A system for the regeneration of nitrogen energy within a closed loop cryogenic system is described. A liquid nitrogen storage is provided in fluid communication with a first flow line. A pump pumps liquid nitrogen from the liquid nitrogen storage to the first flow line. At least one cryogenic cooling loop is provided in fluid communication with the first flow line. The cryogenic cooling loop has an nitrogen intake and a nitrogen outlet with the nitrogen outlet being positioned downstream of the nitrogen intake. The cryogenic cooling loop has a heat exchanger between the nitrogen intake and the nitrogen outlet. A turbo expander used for re-cooling the nitrogen flowing through the first flow line and the at least one cryogenic cooling loop has an inlet and an outlet. The inlet is provided in fluid communication with the first flow line. The turbo expander is connected to a power source. A second flow line connects the outlet of the turbo expander to the liquid nitrogen storage.

A system for the regeneration of nitrogen energy within a closed loop cryogenic system is described. A liquid nitrogen storage is provided in fluid communication with a first flow line. A pump pumps liquid nitrogen from the liquid nitrogen storage to the first flow line. At least one cryogenic cooling loop is provided in fluid communication with the first flow line. The cryogenic cooling loop has an nitrogen intake and a nitrogen outlet with the nitrogen outlet being positioned downstream of the nitrogen intake. The cryogenic cooling loop has a heat exchanger between the nitrogen intake and the nitrogen outlet. A turbo expander used for re-cooling the nitrogen flowing through the first flow line and the at least one cryogenic cooling loop has an inlet and an outlet. The inlet is provided in fluid communication with the first flow line. The turbo expander is connected to a power source. A second flow line connects the outlet of the turbo expander to the liquid nitrogen storage.

In a cryogenic refrigerator, a displacer has an internal space in which refrigerant gas flows. A cylinder houses the displacer to enable the displacer to perform reciprocating movement and forms an expansion space of the refrigerant gas between the cylinder and a bottom surface of the displacer. The displacer supplies the refrigerant gas to the expansion space during movement inside the cylinder from a bottom dead center to a top dead center. The displacer collects the refrigerant gas from the expansion space during movement inside the cylinder from the top dead center to the bottom dead center. A flow path resistance between the displacer and the expansion space is lower when the displacer is at the bottom dead center than when the displacer is at the top dead center.

In a cryogenic refrigerator, a displacer has an internal space in which refrigerant gas flows. A cylinder houses the displacer to enable the displacer to perform reciprocating movement and forms an expansion space of the refrigerant gas between the cylinder and a bottom surface of the displacer. The displacer supplies the refrigerant gas to the expansion space during movement inside the cylinder from a bottom dead center to a top dead center. The displacer collects the refrigerant gas from the expansion space during movement inside the cylinder from the top dead center to the bottom dead center. A flow path resistance between the displacer and the expansion space is lower when the displacer is at the bottom dead center than when the displacer is at the top dead center.

A compressor temperature control system and method for an aircraft air cycle machine is presented. The system prevents overheating of the compressor using a low limit valve positioned between a turbine outlet and a bleed air source. The low limit valve directs the air to an air cycle machine, or bypasses the machine, in regards at least in part to the air temperature measured in the cabin supply duct.

A compressor temperature control system and method for an aircraft air cycle machine is presented. The system prevents overheating of the compressor using a low limit valve positioned between a turbine outlet and a bleed air source. The low limit valve directs the air to an air cycle machine, or bypasses the machine, in regards at least in part to the air temperature measured in the cabin supply duct.

A sensor assembly is shown for sensing a crossing of the critical point in a system utilising a working fluid in a transcritical cycle passing through the critical point. A first broadband acoustic sensor is located upstream of a component and a second broadband acoustic sensor is located downstream of the component, each of which are arranged to detect high-frequency and low-frequency sounds caused by the crossing of the critical point. A flow regulation device regulates flow of working fluid through the component in response to the output of one or both of the first broadband acoustic sensor and the second broadband acoustic sensor, thereby adjusting the location of the crossing of the critical point.

A sensor assembly is shown for sensing a crossing of the critical point in a system utilising a working fluid in a transcritical cycle passing through the critical point. A first broadband acoustic sensor is located upstream of a component and a second broadband acoustic sensor is located downstream of the component, each of which are arranged to detect high-frequency and low-frequency sounds caused by the crossing of the critical point. A flow regulation device regulates flow of working fluid through the component in response to the output of one or both of the first broadband acoustic sensor and the second broadband acoustic sensor, thereby adjusting the location of the crossing of the critical point.

A cooling system includes a compressor configured to pressurize carbon dioxide to form pressurized carbon dioxide, a mixer configured to generate mixed refrigerant in which the pressurized carbon dioxide and solvent in a liquid state, a depressurization apparatus provided downstream from the mixer and configured to depressurize the mixed refrigerant, a separator configured to separate carbon dioxide in a gas state from the mixed refrigerant, a heat exchanger configured to exchange heat between the mixed refrigerant cooled through depressurization and a fluid to be cooled, and a second heat exchanger configured to cool the carbon dioxide or the mixed refrigerant using vaporized carbon dioxide or the mixed refrigerant.

Thermal management systems include an open circuit refrigeration system featuring a first receiver configured to store a gas, a second receiver configured to store a liquid refrigerant fluid, an evaporator configured to extract heat from a heat load that contacts the evaporator, and an exhaust line, where the first receiver, the second receiver, the evaporator, and the exhaust line are connected to provide a refrigerant fluid flow path.