阅读说明：本技术 冷却系统 (Cooling system ) 是由 查世彤 于 2020-02-07 设计创作，主要内容包括：一种冷却系统,该冷却系统包括高侧热交换器、热交换器、闪蒸罐、第一膨胀阀、第二膨胀阀、负载、第一压缩机和第二压缩机。在第一操作模式期间,第二膨胀阀将制冷剂从闪蒸罐引导至负载。来自负载的制冷剂绕过第一压缩机。热交换器将热量从来自高侧热交换器的制冷剂传递到来自负载的制冷剂。第二压缩机压缩来自热交换器的制冷剂。在第二操作模式期间,第一膨胀阀将制冷剂从闪蒸罐引导至负载。第一压缩机压缩来自负载的制冷剂,并且第二压缩机在来自第一压缩机的制冷剂到达高侧热交换器之前压缩来自第一压缩机的制冷剂。(A cooling system includes a high side heat exchanger, a flash tank, a first expansion valve, a second expansion valve, a load, a first compressor, and a second compressor. During the first mode of operation, the second expansion valve directs refrigerant from the flash tank to the load. Refrigerant from the load bypasses the first compressor. The heat exchanger transfers heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load. The second compressor compresses the refrigerant from the heat exchanger. During the second mode of operation, the first expansion valve directs refrigerant from the flash tank to the load. The first compressor compresses refrigerant from the load, and the second compressor compresses refrigerant from the first compressor before the refrigerant from the first compressor reaches the high side heat exchanger.)

1. An apparatus, comprising:

a high-side heat exchanger configured to remove heat from refrigerant;

a heat exchanger;

a flash tank configured to store the refrigerant;

a first expansion valve;

a second expansion valve;

a load;

a first compressor; and

a second compressor that, during a first mode of operation:

the first expansion valve is closed;

the second expansion valve directing refrigerant from the flash tank to the load;

the load cooling a space near the load using the refrigerant from the second expansion valve;

the first compressor is off, the refrigerant from the load bypasses the first compressor;

the heat exchanger transferring heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load, and after transferring heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load, the heat exchanger directing the refrigerant from the load to the second compressor; and is

The second compressor compresses the refrigerant from the heat exchanger;

during a second mode of operation:

the first expansion valve directing refrigerant from the flash tank to the load;

the second expansion valve is closed;

the load cooling the space using the refrigerant from the first expansion valve;

the first compressor compressing the refrigerant from the load;

the heat exchanger is closed; and is

The second compressor compresses the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high-side heat exchanger.

2. The apparatus of claim 1, wherein the first mode of operation ends and the second mode of operation begins when the temperature of the space is below a threshold.

3. The apparatus of claim 1, wherein the load is a blast freezer.

4. The apparatus of claim 1, further comprising a heat reducer that removes heat from the refrigerant from the first compressor before the refrigerant from the first compressor reaches the second compressor during the second mode of operation.

5. The apparatus of claim 1, further comprising a valve that directs the refrigerant from the load to the heat exchanger bypassing the first compressor during the first mode of operation.

6. The apparatus of claim 5, wherein the valve is a three-way valve that directs refrigerant from the load to the first compressor during the second mode of operation.

7. The apparatus of claim 1, further comprising an oil separator configured to separate oil from the refrigerant from the second compressor.

8. A method, comprising:

removing heat from the refrigerant by the high side heat exchanger;

storing the refrigerant by a flash tank;

during a first mode of operation:

directing refrigerant from the flash tank to a load by a first expansion valve;

cooling, by the load, a space near the load using the refrigerant from the first expansion valve, the refrigerant from the load bypassing a first compressor;

transferring heat from the refrigerant from the high side heat exchanger to the refrigerant from the load by a heat exchanger;

directing, by the heat exchanger, the refrigerant from the load to a first compressor after heat of the refrigerant from the high-side heat exchanger is transferred to the refrigerant from the load; and

compressing the refrigerant from the heat exchanger by the first compressor; during a second mode of operation:

directing refrigerant from the flash tank to the load by a second expansion valve;

cooling, by the load, the space using the refrigerant from the second expansion valve;

compressing the refrigerant from the load by a second compressor; and

compressing, by the first compressor, the refrigerant from the second compressor before the refrigerant from the second compressor reaches the high-side heat exchanger.

9. The method of claim 8, wherein the first mode of operation ends and the second mode of operation begins when the temperature of the space is below a threshold.

10. The method of claim 8, wherein the load is a blast freezer.

11. The method of claim 8, further comprising: during the second mode of operation, heat is removed from the refrigerant from the second compressor by a heat reducer before the refrigerant from the second compressor reaches the first compressor.

12. The method of claim 8, further comprising: during the first mode of operation, the refrigerant from the load is directed by a valve to the heat exchanger bypassing the second compressor.

13. The method of claim 12, further comprising: directing, by the valve, the refrigerant from the load to the second compressor during the second mode of operation, wherein the valve is a three-way valve.

14. The method of claim 8, further comprising separating oil from the refrigerant from the first compressor by an oil separator.

15. An apparatus, comprising:

a high-side heat exchanger configured to remove heat from refrigerant;

a heat exchanger;

a flash tank configured to store the refrigerant;

a first expansion valve;

a second expansion valve;

a load;

a valve;

a first compressor; and

a second compressor that, during a first mode of operation:

the first expansion valve is closed;

the second expansion valve directing refrigerant from the flash tank to the load;

the load cooling a space near the load using the refrigerant from the second expansion valve;

the first compressor is off;

the valve directs the refrigerant from the load to the heat exchanger bypassing the first compressor;

the heat exchanger transferring heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load, and after transferring heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load, the heat exchanger directing the refrigerant from the load to the second compressor; and is

The second compressor compresses the refrigerant from the heat exchanger;

during a second mode of operation:

the first expansion valve directing refrigerant from the flash tank to the load;

the second expansion valve is closed;

the load cooling the space using the refrigerant from the first expansion valve;

the first compressor compressing the refrigerant from the load;

the heat exchanger is closed; and is

The second compressor compresses the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high-side heat exchanger.

16. The apparatus of claim 15, wherein the first mode of operation ends and the second mode of operation begins when the temperature of the space is below a threshold.

17. The apparatus of claim 15, wherein the load is a blast freezer.

18. The apparatus of claim 15, further comprising a heat reducer that removes heat from the refrigerant from the first compressor before the refrigerant from the first compressor reaches the second compressor during the second mode of operation.

19. The apparatus of claim 15, wherein the valve is a three-way valve that directs refrigerant from the load to the first compressor during the second mode of operation.

20. The apparatus of claim 15, further comprising an oil separator configured to separate oil from the refrigerant from the second compressor.

Technical Field

The present disclosure relates generally to cooling systems.

Background

Cooling systems are used to cool spaces such as refrigeration units and air flow freezers.

These systems circulate a refrigerant (also referred to as a charge) for cooling the space.

Disclosure of Invention

Cooling systems such as refrigeration units and air flow freezers are used to cool spaces. These systems circulate a refrigerant (e.g., carbon dioxide) that is used to cool the space. The refrigerant is used by the load to cool a space near the load. For example, the refrigeration unit and the air flow freezer may use a refrigerant to cool the space within the refrigeration unit and the air flow freezer. The refrigerant is then compressed by a compressor to concentrate the heat absorbed in the refrigerant at the load, thereby making it easier to remove the heat. However, problems can arise at system start-up. Because the temperature of the space to be cooled is typically highest at start-up, the system works best at start-up to cool the space. As a result, the refrigerant at the load absorbs the most heat at start-up and the pressure of the refrigerant increases, sometimes so quickly as to cause the compressor to shutdown.

In certain embodiments, the present disclosure contemplates an unconventional cooling system that reduces the chances of compressor shutdown during startup. At start-up, refrigerant for cooling a load is directed to a first compressor designed to compress refrigerant for cooling a space to a higher temperature (e.g., a refrigeration temperature). After the space is cooled to a particular temperature (e.g., 10 degrees fahrenheit), the system transitions to a post-startup to cool the space to an even lower temperature (e.g., a blast chill temperature). During a post start, refrigerant from the load is first compressed by a second compressor designed to compress refrigerant used to cool the space to these lower temperatures. The first compressor then compresses the refrigerant from the second compressor. In this way, the second compressor is protected from shutdown during startup. Certain embodiments of the cooling system are discussed below.

According to one embodiment, an apparatus includes a high side heat exchanger, a flash tank, a first expansion valve, a second expansion valve, a load, a first compressor, and a second compressor. The high side heat exchanger removes heat from the refrigerant. The flash tank stores refrigerant. During the first mode of operation, the first expansion valve is closed and the second expansion valve directs refrigerant from the flash tank to the load. The load cools a space near the load using refrigerant from the second expansion valve, and the first compressor is turned off. Refrigerant from the load bypasses the first compressor. The heat exchanger transfers heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load, and guides the refrigerant from the load to the second compressor after transferring heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load. The second compressor compresses the refrigerant from the heat exchanger. During a second mode of operation, the first expansion valve directs refrigerant from the flash tank to the load, and the second expansion valve is closed. The load cools the space using the refrigerant from the first expansion valve, and the first compressor compresses the refrigerant from the load. The heat exchanger is closed and the second compressor compresses the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high side heat exchanger.

According to another embodiment, a method includes removing heat from refrigerant by a high side heat exchanger and storing the refrigerant by a flash tank. During a first mode of operation, the method includes directing refrigerant from the flash tank to the load through a first expansion valve and cooling a space near the load with refrigerant from the first expansion valve through the load. Refrigerant from the load bypasses the first compressor. The method further comprises the following steps: transferring heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load through the heat exchanger; directing the refrigerant from the load to the first compressor through the heat exchanger after heat is transferred from the refrigerant from the high-side heat exchanger to the refrigerant from the load; and compressing the refrigerant from the heat exchanger by the first compressor. During a second mode of operation, the method includes directing refrigerant from the flash tank to the load through the second expansion valve and cooling the space through the load using refrigerant from the second expansion valve. The method further comprises the following steps: compressing, by a second compressor, refrigerant from a load; and compressing the refrigerant from the second compressor by the first compressor before the refrigerant from the second compressor reaches the high-side heat exchanger.

According to yet another embodiment, a system includes a high side heat exchanger, a flash tank, a first expansion valve, a second expansion valve, a load, a valve, a first compressor, and a second compressor. The high side heat exchanger removes heat from the refrigerant. The flash tank stores refrigerant. During the first mode of operation, the first expansion valve is closed and the second expansion valve directs refrigerant from the flash tank to the load. The load cools a space near the load using refrigerant from the second expansion valve, and the first compressor is turned off. The valve directs refrigerant from the load to the heat exchanger bypassing the first compressor, and the heat exchanger transfers heat from the refrigerant from the high side heat exchanger to the refrigerant from the load. The heat exchanger directs the refrigerant from the load to the second compressor after heat is transferred from the refrigerant from the high side heat exchanger to the refrigerant from the load and the second compressor compresses the refrigerant from the heat exchanger. During a second mode of operation, the first expansion valve directs refrigerant from the flash tank to the load, and the second expansion valve is closed. The load cools the space using the refrigerant from the first expansion valve, and the first compressor compresses the refrigerant from the load. The heat exchanger is closed and the second compressor compresses the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high side heat exchanger.

Certain embodiments provide one or more technical advantages. For example, one embodiment protects the compressor from shutdown during startup. As another example, one embodiment provides stable operation and control with one rack. Some embodiments may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art from the figures, descriptions, and claims included herein.

Drawings

For a more complete understanding of this disclosure, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an example cooling system;

FIG. 2 illustrates an example cooling system;

FIG. 3 is a flow chart illustrating a method of operating an example cooling system.

Detailed Description

Embodiments of the present disclosure and its advantages are best understood by referring to figures 1 through 3 of the drawings, like numerals being used for like and corresponding parts of the various drawings.

Cooling systems such as refrigeration units and air flow freezers are used to cool spaces. These systems circulate a refrigerant (e.g., carbon dioxide) that is used to cool the space. The refrigerant is used by the load to cool a space near the load. For example, the refrigeration unit and the air flow freezer may use a refrigerant to cool the space within the refrigeration unit and the air flow freezer. The refrigerant is then compressed by a compressor to concentrate the heat absorbed in the refrigerant at the load, thereby making it easier to remove the heat. However, problems can arise at system start-up. Because the temperature of the space to be cooled is typically highest at start-up, the system works best at start-up to cool the space. As a result, the refrigerant at the load absorbs the most heat at start-up and the pressure of the refrigerant increases, sometimes so quickly as to cause the compressor to shutdown.

In certain embodiments, the present disclosure contemplates an unconventional system that reduces the chances of compressor shutdown during startup. At start-up, refrigerant for cooling a load is directed to a first compressor designed to compress refrigerant for cooling a space to a higher temperature (e.g., a refrigeration temperature). After the space is cooled to a particular temperature (e.g., 10 degrees fahrenheit), the system transitions to a post-startup to cool the space to an even lower temperature (e.g., a blast chill temperature). During a post start, refrigerant from the load is first compressed by a second compressor designed to compress refrigerant used to cool the space to these lower temperatures. The first compressor then compresses the refrigerant from the second compressor. In this way, the second compressor is protected from shutdown during startup. The cooling system will be described in more detail using fig. 1 to 3.

FIG. 1 illustrates an example cooling system 100. As seen in fig. 1, cooling system 100 includes high side heat exchanger 105, heat exchanger 110, flash tank 115, expansion valve 120, expansion valve 125, load 130, sensor 133, valve 135, low temperature compressor 140, desuperheater 145, valve 150, medium temperature compressor 155, and oil separator 160. Typically, the system 100 protects the cryogenic compressor 140 from shutdown during start-up by directing refrigerant from the load 130 to the intermediate temperature compressor 155, bypassing the cryogenic compressor 140. When the temperature of the load 130 is below the threshold, the system 100 begins directing refrigerant from the load 130 to the cryogenic compressor 140. As a result, in certain embodiments, the cryogenic compressor 140 is protected from start-up operating conditions.

Generally, the system 100 circulates a refrigerant to cool the load 130 and/or a space near the load 130. The refrigerant absorbs heat from the load 130 and/or the space near the load 130. The refrigerant is then compressed, making heat easier to remove from the refrigerant. As seen in system 100, refrigerant from load 130 may be compressed by a low temperature compressor 140 and/or a medium temperature compressor 155. However, the two compressors may be designed to compress refrigerant for cooling the space to different temperatures. For example, the medium temperature compressor 155 may be designed to compress a refrigerant for cooling a space to a refrigeration temperature, and the low temperature compressor 140 may be designed to compress a refrigerant for cooling a space to a freezing temperature. In some designs, the medium temperature compressor 155 may compress a mixture of a refrigerant for cooling a space to a refrigeration temperature and a refrigerant for cooling a space to a freezing temperature.

At system 100 start-up, load 130 is at its highest temperature. Thus, the refrigerant leaving the load 130 is at its highest temperature and/or pressure. The temperature and/or pressure of the refrigerant may be too high for the cryogenic compressor 140 to compress. If refrigerant is directed to the cryogenic compressor 140, the cryogenic compressor 140 may shut down, causing the system 100 to malfunction.

The present disclosure protects the cryogenic compressor 140 from shutdown during start-up by bypassing the cryogenic compressor 140 by directing refrigerant from the load 130 to the intermediate temperature compressor 155. After the load 130 has cooled to a particular threshold temperature (e.g., 10 degrees fahrenheit), the system 100 transitions to a post-startup mode and allows refrigerant from the load 130 to flow to the cryogenic compressor 140. In this manner, the cryogenic compressor 140 does not assume the task of compressing refrigerant from the load 130 during startup. The various components of the system 100 are described below.

The high-side heat exchanger 105 removes heat from the refrigerant (e.g., carbon dioxide). As heat is removed from the refrigerant, the refrigerant is cooled. The present disclosure contemplates the high side heat exchanger 105 operating as a condenser and/or a gas cooler. When operating as a condenser, the high-side heat exchanger 105 cools the refrigerant, causing the state of the refrigerant to change from a gas to a liquid. When operating as a gas cooler, the high-side heat exchanger 105 cools the gaseous refrigerant, and the refrigerant remains as a gas. In some configurations, the high side heat exchanger 105 is positioned such that heat removed from the refrigerant may be rejected to the air. For example, the high-side heat exchanger 105 may be positioned on a roof so that heat removed from the refrigerant may be discharged to the air. As another example, the high side heat exchanger 105 may be positioned on the outside of the building and/or on the side of the building. The present disclosure contemplates the use of any suitable refrigerant (e.g., carbon dioxide) in any of the disclosed cooling systems.

The heat exchanger 110 transfers heat between two fluids flowing through the heat exchanger 110. In the example of fig. 1, the heat exchanger 110 transfers heat from the refrigerant from the high-side heat exchanger 105 to the refrigerant from the load 130. During start-up, refrigerant from the load 130 bypasses the low temperature compressor 140 and flows through the heat exchanger 110. The heat exchanger 110 transfers heat from the refrigerant from the high-side heat exchanger 105 to the refrigerant from the load 130. In this manner, the refrigerant flowing to the flash tank 115 is further cooled and additional superheat is added to the refrigerant flowing to the medium temperature compressor 155. After heat transfer is complete, the heat exchanger 110 directs refrigerant from the high side heat exchanger 105 to the flash tank 115 and directs refrigerant from the load 130 to the medium temperature compressor 155. After the system 100 has completed startup, the heat exchanger 110 may be shut down. When heat exchanger 110 is turned off, the refrigerant may continue to flow through heat exchanger 110, but heat exchanger 110 does not transfer heat between the refrigerant flowing through heat exchanger 110.

The flash tank 115 stores refrigerant received from the high side heat exchanger 105. The present disclosure contemplates the flash tank 115 storing refrigerant in any state, such as liquid and/or gaseous. The refrigerant exiting the flash tank 115 is supplied to a low temperature load 120 and a medium temperature load 125. In some embodiments, flash gas and/or gaseous refrigerant is released from the flash tank 115. By releasing the flash gas, the pressure within the flash tank 115 may be reduced.

The expansion valves 120 and 125 control the flow of refrigerant. For example, when the expansion valve 120 or 125 is open, the refrigerant flows through the expansion valve 120 or 125. When the expansion valve 120 or 125 is closed, the refrigerant stops flowing through the expansion valve 120 or 125. In certain embodiments, the expansion valve 120 or 125 may be opened to varying degrees to adjust the amount of refrigerant flow. For example, the expansion valve 120 or 125 may be opened more to increase the flow of refrigerant. As another example, the expansion valve 120 or 125 may be opened less to reduce the flow of refrigerant. Accordingly, the expansion valve 120 or 125 directs refrigerant from the flash tank 115 to the load 130.

The expansion valve 120 or 125 is used to cool the refrigerant flowing through the expansion valve 120 or 125. The expansion valve 120 or 125 may receive refrigerant from any component of the system 200, such as the flash tank 115. The expansion valve 120 or 125 reduces the pressure and thus the temperature of the refrigerant. The temperature of the refrigerant may then decrease as the pressure decreases. As a result, the refrigerant entering the expansion valve 120 or 125 may be cooler when exiting the expansion valve 120 or 125. In certain embodiments, expansion valve 120 and expansion valve 125 cool the refrigerant to different temperatures. For example, the expansion valve 120 may cool the refrigerant to a higher temperature than the expansion valve 125. As a result, the refrigerant from expansion valve 120 cools load 130 to a higher temperature than the refrigerant from expansion valve 125. In other embodiments, the expansion valves 120 and 125 may be designed to handle different volumes of refrigerant. For example, expansion valve 125 may be designed to reduce the temperature of a larger volume of refrigerant per unit time as compared to expansion valve 120.

In certain embodiments, the expansion valve 120 is used in the system 100 during start-up and the expansion valve 125 is used after start-up is complete. During start-up, refrigerant from the flash tank 115 flows through the expansion valve 120. The expansion valve 125 is closed. The expansion valve 120 cools the refrigerant and directs the cold refrigerant to the load 130. The refrigerant cools the load 130 to a particular temperature. When the load 130 has cooled to this temperature, the system 100 transitions to a post-startup mode. During the post start mode, expansion valve 120 is closed and expansion valve 125 is open. From the flash tank 115, the refrigerant flows through an expansion valve 125. Expansion valve 125 cools the refrigerant to a lower temperature than expansion valve 120. Cooled refrigerant from expansion valve 125 is directed to load 130. The load 130 then uses the refrigerant from the expansion valve 125 to further cool the load 130 to an even colder temperature.

The load 130 uses a refrigerant to cool the load 130 or a space near the load 130. For example, the load 130 may be a gas flow freezer that uses a refrigerant to cool an interior space of the gas flow freezer and/or objects within the gas flow freezer. Refrigerant flows from the flash tank 115 to the load 130. When the refrigerant reaches the load 130, the refrigerant removes heat from the air surrounding the load 130. As a result, the air is cooled. The cooled air may then be circulated, for example, by a fan, to cool a space, such as the interior space of the load 130. As the refrigerant passes through the load 130, the refrigerant may change from a liquid state to a gaseous state as it absorbs heat. The present disclosure contemplates any number of loads 130 being included in any of the disclosed cooling systems.

The load 130 may be a refrigeration unit and/or an air flow freezer. During start-up, the load 130 uses refrigerant from the expansion valve 120 to cool the load 130 to a particular temperature, such as 10 degrees fahrenheit. When the load 130 has reached the particular temperature, the load 130 begins to use the refrigerant from the expansion valve 125 to further cool the load 130.

Sensor 133 is any suitable sensor for sensing the temperature of load 130. For example, if load 130 is a gas flow freezer, sensor 133 may detect the temperature within the gas flow freezer and/or the temperature of an object within the gas flow freezer. When sensor 133 detects that the temperature of load 130 has reached a particular threshold (e.g., 10 degrees fahrenheit), system 100 may end the startup mode and transition to a post-startup mode.

Valve 135 is a three-way valve that directs refrigerant from load 130 to either cryogenic compressor 140 or heat exchanger 110. During start-up, valve 135 receives refrigerant from load 130 and directs the refrigerant to heat exchanger 110, thereby bypassing cryogenic compressor 140. During post start-up, valve 135 receives refrigerant from load 130 and directs the refrigerant to cryogenic compressor 140. In this manner, the valve 135 controls the flow of refrigerant during start-up and post-start.

The cryogenic compressor 140 compresses refrigerant from the load 130 during a post start. The cryogenic compressor 140 may remain off during startup. By compressing the refrigerant from the load 130, the cryogenic compressor 140 concentrates the heat absorbed by the refrigerant at the load 130, making it easier to remove heat from the refrigerant as previously described. The cryogenic compressor 140 does not compress refrigerant from the load 130 during start-up because the cryogenic compressor 140 may be shut down if it is responsible for compressing refrigerant from the load 130 during start-up.

The desuperheater 145 removes heat from the refrigerant from the low temperature compressor 140. The desuperheater 145 can include metal tubes, plates, and/or fins that act as heat exchangers. The desuperheater 145 can also include one or more fans that circulate air over the metal components. As a result, heat from the refrigerant flowing through the metal components is transferred to the ambient air, thereby removing heat from the refrigerant in the desuperheater 145. Certain embodiments of the system 100 may not include the desuperheater 145.

The flash gas bypass valve controls the flow of flash gas discharged by the flash tank 115. For example, the flash gas bypass valve 150 may be opened to allow flash gas to flow from the flash tank 110 to the medium temperature compressor 155. The flash gas bypass valve 150 may be closed to stop the flow of flash gas in the flash tank 115. Thus, the flash gas bypass valve 150 may be used to regulate and/or maintain the internal pressure of the flash tank 115. For example, the internal pressure of the flash tank 115 may be reduced by releasing the flash gas from the flash tank 115. In some embodiments, the flash gas bypass valve 150 may be used to control the temperature and/or superheat of the refrigerant from the load 130. For example, during a post start, the flash gas bypass valve 150 may be opened to allow flash gas to mix with refrigerant from the load 130 and/or the cryogenic compressor 140. As a result, the refrigerant can be cooled before reaching the medium temperature compressor 155.

The medium temperature compressor 155 compresses the refrigerant from the load 130. The middle temperature compressor 155 may be designed to compress a refrigerant for cooling a space to a higher temperature than a refrigerant for which the low temperature compressor 140 is designed to compress. During start-up, the medium-temperature compressor 155 compresses the refrigerant from the load 130 after the refrigerant has passed through the heat exchanger 110. As previously described, the refrigerant may absorb heat from the refrigerant from the high side heat exchanger 105 as it passes through the heat exchanger 110 during startup. In this way, the refrigerant may contain sufficient superheat to be compressed by the medium temperature compressor 155. During post start, the medium temperature compressor 155 compresses the refrigerant from the load 130 after the refrigerant has been compressed by the low temperature compressor 140. As a result, the medium temperature compressor 155 compresses the refrigerant that has been compressed by the low temperature compressor 140 during the post start.

The oil separator 160 separates oil from the refrigerant from the medium temperature compressor 155. By separating oil from the refrigerant, the oil separator 160 prevents oil from flowing to other components of the system 100. If the oil flows to these other components, the oil may damage and/or clog these other components. Thus, the oil separator 160 increases the efficiency and longevity of the system 100. Certain embodiments of the system 100 do not include an oil separator 160.

In operation, the system 100 cools the space near the load 130 in two stages. During the startup phase, system 100 opens heat exchanger 110, opens expansion valve 120, closes expansion valve 125, controls valve 135 to direct refrigerant away from low temperature compressor 140, closes low temperature compressor 140, and opens medium temperature compressor 155. The high side heat exchanger 105 removes heat from the refrigerant and directs the refrigerant to the heat exchanger 110. The heat exchanger 110 transfers heat away from the refrigerant from the high side heat exchanger 105 and directs the refrigerant to the flash tank 115. The flash tank 115 stores refrigerant and directs the refrigerant to expansion valves 120 and 125. Because expansion valve 125 is closed and expansion valve 120 is open, refrigerant is routed through expansion valve 120 to load 130. The load 130 uses a refrigerant to cool the load 130. Refrigerant from the load 130 is delivered through valve 135 to the heat exchanger 110, thereby bypassing the cryogenic compressor 140. The heat exchanger 110 transfers heat from the refrigerant from the high-side heat exchanger 105 to the refrigerant from the load 130. The heat exchanger 110 then directs the refrigerant from the load 130 to the medium temperature compressor 155. The medium temperature compressor 155 compresses the refrigerant from the load 130 and directs the refrigerant to the oil separator 160. The oil separator 160 separates oil from the refrigerant, and guides the refrigerant to the high-side heat exchanger 105.

When the load 130 cools the load 130 using the refrigerant, the temperature of the load 130 decreases. Sensor 133 monitors the temperature of load 130. When the temperature of the load 130 drops below a certain temperature threshold (e.g., 10 degrees fahrenheit), the system 100 transitions to a post-startup phase. During the transition, the system 100 closes the heat exchanger 110, closes the expansion valve 120, opens the expansion valve 125, adjusts the valve 135 to direct refrigerant to the low temperature compressor 140, turns the low temperature compressor 140 on, and turns the desuperheater 145 on.

During the post-startup phase, the high side heat exchanger 105 removes heat from the refrigerant and directs the refrigerant to the heat exchanger 110. The heat exchanger 110 directs refrigerant from the high side heat exchanger 105 to a flash tank 115. The flash tank 115 stores refrigerant and directs the refrigerant to expansion valves 120 and 125. Because expansion valve 120 is closed and expansion valve 125 is open, refrigerant flows through expansion valve 125 to load 130. The load 130 uses a refrigerant to further cool the load 130. Refrigerant from load 130 flows to valve 135. Valve 135 directs the refrigerant to a cryogenic compressor 140. The low temperature compressor 140 compresses refrigerant from the load 130. The desuperheater 145 removes heat from the cryogenic compressor 140. The refrigerant then flows to heat exchanger 110. Because the heat exchanger 110 is closed, no heat is transferred from the refrigerant from the high-side heat exchanger 105 to the refrigerant from the load 130. Refrigerant from the load 130 is delivered through the heat exchanger 110 to the medium temperature compressor 155. The intermediate temperature compressor 155 compresses the refrigerant from the low temperature compressor 140 and the load 130. The oil separator 160 separates oil from the refrigerant from the medium temperature compressor 155 and guides the refrigerant to the high side heat exchanger 105.

In this manner, during the startup phase, the system 100 protects the cryogenic compressor 140 from shutdown when the load 130 is at its hottest state. After the load 130 has been sufficiently cooled, the system 100 turns on the cryogenic compressor 140 and allows the cryogenic compressor 140 to compress the refrigerant from the load 130. The present disclosure contemplates shutting down or turning on any suitable component of system 100 during start-up and/or post-start-up. Although certain components are described as being turned off or on during certain phases, the present disclosure contemplates that these components may also be turned on or off during these phases.

FIG. 2 illustrates an example cooling system 200. As seen in fig. 2, system 200 includes high side heat exchanger 105, heat exchanger 110, flash tank 115, expansion valve 120, expansion valve 125, load 130, sensor 133, low temperature compressor 140, desuperheater 145, flash gas bypass valve 150, medium temperature compressor 155, oil separator 160, and valve 205. In certain embodiments, the system 200 protects the cryogenic compressor 140 from shutdown during start-up by directing refrigerant from the load 130 away from the cryogenic compressor 140 to the intermediate temperature compressor 155. In this manner, the cryogenic compressor 140 does not assume the task of compressing refrigerant that the cryogenic compressor 140 is not designed to compress.

In general, several components of system 200 operate similarly to their operation in system 100. For example, the high side heat exchanger 105 removes heat from the refrigerant. The heat exchanger 110 transfers heat between the refrigerant flowing through the heat exchanger 110 during startup. The flash tank 115 stores refrigerant. The expansion valves 120 and 125 cool the refrigerant flowing through the expansion valves 120 and 125. The load 130 uses a refrigerant to cool a space near the load 130. Sensor 133 monitors the temperature of load 130. The cryogenic compressor 140 compresses refrigerant from the load 130 during the post-start phase. The desuperheater 145 removes heat from the refrigerant from the low temperature compressor 140. The flash gas bypass valve 150 controls the flow of flash gas from the flash tank 115 to the medium temperature compressor 155. The medium temperature compressor 155 compresses refrigerant from the load 130 during start-up and compresses refrigerant from the low temperature compressor 140 during post-start-up. The oil separator 160 separates oil from the refrigerant from the medium temperature compressor 155.

One important difference between system 200 and system 100 is valve 205. In the system 100, a three-way valve 135 controls the flow of refrigerant from the load 130. In system 200, valve 205 also controls the flow of refrigerant from load 130. However, the valve 205 may be a two-way valve, such as a solenoid valve. During startup, valve 205 is opened to allow refrigerant from load 130 to flow through valve 205. Because the cryogenic compressor 140 is off during start-up, refrigerant does not flow from the load 130 to the cryogenic compressor 140. As a result, during start-up, refrigerant from load 130 flows through valve 205 to medium temperature compressor 155, thereby bypassing low temperature compressor 140. During post start-up, valve 205 is closed to prevent refrigerant from load 130 from flowing through valve 205. Because the cryogenic compressor 140 is on during the post start, refrigerant from the load 130 flows through the cryogenic compressor 140. In this way, a two-way valve such as a solenoid valve may be used instead of the three-way valve.

During start-up, system 200 turns heat exchanger 110 on, expansion valve 120 on, expansion valve 125 off, low temperature compressor 140 off, valve 205 on, and medium temperature compressor 155 on. The high side heat exchanger 105 removes heat from the refrigerant and directs the refrigerant to the heat exchanger 110. The heat exchanger 110 transfers heat away from the refrigerant from the high side heat exchanger 105 and directs the refrigerant to the flash tank 115. The flash tank 115 stores refrigerant and directs the refrigerant to expansion valves 120 and 125. Because expansion valve 120 is open and expansion valve 125 is closed, refrigerant flows through expansion valve 120 to load 130. The load 130 uses a refrigerant to cool a space near the load 130. Sensor 133 monitors the temperature of load 130. Refrigerant from load 130 flows through valve 205 to heat exchanger 110, thereby bypassing cryogenic compressor 140. The heat exchanger 110 transfers heat to the refrigerant from the load 130 and directs the refrigerant to the medium temperature compressor 155. The intermediate temperature compressor 155 compresses the refrigerant from the heat exchanger 110 and the load 130. The oil separator 160 separates oil from the refrigerant from the medium temperature compressor 155 and guides the refrigerant to the high side heat exchanger 105.

Sensor 133 monitors the temperature of load 130. When the temperature of the load 130 drops below a set temperature threshold (e.g., 10 degrees fahrenheit), the system 200 transitions to a post-startup phase. During post start-up, system 200 closes heat exchanger 110, closes expansion valve 120, opens expansion valve 125, closes valve 205, turns on cryogenic compressor 140, and turns on desuperheater 145.

During post start, the high side heat exchanger 105 removes heat from the refrigerant and directs the refrigerant to the heat exchanger 110. The heat exchanger 110 directs refrigerant to a flash tank 115. The flash tank 115 stores refrigerant and directs the refrigerant to expansion valves 120 and 125. Because expansion valve 120 is closed and expansion valve 125 is open, refrigerant flows through expansion valve 125 to load 130. The load 130 uses a refrigerant to further cool the load 130. Because valve 205 is closed, refrigerant from load 130 flows to cryogenic compressor 140. The low temperature compressor 140 compresses refrigerant from the load 130. The desuperheater 145 removes heat from the refrigerant from the low temperature compressor 140. The intermediate temperature compressor 155 compresses refrigerant from the desuperheater 145 and/or the low temperature compressor 140. The oil separator 160 separates oil from the refrigerant from the medium temperature compressor 155 and guides the refrigerant to the high side heat exchanger 105. In this manner, system 200 protects cryogenic compressor 140 from shutdown during startup by diverting refrigerant away from cryogenic compressor 140 during startup.

The present disclosure contemplates shutting down or turning on any suitable component of system 200 during start-up and/or post-start-up. Although certain components are described as being turned off or on during certain phases, the present disclosure contemplates that these components may also be turned on or off during these phases.

FIG. 3 is a flow chart illustrating a method 300 of operating an example cooling system. In certain embodiments, various components of the systems 100 and 200 perform the steps of the method 300. As a result, the compressor is protected from shutdown during startup of the cooling system.

In step 305, the high side heat exchanger removes heat from the refrigerant. In step 310, the flash tank stores refrigerant. In step 315, it is determined whether the system is in a startup mode. If the temperature of the load is above a set temperature threshold, such as 10 degrees Fahrenheit, the system may be in a startup mode. The present disclosure contemplates the cooling system being in a start-up mode at any suitable temperature.

If the system is in a start-up mode, a first expansion valve directs refrigerant from the flash tank to a load in step 320. In step 325, the load cools the space using the refrigerant. In step 330, the heat exchanger transfers heat from the refrigerant from the high-side heat exchanger to the refrigerant from the load. In step 335, the first compressor compresses a refrigerant.

If the system is not in start-up mode, a second expansion valve directs refrigerant from the flash tank to a load in step 340. In step 345, the load cools the space using the refrigerant. In step 350, the second compressor compresses refrigerant from the load. In step 355, the second compressor compresses the refrigerant from the first compressor.

Modifications, additions, or omissions may be made to method 300 depicted in fig. 3. The method 300 may include more, fewer, or other steps. For example, the steps may be performed in parallel or in any suitable order. Although discussed as systems 100 and/or 200 (or components thereof) performing these steps, any suitable component of systems 100 and/or 200 may perform one or more steps of the method.

Modifications, additions, or omissions may be made to the systems and devices described herein without departing from the scope of the disclosure. The components of the system and apparatus may be integrated or separated. Moreover, the operations of the systems and devices may be performed by more, fewer, or other components. Additionally, the operations of the systems and devices may be performed using any suitable logic comprising software, hardware, and/or other logic. As used herein, "each" refers to each member of a set or each member of a subset of a set.

The present disclosure may refer to refrigerant from a particular component of the system (e.g., refrigerant from a medium temperature compressor, refrigerant from a low temperature compressor, refrigerant from a flash tank, etc.). When such terms are used, the disclosure does not limit the described refrigerant to coming directly from a particular component. The present disclosure contemplates that the refrigerant is from a particular component (e.g., a high-side heat exchanger, a medium-temperature compressor, etc.), even though other intervening components may exist between the particular component and the destination of the refrigerant. For example, the heat exchanger receives refrigerant from a medium temperature compressor, even though there may be an oil separator between the heat exchanger and the medium temperature compressor.

Although the present disclosure includes several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present disclosure encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.