condenser

Abstract

The invention provides a shell and tube type condenser (100, 200) for transfer-ring energy from a refrigerant fluid to a service fluid comprising -an essentially cylindrical shell (110, 210) comprising an inlet (111, 211) for refrigerant fluid in a super-heated vapor state on an upper side and an outlet (112, 212) for completely condensed, slightly subcooled refrigerant fluid on a lower side; - a plurality of tubes (121, 122, 221, 222) for the service fluid, said tubes (121,122, 221, 222) passing through the essentially cylindrical shell (100, 200) extending essentially parallel to the cylinder axis of the essentially cylindrical shell (100,200), said tubes (121, 122, 221, 222) being connected to each other in such a way that service liquid flowing through said tubes (121,122, 221, 222) is led N times inside the tubes (121,122, 221, 222) through the essentially cylindrical shell (100, 200), wherein N is a natural number and N>1; - a number of M longitudinal metal sheets (150, 250) extending from an end of the essentially cylindrical shell (110, 210) and defining in the essentially cylindrical20 shell (110, 210) M+1 passageways (113,114, 213, 214) so that refrigerant fluid makes M+1 passes along tubes (121,122, 221, 222) for the service fluid, wherein M is a positive natural number; wherein the area of the respective cross sections (A1, A2) of the M+1 passageways (113,114, 213, 214) in the direction orthogonal to the cylinder axis of the essentially cylindrical shell (110, 210) decreases from the topmost passageway (113, 213) to the lowest passageway (114, 214).

Description

[0001] Condenser

[0002] A typical application of shell-and-tube type heat exchangers is their use within a vapor compression refrigeration cycle . In this application, the condenser has the function of allowing a trans fer of energy from the refrigerant fluid to the service fluid, normally tower water, sea water or di f ferent types of brine , so that the refrigerant coming from the compressor in the superheated vapor state is first desuperheated to a saturated condition, then completely condensed and finally slightly subcooled .

[0003] Therefore , inside a heat exchanger generally referred to as a " condenser" , three fundamental heat exchange processes actually take place :

[0004] • a single-phase vapor / single-phase liquid heat exchange process between two fluids in the de-superheating section,

[0005] • a two-phase vapor-liquid / single-phase liquid ( in the actual condensation section) , and finally

[0006] • a single-phase liquid / single-phase liquid heat exchange process in the sub-cooling section .

[0007] The three sections j ust described in a functional manner rarely have a clear ef fective physical delimitation within the most used heat exchangers , a delimitation possibly achieved through a particular design / construction choice which may involve the use of additional components such as sheets with or without holes that somehow guide the flow and create separate areas inside the heat exchanger, characteri zed by the main presence of only one of the 3 heat exchange mechanisms highlighted above .

[0008] In practice , there are di f ferent designs that are able to sep- arate / insulate the sub-cooling section of the liquid quite well , however the separation of the vapor de-superheating section is much more complex .

[0009] Therefore , although the heat exchange mechanisms present in the " condenser" component are multiple and very di f ferent from each other, the most widespread design choices are in reality very simple , without speci fic measures for the di f ferent sections and guided by the cost / benefit constraint typical of reference application .

[0010] In a Shell and Tube condenser, generally the service fluid flows inside the tubes in the so-called " tube-side" , while the refrigerant flows outside the tubes in the so-called " shellside" . The service fluid, that could be water or di f ferent types of brine , enters through an inlet connection into a distribution chamber of the so-called front header, this distribution chamber being a volume created by the header itsel f and by a first tube sheet , a perforated metal plate in whose holes the heat exchange tubes are fixed from one of their ends through various possible procedures ( expansion, welding, . . . ) . From the distribution chamber the service fluid is distributed inside the heat exchange tubes fed ( connected) by this distribution chamber and passes through them in what is called " a passage" until it exits the tubes on the opposite side of the heat exchanger and is collected in another collection chamber consisting of the volume created between a rear header and the second tube sheet to which the second ends of the tubes are fixed . In the case of a single-pass tube-side condenser, the front header will have only one connection, namely the inlet connection, and the rear header will have also only one connection, namely the outlet connection . In the case of a 2-pass tube-side condenser, the front header will have both the inlet and outlet connections and the volume between the header and the first tube sheet will be divided into 2 chambers completely separated from each other by a partition . In this way, the service fluid entering the first chamber ( distribution chamber ) will be distributed inside only the tubes connected to this chamber and will perform a " first pass" inside them . Upon exiting these , the service fluid will be collected in a chamber created by the volume enclosed between the rear header and the second tube sheet and inside it it will be able to reverse its direction ( return chamber ) redistributing itsel f inside the tubes not af fected by the " first pass" which will instead constitute the path of the " second pass" of the service fluid . Once the " second pass" has been performed, upon exiting the tubes the service fluid will connect to the second chamber of the front header and will be released out of the condenser through an outlet connection .

[0011] Condensers can be classi fied both based on the number of water ( service fluid) passages inside the tubes ( " tube side" ) , and on the number of refrigerant passages in the space delimited by the shell , the external surface of the tubes and the tubesheets where the tubes are fixed ( " Shell side" ) . The most used configurations , of fering a good compromise between heat exchange performance and construction costs , have a single refrigerant pass configuration on the shell side and di f ferent water configurations on the tube side , generally 1 , 2 , 3 and 4 water passes on the tube side . The configuration with a single refrigerant passage on the shell side and a single water passage on the tube side , a configuration generally referred to as " counter-current" , is the one that optimi zes the temperature profiles of the two fluids and is therefore the one that allows the use of the smallest heat exchange surface for the same thermal power to be exchanged and inlet and outlet temperatures of the two fluids .

[0012] This configuration is also the one that manages to obtain a minimum " approach" between water outlet temperature and condensation temperature with the same thermal power exchanged and heat exchange surface .

[0013] The disadvantage of this configuration is that despite using the best tube technologies available on the market , to design a condenser optimi zed for a high ef ficiency chiller application, therefore with a reduced temperature " approach" between the 2 fluids , it is necessary to use very long tubes , often exceeding 4 meters , thus creating large units .

[0014] The single pass condensers of the refrigerant side on the shell side and an even number of water passes on the tube side ( 2 and 4 passes are the most used) , have the great advantages of shortening the overall length of the heat exchanger and having both water connections on the same side , facilitating the piping layout of the end user . These are the main reasons why they are widely used, despite their less than optimal performance .

[0015] One of the main limitations of shell-side single-pass refrigerant and tube-side multi-pass water condensers ( 2 , 3 , 4 , . . . ) , which does not allow them to achieve optimal performance , is that of not having a perfectly counter-current heat exchange configuration between the two fluids for the entire heat exchange surface , a condition that can instead be obtained with a configuration with a single refrigerant passage on the shell side and a single water passage on the tube side .

[0016] To better understand this concept , we can analyze for simplicity the configuration with a single refrigerant pass on the shell side and two water passes on the tube side : the cold water enters the lower inlet connection, flows inside the tubes of the lower portion of the tube bundle and then, having reversed its direction of travel in the rear cap, in the second passage it crosses the upper section of tubes of the tube bundle before leaving the heat exchanger through the outlet connection at a warmer temperature , having absorbed energy from the refrigerant fluid .

[0017] The refrigerant fluid, which in turn must be condensed and slightly subcooled, usually enters at the state of superheated vapor inside the shell through an inlet connection positioned in the upper area of the shell , in a longitudinal position ( along the hori zontal axis parallel to that of the tubes ) generally close to the end opposite to that of the water inlet : through the external surface of the tubes the refrigerant fluid will give heat to the water flowing inside the tubes , and after having been cooled to the saturation condition, it will begin to condense and be collected in the form of liquid in the lower part of the shell , flooding a portion of the tubes of the tube bundle and in this way undergoing a progressive sub-cooling process exchanging heat with the flooded tubes , crossed inside from the colder water . The liquid refrigerant leaves the heat exchanger through an outlet connection generally positioned in the lower part of the shell and positioned on the water inlet side , precisely to facilitate the subcooling process .

[0018] The overall heat exchange mechanism of the configuration j ust described can be considered good but not optimal i f compared with the configuration with a single refrigerant passage on the shell side and a single water passage on the tube side , in which the condition of counter-current heat exchange can be achieved for the entire heat exchange surface , optimal condition for the temperature profiles that are generated between the two fluids .

[0019] In fact , in the 2-pass water configuration on the tube side described above , the hottest outgoing water will not exchange heat with the refrigerant fluid at the maximum temperature , but with the refrigerant fluid at the saturation temperature , lower than the maximum temperature of the superheated vapor, the latter present instead at the refrigerant inlet connection positioned on the opposite side to the water outlet .

[0020] A second limitation that af fects all the configurations , is that the refrigerant , crossing the free space on the shell side from one side of the heat exchanger to the other side , gradually condenses and thus reduces its velocity both in the vapor phase and in the liquid phase , with a double negative ef fect :

[0021] 1 . the reduction of the velocity of the vapor also reduces the vapor shear ef fect and its positive consequences on the heat exchange coef ficients : a high vapor shear ef fect favors the reduction or total elimination of the condensate film on the external surface of the tube and the modi fication of the way the liquid flows between the tubes of the tube bundle result- ing in a flow of small drops of liquid dispersed in the vapor flow; and

[0022] 2 . the reduction in the velocity of the vapor consequently also reduces the velocity of the underlying liquid phase and with it the heat exchange coef ficient in the sub-cooling section .

[0023] CN 2890783 Y discloses a condenser that attempts to solve the problems related to low refrigerant velocity flow by adopting a multiple refrigerant passage configuration on the shell side , with a number of refrigerant passages equal to that of the water on the tube side . This configuration was implemented using longitudinal plates that guide the flow of the refrigerant into the shell side .

[0024] However, this implementation may present the following problems :

[0025] • di f ficulty in avoiding the by-pass of the longitudinal sheet by the superheated vapor which in this way reaches the refrigerant outlet connection after a short distance without having been completely condensed . I f simply placed next to the Shell or tube sheets , the longitudinal sheets do not guarantee a low value or the total elimination of this by-pass . Furthermore , any fixing by welding presents considerable di f ficulties in implementation in the case of heat exchangers with a length exceeding two meters and a small shell diameter ;

[0026] • di f ficulty in assembling the longitudinal sheet in the presence of support baf fles in the case of condensers having tube lengths such as to require the use of these baf fles to avoid vibration problems ;

[0027] • excessive pressure drops on the refrigerant side , which cancel out the positive ef fects of the perfectly countercurrent configuration created, i f the shell-side plates are positioned in correspondence with the partitions used in the water-side headers (precisely to achieve a perfectly counter-current flow between the two fluids . I f you simply place the shell side longitudinal plates symmetrically ( as well as the partitions in the water side headers ) , ef fectively creating various longitudinal passage sections (parallel to the tubes ) with a free passage section substantially the same or very similar to each other, the free section for the first refrigerant passage will present excessive pressure drops in the initial part of the heat exchanger where the flow is mainly made up of superheated vapor ( low density) , while in the final part of the last passage , where the flow is mainly made up of subcooled liquid (high density) , the free section will be too abundant and the velocity at which the liquid passes through will be too low . In the intermediate free sections an intermediate situation will be created between the two j ust described, but in any case not optimal ; therefore the implementation j ust described will bring negligible benefits or even negative ef fects compared to a single passage refrigerant side configuration without longitudinal baf fles .

[0028] The invention proposed allows an improvement in the heat exchange performance of a shell-and-tube condenser thanks to the adoption of a shell-side multiple refrigerant passage configuration which allows the entire heat exchange surface to work in an optimal condition from a temperature profile perspective (practically a condition equivalent to a pure countercurrent heat exchange ) even in configurations with an even number of water passes on the tube side : the implementation of this innovation is such as to optimi ze the overall heat exchange performance thanks to a lower variability of the velocity of the vapor . Advantageous embodiments can reduce problems induced by unwanted wetting of tubes with condensed refrigerant the presence of refrigerant by-passes and / or the presence of vibration problems of the tubes .

[0029] The shell and tube type condenser of the present invention is typically used for trans ferring energy from a refrigerant fluid to a service fluid . It comprises an essentially cylindrical shell which has an inlet for refrigerant fluid in a superheated vapor state on an upper side and an outlet for completely condensed, slightly subcooled refrigerant fluid on a lower side . In this context , it should be noted that the orientation of a shell and tube type condenser is well defined; the side on which the refrigerant fluid enters the condenser has to be its upper side for physical reasons and can be clearly identified in any practical application .

[0030] In addition, the shell and tube type condenser according to the present invention also comprises a plurality of tubes for the service fluid, said tubes passing through the essentially cylindrical shell extending essentially parallel to the cylinder axis of the essentially cylindrical shell . Said tubes are connected to each other in such a way that service liquid flowing through said tubes is led N times inside the tubes through the essentially cylindrical shell , wherein N is a natural number and N>1 . Evidently, in order to lead service liquid N times through the essentially cylindrical shell in said tubes , N tubes can be interconnected with each other with the connection taking place on alternating sides of the essentially cylindrical shell . This can in principle be obtained directly by providing connections , but in practice this is usually obtained indirectly by providing a common volume between a head plate and a tube sheet supporting the end sections of the tubes to which all tubes that are to contribute to a given pass of service liquid towards said head plate and the subsequent return pass of service liquid are connected .

[0031] Preferably, N is an even number, which allows for arranging service liquid inlet and service liquid outlet on the same side of the condenser .

[0032] Furthermore , the shell and tube type condenser of the present invention comprises a number of M longitudinal metal sheets extending from an end of the essentially cylindrical shell and defining in the essentially cylindrical shell M+ l passageways so that refrigerant fluid makes M+ l passes along tubes for the service fluid, wherein M is a positive natural number .

[0033] As the refrigerant fluid is to make M+ l passes along tubes for the service fluid in the thus configured arrangement , it is clear that on the other end of the essentially cylindrical shell there is a pass-through, so that the refrigerant fluid can propagate into the next passageway below the passageway through which it j ust propagated . The easiest way to create this pass-through is using a metal sheet whose length is shorter than the length of the essentially cylindrical shell .

[0034] Advantageously, the metal sheets extend from the ends of the essentially cylindrical shell in an alternating way, i . e . the next metal sheet always extends from the end opposite of the end from which the previous metal sheet extends i f M>1 .

[0035] According to the invention claimed in this patent , the area of the respective cross sections of the M+ l passageways in the direction orthogonal to the cylinder axis of the essentially cylindrical shell decreases from the topmost passageway to the lowest passageway . The easiest way to achieve this is a reduction of the distance between the respective neighboring longitudinal metal sheets from the top to the bottom; i f M=1 the longitudinal metal sheet is arranged in the lower hal f of the essentially cylindrical shell .

[0036] Due to this speci fic positioning of the longitudinal metal sheets , shell-side multi-pass refrigerant configurations , with substantially countercurrent heat exchange configurations from the point of view of the temperature profile of the two fluids are created, which at the same time improve the global heat exchange performance , benefiting from the average increase in the velocity of the vapor in the various passageways on the shell side and reducing the negative ef fect of the additional refrigerant pressure drops related to this increase in velocity .

[0037] In a preferred variant of such a shell and tube condenser, M=1 and 0 , 3 < A2 / A1 < 0 , 99 , wherein Al is the cross section of the top passageway and wherein A2 is the cross section of the bottom passageway . Even better ef fects are obtained i f these values meet the conditions M=1 and 0 , 3 < A2 / A1 < 0 , 65 , wherein Al is the cross section of the top passageway and wherein A2 is the cross section of the bottom passageway . For condensers used in Systems for air conditioning, refrigeration and heat pump applications , the most interesting configuration is the shell-side two-Pass refrigerant configuration with a single longitudinal metal sheet and thus M=1 . In these systems , the optimal positioning of the single longitudinal metal sheet that divides the total number of tubes in the tubesheet into two sets is dependent on the type of tube used, the length of the tube , the number of tubes , the si ze of the Shell , and the mass flow rate of refrigerant . For typical values of these parameters , optimal results are obtained i f the above-described conditions are met .

[0038] According to an advantageous embodiment of the invention, the shell an tube condenser comprises tubes for the service fluid that are in the same refrigerant passageway that belong to di f ferent passes of the service fluid . In other words , the inventors have found that set of tubes belonging to the same refrigerant passageway does not necessarily coincide with a set of tubes belonging to the same water passage , therefore the positioning of the longitudinal sheet does not necessarily coincide with the positioning of dividers in the water side headers .

[0039] According to another aspect , which is useful as an embodiment of the claimed invention but is also considered to represent an independent invention that achieves positive ef fects in condensers in which the condition regarding the si ze of the cross sections that is present in claim 1 is not met , the shell and tube condenser has one or more baf fle plates which are arranged in at least one of the passageways . These baf fle plates can be used to obtain several advantageous ef fects : They can simpli fy the construction and assembly operation, provide mechanical support to tubes as well as longitudinal metal sheets and remedy vibration problems that can be encountered in shell and tube condensers . These mechanical aspects can be emphasi zed i f the shell and tube condenser comprises a baf fle plate that extends through more than one passageway and maximi zed i f at least one of the baf fle plates extends through all of the passageways .

[0040] Moreover, in configurations with di f ferent numbers and types of baf fles for di f ferent refrigerant passages , in addition to these mechanical aspects , they can help to increase the heat exchange coef ficient on the shell side . For example , in the case of a multi-pass configuration with number of refrigerant passes >2 , in the last pass the refrigerant could be almost totally in the liquid phase and the adoption of a greater number of baf fles which favors a transversal flow with respect to the tube bundle can facilitate subcooling and increase the overall performance of the heat exchanger .

[0041] This ef fect can be emphasi zed for example by adopting a "disks and donuts" type baf fle configuration to avoid excessive pressure drops , i . e . a baf fle configuration wherein a first baf fle plate located in a passageway comprises a central void and a neighboring second baf fle plate located in the same passageway covers said void . This has the function to guide the flow in meandering manner around the tubes .

[0042] According to yet another aspect , which is useful as an embodiment of the claimed invention but is also considered to represent an independent invention that achieves positive ef fects in condensers in which the condition regarding the si ze of the cross sections that is present in claim 1 is not met , at least one of the longitudinal metal plates has a crest line extending parallel to the longitudinal axis and inclined slopes con- necting said crest line to the walls of the essentially cylindrical shell , so that the liquid collected on this longitudinal metal plate flows towards the walls of the essentially cylindrical shell and propagates from there towards a free end of this longitudinal metal plate . Due to the inclined shaping of the metal sheet , the assembly of other devices to be adopted for the lateral anti-bypass seal can be simpli fied and during operation the outflow of the condensed refrigerant fluid is improved .

[0043] Further advantages of this characteristic shape of the metal sheet are that of allowing two lateral areas for accumula- tion / passage of the liquid refrigerant , substantially free of tubes belonging to the section of the upper tube bundle ( tubes involved in the first passage on the refrigerant side ) , in such a way as optimi ze performance of condensation and consequently the fact that this liquid accumulated on the sides of the metal sheet , once it reaches the end of the metal sheet itsel f , will fall into the area below, minimi zing the rewetting of the tubes present in the second refrigerant passage , thus not adding any further thickness to the liquid film of the portion of the tubes of the second refrigerant passageway having the main function of condensing, and simply adding to the liquid which completely floods the complementary portion of the lower tubes with the main function of subcooling .

[0044] According to yet another aspect , which is useful as an embodiment of the claimed invention but is also considered to represent an independent invention that achieves positive ef fects in condensers in which the condition regarding the si ze of the cross sections that is present in claim 1 is not met , a lowered seat is created in the contact region between the metal plate and the walls of the essentially cylindrical shell , and / or in correspondance of tube sheets . This facilitates the welding operation of the longitudinal metal sheet to the tube sheet to allow an improved sealing between the two components and thus to avoid the presence of refrigerant by-passes between longitudinal sheet and tube sheet .

[0045] According to yet another aspect , which is useful as an embodiment of the claimed invention but is also considered to represent an independent invention that achieves positive ef fects in condensers in which the condition regarding the si ze of the cross sections that is present in claim 1 is not met , a lateral sealing gasket is provided in the contact region between the longitudinal metal plate and the walls of the essentially cylindrical shell . As a consequence , refrigerant by-passes between longitudinal sheet and the shell can be avoided even more ef fectively .

[0046] Another criterion that influences the dimensioning of the respective refrigerant passageways is that preferably in the in the M+ l passageway, i . e . the lowest passageway, the refrigerant fluid enters still in a two-phase status and exits in a subcooled one .

[0047] Next , the invention is explained in more detail referring to figures that illustrate speci fic embodiments of the invention . For sake of simplicity, examples with two refrigerant passes and two service fluid (water ) passes are used, i . e . in the examples M=1 and N=2

[0048] The figures show :

[0049] Fig . 1 : A typical configuration for use of condenser ; Fig. 2: a cross section of a first example of a shell and tube condenser of figure 1;

[0050] Fig. 3a: a baffle plate of the shell and tube condenser of figure 2;

[0051] Fig. 3b: a tube sheet of the shell and tube condenser of figure 2 ;

[0052] Fig. 4a: a first alternative for the tube sheet of figure 3b;

[0053] Fig. 4b: a second alternative for the tube sheet of figure 3b;

[0054] Fig. 5: A cross section of a second example of a shell and tube condenser;

[0055] Fig. 6a: a first type of baffle plate of the shell and tube condenser of figure 5;

[0056] Fig. 6b: a second type of baffle plate of the shell and tube condenser of figure 5;

[0057] Fig. 7a: a cross section through a third example of a tube and shell condenser;

[0058] Fig. 7b: a first variant of a seal for the tube condenser of Fig. 6a; and

[0059] Fig. 7c: a second variant of a seal for the tube condenser of Fig. 6a.

[0060] Figure 1 shows a typical configuration of a system 1 comprising a shell and tube condenser 10 according to the invention, wherein water is used as the service liquid . The cold water enters the lower inlet connection 11 , flows inside the tubes (which are not visible in Figure 1 ) of the lower portion of the tube bundle and then, having reversed its direction of travel in the rear cap 12 , in the second passage it flows through the tubes of the upper section of tubes of the tube bundle before leaving the shell and tube condenser 10 through the outlet connection 13 at a warmer temperature having absorbed energy from the refrigerant fluid .

[0061] The refrigerant fluid which in turn must be condensed and slightly subcooled by the shell and tube condenser 10 , usually enters at the state of superheated vapor inside the shell 14 through an inlet connection 15 positioned in the upper area of the shell 14 , in a longitudinal position ( along the hori zontal axis parallel to that of the tubes ) generally close to outlet connection 13 : through the external surface of the tubes the refrigerant fluid will give heat to the water flowing inside the tubes , and after having been cooled to the saturation condition, it will begin to condense and be collected in the form of liquid in the lower part of the shell , flooding a portion of the tubes of the tube bundle and in this way undergoing a progressive sub-cooling process exchanging heat with the flooded tubes , crossed inside from the colder water . The liquid refrigerant leaves the condenser 10 through an outlet connection 16 generally positioned in the lower part of the Shell and positioned on the water inlet side , precisely to facilitate the sub-cooling process .

[0062] The sub-cooled liquid is then expanded via an expansion organ 21 into the refrigerant inlet 22 of a a heat exchanger 20 , where it is used as a cooling agent for a medium entering the heat exchanger 20 through the inlet 23 , which medium is leav- ing the heat exchanger 20 after thermal interaction with the expanded refrigerant through the outlet 24 . The expanded refrigerant gas leaves the heat exchanger 20 through the refrigerant outlet 25 , is returned into the state of superheated vapor then compressed by a compressor 30 and fed back into the condenser 10 .

[0063] Figure 2 shows a cross section of a first example of a shell and tube condenser 100 with an essentially cylindrical shell 110 , taken along a vertical plane in which the cylinder axis of the essentially cylindrical shell 110 lies . The essentially cylindrical shell 110 comprises an inlet 111 for refrigerant fluid in a superheated vapor state on an upper side and an outlet 112 for completely condensed, slightly subcooled refrigerant fluid on a lower side .

[0064] The end faces of the essentially cylindrical shell 110 are formed by head plates 130 , 141 . The head plate 130 is provided with an inlet 131 for service fluid and an outlet 132 for service fluid, which lead to a tube sheet 140 , so that the service fluid can flow into tubes 121 from the inlet 131 and out of tubes 122 into the outlet 132 . On the opposite side of the tubes 121 , 122 , the service fluid leaves the tubes 121 , enters a volume between a second tube sheet 140 and the head plate 141 , from which it flows into the tubes 122 . The plurality of tubes 121 , 122 for the service fluid are sealingly connected to openings in the tube sheets 140 that are adapted to match the tubes . For the sake of clarity of representation, only two of the tubes 121 , 122 are shown in Figure 2 . Said tubes 121 , 122 are passing through the essentially cylindrical shell 110 extending essentially parallel to the cylinder axis of the essentially cylindrical shell 110 . The tubes 121 , 122 can also be profiled internally and externally to improve heat trans fer . In this example , tube 121 is representative for tubes that contribute to the first service fluid pass and tube 122 is representative for tubes that lead to the second service fluid pass through the shell and tube condenser 100 . Accordingly, service fluid enters the tube 121 through the inlet 131 for service fluid, flows towards the tube sheet 140 that is located on the side of the head plate 141 and enters the volume between the tube sheet 140 and the head plate 141 , before at least some of it enters the tube 122 , in which it flows back towards the opposite tube sheet located on the side of the head plate 130 and leaves the shell and tube condenser 100 through the outlet 132 for service fluid .

[0065] Accordingly, said tubes 121 , 122 are connected to each other in such a way that service liquid flowing through said tubes 121 , 122 is led N=2 times inside the tubes through the essentially cylindrical shell 110 .

[0066] The shell and tube type condenser 100 further comprises a longitudinal metal sheet 150 extending at an end of the essentially cylindrical shell from the tube sheet on the side of the head plate 130 , which longitudinal metal sheet 150 essentially divides the essentially cylindrical shell 110 into two passageways 113 , 114 so that refrigerant fluid makes two passes along tubes for the service fluid . On the other end of the essentially cylindrical shell 110 there is a pass-through region 115 , so that the refrigerant fluid can propagate into the next passageway below the passageway through which it j ust propagated, which is created using metal sheet 150 whose length is shorter than the length of the essentially cylindrical shell 110 . Accordingly, refrigerant fluid enters the cylindrical shell 110 through the inlet 111 , flows through the first pas- sageway 113 , falls in the pass through region 115 into the second passageway 114 and continues to the outlet 112 .

[0067] Furthermore , baf fle plates 160 are arranged in an orientation that is orthogonal to the cylinder axis inside the cylindrical shell 110 at several positions in the longitudinal direction of the shell and tube type condenser 100 . These baf fle plates 160 , one of which is shown in more detail in Figure 3a, can serve several purposes : they can make the assembly easier, support the tubes 120 , 121 , provide additional mechanical stability and counteract vibrations . In this example , the baf fle plates 160 are connected by a support rod 190 , which helps to align them precisely during assembly .

[0068] Figure 3a shows the baf fle plate 160 in an enlarged way before installation . It comprises a large number of holes 161 , some of which are to be filled with tubes 120 , 121 and some of which are to remain open to allow for passage of refrigerant fluid . It also comprises a slit 162 for the metal sheet .

[0069] From the shape of the slit 162 , further details of the shape of the longitudinal metal plate 150 can be derived . The slit features a topmost point 162a, inclined sections 162b, 162c and lowered seat sections 162d, 162e . These structures are provided to accommodate a longitudinal metal plate 150 with a crest line extending parallel to the longitudinal axis , inclined slopes connecting said crest line to the walls of the essentially cylindrical shell 110 , so that liquid that condenses in the upper passageway and drops onto this longitudinal metal plate 150 flows towards the walls of the essentially cylindrical shell 110 and propagates from there towards a free end of the longitudinal metal plate 150 , wherein a lowered seat is created in the contact region between the metal plate 150 and the walls of the essentially cylindrical shell 110.

[0070] The tube sheet 140 shown in Figure 3b shows similar structures as the baffle plate 160 shown in Figure 3a, but in the installed state no holes should remain open, as refrigerant fluid is not supposed to pass through the tube sheet 140. The metal plate needs to be connected in sealed manner in gap 162, such that no bypass from the upper passageway to the lower passageway is possible for the entering vapor refrigerant.

[0071] The variants of tube sheets 140", 140" ' that are shown in Figures 4a and 4b differ from the tube sheet 140 in the shape of the respective slit 162", 162" ' and illustrate different shapes of the longitudinal metal sheet 150 that may be used that do not possess lowered seat structures (c.f. Figure 4a) or lowered seat structures, inclined sections and a crest line (c.f. Figure 4b) , respectively.

[0072] Further variants of a possible configuration of a metal sheet 150' that are shown in Figures 7a, b and c may involve an additional sealing gasket 151 or 151', respectively. A sealing element that can be used as a sealing gasket 151, 151' can be a flexible element which is connected to the metal plate on one side and its opposite, free end is advantageously pushed against the inner surface of the shell.

[0073] Another interesting aspect which is illustrated in Figure 7a concerns the baffle plates 170,180 shown in said figure. As mentioned above, in general baffle plates such as the baffle plates 170,180 with baffle openings 173 and 183 can be used to influence mechanical properties of a shell and tube type condenser as well as the dynamics of the refrigerant fluid. Spe- cifically, the baffle plate 170 features a support nose 171 that pushes up and / or supports the metal sheet 150", thus increasing mechanical stability, reducing vibration problems and making the installation more easy.

[0074] The baffle plate 180, on the other hand, features a row of additional vent holes 181 to allow improved gas flow through the baffle plate 180. It should also be noticed that both the baffle plate 170 and the baffle plate 180 do not extend over the complete cross section of the refrigerant fluid passageway in which they are located. Instead, openings, e.g the openings 172 and 182, between the respective baffle plate 170,180 and the shell of the tube and shell type condenser, remain. By suitable adaption of the size and shape of these openings, it is also possible to influence the behavior of the refrigerant fluid flow in a desired way.

[0075] Returning to the shell and tube condenser 100, as best recognized in Figure 3a, the area of the cross section Al of the topmost, i.e. first, passageway 113 is significantly larger than the area of the cross section A2 of the next (and lowest) passageway 114, so that the cross section of the M+l passageways in the direction orthogonal to the cylinder axis of the essentially cylindrical shell 110 decreases from the topmost passageway 113 to the lowest passageway 114. More precisely, these cross sections meet the condition 0,3 < A2 / A1 < 0, 65. It should be stressed that the relevant cross section is the free cross section in the respective passageway 113,114, not the effective cross section defined by the openings in a baffle plate 160 which allow the passage of refrigerant fluid through the baffle plate. Figure 5 shows a cross section of a second example of a shell and tube condenser 200 with an essentially cylindrical shell 210 , taken along a vertical plane in which the cylinder axis of the essentially cylindrical shell 210 lies . The essentially cylindrical shell 210 comprises an inlet 211 for refrigerant fluid in a superheated vapor state on an upper side and an outlet 212 for completely condensed, slightly subcooled refrigerant fluid on a lower side . The end faces of the essentially cylindrical shell 210 are formed by head plates 230 , 241 . The head plate 230 is provided with an inlet 231 for service fluid and an outlet 232 for service fluid, which lead to a tube sheet , so that the service fluid can flow into tubes 221 from the inlet 231 and out of tubes 222 into the outlet 232 . On the opposite side of the tubes 221 , 222 , the service fluid leaves the tubes 221 , enters a volume between a second tube sheet 240 and the head plate 241 , from which it flows into the tubes 222 . The plurality of tubes 221 , 222 for the service fluid are sealingly connected to openings in the tube sheets 240 that are adapted to match the tubes . For the sake of clarity of representation, only two of the tubes 221 , 222 are shown in Figure 4 . Said tubes 221 , 222 are passing through the essentially cylindrical shell 210 extending essentially parallel to the cylinder axis of the essentially cylindrical shell 210 .

[0076] In this example , tube 221 is representative for tubes that contribute to the first service fluid pass and tube 222 is representative for tubes that lead to the second service fluid pass through the shell and tube condenser 200 . Accordingly, service fluid enters the tube 221 through the inlet 231 for service fluid, flows towards the tube sheet 240 and enters the volume between the tube sheet 240 and the head plate 241 before at least some of it enters the tube 222 , in which it flows back towards the opposite tube sheet located on the side of the head plate 230 and leaves the shell and tube condenser 200 through the outlet 232 for service fluid .

[0077] Accordingly, said tubes 221 , 222 are connected to each other in such a way that service liquid flowing through said tubes 221 , 222 is led N=2 times inside the tubes through the essentially cylindrical shell 210 .

[0078] The shell and tube type condenser 200 further comprises a longitudinal metal sheet 250 extending at an end of the essentially cylindrical shell from the tube sheet 240 on the side of the head plate 230 , which longitudinal metal sheet 250 essentially divides the essentially cylindrical shell 210 into two passageways 213 , 214 so that refrigerant fluid makes two passes along tubes for the service fluid . On the other end of the essentially cylindrical shell 210 there is a pass-through region 215 , so that the refrigerant fluid can propagate / fall into the next passageway below the passageway through which it j ust propagated, which is created using metal sheet 250 whose length is shorter than the length of the essentially cylindrical shell 210 . Accordingly, refrigerant fluid enters the cylindrical shell 210 through the inlet 211 , flows through the first passageway 213 , falls in the pass through region 215 into the second passageway 214 and continues to the outlet 212 .

[0079] The fundamental di f ference between the shell and tube type condenser 100 and the shell and tube type condenser 200 is that di f ferent types and di f ferent numbers of baf fle plates 260 , 270 , 280 are employed in the shell and tube type condenser 200 . Whereas the shape of the three baf fle plates 260 that are arranged in the first passageway 213 is rather similar to the shape of the upper part of the baf fle plate 160 , in the second passageway 214 two different types of baffle plates 270,280 that are illustrated in more detail in Figures 6a and 6b, respectively, are used in an alternating manner, forming five pairs .

[0080] More precisely, pairs of baffle plates 270,280 form a "disks and donuts" type baffle configuration to avoid excessive pressure drops, i.e. a baffle configuration wherein the first baffle plate 270 located in passageway 214 comprises a central void 271 and a neighboring second baffle plate 280 located in the same passageway 214 mainly covers the region of said void. Such baffle structure allows to guide the refrigerant in a meandering manner around the tubes.

[0081] Reference numerals

[0082] 1 system

[0083] 10 condenser

[0084] 11 inlet connection

[0085] 12 rear cap

[0086] 13 outlet connection

[0087] 14 shell

[0088] 15 inlet connection

[0089] 16 outlet connection

[0090] 20 heat exchanger

[0091] 21 expansion organ

[0092] 22 refrigerant inlet

[0093] 23 inlet

[0094] 24 outlet

[0095] 25 refrigerant outlet

[0096] 30 compressor

[0097] 100,200 condenser

[0098] 110,210 cylindrical shell

[0099] 111,211 inlet

[0100] 112,212 outlet

[0101] 113, 114,213,214 passageway

[0102] 115,215 pass-through region

[0103] 121, 122,221,222 tube

[0104] 130,230 head plate

[0105] 140, 140 ' , 140 ' ' , 240 tube sheet

[0106] 131,231 inlet

[0107] 132,232 outlet

[0108] 141,241 head plate

[0109] 142 tube sheet hole

[0110] 150, 150 ' , 250 metal sheet

[0111] 151, 151 ' sealing gasket

[0112] 160 baffle plate 161 baffle hole

[0113] 162, 162 ' , 162 ' ' slit

[0114] 162a topmost point

[0115] 162b, 162c inclined section 162d,162e seat section

[0116] 170 baffle plate

[0117] 171 support nose

[0118] 172 opening

[0119] 173 baffle hole 180 baffle plate

[0120] 181 vent hole

[0121] 182 opening

[0122] 183 baffle hole

[0123] 190,290 support rod 260,270,280 baffle plate

[0124] 271 void

[0125] Al, A2 cross section

Claims

Claims1. A shell and tube type condenser (100,200) for transferring energy from a refrigerant fluid to a service fluid comprising- an essentially cylindrical shell (110,210) comprising an inlet (111,211) for refrigerant fluid in a superheated vapor state on an upper side and an outlet (112,212) for completely condensed, slightly subcooled refrigerant fluid on a lower side;- a plurality of tubes (121,122,221,222) for the service fluid, said tubes (121,122,221,222) passing through the essentially cylindrical shell (110,210) extending essentially parallel to the cylinder axis of the essentially cylindrical shell (110,210) , said tubes (121,122,221,222) being connected to each other in such a way that service liquid flowing through said tubes (121,122,221,222) is led N times inside the tubes (121,122,221,222) through the essentially cylindrical shell (100,200) , wherein N is a natural number and N>1;- a number of M longitudinal metal sheets (150,250) extending from an end of the essentially cylindrical shell (110,210) and defining in the essentially cylindrical shell (110,210) M+l passageways (113,114,213,214) so that refrigerant fluid makes M+l passes along tubes (121,122, 221,222) for the service fluid, wherein M is a positive natural number; c h a r a c t e r i z e d i n that the area of the respective cross sections (A1,A2) of the M+l passageways (113,114,213,214) in the direction orthogonal to the cylinder axis of the essentially cylindrical shell (110,210) decreases from the topmost passageway (113,213) to the lowest passageway (114,214) .

2. The shell and tube condenser (100,200) of claim 1, wherein M=1 and 0,3 < A2 / A1 < 0,99, wherein Al is the cross section (Al) of the top passageway (113,213) and wherein A2 is the cross section (A2) of the bottom passageway (114,214) .

3. The shell and tube condenser (100,200) of claim 1, wherein M=1 and 0,3 < A2 / A1 < 0, 65, wherein Al is the cross section (Al) of the top passageway (113,213) and wherein A2 is the cross section (A2) of the bottom passageway (114,214) .

4. The shell and tube condenser (100,200) of one of claims 1 to 3 , wherein there are tubes (121,122,221,222) for the service fluid that are in the same passageway (113,114,213,214) that belong to different passes of the service fluid.

5. The shell and tube condenser (100,200) of one of claims 1 to 4 , wherein one or more baffle plates (160,170,180,260,270, 280) are arranged in at least one of the passageways (113,213, 114,214) .

6. The shell and tube condenser (100,200) of claim 5, wherein the number and / or location of the baffle plates (160,170,180,260,270,280) is different in at least two different passageways (113,213,114,214) .

7. The shell and tube condenser (100,200) of claim 5, wherein at least one of the baffle plates (160,170,180, 260,270,280) extends through more than one passageway (113, 114,213,214) .

8. The shell and tube condenser (100,200) of claim 7, wherein at least one of the baffle plates (160,170,180, 260,270,280) extends through all of the passageways (113, 114,213,214) .

9. The shell and tube condenser (100,200) of one of claims 5 to 8 , wherein a first baffle plate (270) located in a passageway (214) comprises a central void (271) and a neighboring second baffle plate (280) located in the same passageway (214) covers the region of said void (271) .

10. The shell and tube condenser (100,200) of one of claims 1 to 9, wherein at least one of the longitudinal metal plates(150.250) has a crest line extending parallel to the longitudinal axis and inclined slopes connecting said crest line to the walls of the essentially cylindrical shell, so that liquid that condenses on this longitudinal metal plate (150,250) flows towards the walls of the essentially cylindrical shell (110,210) and propagates from there towards a free end of this longitudinal metal plate(150.250) .

11. The shell and tube condenser (100,200) of one of claims 1 to 10, wherein a lowered seat is created in the contact region between the longitudinal metal plate (150,250) and the walls of a tube sheet ( 140 , 140 ' , 140 ' ' , 240 ) and / or the walls of the essentially cylindrical shell (110,210) .

12. The shell and tube condenser (100,200) of one of claims 1 to 11, wherein a lateral sealing gasket (151,151") is provided in the contact region between the longitudinal metal plate (150,250) and the walls of the essentially cylindrical shell (110,210) .

13. The shell and tube condenser (100,200) of one of claims 1 to 11, wherein in the M+l passageway the refrigerant fluid enters still in a two-phase status and exits in a subcooled one.

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