EVAPORATOR AND CENTRIFUGAL CHILLER PROVIDED WITH THE SAME

Abstract

Provided is an evaporator capable of, in a centrifugal chiller using a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG, preventing dry-out of a group of heat transfer pipes in an evaporator to increase heat transfer performance and to suppress reduced efficiency due to carryover of the low pressure refrigerant in a liquid phase to a turbo compressor side and a centrifugal chiller provided with same. An evaporator (7) comprises a pressure container (21) into which a refrigerant is compressed and introduced, a refrigerant inlet (22) provided on a lower portion of the pressure container, a refrigerant outlet (23) provided on an upper portion of the pressure container, a group of heat transfer pipes (25) that exchange heat with the refrigerant through the interior of the pressure container and a tabular refrigerant distribution plate (26) installed between the refrigerant inlet and the group of heat transfer pipes and in which refrigerant flow holes (26a) are drilled. The surface ratio of the refrigerant flow holes per unit area on the refrigerant distribution plate in an area (A1) corresponding to a position near the upstream side of the group of heat transfer pipes is greater than that in another area (A2).

Claims

1. An evaporator comprising: a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed; a refrigerant inlet which is provided in a lower portion of the pressure container; a refrigerant outlet which is provided in an upper portion of the pressure container; a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored, wherein an area ratio of the refrigerant circulation holes per unit area in the refrigerant distribution plate in a region corresponding to the vicinity of a position on an upstream side of the group of heat transfer pipes is greater than the area ratio thereof in the remaining region.

2. The evaporator according to claim 1, wherein the refrigerant inlet is provided at an intermediate portion in the longitudinal axial direction of the pressure container, and wherein the area ratio of the refrigerant circulation holes in the refrigerant distribution plate in regions at end portions of the refrigerant distribution plate in the longitudinal axial direction is greater than the area ratio thereof in a region at the intermediate portion in the longitudinal axial direction.

3. An evaporator comprising: a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed; a refrigerant inlet which is provided in a lower portion of the pressure container; a refrigerant outlet which is provided in an upper portion of the pressure container; a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored, wherein a plurality of the refrigerant inlets are provided in a dispersed manner along the longitudinal axial direction of the pressure container.

4. An evaporator comprising: a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed; a refrigerant inlet which is provided in a lower portion of the pressure container; a refrigerant outlet which is provided in an upper portion of the pressure container; a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored, wherein a cross-sectional flow channel area from an outer opening portion of the refrigerant inlet to the pressure container is enlarged from the outer opening portion toward the pressure container.

5. An evaporator comprising: a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed; a refrigerant inlet which is provided in a lower portion of the pressure container; a refrigerant outlet which is provided in an upper portion of the pressure container; a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored, wherein the refrigerant inlet has a shape of a pipe connected to the pressure container, and a flow velocity attenuation member attenuating a flow velocity of the low pressure refrigerant is provided inside the pipe.

6. The evaporator according to claim 1, wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.

7. The evaporator according to claim 1, wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.

8. The evaporator according to claim 7, wherein the refrigerant circulation holes bored in the refrigerant distribution plate are disposed vertically below the gaps.

9. The evaporator according to claim 1, wherein a demister positioned between the refrigerant outlet and the group of heat transfer pipes inside the pressure container and performing gas-liquid separation of the low pressure refrigerant is disposed immediately above the group of heat transfer pipes.

10. The evaporator according to claim 9, wherein the demister is provided such that the entire circumference thereof is in contact with an inner circumference of the pressure container.

11. The evaporator according to claim 1, wherein each of the heat transfer pipes configuring the group of heat transfer pipes is installed while penetrating a plurality of heat transfer pipe support plates having a plane direction intersecting the longitudinal axial direction of the pressure container and being disposed at intervals in the longitudinal axial direction of the pressure container, and installation intervals of the heat transfer pipe support plates in the vicinity of a position on an upstream side of the group of heat transfer pipes are narrower than the installation intervals of the heat transfer pipe support plates in the remaining position.

12. A centrifugal chiller comprising: a turbo compressor which compresses a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG; a condenser which causes the compressed low pressure refrigerant to be condensed; and the evaporator according to claim 1 which causes the expanded low pressure refrigerant to evaporate.

13. The evaporator according to claim 2, wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.

14. The evaporator according to claim 3, wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.

15. The evaporator according to claim 4, wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.

16. The evaporator according to claim 5, wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.

17. The evaporator according to claim 2, wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.

18. The evaporator according to claim 3, wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.

19. The evaporator according to claim 4, wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.

20. The evaporator according to claim 5, wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0049] FIG. 1 is a general view of a centrifugal chiller according to an embodiment of the present invention.

[0050] FIG. 2 is a side view of an evaporator illustrating a first embodiment of the present invention seen in a direction of the arrow II in FIG. 1.

[0051] FIG. 3 is a longitudinal-sectional view of the evaporator taken along line III-III in FIG. 2.

[0052] FIG. 4 is a longitudinal-sectional view of the evaporator taken along line IV-IV in FIG. 2.

[0053] FIG. 5 is a side view of an evaporator illustrating a second embodiment of the present invention.

[0054] FIG. 6 is a longitudinal-sectional view of an evaporator illustrating a third embodiment of the present invention.

[0055] FIG. 7 is a view seen in a direction of the arrow VII in FIG. 6.

[0056] FIG. 8A is a longitudinal-sectional view of a refrigerant inlet illustrating a fourth embodiment of the present invention.

[0057] FIG. 8B is a longitudinal-sectional view of another refrigerant inlet illustrating the fourth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0058] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0059] FIG. 1 is a general view of a centrifugal chiller according to an embodiment of the present invention. A centrifugal chiller 1 is configured in a unit state including a turbo compressor 2 that compresses a refrigerant, a condenser 3, a high-pressure expansion valve 4, an economizer 5, a low-pressure expansion valve 6, an evaporator 7, a lubricant tank 8, a circuit box 9, an inverter unit 10, an operation panel 11, and the like. The lubricant tank 8 is a tank storing lubricant supplied to bearings, a speed increaser, and the like of the turbo compressor 2.

[0060] The condenser 3 and the evaporator 7 are formed in cylindrical shell shapes having high pressure resistance and are disposed so as to be parallel and adjacent to each other in a state where their axial lines extend in a substantially horizontal direction. The condenser 3 is disposed at a position relatively higher than the evaporator 7, and the circuit box 9 is installed below thereof. The economizer 5 and the lubricant tank 8 are installed being interposed between the condenser 3 and the evaporator 7. The inverter unit 10 is installed in an upper portion of the condenser 3, and the operation panel 11 is disposed above the evaporator 7. The lubricant tank 8, the circuit box 9, the inverter unit 10, and the operation panel 11 are disposed such that each thereof does not significantly stick out of the entire contour of the centrifugal chiller 1 in a plan view.

[0061] The turbo compressor 2 is a known centrifugal turbine-type compressor which is rotatively driven by an electric motor 13. The turbo compressor 2 is disposed above the evaporator 7 in a posture having its axial line extending in the substantially horizontal direction. The electric motor 13 is driven by the inverter unit 10. As described below, the turbo compressor 2 compresses a gas-phase refrigerant supplied through a refrigerant outlet 23 of the evaporator 7 via a suction pipe 14. A low pressure refrigerant such as R1233zd used at a maximum pressure of less than 0.2 MPaG is used as the refrigerant.

[0062] A discharge port of the turbo compressor 2 and the upper portion of the condenser 3 are connected to each other through a discharge pipe 15, and the bottom portion of the condenser 3 and the bottom portion of the economizer 5 are connected to each other through a refrigerant pipe 16. In addition, the bottom portion of the economizer 5 and the evaporator 7 are connected to each other through a refrigerant pipe 17, and an upper portion of the economizer 5 and a middle stage of the turbo compressor 2 are connected to each other through a refrigerant pipe 18. The high-pressure expansion valve 4 is provided in the refrigerant pipe 16, and the low-pressure expansion valve 6 is provided in the refrigerant pipe 17.

First Embodiment

[0063] FIGS. 2 to 4 illustrate a first embodiment of the evaporator 7.

[0064] As illustrated in FIG. 2, the evaporator 7 is configured to include a pressure container 21 having a cylindrical shell shape extending in the horizontal direction, a refrigerant inlet 22 provided in a lower portion of the pressure container 21, the refrigerant outlet 23 provided in an upper portion of the pressure container 21, a group of heat transfer pipes 25 passing through the inside of the pressure container 21 in a longitudinal axial direction, a refrigerant distribution plate 26, and a demister 27.

[0065] Each of the refrigerant inlet 22 and the refrigerant outlet 23 is disposed at an intermediate portion in the longitudinal axial direction of the pressure container 21. The refrigerant inlet 22 is formed in a short pipe shape extending horizontally and tangentially from the bottom portion of the pressure container 21, and the refrigerant outlet 23 is formed in a short pipe shape extending vertically upward from the upper portion of the pressure container 21. As illustrated in FIG. 1, the refrigerant pipe 17 extending from the bottom portion of the economizer 5 is connected to the refrigerant inlet 22, and the suction pipe 14 of the turbo compressor 2 is connected to the refrigerant outlet 23.

[0066] An inlet chamber 31 is provided on a lower side at one end (for example, the left end in FIG. 2) and an outlet chamber 32 is provided above the inlet chamber 31, as independent rooms inside the pressure container 21. In addition, a U-turn chamber 33 is provided as an independent room at the other end (for example, the right end in FIG. 2) inside the pressure container 21. All these chambers 31, 32, and 33 are disposed lower than the demister 27. An inlet nozzle 34 is provided in the inlet chamber 31, and an outlet nozzle 35 is provided in the outlet chamber 32.

[0067] As illustrated in FIGS. 2, 3 and 4, the group of heat transfer pipes 25 includes a group of outbound pipes 25A extending from one end (the left end in FIG. 2) to the other end (the right end in FIG. 2) in the longitudinal axial direction inside the pressure container 21, and a group of inbound pipes 25B communicating with the group of outbound pipes 25A at the other end in the longitudinal axial direction inside the pressure container 21 and returning from the other end to the one end in the longitudinal axial direction inside the pressure container 21. Specifically, the group of outbound pipes 25A is arranged so as to link the inlet chamber 31 and the lower portion of the U-turn chamber 33 with each other, and the group of inbound pipes 25B is arranged so as to link the outlet chamber 32 and the upper portion of the U-turn chamber 33 with each other. That is, the group of outbound pipes 25A is disposed below inside the pressure container 21, and the group of inbound pipes 25B is disposed above inside the pressure container 21.

[0068] For example, as a cooling target liquid to be cooled by the refrigerant, water (tap water, purified water, distilled water, or the like) flows in through the inlet nozzle 34. The water which has flowed in through the inlet chamber 31 flows through the group of outbound pipes 25A and makes a U-turn in the U-turn chamber 33. Thereafter, the water flows through the group of inbound pipes 25B and flows out through the outlet nozzle 35 via the outlet chamber 32 as chilled water.

[0069] As illustrated in FIGS. 3 and 4, the group of outbound pipes 25A and the group of inbound pipes 25B configuring the group of heat transfer pipes 25 have configurations in which a plurality (for example, four each) of heat transfer pipe bundles 25a each having a number of heat transfer pipes bundled therein are arrayed in parallel in the horizontal direction. Gaps S1 extending in a vertical direction are formed among the heat transfer pipe bundles 25a. In addition, a gap S2 extending in the horizontal direction is formed between the group of outbound pipes 25A and the group of inbound pipes 25B.

[0070] As illustrated in FIG. 2, each of the heat transfer pipes configuring the group of heat transfer pipes 25 (25A, 25B) is fixed inside the pressure container 21 while being supported by a plurality of heat transfer pipe support plates 37 inside the pressure container 21. The heat transfer pipe support plates 37 are formed in flat plate shapes having a plane direction intersecting the longitudinal axial direction of the pressure container 21. The plurality of heat transfer pipe support plates 37 are disposed at intervals in the longitudinal axial direction of the pressure container 21 and are fixed to an inner surface of the pressure container 21. A number of penetration holes are bored in the heat transfer pipe support plates 37, and the heat transfer pipes are tightly inserted through the penetration holes.

[0071] In the installation intervals of the heat transfer pipe support plates 37 along the longitudinal axial direction of the pressure container 21, installation intervals L1 in the vicinity of a position on an upstream side of the group of heat transfer pipes 25, that is, in the vicinity of a position on an upstream side of the group of outbound pipes 25A (the left side in FIG. 2) are set to be narrower than installation intervals L2 in the remaining position. For example, L1 is approximately half of L2.

[0072] Meanwhile, as illustrated in FIGS. 2 to 4, the refrigerant distribution plate 26 is installed between the refrigerant inlet 22 and the group of heat transfer pipes (group of outbound pipes 25A) inside the pressure container 21. The refrigerant distribution plate 26 is a tabular member in which a number of refrigerant circulation holes 26a are bored.

[0073] The area ratio of the refrigerant circulation holes 26a per unit area in the refrigerant distribution plate 26 in a region A1 corresponding to the vicinity of a position on an upstream side of the group of heat transfer pipes 25 (25A) is greater than the area ratio in the remaining region, for example, in a region A2 corresponding to a position of an intermediate section of the group of heat transfer pipes 25. In addition, the area ratio of the refrigerant circulation holes 26a in the regions A1 and A3 at both end portions of the refrigerant distribution plate 26 in the longitudinal axial direction is greater than the area ratio thereof in the region A2 at the intermediate portion in the longitudinal axial direction. As an example, the area ratios of the refrigerant circulation holes 26a in the regions A1 and A3 can range from 33% to 38%, and the area ratio of the refrigerant circulation holes 26a in the region A2 can range from 24% to 33%. However, the area ratios are not limited to these regions only.

[0074] As illustrated in FIGS. 3 and 4, the refrigerant circulation holes 26a of the refrigerant distribution plate 26 are disposed vertically below the gaps S1 which extend in the vertical direction and are formed between the plurality of heat transfer pipe bundles 25a configuring the group of heat transfer pipes 25 (25A, 25B). That is, in a plan view, the refrigerant circulation holes 26a are arrayed along a longitudinal direction of the gaps S1.

[0075] As illustrated in FIGS. 2 to 4, the demister 27 is disposed between the refrigerant outlet 23 and the group of heat transfer pipes 25 (group of inbound pipes 25B) inside the pressure container 21. For example, the demister 27 is a member which has excellent air-permeability and in which wires are interwoven in a meshed state. The demister 27 performs gas-liquid separation of the low pressure refrigerant. The demister 27 is not limited to the wire mesh, and other porous matters may be employed as long as the matter is air-permeable.

[0076] The demister 27 is attached such that the entire circumference thereof is in contact with the inner circumference of the pressure container 21, the internal space of the pressure container 21 is divided into two above and below fiducially from the demister 27. In addition, the installation height of the demister 27 is set immediately above the group of heat transfer pipes 25. Specifically, the interval between the group of heat transfer pipes 25 and the demister 27 is set to approximately twice the pipe disposition pitch. Meanwhile, a comparatively significant difference in height (for example, approximately 50% or more of the diameter of the pressure container 21) is provided between the demister 27 and the refrigerant outlet 23.

[0077] In the centrifugal chiller 1 including the evaporator 7 configured as described above, the turbo compressor 2 is rotatively driven by the electric motor 13, compresses a gas-phase low pressure refrigerant supplied from the evaporator 7 via the suction pipe 14, and feeds this compressed low pressure refrigerant to the condenser 3 through the discharge pipe 15.

[0078] Inside the condenser 3, when a high temperature low pressure refrigerant compressed in the turbo compressor 2 is subjected to heat exchange with cooling water, condensed heat is cooled, so that the low pressure refrigerant is condensed and liquefied. The low pressure refrigerant caused to be in a liquid phase by the condenser 3 expands after passing through the high-pressure expansion valve 4 provided in the refrigerant pipe 16 extending from the condenser 3. The low pressure refrigerant is transported to the economizer 5 in a gas-liquid mixed state and is temporarily stored therein.

[0079] Inside the economizer 5, the low pressure refrigerant which has expanded through the high-pressure expansion valve 4 in a gas-liquid mixed state is subjected to gas-liquid separation into a gas-phase part and a liquid-phase part. The liquid-phase part of the low pressure refrigerant separated herein is caused to further expand through the low-pressure expansion valve 6 provided in the refrigerant pipe 17 extending from the bottom portion of the economizer 5 and becomes a gas-liquid two-phase flow, thereby being transported to the evaporator 7. In addition, the gas-phase part of the low pressure refrigerant separated in the economizer 5 is transported to a middle stage portion of the turbo compressor 2 via the refrigerant pipe 18 extending from the upper portion of the economizer 5 and is compressed again.

[0080] As illustrated in FIGS. 2 to 4, in the evaporator 7, the low pressure refrigerant which has adiabatically expanded through the low-pressure expansion valve 6 in a low temperature gas-liquid two-phase flow state flows into the pressure container 21 through the refrigerant inlet 22, is dispersed in the longitudinal axial direction of the pressure container 21 below the refrigerant distribution plate 26, and then passes through the refrigerant circulation holes 26a of the refrigerant distribution plate 26, thereby flowing upward. Then, a pool for the low pressure refrigerant is formed inside the pressure container 21. The liquid level in the low pressure refrigerant pool is automatically adjusted so as to be between the group of heat transfer pipes 25 and the demister 27.

[0081] The group of heat transfer pipes 25 (25A, 25B) is in a state of being immersed in the low pressure refrigerant pool inside the pressure container 21 and is subjected to heat exchange with the low pressure refrigerant. Accordingly, water passing through the inside of the group of heat transfer pipes 25 is cooled and turns into chilled water. This chilled water is utilized as a cooling/heating medium for air conditioning, industrial cooling water, or the like.

[0082] The low pressure refrigerant which has evaporated (been gasified) due to heat exchange with the group of heat transfer pipes 25 is subjected to gas-liquid separation by the demister 27. That is, when a gasified low pressure refrigerant (gasified refrigerant) is headed for the refrigerant outlet 23 inside the pressure container 21, a fast flow is formed due to the characteristics of the low pressure refrigerant having specific volume greater than that of a high pressure refrigerant. Then, droplets of the liquid-phase refrigerant which have spouted upward from the low pressure refrigerant pool in a non-gasified state are entrained by the fast flow of the gasified refrigerant and tend to come out through the refrigerant outlet 23, leading to a possibility of occurrence of carry-over.

[0083] However, since these droplets are captured by the porous demister 27, are separated, and fall into the low pressure refrigerant pool due to gravity, the droplets are prevented from being carried over. The gasified refrigerant which has been subjected to gas-liquid separation as described above comes out through the refrigerant outlet 23 and is suctioned and compressed again in the turbo compressor 2 via the suction pipe 14. Thereafter, the freezing cycle is repetitively performed.

[0084] In the evaporator 7, the area ratio of the refrigerant circulation holes 26a in the refrigerant distribution plate 26 installed between the refrigerant inlet 22 and the group of heat transfer pipes 25 (25A, 25B) inside the pressure container 21 in the region A1 corresponding to the vicinity of a position on an upstream side of the group of heat transfer pipes 25 (25A) is greater than the area ratio thereof in the remaining region A2.

[0085] Therefore, a comparatively large portion of the low pressure refrigerant introduced into the pressure container 21 through the refrigerant inlet 22 is distributed to the vicinity of a position on an upstream side of the group of heat transfer pipes 25 (25A). In addition, a relatively small amount of the low pressure refrigerant is distributed to the remaining position. Accordingly, the liquid level (froth level) in the low pressure refrigerant pool inside the pressure container 21 is caused to be even.

[0086] In the vicinity of a position on an upstream side of the group of heat transfer pipes 25 (25A) inside the pressure container 21, since there is a significant temperature difference between the low pressure refrigerant and water flowing inside the group of heat transfer pipes 25 (25A), the low pressure refrigerant intensely boils. However, as described above, since a relatively large portion of the low pressure refrigerant is distributed to this position compared to the remaining position, the vicinity of a position on an upstream side of the group of heat transfer pipes 25 (25A) is in circumstances prevented from being surrounded by boiling froth of the low pressure refrigerant and being dried out, so that so that it is possible to maintain a state where the group of heat transfer pipes 25 (25A, 25B) is immersed in refrigerant two-phase liquid. Therefore, the cooling target liquid flowing inside the group of heat transfer pipes 25 (25A, 25B) and the low pressure refrigerant can be favorably subjected to heat exchange, so that it is possible to enhance heat transfer performance of the group of heat transfer pipes 25 (25A, 25B).

[0087] As described above, the froth level in the low pressure refrigerant pool at the intermediate portion in the longitudinal axial direction of the pressure container does not rise higher than those in both the end portions in the longitudinal axial direction. Therefore, as in the present embodiment, when the refrigerant outlet 23 leading to the suction pipe 14 of the turbo compressor is provided at the intermediate portion in the longitudinal axial direction of the pressure container 21, the liquid-phase refrigerant is effectively prevented from hitching the flow of the gasified refrigerant and being carried over to the turbo compressor 2 side, so that it is possible to suppress deterioration in efficiency of the turbo compressor 2.

[0088] In addition, in the evaporator 7, the refrigerant inlet 22 is provided at the intermediate portion in the longitudinal axial direction of the pressure container 21, and the area ratio of the refrigerant circulation holes 26a in the refrigerant distribution plate 26 in the regions A1 and A3 at both the end portions of the refrigerant distribution plate 26 in the longitudinal axial direction is greater than the area ratio thereof in the region A2 at the intermediate portion in the longitudinal axial direction.

[0089] Therefore, a large portion of the low pressure refrigerant introduced into the pressure container 21 through the refrigerant inlet 22 provided at the intermediate portion in the longitudinal axial direction of the pressure container 21 is supplied to both the end portions in the longitudinal axial direction inside the pressure container 21, and a relatively small portion thereof is supplied to the intermediate portion in the longitudinal axial direction of the pressure container 21 immediately above the refrigerant inlet 22. Therefore, the liquid level (froth level) in the low pressure refrigerant pool inside the pressure container 21 is caused to be even, and water flowing inside the group of heat transfer pipes 25 (25A, 25B) and the low pressure refrigerant are favorably subjected to heat exchange, so that it is possible to enhance heat transfer performance of the group of heat transfer pipes 25 (25A, 25B).

[0090] Moreover, the group of heat transfer pipes 25 of the evaporator 7 includes the group of outbound pipes 25A extending from one end to the other end in the longitudinal axial direction inside the pressure container 21, and the group of inbound pipes 25B communicating with the group of outbound pipes 25A at the other end in the longitudinal axial direction inside the pressure container 21 and returning from the other end and to the one end in the longitudinal axial direction inside the pressure container 21. The group of outbound pipes 25A is disposed below and the group of inbound pipes 25B is disposed above inside the pressure container 21.

[0091] When the group of heat transfer pipes 25 is configured as described above, the group of outbound pipes 25A, in which the temperature difference between the low pressure refrigerant and water flowing inside the heat transfer pipes is significant and boiling of the low pressure refrigerant becomes intense, is disposed in the lower portion of the pressure container 21, and the group of inbound pipes 25B, in which the temperature difference between the low pressure refrigerant and water flowing inside the heat transfer pipes is small and boiling of the low pressure refrigerant subsides, is disposed in the upper portion of the pressure container 21.

[0092] Therefore, the low pressure refrigerant intensely boils below the liquid surface (deep part) in the low pressure refrigerant pool inside the pressure container 21, and the liquid-phase refrigerant is unlikely to scatter on the liquid surface in the low pressure refrigerant pool. Therefore, the liquid-phase refrigerant is prevented from being entrained by the flow of the gasified refrigerant and being carried over to the turbo compressor 2 side, so that it is possible to suppress deterioration in efficiency of the turbo compressor 2.

[0093] In the group of heat transfer pipes 25 (25A, 25B), a plurality of heat transfer pipes each having a plurality of heat transfer pipe bundles 25a bundled therein are arrayed in the horizontal direction and the gaps S1 extending in the vertical direction are formed across the heat transfer pipe bundles 25a.

[0094] The vertical gaps S1 across the plurality of heat transfer pipe bundles 25a serve as passages for boiling froth of the low pressure refrigerant which has boiled through heat exchange with the group of heat transfer pipes 25 (25A, 25B). Accordingly, boiling froth can easily rise to the liquid surface in the low pressure refrigerant pool. Therefore, the group of heat transfer pipes 25 (25A, 25B) is prevented from being surrounded by boiling froth below the liquid surface of the refrigerant and being dried out, so that it is possible to enhance heat transfer performance of the group of heat transfer pipes 25 (25A, 25B).

[0095] In addition, since the refrigerant circulation holes 26a bored in the refrigerant distribution plate 26 are disposed vertically below the gaps S1, the flow of the low pressure refrigerant passing through the refrigerant circulation holes 26a of the refrigerant distribution plate 26 and being discharged upward passes through the gaps S1 and reaches the upper end of the group of heat transfer pipes 25 (25A, 25B). Therefore, it is possible to enhance heat transfer performance of the group of heat transfer pipes 25 (25A, 25B).

[0096] In a case where the low pressure refrigerant is used as in the centrifugal chiller 1, the gas flow velocity inside the pressure container 21 of the evaporator 7 increases due to the characteristics of the low pressure refrigerant having specific volume greater than that of a high pressure refrigerant. Therefore, the distance to a position where droplets of the liquid-phase refrigerant spouting upward from the low pressure refrigerant pool inside the pressure container 21 are separated from the gas-phase refrigerant due to their dead weights becomes comparatively long. Therefore, when the demister 27 is installed at a position higher than the position where the droplets are separated due to their dead weights, the distance from the liquid surface of the refrigerant to the demister 27 becomes long, and the pressure container 21 increases in shell diameter.

[0097] In this evaporator 7, when the demister 27 is disposed immediately above the group of heat transfer pipes 25, the quantity of droplets spouting upward from the low pressure refrigerant pool is reduced by the demister 27, so that droplets of the low pressure refrigerant are restrained from coming out through the refrigerant outlet 23 (from being carried over).

[0098] Moreover, when the demister 27 is disposed immediately above the group of heat transfer pipes 25, the space above the demister 27 relatively increases in height, evaporated mist of the low pressure refrigerant is promoted to be droplets having a large diameter, and the distance to the position where the droplets are separated due to their dead weights is shortened. Therefore, in this regard as well, it is possible to restrain the low pressure refrigerant from being carried over.

[0099] Moreover, in this evaporator 7, the demister 27 is provided such that the entire circumference thereof is in contact with the entire inner circumference of the pressure container 21. Accordingly, the entire gas flow of the low pressure refrigerant inside the pressure container 21 passes through the demister 27, so that flow resistance of the gas flow increases. Therefore, the flow velocity distribution of the gas flow inside the pressure container 21 is equalized, a local peak value of the gas flow velocity decreases, and the rate of generating droplets drops. Moreover, the dead weight separation distance of droplets is shortened, so that it is possible to prevent the low pressure refrigerant from being carried over.

[0100] In addition, in this evaporator 7, the installation intervals L1 of the plurality of heat transfer pipe support plates 37 supporting each of the heat transfer pipes of the group of heat transfer pipes 25 in the vicinity of a position on an upstream side of the group of heat transfer pipes 25 are set to be narrower than the installation intervals L2 in the remaining position.

[0101] In the vicinity of a position on an upstream side of the group of heat transfer pipes 25, since there is a significant temperature difference between water flowing inside the group of heat transfer pipes 25 and the low pressure refrigerant as described above, the low pressure refrigerant intensely boils, and the specific volume of boiling froth thereof is greater than that of the high pressure refrigerant, thereby generating significant vibration compared to a case of using a high pressure refrigerant. Therefore, there is concern that the group of heat transfer pipes 25 will resonate with vibration of boiling froth and will break.

[0102] As described above, when the installation intervals L1 of the heat transfer pipe support plates 37 in the vicinity of a position on an upstream side of the group of heat transfer pipes 25 are caused to be narrower than the installation intervals L2 in the remaining position, installation rigidity in the vicinity on an upstream side of the group of heat transfer pipes 25 is enhanced and resonance is suppressed, so that it is possible to prevent breakage.

Second Embodiment

[0103] FIG. 5 is a side view of an evaporator illustrating a second embodiment of the present invention.

[0104] An evaporator 7A is different from the evaporator 7 (refrigerant inlet 22) of the first embodiment in that a plurality of refrigerant inlets 22A of the pressure container 21 are provided in a dispersed manner along the longitudinal axial direction of the pressure container 21, and other configurations are the same. Therefore, the same reference signs are applied to parts having the same configurations, and description is omitted.

[0105] In the present embodiment, for example, two refrigerant inlets 22A are dispersed along the longitudinal axial direction of the pressure container 21 so as to be separated from each other. The refrigerant inlet 22A may be provided at three or more locations. The refrigerant inlet 22A is the same as the refrigerant inlet 22 of the first embodiment and is formed in a short pipe shape extending horizontally and tangentially from the bottom portion of the pressure container 21. The caliber of each refrigerant inlet 22A is set to be smaller than the caliber of the refrigerant inlet 22 of the first embodiment.

[0106] As described above, since the low pressure refrigerant has significant specific volume compared to a high pressure refrigerant, the volumetric flow rate thereof flowing into the evaporator 7A is significant and the dynamic pressure is high. However, when the pressure loss is increased by reducing the refrigerant circulation holes 26a of the refrigerant distribution plate 26, or the like as befits its characteristics, the velocity of the low pressure refrigerant spouting out through the refrigerant circulation holes 26a increases, thereby leading to vibration or breakage of the group of heat transfer pipes 25.

[0107] As in the evaporator 7A, when two, three, or more refrigerant inlets 22A are provided so as to be separated from each other along the longitudinal axial direction of the pressure container 21, the inflow velocity of the low pressure refrigerant into the pressure container 21 can be reduced compared to a case where a single refrigerant inlet 22 is provided as in the first embodiment. Therefore, the refrigerant circulation holes 26a of the refrigerant distribution plate 26 can increase in diameter. Accordingly, it is possible to reduce the velocity of the low pressure refrigerant spouting out through the refrigerant circulation holes 26a.

[0108] Accordingly, vibration or breakage of the group of heat transfer pipes 25 is prevented, and the liquid-phase low pressure refrigerant is restrained from locally spouting upward or the like and being carried over to the turbo compressor 2 side, so that it is possible to avoid deterioration in efficiency of the turbo compressor 2.

Third Embodiment

[0109] FIG. 6 is a longitudinal-sectional view of an evaporator illustrating a third embodiment of the present invention, and FIG. 7 is a view seen in a direction of the arrow VII in FIG. 6.

[0110] In an evaporator 7B, a cross-sectional flow channel area from an outer opening portion 22a of the refrigerant inlet 22 provided in the bottom portion of the pressure container 21 to the pressure container 21 is enlarged from the outer opening portion 22a toward the pressure container 21. Specifically, an enlarged flow channel 22b is provided between the outer opening portion 22a and the pressure container 21. The rest of the configuration is similar to that of the evaporator 7 of the first embodiment in FIG. 3. Therefore, the same reference signs are applied to parts having the same configurations, and description is omitted.

[0111] For example, the enlarged flow channel 22b is formed in a box shape, and its cross-sectional flow channel area is set to be greater than the cross-sectional flow channel area of the refrigerant inlet 22. For example, the cross-sectional flow channel area of the enlarged flow channel 22b is set to be greater than the cross-sectional flow channel area of the refrigerant inlet 22 by approximately two to five times. The shape of the enlarged flow channel 22b is not limited to only the box shape, and other shapes may be employed as long as the cross-sectional flow channel area is greater than the outer opening portion 22a of the refrigerant inlet 22. For example, the enlarged flow channel 22b may have a bulge shape or the like. In addition, it is possible to consider that the refrigerant inlet 22 is formed to have a tapered pipe shape which increases in diameter from its outer opening portion 22a toward the pressure container 21 side, without providing the enlarged flow channel 22b.

[0112] In this manner, when the cross-sectional flow channel area from the outer opening portion 22a of the refrigerant inlet 22 to the pressure container 21 is enlarged toward the pressure container 21, the flow velocity of the low pressure refrigerant flowing through the refrigerant inlet 22 is reduced toward the pressure container 21.

[0113] Therefore, vibration or breakage of the group of heat transfer pipes 25 is prevented by reducing the velocity of the low pressure refrigerant spouting out through the refrigerant circulation holes 26a of the refrigerant distribution plate 26. Moreover, the liquid-phase low pressure refrigerant is restrained from locally spouting upward or the like and being carried over to the turbo compressor 2 side, so that it is possible to avoid deterioration in efficiency of the turbo compressor 2.

Fourth Embodiment

[0114] FIGS. 8A and 8B are longitudinal-sectional views of an evaporator illustrating a fourth embodiment of the present invention.

[0115] An evaporator 7C is different from the evaporator 7 (refrigerant inlet 22) of the first embodiment in that a flow velocity attenuation member for attenuating the flow velocity of the low pressure refrigerant is provided inside the pipe of the refrigerant inlet 22, and other configurations are the same.

[0116] As the flow velocity attenuation member, it is possible to consider that a porous plate (punching plate or the like) 22c is installed inside the pipe of the refrigerant inlet 22 as illustrated in FIG. 8A or a plurality of baffle plates 22d are installed inside the pipe of the refrigerant inlet 22 in a maze state as illustrated in FIG. 8B. As long as the flow velocity of the low pressure refrigerant inside the pipe of the refrigerant inlet 22 can be attenuated, a different member other than those described above may be installed as the flow velocity attenuation member.

[0117] In this manner, when the porous plate 22c or the baffle plate 22d serving as the flow velocity attenuation member is provided inside the pipe of the refrigerant inlet 22, the flow velocity of the low pressure refrigerant flowing into the pressure container 21 through the refrigerant inlet 22 is reduced.

[0118] Therefore, vibration or breakage of the group of heat transfer pipes 25 is prevented by reducing the velocity of the low pressure refrigerant spouting out through the refrigerant circulation holes 26a of the refrigerant distribution plate 26. Moreover, the liquid-phase low pressure refrigerant is restrained from locally spouting upward or the like and being carried over to the turbo compressor 2 side, so that it is possible to avoid deterioration in efficiency of the turbo compressor 2.

[0119] As described above, according to the evaporators 7, 7A, 7B, and 7C and the centrifugal chiller 1 provided with these evaporator of the present embodiment, in the centrifugal chiller 1 using a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG, the group of heat transfer pipes 25 is prevented from being dried out inside the evaporator and heat transfer performance is enhanced. Moreover, it is possible to suppress deterioration in efficiency caused due to the liquid-phase low pressure refrigerant carried over to the turbo compressor 2 side.

[0120] The present invention is not limited to only the configurations of the embodiments described above, and changes or modifications can be suitably added. An embodiment having such changes or modifications added thereto is also included in the scope of rights of the present invention. For example, the first to fourth embodiments may be combined or the like.

REFERENCE SIGNS LIST

[0121] 1 CENTRIFUGAL CHILLER [0122] 2 TURBO-COMPRESSOR [0123] 3 CONDENSER [0124] 7 EVAPORATOR [0125] 21 PRESSURE CONTAINER [0126] 22 REFRIGERANT INLET [0127] 22a OUTER OPENING PORTION OF REFRIGERANT INLET [0128] 22b ENLARGED FLOW CHANNEL [0129] 22c POROUS PLATE (FLOW VELOCITY ATTENUATION MEMBER) [0130] 22d BAFFLE PLATE (FLOW VELOCITY ATTENUATION MEMBER) [0131] 23 REFRIGERANT OUTLET [0132] 25 GROUP OF HEAT TRANSFER TUBES [0133] 25A GROUP OF OUTBOUND TUBES [0134] 25B GROUP OF INBOUND TUBES [0135] 25a HEAT TRANSFER TUBE BUNDLE [0136] 26 REFRIGERANT DISTRIBUTION PLATE [0137] 26a REFRIGERANT CIRCULATION HOLE [0138] 27 DEMISTER [0139] 37 HEAT TRANSFER TUBE SUPPORT PLATE [0140] A1 REGION CORRESPONDING TO VICINITY OF POSITION ON UPSTREAM SIDE OF GROUP OF HEAT TRANSFER TUBES (REGION AT END PORTION OF REFRIGERANT DISTRIBUTION PLATE IN LONGITUDINAL AXIAL DIRECTION) [0141] A2 REGION CORRESPONDING TO OTHER POSITIONS OF GROUP OF HEAT TRANSFER TUBES (REGION AT INTERMEDIATE PORTION OF REFRIGERANT DISTRIBUTION PLATE IN LONGITUDINAL AXIAL DIRECTION) [0142] A3 REGION AT END PORTION OF REFRIGERANT DISTRIBUTION PLATE IN LONGITUDINAL AXIAL DIRECTION [0143] L1, L2 INSTALLATION INTERVAL OF HEAT TRANSFER TUBE SUPPORT PLATE [0144] S1 GAP