ES2952980T3 - Falling film evaporator and cooling system - Google Patents

Abstract

A cooling system and a falling film evaporator. The refrigeration system includes: a refrigeration circuit having an air outlet of a compressor, a condenser, a regulating element, a falling film evaporator and an air inlet of the compressor that are connected in sequence by pipes, where the falling film evaporator comprises a housing, a distributor located at a top within the housing and a heat exchange pipe located below the distributor; an oil return branch having an oil inlet point connected to a lower portion of the falling film evaporator and an oil return point connected to the air inlet of the compressor; and a bypass branch having a bypass inlet connected downstream of the throttling element and a bypass outlet connected to the bottom of the falling film evaporator and used to introduce part of two-phase gas-liquid refrigerant into the falling film evaporator . (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Falling film evaporator and cooling system

Technical field

The present invention relates to the field of refrigeration and, in particular, to a refrigeration system having a falling film evaporator.

Background in the art

Currently, for a refrigeration system using a falling film evaporator, the oil-rich region in the system generally exists at the bottom inside the falling film evaporator casing. Therefore, an oil intake point corresponding to an oil return branch is usually also arranged at the bottom inside the falling film evaporator casing, to suck refrigerant in which the lubricating oil is dissolved into the compressor. for lubrication. In this case, if only a small amount of liquid phase refrigerant accumulates in the falling film evaporator in the working mode, it causes an unduly high oil concentration in the refrigerant liquid, which increases the flow resistance and affects the oil return. As the amount of lubricating oil accumulated in the evaporator increases, the heat transfer effect deteriorates. Consequently, the amount of lubricating oil entering the compressor will decrease, which will affect the lubrication performance of the compressor, increase wear and affect reliability. If the refrigerant charge amount in the entire refrigeration system is increased enough and the throttle valve is opened widely to preferably ensure a sufficiently high liquid level in the evaporator instead of ensuring throttle performance, the problem is That the lubricating oil cannot be completely dissolved in the liquid phase refrigerant can be solved by increasing the amount of liquid phase refrigerant accumulated in the falling film evaporator to a sufficiently large value. However, this limits the thermodynamic property of the system and increases costs. Therefore, how to balance the costs and recovery effect of lubricating oil has become a technical problem to be solved in the art.

US 5561987 A discloses a compression refrigeration apparatus that uses a falling film evaporator and utilizes a vapor-liquid separator where the refrigerant vapor is transported by a bypass line to the inlet of the evaporator located on the bottom surface of heat exchange below the nominal pool level so that the steam agitates the coolant and lubricating oil mixture in the pool.

Compendium of invention

An objective of the present invention is to provide a refrigeration system and a falling film evaporator, to balance the thermodynamic property and lubricating oil recovery effect of the refrigeration system that the falling film evaporator has.

The present invention provides a refrigeration system as defined in claim 1. It comprises: a refrigeration circuit having an air outlet from a compressor, a condenser, a throttle element, a falling film evaporator and an air inlet from the compressor that are connected in sequence by pipes, wherein the falling film evaporator comprises a casing, a distributor located in an upper part within the casing and a heat exchange pipe located below the distributor; an oil return branch having an oil intake point connected to a lower portion of the falling film evaporator and an oil return point connected to the air inlet of the compressor; and characterized by a bypass branch having a bypass inlet disposed in the distributor and connected downstream of the throttling element, and a bypass outlet connected to the bottom of the falling film evaporator and used to introduce part of the two-phase refrigerant gas -liquid in the falling film evaporator.

Brief description of the drawings

Fig. 1 is a schematic diagram of a falling film evaporator and oil return loop according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of the cooling system according to an embodiment of the present invention.

Detailed description

As shown in Fig. 1 and Fig. 2, an embodiment of a cooling system. The system of Refrigeration comprises: a refrigeration circuit 100 to perform a main refrigeration function, an oil return branch 200 to provide a return of lubricating oil to the compressor and a bypass branch 300.

The refrigeration circuit 100 has an air outlet 110b of a compressor 110, an oil separator 150, a condenser 120, a throttling element 130, a falling film evaporator 140 and an air inlet 110a of the compressor 110 that are connected in sequence by pipes. Specifically, the falling film evaporator 140 comprises a housing 141, a distributor 142 located at a top within the housing 141, and a heat exchange pipe 143 located below the distributor 142. In a normal operating mode, the refrigerant, After being compressed by the compressor 110, it flows from the air outlet 110b to the condenser 120 for condensation and is then throttled by the throttle element 130. The throttled two-phase refrigerant enters the falling film evaporator 140. The phase refrigerant gaseous will be sucked directly to the compressor 110. The liquid phase refrigerant is distributed by the distributor 142, forms a refrigerant liquid film to flow through the heat exchange pipe 143 into the falling film evaporator 140 and exchanges heat with a medium to cool in it. After the heat exchange, the gas phase refrigerant obtained by evaporation is sucked into the compressor 110, to participate in a new work cycle.

Additionally, the oil return branch 200 has an oil intake point 210 connected to a lower portion of the falling film evaporator 140 and an oil return point 220 connected to the air inlet 110a of the compressor 110. In the mode In normal work, some of the lubricating oil that provides lubrication to the compressor 110 will enter the refrigeration cycle along with the refrigerant flow. In this case, this part of the lubricating oil entering the refrigeration cycle can be sucked from the bottom of the falling film evaporator 140 towards the compressor 110. Therefore, the impact on both the heat exchange effect and the compressor 110 can be avoided. of the refrigerant as well as the lubrication effect of the compressor.

Furthermore, the bypass branch 300 has a bypass inlet 320 connected downstream of the throttling element 130 and a bypass outlet 310 connected to the bottom of the falling film evaporator 140. According to the invention, the bypass inlet 320 is arranged in the distributor 142 and is used to introduce part of the two-phase gas-liquid refrigerant into the falling film evaporator 140. In this case, under a pressure difference, part of the two-phase gas-liquid refrigerant downstream of the throttling element 130 will flow to the bottom of the falling film evaporator 140 through the bypass branch 300, so that the refrigerant at the bottom inside the casing 141 of the falling film evaporator reaches a predetermined liquid level. The preset liquid level allows the liquid phase refrigerant to form a sufficiently large liquid level at the bottom inside the falling film evaporator housing 141, so that lubricating oil droplets from above the falling film evaporator can come into substantial contact with the liquid level and dissolve in the refrigerant. This configuration makes it easier to suck most of the lubricating oil back to the compressor through the oil return branch, achieving efficient oil return function. The preset liquid level specific height value or liquid level area specific value depends on various parameters such as the evaporator shell profile and the required oil return ratio. According to the teachings of the above embodiment, a person skilled in the art can integrate the related parameters and set the liquid level in a real application environment without creative efforts.

In order that the lubricating oil can be completely dissolved in the liquid phase refrigerant at the bottom of the falling film evaporator, the bypass branch is improved in multiple aspects, which will be described one by one.

For example, the bypass input 320 is higher than the bypass output 310 in a vertical direction. For such a configuration, in addition to the pressure difference between the refrigerant on the bypass inlet side and the refrigerant on the bypass outlet side, the gravity of the refrigerant caused by the height difference between the two can also be used as a source. of power to drive the bypass refrigerant to flow. Furthermore, in some cases, an auxiliary drive apparatus may be additionally provided in the bypass branch 300, to provide more power to suck the two-phase refrigerant from the bypass inlet 320 to the bypass outlet 310.

For another example, the bypass branch 300 has a plurality of bypass inputs 320 and/or a plurality of bypass outputs 310. The bypass inputs 320 and the bypass outputs 310 may belong to the same bypass branch, i.e. , similar to the configuration of a liquid collector or liquid separator; or they may belong to different branch lines. In this case, the falling film evaporator comprises a plurality of bypass branches 300, and each of the bypass branches may comprise at least one bypass inlet and/or a bypass outlet. Such a configuration can effectively and uniformly increase the bypass flow. Optionally, the plurality of bypass outlets 310 may also be arranged evenly spaced on the bottom of falling film evaporator housing 141. That way, the bypass refrigerant can be fed to the evaporator more evenly, thus avoiding undue impact.

Optionally, as a specific position for arrangement, the bypass outlet 310 may be arranged at the bottom of the falling film evaporator housing 141. Therefore, the refrigerant entering the evaporator through the bypass outlet 310 basically does not unduly affect the original refrigerant liquid level in the evaporator, making the entire bypass process more stable.

Optionally, a smaller flow cross-sectional area of a branch pipe 300 is 0.5-20% of the flow cross-sectional area of a refrigeration circuit pipe 100 downstream of the throttling element 130. In In this case, it is ensured that the amount of bypass refrigerant can meet the requirement of increasing the liquid level and will not cause great impact on the normal cycle. In general, an unduly large amount of refrigerant accumulated in the casing of the falling film evaporator is not desirable in the present invention, because this has only a limited effect on improving the heat exchange efficiency and greatly increases the amount refrigerant charging, as well as material costs. Therefore, the above problem can be well solved by limiting the flow area of the bypass branch to control the bypass flow, and a balance between efficiency and cost can be achieved.

Optionally, a branch pipe 300 has a circular and/or rectangular and/or channel cross section, to adapt to different application scenarios and flow conditions.

Furthermore, as another embodiment, the bypass input of the bypass branch may be further connected to the distributor, although it is not shown in the figure. In this case, the bypass branch can be considered part of the falling film evaporator.

In particular, the falling film evaporator according to an example, which does not form part of the present invention, comprises: a casing; a distributor arranged in an upper part within the housing; a heat exchange pipe arranged inside the casing and below the distributor; an oil intake point disposed in a lower portion of the falling film evaporator; and a bypass branch having a bypass inlet connected to the distributor and a bypass outlet connected to the bottom of the falling film evaporator and which is used to introduce part of the gas-liquid two-phase refrigerant into the bottom of the falling film evaporator, so the refrigerant at the bottom inside the falling film evaporator casing reaches a preset liquid level. The preset liquid level allows the liquid phase refrigerant to form a sufficiently large liquid level at the bottom inside the falling film evaporator casing, so that lubricating oil droplets from above the falling film evaporator can enter. substantially in contact with the liquid level and dissolve in the coolant, thereby achieving an efficient oil return function.

Similarly, in order that the lubricating oil can be completely dissolved in the liquid phase refrigerant at the bottom of the falling film evaporator, the bypass branch is improved in multiple aspects, which will also be described one by one.

According to the configuration of the above example, the bypass input is generally higher than the bypass output in a vertical direction. In this case, in addition to the pressure difference between the refrigerant on the bypass inlet side and the refrigerant on the bypass outlet side, the gravity of the refrigerant caused by the height difference between the two can also be used as a source. of power to drive the bypass refrigerant to flow. Furthermore, in some cases, an auxiliary drive apparatus may be additionally provided in the bypass branch, to provide more power to suck the two-phase refrigerant from the bypass inlet to the bypass outlet.

For another example, the bypass branch has a plurality of bypass inputs and/or a plurality of bypass outputs. The bypass inlets and the bypass outlets can belong to the same bypass branch, that is, similar to the configuration of a liquid collector or liquid separator; or they may belong to different branch lines. In this case, the falling film evaporator comprises a plurality of bypass branches, and each of the bypass branches may comprise at least one bypass inlet and/or a bypass outlet. Such a configuration can effectively and uniformly increase the bypass flow. Optionally, the plurality of bypass outlets may also be arranged evenly spaced at the bottom of the falling film evaporator housing. That way, the bypass refrigerant can be fed to the evaporator more evenly, thus avoiding undue impact.

Optionally, as a specific position for arrangement, the bypass outlet can be arranged at the bottom of the falling film evaporator casing. Therefore, the refrigerant entering the evaporator through the bypass outlet basically does not unduly affect the liquid level. original refrigerant into the evaporator, making the whole bypass process more stable.

Optionally, a branch pipe has a circular and/or rectangular and/or channel cross section, to adapt to different application scenarios and flow conditions.

Further improvements in terms of the oil return branch in the cooling system according to the above embodiments will be described with reference to Fig. 1 and Fig. 2 again.

The oil return branch 200 has a plurality of oil intake points 210. The oil intake points 210 may belong to the same oil return branch, that is, similar to the configuration of a liquid collector or separator. of liquid; or they may belong to different oil return branches. In this case, the cooling system comprises a plurality of oil return branches 200, and each of the oil return branches may comprise at least one oil intake point and/or an oil return point. Such configuration can effectively and uniformly increase the amount of oil return. Optionally, a plurality of oil intake points 210 may also be arranged evenly spaced at the bottom of the falling film evaporator housing 141. Thus, the recovered lubricating oil can be sucked from the evaporator more evenly, thus avoiding undue impact.

Optionally, as a specific position for the arrangement, the oil intake point 210 may be arranged at the bottom of the falling film evaporator housing 141. Therefore, the lubricating oil in the evaporator can basically be recovered through the oil intake point 210, and the amount of lubricating oil accumulated in the evaporator will not be unduly large to affect the heat exchange performance of the evaporator and the compressor lubrication performance.

Optionally, an ejector 230 may also be provided in the oil return branch 200. The ejector 230 has a first ejector inlet connected to the oil intake point 210, a second ejector inlet connected to an inlet side of the condenser 120 and an ejection outlet connected to the air inlet 110a of the compressor 110, to provide energy for oil return. Definitely, other oil return methods well known in the art can also be adopted according to different application scenarios.

The examples and implementations provided herein should be interpreted as exemplary rather than limiting. The present invention may encompass various modifications and substitutions made without departing from the scope of the present invention as defined in the appended claims.

Claims (14)

1. A refrigeration system comprising: a refrigeration circuit (100) having an air outlet (110b) from a compressor (110), a condenser (120), a throttling element (130), a falling film evaporator (140) and an air inlet (110a) of the compressor that are connected in sequence by pipes, where the falling film evaporator comprises a casing (141), a distributor (142) located in an upper part within the casing and a heat exchange pipe (143 ) located under the distributor; an oil return branch (200) having an oil intake point (210) connected to a lower part of the falling film evaporator (140) and an oil return point (220) connected to the air inlet ( 110a) of the compressor (110); and characterized by a bypass branch (300) having a bypass inlet (320) disposed in the distributor (142) and connected downstream of the throttling element (130), and a bypass outlet (310) connected to the bottom of the evaporator falling film and used to introduce part of the gas-liquid two-phase refrigerant into the falling film evaporator (140). 2. The cooling system according to claim 1, wherein the bypass inlet (320) is higher than the bypass outlet (310) in the vertical direction. 3. The refrigeration system according to claim 1 or 2, wherein the bypass branch (300) has a plurality of bypass inlets (320) and/or a plurality of bypass outlets (310). 4. The refrigeration system according to claim 3, wherein the plurality of bypass outlets (310) are arranged evenly spaced in a lower portion of the housing (141) of the falling film evaporator (140). 5. The refrigeration system according to claim 1 or 2, wherein the bypass outlet (310) is provided at the bottom of the housing (141) of the falling film evaporator (140). 6. The cooling system according to claim 1 or 2, comprising a plurality of branch branches (300). 7. The refrigeration system according to claim 1 or 2, wherein the smallest flow cross-sectional area of a branch pipe (300) is 0.5% to 20% of the flow cross-sectional area of a cooling circuit pipe (100) downstream of the throttling element (130). 8. The cooling system according to claim 1 or 2, wherein a branch pipe (300) has a circular and/or rectangular and/or channel cross section. 9. The cooling system according to any of claims 1 to 7, wherein the oil return branch (200) has a plurality of oil intake points (210). 10. The refrigeration system according to claim 8, wherein the plurality of oil intake points (210) are arranged evenly spaced in a lower portion of the housing (141) of the falling film evaporator (140). 11. The refrigeration system according to any of claims 1 to 9, wherein the oil intake point (210) is provided at the bottom of the housing (141) of the falling film evaporator (140). 12. The cooling system according to any of claims 1 to 7, wherein an ejector (230) is arranged in the oil return branch (200), the ejector has a first ejection inlet connected to the oil intake point. (210), a second ejection inlet connected to an inlet side of the condenser (120), and an ejection outlet connected to the air inlet (110a) of the compressor (110). 13. The cooling system according to any of claims 1 to 7, comprising a plurality of oil return branches (200). 14. The refrigeration system according to any of claims 1 to 7, wherein an auxiliary drive apparatus for sucking the two-phase refrigerant from the bypass inlet (320) to the bypass outlet (310) is arranged in the bypass branch (300).