TECHNICAL FIELD

This disclosure relates generally to a cooling system (e.g., a refrigeration system and/or an air conditioning system).

BACKGROUND

Cooling systems may cycle a refrigerant to cool various spaces. For example, a system may cycle refrigerant to cool spaces near or around low side heat exchangers.

SUMMARY

Cooling systems (e.g., refrigeration systems and/or air conditioning systems) may cycle a refrigerant to cool various spaces. For example, a system may cycle refrigerant to cool spaces near or around low side heat exchangers. One refrigerant that has seen increasing use in cooling systems is carbon dioxide, due to its environmentally friendly properties relative to other conventional refrigerants. One drawback of carbon dioxide refrigerant, however, is that carbon dioxide refrigerant is difficult to use and manage in extreme temperatures. For example, cooling systems that use carbon dioxide refrigerant tend to operate more inefficiently in high ambient heat than cooling systems that use other refrigerants. It may be more difficult to regulate the pressure of the carbon dioxide refrigerant and to remove heat from the carbon dioxide refrigerant in high ambient heat.

This disclosure contemplates a cooling system that implements various processes to improve efficiency in high ambient temperatures. First, the system can flood one or more low side heat exchangers in the system. Second, the system can direct a portion of vapor refrigerant from a low side heat exchanger to a flash tank rather than to a compressor. Third, the system can transfer heat from refrigerant at a compressor suction to refrigerant at the discharge of a high side heat exchanger. By using one or more of these processes, the system improves the efficiency of operation during high ambient temperatures in certain embodiments. Certain embodiments are described below.

According to an embodiment, an apparatus includes a high side heat exchanger, a first ejector, a flash tank, a first low side heat exchanger, a first separator, a second low side heat exchanger, a second separator, an accumulator, a first valve, a second valve, and a compressor. The high side heat exchanger removes heat from a refrigerant. The first ejector receives refrigerant from the high side heat exchanger. The flash tank stores refrigerant. The first ejector directs refrigerant from the high side heat exchanger to the flash tank. The first low side heat exchanger uses refrigerant from the flash tank to cool a first space. The first separator receives refrigerant from the first low side heat exchanger. The refrigerant from the first low side heat exchanger includes a first liquid portion and a first vapor portion. The second low side heat exchanger uses refrigerant from the flash tank to cool a second space. The second separator receives refrigerant from the second low side heat exchanger. The refrigerant from the second low side heat exchanger includes a second liquid portion and a second vapor portion. The accumulator receives the first liquid portion and the second liquid portion. The accumulator separates refrigerant within the accumulator into a third liquid portion and a third vapor portion. The first valve can open to direct the first vapor portion to the first ejector. The first ejector directs the first vapor portion to the flash tank. The first valve can close to direct the first vapor portion to the accumulator. The second valve can open to direct the second vapor portion to the first ejector. The first ejector directs the second vapor portion to the flash tank. The second valve can close to direct the second vapor portion to the accumulator. The compressor compresses the third vapor portion from the accumulator.

According to another embodiment, a method includes removing, by a high side heat exchanger, heat from a refrigerant, receiving, by a first ejector, refrigerant from the high side heat exchanger, and storing, by a flash tank, refrigerant. The method also includes directing, by the first ejector, refrigerant from the high side heat exchanger to the flash tank, using, by a first low side heat exchanger, refrigerant from the flash tank to cool a first space, and receiving, by a first separator, refrigerant from the first low side heat exchanger. The refrigerant from the first low side heat exchanger includes a first liquid portion and a first vapor portion. The method further includes using, by a second low side heat exchanger, refrigerant from the flash tank to cool a second space, and receiving, by a second separator, refrigerant from the second low side heat exchanger. The refrigerant from the second low side heat exchanger includes a second liquid portion and a second vapor portion. The method also includes receiving, by an accumulator, the first liquid portion and the second liquid portion and during a first mode of operation, opening a first valve to direct the first vapor portion to the first ejector, directing, by the first ejector, the first vapor portion to the flash tank, and closing a second valve to direct the second vapor portion to the accumulator. The method further includes, during a second mode of operation, closing the first valve further to direct the first vapor portion to the accumulator, opening the second valve to direct the second vapor portion to the first ejector, and directing, by the first ejector, the second vapor portion to the flash tank. The method further includes separating, by the accumulator, refrigerant within the accumulator into a third liquid portion and a third vapor portion and compressing, by a compressor, the third vapor portion from the accumulator.

According to another embodiment, a system includes a high side heat exchanger, a first ejector, a flash tank, a first low side heat exchanger, a first separator, a second low side heat exchanger, a second separator, an accumulator, a first valve, a second valve, and a compressor. The high side heat exchanger removes heat from a refrigerant. The first ejector receives refrigerant from the high side heat exchanger. The flash tank stores refrigerant. The first ejector directs refrigerant from the high side heat exchanger to the flash tank. The first low side heat exchanger uses refrigerant from the flash tank to cool a first space. The first separator receives refrigerant from the first low side heat exchanger. The refrigerant from the first low side heat exchanger includes a first liquid portion and a first vapor portion. The second low side heat exchanger uses refrigerant from the flash tank to cool a second space. The second separator receives refrigerant from the second low side heat exchanger. The refrigerant from the second low side heat exchanger includes a second liquid portion and a second vapor portion. The accumulator receives the first liquid portion and the second liquid portion and separates refrigerant within the accumulator into a third liquid portion and a third vapor portion. During a first mode of operation, the first valve opens to direct the first vapor portion to the first ejector, the first ejector further directs the first vapor portion to the flash tank, and the second valve closes to direct the second vapor portion to the accumulator. During a second mode of operation, the first valve further closes to direct the first vapor portion to the accumulator, the second valve further opens to direct the second vapor portion to the first ejector, and the first ejector further directs the second vapor portion to the flash tank. The compressor compresses the third vapor portion from the accumulator.

Certain embodiments provide one or more technical advantages. For example, an embodiment improves the efficiency of a carbon dioxide cooling system during high ambient temperatures. 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.

