Abstract: A centrifugal compressor includes a casing, a first impeller, a motor, a cooling medium delivery structure, a shaft, and a first bearing. The casing has a first inlet portion and a first outlet portion. The first impeller is attached to the shaft and disposed between the first inlet portion and the first outlet portion. A first axial gap exists between the first impeller and the casing. The shaft is rotatably supported and axially moveable with respect to the casing by the first bearing. The motor is arranged inside the casing to rotate the shaft. The cooling medium delivery structure is configured to vary a supply of a cooling medium to the casing. An impeller clearance control apparatus for a centrifugal compressor includes a sensor and a controller. The controller controls a supply of a cooling medium to the casing based on a value detected by the sensor.

Abstract: A centrifugal compressor includes a casing, an impeller, a motor, a diffuser, a magnetic bearing, and a magnetic bearing backup system including at least one dynamic gas bearing and at least one hydrostatic gas bearing. The impeller is attached to a shaft rotatable about a rotation axis. The motor is configured and arranged to rotate the shaft in order to rotate the impeller. The magnetic bearing rotatably supports the shaft. The magnetic bearing backup system is configured and arranged to support the shaft when the magnetic bearing stops operating. The at least one dynamic gas bearing and the at least one hydrostatic gas bearing of the magnetic bearing backup system are disposed radially inwardly relative to the magnetic bearing.

Abstract: A refrigerating apparatus includes a centrifugal compressor, suction and discharge capacity control mechanisms that control capacity of the compressor by changing opening degrees of the suction and discharge capacity control mechanisms, and a controller that compares a compressor-specific surge curve with an isentropic head to perform rotational speed control of the compressor, rotational speed adjustment control of the compressor in order to avoid surge, and emergency shutdown control of the compressor upon detection of surge. The compressor-specific surge curve is stored in the controller in advance, and is defined by an actual rotational speed of the compressor and opening degrees of the suction and discharge capacity control mechanisms. The isentropic head is calculated based on a suction pressure, a discharge pressure, and a suction temperature during operation.

Abstract: A non-condensable gas purge system is configured to be used in a chiller system that uses a low pressure refrigerant in a loop refrigeration circuit. The non-condensable gas purge system includes a purge tank and a purge heat exchanger coil arranged inside the purge tank. The purge tank has a tank inlet for receiving the low pressure refrigerant from a condenser of the refrigeration circuit, a tank outlet for returning the low pressure refrigerant to an evaporator of the refrigeration circuit, and a purge outlet for purging non-condensable gas from the purge tank to the ambient atmosphere. The purge heat exchanger coil is fluidly connected to the loop refrigeration circuit such that the low pressure refrigerant contained in the loop of the chiller system can pass through the purge heat exchanger coil. Refrigerant in the purge tank is condensed by the heat exchanger coil while non-condensable gases remain gaseous.

Abstract: A centrifugal compressor includes a casing, a first compression mechanism and a second compression mechanism. The casing has a first inlet portion, a first outlet portion, a second inlet portion and a second outlet portion. The first compression mechanism includes a first inlet guide vane disposed in the first inlet portion, a first impeller disposed downstream of the first inlet guide vane, a first diffuser disposed in the first outlet portion downstream from the first impeller, and a first motor. The second compression mechanism includes a second inlet guide vane disposed in the second inlet portion, a second impeller disposed downstream of the second inlet guide vane, a second diffuser disposed in the second outlet portion downstream from the second impeller, and a second motor. The first and second motors are arranged to rotate first and second shafts in order to rotate the first and second impellers.

Abstract: A centrifugal compressor includes a casing, a first impeller, a motor, a cooling medium delivery structure, a shaft, and a first bearing. The casing has a first inlet portion and a first outlet portion. The first impeller is attached to the shaft and disposed between the first inlet portion and the first outlet portion. A first axial gap exists between the first impeller and the casing. The shaft is rotatably supported and axially moveable with respect to the casing by the first bearing. The motor is arranged inside the casing to rotate the shaft. The cooling medium delivery structure is configured to vary a supply of a cooling medium to the casing. An impeller clearance control apparatus for a centrifugal compressor includes a sensor and a controller. The controller controls a supply of a cooling medium to the casing based on a value detected by the sensor.

Abstract: A centrifugal compressor includes a casing, an impeller, a motor, a diffuser, a magnetic bearing, and a magnetic bearing backup system including at least one dynamic gas bearing and at least one hydrostatic gas bearing. The impeller is attached to a shaft rotatable about a rotation axis. The motor is configured and arranged to rotate the shaft in order to rotate the impeller. The magnetic bearing rotatably supports the shaft. The magnetic bearing backup system is configured and arranged to support the shaft when the magnetic bearing stops operating. The at least one dynamic gas bearing and the at least one hydrostatic gas bearing of the magnetic bearing backup system are disposed radially inwardly relative to the magnetic bearing.

Abstract: A non-condensable gas purge system is configured to be used in a chiller system that uses a low pressure refrigerant in a loop refrigeration circuit. The non-condensable gas purge system includes a purge tank and a purge heat exchanger coil arranged inside the purge tank. The purge tank has a tank inlet for receiving the low pressure refrigerant from a condenser of the refrigeration circuit, a tank outlet for returning the low pressure refrigerant to an evaporator of the refrigeration circuit, and a purge outlet for purging non-condensable gas from the purge tank to the ambient atmosphere. The purge heat exchanger coil is fluidly connected to the loop refrigeration circuit such that the low pressure refrigerant contained in the loop of the chiller system can pass through the purge heat exchanger coil. Refrigerant in the purge tank is condensed by the heat exchanger coil while non-condensable gases remain gaseous.

Abstract: A refrigerating apparatus includes a centrifugal compressor, a capacity control mechanism that controls a capacity of the compressor by changing an opening degree of the capacity control mechanism, an expansion mechanism that reduces a pressure of a refrigerant, and a controller. The controller calculates an opening degree of the expansion mechanism using compressor capacity as one of a plurality of indices of change in load. The compressor capacity is obtained from a current rotation number of the compressor, an opening degree of the capacity control mechanism, and a divergence rate of a current operation head from a surge region.

Abstract: A centrifugal compressor for a chiller system includes a casing, an inlet guide vane, an impeller disposed downstream of the inlet guide vane, a motor and a diffuser. The casing has inlet and outlet portions with the inlet guide vane disposed in the inlet portion. The impeller is attached to a shaft rotatable about a rotation axis, and the motor rotates the shaft in order to rotate the impeller. The centrifugal compressor further includes a casing treatment bypass having an entrance port and an exit port. The casing treatment bypass injects refrigerant from a gap between the impeller and the inlet portion of the casing toward an area between the impeller and the inlet guide vane. The exit port of the casing treatment bypass is positioned upstream in a direction of a refrigerant flow with respect to the entrance port of the casing treatment bypass.

Abstract: A refrigerating apparatus includes a centrifugal compressor, suction and discharge capacity control mechanisms that control capacity of the compressor by changing opening degrees of the suction and discharge capacity control mechanisms, and a controller that compares a compressor-specific surge curve with an isentropic head to perform rotational speed control of the compressor, rotational speed adjustment control of the compressor in order to avoid surge, and emergency shutdown control of the compressor upon detection of surge. The compressor-specific surge curve is stored in the controller in advance, and is defined by an actual rotational speed of the compressor and opening degrees of the suction and discharge capacity control mechanisms. The isentropic head is calculated based on a suction pressure, a discharge pressure, and a suction temperature during operation.

Abstract: A refrigerating apparatus includes a centrifugal compressor, a capacity control mechanism that controls a capacity of the compressor by changing an opening degree of the capacity control mechanism, an expansion mechanism that reduces a pressure of a refrigerant, and a controller. The controller calculates an opening degree of the expansion mechanism using compressor capacity as one of a plurality of indices of change in load. The compressor capacity is obtained from a current rotation number of the compressor, an opening degree of the capacity control mechanism, and a divergence rate of a current operation head from a surge region.

Abstract: A flooded evaporator is provided which can remove floating mist more exactly resulting in that the refrigerant mist is prevented from being sucked into the compressor, and with which heat transfer between the medium to be cooled and refrigerant liquid is improved.