Abstract:
A tubular heat treatment apparatus comprising a number of tubes arranged in a number of groups. Each of the number of groups are arranged to process product within a pre-determined temperature interval. At least one of the groups is swept by a sheet such that heat transfer to or from the group is reduced.

Description:
TECHNICAL FIELD 
       [0001]    The invention generally relates to the field of heat transfer, more particularly to tubular heat treatment apparatus, such as a tubular heat exchanger or tubular holding cell, with improved energy efficiency. 
       BACKGROUND OF THE INVENTION 
       [0002]    Today, it is a common approach within the food processing industry as well as other industries to use tubular heat exchangers for heat treatment purposes. 
         [0003]    Within the food processing industry it is common to have the tubular heat exchanger manufactured in stainless steel. A steel grade of insert tubes and shell tubes, placed outside the insert tubes, can be chosen depending on the product to be processed. 
         [0004]    In short, by example, product enters the tubular heat exchanger in the insert tubes at low temperature and is heated by a media flowing in the shell tubes outside the insert tubes. When the product reaches pasteurization temperature it enters a cell either included in the heat exchanger or separate, a tube with a length adjusted to keep the product at pasteurization temperature for a certain time calculated for each product case. After the holding cell, the product starts cooling down; media now flows outside the insert tubes in the shell tubes. Preferably, insert tubes, shell tubes and holding cells are arranged so they can treat different products and cases. 
         [0005]    In order to reduce heat transfer, insert tubes and shell tubes used for heating the product can be grouped together, and in the same way insert tubes and shell tubes used for cooling the product can be grouped together. By doing so the heat transfer between different parts within the tubular heat exchanger can be reduced, and hence the energy efficiency can be increased. 
         [0006]    Another approach to reduce the energy transfer within the tubular heat exchanger is to insulate the shell tubes by using for example mineral wool or cellular rubber. Since a vast amount of energy is used for heat treatment in e.g. a food processing plant there is a need to reduce this in order to be able to provide heat treatment in a more environmental friendly way. 
       SUMMARY 
       [0007]    Accordingly, the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above mentioned problems. 
         [0008]    According to a first aspect it is provided a tubular heat treatment apparatus comprising a number of tubes, wherein said number of tubes is arranged in a number of groups, wherein each of said number of groups are arranged to process product within a pre-determined temperature interval, wherein at least one of said number of groups are swept by a sheet, such that heat transfer to or from said at least one of said groups is reduced. 
         [0009]    A tubular heat treatment apparatus should be understood to include, but not limited to, a tubular heat treatment apparatus and a tubular holding cell. 
         [0010]    The sheet may be coated at least one side with a silicone material. 
         [0011]    The sheet may be made of glass fibre. 
         [0012]    A first end section and a second end section of said sheet may be fastened together. 
         [0013]    The first end section and said second end section can be placed downwards. 
         [0014]    The first end section or said second end section may be in contact with another sheet swept around another group of said number of groups. 
         [0015]    The other group may in use be placed below said group. 
         [0016]    The tubular heat treatment apparatus may further comprise at least one element placed between said group of tubes and said sheet. 
         [0017]    The at least one element may in use be placed on top of said group. 
         [0018]    The at least one element may be placed in a corner section of said group. 
         [0019]    At least two of said number of groups, comprising said at least one of said number of groups, can be swept at least partly by an additional sheet. 
         [0020]    The tubular heat treatment apparatus may further comprise a mat filled with insulating material, such as mineral wool, provided between one of a number of covers of said tubular heat treatment apparatus and said tubes. 
         [0021]    A first group of said number of groups is arranged to process said product in a first temperature and a second group of said number of groups is arranged to process said product in a second temperature, said first temperature being lower than said second temperature, wherein said first group is in use placed below said second group. This means that it is to be understood that each number of groups may be arranged to individually process product within a pre-determined temperature interval. The pre-determined temperature interval may thus be the same or different for each number of groups. 
         [0022]    The tubular heat treatment apparatus can be for food processing. 
         [0023]    According to a second aspect it is provided a system comprising a tubular heat according to the first aspect. 
         [0024]    According to a third aspect it is provided a sheet arranged for being swept at least partly around said at least one of said number of groups of said tubular heat treatment apparatus according to the first aspect. 
         [0025]    The sheet may be coated at least one side with a silicone material. 
         [0026]    The sheet may be made of glass fibre. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, wherein: 
           [0028]      FIGS. 1   a  and  1   b  generally illustrates an example of a tubular heat exchanger. 
           [0029]      FIG. 2  illustrates an example of a cross sectional view of a tubular heat exchanger. 
           [0030]      FIG. 3  illustrates an example of a cross sectional view of another tubular heat exchanger. 
           [0031]      FIG. 4  illustrates an example of a cross sectional view of a tubular heat exchanger with groups swept by sheets. 
           [0032]      FIG. 5  illustrates another example of a cross sectional view of a tubular heat exchanger with groups swept by sheets. 
           [0033]      FIG. 6  illustrates still an example of a cross sectional view of a tubular heat exchanger with groups swept by sheets. 
           [0034]      FIG. 7  illustrates an example of a sheet with end section fastened together. 
           [0035]      FIG. 8  illustrates an example of a group of tubes swept by a sheet with end sections fastened together and placed downwards. 
           [0036]      FIG. 9   a  illustrates a group of tubes swept by a sheet. 
           [0037]      FIG. 9   b  illustrates a group of tubes swept by a sheet with elements placed in corner sections in order to increase the amount of air held inside the sheet. 
           [0038]      FIG. 9   c  illustrates two groups of tubes as illustrated in  FIG. 9   b  with an additional sheet swept around these two groups and with elements in the corner sections for increasing the amount of air held inside the additional sheet. 
           [0039]      FIG. 10  illustrates an example of a cross sectional view of a tubular heat exchanger with groups of tubes swept by sheets and with an element placed on top of an upper group in order to provide slanted surfaces on an additional sheet swept around a number of groups. 
           [0040]      FIG. 11  illustrates an example of a cross sectional view of a tubular heat exchanger with groups of tubes swept by sheets and with a mat filled with insulated material placed outside the tubes. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]      FIGS. 1   a  and  1   b  illustrates an example of a tubular heat exchanger  100 , more particularly a Tetra Spiraflo™ marketed by Tetra Pak. As illustrated, a number of tubes are connected to each other via bend pipes  102  providing for a compact design. In the illustrated example, insert tubes  104  are kept in sets and each set is arranged in a bigger pipe referred to as a shell tube  106 . The food product is fed through the insert tubes and a heat transfer medium is fed through the shell. In order to keep energy consumption low, it is advantageous to use outgoing product or media, which is to be cooled down, as the heat transfer medium. Such system are often referred to as regenerative systems. 
         [0042]    On the sides and on the top of the tubular heat exchanger  100  side covers  101   a  and top covers  101   b  can be placed. During service these can be be removed in order to provide for easy access. 
         [0043]      FIGS. 2 and 3  illustrate by example cross sectional views of a tubular heat exchanger  200  and a tubular heat exchanger  300 , respectively. 
         [0044]    As illustrated, each tubular heat exchanger can be designed with different tube and shell dimensions, different configuration and different sizes in order to meet the needs specified e.g. by a food processing company. In order to provide for efficient production the tubular heat exchangers can be built up in modules. As example, the tubular heat exchanger  200  illustrated in  FIG. 2  is built up by four modules placed in one column, referred to as a 4×1 tubular heat exchanger. The tubular heat exchanger  300  illustrated in  FIG. 3  has modules placed in four columns with four modules in each of the columns, referred to as a 4×4 tubular heat exchanger. 
         [0045]      FIG. 4  illustrates by example a tubular heat exchanger  400  having a number of shell tubes, insert tubes (not illustrated), and tubes used as holding cells, herein the shell tubes and the tubes used as holding cells are together referred to as tubes. 
         [0046]    In order to reduce heat transfer from tubes used for heating or holding heated product to tubes used for cooling product, one or several sheets may be used. 
         [0047]    As illustrated, a first group of tubes may be swept by a first sheet  402 , a second group may be swept by a second sheet  404 , a third group may be swept by a third sheet  406 , a fourth group may be swept by a fourth sheet  408 , a fifth group may be swept by a fifth sheet  410 , a sixth group may be swept by a sixth sheet  412  and a seventh group may be swept by a seventh sheet  414 . 
         [0048]    Due to that hot air is lighter than cold air and thereby move upwards, it is advantageous to have groups of tubes for heating or holding heated product placed above groups of tubes used for cooling or holding cooled product. In this way, heat released from the groups used for heating or holding heated product will not as easily be transferred to the groups used for cooling or holding cooled product. 
         [0049]      FIG. 5  illustrates by example a tubular heat exchanger  500  provided with seven groups swept by seven different sheets in a similar way as the tubular heat exchanger  400  illustrated in  FIG. 4 . More particularly, a first group of tubes may be swept by a first sheet  502 , a second group may be swept by a second sheet  504 , a third group may be swept by a third sheet  506 , a fourth group may be swept by a fourth sheet  508 , a fifth group may be swept by a fifth sheet  510 , a sixth group may be swept by a sixth sheet  512  and a seventh group may be swept by a seventh sheet  514 . 
         [0050]    In this example, in order to further prevent heat transfer between groups of tubes with different temperatures, two additional sheets, an eighth sheet  516  and a ninth sheet  518 , can be used. 
         [0051]    In the illustrated example, the eighth sheet  516  is swept around the first group swept by the first sheet  502 , the second group swept by the second sheet  504  and the third group swept by the third sheet  506 . The ninth sheet  518  is swept around the fifth group swept by the fifth sheet  510 , the sixth group swept by the sixth sheet  512  and the seventh group swept by the seventh sheet  514 . 
         [0052]      FIG. 6  illustrates a tubular heat exchanger  600  similar to the heat exchangers  400 ,  500  illustrated in  FIG. 4  and  FIG. 5 , but with another set up of the groups of tubes. More particularly, the first group is divided in two different groups  602   a ,  602   b . How to group the tubes in order to get an energy efficient tubular heat exchanger may be determined e.g. by using simulation tools. 
         [0053]    By reducing the heat transfer between different groups within the tubular heat exchangers, as well as the heat transfer between the different groups and the surroundings, a number of advantages can be achieved, for instance: 
         [0054]    Energy Saving 
         [0055]    Due to that the sheets reduce heat transfer between the tubes used for heating and holding the product heated and the tubes used for cooling less energy for heating as well as for cooling is needed. Further, apart from reducing transfer of heat between different groups, the heat recovery within the tubes for heating and holding the product heated will be improved. Put in other words, excessive heat released from one tube among the tubes may be used for heating another tube among the tubes with a slightly lower temperature. In this way less heating media is needed. In the same way the cooling recovery within the tubes for cooling will be improved. In this way less cooling media is needed. 
         [0056]    Reduce Temperature Drop in Holding Cells 
         [0057]    By using sheets as described above, the temperature drop in holding cells can be decreased. An effect of this is that a product temperature when entering the holding cell can be lowered. Since high product temperatures affect the product quality this can lead to improved product quality. 
         [0058]    Reduce Cover Temperature 
         [0059]    Since using sheets as described above will result in less heat transfer to the surroundings this will result in a cooler working environment, thereby reducing costs for cooling the plant. A further effect is that covers of the tubular heat exchanger will be cooler which leads to a safer working environment. More particularly, the risk that operating personnel coming in contact with hot surfaces can be reduced. 
         [0060]    Advantages of using sheets as illustrated by example in  FIG. 4 ,  FIG. 5  and  FIG. 6  are for instance: 
         [0061]    Cost Efficiency 
         [0062]    Using sheets for sweeping groups of tubes is in many cases more cost efficient compared to prior used techniques, e.g. insulating the tubes individually. One reason for this is that less material is needed for the sheets compared to e.g. a mineral wool filled mat. 
         [0063]    Low Assembly Cost 
         [0064]    Since the sheets are lighter than mineral wool it is easier for production personnel to lift these. Today, when using mineral wool mats an overhead crane is in many cases used during assembly. Since the sheets is substantially lighter, about ten times, there is not the same need for the overhead crane. 
         [0065]    Long Life Time 
         [0066]    The sheets can be made of strong material providing for that they will not be needed to be replaced frequently, which is an advantage when determining total cost of ownership. 
         [0067]    Low Environmental Impact 
         [0068]    Since a lighter material and less material is needed the environmental impact of the tubular heat exchanger as a whole will be reduced. 
         [0069]    Low Stock Keeping Cost 
         [0070]    The sheets can easily be cut in pieces. Therefore it is possible to keep the sheet material on a roll and cut piece by piece during production. In this way the number of items can be reduced, which provides for more efficient stock keeping. 
         [0071]    Hygienic 
         [0072]    The sheets can be made of a material not absorbing liquid, thereby providing for that no product will find its way into the sheet. Further, by choosing such a material the sheets can easily be cleaned and made to withstand any cleaning products used. 
         [0073]    As further described below, a distance element may be placed on a top section of a group of tubes swept by a sheet thereby forming a roof top like upper part of the sheet with inclined surfaces providing for that liquid does not stay on top of the sheet. 
         [0074]    Corrosion 
         [0075]    The sheets can be made of a material not inducing corrosion, neither the material itself, nor by causing liquid to stay in contact with the shells for longer times. 
         [0076]    Temperature 
         [0077]    The sheets can be made of a material withstanding temperatures of 160° C. or above. For instance, by choosing a silicone coated sheet it can withstand temperatures up to 250° C. According to the present invention the silicone coated sheet is thus for example a silicone suitable to be used within the necessary temperature interval. An example thereof is a silicone rubber coating such as a flame retardant an chemical resistant silicone rubber coating. 
         [0078]    Inspectability 
         [0079]    If the sheets are not fastened in the tubes, the sheets can be pushed to either side and thereby making the tubes possible to access for an operator or service engineer. 
         [0080]    An example of a sheet material is Temtex™ 420/SG2 provided by TEMATI. The thickness can be chosen to be 0.45 mm. The material can be waterproof, chloride free material that can withstand 160° C. such as a glass fibre thin fabric coated with thin layers of silicone on each side. 
         [0081]      FIG. 7  illustrates an example of a piece  700  of sheet material with two end sections fastened together. The two end sections may be stapled together or fastened by any other method, such as welding, sewing, gluing or taping. An advantage of stapling the two end sections together is that when having the sheet swept around a group of tubes, any liquid will sipper out between the two end sections, provided that the splice is placed downwards. 
         [0082]      FIG. 8  illustrates by example a cross sectional view of a group of tubes swept by a sheet that is stapled together. As described above, by arranging end sections downwards liquid can pass through the splice and be seen by an operator or service engineer on the next sweep or on the floor. 
         [0083]    Further, an advantage of having end sections being in contact with other another sheet is that air flow between the groups of tubes can be reduced. 
         [0084]      FIG. 9   a  illustrates a group of four tubes swept by a sheet. 
         [0085]    As illustrated in  FIG. 9   b , in order to get more insulating air in a space formed by the sheet, such that radiance from tubes to the surroundings can be lowered, distance elements  900   a ,  900   b ,  900   c ,  900   d  can be provided on the tubes. 
         [0086]    A further effect of the distance elements  900   a ,  900   b ,  900   c ,  900   d  is that less space is provided between the group of tubes and covers, not illustrated, providing for that less air flow between the sheets and the covers. 
         [0087]    If having an additional sheet swept around the group secondary distance elements  902   a ,  902   b ,  902   c ,  902   d  may be used for providing more insulating air between the group of tubes and the surroundings and for providing less air flow between the sheets and the covers. 
         [0088]      FIG. 10  illustrates a tubular heat exchanger  1000  similar to the tubular heat exchangers illustrated in  FIG. 4 ,  FIG. 5  and  FIG. 6 . However, unlike the tubular heat exchangers illustrated in  FIG. 4 ,  FIG. 5  and  FIG. 6 , the tubular heat exchanger  1000  is provided with a element  1002  placed on top of an uppermost sheet swept around a first group of tubes. An effect of the element  1002  is that an outer sheet  1004  swept around the first group of tubes as well as the element  1002  will have inclined top surfaces providing for that liquid will have less easy to stay on these surfaces, which is an advantage since liquid gathered on these surfaces impact the efficiency of the tubular heat exchanger. 
         [0089]      FIG. 11  illustrates a tubular heat exchanger  1100  similar to the tubular heat exchangers illustrated in  FIG. 4 ,  FIG. 5 ,  FIG. 6  and  FIG. 9 . However, unlike these tubular heat exchangers, this is provided with an insulated mat  1102  outside the swept groups of tubes. 
         [0090]    The insulated mat  1002  may be made of mineral wool covered with silicone sheets. An advantage of having the insulated mat  1002  is that it can reduce air flow outside the groups of tubes and the covers and thereby contribute to lower the cover temperature. 
         [0091]    As illustrated, the insulated mat can be placed such that a top and sides of the tubes are covered, and leaving a bottom open. An advantage of this is that liquid will have free way to the floor making it easier for service personnel or operators to detect it. 
         [0092]    The different features illustrated in  FIG. 4 ,  FIG. 5 ,  FIG. 6 ,  FIG. 8 ,  FIG. 9  and  FIG. 10  can be combined in different ways depending on the specific conditions for specific situation. 
         [0093]    Generally, in a heat exchanger a heating media can be used for heating a product and a cooling media can be used for cooling the product. In a holding cell however the purpose is to hold the product for a certain period of time at a certain temperature, and therefore heating media and cooling media is generally not needed. Therefore, even though tubular heat exchangers have been used as examples above, the same principles may apply to tubular holding cells. 
         [0094]    The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.