Patent Publication Number: US-11029094-B2

Title: Heat exchanger

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention generally relates to a heat exchanger adapted to be used in a vapor compression system. More specifically, this invention relates to a heat exchanger including at least one baffle arranged to restrict vapor flow, reduce local vapor velocity, isolate liquid leakage and/or trap liquid. 
     Background Information 
     Vapor compression refrigeration has been the most commonly used method for air-conditioning of large buildings or the like. Conventional vapor compression refrigeration systems are typically provided with an evaporator, which is a heat exchanger that allows the refrigerant to evaporate from liquid to vapor while absorbing heat from liquid to be cooled passing through the evaporator. One type of evaporator includes a tube bundle having a plurality of horizontally extending heat transfer tubes through which the liquid to be cooled is circulated, and the tube bundle is housed inside a cylindrical shell. There are several known methods for evaporating the refrigerant in this type of evaporator. In a flooded evaporator, the shell is filled with liquid refrigerant and the heat transfer tubes are immersed in a pool of the liquid refrigerant so that the liquid refrigerant boils and/or evaporates as vapor. In a falling film evaporator, liquid refrigerant is deposited onto exterior surfaces of the heat transfer tubes from above so that a layer or a thin film of the liquid refrigerant is formed along the exterior surfaces of the heat transfer tubes. Heat from walls of the heat transfer tubes is transferred via convection and/or conduction through the liquid film to the vapor-liquid interface where part of the liquid refrigerant evaporates, and thus, heat is removed from the water flowing inside of the heat transfer tubes. The liquid refrigerant that does not evaporate falls vertically from the heat transfer tube at an upper position toward the heat transfer tube at a lower position by force of gravity. There is also a hybrid falling film evaporator, in which the liquid refrigerant is deposited on the exterior surfaces of some of the heat transfer tubes in the tube bundle and the other heat transfer tubes in the tube bundle are immersed in the liquid refrigerant that has been collected at the bottom portion of the shell. 
     Although the flooded evaporators exhibit high heat transfer performance, the flooded evaporators require a considerable amount of refrigerant because the heat transfer tubes are immersed in a pool of the liquid refrigerant. With the recent development of new and high-cost refrigerant having a much lower global warming potential (such as R1234ze or R1234yf), it is desirable to reduce the refrigerant charge in the evaporator. The main advantage of the falling film evaporators is that the refrigerant charge can be reduced while ensuring good heat transfer performance. Therefore, the falling film evaporators have a significant potential to replace the flooded evaporators in large refrigeration systems. Regardless of the type of evaporator, e.g., flooded, falling film, or hybrid, refrigerant entering the evaporator is distributed to the tube bundle where evaporation of refrigerant occurs due to heating from liquid in the tube bundle. As refrigerant evaporates, refrigerant vapor is present. 
     SUMMARY OF THE INVENTION 
     It has been discovered that the vapor velocity can become quite high in some evaporators, which increases the likelihood of liquid carry over where liquid droplets enter the inlet of the compressor. This can cause a reduction in chiller efficiency and potentially increase the possibility of erosion of the impeller blade. If low pressure refrigerants such as R1233zd are used, these issues can occur more readily, although these issues can be present regardless of the refrigerant. 
     Therefore, one object of the present invention is to provide an evaporator that reduces or eliminates spray droplets being sent to the compressor. 
     One technology used for reducing or eliminating spray droplets is a mist eliminator. Though a mist eliminator can be effective, a mist eliminator may be relatively costly and bulky, taking up much room in the evaporator. In addition, a mist eliminator can cause high pressure drop, which may adversely affect system coefficient of performance (COP). Space requirements can lead to increased shell size and chiller size. 
     Therefore, another object of the present invention is to provide an evaporator with one or more baffles to redistribute the vapor flow inside of the evaporator. Such baffle(s) can force the flow to equalize and reduce local velocity. Lower velocity allows liquid droplets to settle out of the flow. In addition, such baffle(s) is/are less expensive and take up less space than a mist eliminator. 
     Another object is to provide a baffle used to even out the vapor flow near the top of the falling film bank by restricting upward vapor flow. 
     Another object is to provide a baffle used to reduce local vapor velocity between first and second tube passes and remove any liquid droplets by momentum. 
     Another object is to provide a baffle used to isolate any liquid leakage from the distributor from the bulk vapor flow. Such a baffle is also used to trap and drain any liquid from high speed vapor between the top row of falling film bank and bottom of the distributor. 
     Yet another object is to provide a baffle used to trap any liquid being dragged up the sides of the shell and direct it onto tubes for evaporation. 
     On or more of the foregoing objects may be obtained by a heat exchanger in accordance with any one or more of the following aspects. However, the aspects and combinations of aspects mentioned below are merely examples of possible aspects and combinations of aspect disclosed herein that may achieve one or more of the above objects. 
     A heat exchanger according to a first aspect of the present invention is adapted to be used in a vapor compression system. The heat exchanger includes a shell, a refrigerant distributor, tube bundle, and first baffle. The shell has a refrigerant inlet through which at least refrigerant with liquid refrigerant flows and a shell refrigerant vapor outlet. A longitudinal center axis of the shell extends substantially parallel to a horizontal plane. The refrigerant distributor fluidly communicates with the refrigerant inlet and is disposed within the shell. The refrigerant distributor has at least one liquid refrigerant distribution opening that distributes liquid refrigerant. The tube bundle is disposed inside of the shell below the refrigerant distributor. The first baffle extends downwardly from the refrigerant distributor at a top of the tube bundle to at least partially vertically overlap the top of the tube bundle. The first baffle is disposed laterally outwardly of the tube bundle toward a first lateral side of the shell. 
     In a second aspect, according to the heat exchanger of the first aspect, the first baffle is disposed laterally outwardly of the tube bundle toward the first lateral side of the shell by a distance not larger than three times a tube diameter of the heat transfer tubes. 
     In a third aspect, according to the heat exchanger of the first and/or second aspects, the first baffle is disposed laterally outwardly of the tube bundle toward the first lateral side of the shell by a distance about one times the tube diameter of the heat transfer tubes or less. 
     In a fourth aspect, according to the heat exchanger of any of the first to third aspects, the first baffle vertically overlaps the top of the tube bundle by a distance of one to three times the tube diameter. 
     In a fifth aspect, according to the heat exchanger of any of the first to fourth aspects, the first baffle includes a first baffle portion extending substantially perpendicular to the horizontal plane. 
     In a sixth aspect, according to the heat exchanger of any of the first to fifth aspects, the first baffle is vertically supported by at least one tube support that supports the tube bundle. 
     In a seventh aspect, according to the heat exchanger of the sixth aspect, the at least one tube support has a slot that receives and supports the baffle portion. 
     In an eighth aspect, according to the heat exchanger of the sixth aspect, the first baffle includes a first lateral portion extending from the first baffle portion in a direction substantially parallel to the horizontal plane, and the first lateral portion is vertically supported by the at least one tube support. 
     In a ninth aspect, according to the heat exchanger of the eighth aspect, the first lateral portion is vertically sandwiched between the at least one tube support and a bottom of the refrigerant distributor. 
     In a tenth aspect, according to the heat exchanger of the eighth aspect, the first lateral portion extends laterally inwardly from an upper end of the first baffle portion in a direction away from the first lateral side of the shell. 
     In an eleventh aspect, according to the heat exchanger of any of the first to tenth aspects, the first baffle is vertically supported without being fixedly attached to other parts of the heat exchanger. 
     In a twelfth aspect, according to the heat exchanger of any of the first to eleventh aspects, the first baffle is tack welded to be maintained in position. 
     In a thirteenth aspect, according to the heat exchanger of any of the first to twelfth aspects, the first baffle is constructed of non-permeable material. 
     In a fourteenth aspect, according to the heat exchanger of the thirteenth aspect, the first baffle is constructed of sheet metal. 
     In a fifteenth aspect, according to the heat exchanger of any of the first to fourteenth aspects, a second baffle extends downwardly from the refrigerant distributor at the top of the tube bundle to at least partially vertically overlap the top of the tube bundle. The second baffle is disposed laterally outwardly of the tube bundle toward a second lateral side of the shell. 
     These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG. 1  is a simplified, overall perspective view of a vapor compression system including a heat exchanger according to a first embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating a refrigeration circuit of the vapor compression system including the heat exchanger according to the first embodiment of the present invention; 
         FIG. 3  is a simplified perspective view of the heat exchanger according to the first embodiment of the present invention; 
         FIG. 4  is a simplified longitudinal cross sectional view of the heat exchanger illustrated in  FIGS. 1-3 , as taken along section line  4 - 4  in  FIG. 3 ; 
         FIG. 5  is a simplified transverse cross sectional view of the heat exchanger illustrated in  FIGS. 1-3 , as taken along section line  5 - 5  in  FIG. 3 ; 
         FIG. 6  is an enlarged partial perspective view of several tube supports and baffles of the heat exchanger illustrated in  FIGS. 1-5 ; 
         FIG. 7  is an exploded perspective view of some of the baffles of the heat exchanger illustrated in  FIG. 1-6 ; 
         FIG. 8  is an enlarged partial view of the arrangement of  FIG. 5 , but with vertical dimensional ranges for the upper baffle shown for the purpose of illustration; 
         FIG. 9  is a further enlarged view of the circled section A in  FIG. 8  with lateral dimensions of the upper baffle indicated thereon; 
         FIG. 10  is a partial view of the circled section A in  FIG. 8 , but with vertical and lateral dimensions of the vertical baffle relative to tube diameter indicated thereon; 
         FIG. 11  is an enlarged partial view of the arrangement of  FIG. 5 , but with vertical and lateral dimensional ranges for the middle baffle shown for the purpose of illustration; 
         FIG. 12  is an enlarged partial view of the arrangement of  FIG. 5 , but with vertical and lateral dimensional ranges for the lower baffle shown for the purpose of illustration; 
         FIG. 13  is an elevational view of one of the tube support plates illustrated in  FIG. 6 ; and 
         FIG. 14  is an enlarged partial transverse cross-sectional view of the structure illustrated in  FIG. 5  but with additional optional heat transfer tubes illustrated thereon in accordance with a modified embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT(S) 
     Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     Referring initially to  FIGS. 1 and 2 , a vapor compression system including a heat exchanger  1  according to a first embodiment will be explained. As seen in  FIG. 1 , the vapor compression system according to the first embodiment is a chiller that may be used in a heating, ventilation and air conditioning (HVAC) system for air-conditioning of large buildings and the like. The vapor compression system of the first embodiment is configured and arranged to remove heat from liquid to be cooled (e.g., water, ethylene glycol, calcium chloride brine, etc.) via a vapor-compression refrigeration cycle. 
     As shown in  FIGS. 1 and 2 , the vapor compression system includes the following four main components: an evaporator  1 , a compressor  2 , a condenser  3 , an expansion device  4 , and a control unit  5 . The control unit  5  includes an electronic controller operatively coupled to a drive mechanism of the compressor  2  and the expansion device  4  to control operation of the vapor compression system. In the illustrated embodiment, as shown in  FIGS. 4-5 , the evaporator  1  includes a plurality of baffles  40 ,  50 ,  60  and  70  in accordance with the present invention, as explained below in more detail. 
     The evaporator  1  is a heat exchanger that removes heat from the liquid to be cooled (in this example, water) passing through the evaporator  1  to lower the temperature of the water as a circulating refrigerant evaporates in the evaporator  1 . The refrigerant entering the evaporator  1  is typically in a two-phase gas/liquid state. The refrigerant at least includes liquid refrigerant. The liquid refrigerant evaporates as the vapor refrigerant in the evaporator  1  while absorbing heat from the water. 
     The low pressure, low temperature vapor refrigerant is discharged from the evaporator  1  and enters the compressor  2  by suction. In the compressor  2 , the vapor refrigerant is compressed to the higher pressure, higher temperature vapor. The compressor  2  may be any type of conventional compressor, for example, centrifugal compressor, scroll compressor, reciprocating compressor, screw compressor, etc. 
     Next, the high temperature, high pressure vapor refrigerant enters the condenser  3 , which is another heat exchanger that removes heat from the vapor refrigerant causing it to condense from a gas state to a liquid state. The condenser  3  may be an air-cooled type, a water-cooled type, or any suitable type of condenser. The heat raises the temperature of cooling water or air passing through the condenser  3 , and the heat is rejected to outside of the system as being carried by the cooling water or air. 
     The condensed liquid refrigerant then enters through the expansion device  4  where the refrigerant undergoes an abrupt reduction in pressure. The expansion device  4  may be as simple as an orifice plate or as complicated as an electronic modulating thermal expansion valve. Whether the expansion device  4  is connected to the control unit  5  will depend on whether a controllable expansion device  4  is utilized. The abrupt pressure reduction usually results in partial evaporation of the liquid refrigerant, and thus, the refrigerant entering the evaporator  1  is usually in a two-phase gas/liquid state. 
     Some examples of refrigerants used in the vapor compression system are hydrofluorocarbon (HFC) based refrigerants, for example, R410A, R407C, and R134a, hydrofluoro olefin (HFO), unsaturated HFC based refrigerant, for example, R1234ze, and R1234yf, and natural refrigerants, for example, R717 and R718. R1234ze, and R1234yf are mid density refrigerants with densities similar to R134a. R450A and R513A are also possible refrigerants. A so-called Low Pressure Refrigerant (LPR) 1233zd is also a suitable type of refrigerant. Low Pressure Refrigerant (LPR) 1233zd is sometimes referred to as Low Density Refrigerant (LDR) because R1233zd has a lower vapor density than the other refrigerants mentioned above. R1233zd has a density lower than R134a, R1234ze, and R1234yf, which are so-called mid density refrigerants. The density being discussed here is vapor density not liquid density because R1233zd has a slightly higher liquid density than R134A. While the embodiment(s) disclosed herein are useful with any type of refrigerant, the embodiment(s) disclosed herein are particularly useful when used with LPR such as 1233zd. This is because a LPR such as R1233zd has a relatively lower vapor density than the other options, which leads to higher velocity vapor flow. Higher velocity vapor flow in a conventional device used with LPR such as R1233zd can lead to liquid carryover as mentioned in the Summary above. While individual refrigerants are mentioned above, it will be apparent to those skilled in the art from this disclosure that a combination refrigerant utilizing any two or more of the above refrigerants may be used. For example, a combined refrigerant including only a portion as R1233zd could be utilized. 
     It will be apparent to those skilled in the art from this disclosure that conventional compressor, condenser and expansion device may be used respectively as the compressor  2 , the condenser  3  and the expansion device  4  in order to carry out the present invention. In other words, the compressor  2 , the condenser  3  and the expansion device  4  are conventional components that are well known in the art. Since the compressor  2 , the condenser  3  and the expansion device  4  are well known in the art, these structures will not be discussed or illustrated in detail herein. The vapor compression system may include a plurality of evaporators  1 , compressors  2  and/or condensers  3 . 
     Referring now to  FIGS. 3-13 , the detailed structure of the evaporator  1 , which is the heat exchanger according to the first embodiment, will be explained. The evaporator  1  basically includes a shell  10 , a refrigerant distributor  20 , and a heat transferring unit  30 . As mentioned above, in the illustrated embodiment, the evaporator  1  includes baffles  40 ,  50 ,  60  and  70 . The baffles  40 ,  50 ,  60  and  70  can be considered to be parts of the heat transferring unit  30  or separate parts of the heat exchanger  1 . In the illustrated embodiment, the heat transferring unit  30  is a tube bundle. Thus, the heat transferring unit  30  will also be referred to as the tube bundle  30  herein. Refrigerant enters the shell  10  and is supplied to the refrigerant distributor  20 . Then refrigerant distributor  20  preferably performs gas liquid separation and supplies the liquid refrigerant onto the tube bundle  30 , as explained in more detail below. Vapor refrigerant will exit the distributor  20  and flow into the interior of the shell  10 , as also explained in more detail below. The baffles  40 ,  50 ,  60  and  70  assist in controlling the flow of the refrigerant vapor within the shell  10 , as explained in more detail below. 
     As best understood from  FIGS. 3-5 , in the illustrated embodiment, the shell  10  has a generally cylindrical shape with a curved lateral sides LS and a longitudinal center axis C ( FIG. 5 ) extending substantially in the horizontal direction. The lateral sides LS are mirror images of each other and can be referred to as first and/or second lateral sides, and vice versa. Thus, the shell  10  extends generally parallel to a horizontal plane P. The shell  10  includes a connection head member  13  defining an inlet water chamber  13   a  and an outlet water chamber  13   b , and a return head member  14  defining a water chamber  14   a . The connection head member  13  and the return head member  14  are fixedly coupled to longitudinal ends of a cylindrical body of the shell  10 . The inlet water chamber  13   a  and the outlet water chamber  13   b  are partitioned by a water baffle  13   c . The connection head member  13  includes a water inlet pipe  15  through which water enters the shell  10  and a water outlet pipe  16  through which the water is discharged from the shell  10 . 
     As shown in  FIGS. 1-5 , the shell  10  further includes a refrigerant inlet  11   a  connected to a refrigerant inlet pipe  11   b  and a shell refrigerant vapor outlet  12   a  connected to a refrigerant outlet pipe  12   b . The refrigerant inlet pipe  11   b  is fluidly connected to the expansion device  4  to introduce the two-phase refrigerant into the shell  10 . The expansion device  4  may be directly coupled at the refrigerant inlet pipe  11   b . Thus, the shell  10  has a refrigerant inlet  11   a  that at least refrigerant with liquid refrigerant flows therethrough and a shell refrigerant vapor outlet  12   a , with the longitudinal center axis C of the shell  10  extending substantially parallel to the horizontal plane P. The liquid component in the two-phase refrigerant boils and/or evaporates in the evaporator  1  and goes through phase change from liquid to vapor as it absorbs heat from the water passing through the evaporator  1 . The vapor refrigerant is drawn from the refrigerant outlet pipe  12   b  to the compressor  2  by suction of the compressor  2 . The refrigerant that enters the refrigerant inlet  11   a  includes at least liquid refrigerant. Often the refrigerant entering the refrigerant inlet  11   a  is two-phase refrigerant. From the refrigerant inlet  11   a  the refrigerant flows into the refrigerant distributor  20 , which distributes the liquid refrigerant over the tube bundle  30 . 
     Referring now to  FIGS. 4-5 , the refrigerant distributor  20  is fluidly communicating with the refrigerant inlet  11   a  and is disposed within the shell  10 . The refrigerant distributor  20  is preferably configured and arranged to serve as both a gas-liquid separator and a liquid refrigerant distributor. The refrigerant distributor  20  extends longitudinally within the shell  10  generally parallel to the longitudinal center axis C of the shell  10 . As best shown in  FIGS. 4-5 , the refrigerant distributor  20  includes a bottom tray part  22  and a top lid part  24 . An inlet tube  26  is connected to the top lid part  24  and the refrigerant inlet  11   a  to fluidly communicate the refrigerant inlet  11   a  with the refrigerant distributor  20 . The bottom tray part  22  and the top lid part  24  are rigidly connected together to form a tubular shape. End parts  28  may be optionally attached to opposite longitudinal ends of the bottom tray part  22  and the top lid part  24 . The refrigerant distributor  20  is supported by parts of the tube bundle  30 , as explained in more detail below. 
     The precise structure of the refrigerant distributor  20  is not critical to the present invention. Therefore, it will be apparent to those skilled in the art from this disclosure that any suitable conventional refrigerant distributor  20  can be used. However, as seen in  FIG. 5  preferably the refrigerant distributor  20  includes at least one liquid refrigerant distribution opening  23  that distributes liquid refrigerant. In the illustrated embodiment, the bottom tray part  22  includes a plurality of liquid refrigerant distribution openings  23  that distribute liquid refrigerant onto the tube bundle  30 . In addition, in the illustrated embodiment, as seen in  FIG. 4  the refrigerant distributor  20  preferably includes at least one gas or vapor refrigerant distribution opening  25 . In the illustrated embodiment, the bottom tray part  22  includes a plurality of gas or vapor refrigerant distribution openings  25  that distribute vapor refrigerant into the shell  10 , which exits the shell  10  through the shell refrigerant vapor outlet  12   a  together with refrigerant that has evaporated due contact with the tube bundle  30 . The vapor refrigerant distribution openings  25  are disposed above a liquid level of refrigerant (not shown) in the refrigerant distributor  20 . Because the precise structure of the refrigerant distributor  20  is not critical to the present invention, the refrigerant distributor  20  will not be explained or illustrated in further detail herein. 
     Referring now to  FIGS. 4-7 , the heat transferring unit  30  (tube bundle) will now be explained in more detail. The tube bundle  30  is disposed inside the shell  10  below the refrigerant distributor  20  so that the liquid refrigerant discharged from the refrigerant distributor  20  is supplied onto the tube bundle  30 . The tube bundle  30  includes a plurality of heat transfer tubes  31  that extend generally parallel to the longitudinal center axis C of the shell  10  as best understood from  FIGS. 4-6 . The heat transfer tubes  31  are grouped together, as explained in more detail below. The heat transfer tubes  31  are made of materials having high thermal conductivity, such as metal. The heat transfer tubes  31  are preferably provided with interior and exterior grooves to further promote heat exchange between the refrigerant and the water flowing inside the heat transfer tubes  31 . Such heat transfer tubes including the interior and exterior grooves are well known in the art. For example, GEWA-B tubes by Wieland Copper Products, LLC may be used as the heat transfer tubes  31  of this embodiment. 
     As best understood from  FIGS. 4-6 , the heat transfer tubes  31  are supported by a plurality of vertically extending support plates  32  in a conventional manner. The support plates  32  may be fixedly coupled to the shell  10  or may merely rest within the shell  10 . The support plates  32  also support bottom tray part  22  in order to support the refrigerant distributor  20 . More specifically, the refrigerant distributor  20  via the bottom tray part  22  may be fixedly attached to the support plates  32  or merely rest on the support plates  32 . In addition, the support plates  32  support the baffles  40 ,  50 ,  60  and  70  as seen in  FIGS. 4-6 . In  FIG. 4 , the heat transfer tubes  31  are removed in order to better illustrate how the baffles  40 ,  50 ,  60  and  70  are supported by the support plates  32 . 
     In this embodiment, the tube bundle  30  is arranged to form a two-pass system, in which the heat transfer tubes  31  are divided into a supply line group disposed in a lower portion of the tube bundle  30 , and a return line group disposed in an upper portion of the tube bundle  30 . Thus, the plurality of heat transfer tubes  31  are grouped to form an upper group UG and a lower group LG with a pass lane PL disposed between the upper group UG and the lower group LG as seen in  FIG. 5 . As understood from  FIGS. 4-5 , inlet ends of the heat transfer tubes  31  in the supply line group are fluidly connected to the water inlet pipe  15  via the inlet water chamber  13   a  of the connection head member  13  so that water entering the evaporator  1  is distributed into the heat transfer tubes  31  in the supply line group. Outlet ends of the heat transfer tubes  31  in the supply line group and inlet ends of the heat transfer tubes  31  of the return line tubes are fluidly communicated with a water chamber  14   a  of the return head member  14 . 
     Therefore, the water flowing inside the heat transfer tubes  31  in the supply line group (lower group LG) is discharged into the water chamber  14   a , and redistributed into the heat transfer tubes  31  in the return line group (upper group UG). Outlet ends of the heat transfer tubes  31  in the return line group are fluidly communicated with the water outlet pipe  16  via the outlet water chamber  13   b  of the connection head member  13 . Thus, the water flowing inside the heat transfer tubes  31  in the return line group exits the evaporator  1  through the water outlet pipe  16 . In a typical two-pass evaporator, the temperature of the water entering at the water inlet pipe  15  may be about 54 degrees F. (about 12° C.), and the water is cooled to about 44 degrees F. (about 7° C.) when it exits from the water outlet pipe  16 . 
     As shown in  FIG. 5 , the tube bundle  30  of the illustrated embodiment is a hybrid tube bundle including a falling film region and a flooded region below a liquid level LL. The liquid level LL illustrated is a minimum liquid level. However, the liquid level could be higher, for example covering two more rows of the heat transfer tubes  31  in the supply line group (lower group LG). The heat transfer tubes  31  not submerged in liquid refrigerant form the tubes in the falling film region. The heat transfer tubes  31  in the falling film region are configured and arranged to perform falling film evaporation of the liquid refrigerant. More specifically, the heat transfer tubes  31  in the falling film region are arranged such that the liquid refrigerant discharged from the refrigerant distributor  20  forms a layer (or a film) along an exterior wall of each of the heat transfer tubes  31 , where the liquid refrigerant evaporates as vapor refrigerant while it absorbs heat from the water flowing inside the heat transfer tubes  31 . As shown in  FIG. 5 , the heat transfer tubes  31  in the falling film region are arranged in a plurality of vertical columns extending parallel to each other when seen in a direction parallel to the longitudinal center axis C of the shell  10  (as shown in  FIG. 5 ). Therefore, the refrigerant falls downwardly from one heat transfer tube to another by force of gravity in each of the columns of the heat transfer tubes  31 . The columns of the heat transfer tubes  31  are disposed with respect to the liquid refrigerant distribution opening  23  of the refrigerant distributor  20  so that the liquid refrigerant discharged from the liquid refrigerant distribution opening  23  is deposited onto an uppermost one of the heat transfer tubes  31  in each of the columns. 
     The liquid refrigerant that did not evaporate in the falling film region continues falling downwardly by force of gravity into the flooded region. The flooded region includes the plurality of the heat transfer tubes  31  disposed in a group below the falling film region at the bottom portion of the hub shell  11 . For example, the bottom, one, two, three or four rows of tubes  31  can be disposed as part of the flooded region depending on the amount of refrigerant charged in the system. Since the refrigerant entering the supply line group (lower group LG) of the heat transfer tubes  31  may be about 54 degrees F. (about 12° C.), liquid refrigerant in the flooded region may still boil and evaporate. 
     In this embodiment, a fluid conduit  8  may be fluidly connected to the flooded region within the shell  10 . A pump device (not shown) may be connected to the fluid conduit  8  to return the fluid from the bottom of the shell  10  to the compressor  2  or may be branched to the inlet pipe  11   b  to be supplied back to the refrigerant distributor  20 . The pump can be selectively operated when the liquid accumulated in the flooded region reaches a prescribed level to discharge the liquid therefrom to outside of the evaporator  1 . In the illustrated embodiment, the fluid conduit  8  is connected to a bottom most point of the flooded region. However, it will be apparent to those skilled in the art from this disclosure that the fluid conduit  8  can be fluidly connected to the flooded region at any location between the bottom most point of the flooded region and a location corresponding to the liquid level LL in the flooded region (e.g., between the bottom most point and the top tier of tubes  31  in the flooded region). Moreover, it will be apparent to those skilled in the art from this disclosure that the pump device (not shown) could instead be an ejector (not shown). In the case, where the pump device is replaced with an ejector, the ejector also receives compressed refrigerant from the compressor  2 . The ejector can then mix the compressed refrigerant from the compressor  2  with the liquid received from the flooded region so that a particular oil concentration can be supplied back to the compressor  2 . Pumps and ejectors such as those mentioned above are well known in the art and thus, will not be explained or illustrated in further detail herein. 
     Referring now to  FIGS. 4-13 , the baffles  40 ,  50 ,  60  and  70  will now be explained in more detail. In the illustrated embodiment, the evaporator includes a pair of upper baffles  40 , a pair of intermediate baffles  50 , a pair of lower baffles  60 , and a pair of upright baffles  70 . The pair of upper baffles  40  are disposed on opposite lateral sides of the refrigerant distributor  20  and the tube bundle  30  at the top of the tube bundle  30 . The pair of intermediate baffles  50  are disposed on opposite lateral sides of the tube bundle  30  below the upper baffles  40 . The pair of lower baffles  60  are disposed on opposite lateral sides of the tube bundle  30  below the intermediate baffles  50 . The pair of upright baffles  70  are disposed on opposite lateral sides of the tube bundle  30  below the refrigerant distributor  20  at inner ends of the upper baffles  40 . 
     The baffles  40 ,  50 ,  60  and  70  are supported by the tube support plates  32 . Specifically, in the illustrated embodiment, each tube support plate  32  has a pair of laterally spaced upper surfaces  34 , a pair of laterally spaced intermediate slots  35 , a pair of laterally spaced lower slots  36 , and a pair of upper slots  37 , as best seen in  FIG. 13 . The pair of laterally spaced upper surfaces  34  support the upper baffles  40 , the pair of laterally spaced intermediate slots  35  support the intermediate baffles  50 , the pair of laterally spaced lower slots  36  support the lower baffles  60 , and the pair of upper slots  37  support the upright baffles  70 , as best understood from  FIGS. 4-7 and 13 . 
     Referring now to  FIGS. 4-9 , the upper baffles  40  will now be explained in more detail. As mentioned above, in the illustrated embodiment, the heat exchanger  1  includes a pair of upper baffles  40 , with one of the upper baffles  40  disposed on each lateral side of the refrigerant distributor  20  and the tube bundle  30 . The upper baffles  40  are identical to each other. However, the upper baffles  40  are mounted to face each other in a mirror image arrangement relative to a vertical plane V passing through the central axis C, as best understood from  FIGS. 5-6 . Therefore, only one of the upper baffles  40  will be discussed and/or illustrated in detail herein. However, it will be apparent to those having ordinary skill in the art that the descriptions and illustrations of one of the upper baffles  40  also applies to the other upper baffle  40 . In addition, it will be apparent that either of the upper baffles  40  could be referred to as a first upper baffle  40  and either of the upper baffles  40  could be referred to a second upper baffle  40 , and vice versa. 
     The upper baffle  40  includes an inner portion  42 , an outer portion  44  extending laterally outwardly from the inner portion  42 , and a flange portion  46  extending downwardly from the outer edge of the outer portion  44 , as best seen in  FIG. 6 . In the illustrated embodiment, the inner portion  42 , the outer portion  44  and the flange portion  46  are each formed of a rigid sheet/plate material such as metal, which prevents liquid and gas refrigerant from passing therethrough unless holes  48  are formed therein. In addition, in the illustrated embodiment, the inner portion  42 , the outer portion  44  and the flange portion  46  are integrally formed together as a one-piece unitary member. However, it will be apparent to those skilled in the art from this disclosure that these plates  42 ,  44  and  46  may be constructed as separate members, which are attached to each other using any conventional technique such as welding. In either case, the inner portion  42  is preferably a solid, non-permeable portion that blocks liquid and gas refrigerant from passing therethrough. On the other hand, the outer portion  44  is preferably a permeable portion that allows liquid and gas refrigerant to pass therethrough. The flange portion  46  can be permeable or non-permeable. 
     Referring still to  FIGS. 4-9 , the inner portion  42  has an inner edge disposed under the refrigerant distributor  20  and above the adjacent upright baffle  70 . Thus, the baffle  40  is sandwiched between the refrigerant distributor  20  and upright baffle  70 . In addition, the inner portion  42  and the outer portion  44  are supported on the upper surfaces  34  of the tube support plates  32 . The flange portion  46  abuts a lateral side of the shell  10  at the outside of the tube support plates  32 . In the illustrated embodiment, the outer portions  44  are solid at the locations above the tube support plates  32 , as best understood from  FIGS. 6 and 9 . The inner portion  42  includes slots  49  ( FIG. 7 ) arranged to receive support flanges  39  of the tube support plates  32  ( FIG. 13 ). The support flanges  39  extend upwardly from the upper surfaces  34 . The support flanges  39  are arranged to laterally support the refrigerant distributor  20  therebetween. 
     The inner portion  42  and the outer portion  44  of the upper baffle  40  have a coplanar arrangement substantially parallel to the horizontal plane P. The inner portion  42  and the outer portion  44  of the upper baffle  40  are disposed upwardly from a bottom of the shell  10  between 40% and 70% of an overall height of the shell  10 . In the illustrated embodiment, the inner portion  42  and the outer portion  44  of the upper baffle  40  are disposed upwardly from a bottom of the shell  10  about 55% of an overall height of the shell  10 . The upper surfaces  34  of the tube support plates  32  are located slightly above the top of the tube bundle  30  at about the same height as the upper baffle  40  as seen in  FIG. 8 . 
     As best understood from  FIG. 7 , in the illustrated embodiment, the outer portion  44  is constructed of the same non-permeable material as the inner portion  42  but with the openings  48  formed therein to allow liquid and gas refrigerant to pass therethrough. Due to this structure, the outer portion  44  generally does not obstruct the flow of refrigerant therethrough. The openings  48  from a majority of the area of the outer portion  44  and preferably more than 75% of the area of the outer portion  44  to allow this free unobstructed flow of refrigerant. The openings  48  are relatively small in number and large in size to achieve this. More specifically, in the illustrated embodiment, each opening  48  has a lateral width that is equal to a lateral width of the outer portion  44 . In the illustrated embodiment, a single opening  48  is disposed between adjacent tube support plates  32  with the end openings  48  being cut longitudinally shorter, as best seen in  FIG. 7 . 
     Still referring to  FIGS. 4-9 , the outer portion  44  and the flange portion  46  may even be eliminated so that a permeable outer portion is formed by the empty space between the inner portion  42  and the shell  10 . However, in the illustrated embodiment, the outer portion  44  and the flange portion  46  are included and can assist in mounting and stability of the inner portion  42  of the baffle  40 . Regardless, the permeable portion (e.g. outer portion  44 ) preferably has a lateral width no more than 50% of a distance between the shell  10  and the adjacent upright baffle  70 . In addition, the permeable portion (e.g. outer portion  44 ) preferably has a lateral width no more than 50% of a distance between the shell  10  and the adjacent part of the refrigerant distributor  20 . In the illustrated embodiment, the adjacent upright baffle  70  is aligned with the adjacent lateral side of the refrigerant distributor  20  as seen in  FIG. 9 . 
     The function(s) of the upper baffles  40  will now be explained in more detail. Because the upper baffles  40  are located between the tube bundle  30  and the shell refrigerant vapor outlet  12   a  where refrigerant vapor is sucked out of the shell  10 , all of the evaporated vapor must flow through the upper baffles  40 . The upper baffles function to even out the vapor flow near the top of the falling film bank by restricting upward vapor flow. The solid area of the inner portion  42  does not allow refrigerant flow to slip off of tube bank, and forces high speed flow at top of tube bundle  30  to mix with lower speed flow in the rest of shell  10 . The open area at the outer portion  44  allows for vapor that has been evaporated off of the tube bundle  30  to mix with vapor above the refrigerant distributor  20 . Although the illustrated embodiment shows as all the same size openings, different sizes can be provided to direct vapor flow. 
     As is understood from the above descriptions, the upper baffles  40  are vertically disposed at a top of the tube bundle  30 , with the upper baffles  40  extending laterally outwardly from the tube bundle  30  toward a first lateral side LS of the shell  10 . In addition, preferably the upper baffles include upper non-permeable portions  42  laterally disposed adjacent to the tube bundle  30  and upper permeable portions  44  laterally disposed outwardly of the upper non-permeable portions  42 , with the upper permeable portions  44  being adjacent to the lateral sides LS of the shell  10 . In addition, preferably, the upper permeable portions  44  have lateral widths less than 50% of overall lateral widths of the upper baffles  40 . Therefore, the upper non-permeable portions have lateral widths larger than the lateral widths of the upper permeable portions, respectively. Also, as mentioned above, the upper baffles  40  are preferably formed of a non-permeable material with holes  48  formed therein to form the upper permeable portions  44 . Also, as mentioned above, the upper baffles  40  are preferably vertically disposed at a bottom of the refrigerant distributor  20 , and may be attached to a bottom of the refrigerant distributor  20 . In the illustrated embodiment, the upper baffles  40  are preferably vertically supported by at least one tube support  32  that supports the tube bundle  30 . The upper baffles are vertically disposed 40% to 70% of an overall height of the shell above a bottom edge of the shell. 
     As mentioned above, in the illustrated embodiment, a pair of upper baffles  40  are preferably present that are mirror images of each other. However, one upper baffle  40  can provide benefits, and thus, the heat exchanger  1  preferably includes at least one upper baffle  40 , and does not necessarily require both. 
     Referring now to  FIGS. 4-7 and 11 , the intermediate baffles  50  will now be explained in more detail. As mentioned above, in the illustrated embodiment, the heat exchanger  1  includes a pair of intermediate baffles  50 , with one of the intermediate baffles  50  disposed on each lateral side of the refrigerant distributor  20  and the tube bundle  30 . The intermediate baffles  50  are identical to each other. However, the intermediate baffles  50  are mounted to face each other in a mirror image arrangement relative to the vertical plane V passing through the central axis C, as best understood from  FIGS. 5-6 . Therefore, only one of the intermediate baffles  50  will be discussed and/or illustrated in detail herein. However, it will be apparent to those having ordinary skill in the art that the descriptions and illustrations of one of the intermediate baffles  50  also applies to the other intermediate baffle  50 . In addition, it will be apparent that either of the intermediate baffles  50  could be referred to as a first intermediate baffle  50  and either of the intermediate baffles  50  could be referred to a second intermediate baffle  50 , and vice versa. Even though the baffles  50  are referred to as intermediate baffles  50 , the baffles  50  could also be considered lower baffles as compared to the upper baffles  40 , and the baffles  50  could also be considered upper baffles as compared to the lower baffles  60 . In other words, the relative position of the intermediate baffles  50  depends on their locations relative to other parts. 
     The intermediate baffle  50  includes main portion  52 , an outer flange portion  54  extending upwardly from the outer edge of the main portion  52 , and reinforcing ribs  56  mounted to the main portion  52 . In the illustrated embodiment, the main portion  52  and the outer flange portion  54  are each formed of a rigid sheet/plate material such as metal, which prevents liquid and gas refrigerant from passing therethrough unless holes  58  are formed therein. In addition, in the illustrated embodiment, the main portion  52  and the outer flange portion  54  are integrally formed together as a one-piece unitary member. However, it will be apparent to those skilled in the art from this disclosure that these plates  52  and  54  may be constructed as separate members, which are attached to each other using any conventional technique such as welding. In either case, the main portion  52  is preferably a permeable portion that allows liquid and gas refrigerant to pass therethrough, except at the outer edge thereof. The outer flange portion  54  can be permeable or non-permeable. However, in the illustrated embodiment, the outer flange portion  54  is non-permeable for a more rigid outer portion than if constructed of permeable material. The reinforcing ribs  56  are preferably separate members constructed of the same material as the main portion  52  and are mounted to provide added strength at locations spaced from the tube support plates  32 . 
     Referring still to  FIGS. 4-7 and 11 , the main portion  52  has a plurality of longitudinally spaced slots  59  that receive the tube support plates  32  therein. In addition, the main portion  52  and the outer flange portion  54  are supported by the groove  35  of the tube support plates  32  at the outer end of the intermediate baffle  50 . The inner part of the main portion  52  is vertically supported by one of a plurality of reinforcing bars  33  (six shown) supporting the tube support plates  32 , as seen in  FIG. 11 .  FIG. 6  has the reinforcing bars  33  omitted for the sake of convenience. In the illustrated embodiment, the outer flange portion  54  is solid along with the outer edge of the main portion  52  as best understood from  FIGS. 6 and 11 . The main portion  52  includes a plurality of the holes  58  formed therein. In the illustrated embodiments, the holes  58  are large in number but small in size. In the illustrated embodiment, the holes  58  are smaller in diameter than a diameter of the heat transfer tubes  31 . However, the holes  58  could be elongated slots and/or the main portion  52  can have a louvered configuration. The outer flange  54  preferably includes a pair of vertical tabs useful when installing. 
     As best understood from  FIG. 11 , the main portion  52  is substantially parallel to the horizontal plane P. The main portion  52  is disposed upwardly from a bottom of the shell  10  between 20% and 40% of an overall height of the shell  10 . In the illustrated embodiment, the main portion  52  of the intermediate baffle  50  is disposed upwardly from a bottom of the shell  10  about 30% of an overall height of the shell  10 . However, the main portion  52  is preferably located above the pass lane PL. Therefore, the dimensions locations of 20% and 40% may not be to scale in  FIG. 11  (mainly the location of 20%). In addition, the intermediate baffle  50  has a lateral width not more than 20% of an overall width of the shell  10  measured at the intermediate baffle  50 . 
     The function(s) of the intermediate baffles  50  will now be explained in more detail. As mentioned above, the main portion  52  has the holes  58 . Alternatively, the main portion  52  can be a grated or louvered area. In any case, the main portion  58  evens out any high velocity spots and catches droplets and drains them back to liquid pool. Thus, the intermediate baffles  50  are used to reduce local vapor velocity between the first and second tube passes and remove any liquid droplets by momentum. The liquid droplets are stopped (physically) from rising by collision with grid, perforated plate, louvers or the like formed in the main portion  52 . While the intermediate baffle  50  can provide some benefit by itself, the intermediate baffle is particularly useful when used in combination with the upper baffle  40 . This is because the presence of the upper baffle  40  can lead to high velocity vapor flow and droplets being entrained in such vapor flow. A total opening area of the main portion  52  is preferably between 35%-65% of an overall area. In the illustrated embodiment, the total opening area is about 50%. In addition, the individual opening size with the openings  58  being used is preferably 2-10 millimeters in diameter. The hole size is of the holes  58  are smaller than the hole size of the openings  48  of the upper baffle. In addition, a total area of the holes  58  is preferably a smaller percentage than the total area of the upper baffle  40 . 
     As is understood from the above descriptions, the intermediate baffles  50  are vertically disposed below the upper baffles  40 , with the intermediate baffles  50  extending laterally inwardly from the lateral sides LS of the shell. Thus, the intermediate baffles  50  can also be considered lower baffles  50  because they are below the upper baffles  40 . Although the intermediate (lower) baffles  50  are below the upper baffles, the intermediate (lower) baffles  50  are preferably vertically disposed above the pass lane PL. In addition, the intermediate (lower) baffles  50  are preferably vertically disposed 20% to 40% of an overall height of the shell  10  above a bottom edge of the shell  10 , as best understood from  FIG. 11 . In addition, the intermediate (lower) baffles  50  extend laterally inwardly from the lateral sides LS of the shell by distances not more than 20% of a width of the shell  10  measured at the intermediate (lower) baffles  50  and perpendicularly relative to the longitudinal center axis C. Since, the intermediate baffles  50  can also be considered lower baffles  50 , the intermediate (lower) baffles  50  preferably include lower permeable portions  52 . In addition, the intermediate (lower) baffles  50  are formed of a non-permeable material with holes  58  formed therein to form the lower permeable portions  52 . As can be seen in  FIG. 7 , each lower permeable portion  52  forms a majority of each intermediate (lower) baffle  50 . In addition, the intermediate (lower) baffles  50  extend laterally inwardly toward the tube bundle  30  to free ends of the intermediate (lower) baffles  50  that are laterally spaced from the tube bundle  30 . 
     As mentioned above, in the illustrated embodiment, a pair of intermediate (lower) baffles  50  are preferably present that are mirror images of each other. However, one intermediate (lower) baffle  50  can provide benefits, and thus, the heat exchanger  1  preferably includes at least one intermediate (lower) baffle  50 , and does not necessarily require both. 
     Referring now to  FIGS. 4-7 and 12 , the lower baffles  60  will now be explained in more detail. As mentioned above, in the illustrated embodiment, the heat exchanger  1  includes a pair of lower baffles  60 , with one of the lower baffles  60  disposed on each lateral side of the refrigerant distributor  20  and the tube bundle  30 . The lower baffles  60  are identical to each other. However, the lower baffles  60  are mounted to face each other in a mirror image arrangement relative to the vertical plane V passing through the central axis C, as best understood from  FIGS. 5-6 . Therefore, only one of the lower baffles  60  will be discussed and/or illustrated in detail herein. However, it will be apparent to those having ordinary skill in the art that the descriptions and illustrations of one of the lower baffles  60  also applies to the other lower baffle  60 . In addition, it will be apparent that either of the lower baffles  60  could be referred to as a first lower baffle  60  and either of the lower baffles  60  could be referred to a second lower baffle  60 , and vice versa. The lower baffles  60  are disposed below the upper baffles  40  and the intermediate baffles  50 . Thus, the intermediate baffles  50  could also be considered upper baffles as compared to the lower baffles  60 . 
     The lower baffle  60  includes a main portion  62  and an inner flange portion  64  extending downwardly from the inner edge of the main portion  62 . In the illustrated embodiment, the main portion  62  and the inner flange portion  64  are each formed of a rigid sheet/plate material such as metal, which prevents liquid and gas refrigerant from passing therethrough unless holes are formed therein (none used in the illustrated embodiment). In addition, in the illustrated embodiment, the main portion  62  and the inner flange portion  64  are integrally formed together as a one-piece unitary member. However, it will be apparent to those skilled in the art from this disclosure that these plates  62  and  64  may be constructed as separate members, which are attached to each other using any conventional technique such as welding. In either case, the main portion  62  is preferably a non-permeable portion that prevents liquid and gas refrigerant from passing therethrough. The inner flange portion  64  can be permeable or non-permeable. However, in the illustrated embodiment, the inner flange portion  64  is non-permeable for a more rigid outer portion than if constructed of permeable material. 
     Referring still to  FIGS. 4-7 and 12 , the main portion  62  is a planar portion that extends substantially parallel to the horizontal plane P. On the other hand, the flange portion  64  extends substantially vertically. In addition, the main portion  62  and the inner flange portion  64  are supported by the grooves  36  of the tube support plates  32  (shown in  FIG. 13 ). Specifically, the grooves  36  are sized and shaped to receive the lower baffle  60  therein in a longitudinally slidable manner. The main portion  62  is disposed upwardly from a bottom of the shell  10  between 5% and 40% of an overall height of the shell  10 . In the illustrated embodiment, the main portion  62  of the lower baffle  60  is disposed upwardly from a bottom of the shell  10  about 15% of an overall height of the shell  10 . However, the main portion  62  is preferably located below the pass lane PL. Therefore, the dimensions locations of 5% and 40% may not be to scale in  FIG. 12  (mainly the location of 40%). In addition, the lower baffle  60  has a lateral width not more than 20% of an overall width of the shell  10  measured at the lower baffle  60 . The vertical positions and lateral widths are best understood from  FIG. 12 . 
     The function(s) of the lower baffles  60  will now be explained in more detail. The lower baffles  60  are used to deflect toward dry tubes any liquid stream coming from the flooded region on the shell side. Thus, the lower baffles are obstacles for liquid refrigerant to climb up the side of shell. Pooled liquid refrigerant in the flooded region tends to bubble and rise up the side of shell  10 . However, the lower baffles  60  are used to trap any liquid refrigerant being dragged up the sides of the shell  10  and direct it onto the refrigerant tubes  31  for evaporation. In the lower group LG of refrigerant tubes  31  some of the tubes  31  are disposed under the lower baffles  60  and adjacent to the lower baffles  60  at locations below the flange portion  64 . These tubes  31  perform a function of mist eliminator tubes. 
     As is understood from the above descriptions, the lower baffles  60  extend from the lateral sides LS of the shell  10 , with the lower baffles being vertically disposed 5% to 40% of an overall height of the shell  10  above a bottom edge of the shell  10 , and the lower baffles  60  extend laterally inwardly from the lateral sides LS of the shell  10  by a distance not more than 20% of a width of the shell measured at the lower baffles and perpendicularly relative to the longitudinal center axis C. In addition, the lower baffles  60  preferably include lateral (main) portions  62  substantially parallel to the horizontal plane P, and hook (flange) portions  64  extending downwardly from the lateral portions  62  at locations laterally spaced from the lateral sides LS of the shell  10 . As seen in  FIGS. 6-7 , the hook (flange) portions  64  are preferably laterally disposed at ends of the lateral (main) portions  62  furthest from the lateral sides LS of the shell  10 , and are substantially perpendicular to the horizontal plane P. 
     As mentioned above, the lower baffles  60  are each preferably constructed of non-permeable material such as sheet metal. In addition, the lower baffles  60  are preferably vertically disposed below the pass lane PL and above the liquid level LL of the liquid refrigerant. In the illustrated embodiment, the lower baffles  60  are preferably vertically disposed closer to the pass lane PL than to the liquid level LL. In addition, the lower group LG of heat transfer tubes  31  preferably has a lateral width larger than a lateral width of the upper group UG of heat transfer tubes  31 . Such an arrangement can aid in mist elimination near the lower baffles  60 . Moreover, at least one of the heat transfer tubes  31  is preferably vertically disposed below each of the lower baffles  60  and laterally outwardly of ends of the lower baffles  60  furthest from the lateral sides LS of the shell  10  so that each of the lower baffles  60  vertically overlaps the at least one heat transfer tube as viewed vertically. In addition, at least one of the heat transfer tubes  31  is laterally disposed within one tube diameter of each of the lower baffles as measured perpendicularly relative to the longitudinal center axis C. 
     As mentioned above, in the illustrated embodiment, a pair of lower baffles  60  are preferably present that are mirror images of each other. However, one lower baffle  60  can provide benefits, and thus, the heat exchanger  1  preferably includes at least one lower baffle  60 , and does not necessarily require both. 
     Referring now to  FIGS. 4-8 and 10 , the upright baffles  70  will now be explained in more detail. As mentioned above, in the illustrated embodiment, the heat exchanger  1  includes a pair of upright baffles  70 , with one of the upright baffles  70  disposed on each lateral side of the refrigerant distributor  20  and the tube bundle  30 . The upright baffles  70  are identical to each other. However, the upright baffles  70  are mounted to face each other in a mirror image arrangement relative to the vertical plane V passing through the central axis C, as best understood from  FIGS. 5-6 . Therefore, only one of the upright baffles  70  will be discussed and/or illustrated in detail herein. However, it will be apparent to those having ordinary skill in the art that the descriptions and illustrations of one of the upright baffles  70  also applies to the other upright baffle  70 . In addition, it will be apparent that either of the upright baffles  70  could be referred to as a first upright baffle  70  and either of the upright baffles  70  could be referred to a second upright baffle  70 , and vice versa. 
     The upright baffle  70  includes an upper portion  72  and a baffle portion  74  extending downwardly from the outer edge of the upper portion  72 . In the illustrated embodiment, the upper portion  72  and the baffle portion  74  are each formed of a rigid sheet/plate material such as metal, which prevents liquid and gas refrigerant from passing therethrough unless holes are formed therein (none used in the illustrated embodiment). In addition, in the illustrated embodiment, the upper portion  72  and the baffle portion  74  are integrally formed together as a one-piece unitary member. However, it will be apparent to those skilled in the art from this disclosure that these plates  72  and  74  may be constructed as separate members, which are attached to each other using any conventional technique such as welding. In either case, the upper portion  72  can be permeable or non-permeable. However, in the illustrated embodiment, the upper portion  72  is non-permeable for a more rigid outer portion than if constructed of permeable material. However, the baffle portion  74  is preferably a non-permeable portion that prevents liquid and gas refrigerant from passing therethrough. 
     Referring still to  FIGS. 4-8 and 10 , the upper portion  72  is a planar portion that extends substantially parallel to the horizontal plane P. On the other hand, the baffle portion  74  is a planar portion that extends substantially vertically perpendicular to the horizontal plane P. In addition, the upper portion  72  and the baffle portion  74  are supported by the grooves  37  of the tube support plates  32 . Specifically, the grooves  37  are sized and shaped to receive the upright baffle  70  therein in a longitudinally slidable manner or from vertically above. The grooves  37  are deeper than the upper portion  72  so the inner part of the upper baffles  40  can be mounted on top of the upper portions  72  yet still be flush with a central section  38  of the upper surface of the tube support plate  32  as shown in  FIG. 13 . 
     The function(s) of the upright baffles  70  will now be explained in more detail. The upright baffles  70  are used to isolate any liquid leakage from the refrigerant distributor  20  from the bulk vapor flow. Also, the upright baffles are used to trap and drain any liquid refrigerant from high speed vapor refrigerant between the top row of the falling film bank (top of tube bundle  30 ) and the bottom of the refrigerant distributor  20 . Some liquid refrigerant may hang on the bottom of refrigerant distributor  20  and can be drawn out to a side supported by vertical tube support plates  32 . However, the upright baffles can assist in preventing (or reducing) such flow from flowing outwardly of the tube bundle  30 , e.g., can guide liquid to flow over tube bundle  30 . The upright baffles  70  could be mounted to the bottom of refrigerant distributor  20  or to upper baffles  30  if present. Alternatively, the upright baffles  70  could be mounted to the tube support plates  32 . 
     As is understood from the above descriptions, the upright baffles  70  extend downwardly from the refrigerant distributor  20  at a top of the tube bundle  30  to at least partially vertically overlap the top of the tube bundle  30 , with the upright baffles being disposed laterally outwardly of the tube bundle  30  toward the lateral sides LS of the shell  10 . Preferably, the upright baffles  70  are disposed laterally outwardly of the tube bundle  30  toward the lateral sides LS of the shell  10  by a distance not larger than three times a tube diameter of the heat transfer tubes  31 , as best understood from  FIG. 10 . More preferably, the upright baffles  70  are disposed laterally outwardly of the tube bundle  30  toward the lateral sides LS of the shell  10  by a distance not larger than two times a tube diameter of the heat transfer tubes  31 . In the illustrated embodiment, the upright baffles  70  are disposed laterally outwardly of the tube bundle  30  toward the lateral sides LS of the shell  10  by a distance about one times the tube diameter of the heat transfer tubes or less. Preferably, the upright baffles  70  are disposed laterally outwardly of the tube bundle  30  toward the lateral sides LS of the shell  10  by a distance about one times a tube diameter of the heat transfer tubes  31  or less. 
     In addition, the upright baffles  70  preferably vertically overlap the top of the tube bundle  30  by a distance of one to three times the tube diameter, as best understood from  FIG. 10 . As mentioned above, each upright baffle  70  preferably includes a baffle portion  74  extending substantially perpendicular to the horizontal plane P. The upright baffles are vertically supported by at least one tube support  32  that supports the tube bundle  30 . The at least one tube support  32  has a slot that receives and supports the baffle portion  74 . Each upright baffle also preferably includes a lateral portion (upper portion)  72  extending from the baffle portion  74  in a direction substantially parallel to the horizontal plane P, and the lateral portion  72  is vertically supported by the at least one tube support  32 . The lateral (upper) portion  72  is preferably vertically sandwiched between the at least one tube support  32  and a bottom of the refrigerant distributor  20 . The lateral (upper) portions  72  extend laterally inwardly from upper ends of the baffle portions  74  in directions away from the lateral sides LS of the shell  10 . The upright baffles  70  can be fixedly attached to other parts of the heat exchanger  1 . For example, the upright baffles  70  can be tack welded to be maintained in position. In the illustrated embodiment, the upright baffles  70  are preferably constructed of non-permeable material such as sheet metal. 
     As mentioned above, in the illustrated embodiment, a pair of upright baffles  70  are preferably present that are mirror images of each other. However, one upright baffle  70  can provide benefits, and thus, the heat exchanger  1  preferably includes at least one upright baffle  70 , and does not necessarily require both. 
     Referring now to  FIG. 13 , one of the tube support plates  32  is illustrated in order clearly illustrate the pair of laterally spaced upper surfaces  34 , the pair of laterally spaced intermediate slots  35 , the pair of laterally spaced lower slots  36 , the pair of upper slots  37 , the central section  38  of the upper surface, and the support flanges  39 . The surface  38  is disposed between the slots  37 . These features were discussed above, and thus, will not be discussed in further detail herein. However, it is noted that in the illustrated embodiment, each of the support plates  32  is preferably cut from a thin sheet material such as sheet metal into the desired shape illustrated in  FIG. 13 . The upper baffles  40  are mounted by either moving the upper baffles  40  vertically downward onto the tube support plates  32  or from the lateral sides of the tube support plates  32 . The upright baffles  70  should be inserted vertically downward before the upper baffles  40 . The intermediate baffles  50  are inserted from the lateral sides of the tube support plates  32 . The lower baffles  60  are inserted longitudinally into the tube support plates  32 . Preferably, all of the baffles  40 ,  50 ,  60  and  70  are installed before installing the tube bundle in the shell  10 . 
     Each pair of baffles  40 ,  50 ,  60  and  70  has benefits alone, and each individual baffle has benefits alone. However, the baffles  40 ,  50 ,  60 , and  70  can be used in any combination. For example, one or both upper baffles  40  can be used without any other baffles  50 ,  60  or  70 . Likewise, one or both lower baffles  60  can be used without any other baffles  40 ,  50  or  70 . Likewise, one or both upright baffles  70  can be used without any other baffles  40 ,  50  or  60 . While one or both intermediate baffles  50  can be used without any other baffles  40 ,  60  or  70 , the intermediate baffles  50  are more beneficial when used with the upper baffles  40 . The upper baffles  40 , the lower baffles  60  and the upright baffles  70  are beneficial alone and when used with any of the other baffles. The baffles  40 ,  50 ,  60  and  70  may merely rest within the shell  10 , or maybe be tack welded at one or more locations. For example, tack welds at opposite ends of each baffle  40 ,  50 ,  60  and  70  can be used to secure the baffles  40 ,  50 ,  60  and  70 . 
     Modified Tube Arrangement 
     Referring now to  FIG. 14 , part of a modified evaporator  1 ′ is illustrated with a modified tube bundle  31 ′ in accordance with a modified embodiment. This modified embodiment is identical to the preceding embodiment, except for the modified tube bundle  31 ′. Therefore, it will be apparent to those of ordinary skill in the art from this disclosure that the descriptions and illustrations of the preceding embodiment also apply to this modified embodiment, except as explained and illustrated herein. In the modified tube bundle  30 ′ additional outer rows of tubes  31  are provided to form a modified upper group UG and a modified lower group LG. In the upper group UG, the additional rows are positioned so refrigerant directed from the upright baffles  70  falls thereon. In the lower group LG, only two additional tubes  31  are provided adjacent the lower baffles  60  to further aid in mist elimination. Due to the above arrangements, the upright baffles  70  are disposed laterally outwardly of the tube bundle  30  toward the lateral sides LS of the shell  10  by a distance less than one times a tube diameter of the heat transfer tubes  31 , and may be aligned with the heat transfer tubes  31  adjacent thereto. Modified tube support plates  32 ′ are needed, which have more holes to accommodate the additional tubes  31 . Otherwise, the tube support plates  32 ′ are identical to the tube support plates  32 . 
     General Interpretation of Terms 
     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. As used herein to describe the above embodiments, the following directional terms “upper”, “lower”, “above”, “downward”, “vertical”, “horizontal”, “below” and “transverse” as well as any other similar directional terms refer to those directions of an evaporator when a longitudinal center axis thereof is oriented substantially horizontally as shown in  FIGS. 4 and 5 . Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to an evaporator as used in the normal operating position. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.