WO2009089503A2

WO2009089503A2 - Vapor compression system

Info

Publication number: WO2009089503A2
Application number: PCT/US2009/030675
Authority: WO
Inventors: Paul De Larminat; Jeb Schreiber; Jay A. Kohler; Mustafa Kemal Yanik; William F. Mcquade; Justin Kauffman; Soren Bierre Poulsen; Lee Li Wang
Original assignee: Johnson Controls Technology Co
Current assignee: Johnson Controls Technology Co
Priority date: 2008-01-11
Filing date: 2009-01-09
Publication date: 2009-07-16
Anticipated expiration: 2010-07-11
Also published as: CN101903714B; CN101855502A; EP2232166B1; EP2450645B1; WO2009089488A1; WO2009089503A3; US20100326108A1; WO2009089514A2; CN102788451A; ATE554355T1; US20100276130A1; JP5616986B2; EP2232168A2; JP2013092365A; EP2482008B1; US20090178790A1; US20100319395A1; CN101903714A; WO2009089446A2; EP2482007A1

Abstract

A heat exchanger (128) is disclosed. The heat exchanger (128) for use in a vapor compression system includes a shell (76), a first partition (146), a first tube bundle (160), a hood (158) and a distributor (80). The first tube bundle (160) includes a plurality of tubes extending substantially horizontally in the shell (76). The first partition (146) divides the shell (76) into at least two separate compartments (150, 152), and the hood (80) is positioned in a first compartment (150) of the at least two compartments. The hood (80) covers the first tube bundle (160). The distributor (80) is configured and positioned to distribute fluid onto at least one tube of the first tube bundle (160).

Description

VAPOR COMPRESSION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from and the benefit of U.S. Provisional Application No. 61/020,533, entitled FALLING FILM EVAPORATOR SYSTEMS, filed January 1 1, 2008, which is hereby incorporated by reference.

BACKGROUND

[0002] The application relates generally to vapor compression systems in refrigeration, air conditioning and chilled liquid systems.

[0003] Conventional chilled liquid systems used in heating, ventilation and air conditioning systems include an evaporator to effect or implement a transfer of thermal energy between the refrigerant of the system and another fluid, generally a liquid to be cooled. One type of evaporator includes a shell with a plurality of tubes forming a tube bundle(s). The fluid to be cooled is circulated inside the tubes. The refrigerant is brought into contact with the outer or exterior surfaces of the tube bundle inside the shell, resulting in a transfer of thermal energy between the fluid to be cooled and the refrigerant. The heat thereby transferred to the refrigerant causes the refrigerant to undergo a phase change to a vapor, that is, boiling the refrigerant outside of the tubes. For example, refrigerant can be deposited onto the exterior surfaces of the tube bundle by spraying or other similar techniques in what is commonly referred to as a "falling film" evaporator. In a further example, the exterior surfaces of the tube bundle can be fully or partially immersed in liquid refrigerant in what is commonly referred to as a "flooded" evaporator. In yet another example, a portion of the tube bundle can have refrigerant deposited on the exterior surfaces and another portion of the tube bundle can be immersed in liquid refrigerant in what is commonly referred to as a "hybrid falling film" evaporator.

[0004] As a result of the transfer of thermal energy from the fluid being cooled, the refrigerant is heated and converted to a vapor state, which is then returned to a compressor where the vapor is compressed, to begin another refrigerant cycle. The cooled fluid can be circulated to a plurality of heat exchangers located throughout a building. Warmer air from the building is passed over the heat exchangers where the cooled fluid is warmed while cooling the air for the building. The fluid warmed by the building air is returned to the evaporator to repeat the process.

SUMMARY

(0005) The present invention relates to a heat exchanger for use in a vapor compression system including a shell, a first partition, a first tube bundle, a hood and a distributor. The first tube bundle includes a plurality of tubes extending substantially horizontally in the shell. The first partition divides the shell into at least two separate compartments, and the hood is positioned in a first compartment of the at least two compartments. The hood covers the first tube bundle. The distributor is configured and positioned to distribute fluid onto at least one tube of the first tube bundle.

[0006] The present invention also relates to a vapor compression system including a first compressor, a condenser, and an evaporator connected by a first refrigerant line. The evaporator includes a shell, a partition, a first tube bundle, a hood and a distributor. The first tube bundle includes a plurality of tubes extending substantially horizontally in the shell. The partition divides the shell into at least two separate compartments, and the hood is positioned in a first compartment of the at least two compartments. The hood covers the first tube bundle. The distributor is configured and positioned to distribute fluid onto at least one tube of the first tube bundle.

BRIEF DESCRIPTION OF THE FIGURES

[0007] FIG. 1 shows an exemplary embodiment for a heating, ventilation and air conditioning system.

[0008] FIG. 2 shows an isometric view of an exemplary vapor compression system.

[0009] FIGS. 3 and 4 schematically illustrate exemplary embodiments of the vapor compression system. [0010] FIG. 5 A shows an exploded, partial cutaway view of an exemplary evaporator.

[0011] FIG. 5B shows a top isometric view of the evaporator of FIG. 5A.

[0012] FIG. 5C shows a cross section of the evaporator taken along line 5-5 of FIG. 5B.

[0013] FIG. 6A shows a top isometric view of an exemplary evaporator.

[0014] FIGS. 6B and 6C show a cross section of the evaporator taken along line 6-6 of FIG. 6A.

[0015] FIGS. 7 and 8 show cross sections of exemplary embodiments of an evaporator.

[0016] FIGS. 9 and 10 show exemplary embodiments of an evaporator in combination with a schematic representation of a vapor compression system.

[0017] FIG. 11 shows a cross section of an exemplary embodiment of an evaporator.

[0018] FIG. 1 IA shows a cross section of an exemplary embodiment of an evaporator shell.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0019] FIG. 1 shows an exemplary environment for a heating, ventilation and air conditioning (HVAC) system 10 incorporating a chilled liquid system in a building 12 for a typical commercial setting. System 10 can include a vapor compression system 14 that can supply a chilled liquid which may be used to cool building 12. System 10 can include a boiler 16 to supply heated liquid that may be used to heat building 12, and an air distribution system which circulates air through building 12. The air distribution system can also include an air return duct 18, an air supply duct 20 and an air handler 22. Air handler 22 can include a heat exchanger that is connected to boiler 16 and vapor compression system 14 by conduits 24. The heat exchanger in air handler 22 may receive either heated liquid from boiler 16 or chilled liquid from vapor compression system 14, depending on the mode of operation of system 10. System 10 is shown with a separate air handler on each floor of building 12, but it is appreciated that the components may be shared between or among floors. [0020] FIGS. 2 and 3 show an exemplary vapor compression system 14 that can be used in an HVAC system, such as HVAC system 10. Vapor compression system 14 can circulate a refrigerant through a compressor 32 driven by a motor 50, a condenser 34, expansion device(s) 36, and a liquid chiller or evaporator 38. Vapor compression system 14 can also include a control panel 40 that can include an analog to digital (AIO) converter 42, a microprocessor 44, a non- volatile memory 46, and an interface board 48. Some examples of fluids that may be used as refrigerants in vapor compression system 14 are hydro fluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, hydrofluoro olefin (HFO), "natural" refrigerants like ammonia (NH3), R-717, carbon dioxide (CO₂), R-744, or hydrocarbon based refrigerants, water vapor or any other suitable type of refrigerant. In an exemplary embodiment, vapor compression system 14 may use one or more of each of VSDs 52, motors 50, compressors 32, condensers 34 and/or evaporators 38.

[0021] Motor 50 used with compressor 32 can be powered by a variable speed drive (VSD) 52 or can be powered directly from an alternating current (AC) or direct current (DC) power source. VSD 52, if used, receives AC power having a particular fixed line voltage and fixed line frequency from the AC power source and provides power having a variable voltage and frequency to motor 50. Motor 50 can include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source. For example, motor 50 can be a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor or any other suitable motor type. In an alternate exemplary embodiment, other drive mechanisms such as steam or gas turbines or engines and associated components can be used to drive compressor 32,

[0022] Compressor 32 compresses a refrigerant vapor and delivers the vapor to condenser 34 through a discharge line. Compressor 32 can be a centrifugal compressor, screw compressor, reciprocating compressor, rotary compressor, swing link compressor, scroll compressor, turbine compressor, or any other suitable compressor. The refrigerant vapor delivered by compressor 32 to condenser 34 transfers heat to a fluid, for example, water or air. The refrigerant vapor condenses to a refrigerant liquid in condenser 34 as a result of the heat transfer with the fluid. The liquid refrigerant from condenser 34 flows through expansion device 36 to evaporator 38. In the exemplary embodiment shown in FIG. 3, condenser 34 is water cooled and includes a tube bundle 54 connected to a cooling tower 56.

[0023] The liquid refrigerant delivered to evaporator 38 absorbs heat from another fluid, which may or may not be the same type of fluid used for condenser 34, and undergoes a phase change to a refrigerant vapor. In the exemplary embodiment shown in FIG. 3, evaporator 38 includes a tube bundle having a supply line 60S and a return line 6OR connected to a cooling load 62. A process fluid, for example, water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable liquid, enters evaporator 38 via return line 6OR and exits evaporator 38 via supply line 60S. Evaporator 38 chills the temperature of the process fluid in the tubes. The tube bundle in evaporator 38 can include a plurality of tubes and a plurality of tube bundles. The vapor refrigerant exits evaporator 38 and returns to compressor 32 by a suction line to complete the cycle.

[0024] FIG. 4, which is similar to FIG. 3, shows the refrigerant circuit with an intermediate circuit 64 that may be incorporated between condenser 34 and expansion device 36 to provide increased cooling capacity, efficiency and performance. Intermediate circuit 64 has an inlet line 68 that can be either connected directly to or can be in fluid communication with condenser 34. As shown, inlet line 68 includes an expansion device 66 positioned upstream of an intermediate vessel 70. Intermediate vessel 70 can be a flash tank, also referred to as a flash intercooler, in an exemplary embodiment. In an alternate exemplary embodiment, intermediate vessel 70 can be configured as a heat exchanger or a "surface economizer". In the flash intercooler arrangement, a first expansion device 66 operates to lower the pressure of the liquid received from condenser 34. During the expansion process in a flash intercooler, a portion of the liquid is evaporated. Intermediate vessel 70 may be used to separate the evaporated vapor from the liquid received from the condenser. The evaporated liquid may be drawn by compressor 32 to a port at a pressure intermediate between suction and discharge or at an intermediate stage of compression, through a line 74. The liquid that is not evaporated is cooled by the expansion process, and collects at the bottom of intermediate vessel 70, where the liquid is recovered to flow to the evaporator 38, through a line 72 comprising a second expansion device 36. [0025] In the "surface intercooler" arrangement, the implementation is slightly different, as known to those skilled in the art. Intermediate circuit 64 can operate in a similar matter to that described above, except that instead of receiving the entire amount of refrigerant from condenser 34, as shown in FIG. 4, intermediate circuit 64 receives only a portion of the refrigerant from condenser 34 and the remaining refrigerant proceeds directly to expansion device 36.

[0026] FIGS. 5 A through 5C show an exemplary embodiment of an evaporator configured as a "hybrid falling film" evaporator. As shown in FIGS. 5A through 5C, an evaporator 138 includes a substantially cylindrical shell 76 with a plurality of tubes forming a tube bundle 78 extending substantially horizontally along the length of shell 76. At least one support 1 16 may be positioned inside shell 76 to support the plurality of tubes in tube bundle 78. A suitable fluid, such as water, ethylene, ethylene glycol, or calcium chloride brine flows through the tubes of tube bundle 78. A distributor 80 positioned above tube bundle 78 distributes, deposits or applies refrigerant 110 from a plurality of positions onto the tubes in tube bundle 78. In one exemplary embodiment, the refrigerant deposited by distributor 80 can be entirely liquid refrigerant, although in another exemplary embodiment, the refrigerant deposited by distributor 80 can include both liquid refrigerant and vapor refrigerant.

[0027] Liquid refrigerant that flows around the tubes of tube bundle 78 without changing state collects in the lower portion of shell 76. The collected liquid refrigerant can form a pool or reservoir of liquid refrigerant 82. The deposition positions from distributor 80 can include any combination of longitudinal or lateral positions with respect to tube bundle 78. In another exemplary embodiment, deposition positions from distributor 80 are not limited to ones that deposit onto the upper tubes of tube bundle 78. Distributor 80 may include a plurality of nozzles supplied by a dispersion source of the refrigerant. In an exemplary embodiment, the dispersion source is a tube connecting a source of refrigerant, such as condenser 34. Nozzles include spraying nozzles, but also include machined openings that can guide or direct refrigerant onto the surfaces of the tubes. The nozzles may apply refrigerant in a predetermined pattern, such as a jet pattern, so that the upper row of tubes of tube bundle 78 are covered. The tubes of tube bundle 78 can be arranged to promote the flow of refrigerant in the form of a film around the tube surfaces, the liquid refrigerant coalescing to form droplets or in some instances, a curtain or sheet of liquid refrigerant at the bottom of the tube surfaces. The resulting sheeting promotes wetting of the tube surfaces which enhances the heat transfer efficiency between the fluid flowing inside the tubes of tube bundle 78 and the refrigerant flowing around the surfaces of the tubes of tube bundle 78.

[0028] In the pool of liquid refrigerant 82, a tube bundle 140 can be immersed or at least partially immersed, to provide additional thermal energy transfer between the refrigerant and the process fluid to evaporate the pool of liquid refrigerant 82. In an exemplary embodiment, tube bundle 78 can be positioned at least partially above (that is, at least partially overlying) tube bundle 140. In one exemplary embodiment, evaporator 138 incorporates a two pass system, in which the process fluid that is to be cooled first flows inside the tubes of tube bundle 140 and then is directed to flow inside the tubes of tube bundle 78 in the opposite direction to the flow in tube bundle 140. In the second pass of the two pass system, the temperature of the fluid flowing in tube bundle 78 is reduced, thus requiring a lesser amount of heat transfer with the refrigerant flowing over the surfaces of tube bundle 78 to obtain a desired temperature of the process fluid.

[0029J It is to be understood that although a two pass system is described in which the first pass is associated with tube bundle 140 and the second pass is associated with tube bundle 78, other arrangements are contemplated. For example, evaporator 138 can incorporate a one pass system where the process fluid flows through both tube bundle 140 and tube bundle 78 in the same direction. Alternatively, evaporator 138 can incorporate a three pass system in which two passes are associated with tube bundle 140 and the remaining pass associated with tube bundle 78, or in which one pass is associated with tube bundle 140 and the remaining two passes are associated with tube bundle 78. Further, evaporator 138 can incorporate an alternate two pass system in which one pass is associated with both tube bundle 78 and tube bundle 140, and the second pass is associated with both tube bundle 78 and tube bundle 140. In one exemplary embodiment, tube bundle 78 is positioned at least partially above tube bundle 140, with a gap separating tube bundle 78 from tube bundle 140. In a further exemplary embodiment, hood 86 overlies tube bundle 78, with hood 86 extending toward and terminating near the gap. In summary, any number of passes in which each pass can be associated with one or both of tube bundle 78 and tube bundle 140 is contemplated. [0030] An enclosure or hood 86 is positioned over tube bundle 78 to substantially prevent cross flow, that is, a lateral flow of vapor refrigerant or liquid and vapor refrigerant 106 between the tubes of tube bundle 78. Hood 86 is positioned over and laterally borders tubes of tube bundle 78. Hood 86 includes an upper end 88 positioned near the upper portion of shell 76. Distributor 80 can be positioned between hood 86 and tube bundle 78. In yet a further exemplary embodiment, distributor 80 may be positioned near, but exterior of, hood 86, so that distributor 80 is not positioned between hood 86 and tube bundle 78. However, even though distributor 80 is not positioned between hood 86 and tube bundle 78, the nozzles of distributor 80 are still configured to direct or apply refrigerant onto surfaces of the tubes. Upper end 88 of hood 86 is configured to substantially prevent the flow of applied refrigerant 1 10 and partially evaporated refrigerant, that is, liquid and/or vapor refrigerant 106 from flowing directly to outlet 104. Instead, applied refrigerant 1 10 and refrigerant 106 are constrained by hood 86, and, more specifically, are forced to travel downward between walls 92 before the refrigerant can exit through an open end 94 in the hood 86. Flow of vapor refrigerant 96 around hood 86 also includes evaporated refrigerant flowing away from the pool of liquid refrigerant 82.

[0031] It is to be understood that at least the above-identified, relative terms are non-limiting as to other exemplary embodiments in the disclosure. For example, hood 86 may be rotated with respect to the other evaporator components previously discussed, that is, hood 86, including walls 92, is not limited to a vertical orientation. Upon sufficient rotation of hood 86 about an axis substantially parallel to the tubes of tube bundle 78, hood 86 may no longer be considered "positioned over" nor to "laterally border" tubes of tube bundle 78. Similarly, "upper" end 88 of hood 86 may no longer be near "an upper portion" of shell 76, and other exemplary embodiments are not limited to such an arrangement between the hood and the shell. In an exemplary embodiment, hood 86 terminates after covering tube bundle 78, although in another exemplary embodiment, hood 86 further extends after covering tube bundle 78.

[0032] After hood 86 forces refrigerant 106 downward between walls 92 and through open end 94, the vapor refrigerant undergoes an abrupt change in direction before traveling in the space between shell 76 and walls 92 from the lower portion of shell 76 to the upper portion of shell 76. Combined with the effect of gravity, the abrupt directional change in flow results in a proportion of any entrained droplets of refrigerant colliding with either liquid refrigerant 82 or shell 76, thereby removing those droplets from the flow of vapor refrigerant 96. Also, refrigerant mist traveling along the length of hood 86 between walls 92 is coalesced into larger drops that are more easily separated by gravity, or maintained sufficiently near or in contact with tube bundle 78, to permit evaporation of the refrigerant mist by heat transfer with the tube bundle. As a result of the increased drop size, the efficiency of liquid separation by gravity is improved, permitting an increased upward velocity of vapor refrigerant 96 flowing through the evaporator in the space between walls 92 and shell 76. Vapor refrigerant 96, whether flowing from open end 94 or from the pool of liquid refrigerant 82, flows over a pair of extensions 98 protruding from walls 92 near upper end 88 and into a channel 100. Vapor refrigerant 96 enters into channel 100 through slots 102, which is the space between the ends of extensions 98 and shell 76, before exiting evaporator 138 at an outlet 104. In another exemplary embodiment, vapor refrigerant 96 can enter into channel 100 through openings or apertures formed in extensions 98, instead of slots 102. In yet another exemplary embodiment, slots 102 can be formed by the space between hood 86 and shell 76, that is, hood 86 does not include extensions 98.

[0033] Stated another way, once refrigerant 106 exits from hood 86, vapor refrigerant 96 then flows from the lower portion of shell 76 to the upper portion of shell 76 along the prescribed passageway. In an exemplary embodiment, the passageways can be substantially symmetric between the surfaces of hood 86 and shell 76 prior to reaching outlet 104. In an exemplary embodiment, baffles, such as extensions 98 are provided near the evaporator outlet to prevent a direct path of vapor refrigerant 96 to the compressor inlet.

[0034] In one exemplary embodiment, hood 86 includes opposed substantially parallel walls 92. In another exemplary embodiment, walls 92 can extend substantially vertically and terminate at open end 94, that is located substantially opposite upper end 88. Upper end 88 and walls 92 are closely positioned near the tubes of tube bundle 78, with walls 92 extending toward the lower portion of shell 76 so as to substantially laterally border the tubes of tube bundle 78. In an exemplary embodiment, walls 92 may be spaced between about 0.02 inch (0.5 mm) and about 0.8 inch (20 mm) from the tubes in tube bundle 78. In a further exemplary embodiment, walls 92 may be spaced between about 0.1 inch (3 mm) and about 0.2 inch (5 mm) from the tubes in tube bundle 78. However, spacing between upper end 88 and the tubes of tube bundle 78 may be significantly greater than 0.2 inch (5 mm), in order to provide sufficient spacing to position distributor 80 between the tubes and the upper end of the hood. In an exemplary embodiment in which walls 92 of hood 86 are substantially parallel and shell 76 is cylindrical, walls 92 may also be symmetric about a central vertical plane of symmetry of the shell bisecting the space separating walls 92. In other exemplary embodiments, walls 92 need not extend vertically past the lower tubes of tube bundle 78, nor do walls 92 need to be planar, as walls 92 may be curved or have other non-planar shapes. Regardless of the specific construction, hood 86 is configured to channel refrigerant 106 within the confines of walls 92 through open end 94 of hood 86.

[0035] FIGS. 6A through 6C show an exemplary embodiment of an evaporator configured as a "falling film" evaporator 128. As shown in FIGS. 6 A through 6C, evaporator 128 is similar to evaporator 138 shown in FIGS. 5A through 5C, except that evaporator 128 does not include tube bundle 140 in the pool of refrigerant 82 that collects in the lower portion of the shell. In an exemplary embodiment, hood 86 terminates after covering tube bundle 78, although in another exemplary embodiment, hood 86 further extends toward pool of refrigerant 82 after covering tube bundle 78. In yet a further exemplary embodiment, hood 86 terminates so that the hood does not totally cover the tube bundle, that is, substantially covers the tube bundle.

[0036] As shown in FIGS. 6B and 6C, a pump 84 can be used to recirculate the pool of liquid refrigerant 82 from the lower portion of the shell 76 via line 1 14 to distributor 80. As further shown in FlG. 6B, line 1 14 can include a regulating device 112 that can be in fluid communication with a condenser (not shown). In another exemplary embodiment, an ejector (not shown) can be employed to draw liquid refrigerant 82 from the lower portion of shell 76 using the pressurized refrigerant from condenser 34, which operates by virtue of the Bernoulli effect. The ejector combines the functions of a regulating device 112 and a pump 84.

[0037] In an exemplary embodiment, one arrangement of tubes or tube bundles may be defined by a plurality of uniformly spaced tubes that are aligned vertically and horizontally, forming an outline that can be substantially rectangular. However, a stacking arrangement of tube bundles can be used where the tubes are neither vertically or horizontally aligned, as well as arrangements that are not uniformly spaced.

[0038] In another exemplary embodiment, different tube bundle constructions are contemplated. For example, finned tubes (not shown) can be used in a tube bundle, such as along the uppermost horizontal row or uppermost portion of the tube bundle. Besides the possibility of using finned tubes, tubes developed for more efficient operation for pool boiling applications, such as in "flooded" evaporators, may also be employed. Additionally, or in combination with the finned tubes, porous coatings can also be applied to the outer surface of the tubes of the tube bundles.

[0039] In a further exemplary embodiment, the cross-sectional profile of the evaporator shell may be non-circular.

[0040] In an exemplary embodiment, a portion of the hood may partially extend into the shell outlet.

[0041] In addition, it is possible to incorporate the expansion functionality of the expansion devices of system 14 into distributor 80. In one exemplary embodiment, two expansion devices may be employed. One expansion device is exhibited in the spraying nozzles of distributor 80. The other expansion device, for example, expansion device 36, can provide a preliminary partial expansion of refrigerant, before that provided by the spraying nozzles positioned inside the evaporator. In an exemplary embodiment, the other expansion device, that is, the non-spraying nozzle expansion device, can be controlled by the level of liquid refrigerant 82 in the evaporator to account for variations in operating conditions, such as evaporating and condensing pressures, as well as partial cooling loads. In an alternative exemplary embodiment, expansion device can be controlled by the level of liquid refrigerant in the condenser, or in a further exemplary embodiment, a "flash economizer" vessel. In one exemplary embodiment, the majority of the expansion can occur in the nozzles, providing a greater pressure difference, while simultaneously permitting the nozzles to be of reduced size, therefore reducing the size and cost of the nozzles. [0042] FIG. 7 shows an exemplary embodiment of an evaporator 144, Evaporator 144 includes a first partition 146 that divides shell 76 into separate compartments 150 and 152. First partition 146 can divide shell 76 into two substantially equally sized compartments, but may divide shell 76 into unevenly sized compartments in other exemplary embodiments. In addition, first partition 146 can extend in a substantially vertical direction. However, in other exemplary embodiments, first partition 146 may be oriented or extend in a non-vertical direction, such as diagonally in shell 76. In a further exemplary embodiment, first partition 146 extends into outlet 104 when only a single outlet is used, such as is shown in FIG. 7. Evaporator 144 may further include a second partition 148 having a first segment 154 connected to one end of a second segment 156, with the other end of second segment 156 extending toward and connecting with shell 76. Collectively, shell 76, first segment 154 and second segment 156 define a hood 158 that covers a tube bundle 160 within each of compartments 150 and 152. A gap 162 separates first partition 146 from second partition 148, in which first partition 146 and first segment 154 of second partition 148 may be positioned substantially parallel to each other. However, second segment 156 and second partition 148 may be nonparallel with first partition 146. The portion of gap 162 separating first partition 146 from second segment 156 of second partition 148 and extending toward the shell is shown in FIG. 7 as diverging respect to the remaining portion of gap 162. Gap 162 may be configured to guide refrigerant 96 toward outlet 104 in each of compartments 150 and 152. In one exemplary embodiment, a filter (not shown), commonly referred to as a "mist eliminator" or "vapor/liquid separator" may be positioned in the portion of gap 162 near outlet 104. In a further exemplary embodiment, first segment 154 terminates near tube bundle 160, that is, after covering tube bundle 160. In yet a further exemplary embodiment, first segment 154 further extends toward the open space separating tube bundle 160 from a tube bundle 164 and a lower portion of the compartment, the first segment terminating in the open space.

[0043] FIG. 8 shows an exemplary embodiment of an evaporator 168 incorporated in a schematic representation of a vapor compression system 170. Evaporator 168 may include a first partition 172 that divides shell 76 into separate compartments 150 and 152. First partition 172 can divide shell 76 into two substantially equally sized compartments, but may divide shell 76 into unevenly sized compartments in other exemplary embodiments. In addition, first partition 172 can extend in a substantially vertical direction. Evaporator 168 may further include a second partition 174 having a first segment 176 connected to one end of a second segment 178, with the other end of second segment 178 connected to shell 76. Collectively, shell 76, first partition 172 and second partition 174 define a hood 180 that covers a tube bundle 78 contained within each of compartments 150 and 152. In an exemplary embodiment, second partition 174 includes an extension 184 positioned near outlet 104. In a further exemplary embodiment, compartment 152 may not contain hood 180 or corresponding tube bundle 78, containing only a tube bundle 182, although in a yet further exemplary embodiment, compartment 152 may contain hood 180 and tube bundle 78, but not tube bundle 182.

[0044] A gap 186 collectively defined between second partition 174 and shell 76 may be configured to guide refrigerant 96 toward outlet 104. In one exemplary embodiment, a filter (not shown), commonly referred to as a "mist eliminator" or "vapor/liquid separator" may be positioned in the portion of gap 186 near outlet 104. In a further exemplary embodiment, first segment 176 can terminate after covering tube bundle 78, In yet a further exemplary embodiment, first segment 176 further extends toward the open space separating tube bundle 78 from a tube bundle 182 and a lower portion of the compartment, with the first segment terminating in the open space. In another exemplary embodiment, compartment 152 may not include tube bundle 182, and first segment 176 may further extend toward pooled liquid refrigerant 82.

[0045] FIG. 8 further shows a first refrigerant line 190 that connects outlet 104 of compartment 150 of evaporator 168 with a first compressor 192, a condenser 194 and a metering device 196, such as an expansion valve, before returning to distributor 80 of compartment 150. Distributor 80 deposits or applies refrigerant onto the surfaces of tube bundle 78, which tube bundle is covered by hood 180, Refrigerant 96 that flows around the end of hood 180, which may also include partially evaporated refrigerant flowing away from the pool of liquid refrigerant 82, flows between hood 180 and shell 76 in gap 186 prior to reaching outlet 104 to complete first refrigerant line 190. [0046] FIG. 8 further shows a second refrigerant line 198 that connects outlet 104 of compartment 152 of evaporator 168 with a second compressor 200 and condenser 194, completing a connection between second refrigerant line 198 and first refrigerant line 190. A third refrigerant line 204 connects an outlet 202 of compartment 150, a metering device 206, such as an expansion valve, and distributor 80 of compartment 152. In one exemplary embodiment, third refrigerant line 204 may be positioned inside shell 76. A sensor 188 may be provided to monitor the amount or level of pooled refrigerant 82 contained in compartment 150, which refrigerant exits the compartment through outlet 202 and then travels inside third refrigerant line 204. In one exemplary embodiment, during operation of vapor compression system 170, the fluid pressure in compartment 150 is greater than the fluid pressure in compartment 152. The pressure difference may be achieved by a proper pass arrangement of the process fluid through the tube bundles. The evaporator may have at least two passes of the process fluid. Pass configurations could include: a first pass (fluid inlet) on tube bundle 182; a second pass on tube bundle 78 of compartment 152 (referred to as tube bundle 78/152); a third pass on tube bundle 78 of compartment 150 (referred to as 78/150 tube bundle). If the system has only two passes, then it should be suitable to have tube bundles 182 and 70/152 arranged in parallel for the first pass, and tube bundle 70/150 for the second pass. In a further exemplary embodiment, the difference in pressure between compartments 150 and 152 is sufficiently small so as not to induce excessive stress in partition 172, that could damage the shell.

[0047] FIG. 9 shows a schematic representation of a vapor compression system 171 , similar to vapor compression system 170 (FIG. 8). In place of evaporator 168 in system 170, which utilizes a single shell construction including separate compartments 150 and 152, system 171 uses evaporators 168A and 168B having respective separate shells 76A and 76B. As further shown in FIG. 9, metering device 196 and sensor 188 of evaporator 168 A, as well as a metering device 206 and sensor 189 of evaporator 168B, are configured to work together to ensure sufficient amounts of liquid refrigerant 82 are maintained in each of evaporators 168 A and 168B. That is, in response to sensor 189 sensing a predetermined level of liquid refrigerant 82 in evaporator 168B that is outside of a predetermined range, in combination with a predetermined setting of metering device 206 and a sensed level of refrigerant 84 in evaporator 168A, metering device 196 is activated to result in a corresponding metering of refrigerant provided by first refrigerant line 190 to the distributor associated with hood 180 of evaporator 168A, thereby maintaining sufficient liquid refrigerant in each of the evaporators. Depending on the refrigerant charge of the various vessels, it may be necessary to add an additional intermediate vessel, such as a liquid receiver, to first refrigerant line 190 and positioned between condenser 194 and metering device 196. The pressure difference may be achieved by a proper pass arrangement of the process fluid through the tube bundles, similar to that discussed in FIG. 8.

[0048] FIG. 10 shows an exemplary embodiment of an evaporator 208 in a schematic representation of a vapor compression system 175. Vapor compression system 175 is similar to vapor compression system 170 (FIG. 8), except that evaporator 208 differs from evaporator 168 (FIG. 8). Evaporator 208 has a first partition 172A that is oriented substantially horizontally, while evaporator 168 has a substantially vertically oriented first partition 172. Compartments 150A and 152A in evaporator 208 are positioned within shell 76 and separated by first partition 172A. In another exemplary embodiment, partition 172A may be positioned in an orientation between a horizontal direction and a vertical direction, that is, in a diagonal direction. As further shown in FIG. 10, liquid contained in upper compartment 150A is applied to the distributor positioned in lower compartment 152A. Hoods 180A and 180B are similar to respective hoods 180 (FIG. 8). In one exemplary embodiment, first partition 172 A includes a protrusion 173. Collectively, shell 76, first partition 172A and protrusion 173 define hood 180B that is positioned in compartment 152A and covers tube bundle 212. As further shown in FIG. 10, hood 180A covers tube bundle 21 1. In a further exemplary embodiment, additional partitions may be used to divide the shell into more than two compartments. The pressure difference may be achieved by a proper pass arrangement of the process fluid through the tube bundles, similar to that discussed in FIG. 8.

[0049] In at least one exemplary embodiment of each of vapor compression systems 170, 171 and 175, compressors 192 and 200 may be configured to substantially match discharge pressures at condenser 194. [0050] FIG. 1 1 shows an exemplary embodiment of an evaporator 208A, similar to evaporator 208 (FIG. 10). Evaporator 208A includes a first partition 172B having a first portion 210 connecting and extending between opposed second portions 213, which second portions 213 further extend and connect to shell 76. In one exemplary embodiment, first portion 210 is positioned in a substantially horizontal orientation, and second portions 213 are positioned in a substantially non-horizontal or diagonal orientation near hood 180B. In a further exemplary embodiment, second portions 213 extend upwardly with respect to first portion 210 toward shell 76. In the exemplary embodiment shown in FIG. 1 1 , first partition 172B has a shape that collects the liquid refrigerant not evaporated in the upper rube bundle. First portion 210 includes one or more apertures that are connected to feeder lines 214 that supply liquid refrigerant 82 from compartment 150A to the distributors contained within hood 180C. In a yet further exemplary embodiment, as shown in FIG. 1 IA, a shell assembly 230 includes a shell portion 232 and a shell 236. Shell portion 232 includes an opening 234 configured to receive shell 236. Upon assembly of shell portion 232 and shell 236 to form shell assembly 230, a common surface 238, which is the portion of shell 236 that is inserted inside of opening 234 of shell portion 232, is configured to collect a liquid. Shell portion 238 can have apertures and feeder lines 214 similar to first portion 210.

[0051] While only certain features and embodiments of the invention have been shown and described, many modifications and changes may occur to those skilled in the art (for example, variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (for example, temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (that is, those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the claimed invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

Claims

WHAT IS CLAIMED IS:

1. A heat exchanger for use in a vapor compression system comprising: a shell; a first partition; a first tube bundle; a hood; a distributor; wherein the first tube bundle comprising a plurality of tubes extending substantially horizontally in the shell; wherein the first partition divides the shell into at least two separate compartments; wherein the hood is positioned in a first compartment of the at least two compartments; wherein the hood covers the first tube bundle; and wherein the distributor is configured and positioned to distribute fluid onto at least one tube of the first tube bundle.

2. The heat exchanger of claim 1 wherein the hood comprises a portion of the shell and a second partition.

3. The heat exchanger of claim 1 wherein the first partition is oriented in a substantially vertical position.

4. The heat exchanger of claim 1 wherein the first partition is oriented in a substantially horizontal position.

5. The heat exchanger of claim 1 further comprises a second tube bundle positioned near the first tube bundle.

6. The heat exchanger of claim 1 wherein a second compartment of the at least two compartments is configured for heat transfer with refrigerant.

7. The heat exchanger of claim 2 wherein a gap separates the first partition from the second partition,

8. The heat exchanger of claim 7 wherein the gap is configured to guide fluid exiting the at least one of the at least two compartments.

9. A vapor compression system comprising: a first compressor, a condenser, and an evaporator connected by a first refrigerant line; the evaporator comprising: a shell; a partition; a first tube bundle; a hood; a distributor; wherein the first tube bundle comprising a plurality of tubes extending substantially horizontally in the shell; wherein the partition divides the shell into at least two separate compartments; wherein the hood is positioned in a first compartment of the at least two compartments; wherein the hood covers the first tube bundle; and wherein the distributor is configured and positioned to distribute fluid onto at least one tube of the first tube bundle.

10. The system of claim 9 wherein the first refrigerant line comprises a first connection to the first compartment of the at least two compartments.

11. The system of claim 10 wherein the first refrigerant line comprises a second connection to the first compartment of the at least two compartments.

12. The system of claim 9 further comprises a second refrigerant line that is connected to the first refrigerant line.

13. The system of claim 12 further comprises a second compressor connected in the second refrigerant line.

14. The system of claim 13 wherein the second refrigerant line is connected to a second compartment of the at least two compartments.

15. The system of claim 14 further comprises a third refrigerant line connected to the first compartment and the second compartment.

16. The system of claim 15 wherein the third refrigerant line is positioned inside the shell

17. The system of claim 15 further comprises a second tube bundle positioned in the second compartment.

18. The system of claim 9 wherein a second compartment is configured for heat transfer with refrigerant .

19. The system of claim 15 further comprises a sensor configured and positioned to monitor a fluid level in the first compartment, wherein measurements from the sensor are used to control fluid flow in the third refrigerant line.

20. The system of claim 9 wherein the first compartment of the at least two compartments is positioned at least partially above a second compartment of the at least two compartments.

21. The system of claim 20 wherein a fluid pressure in the first compartment of the at least two compartments is greater than a fluid pressure in the second compartment of the at least two compartments.

22. The system of claim 21 further comprises a third refrigerant line connected to the first compartment of the at least two compartments and the second compartment of the at least two compartments.

23. The system of claim 9 wherein the partition is configured and positioned to collect a liquid.

24. The system of claim 23 further comprises a shell assembly comprising the shell and a shell portion comprising an opening configured to receive the shell, wherein upon assembly of the shell and the shell portion, a common surface between the shell and the shell portion forms the partition.