BACKGROUND

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

With enforcement from governmental environmental agencies, a large part of the world is now being forced to transition to zero global warming refrigeration systems like trans-critical carbon dioxide refrigeration. Trans-critical carbon dioxide systems work well in relatively cooler climates like most of the Europe and North America but face a drawback in hot climates as their coefficient of performance (a measure of efficiency) degrades as the ambient temperature of the surroundings get larger resulting in higher electricity costs per unit cooling performed. This is due to the much larger pressure that trans-critical carbon dioxide system needs to operate at (approximately 10,342 kPa (1500 psi) or greater) compared to HFC/CFC based systems (approximately 1,379-2068.4 kPa (200-300 psi)). To bring the refrigerant above the critical pressure a very high differential pressure compressor is utilized. The large pressure ratio across the compressor consumes more electrical energy. This problem is exaggerated in hotter climates as the refrigerant temperature at the inlet of the chiller needs to be increased to a sufficiently high temperature to enable rejection of heat to the surrounding hotter environment. This is done by increasing pressure ratio across the compressor even higher, thus creating an even larger electricity demand by the compressor and in turn increasing the electricity costs per unit cooling performed. Increased efficiency of refrigeration systems (e.g., trans-critical carbon dioxide refrigeration systems) may reduce the cost of operating the refrigeration equipment as well as increase its availability, while helping reduce global warming.

BRIEF DESCRIPTION

Certain embodiments commensurate in scope with the disclosed subject matter are summarized below. These embodiments are not intended to limit the scope of the disclosure, but rather these embodiments are intended only to provide a brief summary of certain disclosed embodiments. Indeed, the present disclosure may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

In an embodiment, a refrigeration system is provided. The refrigeration system includes a high pressure branch for circulating a refrigerant at a high pressure through it. The refrigeration system also includes a gas cooler or a condenser disposed along the high pressure branch, wherein the high pressure branch is configured to reject heat to the surroundings from the refrigerant at high pressure via the gas cooler or the condenser, and the refrigerant at high pressure is in a supercritical state or subcritical state. The refrigeration system further includes a low pressure branch for circulating the refrigerant at a low pressure through it. The refrigeration system yet further includes an evaporator disposed along the low pressure branch, wherein the low pressure branch is configured to absorb heat from the surroundings into the refrigerant at low pressure via the evaporator, and the refrigerant at low pressure is in a liquid state, a vapor state, or a two-phase mixture of liquid and vapor. The refrigeration system still further includes a compressor or pump configured to increase a pressure of the refrigerant from low pressure to high pressure. The refrigeration system even further includes a rotary pressure exchanger fluidly coupled to the low pressure branch and the high pressure branch, wherein the rotary pressure exchanger is configured to receive the refrigerant at high pressure from the high pressure branch, to receive the refrigerant at low pressure from the low pressure branch, and to exchange pressure between the refrigerant at high pressure and the refrigerant at low pressure, and wherein a first exiting stream from the rotary pressure exchanger includes the refrigerant at high pressure in the supercritical state or the subcritical state and a second exiting stream from the rotary pressure exchanger includes the refrigerant at low pressure in the liquid state or the two-phase mixture of liquid and vapor.

In an embodiment, a refrigeration system is provided. The refrigeration system includes a high pressure branch for circulating a refrigerant at a high pressure through it. The refrigeration system includes a gas cooler or a condenser disposed along the high pressure branch, wherein the high pressure branch is configured to reject heat to the surroundings from the refrigerant at high pressure via the gas cooler or the condenser, and the refrigerant at high pressure is in a supercritical state or subcritical state. The refrigeration system also includes a low pressure branch for circulating the refrigerant at a low pressure through it. The refrigeration system further includes a first evaporator disposed along the low pressure branch, wherein the first evaporator is configured to operate at a first temperature, wherein the low pressure branch is configured to absorb heat from the surroundings into the refrigerant at low pressure via the evaporator, and the refrigerant at low pressure is in a liquid state, a vapor state, or a two-phase mixture of liquid and vapor. The refrigeration system further includes a first intermediate pressure branch for circulating the refrigerant through it at a first intermediate pressure. The refrigeration system still further includes a second evaporator disposed along the first intermediate pressure branch, wherein the second evaporator is configured to operate at a second temperature greater than the first temperature. The refrigeration system yet further includes a second intermediate pressure branch for circulating the refrigerant through it at a second intermediate pressure, wherein first intermediate pressure of the refrigerant in the first intermediate pressure branch is between respective pressures of the refrigerant in the low pressure branch and the second intermediate pressure branch, the first intermediate pressure of the refrigerant in the first intermediate pressure branch is equal to a saturation pressure at the second evaporator, and the second intermediate pressure of refrigerant in the second intermediate pressure branch is between respective pressures of the refrigerant in the high pressure branch and the first intermediate pressure branch. The refrigeration system still further includes a flash tank configured to operate at the second intermediate pressure and to separate the refrigerant in the two-phase mixture of liquid and vapor into pure liquid and pure vapor; and a rotary pressure exchanger fluidly coupled to the second intermediate pressure branch and the high pressure branch, wherein the rotary pressure exchanger is configured to receive the refrigerant at high pressure from the high pressure branch, to receive the refrigerant at the second intermediate pressure in the vapor state, the liquid state, or the two-phase mixture of liquid and vapor from the second intermediate pressure branch, and to exchange pressure between the refrigerant at high pressure and the refrigerant at the second intermediate pressure, and wherein a first exiting stream from the rotary pressure exchanger includes the refrigerant at high pressure in the supercritical state or the subcritical state and a second exiting stream from the rotary pressure exchanger includes the refrigerant at the second intermediate pressure in the liquid state or the two-phase mixture of liquid and vapor.

In an embodiment, a refrigeration system is provided. The refrigeration system includes a high pressure branch for circulating a refrigerant at a high pressure through it. The refrigeration also includes a gas cooler or a condenser disposed along the high pressure branch, wherein the high pressure branch is configured to reject heat to the surroundings from the refrigerant at high pressure via the gas cooler or the condenser, and the refrigerant at high pressure is in a supercritical state or subcritical state. The refrigeration system further includes a second low pressure branch for circulating the refrigerant at a low pressure through it. The refrigeration system still further includes a first evaporator disposed along the low pressure branch, wherein the first evaporator is configured to operate at a first temperature, wherein the low pressure branch is configured to absorb heat from the surroundings into the refrigerant at low pressure via the evaporator, and the refrigerant at low pressure is in a liquid state, a vapor state, or a two-phase mixture of liquid and vapor. The refrigeration system even further includes an intermediate pressure branch for circulating the refrigerant through it at an intermediate pressure. The refrigeration system yet further includes a second evaporator disposed along the intermediate pressure branch, wherein the second evaporator is configured to operate at a second temperature greater than the first temperature. The intermediate pressure of the refrigerant in the intermediate pressure branch is between respective pressures of the refrigerant in the high pressure branch and the low pressure branch, the intermediate pressure of the refrigerant in the intermediate pressure branch is equal to a saturation pressure at the second evaporator. The refrigeration system still further includes a flash tank configured to operate at the intermediate pressure and to separate the refrigerant in the two-phase mixture of liquid and vapor into pure liquid and pure vapor. The refrigeration system yet further includes a rotary pressure exchanger fluidly coupled to the intermediate pressure branch and the high pressure branch, wherein the rotary pressure exchanger is configured to receive the refrigerant at high pressure from the high pressure branch, to receive the refrigerant at the intermediate pressure in the vapor state, the liquid state, or the two-phase mixture of liquid and vapor from the intermediate pressure branch, and to exchange pressure between the refrigerant at high pressure and the refrigerant at the intermediate pressure, and wherein a first exiting stream from the rotary pressure exchanger includes the refrigerant at high pressure in the supercritical state or the subcritical state and a second exiting stream from the rotary pressure exchanger includes the refrigerant at the intermediate pressure in the liquid state or the two-phase mixture of liquid and vapor.

