A low-pressure refrigerant distributor and falling-film evaporator thereof

Abstract

The application discloses a low-pressure refrigerant distributor and a falling-film evaporator thereof, and belongs to the technical field of refrigeration and air conditioning. The low-pressure refrigerant distributor comprises a conical axial distribution box and a liquid distribution box, the axial distribution box is installed in the liquid distribution box through a plurality of support structures, the plurality of support structures are equidistantly arranged along the axial direction of the liquid distribution box, and the axial distribution box is used for dividing refrigerant liquid in the liquid distribution box into a plurality of equidistant small chambers along the axial direction, and the support structure can be used as a support for the axial distribution box. In the application, the gas-liquid separator can effectively reduce the airflow resistance, compared with the prior art, under the condition of keeping the same flow resistance, the diameter of the cylinder can be reduced by about 10%, the cost of the evaporator is effectively reduced, the conical axial distribution box keeps the static pressure of the refrigerant unchanged in the axial flow, and the non-uniformity of the axial flow distribution is kept below 10%. The gas-liquid separator and the conical distribution box can effectively reduce the refrigerant charging amount, and the refrigerant charging amount of the falling-film evaporator can be reduced by about 15%.

Description

Technical Field

[0001] This invention relates to a low-pressure refrigerant distributor and a falling film evaporator of the distributor, belonging to the field of refrigeration and air conditioning technology. Background Technology

[0002] A low-pressure refrigerant falling film evaporator includes a shell; a heat exchange tube bundle; a refrigerant gas-liquid separator and distributor located at the top of the shell; and a gas outlet at the top of the shell. The gas-liquid two-phase refrigerant enters the shell from the top position, is separated into gas and liquid in the gas-liquid separator, and the liquid refrigerant is distributed to the shell side by the distributor and flows downwards through the tube bundle, absorbing heat and boiling. The vapor flows out of the evaporator from the outlet at the top of the shell. The gas separated by the gas-liquid separator also flows out of the evaporator from the outlet at the top of the shell. Water flows on the tube side of the heat exchange tube bundle, transferring heat to the refrigerant on the shell side, causing the water temperature to drop, thus obtaining the chilled water required for air conditioning (e.g., the refrigerant distributor for a falling film evaporator disclosed in publication number CN109642760A).

[0003] Compared to flooded evaporators (such as the flooded evaporator shown in publication number CN211204506U), falling film evaporators have a lower refrigerant level on the shell side. This effectively reduces the refrigerant charge and lowers the hydrostatic pressure of the refrigerant liquid, increasing the heat exchange temperature difference between the shell-side refrigerant and the pipe-side water. The saturation temperature of low-pressure refrigerants is pressure-sensitive. For example, at 6°C, a 1 kPa pressure change results in a 0.4°C change in the saturation temperature of low-pressure refrigerant R1233zde and a 0.1°C change in the saturation temperature of medium-pressure refrigerant R134a. Therefore, reducing the hydrostatic pressure of the refrigerant liquid is crucial for the heat exchange performance of low-pressure refrigerant evaporators. Simultaneously, reducing the flow pressure drop of the refrigerant gas within the evaporator is also a key factor in the successful design of low-pressure refrigerant evaporators.

[0004] Patent CN215063028U discloses a distributor and a falling film evaporator including the distributor, proposing a distributor design for a falling film evaporator. The distributor includes a primary distributor and a secondary distributor. The primary distributor is a gas-liquid separation chamber arranged along the length of the evaporator. Multiple perforated plates are arranged inside the separation chamber along the flow direction to reduce disturbance to the axial flow of the refrigerant and promote gas-liquid separation. Small holes are evenly distributed on the bottom plate of the gas-liquid separation chamber, through which the separated liquid falls into the secondary distributor. The secondary distributor is a liquid distribution box with an open top and evenly distributed small holes at the bottom. The liquid in the distribution box is evenly distributed onto the tube bundle below the distributor through the small holes. This design lacks a dedicated axial refrigerant distributor. Under low-load conditions, the liquid level in the gas-liquid separation chamber is uneven along its length, which may affect the uniformity of refrigerant distribution along the tube length and reduce the heat exchange performance of the evaporator at low loads.

[0005] Patent CN105518391A discloses an integrated separator-distributor for a falling film evaporator, proposing a separator and distributor design for a falling film evaporator. The separator has two designs: Design 1 allows the refrigerant to enter from the middle of the gas-liquid separator and then flow to both ends; Design 2 allows the refrigerant to enter from one end of the separator and flow to the other. The liquid refrigerant after gas-liquid separation flows into an axial distributor, which has a fixed cross-sectional shape along the axial direction. The refrigerant gas separated by the gas-liquid separator is guided to the vicinity of the refrigerant liquid surface at the bottom through a ventilation riser. This axial distributor design requires a larger amount of refrigerant due to its fixed flow area along the flow direction. Furthermore, as the refrigerant flows axially from the inlet end to the other end, the flow velocity gradually decreases, and the hydrostatic pressure along the axial direction increases, which is detrimental to the uniformity of axial refrigerant distribution. The designed ventilation riser guides the gas (with some liquid droplets) to the bottom refrigerant liquid surface; however, the excessive length of the pipe wastes material and also blocks part of the airflow channel at the bottom of the evaporator, increasing the flow pressure drop. In addition, the outlet of the evaporator in this patented design is installed on the side of the evaporator cylinder, and the outlet is close to the liquid surface at the bottom. This is not conducive to the full separation of liquid droplets entrained in the steam, and it is easy to cause liquid to be drawn into the compressor, which reduces the performance of the refrigeration machine.

[0006] Patent CN109642760A discloses a refrigerant distributor for a falling film evaporator, proposing a distributor design for a falling film evaporator. The upper surface of its refrigerant gas-liquid separator is arranged at an angle, with the lowest height at the outlet and the highest height at the other end or both ends of the cylinder. This design increases the flow area of ​​the refrigerant below the outlet and reduces the local flow resistance of the refrigerant vapor below the outlet. However, the gas-liquid separator is similar in length to the evaporator cylinder, resulting in a relatively large refrigerant charge. Furthermore, although the height of the gas-liquid separator is lowest at the outlet, it still obstructs part of the flow area, increasing the flow resistance.

[0007] Patent CN111919075A discloses an integrated separator and distributor, proposing an integrated gas-liquid separator and distributor structure for a falling film evaporator. After refrigerant separation in the separator, liquid refrigerant flows directly into a groove from openings on both sides at the bottom of the separator. The groove is arranged axially along the evaporator. The liquid entering the groove flows out from a series of axially arranged small holes at the top of the groove channel. Therefore, the groove effectively functions as an axial distributor. The advantage of this invention is that the axial distribution of refrigerant is achieved through a smaller groove, which helps reduce the refrigerant charge. However, the groove manufacturing is relatively complex. Additionally, the gas-liquid separator extends axially below the outlet, obstructing part of the airflow channel. To reduce the flow resistance of the gaseous refrigerant, a larger evaporator shell is required to house the gas-liquid separator.

[0008] Therefore, it is necessary to design a low-pressure refrigerant distributor and a falling film evaporator of the distributor to solve the above problems. Summary of the Invention

[0009] This invention proposes a low-pressure refrigerant distributor and a falling film evaporator of the distributor. The design aims to combine the features of a gas-liquid separator and a distributor with low refrigerant charge. Using this patented design, the refrigerant charge of the falling film evaporator can be reduced by approximately 15%. The gas velocity is highest near the evaporator outlet, making it the most sensitive area to flow resistance. By designing a gas-liquid separator, the flow area below the outlet is increased, reducing flow resistance. Alternatively, while maintaining the same flow resistance, the cylinder diameter can be reduced by approximately 10%, effectively lowering the evaporator cost. Furthermore, an outlet guide pipe is installed on the separator to effectively remove refrigerant liquid entrained in the outlet guide pipe, preventing liquid from flowing into the compressor through the outlet and causing liquid carryover during suction.

[0010] The following technical solution is adopted to achieve this:

[0011] A low-pressure refrigerant distributor includes a conical axial distribution box and a liquid distribution box. The axial distribution box is installed inside the liquid distribution box by multiple support structures, which are equidistantly arranged along the axial direction of the liquid distribution box. These support structures divide the refrigerant liquid in the liquid distribution box into multiple equidistant small chambers along the axial direction. The support structures can also be used to support the axial distribution box. On the other hand, the upper surface of the axial distribution box is provided with outflow holes along the axial direction. When the refrigerant liquid in the axial distribution box flows out through the outflow holes and falls into the liquid distribution box, it converges after entering the multiple small chambers. The bottom surface of the liquid distribution box is a perforated plate, and the converged refrigerant flows out through the holes on the perforated plate.

[0012] Using the above scheme, when the liquid enters the axial distribution box from the larger end, it flows axially to the other end. Along the way, some liquid flows out from the top of the axial distribution box, reducing the axial flow rate of the liquid. However, since the flow cross-sectional area of ​​the axial distribution box gradually decreases along the way, the refrigerant liquid velocity along the axial direction can remain approximately constant. Therefore, the static pressure of the fluid remains almost constant, and the pressure difference between the inside and outside of each small hole in the axial distribution box remains constant, as does the outflow rate of each small hole. Furthermore, the non-uniformity of the axial outflow in the axial distribution box is further reduced after the convergence effect of the small chambers, thereby enhancing the uniformity of the refrigerant distribution along the axial direction and reducing the refrigerant charge.

[0013] A falling film evaporator includes a cylindrical body, a first outlet, a gas-liquid separator, a liquid inlet pipe, and the aforementioned axial distribution box and liquid distribution box. The first outlet is located at one end of the cylindrical body and communicates with the interior of the cylindrical body. The gas-liquid separator is installed inside the cylindrical body and extends from the first outlet to the other end of the cylindrical body to avoid the space below the outlet, increase the clearance below the outlet, and reduce the airflow resistance. One end of the liquid inlet pipe extends into the interior of the gas-liquid separator and corresponds to one end face of the gas-liquid separator. After the refrigerant enters the gas-liquid separator through the liquid inlet pipe, it is sprayed onto the end face of the gas-liquid separator and then flows in the reverse direction. The liquid flows out from the liquid outlet at the other end of the gas-liquid separator.

[0014] The liquid distribution box is located inside the cylinder, and both the liquid distribution box and the axial distribution box are located below the gas-liquid separator. The bottom of the gas-liquid separator is connected to the axial distribution box.

[0015] It should be noted that the cross-sectional shape of the gas-liquid separator is rectangular, but the present invention does not limit the cross-sectional shape of the separator; it can be circular, elliptical, curved, or other shapes.

[0016] Preferably, the outflow orifices are evenly distributed along the length of the evaporator or along the length of the distribution box, and the cone angle of the axial distribution box is 3-7°. .

[0017] Preferably, the inlet pipe is a bent pipe, and the other end of the inlet pipe extends out of the cylinder.

[0018] Preferably, two second air outlets are arranged on the other end of the gas-liquid separator. The two second air outlets are symmetrically arranged and both are close to the upper part of the gas-liquid separator. The gas after gas-liquid separation flows out from the second air outlets, and the liquid outlet is flush with the bottom surface of the gas-liquid separator, which is conducive to the liquid flowing out.

[0019] It should be noted that a baffle or demister can be installed at the air outlet of the separator to eliminate some of the liquid droplets entrained in the airflow.

[0020] Preferably, the liquid outlet of the gas-liquid separator is connected to a liquid pipe, and the other end of the liquid pipe extends into the liquid distribution box and is connected to the axial distribution box inside the liquid distribution box.

[0021] It should be noted that the end of the axial distribution box located at the liquid pipe connection is larger than the other end of the axial distribution box.

[0022] Using the above scheme, the hydrostatic head provided by the liquid in the liquid pipe is used to overcome the flow resistance of the refrigerant liquid in the axial distribution box.

[0023] Preferably, the falling film evaporator further includes a tube bundle support plate, a cover plate, and a heat exchange tube bundle passing through the tube holes of the tube bundle support plate, respectively arranged in the cylinder. The cover plate is L-shaped, and the horizontal side of the cover plate closes the upper part of the liquid distribution box. The vertical side of the cover plate extends downward close to the side of the tube bundle support plate until it exceeds the falling film zone tube hole at the bottom of the tube bundle support plate. A notch is provided above the side panel of the liquid distribution box, and a gap is also provided between the cover plate and the side panel of the liquid distribution box. By setting the notch and the gap, a pressure balance channel is formed to keep the internal pressure of the liquid distribution box equal to the pressure of the falling film tube bundle zone, so that the liquid in the liquid distribution box can fall into the falling film tube bundle zone by the hydrostatic pressure of the liquid column.

[0024] It should be noted that the refrigerant falling into the liquid distribution box passes through the perforated plate on the liquid distribution box and drips onto the falling film tube bundle through the small holes on the perforated plate.

[0025] The vertical edge of the L-shaped cover plate wraps around the outside of the falling film tube bundle region, which can guide the gas generated by evaporation in the falling film tube bundle region to flow downward and in the same direction as the droplets, avoiding the lateral flow of airflow, which may disrupt the flow of droplets.

[0026] Preferably, the falling film evaporator also includes a demister mesh installed between the cylinder and the cover plate to remove liquid droplets entrained in the refrigerant gas.

[0027] It should be noted that, in order to reduce the flow velocity through the screen, the demister mesh is installed near the center of the cylinder at a horizontal position or at an angle, with the angle of inclination relative to the horizontal plane being [missing information]. 30 Within.

[0028] Preferably, the falling film evaporator further includes a gas guide pipe disposed inside the cylinder. The gas guide pipe is connected to the second gas outlet of the gas-liquid separator, and the other end extends into the lower part of the demister mesh. The gas guide pipe guides the gas flow from the gas-liquid separator and the liquid droplets entrained therein to the lower part of the demister mesh, mixes with the gas flow generated by the tube bundle evaporation, and then passes upward through the demister mesh.

[0029] Unlike the design in CN105518391A, the air guide pipe of this invention only needs to pass through the demister mesh at the center horizontal plane of the cylinder to remove entrained droplets, without needing to guide the pipe to the vicinity of the liquid pool at the bottom. On the one hand, the demister mesh effectively removes entrained droplets; on the other hand, it reduces the length of the air guide pipe, saving costs, and also avoids the blockage of the lower airflow channel of the evaporator by a long air guide pipe, thus preventing increased flow pressure drop.

[0030] It should also be mentioned that in a falling film evaporator, when the first outlet is located near the axial center of the cylinder, two gas-liquid separators can be arranged on both sides of the outlet. Each gas-liquid separator has a liquid inlet pipe, a liquid outlet, and one or two second outlets. The liquid outlet of each gas-liquid separator is connected to two conical axial distribution boxes below through their respective liquid pipes. Each axial distribution box is placed inside a liquid distribution box. Each axial distribution box ensures the uniform distribution of refrigerant along the axial direction. The liquid distribution box collects the refrigerant liquid and then distributes it again to the falling film tube bundle below.

[0031] The beneficial effects of this invention are as follows: The gas-liquid separator designed in this invention can effectively reduce airflow resistance. Compared with the prior art, while maintaining the same flow resistance, the cylinder diameter can be reduced by about 10%, effectively reducing the cost of the evaporator. The conical axial distribution box maintains a constant static pressure of the refrigerant in axial flow, keeping the non-uniformity of axial flow distribution below 10%. The gas-liquid separator and the conical distribution box can effectively reduce the refrigerant charge, reducing the refrigerant charge of the falling film evaporator by about 15%. Attached Figure Description

[0032] Figure 1 This is a three-dimensional structural diagram of the falling film evaporator in this invention;

[0033] Figure 2 This is a longitudinal cross-sectional view of the falling film evaporator in this invention;

[0034] Figure 3 This is a schematic diagram of the axial distribution box and the liquid distribution box in this invention;

[0035] Figure 4 This is a cross-sectional view of the falling film evaporator of the present invention, in which the evaporator cylinder is not shown;

[0036] Figure 5 for Figure 4 A partial schematic diagram of the transverse cross-section;

[0037] Figure 6 This is a schematic diagram of the support plate structure for a falling film evaporator, where the heat exchange tube bundle passing through the tube holes is not shown.

[0038] In the diagram: 1. Gas-liquid separator; 2. First gas outlet; 3. Cylinder; 4. Demister mesh; 5. Cover plate; 6. Liquid distribution box; 7. Tube bundle support plate; 8. Axial distribution box; 9. Support structure; 10. Liquid inlet pipe; 11. Second gas outlet; 12. Gas guide pipe; 13. Liquid outlet; 14. Liquid pipe; 15. Vertical edge; 16. Outflow orifice; 17. Perforated plate; 18. Notch; 19. Full liquid zone pipe hole; 20. Falling film zone pipe hole; 21. Liquid level of refrigerant liquid pool. Detailed Implementation

[0039] To facilitate a clear understanding of the technical means, creative features, and achieved objectives and effects of this invention, the invention will be further described below in conjunction with specific illustrations.

[0040] like Figures 1-6 As shown, a low-pressure refrigerant distributor includes a conical axial distribution box 8 and a liquid distribution box 6. The upper surface of the axial distribution box 8 is provided with an outflow hole 16 along the axial direction. The bottom surface of the liquid distribution box 6 is a perforated plate 17. The axial distribution box 8 is installed in the liquid distribution box 6 by multiple support structures 9, and the multiple support structures 9 are equidistantly arranged along the axial direction of the liquid distribution box 6 to divide the refrigerant liquid in the liquid distribution box 6 into multiple equidistant small chambers along the axial direction. The support structures 9 can be used to support the axial distribution box 8. On the other hand, when the refrigerant liquid flows out from the outflow hole 16 of the axial distribution box 8 and falls into the liquid distribution box 6, it enters the multiple small chambers and converges. The converged refrigerant flows out through the small holes of the perforated plate 17.

[0041] It should be noted that the gas content in the gas-liquid separator is based on... Formula calculation: (1.1)

[0042] in It is the gas phase gas content; It is the percentage of gas phase volumetric flow rate, calculated by the following formula:

[0043] (1.2)

[0044] in It is the percentage of gas phase mass flow rate (dryness) in the separator channel; , These are the densities of the gas and liquid phases, respectively. .

[0045] Parameters in equation (1.1) It is a parameter The function. Parameters Represented as: (1.3)

[0046] in It is the hydraulic diameter of the flow passage cross section of the separator. ; , These are the gas and liquid phase dynamic viscosities, respectively. g is the acceleration due to gravity, 9.81 m / s². 2 G is the mass flow rate, kg / (m²). 2 s):

[0047] (1.4)

[0048] Where m is the refrigerant mass flow rate. A i It is the flow cross-sectional area of ​​the separator, m 2 .

[0049] The calculation results are shown in Table 1.

[0050] Table 1 compares the prior art (publication number CN109642760A) with the present invention.

[0051]

[0052] Calculations show that the conical distribution box, together with the shortened gas-liquid separator, can reduce the evaporator charge by approximately 15%, as shown in Table 1. Table 1 indicates the refrigerant charge savings of a 700-ton falling film evaporator designed using the technology of this invention. This falling film evaporator uses R1233zde low-pressure refrigerant, has a cylinder diameter of 1.12m, an evaporator length of 3.66m, an outlet inner diameter of 0.58m, and the outlet is located at 20% axial distance from one end of the evaporator. As can be seen from Table 1, compared with the prior art, the gas-liquid separator and axial distributor of this invention can save 18kg and 30kg of refrigerant respectively, totaling an equivalent of 15% reduction in evaporator charge. It should be noted that using the technology of this invention can reduce the cylinder diameter, thus saving even more refrigerant charge.

[0053] In summary, the conical axial distribution box not only improves the uniformity of refrigerant distribution along the axial direction, but also reduces the refrigerant charge.

[0054] A falling film evaporator includes a cylinder 3, a first outlet 2, a gas-liquid separator 1, a liquid inlet pipe 10, the aforementioned axial distribution box 8 and liquid distribution box 6. The first outlet 2 is located at one end of the cylinder 3 and communicates with the interior of the cylinder 3. The gas-liquid separator 1 is installed inside the cylinder 3 and extends from the first outlet 2 to the other end of the cylinder 3 to avoid the space below the outlet, increase the clearance below the outlet, and reduce the airflow resistance. One end of the liquid inlet pipe 10 extends into the interior of the gas-liquid separator 1 and corresponds to one end face of the gas-liquid separator 1. After the refrigerant enters the gas-liquid separator 1 through the liquid inlet pipe 10, it is sprayed onto the end face of the gas-liquid separator 1 and then flows in the reverse direction. The liquid flows out from the liquid outlet 13 at the other end of the gas-liquid separator 1.

[0055] The liquid distribution box 6 is located inside the cylinder 3, and both the liquid distribution box 6 and the axial distribution box 8 are located below the gas-liquid separator 1. The bottom of the gas-liquid separator 1 is connected to the axial distribution box 8.

[0056] The inlet pipe 10 is a bent pipe, and the other end of the inlet pipe 10 extends out of the cylinder 3.

[0057] Two second air outlets 11 are arranged on the other end of the gas-liquid separator 1. The two second air outlets 11 are symmetrically arranged and are close to the upper part of the gas-liquid separator 1. The gas after gas-liquid separation flows out from the second air outlet, and the liquid outlet 13 is flush with the bottom surface of the gas-liquid separator 1, which is conducive to the liquid flowing out.

[0058] A liquid pipe 14 is connected to the liquid outlet 13 of the gas-liquid separator 1. The other end of the liquid pipe 14 extends into the liquid distribution box 6 and is connected to the axial distribution box 8 inside the liquid distribution box 6.

[0059] The outlet orifices 16 are evenly distributed along the length of the evaporator cylinder 3 or along the length of the axial distribution box 8, and the cone angle of the axial distribution box 8 is 3-7°. .

[0060] The falling film evaporator also includes a tube bundle support plate 7, a cover plate 5, and a heat exchange tube bundle (not shown in the figure) passing through the tube holes of the support plate, which are respectively arranged in the cylinder 3. The cover plate 5 is L-shaped, and the horizontal side of the cover plate 5 closes the upper part of the liquid distribution box 6. The vertical side 15 of the cover plate 5 extends downward close to the side of the tube bundle support plate 7 until it exceeds the falling film zone tube hole 20 at the bottom of the tube bundle support plate 7. A notch 18 is provided above the side panel of the liquid distribution box 6, and a gap is also provided between the cover plate 5 and the side panel of the liquid distribution box 6. By setting the notch 18 and the gap, a pressure balance channel is formed to keep the internal pressure of the liquid distribution box 6 equal to the pressure of the falling film tube bundle zone, so that the liquid in the liquid distribution box can fall into the falling film tube bundle zone by the hydrostatic pressure of the liquid column.

[0061] Heat exchange tube bundles (not shown in the figure) pass through the tube holes in the tube bundle support plate. These tube bundles are divided into upper and lower sections. The upper tube bundle is called the falling film heat exchange tube bundle, and the lower tube bundle is called the flooded heat exchange tube bundle. The shell-side region where the falling film heat exchange tube bundle is located is called the falling film tube bundle region, and the shell-side region where the flooded heat exchange tube bundle is located is called the flooded tube bundle region. It should be noted that there is a refrigerant liquid pool below the falling film evaporator shell 3. The liquid level in the pool is generally at the top of the flooded tube bundle region, see [reference needed]. Figure 6 As shown by the wavy line.

[0062] The falling film evaporator also includes a demister mesh 4 installed between the cylinder 3 and the cover plate 5 to remove liquid droplets entrained in the refrigerant gas.

[0063] The falling film evaporator also includes a gas guide pipe 12 located inside the cylinder. The gas guide pipe 12 is connected to the second gas outlet 11 of the gas-liquid separator 1, and the other end extends into the lower part of the demister wire mesh 4. The gas guide pipe guides the gas flow from the gas-liquid separator and the liquid droplets entrained therein to the lower part of the demister wire mesh 4, mixes with the gas flow generated by the tube bundle evaporation, and then passes upward through the demister wire mesh 4.

[0064] It should be noted that the first outlet 2 is connected to the external compressor. The liquid droplets carried by the upward airflow are separated, collected, and dripped back into the liquid pool below the cylinder 3 by the demister mesh 4. The gas rises and enters the external compressor through the outlet 2.

[0065] It should be noted that the two-phase mixture enters the cylinder through the inlet pipe. Guided by the inlet pipe, it first flows to one end face of the gas-liquid separator, and then flows in the opposite direction to the other side of the gas-liquid separator. Gas-liquid separation is achieved by utilizing the length of the gas-liquid separator, and the reverse flow also facilitates gas-liquid separation. The cross-sectional dimensions of the gas-liquid separator must meet the following requirements:

[0066]

[0067] Where Fr g It is the gas phase Froude number;

[0068] The length of the gas-liquid separator shall not be less than 8 times the hydraulic diameter d of the flow passage. h, m.

[0069] In another embodiment, in a falling film evaporator, when the first outlet 2 is arranged near the axial center of the cylinder 3, two gas-liquid separators 1 can be arranged on both sides of the outlet 2. Each gas-liquid separator 1 has a liquid inlet pipe 10, a liquid outlet 13, and one or two second outlets 11. The liquid outlet 13 of each gas-liquid separator 1 is connected to two conical axial distribution boxes 8 below through their respective liquid pipes 14. Each axial distribution box 8 is placed in a liquid distribution box 6. Each axial distribution box 8 ensures the uniform distribution of refrigerant along the axial direction. The liquid distribution box 6 collects the refrigerant liquid and then redistributes it to the falling film tube bundle below.

[0070] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention, all of which fall within the scope of the claims. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A falling film evaporator, characterized in that, The device includes a cylindrical body, a first gas outlet, a gas-liquid separator, a liquid inlet pipe, a conical axial distribution box, and a liquid distribution box. The axial distribution box is installed inside the liquid distribution box via multiple support structures, which are equidistantly arranged along the axial direction of the liquid distribution box. These support structures divide the refrigerant liquid in the liquid distribution box into multiple equidistant chambers along the axial direction. The support structures also support the axial distribution box. The upper surface of the axial distribution box has outflow holes along the axial direction. When the refrigerant liquid in the axial distribution box flows out through the outflow holes and falls into the liquid distribution box, it converges after entering the multiple chambers. The bottom surface of the liquid distribution box is a perforated plate. The collected refrigerant flows out through small holes in the perforated plate; the first outlet is located at one end of the cylinder and communicates with the inside of the cylinder; the gas-liquid separator is installed inside the cylinder and extends from the first outlet to the other end of the cylinder to avoid the space below the outlet, increase the gap below the outlet, and reduce the airflow resistance; one end of the liquid inlet pipe extends into the inside of the gas-liquid separator and corresponds to one end face of the gas-liquid separator; after the refrigerant enters the gas-liquid separator through the liquid inlet pipe, it is sprayed onto the end face of the gas-liquid separator and then flows in the opposite direction, and the liquid flows out from the liquid outlet at the other end of the gas-liquid separator; The liquid distribution box is located inside the cylinder, and both the liquid distribution box and the axial distribution box are located below the gas-liquid separator. The bottom of the gas-liquid separator is connected to the axial distribution box. Two second air outlets are arranged on the other end of the gas-liquid separator. The two second air outlets are symmetrically arranged and close to the upper part of the gas-liquid separator. The gas after gas-liquid separation flows out from the second air outlets, and the liquid outlet is flush with the bottom surface of the gas-liquid separator, which is conducive to the liquid flowing out. The liquid outlet of the gas-liquid separator is connected to a liquid pipe, and the other end of the liquid pipe extends into the liquid distribution box and is connected to the axial distribution box inside the liquid distribution box. It also includes a tube bundle support plate, a cover plate, and a heat exchange tube bundle passing through the tube holes of the tube bundle support plate, which are respectively installed in the cylinder. The cover plate is L-shaped, and the horizontal side of the cover plate closes the upper part of the liquid distribution box. The vertical side of the cover plate extends downward close to the side of the tube bundle support plate until it exceeds the falling film zone tube hole at the bottom of the tube bundle support plate. A notch is opened above the side panel of the liquid distribution box, and a gap is also provided between the cover plate and the side panel of the liquid distribution box. By setting the notch and the gap, a pressure balance channel is formed to keep the internal pressure of the liquid distribution box equal to the pressure of the falling film tube bundle zone, so that the liquid in the liquid distribution box can fall into the falling film tube bundle zone by the hydrostatic pressure of the liquid column.

2. A falling film evaporator according to claim 1, characterized in that: The outflow orifices are evenly distributed along the length of the evaporator cylinder or along the length of the distribution box, and the cone angle of the axial distribution box is 3-7°. .

3. A falling film evaporator according to claim 2, characterized in that: It also includes a demister mesh installed between the cylinder and the cover plate to remove liquid droplets entrained in the refrigerant gas.

4. A falling film evaporator according to claim 3, characterized in that: It also includes a gas guide pipe installed inside the cylinder. The gas guide pipe is connected to the second gas outlet of the gas-liquid separator, and the other end extends into the lower part of the demister mesh. The gas guide pipe guides the gas flow from the gas-liquid separator and the liquid droplets entrained therein to the lower part of the demister mesh, mixes with the gas flow generated by the evaporation of the tube bundle, and then passes upward through the demister mesh.

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