Cooling system with improved compressor stability

A system includes a high side heat exchanger, a flash tank, a first load, a second load, a first compressor, and a heat exchanger. The flash tank is configured to store the refrigerant from the high side heat exchanger. The first load is configured to use the refrigerant from the flash tank to remove heat from a first space proximate to the first load. The second load is configured to use the refrigerant from the flash tank to remove heat from a second space proximate to the second load. The first compressor is configured to compress the refrigerant from the first load. The heat exchanger is configured to transfer heat from the refrigerant from the first compressor and the second load to the refrigerant from the high side heat exchanger, and direct the refrigerant from the first compressor and the second load to a second compressor.

TECHNICAL FIELD

This disclosure relates generally to a cooling system.

BACKGROUND

Cooling systems cycle a refrigerant to cool various spaces. For example, a refrigeration system may cycle refrigerant to cool spaces near or around a refrigeration unit.

SUMMARY OF THE DISCLOSURE

According to one embodiment, a system includes a high side heat exchanger, a flash tank, a first load, a second load, a first compressor, and a heat exchanger. The high side heat exchanger is configured to remove heat from a refrigerant. The flash tank is configured to store the refrigerant from the high side heat exchanger. The first load is configured to use the refrigerant from the flash tank to remove heat from a first space proximate to the first load. The second load is configured to use the refrigerant from the flash tank to remove heat from a second space proximate to the second load. The first compressor is configured to compress the refrigerant from the first load. The heat exchanger is configured to transfer heat from the refrigerant from the first compressor and the second load to the refrigerant from the high side heat exchanger, and direct the refrigerant from the first compressor and the second load to a second compressor.

According to another embodiment, a method includes removing heat from a refrigerant using a high side heat exchanger. The method also includes storing the refrigerant from the high side heat exchanger in a flash tank. The method further includes removing heat from a first space using a first load including the refrigerant from the flash tank. The method also includes removing heat from a second space using a second load including refrigerant from the flash tank. The method further includes compressing the refrigerant from the first load using a first compressor. The method also includes transferring heat from the refrigerant from the first compressor and the second load to the refrigerant from the high side heat exchanger using a heat exchanger. The method further includes directing the refrigerant from the first compressor and the second load to the second compressor using the heat exchanger.

According to yet another embodiment, a system includes a first load, a second load, a first compressor, and a heat exchanger. The first load is configured to use a refrigerant from a flash tank to remove heat from a first space proximate to the first load. The second load is configured to use the refrigerant from the flash tank to remove heat from a second space proximate to the second load. The first compressor is configured to compress the refrigerant from the first load. The heat exchanger is configured to transfer heat from the refrigerant from the first compressor and the second load to the refrigerant from a high side heat exchanger. The heat exchanger is also configured to direct the refrigerant from the first compressor and the second load to a second compressor.

Certain embodiments may provide one or more technical advantages. For example, an embodiment maintains a stable temperature and pressure of refrigerant entering compressors of the cooling system. As a result, risk of damage to the compressors due to exposure to refrigerant that is too hot or too cold is minimized. As another example, an embodiment maintains a stable temperature of refrigerant entering compressors of the cooling system without the need for specialized hardware in the flash tank or injecting additional refrigerant into the system. Certain 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.

DETAILED DESCRIPTION

Cooling systems may cycle a refrigerant to cool various spaces. For example, a refrigeration system may cycle refrigerant to cool spaces near or around refrigeration loads. In certain installations, such as at a grocery store for example, a refrigeration system may include different types of loads. For example, a grocery store may use medium temperature loads and low temperature loads. The medium temperature loads may be used for produce and the low temperature loads may be used for frozen foods. The compressors for these loads may be chained together. For example, the discharge of the low temperature compressor for the low temperature load may be fed into the medium temperature compressor that also compresses the refrigerant from the medium temperature loads. The discharge of the medium temperature compressor is then fed to a high side heat exchanger that removes heat from the compressed refrigerant.

In cooling systems, it is important that refrigerant entering the compressors maintains a temperature within a certain range. If the refrigerant in the compressors is too warm or too cold, it risks damaging the compressors. As a result, there is a need for refrigerant entering compressors to maintain a stable temperature and pressure. As an example, conventional cooling systems may inject liquid refrigerant into the suction line to mix with the refrigerant traveling to the compressor to maintain a stable temperature and pressure of the refrigerant traveling to the compressor. As another example, conventional cooling systems may use hardware such as a suction accumulator inside of a flash tank through which refrigerant traveling to compressors may travel to stabilize its temperature and pressure.

This disclosure contemplates using a heat exchanger to maintain a stable temperature and pressure of refrigerant fed into compressors of cooling systems. The heat exchanger may use the stable conditions of the refrigerant traveling to the flash tank as a passive control on the refrigerant traveling to the compressor. In certain embodiments, when refrigerant is traveling from a high pressure expansion valve to the flash tank, it has a relatively stable temperature and pressure. By passing that relatively stable refrigerant through the heat exchanger at the same time that refrigerant traveling to the compressor passes through the heat exchanger, the temperature and pressure of the refrigerant traveling to the compressor may be stabilized. Stabilization of the temperature and pressure of refrigerant traveling to the compressor may be achieved without the need to install or maintain specialized hardware such as an accumulator, or expend energy and resources to implement other potential controls.

The system will be described in more detail usingFIGS. 1 through 3.FIG. 1will describe an existing refrigeration system.FIGS. 2 and 3will describe the refrigeration system with a heat exchanger.

FIG. 1illustrates an example cooling system100. As shown inFIG. 1, system100includes a high side heat exchanger105, a flash tank110, a medium temperature load115, a low temperature load120, a medium temperature compressor130, and a low temperature compressor135.

High side heat exchanger105may remove heat from a refrigerant. When heat is removed from the refrigerant, the refrigerant is cooled. This disclosure contemplates high side heat exchanger105being operated as a condenser, a fluid cooler, and/or a gas cooler. When operating as a condenser, high side heat exchanger105cools the refrigerant such that the state of the refrigerant changes from a gas to a liquid. When operating as a fluid cooler, high side heat exchanger105cools liquid refrigerant and the refrigerant remains a liquid. When operating as a gas cooler, high side heat exchanger105cools gaseous refrigerant and the refrigerant remains a gas. In certain configurations, high side heat exchanger105is positioned such that heat removed from the refrigerant may be discharged into the air. For example, high side heat exchanger105may be positioned on a rooftop so that heat removed from the refrigerant may be discharged into the air. As another example, high side heat exchanger105may be positioned external to a building and/or on the side of a building.

Flash tank110may store refrigerant received from high side heat exchanger105. This disclosure contemplates flash tank110storing refrigerant in any state such as, for example, a liquid state and/or a gaseous state. Refrigerant leaving flash tank110is fed to low temperature load120and medium temperature load115. In some embodiments, a flash gas and/or a gaseous refrigerant is released from flash tank110. By releasing flash gas, the pressure within flash tank110may be reduced.

System100may include a low temperature portion and a medium temperature portion. The low temperature portion may operate at a lower temperature than the medium temperature portion. In some refrigeration systems, the low temperature portion may be a freezer system and the medium temperature system may be a regular refrigeration system. In a grocery store setting, the low temperature portion may include freezers used to hold frozen foods, and the medium temperature portion may include refrigerated shelves used to hold produce. Refrigerant may flow from flash tank110to both the low temperature and medium temperature portions of the refrigeration system. For example, the refrigerant may flow to low temperature load120and medium temperature load115. When the refrigerant reaches low temperature load120or medium temperature load115, the refrigerant removes heat from the air around low temperature load120or medium temperature load115. As a result, the air is cooled. The cooled air may then be circulated such as, for example, by a fan to cool a space such as, for example, a freezer and/or a refrigerated shelf. As refrigerant passes through low temperature load120and medium temperature load115, the refrigerant may change from a liquid state to a gaseous state as it absorbs heat.

Refrigerant may flow from low temperature load120and medium temperature load115to compressors130and135. This disclosure contemplates system100including any number of low temperature compressors135and medium temperature compressors130. The low temperature compressor135and medium temperature compressor130may increase the pressure of the refrigerant. As a result, the heat in the refrigerant may become concentrated and the refrigerant may become a high pressure gas. Low temperature compressor135may compress refrigerant from low temperature load120and send the compressed refrigerant to medium temperature compressor130. Medium temperature compressor130may compress refrigerant from low temperature compressor135and medium temperature load115. Medium temperature compressor130may then send the compressed refrigerant to high side heat exchanger105.

As shown inFIG. 1, the discharge of low temperature compressor135is fed to medium temperature compressor130. Medium temperature compressor130then compresses the refrigerant from medium temperature load115and low temperature compressor135. As additional low temperature loads and/or low temperature compressors are added to system100, the strain on medium temperature compressor130increases. As medium temperature compressor130does more work, the overall efficiency of system100falls. As a result of reduced efficiency, the temperature and pressure of refrigerant traveling, for example, from first compressor224to second compressor230may become less stable. Less stable refrigerant traveling to second compressor230risks damaging second compressor230.

FIG. 2illustrates an example of cooling system200. As illustrated inFIG. 2, system200includes high side heat exchanger105, flash tank110, a first load215, a second load220, a first compressor225, a second compressor230, flash gas valve240, heat exchanger250, bypass valve260, and high pressure expansion valve270. The components of system200may be similar to the components of system100. However, the components of system200may be configured differently than the components of system100to integrate the heat exchanger250. In particular embodiments, system200protects first compressor225and/or second compressor230from damage by maintaining the temperature and pressure of the refrigerant entering those compressors within a certain range through use of heat exchanger250.

In system200, flash tank110may receive the refrigerant from heat exchanger250. In some embodiments, flash tank110may receive the refrigerant from a second chamber252of heat exchanger250. Flash thank110may then direct the refrigerant to first load220and second load215. Refrigerant from first load220may flow to first compressor225. First compressor225may direct the refrigerant to heat exchanger250. Refrigerant from second load215may flow to heat exchanger250. Second compressor230may receive the refrigerant from heat exchanger250and direct the refrigerant to high side heat exchanger105. High side heat exchanger105may direct the refrigerant to heat exchanger250. In some embodiments, high side heat exchanger105may direct the refrigerant to a first chamber251of heat exchanger250.

As illustrated inFIG. 1, flash tank110may store refrigerant received from high side heat exchanger105. This disclosure contemplates flash tank110storing refrigerant in any such state such as, for example, a liquid state and/or a gaseous state. In system200, refrigerant leaving flash tank110is fed to first load220and second load215. In some embodiments, a flash gas and/or a gaseous refrigerant is released from flash tank110. By releasing flash gas, the pressure within flash tank110may be reduced. In some embodiments of system200, flash tank110releases a flash gas to flash gas valve240. Flash gas valve240may direct the flash gas from flash tank110to heat exchanger250. In certain embodiments, flash gas valve240receives flash gas from flash tank110and directs it to second chamber252of heat exchanger250.

Refrigerant may flow from first load220and second load215to compressors of system200. This disclosure contemplates system200including any number of compressors. In some embodiments, refrigerant from first load220flows to first compressor225. In other embodiments, refrigerant from heat exchanger250flows to second compressor230. First compressor225and second compressor230may increase the pressure of the refrigerant. First compressor225may compress refrigerant from first load220. As a result, the heat in the refrigerant may become concentrated and the refrigerant may become a high pressure gas. First compressor225may then send the compressed refrigerant to heat exchanger250. In some embodiments, first compressor225sends the compressed refrigerant to second chamber252of heat exchanger250. Second compressor230may compress refrigerant from heat exchanger250. Second compressor250may then send the compressed refrigerant to high side heat exchanger105.

Heat exchanger250may transfer heat from the refrigerant from first compressor225and second load215to the refrigerant from high side heat exchanger105. Heat exchanger250may further direct the refrigerant from first compressor225and second load215to second compressor230. Heat exchanger250may transfer heat through any means, for example, it may transfer heat passively through proximity of the refrigerant. Heat exchanger250may also increase pressure of the refrigerant to facilitate heat transfer. Heat exchanger250may apply, any pressure suitable to facilitating heat transfer between refrigerant, for example, heat exchanger250may apply a pressure rating of 650 psi.

In some embodiments, heat exchanger includes first chamber251and second chamber252. First chamber251may direct the refrigerant from high side heat exchanger105to flash tank110. Second chamber252may direct the refrigerant from first compressor225and second load215to second compressor230. In such embodiments, heat exchanger250transfers heat from second chamber252to first chamber251. Flash tank110receives the refrigerant from first chamber251of heat exchanger250. First compressor225directs the refrigerant to second chamber252of heat exchanger250. Second compressor230receives the refrigerant from second chamber252of heat exchanger250and directs it to high side heat exchanger105. High side heat exchanger105directs the refrigerant to first chamber251of heat exchanger250.

Refrigerant from first compressor225and second load215may have a range of temperatures, for example the mixture of refrigerant from first compressor225and second load215may have a temperature of approximately 50 to 70° F. In some embodiments, refrigerant from first compressor225and second load215may mix with flash gas from flash tank110before entering heat exchanger250as a mixture. Flash gas from flash tank110may have a range of temperatures, for example, flash gas from flash tank110may have a temperature of 20° F. Refrigerant from high side heat exchanger105may have a lower, more stable temperature, for example, refrigerant from high side heat exchanger may have a temperature of approximately 33° F. By passing refrigerant from first compressor225and second load215through heat exchanger250, heat exchanger250may transfer heat from refrigerant from first compressor225and second load215to refrigerant from high side heat exchanger105.

As a result, certain embodiments of system200maintain the temperature and pressure of refrigerant traveling to the compressors within a certain range. For example, it may be desirable to maintain a temperature of approximately 20 to 50° F. for the refrigerant entering second compressor230. Refrigerant entering second compressor230at approximately 20 to 50° F. may prevent liquid refrigerant droplets from entering second compressor230and causing damage. Refrigerant entering compressor230at temperatures above 50° F. may risk damaging the compressor. By transferring heat from refrigerant from first compressor225and second load215to refrigerant from high side heat exchanger105, heat exchanger250may stabilize the temperature and pressure of refrigerant entering second compressor230. Thus, damage to the compressors from exposure to refrigerant that is too hot or too cold is minimized. In certain embodiments, such results are achieved without the need for installing and maintaining additional, specialized hardware in the flash tank, or consuming additional refrigerant and energy injecting additional liquid refrigerant to mix with the refrigerant traveling to the compressors of the cooling system.

System200may include high pressure expansion valve270. High pressure expansion valve270may receive refrigerant from high side heat exchanger105and direct the refrigerant from high side heat exchanger105to heat exchanger250. In some embodiments, high pressure expansion valve270may direct the refrigerant to bypass valve260. High pressure expansion valve270may separate refrigerant into high pressure refrigerant and low pressure refrigerant.

System200may include bypass valve260. Bypass valve260may receive refrigerant from high side heat exchanger105and direct the refrigerant from high side heat exchanger105to heat exchanger250and/or flash tank110. In some embodiments, bypass valve260receives the refrigerant from high side heat exchanger105and directs the refrigerant to first chamber251of heat exchanger250and/or flash tank110. In some embodiments, bypass valve260receives the refrigerant from high pressure expansion valve270. Bypass valve260may prevent the flow of the refrigerant from high side heat exchanger105to heat exchanger250, and alternatively direct the refrigerant to flash tank110.

System200may include flash gas valve240. Flash gas valve240may receive flash gas from flash tank110and direct the flash gas to heat exchanger250. In certain embodiments, flash gas valve240may receive flash gas from flash tank110and direct the flash gas to second chamber252of heat exchanger250.

In some embodiments of system200, the ratio of a temperature of the refrigerant from second load215and a temperature of the refrigerant from first compressor225is less than one. In yet other embodiments, a ratio of a temperature from the refrigerant from second load215and a temperature of the refrigerant from first compressor225is greater than thirty percent. The ratio of the temperature of the refrigerant from second load215and the temperature of the refrigerant from first compressor225may be less than one, and/or greater than 30%, may stabilize the temperature and pressure of refrigerant entering the compressors using heat exchanger250. Thus, system200may stabilize the temperature and pressure of refrigerant entering compressors225and/or230when a mixture of refrigerants has various temperatures when mixed.

This disclosure contemplates system200including any number of components. For example, system200may include any number of loads215and/or220. As another example, system200may include any number of compressors225and/or230. As a further example, system200may include any number of heat exchangers250, and heat exchanger250may include any number of chambers. As yet another example, system200may include any number of high side heat exchangers105and flash tanks115. This disclosure also contemplates cooling system200using any appropriate refrigerant. For example, cooling system200may use a carbon dioxide refrigerant.

FIG. 3is a flowchart illustrating a method300of operating the example cooling system200ofFIG. 2. Various components of system200perform the steps of method300. In certain embodiments, performing method300may improve the stability of the refrigerant entering compressors of cooling system200.

High side heat exchanger may begin by removing heat from a refrigerant in step305. In step310, flash tank110may store the refrigerant from high side heat exchanger105. In step315, first load220may remove heat from a first space proximate to the first load220. Then in step320, second load215may remove heat from a second space proximate to a second load215. In step325, first compressor225may compress the refrigerant from first load220. In step330, heat exchanger250may transfer heat from the refrigerant from first compressor225and second load215to the refrigerant from the high side heat exchanger105. In step335, heat exchanger250may direct the refrigerant from first compressor225and second load215to second compressor230.

Modifications, additions, or omissions may be made to method300depicted inFIG. 3. Method300may include more, fewer, or other steps. For example, steps may be performed in parallel or in any suitable order. While discussed as various components of cooling system200performing the steps, any suitable component or combination of components of system200may perform one or more steps of the method.