All-natural working medium cascade heat exchange system

Abstract

The invention provides an all-natural working medium cascade heat exchange system, relates to the technical field of heat exchange equipment, and aims to optimize the internal structure of the heat exchange system, improve the heat exchange efficiency and reduce the heat loss to a certain extent. The invention provides an all-natural working medium cascade heat exchange system. The all-natural working medium cascade heat exchange system comprises a first circulating device, a second circulating device, an output circulating device and a cascade device, the first circulation device comprises a first circulation loop, the second circulation device comprises a second circulation loop, the output circulation device comprises an output pipeline, a first condenser of the first circulation loop, a heat exchange unit of the second circulation loop and a second evaporator of the output pipeline are all located in the cascade device, and the second evaporator is located on the outermost layer. The heat exchange unit is located between the first condenser and the second evaporator.

Description

Technical Field

[0001] The invention relates to the technical field of heat exchange equipment, and in particular to an all-natural working fluid cascade heat exchange system. Background Art

[0002] As people's requirements for living environment increase, the demand for heating in winter and cooling in summer is gradually increasing. As the efforts to protect the environment and reduce carbon emissions gradually increase, especially for winter heating, more and more regions are using new environmentally friendly all-natural refrigerants to replace traditional fossil energy and conventional refrigerants.

[0003] For traditional fossil energy, the thermal energy of fossil energy is directly transferred through combustion to achieve heat exchange. Due to environmental protection requirements and its own thermodynamic characteristics, conventional refrigerant heat pumps cannot absorb heat from the air well and achieve heating in extremely cold areas or even some cold areas. For all-natural refrigerants, heat exchange is achieved by the transformation of form, that is, the conversion between gas, gas-liquid and liquid. However, at this stage, there is no heat exchange system for all-natural refrigerants that can both guarantee heat exchange efficiency and reduce heat loss.

[0004] Therefore, from the perspectives of environmental protection, improving heat exchange efficiency, and increasing safety factor, the present invention provides a full-natural working fluid cascade heat exchange system to solve the problems existing in the prior art to a certain extent. Summary of the invention

[0005] The object of the present invention is to provide a fully natural working fluid cascade heat exchange system to optimize the structure of the heat exchange system to a certain extent, improve the heat exchange efficiency and reduce heat loss.

[0006] The present invention provides an all-natural working fluid cascade heat exchange system, comprising a first circulation device, a second circulation device, an output circulation device and a cascade device; the first circulation device comprises a first circulation loop, the second circulation device comprises a second circulation loop, the output circulation device comprises an output pipeline, and the first condenser of the first circulation loop, the heat exchange unit of the second circulation loop and the second evaporator of the output pipeline are all located in the cascade device, and the second evaporator is located in the outermost layer, and the heat exchange unit is located between the first condenser and the second evaporator.

[0007] Wherein, the heat exchange unit includes a first evaporator and a second condenser, the first evaporator is located outside the first condenser, the second condenser is located outside the first evaporator, and the second evaporator is located outside the second condenser; the refrigerant flow direction in the first condenser is opposite to the refrigerant flow direction of the first evaporator, the refrigerant flow direction in the first evaporator is opposite to the refrigerant flow direction of the second condenser, and the refrigerant flow direction in the second condenser is opposite to the refrigerant flow direction of the second evaporator.

[0008] Specifically, the first circulation device includes a first compressor, and the second circulation device includes a second compressor; the first compressor is arranged on the first circulation loop, and the outlet of the first compressor can supply refrigerant to the first condenser, and the refrigerant passing through the first condenser flows back to the first compressor circulation from the first circulation loop; the second compressor is arranged on the second circulation loop, and the outlet of the second compressor can supply refrigerant to the second condenser, and after flowing through the first evaporator through the second circulation loop, it flows back to the second compressor circulation.

[0009] Furthermore, the first circulation device also includes a first oil-gas separator, and the second circulation device also includes a second oil-gas separator. The first oil-gas separator is located on the first circulation loop between the outlet of the first compressor and the first condenser; the second oil-gas separator is located on the second circulation loop between the outlet of the second compressor and the second condenser.

[0010] Furthermore, the first circulation device also includes a first liquid reservoir, and the second circulation device also includes a second liquid reservoir. The first liquid reservoir is arranged on a first circulation loop connected to the outlet of the first condenser; the second liquid reservoir is arranged on a second circulation loop connected to the outlet of the second condenser.

[0011] Furthermore, the first circulation device also includes a first expansion valve, and the second circulation device also includes a second expansion valve; the first expansion valve is arranged on a first circulation loop connected to the outlet of the first liquid reservoir, and is located between the first liquid reservoir and the first compressor; the second expansion valve is arranged on a second circulation loop connected to the outlet of the second liquid reservoir, and is located between the second liquid reservoir and the first evaporator.

[0012] Wherein, the first circulation device further includes an evaporator, and the evaporator is arranged on the first circulation loop and located between the first expansion valve and the compressor.

[0013] Specifically, the first circulation device also includes a first gas-liquid separator, and the second circulation device also includes a second gas-liquid separator; the first gas-liquid separator is arranged on the first circulation loop between the evaporator and the inlet of the first compressor, and the second gas-liquid separator is arranged on the second circulation loop between the first evaporator and the inlet of the second compressor.

[0014] Furthermore, the output circulation device also includes an output supply component and a heat using unit, the output supply component is arranged on the output pipeline and is located at the outlet of the second evaporator, the output end of the output supply component is connected to the inlet of the heat using unit, and the reflux end of the heat using unit is connected to the inlet of the second evaporator.

[0015] Compared with the prior art, the all-natural working fluid cascade heat exchange system provided by the present invention has the following advantages:

[0016] The all-natural working fluid cascade heat exchange system provided by the present invention comprises a first circulation device, a second circulation device, an output circulation device and a cascade device; the first circulation device comprises a first circulation loop, the second circulation device comprises a second circulation loop, the output circulation device comprises an output pipeline, and the first condenser of the first circulation loop, the heat exchange unit of the second circulation loop and the second evaporator of the output pipeline are all located in the cascade device, and the second evaporator is located in the outermost layer, and the heat exchange unit is located between the first condenser and the second evaporator.

[0017] From this analysis, it can be seen that the circulation of one refrigerant can be achieved through the first circulation device, and the circulation of another refrigerant can be achieved through the second circulation device. Correspondingly, the circulation of the refrigerant to be heated can be achieved through the output circulation device. In addition, since a cascade device is provided in the system provided in the present application, and the first condenser of the first circulation loop is arranged in the cascade device, the heat exchange unit of the second circulation loop is arranged in the cascade device, and the second evaporator of the output pipeline is also arranged in the cascade device, the first condenser is located in the innermost layer, the heat exchange unit is located between the first condenser and the second evaporator, and the second evaporator is located in the outermost layer. Therefore, through the continuous circulation of the first circulation device, the temperature carried by the internally circulating refrigerant can be transferred to the refrigerant flowing through the heat exchange unit, thereby realizing heat exchange between the first circulation device and the second circulation device.

[0018] Correspondingly, the heat exchange unit of the second circulation device can also exchange heat with the second evaporator of the outer layer, so that the heat can be transferred to the second evaporator, thereby achieving the final heat output.

[0019] It can be understood that since the first condenser, the heat exchange unit and the second evaporator adopt a stacked design in the present application, the distance between the first condenser and the heat exchange unit and the distance between the heat exchange unit and the second evaporator are closer, so the heat exchange efficiency can be improved to a certain extent. At the same time, since the heat exchange process occurs in the formed cascade device and the second evaporator is coated in the outermost layer, even if there is dissipated heat from the first condenser and the heat exchange unit, this part of the heat will eventually be transferred to the second evaporator in the outer layer, thereby greatly reducing heat loss and ensuring the heat exchange effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of the overall structure of the all-natural working fluid cascade heat exchange system provided by an embodiment of the present invention;

[0022] Figure 2 A schematic structural diagram of a cascade device in an all-natural working fluid cascade heat exchange system provided in an embodiment of the present invention.

[0023] In the figure: 1-first circulation loop; 101-first condenser; 2-first compressor; 3-first oil-gas separator; 4-first liquid storage tank; 5-first expansion valve; 6-evaporator; 7-first gas-liquid separator; 8-second circulation loop; 801-heat exchange unit; 8011-first evaporator; 8012-second condenser; 9-second compressor; 10-second oil-gas separator; 11-second liquid storage tank; 12-second expansion valve; 13-second gas-liquid separator; 14-output pipeline; 1401-second evaporator. DETAILED DESCRIPTION

[0024] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0025] In the description of the embodiments of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or are the positions or positional relationships in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0026] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more items.

[0029] For ease of description, spatial relative terms such as "above", "upper", "below", and "lower" may be used herein to describe the relationship of one element to another element as shown in the drawings. Such spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings.

[0030] The terms used herein are only used to describe various examples and are not used to limit the present disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms "include", "comprise" and "have" list the stated features, quantities, operations, components, elements and / or their combinations that exist, but do not exclude the existence or addition of one or more other features, quantities, operations, components, elements and / or their combinations.

[0031] Variations in the shapes shown in the drawings may occur due to manufacturing techniques and / or tolerances. Therefore, the examples described herein are not limited to the specific shapes shown in the drawings but include variations in shapes that occur during manufacturing.

[0032] The features of the examples described herein may be combined in various ways that will be apparent after understanding the disclosure of the present application. In addition, although the examples described herein have various configurations, other configurations are possible as will be apparent after understanding the disclosure of the present application. In addition, the technical solutions between the various embodiments may be combined with each other, but must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be considered that the combination of such technical solutions does not exist and is not within the scope of protection required by the present application.

[0033] like Figure 1 As shown, the present invention provides an all-natural working fluid cascade heat exchange system, including a first circulation device, a second circulation device, an output circulation device and a cascade device; the first circulation device includes a first circulation loop 1, the second circulation device includes a second circulation loop 8, the output circulation device includes an output pipeline 14, and the first condenser 101 of the first circulation loop 1 and the heat exchange unit 801 of the second circulation loop 8 and the second evaporator 1401 of the output pipeline 14 are all located in the cascade device, and the second evaporator 1401 is located at the outermost layer, and the heat exchange unit 801 is located between the first condenser 101 and the second evaporator 1401.

[0034] Compared with the prior art, the all-natural working fluid cascade heat exchange system provided by the present invention has the following advantages:

[0035] The all-natural working fluid cascade heat exchange system provided by the present invention can realize the circulation of one refrigerant through the first circulation device, and can realize the circulation of another refrigerant through the second circulation device. Correspondingly, the circulation of the refrigerant to be heated can be realized through the output circulation device. In addition, since a cascade device is provided in the system provided by the present application, and the first condenser 101 of the first circulation loop 1 is arranged in the cascade device, the heat exchange unit 801 of the second circulation loop 8 is arranged in the cascade device, and the second evaporator 1401 of the output pipeline 14 is also arranged in the cascade device, the first condenser 101 is located in the innermost layer, the heat exchange unit 801 is located between the first condenser 101 and the second evaporator 1401, and the second evaporator 1401 is located in the outermost layer. Therefore, through the continuous circulation of the first circulation device, the temperature carried by the internally circulating refrigerant can be transferred to the refrigerant flowing through the heat exchange unit 801, thereby realizing heat exchange between the first circulation device and the second circulation device.

[0036] Correspondingly, the heat exchange unit 801 of the second circulation device can also exchange heat with the second evaporator 1401 of the outer layer, so that the heat can be transferred to the second evaporator 1401, thereby achieving the final heat output.

[0037] It can be understood that since the first condenser 101, the heat exchange unit 801 and the second evaporator 1401 adopt a stacked design in the present application, the distance between the first condenser 101 and the heat exchange unit 801 and between the heat exchange unit 801 and the second evaporator 1401 is closer, so the heat exchange efficiency can be improved to a certain extent. At the same time, since the heat exchange process occurs in the formed cascade device and the second evaporator 1401 is coated in the outermost layer, even if there is dissipated heat from the first condenser 101 and the heat exchange unit 801, this part of the heat will eventually be transferred to the outer layer of the second evaporator 1401, thereby greatly reducing the heat loss and ensuring the heat exchange effect.

[0038] Alternatively, if Figure 1 As shown, the heat exchange unit 801 in the present application includes a first evaporator 8011 and a second condenser 8012, the first evaporator 8011 is located outside the first condenser 101, the second condenser 8012 is located outside the first evaporator 8011, and the second evaporator 1401 is located outside the second condenser 8012; the refrigerant flow direction in the first condenser 101 is opposite to the refrigerant flow direction of the first evaporator 8011, the refrigerant flow direction in the first evaporator 8011 is opposite to the refrigerant flow direction of the second condenser 8012, and the refrigerant flow direction in the second condenser 8012 is opposite to the refrigerant flow direction of the second evaporator 1401.

[0039] Combination Figure 2It can be seen from the structural schematic diagram of the cascade device that the first condenser 101 in the present application is a straight tube structure, and the refrigerant flows from one end to the other end with a unique flow direction. However, since the first condenser 101 is located in the innermost layer, the final overall cascade device needs to extend a first inlet and a first outlet (not shown in the figure) that are connected to both ends of the first condenser 101 and pass through the second evaporator 1401.

[0040] Accordingly, the first evaporator 8011 and the second condenser 8012 in the present application may be two independent tube structures, or may be an integral tube structure with a partition disposed inside to separate the internal chambers, or may be a plurality of separate tube structures. Figure 2 The structure shown is directly a cavity, and the inner layer and outer layer mentioned above are actually for distinguishing the internal refrigerant, that is, when the first evaporator 8011 and the second condenser 8012 are a tube body, the area close to the first condenser 101 is the first evaporator 8011, and the area close to the second evaporator 1401 is the second condenser 8012. In this case, the heat exchange unit 801 has only one inlet and one outlet.

[0041] This application takes two independent tube structures as an example, the second condenser 8012 and the first evaporator 8011 are fitted together in the cascade device, and the second inlet of the second condenser 8012 passes through the second evaporator 1401 and docks with the second circulation loop 8, and the second outlet can be connected with the first evaporator 8011 in the cascade device to save the number of extended interfaces, and the second evaporator 1401 can also be extended to dock with the second circulation loop 8, and the second circulation loop 8 is used to allow the internal refrigerant to enter from the third inlet of the first evaporator 8011. In this case, the third inlet of the first evaporator 8011 also needs to extend out of the second evaporator 1401 and dock with the second circulation loop 8 to achieve the introduction of refrigerant. Accordingly, the third outlet of the first evaporator 8011 extends out of the second evaporator 1401 and docks with the second circulation loop 8 to achieve the circulation of the refrigerant.

[0042] Preferably, the overall length of the heat exchange unit 801 provided in the present application is smaller than the overall length of the first condenser 101. Therefore, both the first inlet and the first outlet of the first condenser 101 do not need to pass through the heat exchange unit 801, thereby reducing the complexity of the structure.

[0043] Furthermore, since the flow direction of the refrigerant in the outermost second evaporator 1401 in the present application is opposite to that of the refrigerant in the first condenser 101, in the actual structure, the fourth inlet of the second evaporator 1401 is close to the first outlet of the first condenser 101, and the fourth outlet of the second evaporator 1401 is close to the first inlet of the first condenser 101. Therefore, when the refrigerant enters the second evaporator 1401 from the fourth inlet, it can be preheated by the refrigerant flowing out of the first condenser 101, thereby improving the heat exchange efficiency.

[0044] It should be additionally explained here that in the present application, the refrigerant circulating in the first circulation device is carbon dioxide refrigerant, the refrigerant circulating in the second circulation device is R600a refrigerant, and the refrigerant circulating in the output circulation device is water.

[0045] By using all-natural working fluids, the impact of refrigerants on the environment can be reduced, helping to reduce carbon emissions and increase efficiency.

[0046] Alternatively, if Figure 1 As shown, the first circulation device in the present application includes a first compressor 2, and the second circulation device includes a second compressor 9; the first compressor 2 is arranged on the first circulation loop 1, and the outlet of the first compressor 2 can supply the refrigerant to the first condenser 101, and the refrigerant passing through the first condenser 101 flows back from the first circulation loop 1 to the first compressor 2 for circulation; the second compressor 9 is arranged on the second circulation loop 8, and the outlet of the second compressor 9 can supply the refrigerant to the second condenser 8012, and after flowing through the first evaporator 8011 through the second circulation loop 8, it flows back to the second compressor 9 for circulation.

[0047] The first compressor 2 included in the first circulation device can convert the above-mentioned carbon dioxide refrigerant from liquid to high-temperature gas. Since the outlet of the first compressor 2 is connected to the first condenser 101 through the first circulation loop 1, the high-temperature gaseous carbon dioxide refrigerant can enter the first condenser 101 for heat exchange and transfer the heat to the R600a in the heat exchange unit 801.

[0048] After the heat exchange is completed, the gaseous carbon dioxide refrigerant is converted into liquid again, flows back to the first compressor 2 through the first circulation loop 1 and is converted into gas again, thereby realizing the circulation of the refrigerant.

[0049] Correspondingly, the above-mentioned R600a refrigerant can be supplied to the heat exchange unit 801 through the second compressor 9, and after heat exchange, it flows back to the second compressor 9 through the second circulation loop 8 to realize the circulation of R600a.

[0050] Alternatively, if Figure 1As shown, the first circulation device also includes a first oil-gas separator 3, and the second circulation device also includes a second oil-gas separator 10. The first oil-gas separator 3 is located on the first circulation loop 1 between the outlet of the first compressor 2 and the first condenser 101; the second oil-gas separator 10 is located on the second circulation loop 8 between the outlet of the second compressor 9 and the second condenser 8012.

[0051] Since the coolant is in a gas-liquid mixed state during the circulation process, in order to ensure that the refrigerant passing through the first condenser 101 and the heat exchange unit 801 is in a unique form, the gaseous refrigerant and the liquid refrigerant can be separated by the first oil-gas separator 3 and the second oil-gas separator 10, thereby achieving the stability of the overall heat exchange system.

[0052] Alternatively, if Figure 1 As shown, the first circulation device also includes a first liquid reservoir 4, and the second circulation device also includes a second liquid reservoir 11. The first liquid reservoir 4 is arranged on the first circulation loop 1 connected to the outlet of the first condenser 101; the second liquid reservoir 11 is arranged on the second circulation loop 8 connected to the outlet of the second condenser 8012.

[0053] The first liquid storage tank 4 in the present application is located at the outlet of the first condenser 101, and the second liquid storage tank 11 is located at the outlet of the second condenser 8012, which can store a certain amount of refrigerant to a certain extent to ensure the stability of the cycle.

[0054] Alternatively, if Figure 1 As shown, the first circulation device also includes a first expansion valve 5, and the second circulation device also includes a second expansion valve 12; the first expansion valve 5 is arranged on the first circulation loop 1 connected to the outlet of the first liquid reservoir 4, and is located between the first liquid reservoir 4 and the first compressor 2; the second expansion valve 12 is arranged on the second circulation loop 8 connected to the outlet of the second liquid reservoir 11, and is located between the second liquid reservoir 11 and the first evaporator 8011.

[0055] By setting the first expansion valve 5 and the second expansion valve 12, the refrigerant flow rate can be adjusted according to the heat exchange demand to ensure a constant output temperature. In addition, by setting the first expansion valve 5 and the second expansion valve 12, the refrigerant can be converted into low-temperature and low-pressure wet steam, so that rapid heat exchange can be achieved between the first evaporator 8011 and the first condenser 101 and the second evaporator 1401.

[0056] Accordingly, if Figure 1As shown, since the first circulation device in the present application further includes an evaporator 6, the evaporator 6 is arranged on the first circulation loop 1 and is located between the first expansion valve 5 and the compressor, the low-temperature wet steam output by the first expansion valve 5 can be heat exchanged at the evaporator 6 to provide a cold source for the unit with a cooling demand. After heat exchange at the evaporator 6, the refrigerant is heated, thereby reducing the energy consumption of the first compressor 2 to a certain extent.

[0057] Alternatively, if Figure 1 As shown, the all-natural working fluid cascade heat exchange system provided by the present invention also includes a first gas-liquid separator 7, and the second circulation device also includes a second gas-liquid separator 13; the first gas-liquid separator 7 is arranged on the first circulation loop 1 between the evaporator 6 and the inlet of the first compressor 2, and the second gas-liquid separator 13 is arranged on the second circulation loop 8 between the first evaporator 8011 and the inlet of the second compressor 9.

[0058] Since the refrigerant required by the first compressor 2 and the second compressor 9 is in a vapor state, in order to prevent water from entering the first compressor 2 and the second compressor 9, the present application arranges a first gas-liquid separator 7 and a second gas-liquid separator 13 in front of the inlet of the first compressor 2 and the second compressor 9, thereby ensuring the state of the refrigerant supplied to the first compressor 2 and the second compressor 9 and improving the overall system operation stability and structural life.

[0059] It can be understood that the output circulation device in the present application also includes an output supply component and a heat unit. The output supply component is arranged on the output pipeline 14 and is located at the outlet of the second evaporator 1401. The output end of the output supply component is connected to the inlet of the heat unit, and the reflux end of the heat unit is connected to the inlet of the second evaporator 1401.

[0060] The output supply component in the present application may be a circulating pump or other equipment, through which water can be circulated between the heat-using unit and the second evaporator 1401, thereby providing a stable heat supply to the heat-using unit.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An all-natural working fluid cascade heat exchange system, characterized in that: It includes a first circulation device, a second circulation device, an output circulation device and a cascading device; The first circulation device includes a first circulation loop, the second circulation device includes a second circulation loop, the output circulation device includes an output pipeline, and the first condenser of the first circulation loop, the heat exchange unit of the second circulation loop and the second evaporator of the output pipeline are all located in the cascade device, and the second evaporator is located in the outermost layer, and the heat exchange unit is located between the first condenser and the second evaporator.

2. The all-natural working fluid cascade heat exchange system according to claim 1, characterized in that: The heat exchange unit comprises a first evaporator and a second condenser, wherein the first evaporator is located outside the first condenser, the second condenser is located outside the first evaporator, and the second evaporator is located outside the second condenser; The refrigerant flow direction in the first condenser is opposite to that in the first evaporator, the refrigerant flow direction in the first evaporator is opposite to that in the second condenser, and the refrigerant flow direction in the second condenser is opposite to that in the second evaporator.

3. The all-natural working fluid cascade heat exchange system according to claim 2, characterized in that: The first circulation device includes a first compressor, and the second circulation device includes a second compressor; The first compressor is arranged on the first circulation loop, and the outlet of the first compressor can supply the refrigerant to the first condenser, and the refrigerant passing through the first condenser flows back to the first compressor circulation through the first circulation loop; The second compressor is arranged on the second circulation loop, and the outlet of the second compressor can supply the refrigerant to the second condenser, and after passing through the first evaporator through the second circulation loop, the refrigerant flows back to the second compressor circulation.

4. The all-natural working fluid cascade heat exchange system according to claim 3, characterized in that: The first circulation device further includes a first oil-gas separator, and the second circulation device further includes a second oil-gas separator, wherein the first oil-gas separator is located on a first circulation loop between an outlet of the first compressor and the first condenser; The second oil-gas separator is located on the second circulation loop between the outlet of the second compressor and the second condenser.

5. The all-natural working fluid cascade heat exchange system according to claim 3, characterized in that: The first circulation device further comprises a first liquid reservoir, and the second circulation device further comprises a second liquid reservoir, wherein the first liquid reservoir is arranged on a first circulation loop connected to an outlet of the first condenser; The second liquid receiver is disposed on a second circulation loop connected to an outlet of the second condenser.

6. The all-natural working fluid cascade heat exchange system according to claim 5, characterized in that: The first circulation device further comprises a first expansion valve, and the second circulation device further comprises a second expansion valve; The first expansion valve is arranged on a first circulation loop connected to the outlet of the first liquid reservoir and is located between the first liquid reservoir and the first compressor; The second expansion valve is arranged on a second circulation loop connected to an outlet of the second liquid reservoir and is located between the second liquid reservoir and the first evaporator.

7. The all-natural working fluid cascade heat exchange system according to claim 6, characterized in that: The first circulation device further includes an evaporator, which is disposed on the first circulation loop and located between the first expansion valve and the compressor.

8. The all-natural working fluid cascade heat exchange system according to claim 7, characterized in that: The first circulation device further comprises a first gas-liquid separator, and the second circulation device further comprises a second gas-liquid separator; The first gas-liquid separator is disposed on a first circulation loop between the evaporator and an inlet of the first compressor, and the second gas-liquid separator is disposed on a second circulation loop between the first evaporator and an inlet of the second compressor.

9. The all-natural working fluid cascade heat exchange system according to claim 1, characterized in that: The output circulation device also includes an output supply component and a heat using unit. The output supply component is arranged on the output pipeline and is located at the outlet of the second evaporator. The output end of the output supply component is connected to the inlet of the heat using unit, and the reflux end of the heat using unit is connected to the inlet of the second evaporator.

10. The all-natural working fluid cascade heat exchange system according to claim 1, characterized in that: The refrigerant circulating in the first circulation device is carbon dioxide refrigerant, the refrigerant circulating in the second circulation device is R600a refrigerant, and the refrigerant circulating in the output circulation device is water.

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