Evaporator

Abstract

The application provides an evaporator, comprising: a shell; a falling film tube bundle arranged in the cavity and in columns, the falling film tube bundle comprising a plurality of heat exchange tubes, the centers of the heat exchange tubes in each column are arranged along the height direction, and the centers of the adjacent two heat exchange tubes in adjacent columns are arranged staggered in the width direction of the cavity; wherein the falling film tube bundle is configured such that, among the adjacent four heat exchange tubes in the adjacent two columns, the minimum distance between the outer surfaces of the heat exchange tubes of at least two different columns is greater than the minimum distance between the outer surfaces of the two heat exchange tubes in the same column. In the application, by increasing the space of the refrigerant channel in the width direction W, the flow rate of the gas flowing between the corresponding heat exchange tubes is reduced, thereby reducing the gas phase Reynolds number Re v and improving the heat exchange efficiency of the evaporator. film and improving the heat exchange efficiency of the evaporator.

Description

Technical Field

[0001] This application relates to an evaporator, and more particularly to an evaporator with high heat exchange efficiency. Background Technology

[0002] Traditional refrigeration systems consist of an evaporator, condenser, throttling device, and compressor. When the low-temperature liquid refrigerant passes through the evaporator, it exchanges heat with the surrounding environment, absorbing heat and thus lowering the ambient temperature, achieving a refrigeration effect. The surrounding environment can be air or cooling water. After heat exchange, the liquid refrigerant vaporizes into a gaseous refrigerant which then enters the compressor. The heat exchange efficiency of the evaporator is affected by many factors. Summary of the Invention

[0003] At least one objective of this application in its first aspect is to provide an evaporator with high heat exchange efficiency. The evaporator includes: a shell having a cavity having a length direction, a width direction, and a height direction; a falling film tube bundle disposed within the cavity and arranged in rows, the falling film tube bundle including a plurality of heat exchange tubes, each heat exchange tube extending along the length direction of the cavity, the center of the heat exchange tubes in each row arranged along the height direction, and the centers of adjacent heat exchange tubes in adjacent rows staggered in the width direction of the cavity; wherein the falling film tube bundle is configured such that, in two adjacent rows of four heat exchange tubes, the minimum distance between the outer surfaces of at least two heat exchange tubes from different rows is greater than the minimum distance between the outer surfaces of two heat exchange tubes in the same row.

[0004] According to the first aspect above, the spacing between the outer surfaces of at least two heat exchange tubes from different columns in two adjacent columns is set such that the flow velocity of the gas flowing through the two adjacent columns of heat exchange tubes is reduced, thereby improving the heat exchange efficiency of the evaporator.

[0005] According to the first aspect above, each heat exchange tube in the falling film tube bundle has the same tube diameter, and the ratio of the center-to-center distance between two adjacent heat exchange tubes in an adjacent column in the width direction of the cavity to the center-to-center distance between two adjacent heat exchange tubes in the height direction of the cavity in each column satisfies the following condition.

[0006] According to the first aspect above, the falling film tube bundle includes several first heat exchange tubes with larger diameters and several second heat exchange tubes with smaller diameters; in the column of the falling film tube bundle, the first heat exchange tubes and the second heat exchange tubes are arranged alternately.

[0007] According to the first aspect above, the falling film tube bundle includes several first heat exchange tubes with a larger diameter and several second heat exchange tubes with a smaller diameter. The first heat exchange tubes are arranged in rows, and the second heat exchange tubes are arranged in rows; wherein the rows of the first heat exchange tubes and the rows of the second heat exchange tubes are arranged alternately.

[0008] According to the first aspect above, the distance between the centers of adjacent first heat exchange tubes and second heat exchange tubes in two adjacent columns of heat exchange tubes in the width direction of the cavity is not less than the larger diameter of the first heat exchange tube.

[0009] According to the first aspect above, the larger diameter of the first heat exchange tube is 25.4 mm; and the smaller diameter of the second heat exchange tube is 19.05 mm.

[0010] According to the first aspect above, the evaporator further includes: a first baffle and a second baffle, the first baffle and the second baffle being respectively disposed on the outer side of the falling film tube bundle in the width direction of the cavity; wherein, the first baffle and the second baffle are each provided with a plurality of windows, the plurality of windows being arranged along the length direction of the cavity, and the plurality of windows being disposed on the outer side of the middle part of the falling film tube bundle in the height direction of the cavity.

[0011] According to the first aspect above, each of the first baffle and the second baffle has a liquid-blocking plate extending along the length direction of the cavity on the outer side of the window, wherein the top of the liquid-blocking plate is connected to the corresponding first baffle and the second baffle, and the liquid-blocking plate is spaced a certain distance from the window.

[0012] At least one objective of the second aspect of this application is to provide a refrigeration system comprising: a compressor, a condenser, a throttling device, and an evaporator disposed in a refrigerant circuit, wherein the evaporator is as described in any of the first aspects. Attached Figure Description

[0013] Figure 1 This is a schematic block diagram of a refrigeration system;

[0014] Figure 2 yes Figure 1 A three-dimensional view of the evaporator.

[0015] Figure 3A yes Figure 2 A radial section view of one embodiment of an evaporator;

[0016] Figure 3B yes Figure 3A A magnified view of four adjacent heat exchange tubes in a medium falling film tube bundle;

[0017] Figure 3C yes Figure 3A A comparison diagram of the heat transfer coefficients of the falling film tube bundle of the evaporator in the illustrated embodiment and the theoretical values ​​of a single heat exchange tube in an ideal falling film tube bundle.

[0018] Figure 4A yes Figure 2 A radial section view of another embodiment of the evaporator;

[0019] Figure 4B yes Figure 4A A magnified view of four adjacent heat exchange tubes in a medium falling film tube bundle;

[0020] Figure 4C yes Figure 4A A comparison diagram of the heat transfer coefficients of the falling film tube bundle of the evaporator in the illustrated embodiment and the theoretical values ​​of a single heat exchange tube in an ideal falling film tube bundle.

[0021] Figure 5A yes Figure 2 A radial section view of another embodiment of the evaporator;

[0022] Figure 5B yes Figure 5A A magnified view of four adjacent heat exchange tubes in a medium falling film tube bundle;

[0023] Figure 5C yes Figure 5A A comparison diagram of the heat transfer coefficients of the falling film tube bundle of the evaporator in the illustrated embodiment and the theoretical values ​​of a single heat exchange tube in an ideal falling film tube bundle.

[0024] Figure 6A yes Figure 2 A radial section view of another embodiment of the evaporator;

[0025] Figure 6B yes Figure 6A A schematic diagram of the structure of the first baffle in the middle;

[0026] Figure 6C yes Figure 6A A comparison diagram of the heat transfer coefficients of the falling film tube bundle of the evaporator in the illustrated embodiment and the theoretical values ​​of a single heat exchange tube in an ideal falling film tube bundle. Detailed Implementation

[0027] Various specific embodiments of this application 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," "inner," "outer," "top," "bottom," "positive," "negative," "proximal," "farthest," "lateral," and "longitudinal," are used herein to describe various exemplary structural parts and elements, these terms are used only for illustrative purposes and are determined based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this application can be arranged in different orientations, these terms indicating direction are illustrative only and should not be considered limiting.

[0028] Ordinal numbers such as “first” and “second” used in this application are for distinction and identification only and have no other meaning. Unless otherwise specified, they do not indicate a specific order or a specific relationship. For example, the term “first component” does not imply the existence of “second component”, nor does the term “second component” imply the existence of “first component”.

[0029] Figure 1 This is a schematic block diagram of the refrigeration system 190. (For example...) Figure 1 As shown, the refrigeration system 190 includes a compressor 193, a condenser 191, a throttling device 192, and an evaporator 100, which are connected by pipes to form a refrigerant circulation loop, and the loop is filled with refrigerant. Figure 1 As indicated by the arrows, the refrigerant flows sequentially through compressor 193, condenser 191, throttling device 192, and evaporator 100 before re-entering compressor 193. During the refrigeration process, throttling device 192 restricts the pressure of the high-pressure liquid refrigerant from condenser 191, reducing its pressure. The low-pressure refrigerant exchanges heat with the object being cooled in evaporator 100, absorbing heat and vaporizing. The resulting refrigerant vapor is drawn into compressor 193, compressed, and discharged at high pressure. The high-temperature, high-pressure gaseous refrigerant discharged from compressor 193 exchanges heat with the surrounding medium in condenser 191, releasing heat and condensing into liquid refrigerant. The high-temperature liquid refrigerant then flows through throttling device 192 again, reducing its pressure. This cycle repeats continuously, producing a continuous refrigeration effect.

[0030] Figure 2 yes Figure 1 A perspective view of the evaporator 100, as shown below. Figure 2As shown, the evaporator 100 has a shell 203, which includes a cylindrical body 204 and a pair of tube sheets 205. The cylindrical body 204 is open at both ends, and the pair of tube sheets 205 are respectively placed at both ends of the cylindrical body 204 to seal the openings at both ends of the cylindrical body 204. The cylindrical body 204 and the pair of tube sheets 205 form a cavity 310 (see...). Figure 3A The cavity 310 is used to house the heat exchange tubes. An inlet pipe 208 and an outlet pipe 207 are connected to the tube sheet 205. See also... Figure 2 As shown, the evaporator 100 has a height direction H, a length direction L, and a width direction W. The height, length, and width directions of the cavity 310 are aligned with the directions of the evaporator 100. A refrigerant inlet 101 and a refrigerant outlet 102 are provided on the cylindrical body 204, both located at the upper part of the evaporator 100 in the height direction H, and offset in the length and / or radial directions of the cylindrical body 204. Liquid refrigerant or a gas-liquid mixture in the refrigeration system 190 enters the evaporator 130 through the refrigerant inlet 101, absorbs heat in the evaporator 130, and becomes gaseous refrigerant, which is then discharged through the refrigerant outlet 102.

[0031] Figures 3A-3C A first embodiment of the evaporator of this application is shown. Figure 3A yes Figure 2 A radial cross-sectional schematic diagram of the first embodiment of the evaporator. Figure 3B yes Figure 3A A magnified view of four adjacent heat exchange tubes in a falling film tube bundle. Figure 3C This is a comparison chart of theoretical values ​​for heat transfer coefficients. For example... Figure 3A and Figure 3B As shown, the interior of the housing 203 forms a cavity 310, within which a falling film tube bundle 315, a full-fill tube bundle 316, a distribution device 340, and a demister 341 are disposed. Figure 2 and Figure 3A As shown, the refrigerant inlet 101 is located at the middle of the evaporator 100 in both the length and width directions to facilitate uniform refrigerant distribution. The refrigerant outlet 102 and the refrigerant inlet 101 are staggered in the length and / or radial directions. The distribution device 340 is disposed above the falling film tube bundle 315 and communicates with the refrigerant inlet 101 to uniformly distribute the liquid refrigerant received from the throttling device 192 from the refrigerant inlet 101 into the falling film tube bundle 315. The demister 341 is connected below the refrigerant outlet 102, and the outlet of the gas obtained from the evaporation of the falling film tube bundle 315 and the flooded tube bundle 316 is disposed below the demister 341 so that the demister 341 can prevent liquid droplets entrained in the evaporated gas refrigerant from being discharged from the refrigerant outlet 102.

[0032] The falling film tube bundle 315 is generally located in the upper middle part of the cavity 310, and the full liquid tube bundle 316 is located at the bottom of the cavity 310, with a certain distance between the bottom of the full liquid tube bundle 316 and the bottom of the falling film tube bundle 315. Both the falling film tube bundle 315 and the full liquid tube bundle 316 are heat exchange tube bundles formed by multiple heat exchange tubes 320 arranged sequentially. Each heat exchange tube 320 has the same diameter D0 and extends along the length L of the cavity 305. As an example, the diameter D0 of the heat exchange tube 320 is 1 inch, or 25.4 mm. A fluid channel is formed inside each heat exchange tube for communication with the inlet pipe 208 and the outlet pipe 207 to allow the flow of water or other media. The gap between each heat exchange tube 320 and an adjacent heat exchange tube 320 forms a refrigerant channel for the flow of refrigerant. The medium in the fluid channel and the refrigerant in the refrigerant channel exchange heat through the tube walls of the heat exchange tubes.

[0033] The heat exchange tubes 320 in the falling film tube bundle 315 are arranged in rows, with adjacent rows spaced equidistantly. The centers of the heat exchange tubes 320 in each row are evenly spaced along the height direction H. However, in the width direction W, the centers of adjacent heat exchange tubes 320 in adjacent rows are staggered. Within each row, the centers of adjacent heat exchange tubes 320 in adjacent rows have the same spacing. In other words, in the width direction W, the centers of two adjacent heat exchange tubes 320 are not on the same horizontal line, i.e., not at the same height. But in the height direction H, the centers of two adjacent heat exchange tubes 320 are on the same vertical line, i.e., at the same width. This arrangement of the heat exchange tubes is because, during the falling film evaporation process, the liquid refrigerant to be evaporated flows from top to bottom, forming a liquid film on the outer surface of the tube wall of each heat exchange tube 320, exchanging heat with the medium inside the heat exchange tube 320. Arranging the heat exchange tubes 320 in rows, and staggering adjacent heat exchange tubes 320 in the width direction instead of arranging them side by side, is to avoid the refrigerant channel formed between adjacent rows of heat exchange tubes 320 having an extension direction inconsistent with the direction of gravity of the liquid refrigerant, which would prevent the formation of a liquid film on the lower row of heat exchange tubes. The tube arrangement method of this application allows unevaporated liquid refrigerant to continue flowing to the outer surface of the lower heat exchange tubes 320 to form a liquid film, thereby improving the evaporation efficiency of each heat exchange tube.

[0034] The heat exchange tubes 320 in the flooded tube bundle 316 are also arranged in rows and cover the bottom of the cavity 310. After heat exchange through the falling film tube bundle 315, a portion of the liquid refrigerant still fails to completely evaporate into gaseous refrigerant. This portion of liquid refrigerant will form a liquid surface at the bottom of the cavity 310 with a height greater than that of the flooded tube bundle 316. The heat exchange tubes 320 in the flooded tube bundle 316 are used to immerse this portion of liquid refrigerant to further evaporate the liquid refrigerant into gaseous refrigerant.

[0035] The evaporator 100 also includes a first baffle 331 and a second baffle 332, which are respectively disposed on the outer side of the falling film tube bundle 315 in the width direction W and extend in the length direction L. The first baffle 331 and the second baffle 332 are used to guide the refrigerant to flow from top to bottom through each heat exchange tube in the falling film tube bundle 315, preventing the liquid refrigerant from flowing to the outer side of the falling film tube bundle 315. The gaseous refrigerant obtained from evaporation flows along the first baffle 331 and the second baffle 332 and is discharged from the bottom of the first baffle 331 and the second baffle 332. That is, the outlet of the gaseous refrigerant obtained from evaporation in the falling film tube bundle 315 is approximately located at the bottom edge of the first baffle 331 and the second baffle 332.

[0036] Figure 3B Show Figure 3A In the falling film tube bundle 315, there is an enlarged structure of four adjacent heat exchange tubes 320a, 320b, 320c, and 320d in two adjacent columns. Those skilled in the art will understand that because the heat exchange tubes 320 in the falling film tube bundle 315 are uniformly arranged, these four heat exchange tubes can be any four adjacent heat exchange tubes in two adjacent columns, adjacent to each other in pairs, and the centers of three adjacent heat exchange tubes form two acute-angled triangles. Figure 3B As shown, heat exchange tubes 320a and 320b are in the same column, and heat exchange tubes 320c and 320d are in the same column. Heat exchange tubes 320a, 320b, and 320c are adjacent, their centers forming an acute-angled triangle. Heat exchange tubes 320b, 320c, and 320d are also adjacent, their centers forming an acute-angled triangle. In the height direction H, the centers of adjacent heat exchange tubes 320a and 320b in the same column have a distance H0 (hereinafter referred to as the vertical distance). In the width direction W, the centers of adjacent heat exchange tubes 320a and 320c in different columns have a distance W0 (hereinafter referred to as the horizontal distance). There is a minimum distance X0 between the outer surfaces of heat exchange tubes 320a and 320b. There is a minimum distance V0 between the outer surfaces of heat exchange tubes 320a and 320c. In this embodiment, V0 is greater than X0. And H0 and W0 satisfy the following relationship:

[0037] In some existing falling film tube bundles, the centers of three adjacent heat exchange tubes arranged in a row are generally arranged in an equilateral triangle shape. These heat exchange tubes have a horizontal spacing approximately equal to D0, and approximately... The vertical spacing. That is, the ratio of the horizontal spacing to the vertical spacing of these heat exchange tubes is approximately cos30°.

[0038] In a falling film evaporator, the gas-liquid two-phase refrigerant entering the evaporator from the refrigerant inlet is evenly distributed onto the surface of the heat exchange tubes at the top of the falling film tube bundle after being distributed by a distribution device, forming a liquid film for heat exchange. A portion of the liquid refrigerant is converted into gas after evaporation and heat exchange, while the remaining unevaporated liquid refrigerant drips onto the lower heat exchange tubes to continue evaporating. The flow rate of the liquid refrigerant flowing through the falling film tube bundle gradually decreases from the top to the bottom of the tube bundle, while the flow rate of the gaseous refrigerant gradually increases.

[0039] The applicant discovered through research that the heat transfer coefficient "h" of each heat exchange tube in the falling film tube bundle r "It can be fitted to a Gaussian distribution equation (1):"

[0040]

[0041] Where y0,A,w,xc are fitting constants, Re v Re is the gas phase Reynolds number. film Let h be the liquid film Reynolds number. From the Gaussian distribution equation (1), it can be seen that the heat transfer coefficient "h" r "With the gas phase Reynolds number Re" v With liquid film Reynolds number Re film The ratio increases and decreases. Among them, the gas phase Reynolds number Re v The liquid film Reynolds number is directly proportional to the inter-pipe flow velocity of the gaseous refrigerant. film The flow rate of the liquid refrigerant is also directly proportional to the flow rate of the gaseous refrigerant. The lower the flow rate of the gaseous refrigerant, the higher the gas phase Reynolds number. v The smaller the value, the lower the heat transfer coefficient "h". r "The larger the flow rate of the liquid refrigerant, the higher the liquid film Reynolds number Re." film The larger the value, the higher the heat transfer coefficient "h". r "Also bigger.

[0042] The flow velocity of the gaseous refrigerant is related to its flow rate and the flow area. Increasing the minimum spacing between the outer surfaces of the heat exchange tubes in different rows of the falling film tube bundle can reduce the gas velocity flowing between the corresponding heat exchange tubes at a given flow rate by increasing the space of the refrigerant channel in the width direction W, thereby improving the heat transfer coefficient. rHowever, when the horizontal spacing between heat exchange tubes increases, the number of falling film tubes that can be arranged in a cavity of a certain size decreases, leading to a decrease in the heat exchange capacity of the evaporator. Within a certain range, increasing the minimum spacing between the outer surfaces of the tube walls of the falling film tube bundle can improve the heat exchange efficiency of the evaporator, thereby increasing the heat exchange capacity. Alternatively, while maintaining the same heat exchange capacity, the number of heat exchange tubes can be reduced.

[0043] In this embodiment, the evaporator size is the same as in the prior art compared to existing falling film tube bundles, and the size of each heat exchange tube is also the same. This embodiment increases the minimum distance between the outer surfaces of the tube walls in different rows by maintaining the vertical spacing H0 between the centers of the heat exchange tubes and increasing the horizontal spacing W0 between the centers of the heat exchange tubes. Specifically, the falling film tube bundle 315 of this application increases the ratio of the horizontal spacing W0 to the vertical spacing H0 to (1~1.5)*cos30°. That is, the centers of three adjacent heat exchange tubes in the falling film tube bundle 315 of this application are no longer arranged in an equilateral triangle shape, but rather in an isosceles triangle shape with a vertex angle less than 60°. The increased ratio of the horizontal spacing W0 to the vertical spacing H0 will reduce the flow velocity of the gas flowing through two adjacent rows of heat exchange tubes 320, thereby improving the heat exchange efficiency of the evaporator 100.

[0044] Figure 3C A comparison chart is shown of the theoretical values ​​of the heat transfer coefficients of a single heat exchanger tube in the falling film tube bundle 315 of this embodiment, a conventional falling film tube bundle, an ideal falling film tube bundle, and an ideal flooded tube bundle, with the same number of heat exchanger tubes. The theoretical values ​​are obtained through the Gaussian distribution equation (1). Figure 3C In the diagram, the horizontal axis represents the number of heat exchange tubes in different rows from top to bottom, and the vertical axis represents the heat transfer coefficient. Lines 361 and 362 represent the heat transfer coefficients of a single heat exchange tube in an ideal falling film tube bundle and a flooded tube bundle, respectively. Curves 360 and 370 represent the heat transfer coefficients of a conventional falling film tube bundle and the falling film tube bundle 315 of this embodiment, respectively.

[0045] from Figure 3C As can be seen, under ideal conditions, the heat transfer coefficients of the heat exchange tubes in both the falling film tube bundle and the flooded tube bundle do not decrease with the increase in the number of rows. However, in existing falling film tube bundles, the heat transfer coefficient decreases rapidly with the increase in the number of rows, and even in the bottom rows of heat exchange tubes, the heat transfer efficiency will drop below the ideal heat transfer coefficient of the flooded tube bundle. In the falling film tube bundle of this embodiment, the heat transfer coefficient remains almost equivalent to that of the ideal falling film tube bundle. Even with a slight decrease in the bottom rows of heat exchange tubes, the heat transfer coefficient is still much higher than that of the ideal flooded tube bundle.

[0046] Figures 4A-4C A second embodiment of the evaporator of this application is shown. Figure 4A It shows Figure 2 A radial section view of the evaporator 400 in the second embodiment of the evaporator. Figure 4B yes Figure 4A A magnified view of four adjacent heat exchange tubes in a falling film tube bundle. Figure 4C This is a comparison chart of theoretical values ​​for heat transfer coefficients. For example... Figure 4A and Figure 4B As shown, similar to the first embodiment, the evaporator 400 also includes a falling film tube bundle 415 and a flooded tube bundle 416, each comprising several heat exchange tubes arranged in rows. The heat exchange tubes in the flooded tube bundle 416 and their arrangement are the same as in the first embodiment. However, the falling film tube bundle 415 differs from the first embodiment in that the heat exchange tubes no longer have the same diameter. Instead, it includes several first heat exchange tubes 421 with a larger diameter D1 and several second heat exchange tubes 422 with a smaller diameter D2. In each row of the falling film tube bundle 415, the first heat exchange tubes 421 and the second heat exchange tubes 422 are arranged alternately. That is, for any four adjacent heat exchange tubes in two adjacent rows, there must be two first heat exchange tubes 421 with larger diameters and two second heat exchange tubes 422 with smaller diameters. As an example, the larger diameter D1 of the first heat exchange tube 421 is equal to the diameter D0 of the heat exchange tube 320 in the first embodiment. In this embodiment, the diameter D1 of the larger-diameter first heat exchange tube 421 is 1 inch, or 25.4 mm, and the diameter D2 of the smaller-diameter second heat exchange tube 422 is 3 / 4 inch, or 19.05 mm. In the falling film tube bundle 415, the ratio of the number of the first heat exchange tube 421 to the number of the second heat exchange tube 422 is approximately 1:1.

[0047] Figure 4B The diagram shows an enlarged view of four adjacent heat exchange tubes 421a, 421b, 422a, and 422b in two adjacent columns. These heat exchange tubes are adjacent to each other in pairs, and the centers of three adjacent heat exchange tubes form two equilateral triangles. Figure 4BAs shown, heat exchange tubes 421a and 422a are in the same column, and heat exchange tubes 422b and 421b are in the same column. Furthermore, heat exchange tubes 421a, 422a, and 422b are adjacent, as are heat exchange tubes 421b, 422a, and 422b. In the height direction H, the centers of adjacent heat exchange tubes 421a and 422a in the same column have a vertical distance H1. In the width direction W, the centers of adjacent heat exchange tubes 421a and 422b in different columns have a horizontal distance W1. There is a minimum distance X1 between the outer surfaces of heat exchange tubes 421a and 422a, and between the outer surfaces of heat exchange tubes 421a and 422b. There is a minimum distance V1 between the outer surfaces of heat exchange tubes 422a and 422b. In this embodiment, V1 is greater than X1, and W1 ≥ D1.

[0048] Generally, the heat transfer coefficient of the second heat exchange tube 422 with a smaller diameter is greater than that of the first heat exchange tube 421 with a larger diameter, and the cost is lower. However, the heat transfer area is smaller, and the overall heat transfer capacity is not as good as that of the first heat exchange tube 421. In this embodiment, a portion of the first heat exchange tubes 421 with a larger diameter D1 are replaced with second heat exchange tubes 422 with a smaller diameter D2. On the one hand, by reducing the diameter of a portion of the heat exchange tubes, the minimum distance V1 of the outer surface is increased, thereby reducing the flow velocity of the gas flowing between the corresponding heat exchange tubes and thus improving the heat transfer efficiency of the evaporator. On the other hand, in the same column, for the first heat exchange tubes 421 below the second heat exchange tubes 422, since the heat transfer capacity of the second heat exchange tubes 422 is less than that of the first heat exchange tubes 421, the flow rate of liquid refrigerant on the lower row of first heat exchange tubes 421 increases. This can further increase the liquid film Reynolds number Re by increasing the flow rate of liquid refrigerant on the lower row of first heat exchange tubes 421. film This further improves the heat transfer coefficient "h" r ".

[0049] Even without increasing the horizontal spacing W0 between the centers of the heat exchange tubes, this increases the space for the refrigerant channels in the width direction W, thereby reducing the flow velocity of the gas passing between the corresponding heat exchange tubes. In this embodiment, the center-to-center spacing of each heat exchange tube remains unchanged compared to existing technologies where all heat exchange tubes are large-diameter. However, the space for the refrigerant channels between heat exchange tubes 421a and 422b, as well as between heat exchange tubes 422a and 422b, is increased. Therefore, the overall heat exchange efficiency of the evaporator in this embodiment can still be improved, and overall, the cost of the heat exchange tubes can be reduced.

[0050] It should be noted that in some other embodiments, in two adjacent columns, the centers of three adjacent heat exchange tubes 421a, 421b, 422a and 422b may not form two equilateral triangles, but rather form two isosceles triangles similar to the first embodiment, by increasing the horizontal spacing between adjacent heat exchange tubes in different columns.

[0051] Figure 4C A comparison chart shows the theoretical values ​​of the heat transfer coefficients of a single heat exchanger tube in the falling film tube bundle 415 of this embodiment, the second heat exchanger tube in the falling film tube bundle 415 of this embodiment, the ideal falling film tube bundle including the first heat exchanger tube, the ideal flooded tube bundle including the first heat exchanger tube, the ideal falling film tube bundle including the second heat exchanger tube, and the ideal flooded tube bundle including the second heat exchanger tube, all with the same number of heat exchanger tubes. The theoretical values ​​are obtained using the Gaussian distribution equation (1). Figure 4C In the diagram, the horizontal axis represents the number of heat exchange tubes in different rows from top to bottom, and the vertical axis represents the heat transfer coefficient. Lines 461, 462, 463, and 464 represent the heat transfer coefficients of a single heat exchange tube in an ideal falling film tube bundle including a first heat exchange tube, an ideal flooded tube bundle including a first heat exchange tube, an ideal falling film tube bundle including a second heat exchange tube, and an ideal flooded tube bundle including a second heat exchange tube, respectively. Curves 460 and 470 represent the heat transfer coefficients of the first and second heat exchange tubes in the falling film tube bundle 415 of this embodiment, respectively.

[0052] from Figure 4C As can be seen, under ideal conditions, the heat transfer coefficients of the falling film tube bundle and the flooded tube bundle, including the second heat exchange tube with a small diameter, are higher than those of the first heat exchange tube bundle and the flooded tube bundle, respectively, indicating that the small-diameter heat exchange tubes have a better heat transfer coefficient. Furthermore, the falling film tube bundle, including the second heat exchange tube with a small diameter, maintains a heat transfer coefficient almost equivalent to that under ideal conditions, and the heat transfer coefficient does not decrease significantly with the number of rows. The heat transfer coefficient of the falling film tube bundle, including the first heat exchange tube with a large diameter, is also consistently higher than that of the flooded tube bundle of the same diameter under ideal conditions.

[0053] Figures 5A-5C A third embodiment of the evaporator of this application is shown. Figure 5A Show Figure 2 A radial section view of the evaporator 500 in the third embodiment of the evaporator. Figure 5B yes Figure 4A A magnified view of four adjacent heat exchange tubes in a falling film tube bundle. Figure 5C This is a comparison chart of theoretical values ​​for heat transfer coefficients. For example... Figure 5A and Figure 5BAs shown, the evaporator 500 also includes a falling film tube bundle 515 and a flooded tube bundle 516. Both the falling film tube bundle 515 and the flooded tube bundle 516 include several heat exchange tubes arranged in rows. The heat exchange tubes in the flooded tube bundle 516 and their arrangement are the same as in the first and second embodiments. Furthermore, the heat exchange tubes in the falling film tube bundle 515 include several first heat exchange tubes 521 with a larger diameter D1 and several second heat exchange tubes 522 with a smaller diameter D2. Unlike the second embodiment, the first heat exchange tubes 521 are arranged in rows, and the second heat exchange tubes 522 are arranged in rows, with the rows of the first heat exchange tubes 521 and the rows of the second heat exchange tubes 522 alternating. As an example, the larger diameter D1 of the first heat exchange tubes 521 is equal to the diameter D0 of the heat exchange tube 320 in the first embodiment. In this embodiment, the diameter D1 of the large-diameter first heat exchange tube 521 is 1 inch, or 25.4 mm, and the diameter D2 of the small-diameter second heat exchange tube 522 is 3 / 4 inch, or 19.05 mm. In the falling film tube bundle 515, the ratio of the number of the first heat exchange tube 521 and the number of the second heat exchange tube 522 is approximately 1:1.

[0054] Figure 5B The diagram shows an enlarged view of four adjacent heat exchange tubes 521a, 521b, 522a, and 522b in two adjacent columns. These heat exchange tubes are adjacent to each other in pairs, and the centers of three adjacent heat exchange tubes form two equilateral triangles. Figure 5B As shown, heat exchange tubes 521a and 521b are in the same column, and heat exchange tubes 522a and 522b are in the same column. Furthermore, heat exchange tubes 521a, 522a, and 521b are adjacent, and heat exchange tubes 521b, 522a, and 522b are adjacent. In the height direction H, the centers of adjacent heat exchange tubes 521a and 522a in the same column have a vertical distance H2. In the width direction W, the centers of adjacent heat exchange tubes 521a and 522a in different columns have a horizontal distance W2. There is a minimum distance X2 between the outer surfaces of heat exchange tubes 521a and 521b. There is a minimum distance V2 between the outer surfaces of heat exchange tubes 522a and 521b, and between the outer surfaces of heat exchange tubes 522a and 521a. In this embodiment, V2 is greater than X2, and W2 ≥ D1.

[0055] Similar to the second embodiment, this embodiment also replaces a portion of the first heat exchange tubes 521 with larger diameter D1 with second heat exchange tubes 522 with smaller diameter D2. By reducing the diameter of a portion of the heat exchange tubes, the minimum distance V1 between the outer surfaces is increased, thereby reducing the flow velocity of the gas flowing between the corresponding heat exchange tubes and improving the heat exchange efficiency of the evaporator. Compared to the second embodiment, although V2 < V1, the minimum distance between the outer surfaces of the heat exchange tubes in adjacent rows of heat exchange tubes in each row of the falling film tube bundle 515 is increased.

[0056] It should be noted that in some other embodiments, in two adjacent columns, the centers of three adjacent heat exchange tubes 521a, 521b, 522a and 522b may not form two equilateral triangles, but rather form two isosceles triangles similar to the first embodiment, by increasing the horizontal spacing between adjacent heat exchange tubes in different columns.

[0057] Figure 5C A comparison chart shows the theoretical values ​​of the heat transfer coefficients of individual heat exchange tubes in the falling film tube bundle 515 of this embodiment, the second heat exchange tube in the falling film tube bundle 515 of this embodiment, the ideal falling film tube bundle including the first heat exchange tube, the ideal flooded tube bundle including the first heat exchange tube, the ideal falling film tube bundle including the second heat exchange tube, and the ideal flooded tube bundle including the second heat exchange tube, all with the same number of heat exchange tubes. The theoretical values ​​are obtained using the Gaussian distribution equation (1). Figure 5C In the diagram, the horizontal axis represents the number of heat exchange tubes in different rows from top to bottom, and the vertical axis represents the heat transfer coefficient. Lines 561, 562, 563, and 564 represent the heat transfer coefficients of a single heat exchange tube in an ideal falling film tube bundle including a first heat exchange tube, an ideal flooded tube bundle including a first heat exchange tube, an ideal falling film tube bundle including a second heat exchange tube, and an ideal flooded tube bundle including a second heat exchange tube, respectively. Curves 560 and 570 represent the heat transfer coefficients of the first and second heat exchange tubes in the falling film tube bundle 515 of this embodiment, respectively.

[0058] from Figure 5C As can be seen, although the heat transfer coefficients of the falling film tube bundles, including the first heat exchange tube 521 and the second heat exchange tube 522, decrease with the increase of the number of rows, the decrease in heat transfer coefficients with the number of rows is not significant, and they are all higher than the heat transfer coefficients of their respective fully saturated tube bundles.

[0059] Figures 6A-6C A fourth embodiment of the evaporator of this application is shown. Figure 6A It shows Figure 2 A radial section view of the evaporator 600 in the fourth embodiment of the evaporator. Figure 6B It shows Figure 6A A schematic diagram of the structure of baffle 631 in the middle. Figure 6C This is a comparison chart of theoretical values ​​for heat transfer coefficients. For example... Figure 6A and Figure 6BAs shown, the evaporator 600 includes a falling film tube bundle 615 and a flooded tube bundle 616, each comprising several heat exchange tubes arranged in a row. In this embodiment, the heat exchange tubes in the flooded tube bundle 616 and their arrangement are the same as in the first embodiment. Furthermore, the heat exchange tubes in the falling film tube bundle 615 and their arrangement are largely the same as in the first embodiment, and will not be described again here. The only difference is that in this embodiment, the heat exchange tubes in the middle of the falling film tube bundle 615 are spaced apart to form a fluid channel 638 extending approximately along the width direction W.

[0060] The evaporator 600 also includes a first baffle 631 and a second baffle 632, which are respectively disposed on the left and right sides of the falling film tube bundle 615 in the width direction W. Each of the first baffle 631 and the second baffle 632 has several windows 635 arranged along the length direction L and positioned at corresponding locations in the fluid channel 638. The fluid channel 638 and the windows 635 allow the gaseous refrigerant obtained from evaporation in the upper heat exchange tubes to flow out through the windows 635, instead of continuing to flow through the lower heat exchange tubes. This reduces the flow rate of the gaseous refrigerant through the lower heat exchange tubes.

[0061] In this embodiment, even though the space for the refrigerant channel used for refrigerant circulation is the same as in the first embodiment, the flow rate of the gaseous refrigerant in the lower falling film heat exchange tube bundle is reduced because a portion of the gaseous refrigerant is discharged through the fluid channel 638 and window 635, thereby improving the heat exchange efficiency of the evaporator.

[0062] Figure 6C A comparison chart showing the theoretical values ​​of the heat transfer coefficients of a single heat exchanger tube in the falling film tube bundle 615 of this embodiment, the falling film tube bundle 315 of the first embodiment, the ideal falling film tube bundle, and the ideal flooded tube bundle, with the same number of heat exchanger tubes, is shown. The theoretical values ​​are obtained through the Gaussian distribution equation (1). Figure 6C In the diagram, the horizontal axis represents the number of heat exchange tubes in different rows from top to bottom, and the vertical axis represents the heat transfer coefficient. Lines 661 and 662 represent the heat transfer coefficients of a single heat exchange tube in an ideal falling film tube bundle and a flooded tube bundle, respectively. Curves 668 and 670 represent the heat transfer coefficients of the falling film tube bundle 615 in this embodiment and the falling film tube bundle 315 in the first embodiment, respectively.

[0063] from Figure 6C As can be seen from the above, in the falling film tube bundle 615 of this embodiment, by discharging a portion of the gaseous refrigerant through the middle, the heat transfer coefficient of each row of heat exchange tubes can be maintained at a high level.

[0064] Those skilled in the art will understand that, although the heat exchange tubes in the falling film tube bundle are configured in a manner largely the same as in the first embodiment, the heat exchange tubes can also be configured in a manner largely the same as in the second or third embodiment. The only difference is that a fluid channel needs to be provided in the falling film tube bundle in the second or third embodiment, and a window for discharging gaseous refrigerant needs to be provided on the corresponding baffle of the fluid channel.

[0065] In the evaporators of the above embodiments, the falling film tube bundle in the evaporator of the first embodiment increases the space of the refrigerant channel in the width direction W by increasing the distance between each heat exchange tube in the width direction, that is, the spacing between the heat exchange tubes in each row. The falling film tube bundles in the evaporators of the second and third embodiments increase the minimum spacing between the outer surfaces of the heat exchange tube walls by replacing a portion of the heat exchange tubes with smaller diameter heat exchange tubes, thereby increasing the space of the refrigerant channel in the width direction W by at least a portion of the space.

[0066] In this application, by increasing the space of the refrigerant channel in the width direction W, the flow velocity of the gas flowing between the corresponding heat exchange tubes is reduced, thereby reducing the gas phase Reynolds number Re. v With liquid film Reynolds number Re film The ratio of [value] to [value] increases the heat exchange efficiency of the evaporator.

[0067] Although only some features of this application have been illustrated and described herein, many modifications and variations will be apparent to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and variations that fall within the essential spirit and scope of this application.

Claims

1. An evaporator, characterized by Comprising: a housing (203) having a cavity (310) with a length direction (L), a width direction (W) and a height direction (H); a falling film tube bundle (315) disposed in the cavity (310) and arranged in vertical columns, the falling film tube bundle (315) comprising a plurality of heat exchange tubes (320), each heat exchange tube (320) extending along the length direction (L) of the cavity (310), the centers of the heat exchange tubes (320) in each vertical column being arranged along the height direction (H), and the centers of the heat exchange tubes (320) in adjacent vertical columns being arranged staggered in the width direction (W) of the cavity (310); wherein the falling film tube bundle (315) is configured such that, among the four heat exchange tubes (320) in adjacent two vertical columns, the minimum distance (V0, V1, V2) between the outer surfaces of the heat exchange tubes (320) of at least two different vertical columns is greater than the minimum distance (X0, X1, X2) between the outer surfaces of the two heat exchange tubes (320) in the same vertical column.

2. The evaporator of claim 1, wherein: the distance between the outer surfaces of the heat exchange tubes (320) of at least two different vertical columns among the four heat exchange tubes (320) in adjacent two vertical columns is arranged such that the flow rate of gas flowing through the heat exchange tubes (320) in adjacent two vertical columns is reduced, thereby improving the heat exchange efficiency of the evaporator (100).

3. The evaporator of claim 2, wherein: Each heat exchange tube (320) in the falling film tube bundle (315) has the same tube diameter (D0), and the proportion of the spacing (W0) between the centers of two adjacent heat exchange tubes (320) in the width direction (W) of the cavity (310) to the spacing (H0) between the centers of two adjacent heat exchange tubes (320) in the height direction (H) of the cavity (310) in each vertical column satisfies 4. The evaporator of claim 2, wherein: the falling film tube bundle (415) comprises a plurality of first heat exchange tubes (421) having a larger tube diameter (D1) and a plurality of second heat exchange tubes (422) having a smaller tube diameter (D2); the first heat exchange tubes (421) and the second heat exchange tubes (422) are arranged staggered in the vertical columns of the falling film tube bundle (415).

5. The evaporator of claim 2, wherein: the falling film tube bundle (515) comprises a plurality of first heat exchange tubes (521) having a larger tube diameter (D1) and a plurality of second heat exchange tubes (522) having a smaller tube diameter (D2), the plurality of first heat exchange tubes (521) being arranged in vertical columns and the plurality of second heat exchange tubes (522) being arranged in vertical columns; wherein the vertical columns of the first heat exchange tubes (521) and the vertical columns of the second heat exchange tubes (522) are arranged staggered.

6. The evaporator of claim 4 or 5, wherein: the distance (W1, W2) between the centers of the adjacent first heat exchange tubes (421, 521) and the second heat exchange tubes (422, 522) in adjacent two vertical columns of the heat exchange tubes (320) in the width direction (W) of the cavity (310) is not less than the larger tube diameter (D1) of the first heat exchange tubes (421, 521).

7. The evaporator of claim 6, wherein: The larger tube diameter (D1) of the first heat exchange tube (421, 521) is 25.4 mm; and The smaller tube diameter (D2) of the second heat exchange tube (422, 522) is 19.05 mm.

8. The evaporator of claim 1, wherein: The evaporator further comprises: a first baffle (631) and a second baffle (632) disposed outside the falling film tube bundle (615) in the width direction (W) of the cavity (310) respectively; wherein the first baffle (631) and the second baffle (632) are each provided with a plurality of windows (635) arranged along the length direction (L) of the cavity (310), and the plurality of windows (635) are disposed outside the middle part of the falling film tube bundle (615) in the height direction (H) of the cavity (310).

9. The evaporator of claim 8, wherein: the heat exchange tubes in the middle part of the falling film tube bundle (615) are spaced apart to form fluid passages (638) extending in the width direction (W), and the fluid passages (638) are aligned with the corresponding plurality of windows (635) on each of the first baffle (631) and the second baffle (632) in the width direction (W).

10. A refrigeration system characterized by comprises: a compressor (193), a condenser (191), a throttling device (192) and an evaporator (100) disposed in a refrigerant circuit, wherein the evaporator (100) is any one of claims 1-9.

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