HK1205246B

HK1205246B - Heat exchanger

Info

Publication number: HK1205246B
Application number: HK15105824.4A
Authority: HK
Inventors: 沼田光春; 笠井一成
Original assignee: Daikin Industries, Ltd.
Priority date: 2012-04-23
Filing date: 2013-03-15
Publication date: 2018-05-11

Description

Heat exchanger

Technical Field

The present invention relates generally to a heat exchanger suitable for use in a vapor compression system. More particularly, the present invention relates to a heat exchanger including a sump portion extending below at least one of the heat transfer tubes to accumulate refrigerant therein.

Background

Vapor compression refrigeration is the most commonly used method in air conditioning of large buildings and 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 a liquid to a vapor while absorbing heat from the 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 a liquid to be cooled is circulated, and which is contained inside a cylindrical shell. Several methods are known to enable the refrigerant to evaporate in this type of evaporator. In a flooded evaporator (f.o.), the shell is filled with liquid refrigerant and the heat transfer tubes are immersed in a pool of liquid refrigerant to boil and/or evaporate the liquid refrigerant into vapor. In a falling film evaporator (english) liquid refrigerant is deposited onto the outer surface of the heat transfer tubes from above, thereby forming a layer or film of liquid refrigerant along the outer surface of the heat transfer tubes. Heat from the heat transfer tube walls is transferred by convection and/or conduction through the liquid film to the vapor-liquid interface where a portion of the liquid refrigerant evaporates, removing heat from the water flowing inside the heat transfer tubes. The liquid refrigerant that has not evaporated falls vertically from the heat transfer pipe at the upper position toward the heat transfer pipe at the lower position by the force of gravity. There are also hybrid falling film evaporators (hybrid falling film evaporators) in which liquid refrigerant is deposited onto the outer surface of some of the heat transfer tubes in the tube bundle, while other heat transfer tubes in the tube bundle are submerged into the liquid refrigerant collected at the bottom of the shell.

Although flooded evaporators exhibit high heat transfer performance, flooded evaporators require large amounts of refrigerant because the heat transfer tubes are submerged in a pool of liquid refrigerant. With the recent development of new and high cost refrigerants with lower global warming potential, such as R1234ze or R1234yf, it is desirable to reduce the refrigerant charge in the evaporator. The main advantage of falling film evaporators is that good heat transfer performance is ensured while the refrigerant charge is reduced. Falling film evaporators therefore have great potential to replace flooded evaporators in large refrigeration systems.

Us patent No.5,839,294 discloses a hybrid falling film evaporator having a section operating in a flooded mode and a section operating in a falling film mode. More specifically, the evaporator disclosed in this disclosure includes an outer shell through which a plurality of horizontal heat transfer tubes in a tube bundle pass. The distribution system is disposed in overlying relation to the uppermost horizontal surface of the heat transfer tubes in the tube bundle so that refrigerant entering the shell is distributed over the tops of the tubes. The liquid refrigerant forms a film along the outer wall of each of the heat transfer tubes in which a portion of the liquid refrigerant evaporates into vapor refrigerant. The remainder of the liquid refrigerant collects in the lower portion of the shell. In steady state operation, the level of liquid refrigerant within the shell is maintained at a level such that at least 25% of the horizontal heat transfer tubes near the lower end of the shell are submerged in the liquid refrigerant. Thus, in the present disclosure, the evaporator operates with the heat transfer tubes in the lower section of the shell operating in a flooded heat transfer mode, while the heat transfer tubes that are not submerged in liquid refrigerant operate in a falling film heat transfer mode.

Us patent No.7,849,710 discloses a falling film evaporator in which liquid refrigerant collected in the lower portion of the evaporator shell is recirculated. More specifically, the evaporator disclosed in the present disclosure includes a shell having a tube bundle with a plurality of heat transfer tubes extending substantially horizontally in the shell. Liquid refrigerant entering the shell is directed from the distributor to the heat transfer tubes. The liquid refrigerant forms a film along an outer wall of each of the heat transfer tubes, and a part of the liquid refrigerant is evaporated into vapor refrigerant in each of the heat transfer tubes. The remaining liquid refrigerant collects in the lower portion of the shell. In the present disclosure, a pump or ejector is provided to suck the liquid refrigerant collected in the lower portion of the shell to recirculate the liquid refrigerant from the lower portion of the shell to the distributor.

Disclosure of Invention

The problem with the hybrid falling film evaporator disclosed in U.S. patent No.5,839,294, as noted above, is that it still requires a relatively large charge of refrigerant due to the presence of a flooded section at the bottom of the shell. On the other hand, with the evaporator disclosed in U.S. patent No.7,849,710, which recirculates collected liquid refrigerant from the lower portion of the shell to the distributor, in the event of dry spot formation caused by evaporator performance fluctuations, an excessive amount of circulating refrigerant is required to rewet the dry spots on the heat transfer tubes. Further, when a compressor in a vapor compression system utilizes lubricating oil (refrigerant oil), oil migrating from the compressor into the refrigerant circuit of the vapor compression system tends to accumulate in the evaporator because the oil is less volatile than the refrigerant. Thus, with a refrigerant recirculation system as disclosed in U.S. patent No.7,849,710, oil may be recirculated within the evaporator along with the liquid refrigerant, which may result in a high concentration of oil in the liquid refrigerant circulating in the evaporator. Thus, the performance of the evaporator is degraded.

In view of the above, it is an object of the present invention to provide a heat exchanger that can reduce the refrigerant charge amount while ensuring good performance of the heat exchanger.

Another object of the present invention is to provide a heat exchanger which accumulates refrigerant oil migrating from a compressor into a refrigeration circuit of a vapor compression system and discharges the refrigerant oil outside an evaporator.

An exchanger according to an aspect of the present invention is adapted for use in a vapor compression system and includes a shell, a distribution section, a tube bundle, and a trough section. The shell has a longitudinal central axis extending substantially parallel to a horizontal plane. The distribution portion is disposed inside the shell and is configured and arranged to distribute the refrigerant. The tube bundle includes a plurality of heat transfer tubes disposed inside the shell below the distribution portion such that the refrigerant discharged from the distributor is supplied to the tube bundle. The heat transfer tubes extend generally parallel to a longitudinal central axis of the shell. The water sump portion extends below the at least one heat transfer pipe substantially in parallel with a longitudinal center axis of the shell to accumulate the refrigerant therein. The water trough portion at least partially overlaps the at least one heat transfer tube when viewed in a horizontal direction perpendicular to the longitudinal center axis of the shell.

An exchanger according to another aspect of the invention is adapted for use in a vapor compression system and includes a shell, a distribution section, a tube bundle, and a trough section. The shell has a longitudinal central axis extending substantially parallel to a horizontal plane. The distribution portion is disposed inside the shell and is configured and arranged to distribute the refrigerant. The tube bundle includes a plurality of heat transfer tubes disposed inside the shell below the distribution portion such that the refrigerant discharged from the distributor is supplied to the tube bundle. The heat transfer tubes extend generally parallel to a longitudinal central axis of the shell. The sump portion extends below the at least one heat transfer tube, generally parallel to the longitudinal central axis of the shell, such that at least a portion of the at least one heat transfer tube is submerged in refrigerant accumulated in the sump portion when the heat exchanger is operating under normal conditions.

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.

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 a vapor compression system including a heat exchanger according to a first embodiment of the present invention.

FIG. 3 is a simplified perspective view of a heat exchanger according to a first embodiment of the present invention;

fig. 4 is a simplified perspective view of the internal structure of a heat exchanger according to a first embodiment of the present invention;

fig. 5 is an exploded view of the internal structure of a heat exchanger according to a first embodiment of the present invention;

FIG. 6 is a simplified longitudinal cross-sectional view of a heat exchanger according to a first embodiment of the present invention taken along section line 6-6' in FIG. 3;

FIG. 7 is a simplified cross-sectional view of a heat exchanger according to a first embodiment of the present invention, taken along section line 7-7' in FIG. 3;

FIG. 8 is an enlarged schematic cross-sectional view of the heat transfer pipe and the water tank portion disposed in region X of FIG. 7, showing a state in which the heat exchanger is being used, according to the first embodiment of the invention;

FIG. 9 is an enlarged cross-sectional view of a heat transfer tube and one trough section of a trough portion according to a first embodiment of the present invention;

FIG. 10 is a partial side view of the heat transfer tube and trough section according to a first embodiment of the present invention, as viewed in the direction of arrow 10 in FIG. 9;

fig. 11A is a graph of the relationship between the total heat transfer coefficient and the overlapping distance between the water tank part and the heat transfer pipe according to the first embodiment of the present invention, and fig. 11B to 11D are simplified cross-sectional views of samples used for plotting the graph shown in fig. 11A;

FIG. 12 is a simplified cross-sectional view of a heat exchanger showing a first modified example of a configuration of a tube bundle and a trough section in accordance with a first embodiment of the present invention;

FIG. 13 is a simplified cross-sectional view of a heat exchanger showing a second modification of the tube bundle configuration in accordance with the first embodiment of the present invention;

FIG. 14 is a simplified cross-sectional view of a heat exchanger showing a third modification of the tube bundle configuration in accordance with the first embodiment of the present invention;

FIG. 15 is a simplified cross-sectional view of a heat exchanger showing a fourth modification of the tube bundle configuration in accordance with the first embodiment of the present invention;

FIG. 16 is an enlarged schematic cross-sectional view of the heat transfer pipe and the water tank portion arranged in region Y of FIG. 15, showing a state in which the heat exchanger is being used, according to the first embodiment of the invention;

FIG. 17 is a simplified cross-sectional view of a heat exchanger showing a fifth modified example of the arrangement of the tube bundle and the trough portion in accordance with the first embodiment of the present invention;

FIG. 18 is a simplified cross-sectional view of a heat exchanger showing a sixth modified example of the arrangement of the tube bundle and the trough portion in accordance with the first embodiment of the present invention;

FIG. 19 is a simplified cross-sectional view of a heat exchanger according to a second embodiment of the present invention;

FIG. 20 is a simplified cross-sectional view of a heat exchanger according to a third embodiment of the present invention;

FIG. 21 is a simplified cross-sectional view of a heat exchanger showing a first modified example of the arrangement of the tube bundle and the trough portion in accordance with a third embodiment of the present invention;

FIG. 22 is a simplified cross-sectional view of a heat exchanger showing a second modified example of the arrangement of the tube bundle and the trough portion in accordance with a third embodiment of the present invention;

FIG. 23 is a simplified cross-sectional view of a heat exchanger showing a third modified example of the arrangement of the tube bundle and the trough portion in accordance with a third embodiment of the present invention;

FIG. 24 is a simplified cross-sectional view of a heat exchanger according to a fourth embodiment of the present invention; and

fig. 25 is a simplified longitudinal cross-sectional view of a heat exchanger according to a fourth embodiment of the present invention.

Detailed Description

Selected embodiments of the present invention will now be described with reference to the accompanying 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.

First, referring to fig. 1 and 2, a vapor compression system including a heat exchanger according to a first embodiment will be described. As seen in fig. 1, the vapor compression system according to the first embodiment is a refrigerator that may be used in a heating, ventilation, and air conditioning (HVAC) system as an air conditioner for a large building or the like. The vapor compression system of the first embodiment is configured and arranged to remove heat (e.g., water, ethylene glycol, calcium chloride brine, etc.) from a liquid to be cooled via a vapor-compression refrigeration cycle.

As shown in fig. 1 and 2, the vapor compression system includes the following four main components: evaporator 1, compressor 2, condenser 3 and expansion device 4.

The evaporator 1 is a heat exchanger which removes heat from the liquid to be cooled (in this example water) passing through the evaporator 1 to reduce the temperature of the water as the circulating refrigerant evaporates in the evaporator 1. The refrigerant entering the evaporator 1 is in a two-phase gas/liquid state. The liquid refrigerant evaporates into a vapor refrigerant as it absorbs heat from the water.

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 a higher pressure, higher temperature vapor. The compressor 2 may be any type of conventional compressor such as a centrifugal compressor, a scroll compressor, a reciprocating compressor, a screw compressor, or the like.

Next, the high-temperature, high-pressure vapor refrigerant enters the condenser 3, and the condenser 3 is another heat exchanger that removes heat from the vapor refrigerant to condense it from a gaseous 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 the cooling water or air passing through the condenser 3, and the heat is carried by the cooling water or air to be discharged to the outside of the system.

The condensed liquid refrigerant then enters through an expansion device 4, where the refrigerant experiences a sudden drop in pressure 4. The expansion device 4 may be as simple as a restrictive orifice or as complex as an electronically modulated thermal expansion valve. The sudden pressure drop causes a partial evaporation of the liquid refrigerant, whereby the refrigerant entering the evaporator 1 is in a two-phase gas/liquid state.

Some examples of refrigerants used in vapor compression systems are Hydrofluorocarbon (HFC) based refrigerants such as R-410A, R-407C and R-134 a; hydro fluoro-olefins (HFO); unsaturated HFC-based refrigerants such as R-1234ze and R-1234 yf; natural refrigerants such as R-717 and R-718, or any other suitable type of refrigerant.

The vapour compression system comprises a control unit 5, which control unit 5 is operatively coupled to the drive mechanism of the compressor 2 to control the operation of the vapour compression system.

It will be apparent to those skilled in the art from this disclosure that conventional compressors, condensers, and expansion devices can be used as the compressor 2, condenser 3, and expansion device 4, respectively, 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 known in the art. Since the compressor 2, condenser 3 and expansion device 4 are well known in the art, these structures will not be discussed or illustrated in greater detail herein. The vapour compression system may comprise a plurality of evaporators 1, compressors 2 and/or condensers 3.

Referring now to fig. 3 to 5, a detailed structure of the evaporator 1 as a heat exchanger according to the first embodiment will be explained. As shown in fig. 3 and 6, the evaporator 1 includes a shell 10, the shell 10 having a substantially cylindrical shape with a longitudinal center axis C (fig. 6) extending substantially in a horizontal direction. The shell 10 includes a connecting header member 13 and a return header member 14, wherein the connecting header member 13 defines an inlet chamber 13a and an outlet chamber 13b, and the return header member 14 defines a water chamber 14 a. The connection header member 13 and the return header member 14 are fixedly coupled to the longitudinal ends of the cylindrical body of the shell 10. The inlet chamber 13a and the outlet chamber 13b are separated by a water baffle 13 c. The connecting header member 13 includes a water inlet line 15 through which water enters the housing 10 and a water outlet line 16 through which water exits the housing 10 through the water inlet line 15. As shown in fig. 3 and 6, the shell 10 further includes a refrigerant inlet line 11 and a refrigerant discharge line 12. A refrigerant inlet line 11 is fluidly connected to the expansion device 4 via a supply conduit 6 (fig. 7) to introduce two-phase refrigerant into the shell 10. The expansion device 4 may be coupled directly to the refrigerant inlet line 11. The liquid component in the two-phase refrigerant boils and/or evaporates in the evaporator 1 and undergoes a phase change from a liquid state to a gas state as heat is absorbed from the water passing through the evaporator 1. The vapor refrigerant is drawn by suction from the refrigerant discharge line 12 into the refrigerant discharge line 12.

Fig. 4 is a simplified perspective view showing an internal structure accommodated in the case 10. Fig. 5 is an exploded view of the internal structure shown in fig. 4. As shown in fig. 4 and 5, the evaporator 1 basically includes a refrigeration section 20, a tube bundle 30 and a water tank section 40. The evaporator 1 preferably further includes a baffle member 50 as shown in fig. 7, but the illustration of the baffle member 50 is omitted in fig. 4 to 6 for the sake of brevity.

The distribution portion 20 is constructed and arranged to function as a gas-liquid separator and a refrigerant distributor. As shown in fig. 5, the distribution portion 20 includes an inlet piping portion 21, a first tray portion 22, and a plurality of second tray portions 23.

As shown in fig. 6, the inlet conduit portion 21 extends substantially parallel to the longitudinal center axis C of the housing 10. The inlet line portion 21 is fluidly connected to the refrigerant inlet line 11 of the shell 10 such that two-phase refrigerant is introduced into the inlet line portion 21 via the refrigerant inlet line 11. The inlet pipe portion 21 includes a plurality of openings 21a disposed along the longitudinal length of the inlet pipe portion 21 for discharging two-phase refrigerant. When the two-phase refrigerant is discharged from the opening 21a of the inlet pipe portion 21, the liquid component of the two-phase refrigerant discharged from the opening 21a of the inlet pipe portion 21 is received by the first tray portion 22. On the other hand, the vapor component of the two-phase refrigerant flows upward and impinges on the baffle member 50 as shown in fig. 7, so that liquid droplets entrained in the vapor are captured by the baffle member 50. The liquid droplets captured by the baffle member 50 are guided along the inclined surface of the baffle member 50 toward the first tray section 22. The baffle member 50 may be constructed as a plate member, a mesh, or the like. The vapor component flows down the baffle member 50 and then changes its direction upward toward the discharge line 12. The vapor refrigerant is discharged toward the compressor 2 via a discharge line 12.

As shown in fig. 5 and 6, the first tray portion 22 extends substantially parallel to the longitudinal center axis C of the housing 10. As shown in fig. 7, the bottom surface of the first tray portion 22 is disposed below the inlet pipe portion 21 to receive the liquid refrigerant discharged from the opening 21a of the inlet pipe portion 21. In the first embodiment, as shown in fig. 7, the inlet piping portion 21 is disposed inside the first tray portion 22 so that a vertical gap is not formed between the bottom surface of the first tray portion 22 and the inlet piping portion 21. In other words, in the first embodiment, as shown in fig. 6, most of the inlet piping portion 21 overlaps with the first tray portion 22 when viewed in the horizontal direction perpendicular to the longitudinal center axis C of the casing 10. This configuration is advantageous because the total volume of liquid refrigerant accumulated in the first tray portion 22 can be reduced while maintaining the level (height) of liquid refrigerant accumulated in the first tray portion 22 relatively high. Alternatively, the inlet pipe section 21 and the first tray section 22 may be configured to form a large vertical gap between the bottom surface of the first tray section 22 and the inlet pipe section 21. The inlet pipe section 21, the first tray section 22 and the baffle member 50 are preferably coupled together and suspended in a suitable manner in the upper part of the shell 10 from above.

As shown in fig. 5 and 7, the first tray part 22 has a plurality of first discharge hole ports 22a, and the liquid refrigerant accumulated therein is discharged downward. The liquid refrigerant discharged from the first discharge hole ports 22a of the first tray part 22 is received by one of the second tray parts 23 disposed below the first tray part 22.

As shown in fig. 5 and 6, the dispensing section 20 of the first embodiment includes three identical second tray sections 23. The second tray portions 23 are aligned side-by-side along the longitudinal center axis C of the housing 10. As shown in fig. 6, the total longitudinal length of the three second tray portions 23 is substantially the same as the longitudinal length of the first tray portion 22 shown in fig. 6. As shown in fig. 7, the transverse width of the second tray section 23 is set to be greater than the transverse width of the first tray section 22 so that the second tray section 23 extends over substantially the entire width of the tube bundle 30. The second tray portions 23 are configured such that the liquid refrigerant accumulated in the second tray portions 23 is not communicated between the second tray portions 23. As shown in fig. 5 and 7, each of the second tray portions 23 has a plurality of second discharge orifices 23a, and the liquid refrigerant is discharged from the plurality of second discharge orifices 23a downward toward the tube bundle 30.

It will be understood by those skilled in the art from this disclosure that the structure and configuration of the dispensing portion 20 is not limited to the structures and configurations disclosed herein. Any conventional structure for distributing liquid refrigerant down tube bundle 30 may be used in the practice of the present invention. For example, a conventional dispensing system utilizing nozzles and/or spray tree tubes may be used as the dispensing portion 20. In other words, any conventional distribution system compatible with falling film evaporators can be used as the distribution portion 20 to practice the present invention.

The tube bundle 30 is disposed below the distribution portion 20 such that the liquid refrigerant discharged from the distribution portion 20 is supplied onto the tube bundle 30. As shown in fig. 6, the tube bundle 30 includes a plurality of heat transfer tubes 31 extending substantially parallel to the longitudinal center axis C of the shell 10. The heat transfer pipe 31 is made of a material having high thermal conductivity such as metal. The heat transfer pipe 31 is preferably provided with inner grooves and outer grooves to further promote heat exchange between the refrigerant and water flowing inside the heat transfer pipe 31. Such heat transfer tubes including inner and outer grooves are well known in the art. For example, a Thermoexel-E tube supplied from Hitachi Cable ltd. may be used as the heat transfer pipe 31 of the present embodiment. As shown in fig. 5, the heat transfer pipe 31 is supported by a plurality of vertically extending support plates 32, and the support plates 32 are fixedly coupled to the shell 10. In the first embodiment, the tube bundle 30 is configured to form a two-pass system in which the heat transfer tubes 31 are divided into a supply line group disposed at a lower portion of the tube bundle 30 and a return line group disposed at an upper portion of the tube bundle 30. As shown in fig. 6, the inlet ends of the heat transfer tubes 31 in the supply line group are fluidly connected to the water inlet pipe 15 via the water inlet chambers 13a of the connecting header member 13, so that the water entering the evaporator 1 is distributed to the heat transfer tubes 31 in the supply line group. The discharge ends of the heat transfer tubes 31 in the supply line group and the inlet ends of the heat transfer tubes 31 of the return line pipe are in fluid communication with the water chamber 14a of the return header member 14. Therefore, the water flowing inside the heat transfer tubes 31 in the supply line group is discharged into the water chamber 14a, and redistributed into the heat transfer tubes 31 in the return line group. The discharge ends of the heat transfer tubes 31 in the return line group are in fluid communication with the water outlet pipe 16 via the water outlet chamber 13b of the connecting header member 13. Therefore, the water flowing inside the heat transfer tubes 31 in the return line group leaves the evaporator 1 through the water outlet line 16. In a typical two pass evaporator, the temperature of the water entering the inlet line 15 may be about 54 ° f (about 12 ℃), while the water is cooled to about 44 ° f (about 7 ℃) as it exits the outlet line 16. Although in the present embodiment the evaporator 1 is configured as a two-pass system with water entering and exiting on the same side of the evaporator 1, it will be apparent to those skilled in the art from this disclosure that other conventional systems, such as a single pass or three pass system, can be used. In addition, in a two-channel system, the return line group may be disposed below or alongside the supply line group instead of the configuration shown herein.

The detailed arrangement of the heat transfer mechanism of the evaporator 1 according to the first embodiment will be explained with reference to fig. 7. Fig. 7 is a simplified cross-sectional view of evaporator 1 taken along section line 7-7' in fig. 3.

As described above, the refrigerant in a two-phase state is supplied to the inlet line portion 21 of the distributing portion 20 through the inlet line 11 by the supply pipe 6. In fig. 7, the refrigerant flow in the refrigerant circuit is schematically shown, and the inlet line 11 is omitted for the sake of simplicity. The vapor component of the refrigerant supplied to the distribution portion 20 is separated from the liquid component in the first tray section 22 of the distribution portion 20 and leaves the evaporator 1 through the discharge line 12. On the other hand, the liquid component of the two-phase refrigerant accumulates in the first tray section 22, then in the second tray section 23, and is discharged from the discharge orifices 23a of the second tray section 23 downward toward the tube bundle 30.

As shown in fig. 7, the tube bundle 30 of the first embodiment includes a falling film region F and an accumulation region a. The heat transfer tubes 31 in the falling film region F are configured and arranged to perform falling film evaporation of the liquid refrigerant distributed from the distribution portion 20. More specifically, the heat transfer pipes 31 in the falling film region F are configured such that the liquid refrigerant distributed from the distributing portion 20 is caused to form a layer (or film) along the outer wall of each of the heat transfer pipes 31, wherein the liquid refrigerant evaporates as vapor refrigerant when absorbing heat from water flowing from the inside of the heat transfer pipes 31. As shown in fig. 7, the heat transfer pipes 31 in the falling film region F are arranged in a plurality of vertical lines (as shown in fig. 7) extending parallel to each other when viewed in a direction parallel to the longitudinal center axis C of the shell 10. Therefore, in each of the rows of the heat transfer tubes 31, the refrigerant falls downward from one heat transfer tube to another heat transfer tube by the action of gravity. The rows of the heat transfer pipes 31 are arranged with respect to the second discharge openings 23a of the second tray portion 23 such that the liquid refrigerant discharged from the second discharge openings 23a is deposited onto the uppermost heat transfer pipe of the heat transfer pipes 31 in each of these rows. In the first embodiment, as shown in fig. 7, the rows of the heat transfer pipes 31 in the falling film region F are arranged in a staggered pattern. In the first embodiment, the vertical spacing between two adjacent ones of the heat transfer tubes 31 in the falling film region F is substantially constant. Also, the horizontal pitch between two adjacent ones of the columns of the heat transfer pipes 31 in the falling film region F is substantially constant.

The liquid refrigerant that is not evaporated in the falling film region F continues to fall by gravity down into the accumulation region a, in which a water trough portion 40 is provided as shown in fig. 7. The sump portion 40 is constructed and arranged to accumulate the liquid refrigerant flowing from above so that the heat transfer pipes 31 in the accumulation region a are at least partially submerged in the liquid refrigerant accumulated in the sump portion 40. The number of rows of heat transfer tubes 31 in the accumulation region a provided with the water trough portion 40 is preferably about 10% to about 20% of the total number of rows of heat transfer tubes 31 of the tube bundle 30. In other words, the ratio of the number of rows of heat transfer tubes 31 in the accumulation region a to the number of heat transfer tubes 31 in one column in the falling film region F is preferably about 1:9 to about 2: 8. Alternatively, when the heat transfer tubes 31 are arranged in an irregular pattern (e.g., different numbers of heat transfer tubes in each of the columns), the number of heat transfer tubes 31 arranged in the accumulation region a (i.e., at least partially submerged in the liquid refrigerant accumulated in the sump portion 40) is preferably from about 10% to about 20% of the total number of heat transfer tubes in the tube bundle 30. In the example shown in fig. 7, the water trough portion 40 is provided in two rows of heat transfer tubes 31 in the accumulation region a, while each of the columns of heat transfer tubes 31 in the falling film region F includes ten rows (i.e., the total number of rows in the tube bundle 30 is twelve rows). From the present disclosure, it will be appreciated by those skilled in the art that when the evaporator has a larger capacity with a larger number of heat transfer tubes, the number of columns of heat transfer tubes in the falling film region F and/or the number of rows of heat transfer tubes in the accumulation region a will also increase.

As shown in fig. 7, the sump portion 40 includes a first sump section 41 and a pair of second sump sections 42. As can be seen in fig. 6, the first and second water groove sections 41, 42 extend substantially in parallel with the longitudinal center axis C of the shell 10 over substantially the same longitudinal length as that of the heat transfer pipe 31. The first and second sump sections 41, 42 of the sump portion 40 are spaced from the inner surface of the shell 10 when viewed along the longitudinal center axis C shown in fig. 7. The first and second water tank sections 41 and 42 may be made of various materials such as metal, alloy, resin, and the like. In the first embodiment, the first and second water tank sections 41 and 42 are made of a metal material such as a steel plate (steel thin plate). The first and second water tank sections 41 and 42 are supported by the support plate 32. The support plate 32 includes openings (not shown) disposed at locations corresponding to interior regions of the first tank section 41 to place all sections of the tank section 41 in fluid communication along the longitudinal length of the first tank section 41. Thus, liquid refrigerant accumulated in the first water channel section 41 is in fluid communication along the longitudinal length of the water channel section 41 via the openings in the support plate 32. Likewise, openings (not shown) are provided in the support plate 32 at locations corresponding to the interior area of each of the second tank sections 42 to place all sections of the second tank section 42 in fluid communication along the longitudinal length of the second tank section 42. Thus, liquid refrigerant accumulated in the sump section 42 is fluidly communicated along the longitudinal length of the second sump section 42 via the openings of the support plates 32.

As shown in fig. 7, the first water groove section 41 is disposed below the lowermost row of heat transfer tubes 31 in the accumulation region a, and the second water groove section 42 is disposed below the second lowermost row of heat transfer tubes 31. As shown in fig. 7, the second lowermost row of the heat transfer pipes 31 in the accumulation region a is divided into two groups, and each of the second water channel segments 2 is arranged below each of the two groups, respectively. A gap is formed between the second sump sections 42 to allow the liquid refrigerant to overflow from the second sump sections 42 toward the first sump section 41.

In the first embodiment, as shown in fig. 7, the heat transfer tubes 31 in the accumulation region a are arranged such that the outermost heat transfer tubes of the heat transfer tubes 31 in each row of the accumulation region a are arranged outside the outermost columns of heat transfer tubes 31 in the falling film region F on each side of the tube bundle 30. Since the vapor flow within the shell 10 causes the liquid refrigerant flow to spread outwardly as it proceeds toward the lower region of the tube bundle 30, preferably, as shown in fig. 7, at least one heat transfer tube is disposed in each row of the accumulation region a, which is disposed outside the outermost column of heat transfer tubes 31 in the falling film region F.

Fig. 8 shows an enlarged sectional view of the region X in fig. 7, schematically showing the evaporator 1 in a state of use under normal conditions. For the sake of simplicity, water flowing inside the heat transfer pipe 31 is not shown in fig. 8. As shown in fig. 8, the liquid refrigerant forms a film along the outer surface of the heat transfer pipe 31 in the falling film region F, and part of the liquid refrigerant evaporates into vapor refrigerant. However, as the liquid refrigerant evaporates as vapor refrigerant, the amount of liquid refrigerant descending along the heat transfer tubes 31 decreases as it proceeds toward the lower regions of the tube bundle 30. In addition, if the distribution of the liquid refrigerant from the distribution portion 20 is uneven, there is a greater possibility of dry spots forming in the heat transfer tubes arranged in the lower region of the tube bundle 30, which is disadvantageous in heat transfer. Thus, in the first embodiment of the present invention, the sump portion 40 is provided in the accumulation area a disposed in the lower region of the tube bundle 30 to accumulate the liquid refrigerant flowing from above and redistribute the accumulated refrigerant in the longitudinal direction of the shell C. Therefore, all the heat transfer pipes 31 in the accumulation region a are at least partially immersed in the liquid refrigerant collected in the sump portion 40 according to the first embodiment. Thus, dry spots can be prevented from being formed in the lower region of the tube bundle 30, and good heat transfer efficiency of the evaporator 1 can be ensured.

For example, as shown in fig. 8, when the heat transfer pipe 31 labeled "1" receives a small amount of refrigerant, the heat transfer pipe 31 labeled "2", which is the heat transfer pipe 31 disposed immediately below the heat transfer pipe labeled "1", does not receive liquid refrigerant from above. However, as the liquid refrigerant flows along the other heat transfer tubes 31, the liquid refrigerant accumulates in the second water groove section 42. Therefore, the heat transfer tubes 31 disposed immediately above the second water tank section 42 are at least partially immersed in the liquid refrigerant accumulated in the second water tank section 42. Further, even when the heat transfer tubes 31 are only partially immersed in the liquid refrigerant accumulated in the second sump section 42 (i.e., a portion of each of the heat transfer tubes 31 is exposed), the liquid refrigerant accumulated in the sump section 42 may rise along the exposed surface of the outer wall of the heat transfer tubes 31 as indicated by the arrows in fig. 8 due to capillary action. Thus, the liquid refrigerant accumulated in the second water trough section 42 boils and/or evaporates while absorbing heat from the water passing through the heat transfer tubes 31. Furthermore, the second sump section 42 is designed to allow liquid refrigerant to overflow from the second sump section 42 onto the first sump section 41. In order to easily receive the liquid refrigerant overflowing from the second water tank section 42, as shown in fig. 7 and 8, the outer edge of the first water tank section 41 is disposed outside the outer edge of the second water tank section 42. As shown in fig. 8, the heat transfer tubes 31 disposed immediately above the first water tank section 41 are at least partially immersed in the liquid refrigerant accumulated in the first water tank section 41. Further, even when the heat transfer tubes 31 are only partially immersed in the liquid refrigerant accumulated in the second sump section 41 (i.e., a portion of each of the heat transfer tubes 31 is exposed), the liquid refrigerant in the sump section 41 rises along the exposed surface of the outer wall of the heat transfer tubes 31 that is at least partially immersed in the accumulated refrigerant due to capillary action. Thus, the liquid refrigerant accumulated in the first water groove section 41 boils and/or evaporates while absorbing heat from the water passing through the inside of the heat transfer pipe 31. Therefore, heat transfer effectively occurs between the liquid refrigerant in the accumulation region a and the water flowing inside the heat transfer pipe 31.

With reference to fig. 9 and 10, the detailed structure of the first and second water tank sections 41 and 42, and the arrangement of the first and second water tank sections 41 and 42 with respect to the heat transfer pipe 31 will be described using one second water tank section 42 as an example. As shown in fig. 9, the second water tank section 42 includes a bottom wall portion 42a and a pair of side wall portions 42b extending upward from lateral ends of the bottom wall portion 42 a. Although the side wall portion 42b has an upwardly tapered profile in the first embodiment, the shape of the second water tank section 42 is not limited to this configuration. For example, the side wall portions 42B of the second water tank section 42 may extend parallel to each other (see fig. 11B to 11D).

The bottom wall portion 42a and the side wall portion 42b form a recess in which liquid refrigerant accumulates so that the heat transfer tube 31 is at least partially submerged in the liquid refrigerant accumulated in the second sump section 42 when the evaporator is operating under normal conditions. More specifically, the side wall portion 42b of the second water tank portion 42 partially overlaps the heat transfer pipe 31 disposed directly above the second water tank portion 42 when viewed in the horizontal direction perpendicular to the longitudinal center axis C of the shell 10. Fig. 10 shows the trough section 42 and the heat transfer pipe 31 when viewed in a horizontal direction perpendicular to the longitudinal center axis C of the shell 10. The overlap distance D1 between the side wall portion 42b and the heat transfer pipe 31 disposed immediately above the second sump section 42 is set such that the heat transfer pipe 31 is at least partially submerged in the liquid refrigerant accumulated in the second sump section 42, as viewed in the horizontal direction perpendicular to the longitudinal center axis C of the shell 10. The overlap distance D1 is also set so that the liquid refrigerant reliably overflows from the second sump section 42 when the evaporator 1 is operating under normal conditions. Preferably, the overlap distance D1 is set to be equal to or greater than half the height (outer diameter) D2 of the heat transfer tubes 31 (D1/D2 ≧ 0.5). More preferably, the overlap distance D1 is set to be equal to or greater than three-quarters of the height (outer diameter) of the heat transfer tubes 31 (D1/D2 ≧ 0.75). In other words, the second water groove section 42 is configured such that at least half (or more preferably at least three-quarters) of the height (outer diameter) of each of the heat transfer tubes 31 is submerged in the liquid refrigerant when the second water groove section 42 is filled with the liquid refrigerant to the edge. The overlap distance D1 may be equal to or greater than the height D2 of the heat transfer tubes 31. In this case, the heat transfer tubes 31 are completely submerged in the liquid refrigerant accumulated in the second sump section 42. However, since the refrigerant charge amount increases as the capacity of the second water groove section 42 increases, it is preferable that the overlap distance D1 be substantially equal to or less than the height D2 of the heat transfer tubes 31.

The distance D3 between the bottom wall portion 42a and the heat transfer tubes 31 and the distance D4 between the side wall portions 42b and the heat transfer tubes 31 are not limited to any particular distance as long as sufficient space is formed between the heat transfer tubes 31 and the second trough section 42 to allow the liquid refrigerant to flow between the heat transfer tubes 31 and the second trough section 42. For example, each of the distance D3 and the distance D4 may be set to about 1mm to about 4 mm. Further, distance D3 and distance D4 may be the same or different.

The first sump section 41 has a similar structure to the second sump section 42 described above, except that the height of the first sump section 41 may be the same or different from the height of the second sump section. Since the first water tank section 41 is disposed below the lowermost row of the heat transfer tubes 31, it is not necessary to overflow the liquid refrigerant from the first water tank section 41. Therefore, the total height of the first water tank section 41 can be set higher than that of the second water tank section 42. As explained above, in any case, it is preferable that the overlap distance D1 between the first water groove section 41 and the heat transfer pipe 31 be set equal to or greater than half (or more preferably three-quarters) the height (outer diameter) D2 of the heat transfer pipe 31.

Fig. 11A is a graph of the relationship between the total heat transfer coefficient and the overlap distance D1 between the water trough section and the heat transfer pipe 31 according to the first embodiment. In the graph shown in FIG. 11A, the vertical axis represents the overlap heat transfer coefficient (kw/m)²K) And the horizontal axis represents the overlap distance D1, which overlap distance D1 is expressed by the ratio of the height D2 of the heat transfer pipe 31. Experiments were performed to measure the total heat transfer coefficient using the three samples shown in fig. 11B to 11D. In the first example shown in fig. 11B, the overlap distance D1 between the water tank portion 40' and the heat transfer pipe 31 is equal to the height D2 of the heat transfer pipe 31, and thus is expressed in terms of the ratio of the height of the heat transfer pipe 31Is 1.0. In the second example shown in fig. 11C, the overlap distance D1 between the water tank portion 40 ″ and the heat transfer pipe 31 is equal to three-quarters (0.75) of the height D2 of the heat transfer pipe 31. In the third sample shown in fig. 11D, the overlapping distance D1 between the trough portion 40' ″ and the heat transfer pipe 31 is equal to half (0.5) of the height D2 of the heat transfer pipe 31. In the first to third samples shown in fig. 11B to 11D, the distance D3 between the bottom wall of the trough section and the heat transfer pipe 31 and the distance D4 between the side wall of the trough section and the heat transfer pipe 31 were about 1 mm. The first to third samples were filled with liquid refrigerant (R-134a) to the edge and at different heat flux levels (30 kw/m)²、20kw/m²And 15kw/m²) The overall heat transfer coefficient was measured.

As shown in the graph of fig. 11A, at all heat flux levels, the total heat transfer coefficient in the second sample at an overlap distance of 0.75 (fig. 11C) was substantially the same as the total heat transfer coefficient of the first sample at an overlap distance of 1.0 (fig. 11B). Furthermore, at higher heat flux levels (30 kw/m)²) The overall heat transfer coefficient in the third sample at an overlap distance of 0.5 (FIG. 11D) was about 80% of the overall heat transfer coefficient of the first sample (FIG. 11B), and at a lower heat flux level (20 kw/m)²) Next, the total heat transfer coefficient in the third sample (fig. 11D) was about 90% of that of the first sample (fig. 11B). In other words, even when the overlap distance D1 is half (0.5) the height of the heat transfer pipe 31, there is no significant decrease in performance. Therefore, the overlap distance D1 is preferably set equal to or greater than half (0.5) the height of the heat transfer pipe 31 and more preferably equal to or greater than three-quarters (0.75) the height of the heat transfer pipe 31.

With the evaporator 1 according to the first embodiment, liquid refrigerant is accumulated in the sump portion 40 in the accumulation region a, so that the heat transfer tubes 31 arranged in the lower region of the tube bundle 30 are at least partially immersed in the liquid refrigerant accumulated in the sump portion. Thus, even when the liquid refrigerant is not uniformly distributed from above, it is possible to easily prevent dry spots from being formed in the lower region of the tube bundle 30. Further, with the evaporator 1 according to the first embodiment, since the water tank portion 40 is disposed adjacent to the heat transfer pipe 31 while being spaced apart from the inner surface of the shell 10, the refrigerant charge amount can be significantly reduced, which forms a refrigerant pool in the bottom of the evaporator shell while ensuring good heat transfer performance, as compared with the conventional hybrid evaporator having a flooded section.

The arrangement of the tube bundle 30 and the water trough portion 40 is not limited to the arrangement shown in fig. 7. From the present disclosure, it will be apparent to those skilled in the art that various changes and modifications may be made to the present invention without departing from the scope of the invention. Several modifications will be described with reference to fig. 12 to 18.

Fig. 12 is a simplified cross-sectional view of an evaporator 1A according to the first embodiment, showing a first modification of the arrangement of a tube bundle 30A and a water tank portion 40A. As shown in fig. 12, the evaporator 1A is substantially the same as the evaporator 1 shown in fig. 2-7, except that the outermost heat transfer tubes of the heat transfer tubes 31 in the accumulation region a of each row are vertically aligned with the outermost columns of heat transfer tubes 31 in the falling film region F on each side of the tube bundle 30A. In this case, since the outermost end of the second sump section 42A extends outwardly, liquid refrigerant can be easily received by the second sump section 42A even when the flow of liquid refrigerant expands outwardly as it proceeds toward the lower region of the tube bundle 30A.

Fig. 13 is a simplified cross-sectional view of the evaporator 1B according to the first embodiment, showing a second modified example of the arrangement of the tube bundle 30B and the water tank portion 40B. The evaporator 1B is substantially the same as the evaporator a shown in fig. 12 except that the heat transfer tubes 31 of the tube bundle 30B in the falling film region F are not arranged in a staggered pattern but in a matrix as shown in fig. 13.

Fig. 14 is a simplified cross-sectional view of an evaporator 1C according to the first embodiment, showing a third modified example of the arrangement of a tube bundle 30C and a water tank portion 40C. The evaporator 1C is substantially the same as the evaporator 1B shown in fig. 13 except that the water tank portion 40C includes a single second water tank section 42C continuously extending in the lateral direction. In this case, the liquid refrigerant accumulated in the second water tank section 42C overflows from both lateral sides of the second water tank section 42C toward the first water tank section 41C.

Fig. 15 is a simplified cross-sectional view of the evaporator 1D according to the first embodiment, showing a fourth modified example of the arrangement of the tube bundle 30D and the water tank portion 40D. In the example shown in fig. 15, the water tank portion 40D includes a plurality of independent water tank sections 43 respectively arranged below the heat transfer pipes 31 in the accumulation region a. Fig. 16 is an enlarged schematic cross-sectional view of the heat transfer pipe 31 and the water tank section 43 arranged in the region Y of fig. 15, showing a state in which the evaporator 1D is in use. The liquid refrigerant accumulated in the sump section 43 in the uppermost row in the accumulation region a overflows as shown in fig. 16 for the sump section 42 arranged downward. Therefore, all of the heat transfer tubes 31 in the accumulation region a are at least partially submerged in the liquid refrigerant accumulated in the sump section 43. Therefore, since heat transfer occurs between the liquid refrigerant and the water flowing inside the heat transfer pipe 31, the liquid refrigerant evaporates as a vapor refrigerant.

The shape of the water tank section 43 is not limited to the configuration shown in fig. 15 and 16. For example, the cross-section of the trough section 42 may be C-shaped, V-shaped, U-shaped, and the like. Similar to the example discussed above, the overlap distance between the water tank section 43 and the portion disposed directly above the water tank section 43 is preferably set equal to or greater than half (0.5) the height of the heat transfer pipe 31, more preferably equal to or greater than three-quarters (0.75) the height of the heat transfer pipe 31, as viewed in the horizontal direction perpendicular to the longitudinal center axis C.

Fig. 17 is a simplified cross-sectional view of an evaporator 1E according to the first embodiment, showing a fifth modification of the arrangement of a tube bundle 30E and a water tank portion 40E. As shown in fig. 17, evaporator 1E is substantially the same as evaporator 1D shown in fig. 16, except that the outermost heat transfer tubes of the heat transfer tubes 31 in the accumulation region a of each row are vertically aligned with the outermost columns of heat transfer tubes 31 in the falling film region F on each side of the tube bundle 30E.

Fig. 18 is a simplified cross-sectional view of the evaporator 1F according to the first embodiment, showing a sixth modification of the arrangement of the tube bundle 30F and the water tank portion 40F. The evaporator 1A is substantially the same as the evaporator 1 shown in fig. 2 to 7, except that the arrangement pattern of the heat transfer tubes 31 in the falling film region F is different. More specifically, in the example shown in fig. 18, the heat transfer pipes 31 in the falling film region F are arranged such that the vertical spacing between two adjacent heat transfer pipes 31 of each row of heat transfer pipes 31 in the upper region of the falling film region F is larger than the above-described vertical spacing in the lower region of the falling film region F. Further, the heat transfer pipes 31 in the falling film region F are arranged such that the horizontal spacing between two adjacent rows of heat transfer pipes in the laterally central region of the falling film region F is larger than the above-described horizontal spacing in the outer region of the falling film region F.

The momentum of the vapor flow in the shell 10 tends to be greater in the upper region of the falling film region F than in the lower region of the falling film region F. Likewise, the momentum of the vapor stream in shell 10 tends to be greater in the laterally central region of falling film region F than in the outer regions of falling film region F. Therefore, the vapor velocity in the upper and outer regions of the falling film region F often becomes very high. As a result, the lateral vapor flow causes damage to the vertical flow of the liquid refrigerant between the heat transfer pipes 31. Further, liquid refrigerant may be delivered to the compressor 2 by a high velocity vapor flow, and entrained liquid refrigerant may damage the compressor 2. Therefore, in the example shown in fig. 18, the vertical and horizontal pitches of the heat transfer pipes 31 are adjusted to increase the sectional area of the steam passage formed between the heat transfer pipes 31 in the upper and outer regions of the falling film region F. Thus, the vapor flow velocity in the upper and outer regions of the falling film region F can be reduced. Thus. The vertical flow of liquid refrigerant is prevented from being disrupted and entrained liquid refrigerant from occurring due to the flow of vapor.

Second embodiment

Referring now to fig. 19, an evaporator 101 according to a second embodiment will be described. In view of the similarity between the first and second embodiments, the parts of the second embodiment that are identical to the parts of the first embodiment will be given the same reference numerals as the parts of the first embodiment. Moreover, the descriptions of the parts of the second embodiment that are identical to the parts of the first embodiment may be omitted for the sake of brevity.

The evaporator 101 according to the second embodiment is substantially the same as the evaporator 1 of the first embodiment except that the evaporator 101 of the second embodiment is provided with a refrigerant recirculation system. The sink portion 140 of the second embodiment is substantially identical to the sink portion 40 of the first embodiment. In the first embodiment described above, if the liquid refrigerant is distributed relatively uniformly (e.g., ± 10%) over the tube bundle 30 from the distribution portion 20, the refrigerant charge may be set to a prescribed amount by which substantially all of the liquid refrigerant is evaporated in the falling film region F or the accumulation region a. In such a case, less liquid refrigerant overflows from the first water tank section 41 toward the bottom of the shell 10. However, when the distribution of liquid refrigerant from the distribution portion 20 over the tube bundle 30 is significantly uneven (e.g., ± 20%), there is a high likelihood of dry spots forming in the tube bundle 30. Therefore, in this case, more than a prescribed amount of refrigerant needs to be supplied to the system in order to prevent dry spot formation. Therefore, in the second embodiment, the refrigerant recirculation system is provided to the evaporator 101 to recirculate the liquid refrigerant overflowing from the water tank portion 140 and accumulated in the bottom of the shell 110. As shown in fig. 19, the housing 110 includes a bottom outlet pipe 17 in fluid communication with the pipe 7 coupled to the pump device 7 a. The pump device 7a is selectively operable to recirculate liquid refrigerant accumulated in the bottom of the shell 110 back to the distribution portion 20 of the evaporator 110 via conduit 6 and inlet line 11 (fig. 1). The bottom outlet line 17 may be placed at any longitudinal position of the shell 110.

Alternatively, the pump device 7a may be replaced by an ejector device operating according to the bernoulli principle to use the pressurized refrigerant from the condenser 3 to draw the liquid refrigerant accumulated in the bottom of the shell 110. Such an injector device combines the functions of an expansion device and a valve.

Thus, with the evaporator 110 according to the second embodiment, liquid refrigerant that is not evaporated can be efficiently recirculated and reused for heat transfer, thereby reducing the refrigerant charge amount

In the second embodiment, the arrangement of the tube bundle 130 and the water tank portion is not limited to the arrangement in fig. 19. 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.

Third embodiment

Referring now to fig. 20 to 25, an evaporator 201 according to a third embodiment will be described. In view of the similarity between the third embodiment and the first and second embodiments, the parts of the third embodiment that are identical to the parts of the first or second embodiment will be given the same reference numerals as the parts of the first or second embodiment. Moreover, the descriptions of the parts of the third embodiment that are identical to the parts of the first or second embodiments may be omitted for the sake of brevity.

The evaporator 201 of the third embodiment is similar to the evaporator 101 of the second embodiment in that the evaporator 201 is provided with a refrigerant recirculation system that recirculates liquid refrigerant accumulated in the bottom of the shell 210 via the bottom outlet line 17 and the conduit 7. When the compressor 2 (fig. 1) of the vapour compression system utilizes lubricating oil, the oil tends to migrate from the compressor 2 into the refrigeration circuit of the vapour compression system. In other words, the refrigerant entering the evaporator 201 contains compressor oil (refrigerant oil). Therefore, when the refrigerant recirculation system is provided in the evaporator 201, the oil is recirculated within the evaporator 201 along with the liquid, which causes a higher concentration of the oil in the liquid refrigerant in the evaporator 201, thereby reducing the performance of the evaporator 201. Therefore, the evaporator 201 of the third embodiment is constructed and arranged to accumulate oil using the water tank portion 240, and to discharge the oil accumulated outside the evaporator 201 toward the compressor 2.

More specifically, the evaporator 201 includes a water trough portion 240 disposed below a portion of the lowermost row of heat transfer tubes 31 in the tube bundle 230. The sump portion 240 is fluidly connected to the valve arrangement 8a via a bypass conduit 8. When the oil accumulated in the water tank portion 240 reaches a prescribed level, the valve device 8a is selectively operated to discharge the oil from the water tank portion 240 to the outside of the evaporator 201.

As mentioned above, when the refrigerant entering the evaporator 201 contains compressor oil, the oil is recirculated with the liquid refrigerant through the refrigerant recirculation system. In the third embodiment, the sump portion 240 is configured such that the liquid refrigerant accumulated in the sump portion 240 does not overflow from the sump portion 240. The liquid refrigerant accumulated in the sump portion 240 boils and/or evaporates due to its heat absorption from the water flowing inside the heat transfer pipe 31 submerged in the accumulated liquid refrigerant, while the oil remains in the sump portion 240. Therefore, as the liquid refrigerant is recirculated in the evaporator 201, the concentration of the oil in the sump portion 240 gradually increases. Once the amount of oil accumulated in the water tank portion 240 reaches a prescribed level, the valve device 8a operates and discharges the oil from the evaporator 201. Similar to the first embodiment, the overlap distance between the water tank portion 240 and the heat transfer pipe 31 disposed directly above the water tank portion 240 in the third embodiment is preferably set equal to or greater than half (0.5) the height of the heat transfer pipe 30, and more preferably equal to or greater than three-quarters (0.75) the height of the heat transfer pipe 30, as viewed in the horizontal direction perpendicular to the longitudinal center axis C.

In the third embodiment, the area of the tube bundle 230 provided with the water tank portion 240 constitutes the accumulation area a, and the remaining tube bundle 230 constitutes the falling film area F.

Therefore, with the evaporator 201 of the third embodiment, the compressor oil that migrates from the compressor 2 to the refrigeration circuit can be accumulated in the water tank portion 240 and discharged from the evaporator 201, thereby improving the heat transfer efficiency in the evaporator 201.

In the third embodiment, the arrangement of the tube bundle 130 and the water tank portion is not limited to the arrangement in fig. 20. 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. Several modifications will be explained with reference to fig. 21 to 23.

Fig. 21 is a simplified cross-sectional view of an evaporator 201A according to a third embodiment, showing a first modified example of the arrangement of a tube bundle 230A and a water tank portion 240A. As shown in fig. 21, the water tank portion 240A may be placed in the central region below the lowermost row of the heat transfer pipes 31 instead of the side regions shown in fig. 20.

Fig. 22 is a simplified cross-sectional view of an evaporator 201B according to a third embodiment, showing a second modified example of the arrangement of a tube bundle 230B and a water tank portion 240B. The heat transfer tubes 31 of the tube bundle 230B are not arranged in a staggered pattern, but in a matrix as shown in fig. 22.

Fig. 23 is a simplified cross-sectional view of an evaporator 201C according to a third embodiment, showing a third modified example of the arrangement of a tube bundle 230C and a water tank portion 240C. In this example, the heat transfer tubes 31 of the tube bundle 230C are arranged in a matrix. The water tank portion 240C is disposed in a central region located lowermost below the heat transfer pipe 31.

Further, the heat transfer tubes 31 of the tube bundle 230 according to the third example embodiment may be configured in a similar manner to the heat transfer tubes 31 of the tube bundle 30F shown in fig. 18. In other words, the heat transfer tubes 31 of the tube bundle 230 of the third embodiment may be configured such that the vertical spacing between the heat transfer tubes 31 in the upper region of the tube bundle 230 is greater than the above-described vertical spacing in the lower region of the tube bundle 230, and the horizontal spacing between the heat transfer tubes 31 in the outer region of the tube bundle 230 is greater than the above-described horizontal spacing in the central region of the tube bundle 230.

Fourth embodiment

Referring now to fig. 24 and 25, an evaporator 301 according to a fourth embodiment will be described. In view of the similarity between the first to fourth embodiments, the parts of the fourth embodiment that are identical to the parts of the first, second or third embodiments will be given the same reference numerals as the parts of the first, second or third embodiments. Moreover, the descriptions of the parts of the fourth embodiment that are identical to the parts of the first, second, or third embodiments may be omitted for the sake of brevity.

The evaporator 301 of the fourth embodiment is substantially the same as the evaporator 1 of the first embodiment, except that an intermediate tray portion 60 is provided in the falling film region F between the heat transfer tubes 31 in the supply line group and the heat transfer tubes 31 in the return line group. The intermediate tray portion 60 includes a plurality of discharge openings 60a, and the liquid refrigerant is discharged downward through the plurality of discharge openings 60 a.

As explained above, the evaporator 301 incorporates a two pass system in which water first flows inside the heat transfer tubes 31 in the supply line group provided in the lower region of the tube bundle 30 and then is directed to flow inside the heat transfer tubes 31 in the return line group arranged in the upper region of the tube bundle 30. Therefore, the water flowing inside the heat transfer pipes 31 in the supply line group near the intake chamber 13 has the highest temperature, and thus a larger heat transfer amount is required. For example, as shown in fig. 25, the temperature of water flowing inside the heat transfer pipe 31 in the vicinity of the water intake chamber 13a is the highest. Therefore, a larger heat transfer amount is required in the heat transfer pipe 31 near the intake chamber 13 a. Once this region of the heat transfer pipes 31 is dried due to uneven distribution of the refrigerant from the distribution portion 20, the evaporator 301 is forced to perform heat exchange using a limited surface area of the heat transfer pipes 31 that are not dried, and at this time the evaporator 301 is kept pressure-balanced. In such a case, more than a nominal amount (e.g., up to twice) of refrigerant charge would be required to rewet the dried portions of the heat transfer tubes 31.

Therefore, in the fourth embodiment, the intermediate tray portion 60 is disposed at a position above the heat transfer pipes 31 that require a greater amount of heat transfer. Once the liquid refrigerant falling from above is received by the intermediate tray section 60 and is uniformly redistributed toward the heat transfer tubes 31, the intermediate tray section 60 requires a greater amount of heat transfer. Therefore, it is easy to prevent these portions of the heat transfer pipe 31 from drying out, ensuring good heat transfer performance.

Although in the fourth embodiment, as shown in fig. 25, the intermediate tray section 60 is only partially disposed with respect to the longitudinal direction of the tube bundle 130, the intermediate tray section 60 or a plurality of intermediate tray sections 60 may be disposed to extend substantially over the entire longitudinal length of the tube bundle 330.

Similar to the first embodiment, the configuration for the tube bundle 330 and the water tank portion 40 in the fourth embodiment is not limited to those shown in fig. 24. 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. For example, the intermediate tray portion 60 may be combined in any of the configurations shown in fig. 12-15 and 17-23.

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 description 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. The following directional terms "upper", "lower", "above", "downward", "vertical", "horizontal", "below" and "transverse", as well as any other similar directional terms as used herein to describe the above-described embodiments, refer to those directions of the evaporator when the longitudinal central axis of the evaporator is oriented substantially horizontally as shown in fig. 6 and 7. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to an evaporator as used in a 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 may have intermediate structures disposed between them. The functions of one element may be performed by two, and vice versa. The structure and function of one embodiment may be employed in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Each feature which is different from the prior art, alone or in combination with other features, also should be considered as a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Accordingly, 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.

Claims

1. A heat exchanger adapted for use in a vapor compression system, comprising:

a housing having a longitudinal central axis extending generally parallel to a horizontal plane;

a distribution portion disposed inside the case and configured and disposed to distribute a refrigerant; and

a tube bundle including a plurality of heat transfer tubes arranged inside the shell below the distributing section such that the refrigerant discharged from the distributing section is supplied onto the tube bundle, the heat transfer tubes extending substantially parallel to a longitudinal central axis of the shell; and

a water trough portion extending below the at least one of the heat transfer tubes substantially in parallel with a longitudinal center axis of the shell to accumulate the refrigerant therein, the water trough portion overlapping at least partially with the at least one of the heat transfer tubes when viewed in a horizontal direction perpendicular to the longitudinal center axis of the shell.

2. The heat exchanger of claim 1,

the tube bundle includes a falling film region and an accumulation region disposed below the falling film region, and at least one of the heat transfer tubes is disposed in the accumulation region.

3. The heat exchanger of claim 2,

the heat transfer pipes in the falling film region are arranged in a plurality of rows extending substantially parallel to each other when viewed along the longitudinal center axis of the shell.

4. The heat exchanger of claim 3,

the heat transfer pipes in the accumulation region are arranged in a plurality of rows extending substantially parallel to each other when viewed along the longitudinal center axis of the shell; and

the water tank section includes a plurality of water tank sections that are respectively arranged below the rows of the heat transfer pipes in the accumulation region.

5. The heat exchanger of claim 2,

the water tank portion extends continuously below two or more of the heat transfer pipes arranged in the accumulation region.

6. The heat exchanger of claim 4,

at least one of the water trough sections extends continuously below all of the heat transfer tubes in at least one of the rows in the accumulation region.

7. The heat exchanger of claim 4,

the number of rows of heat transfer tubes in the accumulation region is less than the number of heat transfer tubes in each of the columns in the falling film region.

8. The heat exchanger of claim 7,

the ratio of the number of rows of said heat transfer tubes in said accumulation region to the number of said heat transfer tubes in each of said columns in said falling film region is from about 1:9 to about 2: 8.

9. The heat exchanger of claim 3,

an outermost one of the heat transfer tubes in the accumulation region is positioned, with respect to a lateral direction, outside an outermost one of the columns of the heat transfer tubes of the falling film region when viewed along a longitudinal center axis of the shell.

10. The heat exchanger of claim 2,

the heat transfer pipes are arranged in a plurality of rows extending parallel to each other when viewed along a longitudinal center axis of the shell, wherein at least one of the heat transfer pipes in each of the rows is arranged in the accumulation region.

11. The heat exchanger of claim 10,

the water tank section includes a plurality of water tank segments that are respectively arranged below at least one of the heat transfer pipes of each of the rows.

12. The heat exchanger of claim 11,

the number of heat transfer pipes arranged in the accumulation region in each of the banks is smaller than the number of the heat transfer pipes arranged in the falling film region in each of the banks.

13. The heat exchanger of any one of claims 1 to 12, further comprising:

a supply pipe fluidly connected to the distribution portion to supply the refrigerant to the distribution portion; and

a recirculation pipe fluidly connected to an opening formed on the bottom surface of the case to recirculate the refrigerant accumulated in the bottom surface of the case into the supply pipe.

14. The heat exchanger of claim 13, further comprising:

a bypass conduit fluidly connected to the sump portion to discharge fluid accumulated in the sump portion toward an outside of the shell.

15. A heat exchanger adapted for use in a vapor compression system, comprising:

a water tank portion extending below at least one of the heat transfer tubes substantially parallel to a longitudinal central axis of the shell such that at least a portion of the at least one of the heat transfer tubes is submerged in refrigerant accumulated in the water tank portion when the heat exchanger is operating under normal conditions.