Abstract: A method for controlling a vapour compression system (1) is disclosed. Malfunctioning of a gas bypass valve (8) is registered. An actual opening degree of the gas bypass valve (8) is derived, and a target opening degree of the gas bypass valve (8) is derived, based on one or more control parameters of the vapour compression system (1). The actual opening degree is compared to the target opening degree, and the vapour compression system (1) is controlled based on the comparison, and in order to match a mass flow of gaseous refrigerant through the gas bypass valve (8) to the actual opening degree of the gas bypass valve (8).

Abstract: A method for controlling ejector capacity in a vapour compression system (1) is disclosed. A parameter value being representative for a flow rate of liquid refrigerant from the evaporator(s) (8, 10) and into a return pipe (12, 13) is obtained, and the capacity of the ejector(s) (6) is adjusted based on the obtained parameter value. Ejector capacity may be shifted between low pressure ejectors (liquid ejectors) (6a, 6b, 6c, 6d) and high pressure ejectors (gas ejectors) (6e, 6f).

Abstract: A refrigeration system including one or more first compressor(s) for compressing a carbon dioxide (CO2) refrigerant, a main heat rejection system for cooling the CO2 refrigerant, one or more high pressure expansion device(s) for reducing the pressure of the CO2 refrigerant, a receiver for storing the CO2 refrigerant, one or more high pressure expansion device(s), an evaporator and a receiver pressure regulating device. The refrigeration system further includes an auxiliary refrigeration system including an auxiliary compressor arranged to compress at least part of the CO2 refrigerant and thereafter to direct the compressed CO2 refrigerant to a heat rejection system.

Abstract: A method for controlling a vapour compression system (1) is disclosed, the vapour compression system (1) comprising at least one expansion device (8) and at least one evaporator (9). For each expansion device (8), an opening degree of the expansion device (8) is obtained, and a representative opening degree, ODrep, is identified based on the obtained opening degree(s) of the expansion device(s) (8). The representative opening degree could be a maximum opening degree, ODmax, being the largest among the obtained opening degrees. The representative opening degree, ODrep, is compared to a predefined target opening degree, ODtarget, and a minimum setpoint value, SPrec, for a pressure prevailing inside a receiver (7), is calculated or adjusted, based on the comparison. The vapour compression system (1) is controlled to obtain a pressure inside the receiver (7) which is equal to or higher than the calculated or adjusted minimum setpoint value, SPrec.

Abstract: A method for controlling a vapour compression system (1) is disclosed. A mass flow of refrigerant along a part of the refrigerant path is estimated, based on measurements performed by one or more pressure sensors (10, 12, 13) for measuring a refrigerant pressure at selected positions along the refrigerant path and one or more temperature sensors (11, 14) for measuring a refrigerant temperature at selected positions along the refrigerant path. A refrigerant pressure or a refrigerant temperature at a selected position a pressure sensor (10, 12, 13) or temperature sensor (11, 14) along the refrigerant path is derived, based on the estimated mass flow. The vapour compression system (1) is allowed to continue operating, even if a sensor (10, 11, 12, 13, 14) is malfunctioning or unreliable.

Abstract: A method for controlling ejector capacity in a vapour compression system (1) is disclosed. A parameter value being representative for a flow rate of liquid refrigerant from the evaporator(s) (8, 10) and into a return pipe (12, 13) is obtained, and the capacity of the ejector(s) (6) is adjusted based on the obtained parameter value. Ejector capacity may be shifted between low pressure ejectors (liquid ejectors) (6a, 6b, 6c, 6d) and high pressure ejectors (gas ejectors) (6e, 6f).

Abstract: A method for controlling ejector capacity in a vapour compression system (1) is disclosed. A parameter value being representative for a flow rate of liquid refrigerant from the evaporator(s) (8, 10) and into a return pipe (12, 13) is obtained, and the capacity of the ejector(s) (6) is adjusted based on the obtained parameter value. Ejector capacity may be shifted between low pressure ejectors (liquid ejectors) (6a, 6b, 6c, 6d) and high pressure ejectors (gas ejectors) (6e, 6f).

Abstract: A method for controlling a vapour compression system (1) is disclosed, the vapour compression system (1) comprising at least one compressor (2, 16), a heat rejecting heat exchanger (3), a high pressure expansion device (4, 15, 17), a receiver (5), an evaporator expansion device (6), an evaporator (7) and a gas bypass valve (8), arranged in a refrigerant path. It is registered that the gas bypass valve (8) is malfunctioning or saturated, and a pressure value for a pressure prevailing inside the receiver (5) is obtained. Finally, the vapour compression system (1) is controlled in order to control a gaseous refrigerant supply to the receiver (5) to adjust the pressure prevailing inside the receiver (5) to reach a target pressure level.

Abstract: A method for controlling a vapour compression system, the vapour compression system including a compressor unit with one or more compressors. At least one of the compressors is connectable to a gaseous outlet of a receiver, and at least one of the compressors is connectable to an outlet of an evaporator. A parameter of the vapour compression system is measured, an enthalpy of refrigerant leaving the heat rejecting heat exchanger being derivable from the measured parameter. A setpoint value for a pressure inside the receiver is calculated, based on the measured parameter, and the compressor unit is operated in accordance with the calculated setpoint value, and in order to obtain a pressure inside the receiver which is equal to the calculated setpoint value. The vapour compression system is operated in an energy efficient manner over a wide range of ambient temperatures.

Abstract: A method for controlling a vapour compression system in an energy efficient and stable manner, the vapour compression system (1) including at least two evaporator groups (5a, 5b, 5c), each evaporator group (5a, 5b, 5c) including an ejector unit (7a, 7b, 7c), at least one evaporator (9a, 9b, 9c) and a flow control device (8a, 8b, 8c) controlling a flow of refrigerant to the at least one evaporator (9a, 9b, 9c). For each evaporator group (5a, 5b, 5c) the outlet of the evaporator (9a, 9b, 9c) is connected to a secondary inlet (12a, 12b, 12c) of the corresponding ejector unit (7a, 7b, 7c).

Abstract: A method for controlling a vapour compression system having an ejector includes, in the case that a pressure difference between a pressure prevailing in the receiver and a pressure of refrigerant leaving the evaporator decreases below a first lower threshold value, the pressure of refrigerant leaving the heat rejecting heat exchanger is kept at a level which is slightly higher than the pressure level providing optimal coefficient of performance.

Abstract: A method for controlling a vapour compression system (1) is disclosed. The vapour compression system (1) comprises an ejector (6) and a liquid separating device (10) arranged in a suction line. A liquid level sensor (18) is arranged in the liquid separating device (10). A liquid level in the liquid separating device (10) is monitored by means of the liquid level sensor (18). In the case that the liquid level in the liquid separating device (10) is above a predefined threshold level, a control parameter of the vapour compression system (1) is adjusted in order to increase a flow rate of refrigerant from the liquid separating device (10) to the secondary inlet (15) of the ejector (6) and/or decrease a flow rate of liquid refrigerant from the evaporator(s) (9) to the liquid separating device (10).

Abstract: 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.

Abstract: A method for controlling a vapor compression system (1) is disclosed, the vapor compression system (1) comprising an ejector (5). The method comprises controlling a compressor unit (2) in order to adjust a pressure inside a receiver (6), on the basis of a detected pressure of refrigerant leaving an evaporator (8). The portion of refrigerant leaving the evaporator (8) which is supplied to a secondary inlet (15) of the ejector is maximized and the portion of refrigerant supplied directly to the compressor unit (2) is minimized, while ensuring that the pressure of refrigerant leaving the evaporator (8) does not decrease below an acceptable level.

Abstract: A vapour compression system (1) includes an ejector (6) and a liquid separating device (10) arranged in a suction line. At least one evaporator (9) is allowed to be operated in a flooded state. A flow rate of refrigerant from the liquid separating device (10) to the secondary inlet (15) of the ejector (6) is detected, and it is determined whether or not the flow rate is sufficient to remove liquid refrigerant produced by the evaporator(s) (9) from the liquid separating device (10). In the case that it is determined that the flow rate of refrigerant from the liquid separating device (10) to the secondary inlet (15) of the ejector (6) is insufficient to remove liquid refrigerant produced by the evaporator(s) (9), the flow rate of refrigerant from the liquid separating device (10) to the secondary inlet (15) of the ejector (6) is increased, and/or a flow rate of liquid refrigerant from the evaporator(s) (9) to the liquid separating device (10) is decreased.

Abstract: A method for controlling ejector capacity in a vapour compression system (1) is disclosed. A parameter value being representative for a flow rate of liquid refrigerant from the evaporator(s) (8, 10) and into a return pipe (12, 13) is obtained, and the capacity of the ejector(s) (6) is adjusted based on the obtained parameter value. Ejector capacity may be shifted between low pressure ejectors (liquid ejectors) (6a, 6b, 6c, 6d) and high pressure ejectors (gas ejectors) (6e, 6f).

Abstract: A method for controlling a vapour compression system (1) is disclosed. Malfunctioning of a gas bypass valve (8) is registered. An actual opening degree of the gas bypass valve (8) is derived, and a target opening degree of the gas bypass valve (8) is derived, based on one or more control parameters of the vapour compression system (1). The actual opening degree is compared to the target opening degree, and the vapour compression system (1) is controlled based on the comparison, and in order to match a mass flow of gaseous refrigerant through the gas bypass valve (8) to the actual opening degree of the gas bypass valve (8).

Abstract: A method for controlling a vapour compression system (1) is disclosed. A mass flow of refrigerant along a part of the refrigerant path is estimated, based on measurements performed by one or more pressure sensors (10, 12, 13) for measuring a refrigerant pressure at selected positions along the refrigerant path and one or more temperature sensors (11, 14) for measuring a refrigerant temperature at selected positions along the refrigerant path. A refrigerant pressure or a refrigerant temperature at a selected position a pressure sensor (10, 12, 13) or temperature sensor (11, 14) along the refrigerant path is derived, based on the estimated mass flow. The vapour compression system (1) is allowed to continue operating, even if a sensor (10, 11, 12, 13, 14) is malfunctioning or unreliable.

Abstract: A method for controlling a vapour compression system (1) is disclosed, the vapour compression system (1) comprising at least one compressor (2, 16), a heat rejecting heat exchanger (3), a high pressure expansion device (4, 15, 17), a receiver (5), an evaporator expansion device (6), an evaporator (7) and a gas bypass valve (8), arranged in a refrigerant path. It is registered that the gas bypass valve (8) is malfunctioning or saturated, and a pressure value for a pressure prevailing inside the receiver (5) is obtained. Finally, the vapour compression system (1) is controlled in order to control a gaseous refrigerant supply to the receiver (5) to adjust the pressure prevailing inside the receiver (5) to reach a target pressure level.

Abstract: A method for controlling a valve arrangement (12), e.g. in the form of a three way valve, in a vapor compression system (1) is disclosed, the vapor compression system (1) comprising an ejector (6). The valve arrangement (12) is arranged to supply refrigerant to a compressor unit (2) from the gaseous outlet (11) of a receiver (7) and/or from the outlet of an evaporator (9). The vapor compression system (1) may be operated in a first mode of operation (summer mode) or in a second mode of operation (winter mode). When operated in the second mode of operation, it is determined whether or not conditions for operating the vapor compression system (1) in the first mode of operation are prevailing. If this is the case, the valve arrangement (12) is actively switched to the first mode of operation by closing a first inlet (13) towards the evaporator (7) and fully opening a second inlet (14) towards the receiver (7).