maintain high refrigeration capacity over a longer period of time, it is important to cool the sorption agent.
If there is direct contact between the sorption agent and the multilayer film, heat absorption that develops can be dissipated outwardly through the film. As a rule, the heat is given up to the surrounding air. It is also very efficient to cool the sorption container by means of liquids, especially water.
Since the heat transfer to a flow of air from the outside of the multilayer film is of the same order of magnitude as the heat transfer of a sorption agent granulate to the inner side of the film, in principle large film surfaces without fins are recommended, for example cylindrical, plate or tubular geometries. Since zeolite granulates in particular have low thermal conductivity, the sorption containers should be designed so that the average heat conduction path within the sorption agent does not exceed 5 cm.
Using cooling elements in accordance with the invention, the chilling of a 0.75 L champagne bottle from 25° C. to 10° C. can take place within a period of 30 minutes, for example.
After manufacture, the cooling elements can be stored at room temperature for an indefinite period of time. The shutoff device is activated at the starting point of the cooling effect. Starting at this time, the working agent vapor can flow to the sorption agent and be taken up by it. The sorption agent becomes hot since it liquefies and stores the vapor within its crystal structure. Through the evaporation, the evaporator cools and withdraws sensible heat from the liquid container via the outer jacket. During the relatively short cooling period it will not be possible to cool the sorption agent to a significant degree. The capacity for absorption of working agent vapor will therefore be limited if admixture components do not function as a heat buffer.
If a longer refrigeration maintenance time follows the rapid cooling of the contents of the bottle, the sorption agent will also be able to give up heat through the multilayer film.
In accordance with the invention, in these applications the heat of sorption at a higher temperature level can also be transmitted to a product that is to be kept warm.
To minimize the heat flow from the hot sorption agent to the cold evaporator, either insulation materials are provided or care is taken in accordance with the invention to provide sufficient spacing between the two components.
Thermal insulation of the evaporator surrounding the liquid container is also a desirable objective. If the container and the evaporator are not insulated from the ambient air, condensation of water vapor from the air onto the cold surfaces can occur. For one thing, moisture that precipitates between the container and evaporator can improve the heat transfer from the container to the evaporator, but on the other hand a considerable portion of the cooling capacity for the condensation is lost.
In accordance with the invention, the cooling elements can be divided into structural types A and B with regard to their shutoff device:
A: The working agent is already contained in the evaporator nonwoven. To start the cooling effect, the vapor channel from evaporator to sorption agent is opened, for example, by rupturing a sorption agent pouch that contains the sorption agent and is arranged within the multilayer film.
B: The working agent is situated outside the evaporator nonwoven. To start the cooling effect, a working agent connecting line from a working agent pouch to the evaporator is opened; for example, by puncturing the working agent pouch and squeezing the working agent out into the evaporator.
In the first instance (A), either a valve must be connected between the evaporator nonwoven and the sorption agent region, or the sorption agent must be situated within an additional multilayer film pouch, which must be opened in the direction of the evaporator to start the cooling function. Sharp-edged cutting tools that puncture a sufficiently large opening in the sorption agent pouch are suitable for this. The cutting tool in this case can act on the film both from the sorption agent side as well as from the evaporator side. Since the films in accordance with the invention are flexible, the cutting tool in accordance with the invention is actuated by a change of shape produced on the multilayer film from outside. With that, all shutoff devices can be made cheaply and actuated in a gas-tight way.
In principle, the cutting tool must be sharp enough to cut through the film in the necessary cross section. For example, cylindrical expanded metals or sharp-edged molded parts of plastic that are also additionally able to pinch or shift the sorption agent situated behind the film in order to cut through the film in a large area are suitable. In order to cut a sufficiently large opening, at least 1 cm2 in size, using the cutting tool, it is possible, for example, to use a rubber hammer to strike the multilayer film covering the cutting tool.
In the second case (B) only a small opening need be made in the working agent pouch and a connecting line must be provided for the still-liquid working agent to go to the evaporator nonwoven.
In accordance with the invention, additional liquid working agent can be filled into the surrounding multilayer film in the appropriate amount and in a connecting channel. The connecting channel can in accordance with the invention be sealed by the surrounding multilayer film being folded in this region one or several times, so that its sealing layers lie tightly against one another. Together with the air pressure applied from outside pressure, this measure provides a sufficient seal between the liquid working agent and the evaporator nonwoven. To make the opening, one merely needs to refold the enveloping multilayer film back to the original flat form in the channel region and partially squeeze the working agent into the evaporator by additional pressure on the working agent pouch.
Another advantageous embodiment is obtained if a working agent pouch filled with the required amount of work agent is placed between the multilayer film inside or outside the evaporator region. This pouch can be burst by outside pressure on the multilayer film in the region of the pouch so that the liquid working agent escapes into the evaporator nonwoven. Bursting via outside pressure can take place either through the use of a film with peel effect or by putting a pointed opener in the working agent pouch. In a completely filled working agent pouch the pointed opener cannot press against the film and perforate it during storage. Only through the effect of an additional external force in the region of the opener will the liquid working agent be displaced so that the pointed opener can puncture a small opening in the film. If the working agent pouch is made of a film with peel effect, a separate opener can be omitted since the sealing seam can be made to leak and let the contents flow out by vigorous force on the pouch due to the peel effect. The physical rupture properties of the peel-seal seam can be tailored to the requirements of the working agent pouch. Here, one must ensure that the air pressure applied from outside does not burst the pouch, but the pouch lets the contents flow into the evaporator when appropriately high finger pressure is applied. The connecting channel to the evaporator, which can be of any length and can be optimally matched to the relevant geometries that are present, can be held open by a narrow strip of structural material or a flexible plastic tube.
In accordance with the invention, the adsorbable amount of working agent can be held in more than just one single working agent pouch. This gives the possibility of being able to use a cooling element for cooling more than once by opening just one working agent pouch each time. This is of particular advantage in the case of cooling tasks that have high cooling capacities. Due to the high adsorption power, the heat of adsorption in this case cannot be withdrawn from the sorption agent sufficiently rapidly. The adsorption capacity can thus not be fully utilized. However, if the sorption agent has recooled after the first cooling process, it can again adsorb the working agent. For this, a second (or additional) working agent pouch can in turn be opened any time and deliver its contents to the evaporator nonwoven. Each working agent pouch in this case is filled only with a partial amount of the amount of working agent that can maximally be adsorbed by the sorption agent.
In the last embodiments, the evaporator together with the sorption agent can be put into a single multilayer film that surrounds the whole. Only when the liquid working agent advances from the working agent pouch to the evaporator can it evaporate from there and flow further to the sorption agent in vapor form.
The advantage of this shutoff device lies in the fact that only a relatively small flow cross section is required for the liquid working agent. On the other hand, it is disadvantageous that the working agent has to wet the evaporator homogeneously and sufficiently rapidly without being entrained in liquid form into the sorber or even without freezing up at the outlet from the opening of the working agent pouch and thus blocking further flow.
In accordance with the invention, water as the working agent can be kept from freezing by adding an agent that lowers the freezing point. Adding common salt can reduce the freezing point to −17° C., for example. It is also helpful if the freezing point-lowering agent is arranged outside of the working agent pouch, around the outlet opening. Then the water will mix with the freezing point-lowering agent in a high concentration only when it leaves the opening. This prevents the solidification. Water moving in the wake will then dilute the solution and transport the working agent into all regions of the evaporator.
Homogeneous distribution of the working agent can also be achieved in accordance with the invention by a separate, finely branched channel structure that distributes the working agent homogeneously after it flows out from the working agent pouch before it can be entrained in liquid form by the vapor flow. A low-cost distribution can be achieved, for example, by a layer of film with fine perforations that is arranged around the outlet orifice.
An especially efficient, and at the same time low-cost, solution is achieved when the liquid working agent becomes homogeneously distributed in the evaporator nonwoven by the structural material of the vapor channel. For this, after opening the working agent pouch, the working agent is pressed out into the structural material by excess pressure applied to the multilayer film from outside. Here, a part of the working agent evaporates and entrains the still-liquid working agent at high speed. If the structural material is shaped in accordance with the invention, the liquid working agent is repeatedly deflected on the path toward the sorption agent and continues to be thrown against the adjacent nonwoven material. This material absorbs the liquid components of the working agent and secures it from the working agent vapor that is flowing by. In this way, the evaporator nonwoven becomes homogeneously wetted with the optimum amount of working agent in the shortest time. The transport of the liquid working agent consequently takes place not within the evaporator nonwoven, but rather via the vapor channel within the structural material. Advantageously, the evaporator becomes flooded from below with the liquid working agent while the pure working agent vapor flows out from the evaporator above. However, the evaporator does not necessarily have to stand upright. However, in accordance with the invention the feed of the liquid working agent takes place from the one side and the exit of the working agent vapor takes place from the opposite side. The amount of the evaporator nonwoven should be matched to the volume of the liquid working agent. At the end of the outflow operation, the area of the evaporator nonwoven that is in contact with the container should have absorbed the necessary amount of working agent.
The working agent is fixed in the evaporator nonwoven by hygroscopic effects. Especially cheap nonwoven materials are absorbent papers, such as are used in great diversity for the absorption of liquids for home and industry. Also, the water-storing nonwovens, such as the spacers of plastic or natural zeolite, must not outgas under vacuum and at higher temperatures.
Especially absorbent nonwovens consist of polypropylene microfibers. Provided with special wetting agents, they can absorb and hold several times their own weight in water. Sandler A G, Schwarzenbach, Saale, offers the corresponding nonwoven materials under the product name Sawadry 8313.
Another solution is revealed by securing the working agent in organic binders such as “Water Lock” from Grain Processing Corp. USA. The combination of more than one of these measures can also be advantageous.
To produce cooling elements in accordance with the invention by shutoff valve variation A, a sorption pouch open at one side is produced by thermal welding, for example, from a multilayer film. The sorption agent pouch is filled with sorption agent, which is low in working agent and does not contain gases that can escape and the pouch together with the film is put into the desired geometric shape, evacuated to less than 5 mbar and especially to less than 2 mbar and weld-sealed gas-tight. Then the sorption agent pouch under vacuum, together with a shutoff device, a structural material and an evaporator nonwoven that is soaked with working agent, is packaged in another envelope pouch of multilayer film. The envelope pouch is then evacuated in a vacuum chamber to the vapor pressure of the working agent and then likewise sealed gas-tight. When inserting the shutoff device, care should be taken that its orifice device has not already been triggered when air is admitted into the vacuum chamber.
When using separate working agent pouches (shutoff device variation B), the manufacturing process can be slightly modified. The structural material, the nonwoven and the working agent pouch or pouches are put into specific positions in a multilayer film pouch. In this variation, too, the geometry is matched to the container that is to be cooled before evacuating the evaporator region. Then hot adsorption agent is added and the multilayer film pouch is evacuated and sealed either in the vacuum chamber or by means of a suction adapter.
As a rule, the sealing of the film pouches takes place by pressing hot welding bars against the outer film surfaces until the inner polypropylene layers become soft and melt together. As a rule, the sealing operation takes place in a vacuum chamber under vacuum. However, it is also advantageous to evacuate the pouch outside of the vacuum chamber by means of a tight-fitting suction adapter and then to seal it. Besides thermal contact processes, welding methods using ultrasound are also tried and true. Advantageously, the sealing seam has a width of at least 5 mm, and 10 mm is still better. The wider the sealing seam, the lower the leakage rate and consequently the longer the potential storage time of the cooling element.
In the drawings:
One end of the network lattice strip 3 projects from the still-open edge 9. The second end fits into the structural material two (not visible). Between, is the working agent pouch 4 (likewise not visible). The network lattice strip 3 can have nearly any length in order to position the working agent pouch or pouches 4 at a distance from the evaporator region. If the distances are longer it is also possible to use a thin flexible strip 2 instead of the network lattice strip 3.
In
In
Finally,
The cooling element 21 is evacuated in a vacuum chamber to an end pressure of less than 5 mbar (absolute) and the still-open pouch sides are sealed. After removal from the vacuum chamber, the pouch corners 26, which stand in the way of activating the tap, are additionally sealed and then cut off. The cooling element 21 can now be rotated in any position and shaped in accordance with the invention without the zeolite filling 33 (and the incorporated components) leaving their intended positions.
| Number | Date | Country | Kind |
|---|---|---|---|
| DE 102007028559.2 | Jun 2007 | DE | national |
| DE 102007050134.1 | Oct 2007 | DE | national |
