A high-efficiency oil return kettle evaporator

Abstract

The present invention relates to the technical field of evaporators, and discloses a high-efficiency oil return kettle evaporator, comprising a first cylinder and a second cylinder connected to each other, the second cylinder being provided with a heat source inlet and a heat source outlet, a liquid inlet pipe being provided at the lower end of the first cylinder, an air outlet pipe being provided at the upper end, an axially arranged heat exchange tube bundle being provided in the first cylinder, and also comprising a filling block, the filling block being arranged along the axial direction of the first cylinder, the filling block being symmetrically arranged on both sides of the first cylinder, the outer side of the filling block being in contact with the inner wall of the first cylinder, the inner side of the filling block being corresponding to the heat exchange tube bundle, a liquid passage for the working medium to pass through being provided between the filling block and the heat exchange tube bundle, and an oil separation device being provided on at least one side of the filling block. By adding a filling block to the kettle evaporator, the filling amount of the working medium can be reduced by more than 40%, and the cost of filling the working medium can be reduced. By arranging a capillary through tube on the filling block, under the action of the capillary phenomenon, efficient separation of lubricating oil and working medium can be achieved, and the amount of oil return can be increased.

Description

Technical Field

[0001] The invention relates to the technical field of evaporators, and in particular to a high-efficiency oil return kettle type evaporator. Background Art

[0002] Most of the evaporators of high-temperature heat pump units and the top condensing evaporators of closed heat pump distillation systems are kettle evaporators or flooded evaporators. Compared with the flooded evaporators, kettle evaporators have higher heat exchange efficiency and better gas-liquid separation effects, but kettle evaporators have larger cylinders, large working fluid filling volumes, and poor oil return effects.

[0003] At present, the most commonly used working fluids for high-temperature heat pumps include R245FA, R1233zde, etc. Among them, R245FA is a hydrofluorocarbon and R1233zde is a hydrofluoroolefin. The prices of these working fluids are particularly high. Although the kettle evaporator has advantages in heat exchange efficiency and gas-liquid separation effect, the cost of the kettle evaporator and the cost of the filling working fluid are relatively high. The lubricating oil and working fluid used in the high-temperature heat pump are miscible. More than 95% of the direct return oil from the evaporator is working fluid liquid, which will reduce the cooling capacity and heating capacity of the system. In addition, the return oil of the screw heat pump unit usually returns to the suction line, which will cause the compressor to carry liquid in the suction. Since the liquid is incompressible, it will have a severe impact on the moving parts inside the compressor, which may cause serious mechanical damage or even compressor failure. At the same time, it reduces the exhaust superheat and reduces the separation efficiency of the exhaust oil separator.

[0004] Therefore, how to reduce the amount of working fluid charged in the kettle evaporator and solve the problem of a large amount of working fluid in the return oil pipeline has become a technical problem that needs to be solved. Summary of the invention

[0005] The present invention aims at solving the existing technical problems and provides a high-efficiency oil return kettle type evaporator.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a high-efficiency oil return kettle evaporator comprises a first cylinder and a second cylinder, the first cylinder and the second cylinder are connected, a heat source inlet and a heat source outlet are provided on the second cylinder, a liquid inlet pipe is provided at the lower end of the first cylinder, and an air outlet pipe is provided at the upper end, an axially arranged heat exchange tube bundle is provided in the first cylinder, and also comprises a filling block, the filling block is arranged along the axial direction of the first cylinder, the filling blocks are symmetrically arranged on both sides of the first cylinder, the outer side of the filling block is in contact with the inner wall of the first cylinder, the inner side of the filling block corresponds to the heat exchange tube bundle, a liquid passage for the working medium to pass through is provided between the filling block and the heat exchange tube bundle, and an oil separation device is provided on at least one side of the filling block.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows:

[0008] Preferably, the oil separation device includes an oil storage chamber, a capillary tube and an oil outlet pipeline. There are multiple capillary tubes, one end of each of which is connected to the liquid passage and the other end is connected to the oil storage chamber. One end of the oil outlet pipeline is connected to the oil storage chamber and the other end extends out of the first cylinder.

[0009] Preferably, the capillary tube is arranged obliquely, and the inlet height of the capillary tube at the liquid passage is smaller than the outlet height of the capillary tube at the oil storage chamber.

[0010] Preferably, the oil separator is provided in plurality, and the plurality of oil separators are spaced apart along the axial direction of the first cylinder.

[0011] Preferably, a mounting plate is provided on the inner wall of the first cylinder, and a slot is formed between the mounting plate and the inner wall of the first cylinder, and the filling block is inserted into the slot.

[0012] Preferably, an arc segment and a first inclined segment are provided on the inner side of the filling block, the liquid passage is located between the arc segment, the first inclined segment and the heat exchange tube bundle, and the inclination angle θ1 of the first inclined segment is 71.5°-77°.

[0013] Preferably, an air suction baffle is installed in the first cylinder, the air suction baffle is located above the heat exchange tube bundle, and a gas passage is formed between the air suction baffle and the second inclined section of the filling block.

[0014] Preferably, the inclination angle θ2 of the second inclination section is 117.5°-130°.

[0015] Preferably, the filling block is a solid structure; or, the filling block is a hollow or airbag structure and the interior of the filling block is connected to the air outlet pipe.

[0016] Preferably, the filling block is made of polypropylene or polytetrafluoroethylene.

[0017] The beneficial effects of the present invention are:

[0018] 1. By adding filling blocks to the kettle evaporator, the filling amount of the working fluid can be reduced by more than 40%, the cost of filling the working fluid can be reduced, and the investment cost of equipment such as the liquid storage device of the heat pump unit can be reduced.

[0019] 2. The material of the filling block will not react with the working fluid and lubricating oil, and is easy to shape, ensuring the normal operation of the heat pump unit.

[0020] 3. By arranging a capillary tube on the filling block, under the action of capillary phenomenon, efficient separation of lubricating oil and working fluid is achieved, the return oil volume is increased, the problem of a large amount of working fluid in the return oil pipeline is solved, and the lubricating effect of the lubricating oil on the compressor is ensured.

[0021] 4. The return oil is mainly returned lubricating oil, which contains very little working substance. The heat pump unit will not have stability problems due to the return oil containing a large amount of working substance. There is no need to add an oil collector or return oil heating equipment to the heat pump unit, which further reduces the use cost and ensures the stable operation of the heat pump unit.

[0022] 5. By designing the air suction baffle and gas passage, the gas-liquid separation effect is further improved, the amount of liquid and foam in the air suction is reduced, the service life of the compressor is guaranteed, and the heat exchange efficiency of the kettle evaporator is guaranteed.

[0023] 6. The filling block adopts modular, integrally molded and push-in embedded structure, which is simple to process, easy to install, and not easy to fall off, ensuring the stability and firmness of the filling block installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a front view of the kettle evaporator of the present invention;

[0025] Figure 2 It is a cross-sectional schematic diagram of a kettle evaporator of the present invention;

[0026] Figure 3 It is a schematic diagram of the filling block and the oil separation device of the present invention;

[0027] Figure 4 It is a schematic diagram of the oil separation device of the present invention being arranged along the axial direction of the kettle type evaporator;

[0028] Figure 5 It is a longitudinal partial cross-sectional schematic diagram of the fin heat exchange tube of the present invention;

[0029] Figure 6 It is a longitudinal partial cross-sectional schematic diagram of a T-shaped heat exchange tube of the present invention;

[0030] Figure 7 It is a schematic cross-sectional view of the heat exchange tube of the present invention.

[0031] The reference numerals are recorded as follows: 1. first cylinder; 2. second cylinder; 3. heat exchange tube bundle; 31. finned heat exchange tube; 32. T-type heat exchange tube; 33. longitudinal groove tube; 4. filling block; 5. oil storage chamber; 6. air suction baffle; 7. liquid inlet pipe; 8. air outlet pipe; 9. capillary tube; 10. oil outlet pipeline; 11. mounting plate; 12. gas passage; 13. liquid passage. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0033] like Figures 1 to 7 As shown, the present invention discloses a high-efficiency oil return kettle evaporator, comprising a first barrel 1 and a second barrel 2, the first barrel 1 and the second barrel 2 are connected to each other, a heat source inlet and a heat source outlet are arranged on the second barrel 2, a liquid inlet pipe 7 is arranged at the lower end of the first barrel 1, and an air outlet pipe 8 is arranged at the upper end, a heat exchange tube bundle 3 arranged along the axial direction is arranged in the first barrel 1, the heat source flows in the heat exchange tube bundle 3, that is, the heat source is in the tube side, and the side and upper part of the heat exchange tube bundle 3 are reserved with space, and also includes a filling block 4, the filling block 4 does not react or dissolve with the heat pump working medium and the lubricating oil, and the filling block 4 can reduce the kettle evaporator. The dead space in the generator is reduced to reduce the filling amount of the working fluid. The filling block 4 is arranged along the axial direction of the first cylinder 1. The filling blocks 4 are symmetrically arranged on both sides of the first cylinder 1, which will not affect the flow distance of the working fluid and the lubricating oil when the working fluid flows upward, and ensure the separation effect of the working fluid and the lubricating oil. The outer side of the filling block 4 fits with the inner wall of the first cylinder 1 to reduce the gap between the filling block 4 and the inner wall of the first cylinder 1. The inner side of the filling block 4 corresponds to the heat exchange tube bundle 3. A liquid passage 13 for the working fluid to pass through is provided between the filling block 4 and the heat exchange tube bundle 3, and an oil separation device is provided on the filling block 4 on at least one side. The working medium enters the shell side of the first cylinder 1 through the liquid inlet pipe 7, the heat exchange tube bundle 3 is immersed in the working medium liquid, the working medium liquid is heated and boiled between the heat exchange tube bundles 3, the gas-liquid two-phase working medium flows upward, the gas-liquid two-phase is separated in the upper space of the heat exchange tube bundle 3, the gaseous working medium is discharged from the gas outlet pipe 8, and the liquid working medium flows downward from the liquid passage 13 on the side of the heat exchange tube bundle 3 and enters the bottom of the heat exchange tube bundle 3. The working medium forms a circulating flow in the shell side by relying on the density difference and the liquid static pressure head.

[0034] Furthermore, the heat exchange tube bundle 3 uses high-efficiency heat exchange tubes on both sides, and the tubes are in the form of longitudinal groove tubes 33. The internal longitudinal grooves can increase the turbulence of the fluid, making the heat transfer between the liquid and the tube wall more effective, improving the heat transfer efficiency, improving the fluid distribution, and making the fluid flow more evenly in the heat exchange tube, avoiding the situation where the flow rate is too high or too low in the local area. According to the position of the heat exchange tube, different structures are used outside the tube, among which the full liquid area submerged by the liquid level adopts T-type heat exchange tubes 32 to enhance boiling heat transfer, and the heat exchange tubes above the liquid level adopt finned heat exchange tubes 31 to enhance gas heat exchange, wherein the finned heat exchange tubes 31 are arranged in two rows, and different types of high-efficiency heat exchange tube bundles are arranged by partitioning to enhance the overall heat exchange effect of the heat exchanger.

[0035] The distance between the filling block 4 and the heat exchange tube bundle 3 must ensure that it does not affect the heat exchange performance of the kettle evaporator. It can be calculated by using the maximum liquid flow rate. Calculate according to the circulation volume of three times the liquid supply volume to ensure that the liquid flow rate is less than 0.3m / s, which can effectively ensure the normal circulation of the liquid and will not drive bubbles into the bottom. For the most common R245FA or R1233ZDE working fluids, within the heat pump evaporation temperature (less than 100°C), the distance between the filling block 4 and the outermost side of the heat exchange tube bundle 3 is 22mm-38mm, that is, the width of the liquid passage 13 is 22mm-38mm. The calculation process is detailed in Formula 1 below.

[0036] (Formula 1)

[0037] Where, d is the distance between the filling block and the heat exchange tube bundle, mm; Q is the heat load, kW; -Specific enthalpy difference of heat pump working fluid entering and leaving the evaporator, kJ / kg; -Liquid phase density, kg / m3; v-limited speed, m / s; L-cylinder length, mm; H-liquid level, mm.

[0038] In this embodiment, a mounting plate 11 is provided on the inner wall of the first cylinder 1, and the filling block 4 is inserted on the mounting plate 11. The upper and lower ends of the filling block 4 are both provided with mounting plates 11, and the mounting plates 11 and the inner wall of the first cylinder 1 form a slot, and the filling block 4 is inserted into the slot along the length direction of the first cylinder 1, without welding, ensuring the service life of the kettle evaporator, and convenient installation.

[0039] In this embodiment, specifically, an arc section and a first inclined section are provided on the inner side of the filling block 4. The arc section is to ensure the size of the liquid passage 13 and the normal circulation of the working fluid. The liquid passage 13 is located between the arc section, the first inclined section and the heat exchange tube bundle 3. The inclination angle θ1 of the first inclined section is 71.5°-77°. When the inclination angle θ1 is less than 71.5°, the distance between the filling block 4 and the heat exchange tube bundle 3 is too small, which affects the normal circulation of the working fluid and the heat exchange effect. When the inclination angle θ1 is greater than 77°, the distance between the filling block 4 and the heat exchange tube bundle 3 is too large, resulting in the filling block 4 being unable to completely fill the invalid space of the first cylinder 1, and the filling amount of the working fluid is large, which increases the use cost.

[0040] In this embodiment, specifically, the material of the filling block 4 is polypropylene, and the filling block 4 is a solid structure. The solid structure has a higher compressive strength. The solid polypropylene can withstand a pressure of 40Mpa-60Mpa, and has no problem in long-term use at a temperature of 120°C. Polypropylene is less deformed by temperature. For a length of 100mm, a temperature rise of 50°C, and a deformation of 0.75mm, it is ensured that the circulation space of the working fluid in the kettle evaporator will not change significantly, and the working fluid is guaranteed to circulate normally and the heat exchange effect is guaranteed. In addition, the price of polypropylene is relatively low. Under the same volume, the cost of polypropylene is only about 8% of the cost of R245FA working fluid and only about 3% of the price of R1233zde working fluid. The filling block 4 made of relatively low-priced polypropylene is used to fill the invalid space in the kettle evaporator, which reduces the amount of working fluid and saves the cost of use. Further, the filling block 4 made of polypropylene is easy to shape, and there is no need for secondary welding in the kettle heat exchanger. It is easy to install and ensures the service life of the kettle evaporator.

[0041] In this embodiment, an air intake baffle 6 is installed in the first cylinder 1, and the air intake baffle 6 is located above the heat exchange tube bundle 3. A gas passage 12 is formed between the air intake baffle 6 and the second inclined section of the filling block 4. The air intake baffle 6 is mainly used to avoid the problem of air intake with liquid or air intake with foam caused by excessive local flow rate, and can make the air flow inside the container more uniform. Among them, the gas flow rate of the gas passage 12 is calculated according to the separation speed of the gas-liquid two phases. Specifically, it is calculated according to the gas flow rate being lower than the working medium settling speed. The specific calculation process adopts the existing technology and will not be repeated here.

[0042] Furthermore, the inclination angle θ2 of the second inclined section at the upper part of the filling block 4 is 117.5°-130°. Gas and liquid are separated here, and the liquid flows downward along the second inclined section after separation, and the gas flows upward. When the inclination angle θ2 is less than 117.5°, the cross-sectional area of ​​the gas passage 12 is small, which affects the flow of the gas phase working medium. When the inclination angle θ2 is greater than 130°, the cross-sectional area of ​​the gas passage 12 is large, which affects the effect of gas-liquid separation.

[0043] In an optional embodiment, the filling block 4 is a hollow or airbag structure, and the interior of the filling block 4 is connected to the air outlet pipe 8, so that the pressure inside and outside the filling block 4 is equalized, further reducing the cost of the filling block 4. The hollow or airbag structure is also suitable for working fluids or working conditions with stricter material requirements, and the material of the filling block 4 can be polytetrafluoroethylene.

[0044] In this embodiment, specifically, the oil separation device includes an oil storage chamber 5, a capillary tube 9 and an oil outlet pipeline 10. A plurality of capillary tubes 9 are provided, one end of each of the capillary tubes 9 is connected to the liquid passage 13, and the other end is connected to the oil storage chamber 5. One end of the oil outlet pipeline 10 is connected to the oil storage chamber 5, and the other end extends out of the first cylinder 1. By utilizing the difference in wettability and tension between the working medium and the oil, it is found through experiments that the lubricating oil is more likely to rise along the capillary tube 9 and enter the oil storage chamber 5 due to the capillary phenomenon, thereby achieving the separation of the lubricating oil and the working medium, reducing the content of the working medium in the lubricating oil in the oil return pipeline, ensuring the lubrication effect on the compressor in the unit, and ensuring the service life of the compressor.

[0045] The capillary tube 9 needs to be different according to the type and viscosity of the lubricating oil. The diameter of the capillary tube 9 is 1mm-2mm and the length is set to be more than 100mm, which has a better separation effect. The material of the capillary tube 9 can be ceramic or porous fiber to ensure the diversion effect of the lubricating oil.

[0046] Furthermore, a valve is installed on the oil outlet pipeline 10, and the return oil volume is adjusted by the valve to avoid excessive return oil volume causing the working fluid to be directly sucked into the oil storage chamber 5, affecting the separation effect of the lubricating oil and the working fluid; it also avoids the problem of too high oil level in the oil storage chamber 5 caused by too small oil output.

[0047] Furthermore, the capillary tube 9 is inclined, and the inlet height of the capillary tube 9 at the liquid passage 13 is less than the outlet height of the capillary tube 9 at the oil storage chamber 5. The inclination direction of the capillary tube 9 corresponds to the flow direction of the gas phase working medium, so that the lubricating oil in the gas phase working medium can enter the capillary tube 9 more smoothly, further improving the separation effect of the lubricating oil and the working medium.

[0048] In this embodiment, the oil separator is arranged on the filling block 4 on one side, which reduces the processing difficulty and saves costs. There are multiple oil separators, and the multiple oil separators are arranged along the axial intervals of the first cylinder 1, wherein the oil separators are evenly arranged in the axial direction of the first cylinder 1 at a spacing of 800mm-1000mm, further improving the separation effect of the working medium and the lubricating oil. Among them, the oil storage chamber 5 can be formed by folding and welding a steel sheet, and a capillary hole is opened on the side to connect the capillary tube 9, and a hole is opened on the bottom of the opposite side to connect the oil outlet pipeline 10. After the oil separator is manufactured as a whole, it is shaped together with the filling block 4 to ensure the firmness of the overall structure and reduce the difficulty of installation.

[0049] In an optional embodiment, oil separation devices are provided on the filling blocks 4 on both sides to further improve the separation effect of the lubricating oil and the working medium.

[0050] Take the top condenser evaporator of the heat pump distillation project of the methanol tower as an example.

[0051] Related parameters: tower top pressure is normal pressure, tower top gas temperature is 65℃, tower top load is 5000kw.

[0052] A kettle evaporator is used, with methanol gas condensing in the tube and R245FA evaporating in the shell. The diameter of the first cylinder 1 is 2000mm, the diameter of the second cylinder 2 is 1100mm, the overall length of the kettle evaporator is 7m, and the heat exchange area is 332m 2 The heat exchange tube bundle 3 is a stainless steel heat exchange tube, and the number of heat exchange tubes is 790.

[0053] In the prior art, the working fluid filling amount of the above-mentioned kettle evaporator is 8000kg, and the working fluid filling amount of the high-efficiency oil return kettle evaporator of the present invention is 4500kg, which saves 3500kg of working fluid and reduces the working fluid filling amount by 43.8%.

[0054] The total cost of the existing kettle evaporator is approximately: the heat exchanger cost is 500,000, the working fluid filling cost is 640,000, and the total cost is 1.14 million.

[0055] The total cost of the high-efficiency oil return kettle evaporator of the present invention is: the cost of the heat exchanger is 520,000, the cost of the working fluid filling is 360,000, and the total cost is 880,000. The total cost is saved by 260,000, accounting for 22.8% of the total cost.

[0056] The present invention ensures the effect of working medium circulation heat exchange, reduces the invalid space in the kettle evaporator, reduces the filling amount of the working medium, saves the high cost of the working medium, and reduces the content of the working medium in the lubricating oil collection through the oil separator, improves the oil return effect and the oil return amount, and ensures the normal operation of the heat pump unit.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-efficiency oil return kettle evaporator, comprising a first cylinder (1) and a second cylinder (2), wherein the first cylinder (1) and the second cylinder (2) are connected, a heat source inlet and a heat source outlet are provided on the second cylinder (2), a liquid inlet pipe (7) is provided at the lower end of the first cylinder (1), and an air outlet pipe (8) is provided at the upper end, and an axially arranged heat exchange tube bundle (3) is provided in the first cylinder (1), characterized in that: The heat exchange tube bundle (3) further comprises a filling block (4), wherein the filling block (4) is arranged along the axial direction of the first cylinder (1), the filling blocks (4) are symmetrically arranged on both sides of the first cylinder (1), the outer side of the filling block (4) is in contact with the inner wall of the first cylinder (1), the inner side of the filling block (4) corresponds to the heat exchange tube bundle (3), a liquid passage (13) for the working medium to pass through is provided between the filling block (4) and the heat exchange tube bundle (3), and an oil separation device is provided on at least one side of the filling block (4), the oil separation device comprising an oil storage chamber (5), a capillary tube (9) and an oil outlet pipeline (10), wherein a plurality of the capillary tubes (9) are provided, one end of each of the capillary tubes (9) is in communication with the liquid passage (13) and the other end is in communication with the oil storage chamber (5), one end of the oil outlet pipeline (10) is in communication with the oil storage chamber (5) and the other end extends out of the first cylinder (1), the capillary tube (9) is arranged obliquely, and the inlet height of the capillary tube (9) at the liquid passage (13) is smaller than the outlet height of the capillary tube (9) at the oil storage chamber (5).

2. The high-efficiency oil return kettle evaporator according to claim 1 is characterized in that: The oil separators are provided in plurality, and the plurality of oil separators are arranged at intervals along the axial direction of the first cylinder (1).

3. The high-efficiency oil return kettle evaporator according to claim 1 is characterized in that: A mounting plate (11) is provided on the inner wall of the first cylinder (1), the mounting plate (11) and the inner wall of the first cylinder (1) forming a slot, and the filling block (4) is inserted into the slot.

4. The high-efficiency oil return kettle evaporator according to claim 1 is characterized in that: An arc section and a first inclined section are provided on the inner side of the filling block (4); the liquid passage (13) is located between the arc section, the first inclined section and the heat exchange tube bundle (3); and an inclination angle θ1 of the first inclined section is 71.5°-77°.

5. The high-efficiency oil return kettle evaporator according to claim 1 or 4, characterized in that: An air intake baffle (6) is installed in the first cylinder (1), the air intake baffle (6) is located above the heat exchange tube bundle (3), and a gas passage (12) is formed between the air intake baffle (6) and the second inclined section of the filling block (4).

6. The high-efficiency oil return kettle evaporator according to claim 5, characterized in that: The inclination angle θ2 of the second inclination section is 117.5°-130°.

7. The high-efficiency oil return kettle evaporator according to claim 1 is characterized in that: The filling block (4) is a solid structure; or, the filling block (4) is a hollow or airbag structure, and the interior of the filling block (4) is in communication with the air outlet pipe (8).

8. The high-efficiency oil return kettle evaporator according to claim 1 or 7, characterized in that: The material of the filling block (4) is polypropylene or polytetrafluoroethylene.

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