Falling film evaporator and refrigeration system comprising the same

Abstract

The application discloses a falling film evaporator and a refrigeration system comprising the same. The falling film evaporator comprises a shell, a heat exchange tube bundle, a first stage demisting device and a second stage demisting device. The falling film evaporator is arranged such that refrigerant entering the falling film evaporator from an evaporator inlet first exchanges heat with a heat exchange medium in the heat exchange tube bundle, then flows through the first stage demisting device and enters a gas-liquid separation cavity, and finally flows through the second stage demisting device and is discharged from an evaporator outlet. In the falling film evaporator, the liquid droplets in the gaseous refrigerant are removed by reasonably arranging the two-stage demisting device, so that the gas-liquid separation cavity no longer needs to bear or only needs to bear a small amount of gas-liquid separation function. Therefore, the gas-liquid separation cavity does not need to be arranged to be large in size, and the effect of fully removing the liquid droplets in the gaseous refrigerant can be achieved.

Description

Technical Field

[0001] This application relates to the field of refrigeration systems, and particularly to a falling film evaporator and a refrigeration system including the falling film evaporator. Background Technology

[0002] A refrigeration system mainly consists of four components: a compressor, a condenser, a throttling device, and an evaporator. The evaporator is used to evaporate liquid refrigerant into gaseous refrigerant. A falling film evaporator is a commonly used type of evaporator. It includes a falling film tube bundle, and a distributor typically distributes the refrigerant to the surface of the heat exchange tubes, where a liquid film forms and evaporates. Falling film evaporators utilize the thin-film evaporation mechanism on the surface of the heat exchange tubes, offering advantages such as high heat transfer efficiency and low refrigerant charge, making them a research hotspot in the air conditioning industry in recent years.

[0003] A falling film evaporator typically includes a flooded tube bundle at the bottom of the evaporator and a falling film tube bundle above it. The gaseous refrigerant obtained after evaporation through the falling film and flooded tube bundles needs to undergo sufficient gas-liquid separation before being discharged from the falling film evaporator to prevent liquid droplets from being trapped in the gaseous refrigerant entering the compressor. In existing falling film evaporators, the gaseous refrigerant is allowed to flow a sufficiently long path, during which any trapped droplets fall back to the bottom of the evaporator under gravity and re-evaporate through the flooded tube bundle. However, to ensure a sufficiently long flow path for the gaseous refrigerant, the evaporator needs to have a sufficiently large space. Summary of the Invention

[0004] To address the above problems, this application provides a falling film evaporator in a first aspect, comprising: a shell, a heat exchange tube bundle, a first-stage demister, and a second-stage demister. The shell defines a cavity including a communicating heat exchange chamber and a gas-liquid separation chamber. The shell has an evaporator inlet and an evaporator outlet, wherein the heat exchange chamber is in fluid communication with the evaporator inlet, and the gas-liquid separation chamber and the evaporator outlet are in fluid communication. The heat exchange tube bundle is disposed in the heat exchange chamber. The first-stage demister is configured to be located on the flow path of the refrigerant from the heat exchange chamber to the gas-liquid separation chamber. The second-stage demister is configured to be located on the flow path of the refrigerant from the gas-liquid separation chamber to the evaporator outlet. The falling film evaporator is configured such that the refrigerant entering the falling film evaporator from the evaporator inlet first exchanges heat with the heat exchange medium in the heat exchange tube bundle in the heat exchange chamber, then flows through the first-stage demister and into the gas-liquid separation chamber, and finally flows through the second-stage demister and is discharged from the evaporator outlet.

[0005] According to the first aspect above, the housing includes a first housing and a second housing, the first housing and the second housing being interconnected, wherein the heat exchange cavity is defined within the second housing, and the gas-liquid separation cavity is defined between the first housing and the second housing.

[0006] According to the first aspect above, the first-stage demisting device includes several windows, which are disposed on the second housing and are in fluid communication with the heat exchange chamber and the gas-liquid separation chamber.

[0007] According to the first aspect above, the cavity has a length direction, the plurality of windows are arranged side by side along the length direction of the cavity, and in the length direction toward the evaporator outlet, the size of the plurality of windows gradually decreases, and the interval between the plurality of windows gradually increases.

[0008] According to the first aspect described above, the first-stage demister includes a superheated tube bundle. The second housing includes an opening that is in fluid communication with the heat exchange chamber and the gas-liquid separation chamber, and the superheated tube bundle is disposed in the opening.

[0009] According to the first aspect above, the second-stage demisting device includes a filter or a regenerator, wherein the regenerator includes several regenerator tube bundles, and the tube bundles are used for the flow of liquid refrigerant from the condenser.

[0010] According to the first aspect above, the falling film evaporator further includes a distributor in fluid communication with the evaporator inlet, the distributor being configured to distribute refrigerant entering the falling film evaporator from the evaporator inlet to the heat exchange tube bundle. The second-stage demister is disposed above the second housing.

[0011] According to the first aspect described above, the cavity has a width direction. The second housing is disposed inside the first housing, wherein the second housing is connected to the inner side of the first housing on both sides of the cavity in the width direction.

[0012] According to the first aspect described above, the cavity has a width direction. The first housing is connected above the second housing, wherein the first housing is connected to the outer sides of the second housing on both sides of the cavity in the width direction.

[0013] This application provides a refrigeration system in a second aspect, comprising: a compressor, a condenser, a throttling device, and a falling film evaporator as described in any one of the first aspects, all disposed in a refrigerant circuit. Attached Figure Description

[0014] Figure 1 This is a schematic block diagram of the refrigeration system of this application;

[0015] Figure 2 for Figure 1 A three-dimensional structural diagram of a falling film evaporator;

[0016] Figure 3 for Figure 2 A schematic diagram of the axial section of an embodiment of a falling film evaporator;

[0017] Figure 4 for Figure 2 A schematic diagram of the axial section of another embodiment of the falling film evaporator;

[0018] Figure 5A This is a structural schematic diagram of the axial section of another embodiment of the falling film evaporator according to this application;

[0019] Figure 5B for Figure 5A The diagram shows a schematic representation of the radial cross-section of a falling film evaporator.

[0020] Figure 6 This is a structural schematic diagram of the axial section of another embodiment of the falling film evaporator according to this application. Detailed Implementation

[0021] Various specific embodiments of the present invention will now be described with reference to the accompanying drawings, which form part of this specification. It should be understood that although terms indicating direction, such as "front," "rear," "upper," "lower," "left," "right," "top," and "bottom," are used herein to describe various exemplary structural parts and elements, their use is merely for ease of description and is based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed herein can be arranged in different orientations, these terms indicating direction are illustrative only and should not be considered limiting.

[0022] Figure 1 This is a schematic block diagram of the refrigeration system 190 of this application, used to illustrate the location and function of the falling film evaporator 100 in the refrigeration system 190.

[0023] like Figure 1As shown, the refrigeration system 190 includes a compressor 193, a condenser 191, a throttling device 192, and a falling film evaporator 100. These components are connected by pipes to form a closed system, which is filled with refrigerant. The refrigerant flows sequentially through the compressor 193, condenser 191, throttling device 192, and falling film evaporator 100, enabling the refrigeration system 190 to provide cooling to external systems via the falling film evaporator 100. Specifically, the high-pressure gaseous refrigerant discharged from the compressor 193 flows into the condenser 191, where it releases heat and is condensed into a high-pressure liquid refrigerant. It then flows into the throttling device 192, where it is throttled into a low-pressure two-phase refrigerant. This low-pressure gaseous refrigerant then flows through the evaporator inlet 101 of the falling film evaporator 100, where it absorbs heat and evaporates into a low-pressure gaseous refrigerant. Finally, it flows out from the evaporator outlet 102 of the falling film evaporator 100 and re-flows into the compressor 193, completing the refrigerant cycle.

[0024] Figure 2 for Figure 1 A three-dimensional structural diagram of the falling film evaporator 100 is provided to illustrate its external structure. (See diagram for reference.) Figure 2 As shown, the falling film evaporator 100 has a shell 203, which is generally cylindrical in shape and has a length direction L, a width direction W, and a height direction H. The shell 203 is provided with an evaporator inlet 101, an evaporator outlet 102, and inlet and outlet water pipes 206 and 207. The evaporator inlet 101 is located above the middle of the shell 203 and is in fluid communication with the outlet of the throttling device 192 to provide a two-phase refrigerant (gas and liquid) into the cavity inside the shell 203. It should be noted that the flow rate of the refrigerant flowing through the evaporator inlet 101 can be controlled by known control devices such as valves, which will not be specifically described here. Furthermore, depending on the design of the falling film evaporator, multiple evaporator inlets may be provided. The evaporator outlet 102 is in fluid communication with the suction end of the compressor 193 to discharge the gaseous refrigerant evaporated inside the shell 203 to the suction end of the compressor 193. In this embodiment, the evaporator outlet 102 is located above the housing 203 and is spaced a certain distance from the evaporator inlet 101.

[0025] The housing 203 also includes tube sheets 205 at both ends for closing the cylindrical ends, wherein the front tube sheet 205 is provided with inlet and outlet water pipes 206 and 207. In this embodiment, the inlet and outlet water pipes 206 and 207 are in fluid communication with the heat exchange medium and are in fluid communication with the inside of the heat exchange tube in the housing 203, thereby providing the heat exchange medium for heat exchange to the inside of the heat exchange tube.

[0026] Thus, the gas-liquid two-phase refrigerant from the throttling device 192 enters the shell 203 of the falling film evaporator 100 through the evaporator inlet 101. Inside the shell 203, it exchanges heat with the heat exchange medium flowing through the heat exchange tubes. The refrigerant absorbs heat and evaporates into a gas, then exits the falling film evaporator 100 through the evaporator outlet 102 and flows into the suction end of the compressor 193. The heat exchange medium used for heat exchange in the heat exchange tubes flows in and out through the inlet and outlet water pipes 206 and 207. In this embodiment, the heat exchange medium is hot water.

[0027] Figure 3 This is a schematic structural diagram of an axial section of one embodiment of a falling film evaporator 100, used to illustrate the internal structure of the falling film evaporator 100. For example... Figure 3 As shown, the housing 203 has a cavity 308 defined by the housing 203, and the evaporator inlet 101 and evaporator outlet 102 are in fluid communication with the cavity 308. The cavity 308 includes a heat exchange tube bundle 320 extending along the length L of the housing 203. The heat exchange tube bundle 320 includes a flooded tube bundle 322 disposed at the bottom of the cavity 308 and a falling film tube bundle 321 disposed above the flooded tube bundle 322. The flooded tube bundle 322 and the falling film tube bundle 321 are used to circulate a heat exchange medium, i.e., hot water. The hot water exchanges heat with the refrigerant outside the tubes through the tube walls of the flooded tube bundle 322 and the falling film tube bundle 321 to evaporate the refrigerant into a gaseous refrigerant. Furthermore, a pair of baffles 315 are provided on the outer sides of the falling film tube bundle 321 in the width direction W, which restrict the direction of refrigerant flow through the falling film tube bundle 321 to approximately downwards. Since the refrigerant has a higher liquid content at the top, the baffle 315 can effectively prevent the gaseous refrigerant with a high liquid content from flowing downwards and instead flowing directly to the evaporator outlet 102.

[0028] In this embodiment, the housing 203 includes a first housing 311 and a second housing 312, with the second housing 312 connected inside the first housing 311. The cavity 308 includes a heat exchange cavity 316 and a gas-liquid separation cavity 317, which are fluidly connected through several windows 336. The cavity 308 is defined by the first housing 311, the heat exchange cavity 316 is defined by the second housing 312, and the gas-liquid separation cavity 317 is defined between the first housing 311 and the second housing 312. A heat exchange tube bundle 320 is disposed in the heat exchange cavity 316 to allow the refrigerant to exchange heat within the heat exchange cavity 316. After heat exchange, the resulting gaseous refrigerant enters the gas-liquid separation cavity 317, where gas-liquid separation occurs due to the density difference between gas and liquid during the flow of the gaseous refrigerant. As a more specific embodiment, the first housing 311 is generally cylindrical, and the second housing 312 is partially cylindrical. The diameter of the first housing 311 is larger than the diameter of the second housing 312, and the second housing 312 is connected to the inner side of the bottom of the first housing 311 on both sides in the width direction W. Those skilled in the art will understand that when the second housing 312 is connected to the first housing 311 in the width direction W, the second housing 312 may or may not be connected to the first housing 311 in the length direction L. For example, the length of the second housing 312 may be less than that of the first housing 311, so that the second housing 312 is not connected to the first housing 311 in the length direction L. In this case, additional sealing plates can be provided at both ends of the second housing 312 in the length direction L to define a heat exchange cavity 316 within the second housing 312.

[0029] In this embodiment, the connection between the second housing 312 and the first housing 311 is located near the top edge of the liquid-filled tube bundle 322, so that the second housing 312 can precisely confine the heat exchange tube bundle 320 within the heat exchange cavity 316. This allows for minimizing the volume of the heat exchange cavity 316 while maintaining a fixed number of heat exchange tubes, or ensuring a sufficient number of heat exchange tubes and effective gas-liquid separation while maintaining a fixed volume of the cavity 308. As a more specific example, the bottom left and right edges of the second housing 312 each have outwardly folded edges 331, which connect to the first housing 311. Each edge 331 extends outward and downward from the bottom edge of the second housing 312 to the first housing 311, effectively blocking the gaseous refrigerant evaporating from the liquid-filled tube bundle 322. In some embodiments, one or more return holes (not shown in the figure) are also provided on the folded edge 331 to allow the liquid accumulated in the gas-liquid separation chamber after gas-liquid separation to return to the heat exchange chamber 316 and be evaporated into gas by the full liquid tube bundle 322.

[0030] The falling film evaporator 100 also includes a first-stage demister 318 and a second-stage demister 319. In various embodiments of this application, demistering refers to removing liquid droplets or the like entrained in the gas. The gaseous refrigerant evaporated in the heat exchange chamber 316 can sequentially flow through the first-stage demister 318 and the second-stage demister 319 to remove liquid droplets (i.e., demister) from the gaseous refrigerant before being discharged from the falling film evaporator 100 through the evaporator outlet 102.

[0031] The first-stage demister 318 is located on the flow path of the refrigerant from the heat exchange chamber 316 to the gas-liquid separation chamber 317 to perform preliminary demisting. In some embodiments, the first-stage demister 318 is located near the connection between the heat exchange chamber 316 and the gas-liquid separation chamber 317. This arrangement allows for the thorough processing of all gaseous refrigerant after evaporation through the falling film tube bundle 321 and the flooded liquid tube bundle 322, while also reducing the liquid content in the gaseous refrigerant flowing in the gas-liquid separation chamber 317. In some more specific embodiments, the first-stage demister 318 includes several windows 336 disposed on the second housing 312, which form the first-stage demister. When the gaseous refrigerant flows through the first-stage demister 318, due to the difference in specific gravity between gas and liquid, if the gaseous refrigerant is blocked by the second housing 312, the gas in the gaseous refrigerant can be deflected after being blocked and flow back through the window 336, while the liquid droplets entrained in the gaseous refrigerant can be at least partially blocked and drip back into the heat exchange chamber 316, where they will be evaporated again by the liquid-filled tube bundle 322. The arrangement and structure of the windows 336 in the first-stage demister 318 in this embodiment are the same as those of the windows 536 shown in Figure 5, and will be described in detail in Figure 5.

[0032] The second-stage demister 319 is located on the flow path of the refrigerant from the gas-liquid separation chamber 317 to the evaporator outlet 102 to further demister. In some embodiments, the second-stage demister 319 is located near the evaporator outlet 102. In some more specific embodiments, the second-stage demister 319 is located above the second housing 312 and connected to the left and right sides of the top of the first housing 311. This arrangement maximizes the flow distance of the gaseous refrigerant in the height direction H in the gas-liquid separation chamber 317, thereby reducing the liquid content of the gaseous refrigerant flowing through the second-stage demister 319. In some more specific embodiments, the second-stage demister 319 includes a filter screen 329. When the gaseous refrigerant flows through the filter screen 329 of the second-stage demister 319, the gas in the gaseous refrigerant can pass through the filter screen 329, while the liquid droplets mixed in the gaseous refrigerant will adhere to the filter screen 329. After reaching a certain amount, they fall back into the gas-liquid separation chamber 317. Part of the liquid flows along the second housing 312 and returns to the heat exchange chamber 316 through the window 336. The other part of the liquid accumulates at the bottom of the gas-liquid separation chamber 317 and returns to the heat exchange chamber 316 through the liquid return hole on the folded edge 331, where it is evaporated again by the full liquid tube bundle 322.

[0033] The cavity 308 also includes a distributor 313. A pipe from the evaporator inlet 101 extends into the housing 203 and is in fluid communication with the distributor 313. The distributor 313 is used to uniformly distribute the gas-liquid two-phase refrigerant entering the cavity 308 from the evaporator inlet 101 to the heat exchange tube bundle 320. In this embodiment, the distributor 313 is connected to the tube sheets 205 at both ends of the housing 203 in the length direction L, is located above the falling film tube bundle 321 in the height direction H, and covers the width range of the falling film tube bundle 321 in the width direction W. In this embodiment, the distributor 313 includes an orifice plate 351, a distributor housing 352, and a distribution element 353, the orifice plate 351 and the distributor housing 352 defining a distribution cavity 354. The orifice plate 351 has several holes (not shown in the figure) aligned with and penetrating the falling film tube bundles 321, for distributing the refrigerant above the orifice plate 351 to the respective falling film tube bundles 321 below the orifice plate 351. The housing of the distribution cavity 354 is an arc-shaped strip, with its two ends in the length direction L connected to the tube sheet 205, and its two ends in the width direction W connected to the two end edges of the orifice plate 351. The distributor 353 is located in the distribution cavity 354 and communicates with the evaporator inlet 101 for distributing the gas-liquid two-phase refrigerant above the orifice plate 351. In this embodiment, the second housing 312 is formed by extending downward in an arc shape from the edge where the distributor housing 352 connects to the orifice plate 351. The filter screen 329 is located above the distributor housing 352.

[0034] Thus, the refrigerant entering the falling film evaporator 100 from the evaporator inlet 101 first exchanges heat with the hot water flowing inside the heat exchange tube bundle 320 in the heat exchange chamber 316 to evaporate into gaseous refrigerant. Then, it flows through the first-stage demister 318 for preliminary demisting, enters the gas-liquid separation chamber 317 for further demisting, and finally flows through the second-stage demister 319 for further demisting before being discharged from the evaporator outlet 102.

[0035] In the embodiments of this application, by setting a first-stage demister 318 and a second-stage demister 319 to remove liquid droplets entrained in the gaseous refrigerant, the gas-liquid separation chamber 317 no longer needs to perform, or only needs to perform, a small amount of gas-liquid separation or demistering. Therefore, compared with the existing falling film evaporator 100, with the same volume of cavity 308, the gas-liquid separation chamber 317 does not need to be set to a larger size to achieve sufficient demistering effect. Correspondingly, the heat exchange chamber 316 can be set to have a larger size to accommodate more heat exchange tube bundles 320, thereby increasing the heat exchange capacity of the falling film evaporator 100. And with the same heat exchange capacity, the falling film evaporator 100 can be designed to have a smaller size to meet more environmental requirements.

[0036] Furthermore, compared to evaporators where the filter screen 329 is connected to the top of the baffle 315 or the outside of the distributor housing 352, in the embodiments of this application, the gaseous refrigerant flowing in the gas-liquid separation chamber 317 travels a greater distance in the height direction H, which is beneficial for more complete separation of liquid droplets in the gaseous refrigerant. Moreover, the wider filter screen 329 results in a lower flow velocity of the gaseous refrigerant as it flows through the filter screen 329, thus reducing the pressure drop generated when the gaseous refrigerant flows through the filter screen 329, which is advantageous for the performance of the falling film evaporator 100.

[0037] Figure 4 A schematic structural diagram of the axial section of a falling film evaporator 400 according to another embodiment of this application is shown to illustrate the internal structure of the falling film evaporator 400. For example... Figure 4 As shown, the structure of the falling film evaporator 400 is similar to... Figure 3The falling film evaporator 100 shown has a generally similar structure. The housing 403 of the falling film evaporator 400 also includes a first housing 411 and a second housing 412, with the second housing 412 connected inside the first housing 411. The second housing 412 defines a heat exchange chamber 416, and the first housing 411 and the second housing 412 define a gas-liquid separation chamber 417. A heat exchange tube bundle 320 is disposed in the heat exchange chamber 416 to evaporate the refrigerant into a gaseous refrigerant. The evaporated gaseous refrigerant flows in the gas-liquid separation chamber 417 for gas-liquid separation. The falling film evaporator 400 also includes a first-stage demister 418 and a second-stage demister 419. The first-stage demister 418 is located on the flow path of the refrigerant from the heat exchange chamber 416 to the gas-liquid separation chamber 417, and the second-stage demister 419 is located on the flow path of the refrigerant from the gas-liquid separation chamber 417 to the evaporator outlet 102. The second-stage demisting device 419 includes a filter 329 located above the second housing 412.

[0038] Unlike the falling film evaporator 100, in this embodiment, the first-stage demister 418 no longer includes the window 336, but instead includes a superheated tube bundle 423. The tubes of the superheated tube bundle 423 are used to circulate a heat exchange medium, such as hot water. By allowing the evaporated refrigerant to flow through the superheated tube bundle 423, liquid droplets entrained in the gaseous refrigerant can be initially removed. Specifically, in this embodiment, the two sides of the second housing 412 in the width direction W are no longer connected to the inner side of the bottom of the first housing 411, but instead form an open opening 426 between them. The opening 426 connects the heat exchange chamber 416 and the gas-liquid separation chamber 417. The superheated tube bundle 423 is disposed in the opening 426. In this embodiment, the falling film evaporator 400 no longer includes a pair of baffles located on the outer sides of the falling film tube bundle 321, but instead consists of rows of superheated tube bundles 423 respectively disposed on the outer sides of the falling film tube bundle 321. In some embodiments, a pair of baffles can still be provided, which can correspondingly reduce the number of heat exchange tubes in the superheated tube bundle.

[0039] In this embodiment, the superheated tube bundle 423 of the first-stage demister 418 in the falling film evaporator 400 uses a different gas-liquid separation principle compared to the window 336 of the first-stage demister 318 in the falling film evaporator 100. Specifically, the window 336 demisters by blocking and deflecting the flow, while the superheated tube bundle 423 demisters by reheating and evaporating the liquid refrigerant. Therefore, compared to the first-stage demister 318, the first-stage demister 418 reduces refrigerant pressure loss.

[0040] Figure 5A and Figure 5B The structure of a falling film evaporator 500 according to another embodiment of this application is shown, wherein Figure 5AThis is a schematic diagram of the axial section of a 500 falling film evaporator. Figure 5B This is a schematic diagram of the radial cross-section of a falling film evaporator 500. Figure 5A and Figure 5B As shown, the first housing 511 of the falling film evaporator 500 is disposed above the second housing 512. In this embodiment, the second housing 512 is cylindrical, the first housing 511 is partially cylindrical, and the first housing 511 is connected to the outer sides of the top of the second housing 512 on both sides in the width direction W. The first housing 511 and the second housing 512 have approximately equal diameters. A heat exchange chamber 516 is defined within the second housing 512, and a gas-liquid separation chamber 517 is defined between the first housing 511 and the second housing 512. A heat exchange tube bundle 320 is disposed in the heat exchange chamber 516 to evaporate the refrigerant into a gaseous refrigerant. The evaporated gaseous refrigerant flows in the gas-liquid separation chamber 517 for gas-liquid separation.

[0041] The falling film evaporator 500 also includes a first-stage demister 518 and a second-stage demister 519. The first-stage demister 518 is located on the flow path of the refrigerant from the heat exchange chamber 516 to the gas-liquid separation chamber 517, and the second-stage demister 519 is located on the flow path of the refrigerant from the gas-liquid separation chamber 517 to the evaporator outlet 102. Similar to the falling film evaporator 100, the first-stage demister 518 also includes several windows 536 disposed on the second housing 512, which fluidly communicate with the heat exchange chamber 516 and the gas-liquid separation chamber 517. When the gaseous refrigerant flows through the first-stage demister 518, the gas in the gaseous refrigerant can flow through the windows 536, while the liquid droplets entrained in the gaseous refrigerant can be at least partially blocked by the second housing 512 and drip back into the heat exchange chamber 516 for re-evaporation. The second-stage demisting device 519 also includes a filter 329 located above the second housing 512.

[0042] In this embodiment, several windows 536 are arranged side-by-side approximately along the length direction L. The evaporator outlet 102 is located at the end of the first housing 511 along the length direction L. Therefore, the refrigerant flowing from the heat exchange chamber 516 to the gas-liquid separation chamber 517 and passing through the various windows 536 arranged along the length direction L travels different distances in the gas-liquid separation chamber 517. The refrigerant flowing closer to the window 536 of the evaporator outlet 102 has a shorter flow distance in the gas-liquid separation chamber 517, thus requiring the first-stage demisting device 518 to provide a better demisting effect. In this embodiment, the windows 536 are configured such that, along the length direction L towards the evaporator outlet 102, the size of several windows 536 gradually decreases, and the spacing between several windows 536 gradually increases, enabling the windows 536 closer to the evaporator outlet 102 to have a better demisting effect. The arrangement of several windows 336 in the first-stage demister 318 of the falling film evaporator 100 is the same as the arrangement of several windows 536.

[0043] In this embodiment, compared to the falling film evaporator 100, the second shell of the falling film evaporator 500 is no longer disposed inside the first shell. When the length and width of the falling film evaporator 500 are approximately the same as those of the falling film evaporator 100, the height of the falling film evaporator 500 is greater than that of the falling film evaporator 100. Furthermore, since the first shell 511 is disposed above the second shell 512 rather than on its outer side, the width of the heat exchange chamber 516 of the falling film evaporator 500 is greater than the width of the heat exchange chamber 316 of the falling film evaporator 100, allowing for more heat exchange tubes to be disposed in the heat exchange chamber 516 to increase the heat exchange capacity of the falling film evaporator 500. Also, since the gas-liquid separation chamber 517 is disposed above the heat exchange chamber 516 rather than on its outer side, the gas-liquid separation chamber 517 can achieve a greater height and width, making its height and width greater than those of the gas-liquid separation chamber 317. As a result, the refrigerant travels a longer distance in the gas-liquid separation chamber 517, leading to better gas-liquid separation. Furthermore, the width of the gas-liquid separation chamber 517 allows the refrigerant to flow at a lower velocity through the second-stage demister 519, resulting in a lower pressure drop or pressure loss.

[0044] Figure 6 A schematic structural diagram of the axial section of a falling film evaporator 600 according to another embodiment of this application is shown to illustrate the internal structure of the falling film evaporator 600. Figure 6As shown, the structure of the falling film evaporator 600 is largely the same as that of the falling film evaporator 500, and will not be described again here. The difference lies in the specific structure of the second-stage demister 619 in the falling film evaporator 600, which differs from the specific structure of the second-stage demister 519 in the falling film evaporator 500. Specifically, the second-stage demister 619 includes a regenerator 641, in which a regenerator tube bundle 642 extending along the length direction L is provided. The tubes of the regenerator tube bundle 642 are used to circulate a high-temperature medium, so that the gaseous refrigerant in the gas-liquid separation chamber 617 can flow through the regenerator tube bundle 642 in the regenerator 641, thereby further removing liquid droplets entrained in the gaseous refrigerant. In some embodiments, the regenerator tube bundle 642 is used to fluidly communicate with the high-pressure side of the refrigeration system 190. In this embodiment, the tubes of the regenerating tube bundle 642 are used to circulate high-temperature liquid refrigerant from the condenser 191, and the refrigerant flowing through the regenerating tube bundle 642 returns to the throttling device 192.

[0045] In this embodiment, the gaseous refrigerant in the gas-liquid separation chamber 617 absorbs heat from the high-temperature liquid refrigerant in the regenerating tube bundle 642 and vaporizes, causing the entrained droplets to vaporize into gas. Simultaneously, the high-temperature liquid refrigerant in the regenerating tube bundle 642 releases heat to the gaseous refrigerant in the gas-liquid separation chamber 617, thereby achieving a subcooling effect. Therefore, the refrigeration system using the falling film evaporator 600, including the second-stage demister 619, can achieve a higher system cycle efficiency (COP) compared to other falling film evaporators that do not use the second-stage demister 619.

[0046] In existing falling film evaporators, to prevent the compressor from drawing in liquid, sufficient flow distance is required for the gaseous refrigerant in the gas-liquid separation chamber to completely demister. This results in either a larger size for the falling film evaporator, thus increasing its footprint, or a reduction in the heat exchange tube bundle and heat exchange capacity.

[0047] In various embodiments of this application, compared to existing falling film evaporators, the embodiments of falling film evaporators 100 and 400 can increase the size of the heat exchange chamber while maintaining the existing size of the evaporator, thereby increasing the number of heat exchange tubes and improving the heat exchange capacity of the evaporator. The embodiments of falling film evaporators 500 and 600 can increase the height of the evaporator without increasing its width and length (i.e., without increasing the floor space of the evaporator), thereby increasing the number of heat exchange tube bundles and improving the heat exchange capacity of the evaporator. Furthermore, while maintaining the size of the gas-liquid separation chamber, the demisting effect is improved. In addition, the embodiments of this application also reduce the velocity of the gaseous refrigerant flowing through the second-stage demisting device by increasing the width of the gas-liquid separation chamber, thereby reducing the pressure drop of the gaseous refrigerant.

[0048] While some examples of falling film evaporators have been given above, those skilled in the art will understand that the structures of the shell, the first-stage demister, and the second-stage demister in these examples can be combined and used according to specific needs. For example, the structure of the second-stage demister in any of the falling film evaporators 100, 400, and 500 can be replaced with the structure of the second-stage demister 619.

[0049] In the falling film evaporator of this application, liquid droplets in the gaseous refrigerant are removed by reasonably setting a two-stage demister. This means that the gas-liquid separation chamber no longer needs to perform or only needs to perform a small amount of gas-liquid separation function. Therefore, the gas-liquid separation chamber does not need to be set to a large size to achieve the effect of fully removing liquid droplets in the gaseous refrigerant.

[0050] Furthermore, the falling film evaporator of this application, by setting two shells, can form a separated heat exchange chamber and a gas-liquid separation chamber within the falling film evaporator, each chamber capable of functioning independently. With the overall volume of the falling film evaporator remaining constant, the volume of the heat exchange chamber is increased by reducing the volume of the gas-liquid separation chamber, thereby accommodating more heat exchange tubes. In some embodiments, the volume of the gas-liquid separation chamber can also be further increased to achieve better demisting effects.

[0051] Although this application will be described with reference to the specific embodiments shown in the accompanying drawings, it should be understood that the evaporator of this application can be varied in many ways without departing from the spirit, scope, and context of the teachings of this application. Those skilled in the art will also recognize that different ways of modifying the structural details of the embodiments disclosed in this application fall within the spirit and scope of the invention and the claims.

Claims

1. A falling film evaporator, characterized in that include: A housing defining a cavity having a length direction and a width direction, the cavity including a heat exchange cavity and a gas-liquid separation cavity in communication, the housing having an evaporator inlet and an evaporator outlet, wherein the heat exchange cavity is in fluid communication with the evaporator inlet, and the gas-liquid separation cavity is in fluid communication with the evaporator outlet; A heat exchange tube bundle, which extends along the length direction and is disposed in the heat exchange cavity, the heat exchange tube bundle including a plurality of falling film tube bundles; The first-stage demister is located on the flow path of the refrigerant from the heat exchange chamber to the gas-liquid separation chamber, and is located on the outside of the plurality of falling film tube bundles in the width direction. as well as The second-stage demister is located on the flow path of the refrigerant from the gas-liquid separation chamber to the evaporator outlet. The falling film evaporator is configured such that the refrigerant entering the falling film evaporator from the evaporator inlet first exchanges heat with the heat exchange medium in the heat exchange chamber, then flows through the first-stage demister and enters the gas-liquid separation chamber, and finally flows through the second-stage demister and is discharged from the evaporator outlet.

2. The falling film evaporator according to claim 1, characterized in that: The housing includes a first housing and a second housing, which are connected to each other. The heat exchange cavity is defined within the second housing, and the gas-liquid separation cavity is defined between the first housing and the second housing. The second-stage demisting device is located above the second housing.

3. The falling film evaporator according to claim 2, characterized in that: The first-stage demister includes several windows, which are in fluid communication with the heat exchange chamber and the gas-liquid separation chamber. Specifically, a pair of baffles are provided on the outer sides of the plurality of falling film tube bundles in the width direction. The second housing portion is separated from the baffle in the width direction, and the plurality of windows are disposed on the second housing portion and above the lower edge of the baffle.

4. The falling film evaporator according to claim 3, characterized in that: The plurality of windows are arranged side by side along the length direction, and the size of the plurality of windows gradually decreases along the length direction toward the evaporator outlet, while the spacing between the plurality of windows gradually increases.

5. The falling film evaporator according to claim 2, characterized in that: The first-stage demister includes a superheated tube bundle; The second housing includes an opening that is in fluid communication with the heat exchange chamber and the gas-liquid separation chamber, and the superheated tube bundle is disposed in the opening.

6. The falling film evaporator according to claim 2, characterized in that: The second-stage demisting device includes a filter or a regenerator, wherein the regenerator includes several regenerator tube bundles, and the tube bundles are used to circulate liquid refrigerant from the condenser.

7. The falling film evaporator according to claim 2, characterized in that: The falling film evaporator also includes a distributor in fluid communication with the evaporator inlet, the distributor being configured to distribute refrigerant entering the falling film evaporator from the evaporator inlet to the heat exchange tube bundle.

8. The falling film evaporator according to claim 2, characterized in that: The second housing is disposed inside the first housing, wherein the second housing is connected to the inner side of the first housing on both sides in the width direction.

9. The falling film evaporator according to claim 2, characterized in that: The first housing is connected above the second housing, wherein the first housing is connected to the outer side of the second housing on both sides in the width direction.

10. A refrigeration system, characterized in that: It includes a compressor, a condenser, a throttling device, and a falling film evaporator according to any one of claims 1-9, all located in the refrigerant circuit.

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