Tube bundle heat exchanger with multi-level spraying system

Abstract

The present invention relates to a heat exchanger configured with a distribution device of the cooling fluid at several vertical levels into a tube bundle suitably organized in groups of tubes insisting on such vertical levels.

Description

[0001] TUBE BUNDLE HEAT EXCHANGER WITH MULTI-LEVEL SPRAYING SYSTEM

[0002] DESCRIPTION

[0003] Technical field of the invention

[0004] The present invention relates to the field of the apparatuses for the heat treatment of fluids, in particular the apparatuses suitable to the use in industrial air conditioning systems.

[0005] The present invention, more in detail, relates to a tube bundle heat exchanger, in particular an evaporator, which implements a multi-level system for spraying the cooling fluid flow on the tube bundle.

[0006] Background

[0007] As it is known, the tube bundle heat exchangers have several problems affecting the size and design of the evaporator.

[0008] Generally, a problem of the evaporators is that of obtaining a wished thermal efficiency, sizes and technical complexity being equal.

[0009] Therefore, a technical object is to increase the thermal efficiency of the heat exchanger with structurally simple and economically advantageous solutions.

[0010] Several factors affect the efficiency of these machines.

[0011] For example, one of the main operating limits of the evaporators, such as for example in the flooded and spray type evaporators, is represented by the dragging of a liquid component in the flow for sucking the fluid used as cooling fluid. In fact, this involves a loss in the available refrigeration capacity since if, on one side, a portion of the cooling fluid exits the evaporator in liquid phase the latter could not have contributed to the heat exchange, by affecting the apparatus efficiency. In the most serious cases, the liquid dragging involves further significant damages to the circuit placed downstream of the suction, in particular to the mechanics of the compression units.

[0012] A known solution to avoid the liquid dragging provides to increase the overheating of the fluid during suction at the evaporator exit. This solution, although very effective and simple to be implemented (it does not require additional components) is very expensive since it involves an oversizing of the evaporator. In order to obtain the overheating of the cooling fluid, in fact, it is necessary to increase the heat exchange surfaces and then the overall sizes of the evaporator, by increasing considerably the costs.

[0013] It is also known to size the evaporator in order to limit the liquid dragging and to keep the gas flows within predetermined conditions. Even in this case one proceeds with oversizing the evaporator and mechanical elements are used, suitable to uniform the inner gas flows. As for the previously described solution, by introducing additional inner components and / or by oversizing the sizes to reduce the suction flow speed, the evaporator cost increases.

[0014] Other solutions provide the use of “intermediate” heat exchangers in order to dry the suction flow. In other words, the use of an additional heat exchanger, outer or inserted in the evaporator itself, is provided, in which the hot liquid coming from the high-pressure line circulates and so as to allow an additional heat exchange with the humid gas exiting the evaporator.

[0015] At last, it is also known to use liquid separating means installed downstream of the suction, but upstream of the inlet in the compression units. Although these are generally cheap solutions, which operate well in protecting the compressor against high liquid dragging transients, these configurations are not useful in case the liquid dragging is constantly above a limit threshold.

[0016] Moreover, although each one of the above-illustrated solutions can have advantages, all of them have in common the drawback of a not negligible cost increase, associated to the refrigerator implementation.

[0017] Still, an additional factor affecting the exchanger efficiency is linked to the homogeneous spraying of the cooling fluid in general, even in particular of its liquid phase, on the tube bundle. In fact, if such homogeneous spraying does not take place, the wished heat exchange is not obtained.

[0018] In standard flooded type evaporators the cooling fluid, generally sprayed from the bottom, submerges the tube bundle by favouring the liquid interaction with the exchange tubes to the detriment of the overall amount of charge the same.

[0019] Within the evaporators of so-called “falling film” and “spray” type, according to the known solutions, the distribution of the cooling fluid mainly takes place from a portion above the tube bundle, in a spraying direction traditionally from top towards the bottom. However, this type of spraying does not solve the technical problem of spraying the fluid so that the tube bundle is wetted thereby uniformly.

[0020] In fact, it is unquestionable that this configuration allows to wet sufficiently well the surface of tubes placed directly facing the spraying devices or generally the surface of the upper portion of the bundle, but it is not as effective in wetting the tube bundle portion placed therebelow.

[0021] There are also solutions providing a configuration interposed between spraying devices and pipes, in a “rhombus”-like arrangement which provides each spraying device surrounded by four tubes. These solutions, if on one side try to obtain a more uniform distribution of the cooling fluid, on the other side complicate considerably the geometry of the machine and of the system connected thereto, with an evident increase in the production costs.

[0022] The type of nozzle, used to distribute the service fluid on the tube bundle, too affects the spraying homogeneity. Even the nozzle, then, is an element which can be susceptible to improvements in order to increase the overall performance of the evaporator.

[0023] Summary of the invention The technical problem placed and solved by the present invention is then to provide a heat exchanger, in particular an evaporator, allowing to obviate one or more of the drawbacks mentioned above with reference to the known art.

[0024] Such problem is solved by a heat exchanger according to the enclosed independent claims.

[0025] Preferred features of the invention are set forth in the dependent claims.

[0026] Brief description of figures

[0027] The figures of the enclosed drawings will be referred to, wherein:

[0028] ■ Figures 1 and 2 show, each one, a schematic side view of a first configuration of a heat exchanger wherein operating regions of outflow and representative of the active principle of the present invention are highlighted, respectively according to a first and a second embodiment of the heat exchanger itself;

[0029] ■ Figure 3 shows a schematic view in front section of a preferred embodiment of the heat exchanger according to the present invention;

[0030] ■ Figure 4 shows a schematic view of an assembly consisting of the distribution means and of the directional means of the fluid flow of the exchanger illustrated in Figure 3 and according to a preferred embodiment of the present invention;

[0031] ■ Figure 5 and Figure 6 show, each one, structural details of the assembly illustrated in Figure 4.

[0032] ■ Figure 7 shows a partial and isometric schematic view of the heat exchanger according to a preferred embodiment of the invention, implementing the assembly shown in Figure 4 and the lines of fluid flow during suction;

[0033] Figure 8 shows a schematic view in front view of Figure 5;

[0034] Figure 9 and Figure 10 show, respectively, an example of refrigerating cycle explaining the inventive principle, the invention relates to, and a course graph exemplifying operating parameters of the distribution means;

[0035] ■ Figure 11 represents schematically a second configuration of heat exchanger and in particular of a distribution device of the cooling fluid installed therein;

[0036] ■ Figure 12 represents more in detail a preferred embodiment of the second configuration of heat exchanger represented in Figure 11 and in particular it is a cross section view of the exchanger;

[0037] ■ Figure 13 is a front view of an embodiment of the exchanger of Figure 12 with some portions of the exchanger omitted for better representation clarity;

[0038] ■ Figure 14 shows a front view of a first embodiment variant of a nozzle suitable to be used for spraying a cooling fluid in a heat exchanger;

[0039] ■ Figure 15 is a longitudinal section view of the nozzle of Figure 15, wherein an annular chamber of the nozzle itself is visible;

[0040] ■ Figure 16 shows a second embodiment variant of nozzle, represented in a perspective view;

[0041] ■ Figure 17 is a longitudinal section view of such second embodiment variant of nozzle, represented in a perspective view too.

[0042] Detailed description of preferred embodiments

[0043] In general terms, the present description relates to a heat exchanger, of the tube bundle type, which uses as first operating fluid - or process fluid, preferably water (pure water or water in solution) and as second operating fluid - or service fluid - preferably a cooling fluid, such as for example hydrofluorocarbons (HFC), hydrofluorolefins (HFO) or fluids with similar properties.

[0044] The cooling fluid in contact (or, concurrently, for convection phenomena) with the tube bundle, removes heat energy from the process fluid circulating inside the tubes of said bundle, by cooling it down.

[0045] The heat exchanger is designated as a whole with reference number 100, 100’. The exchanger 100, 100’ is preferably a heat exchanger of the so-called “flooded” or “spray” type, in particular an evaporator.

[0046] The exchanger 100, 100’ comprises a tube bundle, designated with reference number 1 , T, intended to allow internally a circulation of the first operating fluid through corresponding openings 11 and 12 and it has a prevalent extension of development along a longitudinal direction A.

[0047] The tube bundle 1 , T preferably engages a tube sheet 13 configured to supply said tube bundle 1 , T with the process fluid. Such configuration is within the comprehension of the person skilled in the art and therefore one will not further dwell upon it.

[0048] The exchanger 100, 100’ further comprises a casing, or skirt, 2, 2’ suitable to allow a circulation of the cooling fluid inside thereof. The casing 2, 2’ surrounds said tube bundle 1 , T. The casing 2, 2’ is watertight and it is suitably sized to operate at the design pressures. As it can be seen in the illustrated examples, the casing 2, 2’ extends in the same longitudinal direction A of development of the tube bundle 1 , T which is contained inside thereof.

[0049] The casing 2, 2’ internally defines a heat exchange chamber 3, 3’, inside which chamber 3, 3’ there is the tube bundle 1. Such chamber 3, 3’ has a base region B and a top region S. The tube bundle 1 , T is positioned, or extends, at said base region B.

[0050] The heat exchange chamber 3, 3’ further houses inside thereof distribution means, designated as a whole with reference number 4, 4’. The distribution means 4, 4’ is configured to receive internally the cooling fluid and to spray it in said chamber 3. More precisely, said distribution means 4, 4’ is configured to spray such fluid so that it performs a first heat exchange with the tube bundle 1 .

[0051] In the operation as evaporator, as shown by the arrows D in Figure 1 and 2, the entering cooling fluid, typically in liquid or biphasic (liquid and vapour) form is sprayed in the base region B of the chamber 3, 3’ where there is the tube bundle 1 , T, it evaporates in a first heat exchange which takes place with the process fluid present inside said bundle 1 , T and, then rises, as designated by the arrow E, towards an outlet opening 21 , 2T carried by the casing 2, 2’ to exit the heat exchange chamber 3, 3’.

[0052] Let’s now go into details of a first configuration of the heat exchanger, represented in figures 1 to 10.

[0053] In such first configuration the distribution means 4 results to be positioned inside the heat exchange chamber 3 and it has to be placed at the top region S of the latter.

[0054] The configuration of the exchanger 100 is so that the outlet opening 21 results to be positioned downstream of said distribution means 4 according to the exit direction E of the fluid so that the distribution means 4 allows a second heat exchange with such fluid exiting the chamber 3.

[0055] In this embodiment, the distribution means 4 is interposed between the outlet opening 21 and the tube bundle 1 so that the fluid rising from the base region B has necessarily to hit the distribution means 4, for example by coming in contact with an outer surface of the structure of the distribution means, and it has to perform an additional heat exchange before being able to flow through the outlet opening 21. Preferably, the casing 2 carries said outlet opening 21 in position opposite to said base region B.

[0056] As previously mentioned, said second heat exchange guarantees the evaporation of the liquid component and / or the drying of the vapour component of the fluid exiting the exchanger 100, by preventing to drag the liquid outside the heat exchange chamber 3.

[0057] As shown in Figures 1 and 2, the rising of the fluid after the first heat exchange with the tube bundle 1 can provide different paths towards the outlet opening 21 . The fluid, for example, can be sucked exclusively from an area R of the heat exchange chamber 3 substantially facing the outlet opening (Figure 2) or it can travel through the top region S along the relative (complete or partial) extension inside the exchange chamber 3 before crossing the outlet opening 21 (as designated by the dotted box in Figure 1 ). Generally, additional (different) paths can be provided depending upon the type and shape of the distribution means adopted to spray and, indeed, to distribute the fluid inside the heat exchange chamber 3. Specific examples in this regard will be illustrated in more details hereinafter.

[0058] The distribution means can include one or more fluid supply connections 4’ and the casing 2 carries respective one or more openings 22 for such supply. Going back to Figures 3-8, a preferred embodiment, not limiting the above-said distribution means 4, is then illustrated.

[0059] In a specific embodiment example of the embodiment of the first exchanger configuration, the distribution means 4 comprises a tubular element 40 acting as supply collector and the outer surface thereof 40a provides for the heat exchange with the fluid present in the chamber 3.

[0060] In a representative example, the tubular element 40 is implemented as one single conduit.

[0061] In an additional representative example, the tubular element 40 in case can include a plurality of conduits connected by junction elements. In this way it is advantageously possible to increase the heat exchange outer surface 40a with the fluid coming from the base region B. According to preferred variants, the outer surface 40a comprises fins and / or recesses to further favour the heat exchange with the fluid, not illustrated.

[0062] Still in the illustrated example, the distribution means 4 extends in the top region S longitudinally and parallelly to the direction of development A of the tube bundle 1 and of the heat exchange chamber 3. However, such longitudinal configuration is not essential to obtain the technical effects described above, but it is preferable since it allows to reduce the cost of the component itself. Therefore, alternative embodiments of the distribution means are not then excluded.

[0063] Advantageously, the exchanger 100 comprises pressure drop means configured to establish a predetermined pressure difference between the internal pressure existing in the distribution means 4 and the internal pressure existing in the heat exchange chamber 3. The above-mentioned pressure difference results in an always greater internal pressure PD of the distribution means 4 than an internal pressure PS of the heat exchange chamber 3.

[0064] Preferably, said pressure drop means comprises one or more openings, such as for example nozzles 41 and / or orifices 42, carried by the distribution means 4 themselves.

[0065] The pressure drop means and, in particular such openings 41 , 42, are then suitably sized to introduce a pressure drop at the inlet of the heat exchange chamber 3 and then to guarantee a suitable temperature difference between the inner environment, and the outer environment, of the distribution means 4 themselves.

[0066] In order to explain the advantageous technical effect associated to such arrangement let’s make now further reference to Figure 9 wherein an example of refrigerating cycle is shown in the enthalpy-pressure thermodynamic graph and a hypothetical temperature present inside the distribution means 4 by fixing a predetermined pressure drop. Figure 10, moreover, shows a temperature different (DT) course graph of the distribution means 4 depending upon the internal pressure difference (DP) between the latter and the heat exchange chamber 3 for four curves representing the behaviour of corresponding refrigerant fluids.

[0067] From such graphs it can be seen that, differently from the known solutions bringing back to configurations of evaporators of the type the present invention relates to, wherein the load losses are generally lower than 1.5 bar and corresponding to a temperature difference between the inside and the outside of the distribution means lower than 10 Kelvin, the openings 41 , 42 of the distribution means 4 are sized so as to introduce load losses (depending upon the type of used cooling) even higher than 4 bar, thereto more than twice of the temperature difference (DT), obtainable with the already mentioned known solutions, corresponds.

[0068] The efficiency values between the exchanger the invention relates to and an exchanger adopting one of the above-illustrated known solutions being equal, the fact of obtaining high values of temperature difference (DT) of the distribution means 4 advantageously allows to reduce the surface assigned to the “auxiliary” heat exchange arranged to contrast the dragging of liquid during suction, by making the unit simpler and cheaper and by reducing significantly the probability that a residual liquid component of the fluid flow could exit the chamber 3 without having exchanged heat.

[0069] According to a preferred embodiment, the heat exchanger 100 implements directional means of the fluid flow positioned in the heat exchange chamber 3 and configured to direct the exiting fluid towards the distribution means 4.

[0070] The fact of providing directional means advantageously increases the interaction probability between the fluid flow in the (second) heat exchange with the distribution means 4, by further reducing the risk of dragging the liquid exiting the chamber 3.

[0071] An embodiment exemplifying said direction means is clearly visible in Figure 4 and designated with the reference number 5.

[0072] In the illustrated example, the directional means comprises a plate-like element 5 fixed to the casing 2 and oriented in such a way as to confine therebetween la base region B and the top region S of the heat exchange chamber 3. In particular, a first face 5s of the plate-like element 5 is directed towards the top region S and a second face 5b, opposite to the first face, is directed towards the base region B. The plate-like element 5 is fixed preferably to an inner wall of the casing 2.

[0073] It should be noted that the base region B and the top region S are in fluid communication therebetween to allow the passage of the fluid rising towards the outlet opening 21. The confinement, then, is intended to limit said regions spatially and not flu id ically and so that the directional means 5 could address (at least the liquid component of) the cooling fluid towards the distribution means 4. Such fluid communication is preferably obtained through one or more openings 51 obtained in the plate-like element 5 so as to force the path of the fluid towards the outlet opening 21 upon crossing from the base region B to the top region S in predetermined areas of the heat exchange chamber 3, as it can be seen from the arrows shown in Figures 7 and 8.

[0074] In particular, with additional reference to Figures 5 and 6, said one or more openings 51 face the distribution means 4 and are distributed along a direction A’ parallel to the direction A of longitudinal development of the casing 2 and / or of the tube bundle 1 . Preferably, the directional means 5 develops along the whole extension of the distribution means 4. The plate-like element 5 for example can have a shape with V-or ll-like profile, as in the illustrated example, with respect to its own direction of development. The openings 51 can have sizes and shapes different therebetween.

[0075] A preferred embodiment provides a combined use of distribution means 4 with mainly longitudinal development in combination with directional means 5 along its complete extension, to make more uniform the cooling flows coming from different areas of the base region B.

[0076] In a possible embodiment variant of such configuration, the above-mentioned openings, such as in particular the nozzles 41 and / or the orifices 42 are placed on portions 43 projecting from the tubular element 40 towards the base region B.

[0077] In case, such portions 43 can be provided at the above-mentioned junction means 40” in case the distribution means 4 is implemented like a tubular element 40 consisting of a plurality of conduits 40’ connected therebetween.

[0078] Still, for example, the portions 43 extend through one or more corresponding one of said one or more openings 51 of the plate-like element 5.

[0079] The heat exchanger, the enclosed claims relate to, then allows in particular to limit to drag the liquid component of the fluid flow during suction by reducing significantly, or annulling, additional cost items associated to the manufacturing of the exchanger and with respect to the standard solutions. According to an additional aspect, the invention then provides a heat exchanger and a method of drying a fluid in a tube bundle exchanger which allows to obtain improved performances in terms of overall efficiency of heat exchange.

[0080] Differently from the known solutions in which the fluid is sprayed on the tube bundle and subsequently it flows directly during suction, the heat exchanger as claimed comprises, as described above, distribution means which results to be interposed between the tube bundle and the fluid suction, by performing a dual active function in two separated phases of the operation of the heat exchanger itself. The cooling fluid then flows at first inside the distribution means to be then sprayed in the chamber so as to obtain a first heat exchange with the tube bundle and, subsequently, it rises towards the top region to obtain a second heat exchange by hitting said distribution means, for example by coming in contact with the outer surface of the latter, before exiting the chamber through the suction opening.

[0081] Advantageously, the exchanger comprises pressure drop means configured to establish a suitable internal pressure difference between the distribution means and the heat exchange chamber. It will be appreciated that the proposed solution exploits the apparent disadvantage of having load losses upon spraying the fluid in the heat exchange chamber to raise advantageously the temperature of the fluid distributing means, in particular at a higher predetermined temperature than the room temperature inside the heat exchange chamber, and then to obtain a temperature difference so as to allow a second heat exchange between the fluid exiting the chamber and the distribution means itself.

[0082] Such second heat exchange then guarantees the evaporation of the liquid component and / or drying of the vapour component of said fluid exiting the exchanger.

[0083] Moreover, the solution, the invention relates to, advantageously provides a configuration integrated inside the heat exchanger without the need for arranging auxiliary (intermediate) heat exchangers to contrast the liquid dragging phenomenon, to the full advantage of construction simplicity and compactness.

[0084] In other terms, such configuration allows to integrate a system and a method for treating the fluid inside the heat exchanger without modifying the layout of the refrigerating circuit with respect to a standard configuration.

[0085] The above-mentioned type of known solutions, in fact, is expensive in terms of manufacturing and bulky since the auxiliary exchangers are typically housed in a separate chamber inside the heat exchange chamber, implemented as waterproof units supplied by the same cooling fluid coming from the condenser (which precedes the lamination valve, which is normally positioned upstream of spraying in the heat exchange chamber). The known solutions that make use of auxiliary exchangers then require the implementation of at least an additional inlet and an additional outlet for the fluidic circuit (of the auxiliary exchanger) in the evaporator structure, by making also structurally complex the structure of the latter and the pipes associated to the system. Additionally, in case of malfunction or failure, such as a fluid loss, the procedures for repairing the systems with auxiliary exchangers are difficult to be performed and require a complete replacement of said auxiliary unit and related interruption of the operation of the evaporator or of the system itself.

[0086] Differently, a possible loss of cooling fluid from the distribution means of the invention could affect, in case, the quality of the fluid flow distribution in the heat exchange chamber, however guaranteeing the evaporator operation since said fluid could however flow inside the skirt.

[0087] Advantageously, it is then possible to obtain a solution with improved heat exchange efficiency through a simple heat exchanger structure, structurally cheap and reliable even upon considering its compactness since it reduces significantly the risk of dragging liquid during suction.

[0088] ***

[0089] As mentioned above, even the distribution of the cooling fluid on the tube bundle 1 has an important role in the performance of the heat exchanger. In fact, it is necessary that the tubes are wetted suitably and uniformly. In fact, considering that the heat which can be exchanged along the tube is substantially stable, the amount of fluid sprayed thereon has to be as uniform as possible in order to make the most of all available heat exchange surface.

[0090] Figures 11 to 13 show a second exchanger configuration trying to solve this problem, with the aim of distributing in a satisfactorily uniform manner the service fluid on the bundle of tubes in which the process fluid circulates.

[0091] Such exchanger configuration can be put in the field of the flooded-spray evaporator exchangers, that is evaporator exchangers in which at least a portion of the tube bundle is not flooded (that is immersed in the cooling fluid) but involved by the cooling fluid through a spray type spraying.

[0092] Going more in details, the second proposed configuration provides distribution means or more shortly a distribution device 4’ of a fluid, meant as the already above-described cooling or service fluid.

[0093] With reference in particular to figure 11 , the distribution device 4’ comprises means 4T for spraying the cooling fluid and in particular at least one 41’n of such spraying means is placed inside the tube bundle T at a respective vertical spraying level nVL.

[0094] For the purposes of understanding the text, under vertical a direction substantially perpendicular to the direction of longitudinal development A of the tube bundle T, designated with Y in figure, is meant.

[0095] The at least one 41’n of the spraying means places inside the tube bundle by dividing it into two groups of tubes, a lower group 1 ’inf placed at a lower vertical lever than the respective vertical spraying level nVL and an upper group 1’sup, placed at a higher vertical level than the respective vertical spraying level nVL.

[0096] Each one of the two groups of tubes, the lower 1 ’inf and upper 1’sup one, comprises at least two horizontal rows of tubes.

[0097] Still, the lower group of tubes 1’inf and the upper one 1’sup are mutually spaced-apart on the vertical direction Y, to define a vertical gap Gn. Under gap a portion of the tube bundle without tubes is meant.

[0098] The portion without tubes Gn has a development according a horizontal direction perpendicular to the vertical direction.

[0099] At least one 41 ’n of the spraying means is then arranged between the two lower 1 ’inf and upper 1 ’sup groups of tubes at this gap Gn and it is arranged to spray the fluid on the upper 1 ’sup group of tubes and / or on the lower 1 ’ inf group of tubes through such vertical gap Gn.

[0100] The vertical gap Gn places at the respective spraying level nVL of at least one of the spraying means.

[0101] In a preferred embodiment solution the spraying level nVL is arranged in the centre of the vertical development of the gap Gn.

[0102] Still, the distribution device 4’ comprises at least a first distribution conduit 43’ which extends at least partially inside the tube bundle T and which carries at least one 41 ’n of the spraying means.

[0103] The first conduit 43’ extends substantially vertically.

[0104] Consequently, the vertical gap Gn between the two lower and upper groups of tubes is arranged orthogonally to the first conduit 43’.

[0105] A preferred embodiment variant of this second exchanger configuration provides that the distribution device 4’ comprises a second conduit 40’, arranged along the longitudinal direction A, then substantially horizontally and essentially parallelly to the tube bundle T.

[0106] The second conduit 40’ runs above the tube bundle T, in the top region S of the exchanger.

[0107] Preferably the distribution device 4’ comprises two or more of such first conduits 43’ connected to such second horizontal conduit 40’.

[0108] The number of first conduits 43’, for example, is linked to the length of the exchanger. Let’s now make reference in particular to figures 12 to 13 which describe a preferred embodiment of such exchanger configuration.

[0109] In this example, the distribution device comprises spraying means 41 T which places at a first vertical spraying level 1VL, for sake of simplicity in the text called first spraying means. The first spraying means 41 T then divides the tube bundle T into two groups of tubes: a first 1’a group of tubes is arranged below the first vertical spraying level 1VL, whereas a second 1’b group of tubes is arranged above the first vertical spraying level 1VL.

[0110] By convention in the present description under first spraying means 41 T the ones located further down in the exchanger will be meant, that is the ones closest to the base region B.

[0111] Between the first group 1’a of tubes and the second group 1’b of tubes a first gap G1 is defined, arranged astride the first spraying level 1VL, and through which at least one of the first spraying means sprays the cooling fluid.

[0112] In the present description by convention the numbering of the elements will be applied in an ascending order rising vertically with respect to the tube bundle. It is obvious that other conventions could be used (for example a numbering starting from top), therefore such indication is not to be meant as limiting the interpretation of the present description and technical solution.

[0113] The distribution device can further include spraying means 412’ arranged at a second spraying level 2VL placed above the first spraying level 1 VL, for sake of simplicity called in the description second spraying means. Such second spraying means 412’ has a group of tubes placed below the respective vertical spraying level which corresponds to the above-mentioned second group of tubes 1’b and a group of tubes placed above the second spraying level 2VL, that is a third group of tubes 1’c. In this case between the second and third group of tubes a second gap G2 is defined, placed at the second spraying level 2VL and through which the second spraying means 412’ sprays the cooling fluid.

[0114] In the solution illustrated in figures, the spraying means 413’ is provided at a third higher spraying level 3VL than the second vertical spraying level 3VL; analogously, for sake of simplicity in the description they will be designated as third spraying means. Such third spraying means insist on the above-mentioned third group of tubes 1’c placed below the third vertical spraying level and on a fourth group of tubes 1’d, placed above the third vertical spraying level. Therefore, a third gap G3 is defined between the third and fourth group of tubes, placed at the third vertical spraying level 3VL and through which the third spraying means 413’ sprays the fluid.

[0115] In such embodiment, even the second and third spraying means 412’, 413’ are arranged on the same first conduit 43’ of the first spraying means.

[0116] It is obvious that various solutions can be provided, with a variable number of spraying means, vertical spraying levels and groups of tubes.

[0117] As mentioned, the distribution device can include several first conduits 43’.

[0118] Preferably, the spraying means is associated in number of one for each level to each first conduit. Therefore, the first spraying means 41 T associated to the first spraying level 1VL present in the distribution device is in number corresponding to the number of conduits 43’ and so on analogously for all second, third and subsequent spraying means.

[0119] By going further in detail, the second conduit 40’ can be for example, but not limitedly, in the form of the above-described tubular element or collector 40.

[0120] The second conduit 40’ then can be implemented by one single tubular conduit or by a plurality of conduits connected by junction elements.

[0121] The first conduits 43’ can be for example for example, but not limitedly, in the form of the above-described portions of pipe 43; as mentioned above, these can be arranged at the above-mentioned junction means 40 in case the distribution means 4 is implemented as a collector 40 consisting of a plurality of conduits 40 connected therebetween.

[0122] Still, figure 13 illustrates an example of distribution device 4’ comprising a second horizontal conduit 40’, four first conduits 43’ which extend vertically from such horizontal conduit. Each first conduit defines three spraying levels, then it comprises first, second and third spraying means, for a total of four first spraying means, four second spraying means and four third spraying means.

[0123] Going back to the tube bundle, the first group of tubes 1’a places on the bottom of the exchanger, that in the base section B. During the use of the exchanger, such first group 1’a is usually at least partially immersed in the service fluid. In fact, a design parameter of the exchanger is the level of the service fluid stagnant on the bottom of the same.

[0124] In this case it is provided that the first spraying means 41 T could spray the fluid preferably towards the second group 1’b of tubes arranged thereabove.

[0125] However, this does not exclude that other solutions may exist in which such bottom group 1’a is not immersed in the service fluid or however not wholly immersed and then the first spraying means 41 T distributes the cooling fluid towards both groups of tubes, that is the second group 1’b of tubes arranged on the higher side and the first group 1’a of tubes arranged on the lower side.

[0126] In a preferred solution the spraying means described in the present configuration of exchanger are nozzles.

[0127] Still, in an additional solution such nozzles spray the fluid with a main spraying direction substantially orthogonal to the first conduit 43’.

[0128] Solutions are also provided, in which the distribution device 4’ comprises spraying devices in addition to the above-described (not shown) spraying means.

[0129] For example, but not limitedly, such additional spraying devices can be directly placed on the horizontal conduit 40’ and then involve the tube bundle 1’ with a fluid spraying from top.

[0130] Alternatively, but not limitedly, such additional spraying devices can be placed on the first conduit 43’, at an upper end thereof and mainly insist on one single group of tubes placed therebelow. Even such additional supply devices can be nozzles.

[0131] In an embodiment solution, the two horizontal rows composing each group are arranged one on top of the other one and mutually spaced apart by a lower amount than the vertical gap between the respective groups. This means that the rows of tubes in each group are approached therebetween.

[0132] As mentioned above, the horizontal conduit can have several shapes and sizes. In particular, the size of the cross section of the horizontal conduit is selected to avoid flow speed of the cooling fluid which could involve mechanical erosion, bad distribution of the fluid along the conduit itself due to the flow inertia and to decrease the production costs.

[0133] Analogously even the vertical conduits have a section coherent with the involved flows and they are spaced apart therebetween in order to guarantee an adequate and satisfying fluid covering in the different vertical spraying levels. In fact, if upon increasing the number of the first conduits and spraying means even the fluid covering can increase, however also a considerable cost increase takes place.

[0134] The spraying means is selected to manage the distribution of the fluid in the different spraying levels mainly based upon the geometry of the sprayed fluid bundle and upon the working conditions. On this regard, the spraying means at each vertical spraying level can be even different therebetween in type and / or size depending upon needs.

[0135] The number of spraying levels mainly depends upon the number of rows of tubes of the tube bundle. As mentioned above, if on one side the increase in spraying levels can involve an increase in the distribution of the bundle, on the other side it also involves a cost increase.

[0136] It is also to be noted that, in case, the arrangement of the distribution means 4’ with respect to the outlet opening of the exchanger as described in the first exchanger configuration can be applied even in this second configuration. In fact, nothing prevents that even the distribution device 4’ as described in the second configuration is interposed between the outlet opening 21 and the tube bundle 1 , that is arranged so as to be hit by the fluid rising from the base region B towards the outlet direction E so as to allow a second heat exchange with such fluid exiting the chamber 3. Alternatively, even embodiment solutions are provided in which the distribution means in this second configuration is arranged in different position.

[0137] Such second exchanger configuration solves the placed technical problem to increase the thermal efficiency through a better and more uniform distribution of the cooling fluid on the tube bundle.

[0138] The known solutions, in fact, with spraying of the cooling fluid from top to bottom, then with a rain-like spraying on the tube bundle were not satisfying since they failed to wet uniformly all bundle tubes, especially those placed in the central portion thereof.

[0139] On the contrary, thanks to the described configuration the spraying of the cooling fluid takes place inside the bundle itself, then reaching the outer surface of the tubes even inside the bundle.

[0140] Moreover, thanks to the fact that the tubes are divided into groups spaced vertically therebetween, it is possible to spray the fluid directly even on the outer surface of the tube directed towards the bottom of the exchanger. It is clear that with a rain-like spraying from top such lower portion of the tube is never directly wetted adequately. Therefore, such configuration has even the additional advantage to increase the active heat exchange surface and as consequence to increase the exchanger efficiency.

[0141] ***

[0142] Let’s now consider figures from 14 to 17 which describe a possible solution of nozzle 6 applicable both to the first and second heat exchanger configurations described above.

[0143] Such nozzle 6 reaches significant results in terms of performance in particular if applied to the second exchanger configuration.

[0144] It always aims at increasing performances, wherein such increase is directly correspondent to the capability of spraying the cooling fluid homogeneously.

[0145] By going further in detail, the technical problems linked to this type of component, affecting the performances thereof, are several.

[0146] One thereof for example is linked to the load losses which can be significantly affected by the fact that the sprayed cooling fluid is commonly biphasic, that is it carries one liquid component and one gaseous component.

[0147] This affects the nozzle spraying field, that is its capability of spraying at a wished distance and covering a wished area, apart from the quality of the distribution of the fluid on the tubes.

[0148] Therefore, the proposed nozzle solution aims at solving such problems.

[0149] According to the proposed solution the nozzle 6 comprises an annular chamber 60 defined between two walls arranged coaxially to one another: a first wall 6a and a second wall 6b.

[0150] The first wall 6a has substantially tubular shape and defines a radial direction A’, an axial direction Y and a circumferential direction (not shown in figures) which forms with the other two a Cartesian triple. Still, hereinafter in the text, under transversal plane a plane perpendicular to the radial direction A’ will be meant.

[0151] The second wall 6b is arranged spaced apart from the first wall along the radial direction of a distance s.

[0152] The first tubular wall 6a limits an inner space 600 in which the cooling fluid coming from an outer (not shown) supplying system flows.

[0153] The first wall 6a carries at least an inlet opening 61 to the annular chamber 60. Through such at least an inlet opening 61 the cooling fluid flows from such inner space 600 to the annular chamber 60.

[0154] The second wall 6b, in turn, carries outlet means 62’, 62”, or means for exiting the fluid, involving circumferentially the second wall itself 6b. The outlet means allows the fluid present in the annular chamber to be sprayed towards outside.

[0155] The first tubular wall 6a, in an embodiment solution, is the outer wall of a conduit of the distribution device 4, 4’. Such conduit can be in the shape of the conduit 43 or the first conduit 43’.

[0156] The inner space limited by the first tubular wall is then represented by the compartment inside the conduit 43, 43’.

[0157] The second wall 6b, in a preferred embodiment solution illustrated in figures, develops parallelly and coaxially to the first wall 6a.

[0158] Still, the inner wall 6a defines an outer surface 6a‘ and the outer wall 6b defines an inner surface 6b’, the one mutually facing the other one and both of them directed towards the inside of the chamber 60.

[0159] The annular chamber 60 is further limited by additional walls 6c, 6d which develop between the first tubular wall and the second wall.

[0160] The first wall, the second wall and the additional walls are preferably impermeable for the service fluid. Alternatively, it is possible that even only one section of such walls is impermeable for the cooling fluid, section facing such at least one opening to the chamber and to the distribution means.

[0161] In the illustrated solution the additional walls are two, a lower one 6c limiting the chamber on the lower side with reference to the axial development Y and an upper one 6d, limiting the chamber on the upper side, still with reference to the axial development Y.

[0162] It is clear that “upper” and “lower” are references which can also be taken in the opposite way without compromising the understanding of the proposed solution.

[0163] Still, each one of the additional walls arranges substantially radially, that is perpendicularly to the first tubular wall 6a.

[0164] In the illustrated example the additional upper wall defines a deflector for the flow exiting the annular chamber 60. Such additional upper wall 6d, in fact, is arranged in proximity of the fluid outlet means and directs the fluid circulating in the chamber 60 towards them.

[0165] In a preferred embodiment solution, the deflector directs the fluid in a mainly radial outlet direction.

[0166] The outlet means 62’, 62”, in the illustrated example, is arranged on the second wall 6b spaced apart axially with respect to the at least an opening 61 . This solution allows that the fluid circulates inside the chamber 60 before exiting it; such circulation contributes to mix the fluid carrying, in case, one liquid component and one gaseous component.

[0167] In the illustrated solution the outlet means 62’, 62” face a section of the first wall 6a and consequently the at least an inlet opening 61 faces a section of the second wall 6b. As mentioned above, such sections are impermeable for the fluid so that, in order to exit the chamber, it has no other way but to pass through the distribution means.

[0168] It is to be noted that other geometries can be provided, in fact it is not certain that the second wall is parallel to the first one or that the additional walls are in number of two and / or arranged radially. Therefore, also solutions can be provided in which the distribution means, and by analogy the at least an opening, faces sections of the additional walls.

[0169] Still, the distribution means can have various shapes.

[0170] In a first solution represented in figures 14 and 15 the outlet means comprises one single through-slot 62’ which develops peripherally on the second wall 6b. The only slot develops on one single vertical level that is astride the plane transversal to the axial direction.

[0171] However, solutions are provided in which the only slot 62’ can develop by involving even several vertical levels or the only slot develops on a plane having a certain tilting with respect to the transverse plane.

[0172] Such solution of nozzle with only one slot allows to obtain a more homogeneous fluid spraying, distributed on 360°. In a second solution, represented in figures 16 and 17, the outlet means comprises a plurality of slots 62” where such plurality arranges peripherally to the second wall 6b. Preferably, but not limitedly, each slot 62” of such plurality is arranged tilted with respect to a transverse plane. The tilting of each slot is a variable parameter selected depending upon the specific spraying needs.

[0173] Such configuration allows to have a jet sprayed with a certain tilting and then it obtains a better spraying cover even in axial direction.

[0174] In a preferred embodiment variant, the first wall comprises a plurality of inlet openings 61 , arranged peripherally. Such inlet openings can be implemented by holes or slots. Alternatively, the opening can be single such as a slot running circumferentially on the first wall 6a.

[0175] The sizing of the openings (or of the opening) in the sense of their number, their sizes, etc. affects the amount of cooling fluid entering the annular chamber.

[0176] In the represented examples, the chamber inlet openings are positioned near the additional lower wall 6c. This allows to enter the fluid inside the chamber 60 in the position more distant from the outlet, by forcing it to circulate longer inside the chamber and then by contributing to a better mixing.

[0177] However, there can be also solutions in which the openings (or the opening) are positioned axially in a different point. For example, but not limitedly, the openings (or the opening) could arrange in position more proximate to the axial half of the development of the chamber itself or to the outlet itself of the annular chamber.

[0178] As mentioned above, the circulation of the fluid inside the chamber allows the mixing thereof. In fact, it is common that the cooling fluid is in a gas-liquid biphasic state.

[0179] The fluid enters the chamber at high speed (commonly in range comprised between 5 and 30 m / s). This high inlet speed is a further factor which can contribute to the subsequent mixing of the fluid inside the chamber. As already mentioned, the first wall 6a can be a portion of wall of a conduit 43, 43’ such as those described previously. In this case a specific radial direction A’ coincides with the direction of longitudinal development A of the tube bundle, whereas the axial direction Y is meant as the vertical direction, of development of the conduit 43, 43’ with respect to the tube bundle.

[0180] Thanks to the fact that the proposed nozzle has a fluid spraying preferably and mainly directed in radial direction, such nozzle results to be particularly effective if associated to the above-described second exchanger configuration, since it can spray the fluid mainly through the vertical gaps separating the various groups of tubes in which the tube bundle is organized.

[0181] ***

[0182] The present invention has been sofar described with reference to preferred embodiments. It is to be meant that other embodiments belonging to the same inventive core may exist, as defined by the protective scope of the herebelow reported claims.

Claims

CLAIMS1. A heat exchanger suitable to be used as evaporator, comprising: a plurality of parallel tubes (T) arranged substantially horizontally, the tubes having an outer surface, a distribution device (4’) to distribute a cooling fluid on the outer surface of said tubes, the distribution device comprising at least one of means (41’n) for spraying said fluid placed at a respective vertical level of spraying (nVL), wherein such respective vertical level is placed into the plurality of tubes (T) by dividing it into two groups of tubes, a lower group (1 ’inf) situated at a lower vertical level than said respective vertical spraying level and an upper group (1’sup) placed at a higher vertical level than said respective vertical spraying level, wherein said lower group of tubes and said upper group of tubes comprise, each one, at least two horizontal rows of tubes.

2. The heat exchanger according to claim 1 , wherein said lower group (1’inf) and said upper group of tubes (1’sup) are vertically spaced apart by defining a gap (Gn).

3. The heat exchanger according to claim 2, wherein said at least one of the spraying means is arranged to spray the fluid on said second group of tubes and / or on said lower group of tubes through said gap (Gn).

4. The heat exchanger according to claim 1 , 2 or 3, wherein said distribution device (4’) comprises at least a first conduit (43’) extending at least partially into the plurality of tubes (T) and said at least one of the spraying means is arranged on said at least a first conduit (43’).

5. The heat exchanger according to claim 4, wherein said at least a first conduit (43’) extends substantially vertically.

6. The heat exchanger according to claim 5, wherein said distribution device comprises a second conduit (40’) extending substantially horizontally and parallelly to the tubes of said plurality.

7. The heat exchanger according to claim 6, wherein from said second conduit (40’) two or more of said first conduits (43’) extend.

8. The heat exchanger according to claim 7, wherein each one of said first conduits (43’) comprises at least one (41’n) of said spraying means arranged at its own respective vertical spraying level.

9. The heat exchanger according to any one of claims 3 to 8, wherein said distribution device comprises at least a first one (41 T) of spraying means arranged at a first vertical spraying level (1VL) and at least a second one (412’) of spraying means, arranged at a second vertical spraying level (2VL) wherein said second vertical spraying level is arranged above the first one.

10. The heat exchanger according to claim 9, wherein a first group of tubes (1’a) is defined lower than said first vertical spraying level (1VL), a second group of tubes (1’b) is placed above said first vertical spraying level (1VL) and said first and second group of tubes are spaced apart vertically to define a first gap (G1 ) through which said at least one (41 T) of first spraying means sprays.

11. The heat exchanger according to claim 10, wherein a third group of tubes (1’c) is placed above said second vertical spraying level (2VL), said third group of tubes being spaced vertically with respect to said second group of tubes (1’b) by defining a second gap (G2) through which said at least one (412’) of second spraying means sprays.

12. The heat exchanger according to claim 9, 10 or 11 , wherein said at least one of first spraying means and at least one of second spraying means are arranged on a same first conduit (43’) of said distribution device.

13. The heat exchanger according to any one of claims 9 to 12, further comprising at least one (413’) of third spraying means, arranged at a third vertical level (3VL) above said second vertical spraying level.

14. The heat exchanger according to claim 13, wherein said at least one of third spraying means, said at least one of second spraying means and said at least one of first spraying means are arranged on a same first conduit of said distribution device.

15. The heat exchanger according to claim 14, wherein a fourth group of tubes (1’d) is arranged above said third vertical level and it is spaced vertically from the third group of tubes to define a third gap (G3) through which said at least one of third spraying means sprays.

16. The heat exchanger according to any one of claims 9 to 15, wherein said first group of tubes (1’a) is arranged at a base region (B) of said exchanger and at least partially immersed into said cooling fluid.

17. The heat exchanger according to claim 16, wherein said at least one of first spraying means is configured to spray fluid through said first gap (G1 ) mainly on said second group of tubes (1’b) placed above said first vertical spraying level.

18. The heat exchanger according to any one of the preceding claims, wherein additional spraying means is provided placed directly on said second horizontal conduit (40’) or at an upper end of said first conduit to spray said plurality of tubes with a fluid spraying from top.

19. The heat exchanger according to any one of the preceding claims, wherein each one of said spraying means is a nozzle.

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