Danfoss A/s

Jan Prins

Frede Schmidt

Kristian Fredslund

Kenneth Bank Madsen

Lars Finn Sloth Larsen

Torben Green

Peter Reichwald

Salvatore Piscopiello

A method for controlling a vapour compression system () is disclosed. The vapour compression system () includes an ejector (), and has a non-return valve () arranged in the refrigerant path between an outlet () of an evaporator () and an inlet () of a compressor unit (), in such a manner that a refrigerant flow from the outlet () of the evaporator () towards the inlet () of the compressor unit () is allowed, while a fluid flow from the inlet () of the compressor unit () towards the outlet () of the evaporator () is prevented. A pressure, P, of refrigerant leaving the evaporator () is measured and a value being representative for a pressure, P, of refrigerant entering the compressor unit () is obtained. The pressures, Pand P, are compared to respective reference pressure values, Pand P. In the case that ε>ε, where ε=P−Pand ε=P−P, the compressor unit () is controlled based on P, and in the case that ε>ε, the compressor unit () is controlled based on P.

Method for controlling suction pressure of a vapour compression system

A method for configuring a plurality of operating setpoints for a vapour compression system () is disclosed. The plurality of operating setpoints are divided into a first group () of operating setpoints to be generated manually and a second group () of operating setpoints to be generated automatically, and the operating setpoints are operated in accordance therewith. The manually generated operating setpoints () and the automatically generated operating setpoints () are provided to a setpoint manager (), and the setpoint manager () checks if the provided operating setpoints () are in compliance with a set of rules. In the case that at least some of the provided operating setpoints () are not in compliance with the set of rules, the setpoint manager () adjusts at least some of the provided operating setpoints () in accordance with the set of rules, thereby obtaining an adjusted set of operating setpoints. The vapour compression system () is subsequently controlled in accordance with the adjusted set of operating setpoints.

Method for configuring setpoints for a vapour compression system

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

Method for controlling a vapour compression system during gas bypass valve malfunction

A method for controlling a vapour compression system () including a compressor unit () including one or more compressors (), a heat rejecting heat exchanger (), a receiver (), an expansion device () and an evaporator () arranged in a refrigerant path. A pressure value indicating a pressure prevailing inside the receiver () is obtained, and the obtained pressure value is compared to a first threshold pressure value. In the case that the obtained pressure value is below the first threshold pressure value, the compressor(s) () of the compressor unit () are controlled in order to reduce a suction pressure of the vapour compression system ().

Method for controlling a vapour compression system at a reduced suction pressure

A method for controlling a vapour compression system () including a compressor unit () including at least two compressors (), a heat rejecting heat exchanger (), a receiver (), an expansion device () and an evaporator () arranged in a refrigerant path is disclosed. At least one of the compressors is a main compressor () being fluidly connected to an outlet of the evaporator () and at least one of the compressors is a receiver compressor () being fluidly connected to a gaseous outlet () of the receiver (). A flow of vapour entering the receiver (), such as a mass flow of vapour entering the receiver () is estimated and compared to a first threshold value. In the case that the estimated flow is above the first threshold value, a pressure prevailing inside the receiver () is controlled by operating the receiver compressor ().

Method for controlling a vapour compression system based on estimated flow

A method for controlling ejector capacity in a vapour compression system () is disclosed. A parameter value being representative for a flow rate of liquid refrigerant from the evaporator(s) () and into a return pipe () is obtained, and the capacity of the ejector(s) () is adjusted based on the obtained parameter value. Ejector capacity may be shifted between low pressure ejectors (liquid ejectors) () and high pressure ejectors (gas ejectors) ().

Method for controlling ejector capacity in a vapour compression system

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

Method for controlling a vapour compression system with a variable receiver pressure setpoint

A method for controlling a vapour compression system () 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 () for measuring a refrigerant pressure at selected positions along the refrigerant path and one or more temperature sensors () 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 () or temperature sensor () along the refrigerant path is derived, based on the estimated mass flow. The vapour compression system () is allowed to continue operating, even if a sensor () is malfunctioning or unreliable.

Method for handling fault mitigation in a vapour compression system

A method for controlling suction pressure in a vapour compression system including one or more cooling entities is disclosed. For each cooling entity, a maximum required suction pressure and/or a required change in suction pressure for maintaining a target temperature in the refrigerated volume is obtained. A most loaded cooling entity among the one or more cooling entities is identified, based on the maximum required suction pressures and/or the required changes in suction pressure. The suction pressure of the vapour compression system is controlled in accordance with the maximum required suction pressure and/or required change in suction pressure for the identified most loaded cooling entity.

Method for controlling suction pressure based on a most loaded cooling entity

A method for operating a compressor unit () comprising one or more compressors () is disclosed, the compressor unit () being arranged in a vapour compression system (). Two or more options for distributing the available compressor capacity of the compressor unit () between being connected to a high pressure suction line () and to a medium pressure suction line () are defined. For each option, an expected impact on one or more operating parameters of the vapour compression system (), resulting from distributing the available compressor capacity according to the option, is predicted. An option is selected, based on the predicted expected impact for the options, and based on current operating demands of the vapour compression system (), and the available compressor capacity is distributed according to the selected option, e.g. by means of settings of one or more valve arrangements ().

Method for switching compressor capacity

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

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.

Method for operating a vapour compression system with a receiver

A method for operating a vapour compression system () comprising a heat recovery heat exchanger () is disclosed. The heat recovery system requests a required level of recovered heat to be provided by the heat recovery heat exchanger () to the heat recovery system, generates a signal indicating the required level of recovered heat, and supplies the generated signal to a control unit of the vapour compression system (). A setpoint value for at least one control parameter of the vapour compression system () is calculated, based on the generated signal, and the vapour compression system () is operated in accordance with the calculated setpoint value(s).

Method for operating a vapour compression system with heat recovery

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

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Nordborg, Denmark

Jan Prins