CN113819669B - A low-temperature refrigeration device and method based on the gravity oil separation effect of carbon nanotubes - Google Patents

Abstract

The invention discloses a low-temperature refrigeration device and a low-temperature refrigeration method based on a carbon nano tube gravity oil separation effect, wherein the device is based on single-machine compression single-stage fractional condensation self-cascade refrigeration and comprises a compressor, a condenser, a gas-liquid separator, a capillary tube and a throttle valve; saturated liquid-phase high-temperature refrigerant in the gas-liquid separator enters a condensing evaporator through a throttling device to complete the evaporation process; meanwhile, saturated gas working refrigerant generated in the gas-liquid separator enters the condensing evaporator to finish the condensation process, enters the evaporator after being throttled by a capillary tube, and finally enters a compression cycle after low-temperature refrigerant exiting the evaporator is mixed with high-temperature refrigerant gas which finishes the evaporation process in the condensing evaporator; in the circulation process, a proper amount of carbon nano tubes are added to the refrigerant, so that the content of lubricating oil in the low-boiling-point refrigerant in the gas-liquid separator is greatly reduced, the capillary tube is prevented from being blocked by the lubricating oil, and meanwhile, the heat exchange performance of the refrigerant, the lubricating performance of the lubricating oil and the abrasion of a compressor can be improved.

Description

A low-temperature refrigeration device and method based on the gravity oil separation effect of carbon nanotubes

technical field

The invention relates to the field of refrigeration equipment, in particular to a low-temperature refrigeration device and method based on the gravity oil separation effect of carbon nanotubes.

Background technique

Since the discovery of carbon nanotubes in 1991, due to their unique structural characteristics, they have good heat transfer performance, singular electrical conductivity and excellent mechanical properties, which have attracted widespread attention from experts and scholars, and have shown great promise in various fields. Broad application prospects. Carbon nanotubes not only have some common characteristics of nanomaterials, but also have extremely high mechanical strength. They are used in lubricating oil additives in the field of lubrication to improve and enhance anti-wear properties. The porous structure, large specific surface area and light mass density of carbon nanotubes also make them exhibit good performance in adsorption.

In the self-cascading refrigeration system, after the refrigerants with different evaporation temperatures are condensed by the condenser, the low-temperature refrigerant is in a gaseous state, while the high-boiling point refrigerant has been condensed into a liquid state. At this time, the gas-liquid separator is set to make the two The refrigerant in the liquid state is separated, so that the liquid high-boiling point refrigerant is throttled and continues to condense the low-temperature refrigerant. However, at present, when the gas-phase low-boiling point refrigerant is separated, some lubricating oil droplets are often entrained. Seriously, these droplets enter the low-temperature pipeline, which will cause capillary blockage and seriously affect the operation of the system.

At present, in order to realize the high-efficiency separation of the gas-phase low-boiling point refrigerant and the lubricating oil in the gas-liquid separator of the low-temperature refrigeration system, the gas-liquid separator is mainly improved. It is still not obvious, so there is a need for a device and method capable of efficiently separating oil components in gas-phase low-boiling point refrigerants.

Contents of the invention

The purpose of the present invention is to solve the deficiencies of the prior art, and provide a low-temperature refrigeration device and method based on the gravity oil separation effect of carbon nanotubes.

In order to solve the above problems, the present invention adopts the following technical solutions:

A low-temperature refrigeration device based on the gravity oil separation effect of carbon nanotubes, including a compressor, a condenser, a gas-liquid separator, a throttle valve, a capillary tube, a condensing evaporator, an evaporator, and a filling port; wherein the outlet of the compressor is connected to the condensing The inlet of the condenser is connected, and the outlet of the condenser is connected to the inlet of the gas-liquid separator; the high-boiling point refrigerant channel of the gas-liquid separator is connected to the evaporation side channel of the condensing evaporator through a throttle valve; the low-boiling point refrigerant channel of the gas-liquid separator is connected to the The condensing side channel of the condensing evaporator is connected; the condensing side outlet of the condensing evaporator is connected to the inlet of the evaporator through a capillary tube; the evaporating side outlet of the condensing evaporator is connected to the outlet of the evaporator and connected to the inlet of the compressor; in the condenser A filling port is arranged between the gas-liquid separator and the gas-liquid separator, and the filling port is used for filling carbon nanotubes.

Further, it also includes a refrigerant, and the refrigerant is a self-cascading mixed refrigerant.

Further, the self-cascading mixed refrigerant includes one or a combination of high-boiling refrigerants, and one or a combination of low-boiling refrigerants; wherein the high-boiling refrigerants include R134A, R600A, R1234YF, R1234ZE (Z), R1234ZE(E), R142B and R22, low boiling point refrigerants include R23, R14, R1150, R290, R170, R125 and R32.

A low-temperature refrigeration method based on the gravity oil separation effect of carbon nanotubes, the refrigeration method is based on the above-mentioned refrigeration device, and the refrigeration method includes the following steps:

Step 1: The compressor stops working, and the set amount of carbon nanotubes is filled into the refrigeration device through the filling port;

Step 2: Start the compressor; carbon nanotubes and refrigerant are mixed into the condenser;

Step 3: After condensing in the condenser, a partially liquefied refrigerant is obtained; the high-boiling point refrigerant is condensed to form a liquid state after exothermic condensation, and the low-boiling point refrigerant remains in a gaseous state; due to the high viscosity of the lubricating oil, the carbon nanotubes have a migration mechanism , so carbon nanotubes absorb lubricating oil and deposit, and mix with liquid high-boiling point refrigerant;

Step 4: The partially liquefied refrigerant enters the gas-liquid separator for the separation process of gas-phase low-boiling point refrigerant and high-boiling point refrigerant; the separated high-boiling point refrigerant enters the evaporation side channel of the condensing evaporator through the throttle valve, and the low-temperature The refrigerant enters the condensing side channel of the condensing evaporator;

Step 5: In the condensing evaporator, the high-boiling point refrigerant containing lubricating oil and carbon nanotubes exchanges heat with the saturated gas-phase low-boiling point refrigerant, so that the high-boiling point refrigerant absorbs heat and evaporates to form steam, and the low-boiling point refrigerant releases heat Condensation becomes liquid; the high-boiling point refrigerant containing carbon nanotubes produces a large number of bubbles due to the heat transfer effect of boiling, and the carbon nanotubes are resuspended in the refrigerant under the action of bubbles generated during the boiling process, so that the carbon nanotubes are dispersed and the cycle process is avoided. Due to the deposition and agglomeration of carbon nanotubes, the condensation and evaporation effect becomes worse;

Step 6: Send the liquid low-boiling point refrigerant into the evaporator through the capillary tube; the low-boiling point refrigerant that has completed the evaporation process through the evaporator is mixed with the high-boiling point refrigerant that has passed through the condensing evaporator, and then enters the compressor for the next cycle process, ending step.

Further, in the step 1, the carbon nanotubes are 0.8-10 wt% of the refrigerant.

Further, the carbon nanotubes are surface-modified.

Further, the surface of the carbon nanotubes is grafted with functional groups having chemical properties similar to alkanes through covalent bonds.

Further, the functional groups with similar chemical properties to alkanes include C ₁₆ TMS , C ₈ TMS , and C ₃ TMS .

Further, the surface modification of the carbon nanotubes includes the following steps:

Step 11: Mix 10-30g of carbon nanotubes with 600ml of alcohol solution evenly, and ultrasonicate in a water bath for 60-80 minutes to form hydroxyl groups on the surface of the particles;

Step 12: adding 5-15 g of C ₁₆ TMS , C ₈ TMS or C ₃ TMS to the carbon nanotube/water suspension to form a covalent bond to complete the grafting of hydroxyl groups;

Step 13: Centrifuge the suspension, and wash the modified particles with alcohol for a set number of times;

Step 14: Dry the obtained particles in a vacuum oven to remove the organic solvent.

Further, the drying temperature of the vacuum oven in step 14 is 100°C-120°C.

The beneficial effects of the present invention are:

By setting and filling carbon nanotubes between the condenser and the gas-liquid separator, the porous structure and large specific surface area of carbon nanotubes are used to realize the low boiling point refrigeration of the gas phase in the gas-liquid separator in the self-cascading refrigeration system The mist-like lubricating oil droplets entrained by the refrigerant absorb, increase the density of the lubricating oil, promote the gravitational sedimentation of the lubricating oil in the gas-liquid separator and condensing evaporator, reduce the lubricating oil content in the low boiling point refrigerant, and prevent the lubricating oil from following the low The boiling point refrigerant enters the capillary and causes blockage;

By adding carbon nanotubes, and the carbon nanotubes follow the refrigerant to circulate in the refrigeration device. After the carbon nanotubes enter the compressor, they can lubricate the compressor, reduce the mechanical loss of the compressor, and reduce the The use of medium lubricating oil further promotes the reduction of oil foam in the gas phase low boiling point refrigerant;

Improve the heat transfer efficiency and cooling capacity of refrigeration devices by adding carbon nanotubes;

During the process of filling the carbon nanotubes in step 1, the compressor is stopped to facilitate the filling of the carbon nanotubes;

Through the surface modification of carbon nanotubes, the affinity between carbon nanotubes and lubricating oil composed of mineral oil can be improved, the purpose of absorbing lubricating oil can be better achieved, and the agglomeration of carbon nanotube particles in lubricating oil can be reduced at the same time. Reduce the sedimentation ratio of particles, so as to achieve the purpose of improving oil phase migration.

Description of drawings

FIG. 1 is a structural block diagram of Embodiment 1 of the present invention.

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.

It should be noted that the diagrams provided in the following embodiments are only schematically illustrating the basic ideas of the present invention, and only the components related to the present invention are shown in the diagrams rather than the number, shape and shape of the components in actual implementation. Dimensional drawing, the type, quantity and proportion of each component can be changed arbitrarily during actual implementation, and the component layout type may also be more complicated.

Embodiment one:

As shown in Figure 1, a low-temperature refrigeration device based on the gravity oil separation effect of carbon nanotubes, including a compressor, a condenser, a gas-liquid separator, a throttle valve, a capillary tube, a condensation evaporator, an evaporator and a filling port; The outlet of the compressor is connected to the inlet of the condenser, and the outlet of the condenser is connected to the inlet of the gas-liquid separator; the high-boiling point refrigerant channel of the gas-liquid separator is connected to the evaporation side channel of the condensing evaporator through a throttle valve; The low-boiling point refrigerant channel is connected to the condensing side channel of the condensing evaporator; the condensing side outlet of the condensing evaporator is connected to the inlet of the evaporator through a capillary tube; the evaporating side outlet of the condensing evaporator is connected to the outlet of the evaporator and connected to the compressor Inlet connection; a charging port is provided between the condenser and the gas-liquid separator, and the charging port is used for filling carbon nanotubes. It should be noted that in some other embodiments, the charging port can also be directly arranged on the condenser device or placed between other devices. The refrigerant in the refrigeration device is an existing self-cascading mixed refrigerant, and the self-cascading mixed refrigerant includes one or a combination of high-boiling point refrigerants and one or a combination of low-boiling point refrigerants, wherein High boiling point refrigerants include R134A, R600A, R1234YF, R1234ZE(Z), R1234ZE(E), R142B, R22, etc., and low boiling point refrigerants include R23, R14, R1150, R290, R170, R125, R32, etc. The self-cascading mixed refrigerant of the binary mixed refrigerant type includes a combination of R134A and R23 at a ratio of 60:40, a combination of R134A/R744 at a ratio of 65:35, and a combination of R600A/R744 at a ratio of 65:35 and the combination of R170/R600A at a ratio of 8:92; the ternary mixed working medium includes the combination of R290, R600A and R123 at a ratio of 50:10:40, and the ratio of R23, R143A and R134A at a ratio of 10:70:20 Combination of ratios; quaternary mixed working fluids include R23, R125, R134A and R32 in a ratio of 10:45:40:5. In this example, the refrigerant mixed with R744 and R134A is used, and the ratio is 35:65.

The filling port is used for filling carbon nanotubes, through which the mist-like oil droplets in the gas-phase low-boiling point refrigerant separated by the gas-liquid separator are absorbed. The carbon nanotubes follow the refrigerant as it circulates through the refrigeration unit.

In the process of implementation, by setting a filling port filled with carbon nanotubes between the condenser and the gas-liquid separator, the self-cascading refrigeration system is realized by utilizing the porous structure and large specific surface area of carbon nanotubes. The mist-like lubricating oil droplets entrained by the gas-phase low-boiling point refrigerant in the gas-liquid separator are adsorbed to increase the density of the lubricating oil, and promote the gravitational settlement of the lubricating oil in the gas-liquid separator and condensing evaporator, preventing the lubricating oil from following the low boiling point The refrigerant enters the capillary and causes blockage; by adding carbon nanotubes, and the carbon nanotubes follow the refrigerant to circulate in the refrigeration device, where the carbon nanotubes enter the compressor, lubricate the compressor, and reduce the compressor reduce the amount of lubricating oil used in the compressor, and further promote the reduction of oil foam in low-boiling refrigerants; increase the heat exchange efficiency and cooling capacity of the refrigeration device by adding carbon nanotubes.

A low-temperature refrigeration method based on the gravity oil separation effect of carbon nanotubes, comprising the steps of:

Step 1: The compressor stops working, and the set amount of carbon nanotubes is filled into the refrigeration device through the filling port;

Step 2: Start the compressor; carbon nanotubes and refrigerant are mixed into the condenser;

Step 3: Condensate through the condenser to obtain partially liquefied refrigerant; it should be noted that after the condensation effect of the condenser, the high-boiling point refrigerant releases heat to form a liquid state, and the low-boiling point refrigerant remains in a gaseous state;

Step 4: The partially liquefied refrigerant enters the gas-liquid separator for the separation process of gas-phase low-boiling point refrigerant and high-boiling point refrigerant; the separated high-boiling point refrigerant enters the evaporation side channel of the condensing evaporator through the throttle valve, and the low-temperature The refrigerant enters the condensing side channel of the condensing evaporator;

Step 5: In the condensing evaporator, the high-boiling point refrigerant containing lubricating oil and carbon nanotubes exchanges heat with the saturated gas-phase low-boiling point refrigerant, so that the high-boiling point refrigerant absorbs heat and evaporates to form steam, and the low-boiling point refrigerant releases heat condense into a liquid state;

Step 6: Send the liquid low-boiling point refrigerant into the evaporator through the capillary tube; the low-boiling point refrigerant that has completed the evaporation process through the evaporator is mixed with the high-boiling point refrigerant that has passed through the condensing evaporator, and then enters the compressor for the next cycle process, ending Step; wherein the high boiling point refrigerant contains lubricating oil and carbon nanotubes.

The set amount of carbon nanotubes in the step 1 is 0.8-10 wt% of the refrigerant. In this example, the carbon nanotubes are surface-modified; on the surface of the carbon nanotubes, functional groups with similar chemical properties to alkanes are grafted on the surface of the carbon nanotubes, including C ₁₆ TMS, C ₈ TMS, and C ₃ TMS. Modification of nanotubes. Through surface-modified carbon nanotubes, the affinity with lubricating oil composed of mineral oil can be improved, and the purpose of absorbing lubricating oil can be better achieved, while reducing the agglomeration of carbon nanotube particles in lubricating oil and reducing particle deposition Ratio, so as to achieve the purpose of improving oil phase migration. The surface modification of carbon nanotubes is obtained through the following steps, taking C ₁₆ TMS as an example:

Step 11: Mix 20g of carbon nanotubes with 600ml of alcohol solution evenly, and ultrasonicate in a water bath for 60-80 minutes to form hydroxyl groups on the surface of the particles;

Step 12: adding 10 g of C ₁₆ TMS to the carbon nanotube/water suspension to form a covalent bond to complete the grafting of hydroxyl groups;

Step 13: Centrifuge the suspension and wash the modified particles several times with alcohol;

Step 14: The obtained particles were dried in a vacuum oven for 3 hours to remove the organic solvent.

The drying temperature of the vacuum oven in step 14 is 100°C-120°C, preferably 110°C.

In the step 3, due to the high viscosity of the lubricating oil, carbon nanotubes have a phase migration mechanism, so carbon nanotubes are easier to combine with the lubricating oil than refrigerants. After the lubricating oil is absorbed, due to the increase in weight, the Deposition, so carbon nanotubes and lubricating oil are more present in liquid high-boiling point refrigerants;

In the step 5, the high-boiling point refrigerant containing carbon nanotubes produces a large number of bubbles due to the heat transfer effect of boiling, and the carbon nanotubes are resuspended in the refrigerant under the action of the bubbles generated during the boiling process, so that the carbon nanotubes are dispersed and the circulation is avoided. During the process, due to the deposition and agglomeration of carbon nanotubes, the effect of condensation and evaporation is deteriorated, which helps the device to run efficiently for a long time.

During the implementation process, during the process of filling carbon nanotubes in step 1, the compressor is stopped to facilitate the filling of carbon nanotubes; by surface modification of carbon nanotubes, the composition of carbon nanotubes and mineral oil is improved. Improve the affinity of lubricating oil, better achieve the purpose of absorbing lubricating oil, reduce the agglomeration of carbon nanotube particles in lubricating oil, reduce the sedimentation ratio of particles, so as to achieve the purpose of improving oil phase migration.

Embodiment two:

This embodiment is obtained based on the improvement of Embodiment 1, wherein the modification process of carbon nanotubes includes the following steps:

Step 21: Add methyl methacrylate into a three-necked bottle filled with methanol and carbon nanotubes; wherein the mass ratio of methyl methacrylate to carbon nanotubes is 20:1, and the ratio of methyl methacrylate to methanol 1g/20ml～1g/40ml;

Step 22: ultrasonically treat the three-neck bottle for 10-30 minutes;

Step 23: Continuously inject nitrogen into the three-neck bottle for 25-35 minutes

Step 24: Add 1g of free radical initiator to the three-necked bottle, and react for 6-10 hours at 55°C to 70°C; in this example, azobisisobutyronitrile is used as the free radical initiator, which can Promote the formation of covalent bonds between carbon nanotubes and methyl methacrylate, and ensure a more thorough reaction;

Step 25: Obtain the reacted product by filtration, and ultrasonically wash with ethyl acetate for 3 to 5 times;

Step 26: Put the washed particles into a vacuum oven, set the temperature at 40°C-50°C, dry for 16-20 hours, and remove the organic solvent.

The above description is only a specific example of the present invention, and does not constitute any limitation to the present invention. Obviously, for those skilled in the art, after understanding the content and principle of the present invention, it is possible to make various modifications and changes in form and details without departing from the principle and structure of the present invention, but these are based on the present invention. The modification and change of the inventive concept are still within the protection scope of the claims of the present invention.

Claims (5)

1. A low-temperature refrigeration device based on the gravity oil separation effect of carbon nanotubes, characterized in that it comprises a compressor, a condenser, a gas-liquid separator, a throttle valve, a capillary tube, a condensation evaporator, an evaporator and a filling port; The outlet of the compressor is connected to the inlet of the condenser, and the outlet of the condenser is connected to the inlet of the gas-liquid separator; The high-boiling point refrigerant channel of the gas-liquid separator is connected to the evaporating side channel of the condensing evaporator through a throttle valve; the low-boiling point refrigerant channel of the gas-liquid separator is connected to the condensing side channel of the condensing evaporator; the condensing side of the condensing evaporator The outlet is connected to the inlet of the evaporator through a capillary tube; the outlet of the evaporation side of the condensing evaporator is connected to the outlet of the evaporator and connected to the inlet of the compressor; a charging port is provided between the condenser and the gas-liquid separator, and the charging port It is used to fill carbon nanotubes; the lubricating oil is adsorbed by carbon nanotubes to make the lubricating oil settle by gravity. The self-cascade mixed refrigerant includes one or a combination of high-boiling refrigerants, and one or a combination of low-boiling refrigerants; wherein the high-boiling refrigerants include R134A, R600A, R1234YF, R1234ZE(Z), R1234ZE (E), R142B and R22, low-boiling point refrigerants include R23, R14, R1150, R290, R170, R125 and R32, the carbon nanotubes are surface-modified, and the surface of the carbon nanotubes is covalently bonded Grafting functional groups with similar chemical properties to alkanes, including C ₁₆ TMS , C ₈ TMS , and C ₃ TMS . 2. a low-temperature refrigeration method based on carbon nanotube gravity oil separation effect, it is characterized in that, described refrigeration method is based on the refrigeration unit described in claim 1, and refrigeration method comprises the steps: Step 1: The compressor stops working, and the set amount of carbon nanotubes is filled into the refrigeration device through the filling port; Step 2: Start the compressor; carbon nanotubes and refrigerant are mixed into the condenser; Step 3: After condensing in the condenser, a partially liquefied refrigerant is obtained; the high-boiling point refrigerant is condensed to form a liquid state after exothermic condensation, and the low-boiling point refrigerant remains in a gaseous state; due to the high viscosity of the lubricating oil, the carbon nanotubes have a migration mechanism , so carbon nanotubes absorb lubricating oil and deposit, and mix with liquid high-boiling point refrigerant; Step 4: The partially liquefied refrigerant enters the gas-liquid separator for the separation process of gas-phase low-boiling point refrigerant and high-boiling point refrigerant; the separated high-boiling point refrigerant enters the evaporation side channel of the condensing evaporator through the throttle valve, and the low-temperature The refrigerant enters the condensing side channel of the condensing evaporator; Step 5: In the condensing evaporator, the high-boiling point refrigerant containing lubricating oil and carbon nanotubes exchanges heat with the saturated gas-phase low-boiling point refrigerant, so that the high-boiling point refrigerant absorbs heat and evaporates to form steam, and the low-boiling point refrigerant releases heat Condensation becomes liquid; the high-boiling point refrigerant containing carbon nanotubes produces a large number of bubbles due to the heat transfer effect of boiling, and the carbon nanotubes are resuspended in the refrigerant under the action of bubbles generated during the boiling process, so that the carbon nanotubes are dispersed and the cycle process is avoided. Due to the deposition and agglomeration of carbon nanotubes, the condensation and evaporation effect becomes worse; Step 6: Send the liquid low-boiling point refrigerant into the evaporator through the capillary tube; the low-boiling point refrigerant that has completed the evaporation process through the evaporator is mixed with the high-boiling point refrigerant that has passed through the condensing evaporator, and then enters the compressor for the next cycle process, ending step. 3. A low-temperature refrigeration method based on the gravity oil separation effect of carbon nanotubes according to claim 2, characterized in that, in the step 1, the carbon nanotubes are 0.8-10 wt% of the refrigerant. 4. a kind of cryogenic refrigeration method based on carbon nanotube gravity oil separation effect according to claim 2, is characterized in that, the surface modification of described carbon nanotube comprises the steps: Step 11: Select 10-30g of carbon nanotubes and mix them evenly with 600ml of alcohol solution, and ultrasonicate in a water bath for 60-80 minutes to form hydroxyl groups on the surface of the particles; Step 12: adding 5-15 g of C ₁₆ TMS , C ₈ TMS or C ₃ TMS to the carbon nanotube/water suspension to form a covalent bond to complete the grafting of hydroxyl groups; Step 13: Centrifuge the suspension, and wash the modified particles with alcohol for a set number of times; Step 14: Dry the obtained particles in a vacuum oven to remove the organic solvent. 5 . The low-temperature refrigeration method based on the gravity oil separation effect of carbon nanotubes according to claim 4 , wherein the drying temperature of the vacuum oven in the step 14 is 100° C. to 120° C. 5 .

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