EVAPORATIVE COOLING

FIELD OF THE INVENTION

The present invention relates to a method of cooling products, an apparatus for cooling products and a system comprising such apparatus.

BACKGROUND ART Numerous types of foods, including beverages are packed or bottled as a hot-fill product. Also, in food technology, one frequently used method of increasing the shelf life of food products, including beverages, is pasteurization. Pasteurization is normally made after the food product has been packed in its container, which container by way of example can be a flexible pouch, a box, a bottle or a tin can. During pasteurization, the container with its contents is heated to a temperature in the range of 70-95 ^° C to kill any pathogenic micro organisms while the contents as such are left more or less non- affected.

Generally it is highly desirable to cool the hot containers or naked not packeted heat-treated products quickly. One reason is that some foods can degrade if they are not cooled quickly due to overcooking, bacterial action or due to chemical reactions, sometimes with the container. Another reason is that without quickly cooling the containers, the containers would have to be stored and removed from storage prior to labelling, which is highly inefficient. Prior art methods of cooling containers often contain multiple cooling zones where each zone uses coolants of different temperatures. One such method is disclosed in US 2007/0079618. The method includes spraying coolant onto the containers and decreasing the flow rate of coolant as the average temperature of the hot contents decreases. More precisely, the spraying is made as the containers are conveyed along a conveyor passing at least three different zones and most preferably at least six different zones. Each zone has a predetermined coolant flow rate or spray density with the coolant flow rate decreasing in each downstream zone as compared to the upstream zone or zones. The coolant is at least about 22 ⁰ C cooler than the initial average temperature of the hot contents.

This prior art method is less favourable as regards to the energy consumption since the coolant is required to be specially tempered for each zone, no matter if the coolant is fresh or re-circulated. This also makes the

apparatus complex and expensive. Also, the apparatus tends to be bulky and space requiring. Another drawback is that the method requires large volumes of coolant which means that the method is less favourable to paper or fiber based containers. Yet another drawback is that the large volumes are less favourable to naked products.

OBJECT OF THE PRESENT INVENTION

The object of the present invention is to provide a method, an apparatus and a system for cooling.

Such method, apparatus and system should provide a careful treat- ment of the containers.

The method, apparatus and system should allow cooling by using a minimum of energy consumption as regards to coolant consumption and required tempering of the coolant.

The method, apparatus and system should be simple in terms of con- struction and space saving.

Said method, apparatus and system should not only be applicable to containers but also to naked products before packeting.

SUMMARY OF THE INVENTION

To achieve at least one of these objects and also other objects that will be evident from the following description, the present invention refers to a method, an apparatus and a system for cooling containers.

The term product should in the following disclosure of the invention be interpreted as to include naked, not yet packeted, products as well as containers. Examples of naked products are boiled or steamed vegetables. The term container relates to any type of container used for food products no matter its consistency, such as a flexible pouch, a package, a box, a bottle or a tin can, and especially the type of containers used for pasteurized or otherwise heat treated food products. The term container is not to be limited to containers of any special type of material. More specifically, according to a first aspect the invention refers to a method of cooling products, comprising the steps of continuously transporting the products on a conveyor in a vertical direction from an inlet to an outlet, spraying water and blowing air onto the products during said transportation, said air removing water evaporating on said products, and regulating the speed of the conveyor, the flow of water and the flow of air supplied onto the products, so that the outlet temperature of the products is reduced to be lower

than the inlet temperature thereof and the outlet temperature of the water is the same as or reduced to be lower than the inlet temperature thereof.

By said method heat treated products can be cooled in a very time efficient, cost effective and energy-saving manner. In case the products treated are containers, the containers can be filled containers of any type and of any material and with any contents that have undergone a prior heat treatment. The method can be applied in a conventional conveyor being supplied with means for spraying water and blowing air onto the products transported.

By spraying water a mist is formed which meets the surface of the hot products entering the inlet. When the mist meets the hot surface it is evaporated. During said evaporation energy is consumed, partly from the water being sprayed, partly from the hot products and their contents. By the energy consumption, the products are evaporative cooled as they are continuously transported in the vertical direction from the inlet to the outlet. The consumed energy is disposed by air being blown onto the products, blowing away the evaporated water from the products and out of the encapsulation or housing that normally is surrounding the conveyor. By the products being subjected to both water and air, the cooling occurs by evaporation as well as convection and conduction. The fact that energy is consumed is shown by the outlet temperature of the products being reduced to be lower than the inlet temperature thereof and the outlet temperature of the water being the same as or reduced to be lower than the inlet temperature thereof. Trials have shown that the inlet temperature of containers having a temperature of 70-95 ⁰ C at the inlet in theory can be cooled to an outlet temperature of 14 ⁰ C and in practice to 20-35°C by using an air inlet temperature of 25 ⁰ C and a relative humidity of 50%.

It is to be understood that these exemplified temperatures are a result of by way of example the dwell time regulated by e.g. transportation speed and length of the conveyor. By the products being transported in the vertical direction, the required floor space can be reduced. Further, by the water being sprayed, the water consumption is very limited as compared to prior art equipment. In fact, since only a water volume sufficient to create a mist is required, said volume can be reduced to a couple of litres per minute. This is in direct contrast to prior art wherein the products are more or less drown in water being flushed over the products. Such drowning can be equalled with a surface insulation preventing cooling of the products. By instead only forming a mist, only a thin layer of

water is formed on the product surface. The amount of water being sprayed onto the products can be balanced so that the water mist meeting the hot surface is immediately evaporated and removed by the air flow.

The air blown can be the ambient air at room temperature being circu- lated. Thus no tempering is required.

Also, said method is very careful as regards to the products since the amount of water sprayed onto the products is very low as compared to prior art. This means that paper or fiber-based containers can be used without risking wetting damages. By the limited amount of water and the efficient extrac- tion of water by the blown air, there is in practice no need for intermediate storage of the containers prior to any labelling. Also, in case of naked products, there is no risk of these being damaged by an abundant water supply.

Surprisingly, it has been noted that the present method is very suitable for cooling containers with high viscous products, such as tomato products, which products normally are hard to cool due to their high viscosity. Cooling normally creates a small turbulence in the contents, enhancing the heat transfer and thereby the cooling. However in high viscous products this turbulence is hard to create. By the present method using a combination of convection and conduction, a more efficient cooling effect has been observed. The inlet of the conveyor can be arranged above the outlet. However, it is to be understood that the opposite position can be used with remained function.

The method can be applied to products in the form of containers with their contents being pasteurized immediately prior to entering the inlet. Pas- teuhzation is a careful treatment to food products since the temperature applied to the container is well below 100 ^" C, normally 70-95 ⁰ C, whereby the killing of micro organisms is good and the impact of the properties of the contents is limited. Also, there is no pressure build-up in the container that may affect the geometry of the container. However, it is to be understood that the method is equally suitable applied to other prior methods of heat treatment of food products.

The water can be sprayed from the above onto the products. This means that the drops are descending by gravity.

In said method the air can be blown from the outlet to the inlet, oppo- site the direction of the water being sprayed. By said opposite flow, the evaporated water is blown away from the surface of the product, whereby energy in form of heat is removed from the products and their contents in

case of the products being containers. It is to be understood that the air can alternatively be blown in the same direction as the water being sprayed. The vapour can by way of example be disposed from the top of the stack, the water condensed and re-circulated in a return channel to the nozzles. The vapour can also be disposed from other positions.

The water can be sprayed with a flow volume per minute balanced as regards to the desired dryness of the products exiting the outlet. By using a flow value representing the ratio of the amount of water supplied and the amount of water evaporated, the dryness of the product exiting the outlet can be controlled. A flow value below one means that less water is supplied than can be evaporated, a value equalling one means that all water supplied is evaporated, and a value above one that more water is supplied than evaporated. By way of example, in case the product should be immediately labelled a dry product is preferred, whereas it in other situations can be irrelevant whether the product is dry or wet, and also whether the product is only humid or soaking wet. The amount of water supplied and thus the dryness of the product can be regulated based on a determination of the air humidity at the outlet.

The water and the air can be arranged to be sprayed or blown onto the products at different water or air supply zones along the path of the conveyor. The water and/or the air supplied can have different temperature in each such zone. Thus, the re-circulated water or any fresh supplied water can be used to temper the re-circulated water in such zones.

In order of reducing the water consumption, the water can be re-circu- lated. During re-circulation the water can be tempered and/or purified. In principle, the water can be tapped directly from the ordinary water supply system provided at the production facility.

The term purification is meant to include filtering but also other treatment of the water such as de-salting and de-calcination in order of avoiding clogging in the re-circulation system.

Also fresh water can be supplied to the re-circulated water. By adding an amount of fresh water to the re-circulated water, volume losses due to evaporation, "bleed off' and purification is compensated for.

The conveyor can form an endless helical path, whereby the floor space required, known as "foot print", in the production facility can be strictly limited due to the transportation being made generally in the vertical direction.

The conveyor can be a belt conveyor, however, it is to be understood that any other type of conveyor can be equally used.

The conveyor can be a self-stacking conveyor forming inner and outer walls. According to another aspect, the invention relates to an apparatus for cooling products, comprising an endless conveyor, which along part of its length follows a helical path to form a stack, said helical path defining a central space in the stack. The apparatus is characterized by nozzles for spraying water onto the products while transported on the conveyor from an inlet to an outlet of the apparatus and circulation means for blowing air onto the products to remove water evaporating on said products while transported on the conveyor, whereby the outlet temperature of the products is reduced to be lower than the inlet temperature thereof and the outlet temperature of the water is the same as or reduced to be lower than the inlet temperature thereof by regulation of the speed of the belt conveyor, the flow of water and the flow of air supplied onto the containers.

An apparatus in accordance with the preamble is known from US 3,398,651 , which apparatus comprises an endless conveyor, which along part of its length follows a helical path to form a stack, said helical path defining a central space in the stack. It is to be understood that also other types of apparatuses and conveyors can be used. The inventive apparatus benefits from the same advantages as the method previously discussed, whereby reference is made to the sections above relating to the method.

The inlet of the apparatus can be arranged above the outlet of the apparatus. However, it is to be understood that the opposite position can be used with remained function.

The air can be blown or sucked through the stack from the outlet to the inlet, opposite the direction in which the water is sprayed. By said opposite flow, the evaporated water is blown away from the surface of the products whereby energy in form of heat is removed from the products and their contents in case the products are containers. The evaporated water can be disposed from the top of the stack, the water condensed and the re-circulated via a return channel to the nozzles. Still, it is to be understood that the air can be blown or sucked in the same direction as the water being sprayed. The conveyor can have passages for letting the airflow in the vertical as well as in the horizontal direction through the stack. Accordingly, the outlets of the means for blowing air can be positioned in the central space as

well as in the annular space of the stack, while the air can be circulated onto the products transported on the conveyor and through the central space disposing the evaporated water from the apparatus.

The conveyor can be self-stacking for forming inner and outer walls of said stack. Such walls form an encapsulation that can either replace or supplement an external housing or encapsulation.

The nozzles for spraying water can be arranged at least at the inlet of the apparatus. In case the inlet is arranged above the outlet, this means that the sprayed water will descend by gravity onto the products towards the bot- torn of the stack.

The apparatus can comprise means for collecting and re-cycling water sprayed onto the products. Further, the apparatus can comprise means for tempering the water sprayed onto the products and means for purifying the water sprayed onto the products. Also, the apparatus can comprise means for supplying fresh water to said re-cycled water. The latter is to compensate for bleed-off.

Said conveyor can be a belt conveyor. However it is to be understood that any other type of conveyor can be equally used.

According to a third aspect, the invention relates to a system for cool- ing products, comprising an apparatus according to the second aspect of the invention, i.e. according to any of claims 15-25. The benefits with such apparatus have previously been discussed above, whereby reference is made to that section.

Said system can further comprise one or more of the following: a heat treatment apparatus supplying heat treated products to the inlet of the apparatus, a pasteurizer supplying pasteurized products in the form of containers to the inlet of the apparatus and a return channel re-circulating water sprayed onto the products.

DESCRIPTION OF DRAWINGS The invention will now be described in more detail by way of example and with reference to the accompanying drawings.

Fig. 1 illustrates one example of an apparatus for cooling products according to the present invention.

Fig. 2 is a schematic cross-sectional view of the apparatus and system in accordance with the present invention.

TECHNICAL DESCRIPTION

Fig. 1 illustrates the general design of one type of an endless conveyor, an embodiment on which the apparatus according to the present invention is mainly based. To facilitate the understanding of the conveyor no housing, nozzles for spraying water or means for blowing air onto the products are disclosed. Further, no products are disclosed.

The conveyor is formed by a belt conveyor 1 comprising a conveyor belt 2, which, in the manner illustrated, is adapted to follow along part of its length a helical path comprising a number of successive turns 4 to form a stack 3. The shown conveyor belt 2 comprises a number of mutually articulated links 5 and can run straight, through curves upwards and downwards and also sideways.

The links 5 comprise a bottom part 6 and at least one lateral piece 7b, which are arranged at the outer longitudinal edge of the conveyor belt 2. As shown, the links 5 may comprise one more lateral piece 7a at the inner longitudinal edge of the conveyor belt 2. The bottom part 6 constitutes a surface with some kind of perforation to allow water, water vapour and air to pass through. The bottom part 6 may consist of, for instance, a mesh or a perforated metal sheet. The links 5 are designed so as to allow a flow of water and water vapour both vertically and horizontally through the conveyor belt 2. This occurs through passages which may consist of, for instance, the play between two successive links 5, two successive turns 4 in the stack 3 or holes formed in the lateral pieces 7a, 7b. The vertical flow is ensured by the perforated bottom part 6.

The lateral pieces 7a, 7b of a first turn 4 in the stack 3 carry at least one longitudinal edge of a second turn 4' arranged on top of the first turn. This means that the conveyor belt 2 is self-stacking. The lateral pieces 7b at the outer longitudinal edge of the links 5 in the conveyor belt 2 thus form an outer cylindrical wall 8 of the stack 3 and, if there are lateral pieces 7a at the inner longitudinal edge of the links 5 in the conveyor belt 2, an inner cylindrical wall 9 of the stack 3. This results in an annular space 10 between the outer cylindrical wall 8 and the inner cylindrical wall 9. Furthermore, a cylindrical central space 11 is defined by the inner cylindrical wall 9. As an alternative to the inner cylindrical wall 9, the inner wall may comprise a wall (not shown), which is separated from the conveyor belt. Such wall may for instance be a wall formed from the outer periphery of a drum that

is used to carry the conveyor belt at its inner longitudinal edge in the stack. Such a wall comprises the previously described passages to allow a flow of water, water vapour and air in the horizontal direction between the central space and the annular space and vice verse. In addition to, or as an alternative or as a complement to said outer cylindrical wall 8, the conveyor can be arranged in a housing (not shown).

Also, the apparatus is provided with a drive means, which drive means, is schematically disclosed in Fig. 1 as reference number 40.

The annular space 10 is used as a duct for a flow of sprayed water, evaporated water and air over and around the products that are conveyed on the conveyor belt 2 in said space. Sprayed water and water vapour generally flows vertically through the annular space 10 from one turn 4, 4' to another 4, 4' included in the stack 3. Evaporated water and air may also flow horizontally between the annular space 10 and the central space 11. Accordingly, a verti- cal as well as a horizontal flow is permitted through the stack. This will later be discussed and disclosed in connection with Fig. 2.

Now turning to Fig. 2, a schematic cross-sectional view of one embodiment of a system including an apparatus 15 according to the invention is disclosed. The apparatus 15 is provided with an inlet 19 and an outlet 20 for transporting containers vertically through the stack 3 along the helical path formed by the conveyor belt 2. In the disclosed embodiment the inlet 19 is arranged above the outlet 20.

In the upper portion the apparatus 15 comprises a first end closure 16, which in one piece covers both the annular 10 and the central space 11. The first end closure 16 could be constituted of two pieces, a first piece, which is arranged to cover the annular space 10, and a second piece, which is arranged to cover the central space 11. The first end closure 16 should preferably be easy removable so as to allow access for maintenance and cleaning. Nozzles 22 are arranged below the first end closure 16 above the annular space 10 for spraying water onto the conveyor belt 2 and products being transported thereon. Although not disclosed, it is to be understood that additional nozzles can be arranged at a number of water supply zones along the path of the conveyor belt, providing water with the same or different tem- perature.

The first end closure 16 comprises an outlet 23 for a flow of air comprising evaporated water, which outlet will be further discussed below. The

flow of air is generated by circulation means 31 in the form of fans being arranged in the upper part of the apparatus.

The apparatus 15 further comprises a second end closure 18, which is arranged against the lowermost turn 4 formed in the stack 3. The second end closure 18 forms a bottom wall, which abuts against the outer cylindrical wall 8. The second end closure 18 is preferably slightly conical, providing a collecting means 24 for water. In the bottom thereof an outlet 25 is formed. Said outlet 25 can via a return channel 26 communicate with the nozzles 22 for recycling the collected water. The return channel 26 can comprise means for purifying 27 the water sprayed onto the products and/or means for tempering 28 the water. The return channel 26 can also comprise means 35 for adding fresh water to compensate for bleed off.

A condenser 29 can be arranged between the outlet 23 and the nozz- les 22 for condensing evaporated water disposed via said outlet. Such condensed water is returned via a return channel 36 to the apparatus in its collecting means 24. Air from the condensor can be returned via a return channel 37 to the apparatus in its collecting means 24.

Air could be supplied directly to the lower portions of the apparatus 15 via a means 38 or via the condensor.

It is to be understood that the nozzles 22 can be provided with fresh water only, or a mixture of fresh and re-cycled water. In order of compensating for losses of water due to evaporation, bleed off or during purification, an amount of fresh water is to be added to the re-circulated water. The system can in addition comprise by way of example a heat treatment apparatus 30 supplying heat-treated products to the inlet 19 of the apparatus 15. The heat treatment apparatus 30 can by way of example be a pasteurizer 32 supplying newly pasteurized hot containers directly to the inlet of the apparatus. It is to be understood that also other types of heat treatment apparatuses but pasteurizers may be used.

In the following, the function of the system, the apparatus and thus the method will be disclosed.

In the disclosed apparatus 15, the conveyor belt 2 has a conveying direction V from the inlet 19 towards the outlet 20, the inlet being arranged above the outlet. By the endless conveyor belt 2 forming a stack 3, the products P entering the inlet 19 will be transported through the stack 3 along an endless path in the vertical direction. This means that the required floor space

is limited. Further, the dwell time of the products P inside the stack is decided by the length of the conveyor, the height of the stack, i.e. the number of turns, and the speed of the conveyor belt.

While the products P are transported along the path a flow of water W is sprayed onto the products by the nozzles 22. The nozzles 22 are arranged on the top of the stack 3, and preferably in the annular space 10, whereby the sprayed water W is descending by gravity onto the products P. Also, from the opposite direction, a flow of air A is blown onto the products P. However, it is to be understood that the air can be blown in any other direction. Depending on the position of the circulation means, the air can be sucked through the apparatus with the same result. The air can be blown or sucked in the annular space 10 only or in both the annular 10 and the central space 11. The airflow can be in the interval 0.05-5.0 m/s.

When meeting the hot products P the water W is evaporated, extract- ing energy from the products. The evaporated water EW is blown away from the products P towards the outlet 23 arranged in the first end closure 16 at the top of the stack 3. The flow of water W, evaporated water EW and air A in the vertical direction through the stack is permitted by the conveyor belt 2 being provided with a bottom part 6 having some sort of perforations. Also, a flow vertically as well as horizontally (or a mixture thereof) is permitted by the design of the links 5 of the conveyor belt 2. Thus, there is a flow of sprayed water W generally in the vertical direction from the inlet 19 towards the outlet 20 through the annular space 10, whereas there is a flow of air A and evaporated water EW not only in the opposite vertical direction, which flow can be in the annular space 10 as well as in the central space 11 , but also in the generally horizontal direction between the annular space and the central space. The evaporated water EW and the air A exit the apparatus 15 mainly via the outlet 23 arranged in the first end closure 16. The evaporated water EW can either be disposed into the ambient air or be directed via a condenser 29 for condensing and extracting the water W and returning the same to the apparatus via the return channel 36.

Any water W descending through the stack 3 towards the bottom thereof is collected in the second end closure 18. The collected water can be returned via the outlet 25 thereof, via the return channel 26 and back to the nozzles 22. During this re-cycling the water may pass means for purifying 27 the water and/or means for tempering 28. To compensate for bleed off or evaporation, a certain amount of fresh water can be added by means 35.

During the flow of sprayed water W and evaporated water EW being blown away from the products P, energy is consumed, resulting in the temperature of the products and their contents in the case the products being containers being lowered. The energy consumption is shown by the outlet temperature of the products being reduced to be lower than the inlet temperature thereof and the outlet temperature of the water being reduced to be the same or lower than the inlet temperature thereof.

Depending on the required dryness of the products, the amount of water sprayed, i.e. the flow value can be varied. By way of example, the amount of water sprayed onto the products can be balanced so that the water sprayed meeting the hot products in the form of a mist is immediately evaporated and removed by the airflow. Alternatively an overfeeding of water can be used, wherein the amount of water sprayed onto the products can be from a few times to up to 200 times the evaporated amount in order of obtaining optimal cooling performance for different conditions, applications etc. The excessive water not evaporated can be collected in the collecting means 24 for re-circulation. It is to be understood that for some applications the amount of water sprayed on the products should be in the range of or less than the amount of water that can be evaporated. The objective would be to exclude the recirculation of water and make a more simple and less expensive system. Further, when the products, such as naked products or paper based containers, are sensitive to water, or when the products must be dry at the outlet of the apparatus, the amount of water sprayed over the products can be controlled by a sensor measuring the relative humidity. The apparatus has been described above based on a belt conveyor with a self-stacking conveyor belt. It will be appreciated that the invention can be applied with the same result to a belt conveyor comprising a non-self- stacking conveyor belt, or with a conveyor belt with any other design. It will be appreciated that the present invention is not limited to the shown and described embodiment of the inventive apparatus, system and method. The apparatus has been disclosed as having a circulation means arranged in the top, whereby the air is sucked through the apparatus. Alternatively, the circulation means can be positioned in the bottom of the apparatus, whereby the air is pressed through the apparatus. The air supplied to the apparatus would normally be ambient air or ambient air mixed with re-circulated air. The air is usually passed through some sort of filter to remove particles. It should be understood that the air

could be cooled and dehumidified in an air-cooling coil. The water evaporated from the surface of the products would condense in the cooling coil and therefore enhance the heat transfer and performance not only between the products and the air, but also between the air and the air cooler. Several modifications and variants are thus conceivable, and consequently the invention is defined exclusively by the appended claims.