CN101464078A - High-efficiency external evaporation heat exchanger with perturbation and safe oil return - Google Patents

Abstract

The invention discloses a high-efficiency external evaporative heat exchanger with disturbance and safe oil return, and aims to provide an external evaporative heat exchanger capable of preventing liquid hammer accidents, enhancing heat exchange effect, and safely returning oil. The first head and the first tube sheet are separated into the second flow chamber and the liquid collection chamber by the first partition, and the second head and the second tube sheet are separated into the first flow chamber and the liquid collection chamber by the second partition. In the third distribution chamber, a plurality of vertical heat exchange flat tubes placed side by side are arranged in the lower space of the shell, a part of the vertical heat exchange flat tubes communicates with the second distribution chamber and the first distribution chamber, and the other part of the vertical heat exchange flat tubes communicates The second distributing chamber and the third distributing chamber; the horizontal heat exchange flat tube is arranged in the upper space of the casing and communicates with the liquid collection chamber and the third distributing chamber. The space in the shell of the evaporation heat exchanger of the present invention is increased and unobstructed, the rising resistance of the air bubbles outside the heat exchange flat tube is reduced, the air bubbles are easy to rise rapidly, and the heat exchange effect is enhanced. Avoid gas entrained liquid droplets, to prevent liquid impact accidents.

Description

High Efficiency Out-of-Tube Evaporation Heat Exchanger with Disturbance and Safe Oil Return

technical field

The invention relates to an external evaporating heat exchanger for cooling refrigerant in a condensing pipe and carrying refrigerant in a cooling pipe used in a refrigeration system.

Background technique

In the industrial and commercial fields, the shell-and-tube evaporative heat exchangers used in existing refrigeration systems mainly have the following disadvantages:

1. The shell and tube outside the tube of the evaporative heat exchanger is filled with refrigerant according to a certain liquid level, and the inside of the shell forms a mist due to disturbance. When it is easy to entrain liquid droplets, it will cause liquid hammer accidents of the compressor.

2. For the working medium that absorbs heat and evaporates in the large space between the shell and tube, the lubricating oil is either suspended on the surface of the liquid or deposited under the liquid, and the oil is carried by the compressor to suck the gas, so the lubricating oil cannot return to the compression in time and smoothly machine, the amount of lubricating oil in the compressor cannot be guaranteed.

3. If the heat exchange tube used in the evaporative heat exchanger is longer, a support plate needs to be installed to reduce the heat exchange area. More material and more weight.

4. The evaporative heat exchanger adopts the structure of staggered arrangement of circular heat exchange tubes, which is not conducive to the rise of bubbles and affects the heat exchange effect.

In the cascade refrigeration system for freezing, refrigerating and fresh-keeping foods such as supermarkets, the heat exchangers for cooling and condensing low-temperature circulating refrigerants, cooling medium-temperature circulating refrigerants, and high-temperature circulating refrigerants for external evaporation and heat exchange should be designed for low-temperature cooling. The thermodynamic performance characteristics of circulating refrigerants and medium-temperature circulating refrigerants, such as natural refrigerant CO ₂ , has low viscosity and low flow resistance, so it is necessary to use an external evaporative heat exchanger with micro-channel heat exchange tubes to save metal materials , to reduce space and weight.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide an external evaporation heat exchanger capable of preventing liquid hammer accidents, enhancing heat exchange effect, reducing heat exchange area and having good oil return performance.

The present invention realizes through following technical scheme:

A high-efficiency external tube evaporative heat exchanger with disturbance and safe oil return is characterized in that it includes a cylindrical shell, a first head, a first tube sheet, a second head, a second tube sheet, A plurality of vertical heat exchange flat tubes and horizontal heat exchange flat tubes placed side by side, the vertical heat exchange flat tubes and horizontal heat exchange flat tubes are respectively provided with a plurality of internal passages, the two ends of the shell are respectively connected to the first One tube sheet and the second tube sheet are welded, the first tube sheet and the second tube sheet are respectively provided with horizontal heat exchange flat tube holes and a plurality of vertical heat exchange flat tube holes, the first tube sheet and the second tube sheet The heads are connected by connecting bolts and gaskets, and the first head and the first tube sheet are separated into a second distribution chamber and a liquid collection chamber by a first partition, and the liquid collection chamber is connected with a The outlet of the first working medium liquid is connected; the second tube plate and the second head are connected by connecting bolts and gaskets, and the second head and the second tube plate are separated into the first part by the second partition plate A diversion chamber and a third diversion chamber, the outside of the first diversion chamber is connected with a first working gas inlet connection; a plurality of vertical heat exchange flat tubes placed side by side are arranged in the lower space of the shell, and a part of the vertical heat exchange flat tubes The tube passes through the vertical heat exchange flat tube holes on the first tube sheet and the second tube sheet to communicate with the second flow chamber and the first flow chamber, and another part of the vertical heat exchange flat tube passes through the first tube sheet and the second tube The vertical heat exchange flat tube hole on the plate communicates with the second distribution chamber and the third distribution chamber; the horizontal heat exchange flat tube is arranged in the upper space of the shell, and the horizontal heat exchange flat tube passes through the first tube sheet and the second tube sheet The horizontal heat exchange flat tube holes are connected to the liquid collection chamber and the third distribution chamber; each vertical heat exchange flat tube is respectively welded to the vertical heat exchange flat tube holes on the first tube sheet and the second tube sheet, and the horizontal heat exchange flat tube holes are connected to each other. The heat flat tubes are respectively welded to the horizontal heat exchange flat tube holes on the first tube plate and the second tube plate; the upper end of the shell is connected with the outlet pipe of the second working medium gas, and the lower end of the shell is connected with the second working medium liquid Imports take over.

A second working fluid connecting pipe is connected to the lower end of the housing, the end of the second working fluid connecting pipe communicates with the injection chamber, one end of the bell-shaped diffuser communicates with the injection chamber, and the other end communicates with the injection chamber. It is connected to the lower end of the housing, the end of the second working medium high-pressure liquid connecting pipe is placed in the injection chamber, and a nozzle connected to the second working medium high-pressure liquid connecting pipe is arranged at a position corresponding to the throat of the diffusion pipe .

One end of the oil return pipe is connected to the outlet pipe of the second working medium gas through the oil return control valve, the other end is placed in the casing, and the end reaches the uppermost position of the vertical heat exchange flat pipe, and the end of the oil return pipe extending into the casing is fixed There is a temperature sensor.

Each internal channel of each vertical heat exchange flat tube is provided with multiple heat exchange fins, and each internal channel of the horizontal heat exchange flat tube is provided with multiple heat exchange fins.

The housing is welded to the outlet pipe of the second working fluid gas, the outlet pipe of the second working fluid gas is welded to the oil return pipe, the housing is welded to the oil return pipe, and the liquid inlet pipe of the second working medium is connected to the housing. The welding connection is the welding connection between the diffusion pipe and the casing, and the welding connection between the second working fluid connection pipe and the casing.

The present invention has following technical effect:

1. The high-efficiency outer-tube evaporative heat exchanger with disturbance and safe oil return of the present invention adopts a structure combining vertical heat-exchange flat tubes and horizontal heat-exchange flat tubes, and the vertical heat-exchange flat tubes placed side by side make the tubes Compared with the space between the original staggered circular tubes, the space between them is significantly increased and unobstructed. The rising resistance of the air bubbles formed outside the heat exchange flat tubes is reduced, making it easy for the air bubbles to rise rapidly, and the heat exchange effect is enhanced. The horizontal heat exchange flat tube placed in the upper space of the shell can block the mist formed by the disturbance in the shell, avoid the entrainment of liquid droplets in the gas, and prevent the occurrence of liquid hammer accidents.

2. The high-pressure liquid of the second working medium enters the connecting pipe of the high-pressure fluid of the second working medium, and is sprayed out at high speed through the nozzle, forming a vacuum at the entrance of the throat of the diffusion pipe, and the low-pressure liquid coming from the connecting pipe of the second working medium liquid is Inhalation, the two fluids mix and exchange momentum at the throat, which increases the kinetic energy of the transported liquid, and finally converts most of the kinetic energy into pressure energy through the diffuser tube and enters the shell. Due to the ejection of high-pressure fluid, the working medium in the shell is continuously flowing, which disturbs the working medium in the shell, and quickly takes away the air bubbles formed on the outer surface of the heat exchange flat tube, which accelerates the formation of air bubbles and strengthens the Heat exchange effect, the evaporation heat exchange of the same heat exchange heat can reduce the heat exchange area, reduce the size of the heat exchanger, reduce the cost and save energy.

3. An oil return pipe is connected to the outlet pipe of the second working medium, and the oil return pipe extends to the control liquid level height of the second working medium in the casing, and the end of the oil return pipe extending into the casing is provided with a temperature sensor, which can Using the difference in thermal conductivity of the second working medium liquid, gas and lubricating oil to control the oil return and liquid supply, the height of the liquid level can be precisely controlled, effectively preventing the liquid from entering the compressor and preventing the liquid shock accident of the compressor. occur. At the same time, good oil return can ensure the reliable operation of the system.

4. The internal channels of the vertical heat exchange flat tubes and horizontal heat exchange flat tubes are processed into structures with various inner fins, which can strengthen the heat exchange of the first working fluid in the channels.

5. The shell is welded to the first tube plate, the second tube plate, the second working medium gas outlet connection pipe, the second working medium liquid inlet connection pipe, the diffusion pipe, and the second working medium liquid connecting pipe respectively, which can effectively To prevent the leakage of the second working fluid.

6. The artificial flow heat exchange between the first working substance and the second working substance has good heat exchange effect.

7. Due to the rigidity of the heat exchange flat tube itself, there will be no sagging deformation, so there is no support plate, which does not affect the heat exchange area, small size and light weight.

Description of drawings

Fig. 1 is the schematic diagram of the high-efficiency external tube evaporative heat exchanger with disturbance and safe oil return of the present invention;

Fig. 2 is a schematic diagram of the structure of the first head;

Fig. 3 is a schematic diagram of the structure of the second head;

Fig. 4 is a schematic diagram of the structure of the first tube sheet;

Fig. 5 is A-A sectional view;

Fig. 6 is a B-B sectional view.

Detailed ways

Fig. 1 is a schematic diagram of the high-efficiency external tube evaporation heat exchanger with disturbance and safe oil return of the present invention, including a cylindrical shell 5, a first head 2, a first tube sheet 4, a second head 11, The second tube sheet 12, a plurality of vertical heat exchange flat tubes 8 and horizontal heat exchange flat tubes 9 placed side by side. Both the vertical heat exchange flat tubes 8 and the horizontal heat exchange flat tubes 9 are extruded from aluminum, and a plurality of tiny internal passages are formed inside the vertical heat exchange flat tubes 8 and the horizontal heat exchange flat tubes 9 . Both ends of the casing 5 are welded to the first tube sheet 4 and the second tube sheet 12 respectively. The schematic diagram of the first tube sheet is shown in Figure 4, the first tube sheet 4 is respectively provided with connecting bolt holes 27, horizontal heat exchange flat tube holes 28 and a plurality of vertical heat exchange flat tube holes 29, the second tube sheet 12 has the same structure as the first tube sheet 4, and the second tube sheet 12 is also respectively provided with connecting bolt holes, horizontal heat exchange flat tube holes and a plurality of vertical heat exchange flat tube holes.

The schematic diagram of the first head is shown in Figure 2. On the first head, there are a plurality of connecting bolt holes 19 corresponding to the first tube plate evenly distributed along the circumference. The first tube plate 4 and the first head 2 They are connected by the connecting bolt 3 passing through the connecting bolt hole 27 on the first tube plate and the connecting bolt hole 19 on the first head and the gasket. The first head 2 and the first tube sheet 4 are separated into a second flow chamber 22 and a liquid collection chamber 20 by a first partition 21 , and the liquid collection chamber 20 is connected with a first working fluid outlet connection pipe 1 outside. The schematic diagram of the second head is shown in Figure 3. On the second head, there are a plurality of connecting bolt holes 23 corresponding to the second tube plate evenly distributed along the circumference. The second tube plate 12 and the second head 11 The spaces are connected by connecting bolts and gaskets passing through the connecting bolt holes on the second tube plate and the connecting bolt holes on the second head. The second head 11 and the second tube sheet 12 are separated into a first flow distribution chamber 26 and a third flow distribution chamber 24 by a second partition plate 25 , and the first flow distribution chamber 26 is connected with a first working gas inlet connection pipe 10 outside.

A plurality of vertical heat exchange flat tubes 8 placed side by side are arranged in the lower space of the shell 5, and the plurality of vertical heat exchange flat tubes 8 placed side by side are divided into two parts, and a part of the vertical heat exchange flat tubes 8-1 passes through The vertical heat exchange flat tube holes on the first tube plate and the second tube plate communicate with the second flow chamber 22 and the first flow chamber 26, and another part of the vertical heat exchange flat tubes 8-2 passes through the first tube plate and the first tube plate. The vertical heat exchange flat tube holes on the second tube plate communicate with the second distribution chamber 22 and the third distribution chamber 24 . The horizontal heat exchange flat tubes 9 are arranged in the upper space of the shell, and the horizontal heat exchange flat tubes 9 pass through the horizontal heat exchange flat tube holes on the first tube sheet and the second tube sheet to communicate with the liquid collection chamber 20 and the third distribution chamber 24 . Each vertical heat exchange flat tube is respectively welded to the vertical heat exchange flat tube holes on the first tube sheet and the second tube sheet, and the horizontal heat exchange flat tubes are respectively welded to the horizontal heat exchange tube holes on the first tube sheet and the second tube sheet. Hot flat tube hole welding. The upper end of the casing 5 is connected with a second working medium gas outlet connecting pipe 6 , and the lower end of the casing 5 is connected with a second working medium liquid inlet connecting pipe 14 .

In order to form a disturbance to the fluid in the housing, a second working fluid connecting pipe 13 is connected to the lower end of the housing 5, and the end of the second working fluid connecting pipe 13 communicates with the injection chamber 31. One end of 16 communicates with the injection chamber 31, and the other end is connected with the lower end of the casing 5. The end of the second working medium high-pressure liquid connection pipe 18 is placed in the injection chamber 31, and the throat part of the diffusion pipe 17 is provided with a nozzle 15 connected to the second working medium high-pressure liquid connection pipe 18 .

One end of the oil return pipe 7 is connected to the second working medium gas outlet connection pipe 6 through the oil return control valve 30, the other end is placed in the casing 5, and the end reaches the uppermost position of the vertical heat exchange flat pipe 8. The oil return pipe 7 extends A temperature sensor is fixed at the end of the housing.

In order to enhance the heat exchange effect in the channel, a plurality of heat exchange fins are arranged in each inner channel of each vertical heat exchange flat tube, and a plurality of heat exchange fins are arranged in each inner channel of each horizontal heat exchange flat tube.

In order to prevent the leakage of the second working fluid, the casing is welded to the outlet pipe of the second working fluid, the outlet pipe of the second working fluid is welded to the oil return pipe, and the casing is welded to the oil return pipe. The liquid inlet connection pipe is welded to the shell, the diffuser is welded to the shell, and the second working fluid connection pipe is welded to the shell.

When assembling, after the shell 5 is welded with the first tube sheet 4 and the second tube sheet 12, the horizontal heat exchange flat tube is inserted through the horizontal heat exchange flat tube hole 28 on the first tube sheet 4, and passes through the second tube sheet The horizontal heat exchange flat tube holes on the plate communicate with the liquid collection chamber 20 and the third flow distribution chamber 24, and the horizontal heat exchange flat tubes are welded to the horizontal heat exchange flat tube holes. The vertical heat exchange flat tubes are inserted through the vertical heat exchange flat tube holes 29 on the first tube sheet 4, and pass through the vertical heat exchange flat tube holes on the second tube sheet 12, part of the vertical heat exchange flat tubes 8-1 communicates with the second distribution chamber 22 and the first distribution chamber 26, another part of the vertical heat exchange flat tube 8-2 communicates with the second distribution chamber 22 and the third distribution chamber 24, and connects the vertical heat exchange flat tube with the vertical Direct heat exchange flat tube hole welding. Afterwards, the connecting bolt holes on the first tube sheet 4 are aligned with the connecting bolt holes on the first head, tightly connected by the connecting bolts, and sealed by a gasket, and the connecting bolt holes on the second tube sheet 12 are aligned with the connecting bolt holes on the first head. The connecting bolt holes on the second head are aligned, tightly connected by connecting bolts, and sealed by a gasket. Afterwards, the casing 5 is welded with the second working medium gas outlet connecting pipe 6, the oil return pipe 7, the second working medium liquid inlet connecting pipe 14, the diffusion pipe 16, and the second working medium liquid connecting pipe 13 to complete the assembly process.

The heat exchange process of the present invention will be described below by taking the R290/CO ₂ cascade refrigeration cycle as an example. For the R290/CO ₂ cascade refrigeration cycle, the first working fluid is CO ₂ and the second working fluid is R290. When in use, the R290 fluid from the R290 expansion valve enters the casing 5 through the second working medium liquid inlet connection pipe 14, and the liquid level height of the second working medium R290 liquid reaches the upper end of the horizontal heat exchange flat tube, so that the horizontal The heat exchange flat tubes are submerged in R290 liquid. The first working medium CO ₂ gas from the CO ₂ compressor enters the first split flow chamber 26 of the second head through the first working medium gas inlet connecting pipe 10, and enters the passage in the vertical heat exchange flat tube 8-1, It exchanges heat with the second working substance R290, releases heat, cools and condenses, then enters the second distribution chamber 22 of the first head, flows out from the second distribution chamber 22 of the first head, and enters the second partition separated by the second partition 25 The channel in the vertical heat exchange flat tube 8-2, after further cooling and condensing to release heat, enters the third flow distribution chamber 24 of the second head, enters the channel in the horizontal heat exchange flat tube 9 from the third flow distribution chamber 24, and further After heat release, it becomes liquid and enters the liquid collection chamber 20 of the first head, and the first working medium CO ₂ liquid enters the expansion valve of the first working medium CO ₂ through the first working medium liquid outlet connection 1 of the first head. The second working medium R290 absorbs the heat released by the first working medium _CO2 in the vertical heat exchange flat tube and the horizontal heat exchange flat tube in the shell and evaporates into a gas, then returns to the R290 compressor through the second working medium gas outlet connection 6.

The second working medium high-pressure fluid connecting pipe 18 is connected to the outlet of the second working medium R290 condenser, and part of the high-pressure R290 liquid from the R290 condenser is sprayed out at a high speed through the nozzle 15 through the second working medium high-pressure fluid connecting pipe 18. At the inlet of the throat, the surrounding R290 gas is swept away by the jet to form a vacuum, and the low-pressure R290 liquid from the second working fluid connection pipe 13 is sucked in, and the two fluids are mixed in the throat and exchange momentum. Increase the kinetic energy of the transported R290 liquid, and finally convert most of the kinetic energy into pressure energy through the diffusion tube 16, and then enter the housing 5. Due to the ejection of the high-pressure R290 fluid, the second working medium R290 in the housing will not stop The ground flow disturbs the R290 working medium in the shell, quickly takes away the bubbles formed on the outer surface of the heat exchange flat tube, accelerates the formation of bubbles, and strengthens the heat exchange effect. The heat exchange area can be reduced, the size of the heat exchanger can be reduced, the cost can be reduced, and energy can be saved.

The oil return pipe 7 protrudes to the control liquid level of the second working fluid R290 in the shell, and the end of the oil return pipe 7 protruding into the shell is provided with a temperature sensor. The difference in thermal conductivity between gas and lubricating oil controls oil return and liquid supply. If the temperature sensor senses oil, the oil return control valve 30 is opened by the controller, and the lubricating oil layer on the liquid surface passes through the oil return pipe 7, passes through the oil return control valve 30 and the R290 gas at the second working gas outlet 6 , is sucked back to the compressor, which can effectively prevent the R290 liquid from entering the R290 compressor and prevent the occurrence of liquid hammer accidents of the R290 compressor. Reliable operation. If the temperature sensor senses the R290 liquid, the oil return control valve 30 is closed by the controller, the opening degree of the R290 expansion valve is reduced, and the liquid supply of R290 is reduced. If the temperature sensor senses R290 gas, the oil return control valve 30 is opened by the controller, and the opening degree of the R290 expansion valve is increased to increase the liquid supply of R290. Through the structural design of the oil return pipe, temperature sensor and oil return control valve, the height of the liquid level can be precisely controlled.

The internal channels of the vertical heat exchange flat tubes 8 and the horizontal heat exchange flat tubes 9 can be processed into structures with various inner fins to enhance the heat exchange of the first working substance CO ₂ in the channels. The vertical heat exchange flat tubes 8 arranged side by side, the space between the tubes is obviously increased compared with the space between the original staggered round tubes, and the space is unobstructed. The rising resistance of the air bubbles formed outside the heat exchange flat tubes is reduced, and the air bubbles are easy to rise rapidly. Enhanced heat transfer. The horizontal heat exchange flat tube 9 placed in the upper space of the shell can block the mist formed in the shell due to disturbance, causing the gas to entrain liquid droplets, which are sucked back to the compressor through the gas outlet of the second working medium to prevent liquid shock Accidents happen.

The first working substance _CO in the embodiment of the present invention has three processes, and the first partition in the first head and the second partition in the second head can be adjusted according to the size of different heat transfers. Position, adjust the number of separated vertical heat exchange flat tubes, and set different flow numbers. By changing the size and number of channels of the horizontal heat exchange flat tube 9 , adjusting the upper and lower positions of the horizontal heat exchange flat tube 9 , the heat exchange area of the last pass is adjusted.

The invention has simple structure and is convenient to manufacture, install and maintain. It is especially suitable for the characteristics of condensation, evaporation and heat exchange of the R290/CO ₂ cascade refrigeration cycle with relatively large cooling capacity. The proposal of the present invention is one of the key technologies to make the R290/CO ₂ cascade refrigeration cycle move towards practical application.

Although the disclosed high-efficiency external tube evaporative heat exchanger with disturbance and safety oil return has been specifically described with reference to the embodiments, the above-described embodiments are illustrative and not restrictive, without departing from the present invention All changes and modifications within the spirit and scope of the invention are within the scope of the invention.

Claims (5)

1. A high-efficiency external tube evaporative heat exchanger with disturbance and safe oil return, characterized in that it includes a cylindrical shell, a first head, a first tube sheet, a second head, and a second tube plate, a plurality of vertical heat exchange flat tubes and horizontal heat exchange flat tubes placed side by side, the vertical heat exchange flat tubes and horizontal heat exchange flat tubes are respectively provided with a plurality of internal passages, and the two ends of the shell are respectively Welded with the first tube sheet and the second tube sheet, the first tube sheet and the second tube sheet are respectively provided with horizontal heat exchange flat tube holes and a plurality of vertical heat exchange flat tube holes, the first tube sheet It is connected with the first head through connecting bolts and gaskets, and the first head and the first tube sheet are separated into a second distribution chamber and a liquid collection chamber by a first partition, and the outside of the liquid collection chamber Connected with the first working fluid outlet connection; the second tube plate and the second head are connected by connecting bolts and gaskets, and the second head and the second tube plate are separated by a second partition The first flow chamber and the third flow chamber are connected to the outside of the first flow chamber. The first working gas inlet connection pipe is connected; a plurality of vertical heat exchange flat tubes placed side by side are arranged in the lower space of the shell, and some of them are vertically exchanged. The heat flat tubes pass through the vertical heat exchange flat tube holes on the first tube sheet and the second tube sheet to communicate with the second distribution chamber and the first distribution chamber, and another part of the vertical heat exchange flat tubes passes through the first tube sheet and the second tube sheet. The vertical heat exchange flat tube hole on the second tube plate communicates with the second flow chamber and the third flow chamber; the horizontal heat exchange flat tube is arranged in the upper space of the shell, and the horizontal heat exchange flat tube passes through the first tube plate and the second tube The horizontal heat exchange flat tube holes on the plate communicate with the liquid collection chamber and the third distribution chamber; each vertical heat exchange flat tube is welded to the vertical heat exchange flat tube holes on the first tube plate and the second tube plate respectively, The horizontal heat exchange flat tubes are respectively welded to the horizontal heat exchange flat tube holes on the first tube plate and the second tube plate; the upper end of the shell is connected with the second working medium gas outlet connection pipe, and the lower end of the shell is connected with the second working Quality liquid inlet connection. 2. The high-efficiency external tube evaporative heat exchanger with disturbance and safe oil return according to claim 1, characterized in that a second working fluid liquid connection pipe is connected to the lower end of the shell, and the second working fluid The end of the liquid connection pipe communicates with the ejection chamber, one end of the flared diffuser pipe communicates with the ejection chamber, and the other end connects with the lower end of the housing, and the end of the second working medium high-pressure liquid connection pipe is placed in the chamber. In the injection chamber, a nozzle connected to the second working medium high-pressure liquid connecting pipe is arranged at a position corresponding to the throat of the diffusion pipe. 3. The high-efficiency external tube evaporative heat exchanger with disturbance and safe oil return according to claim 1 or 2, characterized in that one end of the oil return pipe is connected to the outlet of the second working medium gas through the oil return control valve, and the other One end is placed in the shell, the end reaches the uppermost position of the vertical heat exchange flat tube, and the end of the oil return pipe extending into the shell is fixed with a temperature sensor. 4. The high-efficiency external evaporative heat exchanger with disturbance and safe oil return according to claim 3, characterized in that, each internal channel of each vertical heat exchange flat tube is provided with a plurality of heat exchange fins , each internal channel of the horizontal heat exchange flat tube is provided with a plurality of heat exchange fins. 5. The high-efficiency external tube evaporative heat exchanger with disturbance and safe oil return according to claim 4, characterized in that the shell is welded to the second working fluid gas outlet connecting pipe, and the second working medium gas outlet connecting pipe is connected to the Welding connection between the oil return pipe, welding connection between the casing and the oil return pipe, welding connection between the second working fluid inlet connection pipe and the casing, welding connection between the diffusion pipe and the casing, the welding connection between the second working fluid liquid connection pipe and the Welded connections between shells.

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