EP2850377B1

EP2850377B1 - Rotary heat exchanger

Info

Publication number: EP2850377B1
Application number: EP13735396.7A
Authority: EP
Inventors: Alberto Pozzi; Flavio Convento
Original assignee: Pozzi Leopoldo SRL
Current assignee: Pozzi Leopoldo SRL
Priority date: 2012-05-18
Filing date: 2013-05-16
Publication date: 2016-09-14
Anticipated expiration: 2033-05-16
Also published as: ES2617525T3; EP2850377A1; WO2013171566A1; ITMI20120866A1; DK2850377T3

Description

FIELD OF THE INVENTION

The present invention relates to a heat exchanger of the rotary type, wherein inside a container for a first liquid a rotor is rotated comprising a plurality of hollow bodies, the latter generally having the shape of hollow discs, fluidically linked to each other to allow the passage of a second liquid involved in the heat exchange.

KNOWN PREVIOUS ART

The heat exchangers of the rotary type are currently used for recovering the heat present in liquids and in particular in waste waters deriving from a number of industrial and not industrial manufacturing processes, such as for example manufacturing processes in the textile field and in washing and treating fields of fabrics. The waters deriving from such manufacturing processes may contain, usually entrained, solid type residuals deriving from the previous manufacturing processes carried out by means of the liquid. Take for example the water used for the textile manufacturing processes such as dyeing, or fiber treatment or industrial washing of large amounts of garments and fabrics.
It has to be noted that, in addition to the previously specifically mentioned fields, this type of heat exchangers can be used for recovering heat from liquids, waste waters, sludges of any origin and has particular application in the cases wherein such liquids contain residuals of the manufacturing processes previously carried out with such a liquid.
In fact, in rotary exchangers rotating movement of the rotor inside the exchangers allows the effective heat exchange, in addition to the generation of a turbulent motion of the liquid located inside the container such to allow the removal or at least the separation of solid residuals therein contained.
Patent US4.301.860 describes a heat exchanger of the above mentioned type provided with a container inside which the first liquid is filled, preferably waste water from industrial processing and treatment, by proper input and output means.
Inside the container a rotor is rotatably mounted provided with a plurality of hollow bodies, having the shape of hollow discs of lenticular shape, which allow the passage in their inside of the second liquid involved in the heat exchange. The two liquids are separated from each other and are not directly contacting, but the heat is exchanged therebetween through the surfaces of the hollow discs rotated in the exchanger. In fact, as mentioned, the discs are submerged in the liquid contained in the exchanger container, whereas the other liquid passes inside the discs which are fluidically linked to each other.
In particular, the discs used as heat exchange surfaces have substantially a lenticular shape, in other words they are formed of two convex side walls having a circular perimeter which are constrained in a facing position such to constitute a hollow disc with the side walls protruding outwards which form in their inside the hollow of the lenticular disc designed for the passage of the second liquid.
Each hollow disc of the exchanger described in US4.301.860 comprises a central inner diaphragm and dips made on the surface of the side walls acting to adjust the liquid passage.
The formation within the disc of a pathway for the liquid passing within the same by means of the dips, allows to increase the efficiency of the heat exchange between the two liquids through the walls of the discs of lenticular shape arranged in succession on the rotor. The dips, which have substantially circular shape and are arranged at different distance from the disc rotation axis, allow as well to strengthen the surface thereof.
In fact, when the two walls are coupled, the dips are correspondingly arranged and their lower surfaces are contacted, with the diaphragm interposition, to- facilitate the constraint between the two side walls. Furthermore, at the contacted dips, when the two side walls are constrained to each other to form the disc of lenticular shape, constraining means such as for example welding points or nails and like constraining means are prearranged.
The heat exchanger according to the document DE19615606 comprises a rotor provided with a plurality of hollow bodies, in the shape of hollow discs of lenticular shape.
Each hollow disc of the exchanger comprises some dips, having arched shape, made on the surface of the side walls of each hollow body.
Furthermore, inside each hollow body a central inner diaphragm is present and provided with fins on its surface, the fins having arched shape too. Some drawbacks of the heat exchangers of the above described type have been detected over time, emphasized in particular use fields and by increasingly higher demands in terms of the exchanger efficiency and widening of operative field.
In fact, in some use fields the liquid located in the exchanger is cyclically and impulsively subjected to pressure variations. In addition, in some cases the liquid is subjected to pressurization and depressurization cycles. In such occasions, especially in the constraining regions of the two walls composing the hollow body, breakings due to the excessive elasticity of the latter have been found.
Therefore there is the need of increasing the strength of hollow bodies of the exchanger also in case of wishing to increase the pressure of the liquids involved in the heat exchange.
The heat exchanger according to DE19615606 is provided with an inner diaphragm which aids to strengthen the hollow cylindrical bodies; however it has to be noted that the presence of such diaphragms, and in particular of the arched fins arranged on the diaphragm surface, causes the formation of high load losses which adversely affect the exchanger efficiency.
In fact, inside each hollow body the presence of fins, in addition to protrusions corresponding to the dips made on the surfaces of the side walls of the hollow body, causes the formation of narrowed passages within the hollow body which generate high load losses.
Other drawbacks of the exchangers known in the art are caused by the load losses of the liquid inside which the rotor, on which the hollow bodies are constrained, is submerged. In fact, in order to obtain a sufficient heat length of the exchanger, fixed baffles, or partitions, are used, which are installed within the exchanger container between hollow bodies located in succession on the rotor. The baffles interspaced by the hollow bodies, form chambers fluidically linked to each other such to create a labyrinth pathway to extend the heat exchange surface, by increasing the efficacy of the exchange process. However, in very long exchangers, with a high number of hollow bodies installed in succession, the presence of a high number of baffles yields to the formation of excessive load losses with consequent challenges in the handling of the liquid located inside the exchanger container, to such an extent that some baffles had to be eliminated in many applications.
The document DE19615606 teaches how to increase the rotation speed of the rotor on which the hollow bodies of lenticular shape are constrained. However the presence of many hollow bodies and many baffles, inside the exchanger container, causes the formation of a "hydraulic plug", due to high load losses, which adversely affects the handling of the liquid located inside the exchanger container.
Object of the present invention is to provide a heat exchanger which overcomes the above shortly reviewed drawbacks and which allows as well to obtain high heat exchange efficacy.
Further object of the present invention is to provide a heat exchanger of the rotary type wherein the rotated hollow bodies are provided with such a stiffness to avoid possible breakings, especially in presence of high pressure liquids and in case of cyclical application of pressurization and depressurization of the liquid/s located in the exchanger.
Furthermore, it is object of the present invention to provide a heat exchanger wherein the load losses of the liquid located inside the exchanger container are limited and at the same time allows to improve the liquid circulation within the same, especially in the cases in which the liquid density is high.

SUMMARY OF THE INVENTION

These and other objects are obtained by a heat exchanger for liquids, according to the present invention, comprising a container inside which at least a first liquid is located and at least one rotor rotatably constrained inside the container. The rotor comprises at least one hollow body provided with at least two side walls constrained to each other to form a hollow space within them for the passage of at least a second liquid. The hollow body/ bodies is/ are rotated around an axis and at least one of the side walls comprises at least one elongated dip extending along a line non - radial with respect to the rotation axis.
It has to be immediately noted that with the term "dip" a portion of the surface of the side walls of the hollow bodies is meant which is located at a lower level with respect to the surface outside the dip. In other words, the dip is a recessed portion of the side wall wherein the points within the same are at a lower height with respect to the outer surface of the side wall outside the dip. Each dip forms, of course, a protrusion next to the same within the hollow body.
Furthermore, the expression "extending along a non - radial line" herein and in the following is used to mean that the line along which the elongated dip extends is not arranged according to a radius and therefore it is not lying on a radius of the side wall defined from the rotation axis of the hollow body. In other words, the line along which the dips extend at least partially touches the radius of the side wall starting from the rotation center of the hollow body. As mentioned, according to an aspect of the present invention, the dips made on the side walls of the hollow body are elongated such that at least two points of the side surface not belonging to the same radius with respect to the rotation axis of the hollow body can be joined.
Advantageously the presence of the elongated dips allows to significantly improve the stiffness of the hollow body and its side walls, in fact, the dips within the hollow body form a plurality of inner walls which reduce the elastic properties of the hollow body.
This way, the breakings observed in the use of the currently used exchangers, especially as a consequence of pressurization and depressurization cycles of the liquids located in the exchanger, can be remarkably reduced. Furthermore, due to the stiffness increase of hollow bodies of the exchanger, the working pressure of the liquids involved in the heat exchange can be increased.
According to the invention, at least one side wall of the hollow body comprises a first plurality of dips and at least one second plurality of dips having smaller dimensions than the dips of the first plurality of dips. Advantageously, the dips with smaller dimensions than the other dips allow to cover, that is to say to occupy, an area greater than the surface of the side walls of the hollow body so to further increase the stiffness thereof.
Furthermore, the presence of a first plurality of dips and at least one second plurality of dips allows to increase the exchanger efficacy without causing the formation of undesired load losses, so as it occurs in the exchangers known in the art, for example in the exchanger according to the document DE19615606 , due to the presence of a plurality of fins within each hollow body.
Furthermore, according to an aspect of the present invention, the at least one second plurality of dips substantially extends on a circular crown having smaller extension with respect to the circular crown on which the first plurality of dips extends. In detail, the circular crown on which the at least one second plurality of dips extends is arranged at a radial distance from the rotation axis of the hollow body larger than the circular crown on which the first plurality of dips extends.
According to an aspect of the present invention, the heat exchanger is provided with at least one dip on each of the side walls of the hollow body, and in particular the dips made on a side wall are overlapped in at least one contacting point with at least one dip arranged on another side wall of the hollow body. In other words, the dips on the two different side walls of the hollow body are arranged such to become overlapped in at least one contacting point, or area.
According to a preferential aspect of the present invention, the heat exchanger is provided with at least one dip of said first plurality of dips and with said at least one second plurality of dips, on each of the side walls of the hollow body. As mentioned, the dips made on a side wall are overlapped in at least one contacting point with at least one dip arranged on another side wall of the body.
It has to be noted that the contact between the dips arranged on different walls, which preferably occurs at the lower surface of the overlapped dips, can either be direct and indirect, for example by the interposition of an inner wall or diaphragm inside the hollow body.
The advantages related to the stiffening of the hollow bodies of the exchanger are particularly evident in case the dips located on two side walls of the hollow body have one or more contacting points or areas. In fact, the contact between these parts of the dips, and in particular their lower surface, allows to stiffen the structure of the hollow body.
This way, when the exchanger liquid or liquids is/ are subjected to pressurizations or depressurizations, cyclically and/ or impulsively too, the disc is not subjected to "inflation" and "deflation" effects by virtue of its radial and annular stiffness. According to an aspect of the present invention, at least one dip of a side wall is overlapped with at least two different dips arranged on the other side wall of the hollow body. The overlapping of one dip with at least two different dips arranged on the other side wall of the hollow body, causes the formation of two different contacting points or areas.
It has to be noted that, according to a preferred aspect of the present invention, at least one dip of the first plurality of dips of a side wall is overlapped with at least two different dips of the first plurality of dips arranged on the other side wall of the hollow body.
Furthermore, according to a preferred aspect of the present invention, at least one dip of the at least one second plurality of dips, arranged on a first side wall of the hollow body, is overlapped and has at least one contacting point, with at least one dip of the first plurality of dips arranged on another side wall of the hollow body.
In this way, the side surfaces of the hollow bodies become advantageously stiffened while allowing an effective heat exchange without generating undesired load losses.
In fact, such a particular arrangement allows to obtain a larger number of contacting points between the dips and thus allows to provide a larger number of stiffening areas of the hollow body, at which the constraint of the two side walls can be made, for example by welding, riveting and like constraining means.
According to an aspect of the present invention, at least one dip of the at least one second plurality of dips, arranged on a first side wall of the hollow body, is overlapped and has at least one contacting point, with at least one dip of the first plurality of dips and with at least one dip of the second plurality of dips arranged on another side wall of the hollow body.
Furthermore, according to a preferred embodiment, each dip arranged on a wall is overlapped with three different dips arranged on the other side wall of the hollow body, forming three different contacting points.
In detail as already mentioned, a dip belonging to the first plurality of dips, arranged on a side wall, is overlapped with two dips belonging to the first plurality arranged on another side wall of the hollow body, as well as with a dip belonging to the second plurality of dips arranged on another side wall of the hollow body. Preferably, the contacting point or points of the overlapped dips belonging to different side walls is/ are arranged substantially at the ends of the line along which the dip extends. A third contacting point is preferably arranged in substantially central (median) position of the line along which the dip extends.
Preferably, the least one contacting point of the overlapped dips of the first plurality of dips, belonging to different side walls, is substantially arranged at an end of said line along which said at least one dip extends.
In addition, it has to be noticed that the at least one contacting point of at least one dip of the at least one second plurality, arranged on a first side wall of the hollow body, with at least one dip of the first plurality of dips arranged on another side wall of the hollow body, is arranged in a substantially central position of the line along which the at least one dip of the first plurality of dips extends.
Advantageously, the overlapping of a dip belonging to the second plurality in a median point of a dip belonging to the first plurality allows to increase the stiffness of the surface of the hollow body of the exchanger.
Meanwhile, the overlapping of the dips belonging to two opposite side walls of the hollow body allows to form passages within the same which allow an effective heat exchange without the formation of undesired load losses, as conversely happens for example in the exchanger according to the document DE19615606 due to the protruding fins arranged on the central diaphragm.
Advantageously, the contacting points or areas of the overlapped dips can be used for adding constraining means of the side walls for further stiffening and strengthening the hollow body. In detail, constraining means of known type such as for example nails, rivets, welding points and the like can be installed at the contacting points of the overlapped dips.
According to an aspect of the present invention, the line along which the elongated dip or dips extend/s can be at least partially curved and/ or at least partially straight. Furthermore, the exchanger according to the present invention is characterized in that the dips in a first side wall are arranged according to a first slope with respect to a radius of the hollow body and the dips arranged on another side wall of said hollow body extend with an slope, with respect to a radius, opposite to the dips arranged on the other side wall of the hollow body. Such a particular structure allows to improve the feeding of the liquid within the exchanger container thus remarkably reducing the generated load losses.
Advantageously, the heat exchanger according to the present invention, provided with a plurality of hollow bodies of the above described type and in particular provided with a series of arched dips arranged such to become oppositely sloped on two opposite side walls of the hollow body, allows to treat much more viscous liquids also having high density without generating excessive load losses.
Such advantages are most apparent in the preferred embodiment in which a first plurality and at least one second plurality of dips arranged on the side walls of the hollow body are present, which are arched and arranged with substantially opposed slope on the two facing and constrained side walls forming the hollow body.

BRIEF DESCRIPTION OF THE FIGURES

These and other advantages will be evident from the following description and the figures in attachment, herein reported for illustrative and not limitative purposes, wherein:

Figure 1 is a plan view of a side wall of the hollow body of the heat exchanger according to the present invention;
Figure 2 is an enlarged view of a portion of the side wall of figure 1;
Figure 3 is a cross sectional view of the side wall according to the plane A-A of figure 1;
Figure 4 is a view of a portion of the hollow body formed by two side walls constrained to each other in facing position in which the dips present on the upper wall (solid lines) and the dips of the lower wall (broken lines) are visible;
Figure 5 is a cross sectional view of the side walls of the hollow body constrained to each other according to the plane H-H of figure 4;
Figure 6 is a simplified side view of the heat exchanger according to the present invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION

Referring to the attached figures 1 - 6 a preferred embodiment of the heat exchanger 1 according to the present invention will be now described. As visible in the side view of figure 6, the exchanger 1 comprises a container 2 inside which at least a first liquid and at least one rotor 3 rotatably constrained inside the container 2 are located. The rotor 3 comprises at least one hollow body 10 provided with at least two side walls 11 and 12 constrained to each other to form a hollow 13 within the same for the passage of at least a second liquid.
More in detail, as visible in figure 6, the rotor 3 is rotatably supported inside the container 2, or exchanger tank, and is fluidically linked with the outside as well by suitable joints 4 and 5 which allow the passage of the second liquid inside the rotor. Of course, the container 2 as well is provided with proper joints 6 and 7 for fluidically linking with the outside, and in particular for allowing the input and output of the first liquid to/from the container 2.
As visible in figure 6, preferably the rotor 3 comprises a central shaft 3a on which one or more hollow bodies 10 are constrained. Of course the number of hollow bodies 10 constrained to the rotor 3 of the exchanger 1 can vary depending on the needs, in fact, the larger is the number of hollow bodies, the larger the exchange surface between the two liquids involved in the heat exchange will be.
The first liquid passes within the container 2 of the exchanger contacting the outer surface of the hollow bodies 10, whereas the second liquid passes within the rotor 3 and the hollow bodies 10. The hollow body 10 constrained to the rotor 3 are rotated around an axis X, for example by means of an electrical motor 8 constrained outside the exchanger container 2.
As mentioned, each hollow body 10 comprises at least two side walls 11 and 12, and in the embodiment illustrated each hollow body 10 comprises two side walls 11 and 12 having convex outer surface such to form, when coupled, a hollow disc of substantially lenticular shape.
Preferably, the side walls 11 and 12 have circular shape and are constrained to each other in facing position thus forming a hollow body having substantially a disc shape. Preferably, the side walls 11 and 12 of the hollow body 10 are made of metal foils whose thickness can vary according to the constructive and use needs.
In particular, too great thicknesses are avoided since they would cause an excessive weight of the hollow body with the consequent handling difficulty, and in particular their rotation inside the exchanger.
On the other side the thickness can not be too reduced since, as mentioned, the hollow bodies are designed for internally and externally contacting the liquids involved in the heat exchange which can be filled under pressure, or according to pressurization and depressurization cycles.
Advantageously, as it will be more apparent in the following, the dips 20, 20' arranged on the side walls 11 and 12 of the hollow bodies 10 also serve to provide stiffness to the surface of the hollow body, therefore keeping the weight thereof limited while obtaining optimal performances in terms of mechanical strength.
It has to be noted as well that the side walls 11 and 12 can be formed by several portions constrained to each other or can be made in a single piece, for example by a unique properly shaped foil, as in the embodiment illustrated in figures.
The hollow bodies 10 formed as a consequence of the constraint of two side walls 11 and 12 are pierced at their central part to allow the passage of the shaft 3a of the rotor 3, and therefore so that they can be keyed thereon. Furthermore, the hollow bodies 10 comprise a flap 14 (see figures 3 and 4) outwards, at their central part, to allow the linking with adjacent bodies keyed in succession on the shaft 3a of the rotor 3.
At the flap 14 a pierced surface 15 is constrained (visible in figure 4) substantially parallel to the side walls of the hollow body such to allow to fluidically link a hollow body and the following one joined on the rotor 3.
As visible in figure 5, on the side wall 11 a portion 16 projecting at the central part is further arranged, which allows to constrain the hollow body with the subsequent. In fact, as visible in figure 5, the outer surface of the projecting portion 16 is shaped to allow the passage externally of the latter of the flap 14 of the hollow body mounted after it on the rotor 3.
According to an aspect of the present invention, at least one side surface 11, 12 of the hollow body 10 comprises at least one dip 20, 20'. More in detail, the side walls of the hollow bodies comprise one or more dips 20, 20' which form corresponding protrusions inside the hollow body when the two side walls are constrained to each other to form the hollow body.
In the preferred embodiment, illustrated in the figures, the dips 20, 20' are made on both the side walls 11 and 12 forming the hollow bodies 10. In detail, as it will be better explained in the following, each side wall 11 and 12 comprises a first and at least one second plurality of dips 20, 20', made for example by molding thereon.
Of course, other known processing technologies can be employed for making the dips 20, 20' on the side surfaces of the hollow body according to the present invention.
In the embodiment illustrated in figures, the hollow bodies 10 are formed by equal side walls 11 and 12, preferably having convex circular shape, which are constrained in a facing position. Therefore the arrangement, the number and the shape of the dips 20, 20' formed on the two side walls 11 and 12 are the same for the two side walls. Figures 4 and 5 show a portion of a hollow body 10 made by constraining two side walls 11 and 12 equal to each other.
Of course, according to further possible embodiment, the dips 20, 20' can be realized and arranged in different way on the side walls 11 and 12 which are constrained to each other for forming the hollow body, in terms of dimensions, shape and amount.
As visible in figures, the side walls 11 and 12 comprise at least one plurality of elongated dips 20, 20' extending along a line non - radial with respect to the rotation axis X.
Preferably, the side walls 11 and 12 comprise a first plurality of dips 20 and at least one second plurality of dips 20'.
It has to be noted that in the present description the radius, or the radial direction of the hollow body, is or will be referred in reference to the rotation center of the hollow body targeted by the X axis around which the rotor 3 rotates the hollow body.
As visible in figures, the dips 20, 20' are elongated and extend along a line joining at least two non aligned points on the same radius belonging to the side wall 11, 12. Based upon several experimental tests, the applicant could verified that the extension of the dips 20, 20' along a line arranged radially with respect to the rotation axis X has to be avoided since it would cause passages too much linear and straight for the liquid within the exchanger, thus remarkably reducing the efficiency thereof.
In other words, the line along which each elongated dip 20, 20' extends is not arranged along a radial direction and therefore does not lie on a radius of the side wall 11, 12 defined from the rotation axis X of the hollow body.
Preferably, the dips 20, 20' extend along a line joining at least two points arranged at a different distance with respect to the rotation axis X.
The dips can be either straight or curved, as in the embodiment illustrated in the figures in which they have an arched shape similar to the geometry of the impeller vanes which, as it will be better seen in the following, provides particular advantages in terms of reduction of the load losses generated within the exchanger.
According to an aspect of the present invention, the dips 20, 20' made on a side wall 11, 12 are overlapped in at least one point or area, 25, 26 contacting at least one dip 20, 20' arranged on another side wall of the hollow body. In other words, the dips on the two different side walls of the hollow body are arranged such to become overlapped in at least one contacting point or area 25.
In detail, according to a preferred embodiment, each of the side walls 11, 12 comprises at least one dip 20 of the first plurality of dips and the at least one second plurality of dips 20', and the dips 20, 20' arranged on a side wall are overlapped in at least one contacting point 25, 26 with at least one dip 20, 20' arranged on the other side wall 11, 12 of the hollow body 10.
It has to be observed that the contact, which preferably occurs at the lower surface of the overlapped dips, can either be direct and indirect, for example by the interposition of an inner wall or diaphragm inside the hollow body.
In figure 4, which as mentioned shows a hollow body formed by the constraint of the two side walls 11 and 12, the dips 20, 20' arranged on the wall 11 can be observed which are represented with solid lines, whereas the dips 20, 20' made on the side wall 12 are represented with broken lines.
Always referring to figure 4, the dips 20, 20' arranged on two different side walls have at least one contacting point 25, 26.
More in detail, the dips 20, 20' on a side wall have a contacting point 25, 26 in common with two different dips 20, 20' arranged on the other side wall.
Preferably, at least one dip of the first plurality of dips 20 of a side wall 11, 12 is overlapped with at least two different dips 20 of the first plurality of dips arranged on the other side wall 11, 12 of the hollow body 10.
Preferably the contacting points 25 are at the starting and ending portion of the line along which each dip 20 extends.
Such a particular structure allows to strengthen the hollow body 10 and thus make it more resistant with respect to the dip arrangements used in exchangers known in the art. Furthermore, it has to be noted that the contacting points 25, 26, between the dips 20, 20' arranged on opposite side walls 11, 12 of the hollow body allow to stiffen the structure thereof by forming areas in which the dip surfaces are overlapped, allowing an effective heat exchange without generating undesired load losses.
As it will be more apparent in the following, according to a preferred aspect of the present invention, at least one dip 20' of the at least one second plurality of dips, arranged on a first side wall 11, 12 of the hollow body 10, is overlapped and has at least one contacting point 26 with at least one dip 20 of the first plurality of dips arranged on another side wall 11, 12 of the hollow body.
More in detail, according to an aspect of the present invention, at least one dip 20' of the at least one second plurality of dips, arranged on a first side wall 11, 12 of the hollow body 10, is overlapped and has at least one contacting point 25, 26, with at least one dip 20 of the first plurality of dips and with at least one dip 20' of the second plurality of dips, arranged on another side wall 11, 12 of the hollow body 10.
Advantageously, the contacting points allow to form within the hollow body a pathway for the liquid passing within the same, without however causing the generation of undesired load losses.
Advantageously, the contacting points or areas 25, 26 of the overlapped dips 20,20' can be used for attaching constraining means 30 of the side walls for further stiffening and strengthening the hollow body.
In detail, at the contacting points 25, 26 of the overlapped dips, constraining means 30 of known type such as for example nails, rivets, welding points and the like can be installed. See in this regard figure 4 in which the constraining means 30 are visible at the contacting points or areas 25 of the dips 20.
Furthermore, according to a preferred embodiment each dip 20 arranged on a side wall is overlapped with three different dips 20, 20' arranged on another side wall of the hollow body, thus forming three different contacting points or areas 25.
Preferably, as visible in figures, a dip 20 belonging to the first plurality of dips, arranged on a side wall 11, is overlapped with two dips 20 belonging to the first plurality arranged on the other side wall 12 of the hollow body, as well as with a dip 20' belonging to the second plurality of dips arranged on the other side wall 12 of the hollow body.
In particular figure 4 shows three contacting points 25a, 26 and 25c of the dip 20d on the wall 11 respectively with three different dips 20a, 20' and 20c arranged on the other side wall 12 of the hollow body 10.
In detail, the dip 20' belongs to the second plurality of dips on the wall 12 of the hollow body 10, and it overlaps in a contacting point 26 with the dip 20d of the first plurality of dips arranged on the wall 11 of the hollow body 10.
Furthermore, the dip 20' belonging to the second plurality of dips on the wall 12 of the hollow body 10, is overlapped and has at least one contacting point with a dip 20' of the second plurality of dips arranged on the other side wall 11 of the hollow body 10. As visible in such a figure, the contacting point 26 of the dip 20' belonging to the second plurality of dips with the dip belonging to the first plurality of dips, arranged on another side wall of the hollow body, is arranged substantially at the lower end (closer to the rotation axis X) of the line along which the dip of the second plurality extends.
Of course, the dips can have more or less extended width both in terms of side development, indicated in figure 1 by the chord Y, and in terms of longitudinal development, indicated in figure 1 by the chord Z, which substantially indicates the extension from a point belonging to an inner circumference to a point belonging to an outer circumference on the side walls 11 and 12 of the hollow body measured from the rotation axis X.
As already mentioned at least one side wall of the hollow body comprises a first plurality of dips and one second plurality of dips having dimensions smaller than the dips of the first plurality of dips.
Advantageously, the presence of a first plurality of dips and at least one second plurality of dips allows to increase the efficacy of the exchanger without causing the formation of undesired load losses, so as it occurs in the exchangers known in the art, for example in the exchanger according to the document DE19615606 , due to the presence of a plurality of fins protruding within each hollow body.
In the attached figures it can be observed how the second plurality of dips extends substantially on a circular crown with extension smaller than the first plurality of dips which substantially extend on the whole surface of the circular crown of the side wall. In other words, the at least one second plurality of dips 20' extends substantially on a circular crown with smaller extension, that is to say with smaller area, with respect to the circular crown on which the first plurality of dips 20 extends.
Furthermore, as visible in the attached figures, the second plurality of dips 20' extends on a part of the side wall 11, 12 of the hollow body 10 radially spaced apart from the rotation axis X of the hollow body 10.
In detail, the circular crown on which the at least one second plurality of dips 20' extends is arranged at a radial distance from the rotation axis X of the hollow body 10 larger than the circular crown on which the first plurality of dips 20 extends.
In this way, the second plurality of dips 20' helps the stiffening, besides conveying the liquid, also next to a part, or circular crown, of the side wall 11, 12 of the hollow body spaced apart from the rotation axis X, and in general with respect to the part of the side wall on which the dips 20, belonging to the first plurality of dips, extend. As visible in figures, the dips 20 of the first plurality are interspaced with the dips 20' of the second plurality, having smaller dimensions.
This particular arrangement allows to obtain a larger number of dips arranged on opposite side walls 11 and 12 which are in contact with each other by forming a grid for the passage of the liquid within the hollow body while further strengthening the surface of the hollow body.
Such an arrangement offers remarkable advantages with respect to the exchangers known in the art, and in particular with respect to the typology described in the document DE19615606 , wherein the presence of the protruding fins arranged on the inner diaphragm causes an undesired weight increase in addition to the generated load losses.
In fact, as mentioned, according to a preferred embodiment, at least one dip 20' belonging to the second plurality of dips arranged on a first side wall of the body is overlapped and has at least one contacting point 26 with at least one dip 20 of the first plurality of dips arranged on another side wall of the hollow body.
As visible in figure 4, the dips 20' having smaller extension, that is to say the dips belonging to the second plurality, are overlapped in a substantially median, or central, point 26 of the dips 20 that have larger extension, that is to say the dips belonging to the first plurality. It becomes apparent that the formation of a contacting point 26 arranged in a substantially central point of the dip 20 having larger extension causes a further stiffening of the surface of the hollow body.
Furthermore, as visible in figure 4, a dip 20' belonging to the second plurality of dips on a side wall 11, 12 of the hollow body 10, is overlapped and has at least one contacting point 26a with a dip 20' of the second plurality of dips arranged on the other side wall 11, 12 of the hollow body 10. Preferably, the contacting point 26a between two overlapped dips 20' of the second plurality of dips, belonging to different side walls 11, 12 of the hollow body 10, occurs at the upper end of the lines along which such dips 20' extend.
As already mentioned above referring to the first plurality of dips, constraining means 30 can be installed at least at a contacting point between the lower surfaces of the overlapped dips arranged on two different side walls.
Furthermore, the exchanger according to the present invention is characterized in that the dips arranged on a first side wall 11 are arranged according to a first slope with respect to a radius of the hollow body and the dips 20, 20' arranged on another side wall 12 of the hollow body extend with a slope, with respect to a radius, opposite with respect to the dips arranged on the other side wall 11.
In fact, as visible in particular in figure 4, the dips 20, 20' on the first side wall 11 (represented by solid lines) extend slopingly rightwards with respect to a radius passing through the rotation axis X of the hollow body. Conversely, the dips 20, 20' arranged on the side wall 12 (represented by broken lines) are sloped leftwards with respect to a radius passing through the rotation axis X of the hollow body. Such a particular arrangement of the dips on the two facing and constrained side walls is obtained, as mentioned, by constraining two equal side walls, that is to say two side walls having the same pattern of the dips which are constrained facing each other.
As mentioned, the dips 20, 20' are arched such to substantially take the geometrical shape of vanes of a centrifugal impeller, and when two side walls are constrained to each other, the arched dips are sloped according to two opposite directions on the two walls 11 and 12.
Therefore the fluid dynamic behavior of the liquid in which the hollow bodies are submerged will be different from a side wall to another of the hollow body. In particular, the fluid dynamic behavior of the dips can be theoretically considered the behavior due to the "forward vanes" and "rearward vanes" of an impeller. In this way the formation of a centrifugal force acting on the liquid contained in the container 2 of the exchanger can be determined differently depending on the face (side wall) of the concerned hollow body, this resulting in the generation of high pressure regions and low pressure regions at the two side walls of the same hollow body and between the walls of two adjoining hollow bodies. The high pressure and low pressure regions come in succession along the whole length of the exchanger. Therefore the feeding motion of the liquid in the container 2 of the exchanger is aided with respect to the exchangers known in the art.
In particular, the heat exchanger according to the present invention is provided with baffles 9 installed inside the container 2 between two hollow bodies 10 arranged in succession on the rotor 3. The particular arrangement of the dips 20, 20' allows to aid the liquid displacement within the container without generating excessive load losses and without the need of removing some baffles as it occurs in the heat exchangers known in the art and currently used.
Furthermore, the generated load losses can be remarkably reduced, also in case in which the liquid located inside the exchanger container has high density or is particularly viscous.
The arrangement of the dips 20, 20', and in particular their arched shape with opposite slope on the two side walls 11 and 12, in addition to the presence of the second plurality of dips 20' having smaller extension illustrated in the figures, allows to significantly improve the efficiency of the heat exchanger in which the so made hollow bodies are installed.
Furthermore, the center distance can be reduced with the same generated load losses, that is to say the distance between two adjoining hollow bodies arranged in succession on the shaft 3a of the rotor 3 of the exchanger, so to obtain exchangers having more compact dimensions with the same performances and heat exchange efficacy. Furthermore, the particular arrangement of the hollow bodies and dips arranged on their side walls allows to increase the turbulent state of the liquid located inside the exchanger container effectively improving the efficacy of the heat exchange with the liquid passing inside the hollow bodies.
It has to be noted as well that the turbulence increase inside the exchanger container allows to improve the self-cleaning characteristics of the exchanger since the solid residuals contained within could be kept entrained over the liquid surface.

Claims

Heat exchanger (1) for liquids of the type comprising a container (2) inside which at least a first liquid is located and at least one rotor (3) rotatably constrained inside said container, said rotor comprising at least one hollow body (10) provided with at least two side walls (11, 12) constrained to each other to form a hollow space (13) within them for the passage of at least a second liquid, said at least one hollow body (10) being rotated around an axis (X), wherein at least one of said side walls (11, 12) comprises a first plurality of elongate dips (20) extending along a non - radial line with respect to said rotation axis (X), characterized in that said at east one side wall (11, 12) of said at least one hollow body (10) comprises at least one second plurality of dips (20') having dimensions smaller than the dips of the first plurality of dips (20).
Heat exchanger according to claim 1, wherein the dips (20) of said first plurality are interspaced with said dips (20') of said second plurality having smaller dimensions.
Heat exchanger according to claim 1 or 2, wherein said at least one second plurality of dips (20') extends substantially on a circular crown having an extension smaller than a circular crown on which said first plurality of dips (20) extends.
Heat exchanger according to claim 3, wherein said circular crown on which said at least one second plurality of dips (20') extends, is arranged at a radial distance from said rotation axis (X) of said hollow body (10) larger than said circular crown on which said first plurality of dips (20) extends.
Heat exchanger according to any one of the preceding claims, wherein each one of said at least two side walls (11, 12) comprises at least one dip (20, 20') of said first plurality of dips (20) and said second plurality of dips (20'), the at least one dip (20, 20') made on a side wall (11, 12) being overlapped in at least one contacting point (25, 26) with at least one dip (20, 20') arranged on the other side wall (11, 12) of said hollow body (10).
Heat exchanger according to claim 5, wherein said at least one dip (20) of said first plurality of dips of a side wall (11, 12) is overlapped with at least two different dips (20) of said first plurality of dips arranged on the other side wall (11, 12) of said hollow body.
Heat exchanger according to claim 5 or 6, wherein said at least one contacting point (25) of said overlapped dips (20) of said first plurality of dips, belonging to different side walls (11, 12), is substantially arranged at an end of said line along which said at least one dip (20) of said first plurality of dips extends.
Heat exchanger according to any one of the claims 5 to 7, wherein said at least one dip (20) of said first plurality of dips of a side wall (11, 12) is overlapped with three different dips (20, 20') arranged on the other side wall (11, 12) of said hollow body (10), two dips (20) belonging to said first plurality of dips and the third dip (20') belonging to said at least one second plurality of dips.
Heat exchanger according to any one of the claims 5 to 8, wherein at least one dip (20') of said second plurality of dips arranged on a first side wall (11, 12) of said body (10), is overlapped and has at least one contacting point (26) with at least one dip (20) of the first plurality of dips arranged on another side wall (11, 12) of said hollow body.
Heat exchanger according to claim 9, wherein said at least one contacting point (26) of at least one dip (20') of said at least one second plurality of dips arranged on a first side wall (11, 12) of said body (10) with at least one dip (20) of the first plurality of dips arranged on another side wall (11, 12) of said hollow body, is substantially arranged in a substantially central position of said line along which said at least one dip (20) of said first plurality of dips extends.
Heat exchanger according to any one of the claims 5 - 10, comprising constraining means (30) of said overlapped dips (20, 20') belonging to side walls (11, 12) different in said at least one contacting point (25, 26).
Heat exchanger according to any one of the preceding claims, characterized in that said at least two facing constrained side walls (11, 12) are equal to each other.
Heat exchanger according to any one of the preceding claims, wherein said at least one hollow body (10) comprises two convex circular side walls (11, 12) constrained to each other to form a hollow disc of lenticular shape.
Heat exchanger according to any one of the preceding claims, characterized by comprising two or more hollow bodies (10) arranged in succession on said rotor (3), said two or more hollow bodies being fluidically linked to each other to allow the passage of said at least a second liquid therebetween.
Heat exchanger according to any one of the preceding claims, characterized by comprising at least a baffle (9) inside said container (2), said at least one baffle (9) being located between said at least two hollow bodies (10).