A two-phase vertical falling film condenser and refrigeration system

Abstract

This invention relates to a two-phase vertical falling film condenser and a refrigeration system, comprising: a horizontal gas pipe, which is horizontally arranged and connected to a corresponding compressor to receive gaseous refrigerant output from the compressor; a horizontal liquid pipe, which is horizontally arranged and connected to a corresponding expansion valve to output liquid refrigerant to the expansion valve; and several vertical heat exchange tubes, which are spaced apart and vertically connected between the horizontal gas pipe and the horizontal liquid pipe, thereby connecting the horizontal gas pipe and the horizontal liquid pipe. A portion of the gaseous refrigerant condenses into liquid, which flows downwards under gravity within the vertical heat exchange tubes, while another portion of the gaseous refrigerant flows through the vertical heat exchange tubes in gaseous form under the drive of the compressor, forming a refrigerant circuit from the compressor to the expansion valve.

Description

Technical Field

[0001] This invention relates to the field of refrigeration, specifically to a two-phase vertical falling film condenser and a refrigeration system. Background Technology

[0002] The current structural diagram of the outdoor unit of a typical household split air conditioner is as follows: Figure 1-2 As shown. The heat exchange tubes of the outdoor unit of the air conditioner are all horizontally arranged finned tubes, connected in a serpentine configuration. This is a horizontally coiled structure, where air is cooled and cooled by forced convection outside the tubes thanks to a fan. The refrigerant side of this structure (corresponding to...) Figure 2 (From the compressor end): The refrigerant is compressed into a high-temperature, high-pressure gas by the compressor and enters the condenser to exchange heat with the air. Inside the pipes, the refrigerant undergoes heat exchange from superheated vapor and gas-liquid two-phase condensation to subcooled liquid. As the condensation process proceeds, such as... Figure 3 As shown, condensate forms on the wall surface after refrigerant dissipates heat, hindering heat exchange between the vapor and the wall, constituting the main thermal resistance and reducing the heat transfer coefficient. With the increasing amount of condensate, the liquid film thickness on the wall increases, and coupled with the reduced refrigerant flow rate due to decreased vapor volume, the condensation effect deteriorates sharply in the latter part of the heat exchange tube. (Air side - corresponding to...) Figure 2 (To the expansion valve end): Due to the thermal resistance of the condensate inside the tube, the temperature of the outer wall of the heat exchange tube decreases, reducing the driving force for heat exchange and thus reducing the amount of heat exchanged by forced air convection. To achieve sufficient heat exchange, the heat exchange area needs to be increased to meet the heat exchange requirements. Using fins to increase the outer area of ​​the tube increases investment costs and also results in a larger volume. Increasing the length of the heat exchange tube further increases the amount of liquid phase accumulated, leading to a greater charge volume for the air conditioning unit.

[0003] The purpose of this invention is to design a two-phase vertical falling film condenser and refrigeration system to address the problems existing in the prior art. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a two-phase vertical falling film condenser and a refrigeration system, which can effectively solve at least one of the problems existing in the prior art.

[0005] The technical solution of this invention is:

[0006] A two-phase vertical falling film condenser, comprising:

[0007] A horizontal gas pipe, which is set horizontally and is connected to a corresponding compressor to receive gaseous refrigerant output from the compressor;

[0008] A horizontal liquid pipe, which is horizontally positioned, is connected to a corresponding expansion valve to output liquid refrigerant to the expansion valve;

[0009] A number of vertical heat exchange tubes are provided, spaced apart and vertically connected between the horizontal gas tube and the horizontal liquid tube, thereby connecting the horizontal gas tube and the horizontal liquid tube. This allows a portion of the gaseous refrigerant to condense into liquid and flow down the vertical heat exchange tube under gravity, while another portion of the gaseous refrigerant flows through the vertical heat exchange tube in gaseous form under the drive of the compressor, forming a refrigerant circuit from the compressor to the expansion valve.

[0010] Furthermore, after the horizontal air pipe is coiled into several sections in a serpentine pattern, it begins to connect to the vertical heat exchange pipe.

[0011] Furthermore, after the horizontal air tube is coiled in a serpentine pattern for 2-3 sections, it begins to connect to the vertical heat exchange tube.

[0012] Furthermore, after the horizontal liquid pipe is coiled into several sections in a serpentine pattern, it begins to connect to the vertical heat exchange pipe.

[0013] Furthermore, after the horizontal liquid pipe is coiled in a serpentine pattern for 3-4 segments, it begins to connect to the vertical heat exchange pipe.

[0014] Furthermore, it includes several relay pipes, which are horizontally arranged and vertically divide the vertical heat exchange pipe into several equal parts. The relay pipes are connected to the vertical heat exchange pipes, and the end of the relay pipes is connected to the end of the horizontal liquid pipe. This allows the refrigerant to collect from the upper section of the vertical heat exchange pipe into the relay pipe. Then, the gaseous refrigerant in the relay pipe is diverted to the lower section of the vertical heat exchange pipe, and the liquid refrigerant in the relay pipe is diverted to the horizontal liquid pipe.

[0015] Furthermore, the diameter of the vertical heat exchange tube is 9.5mm~10mm.

[0016] Furthermore, the length of the vertical heat exchange tube is 0.38m to 0.47m.

[0017] Furthermore, the horizontal air tube is positioned higher than the horizontal liquid tube.

[0018] A refrigeration system is further provided, the refrigeration system including any one of the two-phase vertical falling film condensers described in any one of the above.

[0019] Therefore, the present invention provides the following effects and / or advantages:

[0020] This application utilizes the condensation of a portion of the gaseous refrigerant to form a liquid on the inner wall of a vertical heat exchange tube. In the vertical direction, the liquid flows in the same direction as gravity, allowing gravity to propel the liquid downwards and thin the liquid film on the inner wall of the tube. Compared to horizontal coiled tubes, the thinner vertical liquid film reduces thermal resistance, increases the heat transfer coefficient, and improves the amount of heat exchanged. The remaining portion of the gaseous refrigerant remains in a gaseous state and passes directly through the vertical heat exchange tube under the drive of the compressor. With a thinner liquid film, the gaseous refrigerant can achieve better heat exchange through the vertical heat exchange tube.

[0021] This application can effectively reduce the thickness of the liquid film formed by the liquid refrigerant inside the vertical heat exchange tube, thereby improving the heat exchange efficiency.

[0022] The present application's structural design, which involves the horizontal gas pipe serpentinely looping through several segments before connecting to the vertical heat exchange pipe, and the horizontal liquid pipe serpentinely looping through several segments before connecting to the vertical heat exchange pipe, provides the refrigerant with sufficient path and time to reach a critical state of gas-liquid two-phase at the inlet of the vertical heat exchange pipe, and further cools it at the outlet of the horizontal liquid pipe.

[0023] This application, through practical simulation, derives the most suitable diameter of the vertical heat exchanger tubes and the optimal spacing between them based on the relationship between the flow rate of the coolant (V), the diameter of the vertical heat exchanger tubes (D), and the spacing between the vertical heat exchanger tubes (d), which can further improve the heat exchange efficiency.

[0024] It should be understood that the above summary and the following detailed description of the invention are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed. Attached Figure Description

[0025] Figure 1-2 This is a schematic diagram of the heat exchange tube structure of an existing air conditioner condenser.

[0026] Figure 3 This is a schematic diagram showing the formation of condensate on the wall surface inside the heat exchange tubes of an existing air conditioner condenser.

[0027] Figure 4 This is a schematic diagram of the structure of one embodiment of the present invention;

[0028] Figure 5 For the present invention Figure 4 The diagram shows the refrigerant flow direction of the embodiment shown.

[0029] Figure 6 This is a schematic diagram of the gas-liquid two-phase state inside a vertical heat exchange tube according to one embodiment of the present invention;

[0030] Figure 7 This is a schematic diagram of another embodiment of the present invention;

[0031] Figure 8 This is a coupled surface diagram of the heat transfer coefficient of the vertical heat exchange tube in this invention with the length and diameter of the heat exchange tube. Detailed Implementation

[0032] To facilitate understanding by those skilled in the art, the structure of the present invention will now be described in further detail with reference to the accompanying drawings:

[0033] refer to Figure 4 A two-phase vertical falling film condenser, comprising:

[0034] A horizontal gas pipe 1 is provided, which is set horizontally and is connected to a corresponding compressor to receive gaseous refrigerant output from the compressor.

[0035] In this embodiment, the gaseous refrigerant output from the compressor first exchanges heat in the horizontal gas pipe, a process similar to that of a conventional coiled refrigerant. After flowing through the horizontal gas pipe, the refrigerant gradually approaches its gaseous saturation point and is about to begin precipitating as a liquid. At this point, the refrigerant enters the vertical two-phase pipe section.

[0036] During this stage, the gaseous refrigerant flows within horizontal gas pipe 1 driven by the compressor. Throughout this process, the refrigerant remains in a gaseous state. As the compressor compresses the refrigerant, its state gradually approaches the gas saturation point, releasing heat. Because the refrigerant within the horizontal gas pipe remains gaseous, the released heat can fully contact the horizontal gas pipe and exchange heat effectively with the outside environment. The fan outside the condenser blows this heat away. This process and... Figure 1-2 The working principle of the front part of the horizontal serpentine tube is roughly the same as that of the other two. The difference is that the horizontal loop section of the horizontal gas tube 1 in this embodiment is less, so that the refrigerant remains in a gaseous state and does not form a liquid state to cover the inner wall of the horizontal gas tube 1, thus preventing the refrigerant from fully exchanging heat with the outside through the horizontal gas tube.

[0037] Next, the gaseous refrigerant enters the vertical heat exchange tube 2.

[0038] A number of vertical heat exchange tubes 2 are distributed at intervals and vertically connected between the horizontal gas pipe 1 and the horizontal liquid pipe 3, thereby connecting the horizontal gas pipe 1 and the horizontal liquid pipe 3. A portion of the gaseous refrigerant condenses into liquid and flows down the vertical heat exchange tube 2 under the action of gravity, while another portion of the gaseous refrigerant flows through the vertical heat exchange tube 2 in gaseous form under the drive of the compressor, forming a refrigerant circuit from the compressor to the expansion valve.

[0039] In this embodiment, reference Figure 6A portion of the gaseous refrigerant condenses into a liquid on the inner wall of the vertical heat exchange tube 2. In the vertical direction, the liquid flows in the same direction as gravity, allowing gravity to propel the liquid downwards and thin the liquid film on the inner wall of the tube. Compared to horizontal coils, the thinner liquid film in the vertical tube reduces thermal resistance, increases the heat transfer coefficient, and improves the amount of heat exchanged. The remaining gaseous refrigerant remains in a gaseous state and passes directly through the vertical heat exchange tube 2 under the drive of the compressor. With a thinner liquid film, the gaseous refrigerant can achieve better heat exchange through the vertical heat exchange tube 2.

[0040] Meanwhile, inside the vertical heat exchange tube 2, the refrigerant exists in a two-phase state, namely gas and liquid. The process from a fully saturated gaseous state to a fully saturated liquid state is a state of coexistence of the two phases.

[0041] A horizontal liquid pipe 3 is arranged horizontally and is connected to a corresponding expansion valve to output liquid refrigerant to the expansion valve.

[0042] In this embodiment, the liquid refrigerant collects in the horizontal liquid pipe 3, undergoes heat exchange along the horizontal liquid pipe 3 to achieve subcooling, and finally flows to the expansion valve. This process is similar to... Figure 2 The latter half of the traditional serpentine tube shown is the same.

[0043] Furthermore, in this embodiment, each of the vertical heat exchange tubes 2 is connected to the horizontal gas tube 1 and the horizontal liquid tube 3 respectively, so that the gaseous refrigerant can reach the vertical heat exchange tubes 2 respectively, and the gas-liquid two-phase change is completed in each vertical heat exchange tube to complete the heat exchange process.

[0044] In this embodiment, an external fan simultaneously dissipates heat from the horizontal air pipe 1, the vertical heat exchange pipe 2, and the horizontal liquid pipe 3.

[0045] Furthermore, after the horizontal air pipe 1 is coiled in a serpentine pattern for several segments, it begins to connect to the vertical heat exchange pipe 2. Specifically, after the horizontal air pipe 1 is coiled in a serpentine pattern for 2-3 segments, it begins to connect to the vertical heat exchange pipe 2.

[0046] In this embodiment, the reason why the horizontal gas pipe 1 is arranged in a serpentine pattern around several segments before connecting to the vertical heat exchange pipe 2 is that the main function of the vertical heat exchange pipe 2 is to use gravity to thin out the precipitated liquid. However, the gaseous refrigerant from the compressor is a superheated gas (e.g., 70°C), and it needs to be cooled to 50°C before refrigerant begins to precipitate liquid. Therefore, it is necessary to cool it down in the horizontal gas pipe 1 until liquid begins to precipitate before it enters the vertical heat exchange pipe. By arranging the horizontal gas pipe 1 in a serpentine pattern around several segments before connecting to the vertical heat exchange pipe 2, sufficient path and time can be provided for the gaseous refrigerant to cool down to the saturated state of the gas-liquid two-phase system. Through multiple experiments by the applicant, under the current gaseous refrigerant flow rate of air conditioners, the horizontal gas pipe 1, arranged in a serpentine pattern around 2-3 segments, can achieve the optimal critical state of the gas-liquid two-phase system.

[0047] Furthermore, after the horizontal liquid pipe 3 is coiled in a serpentine pattern for several segments, it begins to connect to the vertical heat exchange pipe 2. After the horizontal liquid pipe 3 is coiled in a serpentine pattern for 3-4 segments, it begins to connect to the vertical heat exchange pipe 2.

[0048] In this embodiment, the horizontal liquid pipe 3 is used to subcool the liquid refrigerant. For example, the liquid in the vertical section is just saturated, say at 50°C. During the process of liquid precipitation in the vertical heat exchange pipe 2, the temperature remains unchanged. It needs to be further cooled in the lower serpentine pipe to 45°C before being output to the expansion valve.

[0049] The term "subcooling" mentioned in this embodiment refers to the process of recooling a saturated liquid after condensation through a device (such as a subcooler) and by using certain methods, so that its temperature is lower than the saturation temperature under the condensation pressure. Subcooling can increase the cooling capacity of an air conditioning system and is a prior art in the field of refrigeration.

[0050] Furthermore, the diameter of the vertical heat exchange tube is 9.5mm~10mm.

[0051] Due to dimensional constraints, the pipe diameter and the number of heat exchange tubes are inversely proportional; a larger pipe diameter results in fewer vertical heat exchange tubes. Theoretically, a larger pipe diameter allows for a thinner liquid film, which is beneficial for heat exchange. Simultaneously, theoretically, a higher number of heat exchange tubes means less refrigerant is distributed across each tube, further facilitating heat exchange. Therefore, there is a contradictory relationship between pipe diameter and the number of heat exchange tubes, and an optimal matching relationship exists. (Reference) Figure 8 , Figure 8 The two-dimensional diagram below is a projection diagram. The darkest part in the middle is the area with the highest heat transfer coefficient. The vertical section length corresponding to this area is about 0.38~0.47m, and the corresponding pipe diameter is 9.5~10mm.

[0052] Figure 8The darkest position in the middle represents the point with the best heat transfer coefficient. The applicant obtained the highest heat transfer coefficient through simulation data.

[0053] Furthermore, the length of the vertical heat exchange tube is 0.38~0.47m.

[0054] Theoretically, when the refrigerant is in a two-phase state, a longer vertical section results in a larger heat exchange area, which is more conducive to heat exchange. However, when the length increases to a certain value, the refrigerant has already completed condensation, becoming a completely saturated liquid. At this point, the refrigerant enters a pure liquid state, requiring the liquid to be collected into a pipe. A large flow rate can be used to increase the flow velocity and improve the heat transfer coefficient. If the vertical section is too long, meaning the lower half of the vertical section is a pure liquid and subcooled section, the flow rate is too small, which is detrimental to heat exchange. (Reference) Figure 8 , Figure 8 The darkest position in the middle represents the point with the best heat transfer coefficient. The applicant found through simulation data that the heat transfer coefficient is the highest when the length of the vertical heat exchange tube is about 0.41m.

[0055] Furthermore, the horizontal air tube 1 is positioned higher than the height of the horizontal liquid tube 3.

[0056] By positioning the horizontal air pipe 1 higher than the horizontal liquid pipe 3, the liquid inside the vertical heat exchange pipe 2 can flow naturally downwards under the influence of gravity.

[0057] Example 2

[0058] This embodiment is basically the same as embodiment one in terms of structure and working principle, except that:

[0059] refer to Figure 7 It includes several relay pipes 4, which are arranged horizontally. The relay pipes 4 vertically divide the vertical heat exchange pipe 2 into several equal parts. The relay pipes 4 are connected to the vertical heat exchange pipe 2. The end of the relay pipe 4 is connected to the end of the horizontal liquid pipe 3, so that the refrigerant from the upper section of the vertical heat exchange pipe 2 is collected in the relay pipe 4. Then, the gaseous refrigerant in the relay pipe 4 is diverted to the lower section of the vertical heat exchange pipe 2, and the liquid refrigerant in the relay pipe 4 is diverted to the horizontal liquid pipe 3.

[0060] In this embodiment, the relay pipe 4 collects the liquid refrigerant and then re-disperses the gaseous refrigerant into each of the vertical heat exchange pipes 2. The relay pipe 4 further reduces the formation of a liquid film on the inner wall of the vertical heat exchange pipes 2, thereby accelerating heat dissipation.

[0061] Although this embodiment uses a middle-section drainage method, the addition of the middle section makes it impossible to install heat dissipation fins (the vertical section requires fins to improve heat dissipation), thus weakening the heat exchange effect. Furthermore, it is more difficult to manufacture and thus harder to promote.

[0062] Compared to Example 1, Example 1 offers a larger area for installing heat dissipation fins, thus improving heat exchange efficiency. Furthermore, the numerous vertical sections are designed to distribute the liquid accumulation within individual tubes, reducing the amount of liquid in each tube and minimizing the impact of the liquid film on heat exchange. Because of the multiple vertical tubes, the adverse effects of liquid within a single heat exchange tube are significantly reduced, eliminating the need for a separate intermediate drainage section. Therefore, Example 1 is more effective than Example 2.

[0063] A refrigeration system comprising any one of the two-phase vertical falling film condensers described in any one of the above statements.

[0064] Comparative Example

[0065] Adopting such Figures 1-3 Compare with existing condensers shown.

[0066] Through computer simulation and actual measurement, the diameter of the entire heat exchange tube in the existing technology, which is set horizontally, is 9.8 mm. Its cross-section is completely covered with liquid. After the refrigerant precipitates out liquid, the liquid film formed in the horizontal coil tube is 9.8 mm thick, and the actual heat exchange efficiency is about 80%.

[0067] Using the condenser provided in Example 1, the thickness of the liquid film at its thickest point (vertical tube outlet) does not exceed 1 mm, which is much smaller than the liquid film thickness of the horizontal serpentine tube. The actual heat exchange efficiency is 95%, which is about 15% higher than the existing technology.

[0068] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0069] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0070] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A two-phase vertical falling film condenser, characterized in that: include: A horizontal gas pipe, which is set horizontally and is connected to a corresponding compressor to receive gaseous refrigerant output from the compressor; A horizontal liquid pipe, which is horizontally positioned, is connected to a corresponding expansion valve to output liquid refrigerant to the expansion valve; A number of vertical heat exchange tubes are arranged at intervals and vertically connected between the horizontal gas tube and the horizontal liquid tube, thereby connecting the horizontal gas tube and the horizontal liquid tube. This allows a portion of the gaseous refrigerant to condense into liquid and flow down the vertical heat exchange tube under the action of gravity, while another portion of the gaseous refrigerant flows through the vertical heat exchange tube in gaseous form under the drive of the compressor, forming a refrigerant circuit from the compressor to the expansion valve. It includes several relay pipes, which are arranged horizontally. The relay pipes vertically divide the vertical heat exchange pipe into several equal parts. The relay pipes are connected to the vertical heat exchange pipes, and the end of the relay pipes is connected to the end of the horizontal liquid pipe. This allows the refrigerant to collect from the upper section of the vertical heat exchange pipe into the relay pipe. Then, the gaseous refrigerant in the relay pipe is diverted to the lower section of the vertical heat exchange pipe, and the liquid refrigerant in the relay pipe is diverted to the horizontal liquid pipe.

2. A two-phase vertical falling film condenser according to claim 1, characterized in that: After the horizontal air pipe is coiled into several sections in a serpentine pattern, it begins to connect to the vertical heat exchange pipe.

3. A two-phase vertical falling film condenser according to claim 2, characterized in that: After the horizontal air tube is coiled in a serpentine pattern for 2-3 sections, it begins to connect to the vertical heat exchange tube.

4. A two-phase vertical falling film condenser according to claim 1, characterized in that: After the horizontal liquid pipe is coiled into several sections in a serpentine pattern, it begins to connect to the vertical heat exchange pipe.

5. A two-phase vertical falling film condenser according to claim 4, characterized in that: After the horizontal liquid pipe is coiled in a serpentine pattern for 3-4 sections, it begins to connect to the vertical heat exchange pipe.

6. A two-phase vertical falling film condenser according to claim 1, characterized in that: The diameter of the vertical heat exchange tube is 9.5mm~10mm.

7. A two-phase vertical falling film condenser according to claim 1, characterized in that: The length of the vertical heat exchange tube is 0.38m to 0.47m.

8. A two-phase vertical falling film condenser according to claim 1, characterized in that: The horizontal air tube is positioned higher than the horizontal liquid tube.

9. A refrigeration system, characterized in that: The refrigeration system includes a two-phase vertical falling film condenser as described in any one of claims 1-8.

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