A method for controlling a variable capacity ejector unit (7) arranged in a refrigeration system (1) is disclosed. An ejector control signal for the ejector unit (7) is generated, based on an obtained temperature and an obtained pressure of refrigerant leaving a heat rejecting heat exchanger (3), or on the basis of a high pressure valve control signal for controlling an opening degree of a high pressure valve (6) arranged fluidly in parallel with the ejector unit (7). The ejector control signal indicates whether the capacity of the ejector unit (7) should be increased, decreased or maintained. The capacity of the ejector unit (7) is controlled in accordance with the generated ejector control signal. The power consumption of the refrigeration system (1) is reduced, while the pressure of the refrigerant leaving the heat rejecting heat exchanger (3) is maintained at an acceptable level.

An air-conditioning apparatus includes a first flow switching unit configured to be switched between a first state in which refrigerant communication between a compressor and a second load-side heat exchanger is blocked and a second state in which the compressor is in refrigerant communication with a first load-side heat exchanger and the second load-side heat exchanger. The air-conditioning apparatus further includes a second flow switching unit configured to be switched between a third state in which refrigerant communication between the second load-side heat exchanger and a heat-source-side heat exchanger is blocked and a fourth state in which the first load-side heat exchanger is in refrigerant communication with the second load-side heat exchanger and the heat-source-side heat exchanger. The first heat exchanger is located upstream of the second load-side heat exchanger. The second flow switching unit is located downstream of the second load-side heat exchanger.

A method of controlling an HVAC circuit, comprises allowing refrigerant to circulate within the HVAC circuit, wherein the HVAC circuit comprises an evaporator coil, a condenser coil, at least one fan configured to provide airflow to the condenser coil, at least one expansion valve, and at least one compressor. The method continues by receiving a temperature measurement and determining based on the temperature measurement, a minimum fan speed configured to avoid pressure spikes within the condenser coil. The method concludes by sending a signal to the at the least one fan to direct the at least one fan to spin at a rate greater than or equal to the minimum fan speed when the measured temperature is less than a predetermined temperature, wherein, when the refrigerant circulates through the condenser coil, the minimum fan speed is greater than zero rotations per minute.

The present disclosure concerns a device and a method for chiller station management for providing chilled water to a load (30), a computer storage medium and a chiller station. The method for chiller station management includes: determining whether a chiller (10) with a low load exists in a chiller station and determining whether to allow to shut down one chiller (10) in the chiller station, when a certain chiller (10) in the chiller station transmits a surge risk signal; if yes, shutting down one chiller (10) in the chiller station to increase loads of other chillers (10); and if no, raising a chiller (10) outlet water temperature in the chiller station and/or lowering a cooling tower (20) outlet water temperature in the chiller station. The device and method for chiller station management according to the present disclosure provide a surge protection at a chiller station level, thereby effectively avoiding occurrence of surge in the chiller, and improving the efficiency and operation stability of the chiller station.

A refrigeration system includes an evaporator within which a refrigerant absorbs heat, a gas cooler/condenser within which the refrigerant rejects heat, a compressor operable to circulate the refrigerant between the evaporator and the gas cooler/condenser, a high pressure valve operable to control a pressure of the refrigerant at an outlet of the gas cooler/condenser, and a controller. The controller is configured to automatically generate a setpoint for a measured or calculated variable of the refrigeration system based on a measured temperature of the refrigerant at the outlet of the gas cooler/condenser. The setpoint is generated using a stored relationship between the measured temperature and a maximum estimated coefficient of performance (COP) that can be achieved at the measured temperature. The controller is configured to operate the high pressure valve to drive the measured or calculated variable toward the setpoint.

In some embodiments, an air-cooled ammonia refrigeration system comprises: a plurality of air-cooled condensers, each having a heat exchanger and at least one axial fan and having a first operating state capable of condensing vaporous ammonia to form liquid ammonia; an evaporator coupled to the air-cooled condenser; a subcooler positioned between the air-cooled condenser and the evaporator; a compressor coupled to the evaporator; an oil cooler coupled to the compressor; and a plurality of valves coupled to the plurality of air-cooled condensers and having a first configuration corresponding to the first operating state of the plurality of air-cooled condensers, and a second configuration corresponding to a second operating state of one or more of the plurality of air-cooled condensers such that the one or more of the plurality of air-cooled condensers functions as an evaporator capable of evaporating liquid ammonia to form vaporous ammonia.

A heating, ventilation, and/or air conditioning (HVAC) unit includes a refrigerant circuit including a reheat coil and a condenser system, a first valve disposed along the refrigerant circuit and configured to modulate refrigerant flow to the reheat coil and to the condenser system, and a second valve disposed along the refrigerant circuit downstream of the first valve relative to a direction of the refrigerant flow through the refrigerant circuit. The condenser system includes a first condenser coil and a second condenser coil, and the second valve is configured to be actuated to control refrigerant flow to the second condenser coil.

A refrigeration cycle apparatus includes a refrigeration cycle circuit, a bypass flow path, a first valve provided in the refrigeration cycle circuit, a second valve provided at the bypass flow path, a first temperature sensor configured to detect a temperature of an indoor space, a second temperature sensor configured to detect a temperature of refrigerant on a liquid side of an indoor heat exchanger, and a notification part. The refrigeration cycle apparatus is able to operate in an operation state where the compressor operates, the indoor heat exchanger functions as an evaporator, and the first valve is open while the second valve is closed. In the operation state, the notification part issues notification of an abnormality of an electronic expansion valve or the first valve when a temperature detected by the second temperature sensor is higher than an evaporation temperature of refrigerant in the refrigeration cycle circuit.

An air-conditioning apparatus includes heat-source-side units each including a compressor and a heat-source-side heat exchanger, a load-side heat exchanger and a load-side expansion device, a first header, a second header, bypass expansion devices, circuit switching units, discharge pressure sensors, bypass pressure sensors, and a controller configured to control, in a heat-source-side unit in defrosting mode, the circuit switching unit in such a manner that a portion of refrigerant discharged from the compressor flows into the heat-source-side heat exchanger and configured to control, in the heat-source-side unit in defrosting mode, an opening degree of the bypass expansion device in the heat-source-side unit in such a manner that a value representing a difference between a value obtained by the discharge pressure sensor and a value obtained by the bypass pressure sensor is equal to or greater than a predetermined value.

The present disclosure concerns a device and a method for chiller station management for providing chilled water to a load (30), a computer storage medium and a chiller station. The method for chiller station management includes: determining whether a chiller (10) with a low load exists in a chiller station and determining whether to allow to shut down one chiller (10) in the chiller station, when a certain chiller (10) in the chiller station transmits a surge risk signal; if yes, shutting down one chiller (10) in the chiller station to increase loads of other chillers (10); and if no, raising a chiller (10) outlet water temperature in the chiller station and/or lowering a cooling tower (20) outlet water temperature in the chiller station. The device and method for chiller station management according to the present disclosure provide a surge protection at a chiller station level, thereby effectively avoiding occurrence of surge in the chiller, and improving the efficiency and operation stability of the chiller station.