Abstract: A method for controlling a vapour compression system (1) is disclosed. The vapour compression system (1) has an ambient temperature sensor (8) arranged to measure an ambient temperature. A time period during which the ambient temperature sensor (8) is unexposed to solar heating is selected. During the selected time period, measurements of the ambient temperature are obtained by means of the ambient temperature sensor (8), and measurements of at least one further parameter related to the vapour compression system (1) are obtained, while operating the vapour compression system (1). Model parameters for a model of at least a part of the vapour compression system (1) are derived, based on the obtained measurements, the model providing correlation between the ambient temperature and the at least one further parameter.

Abstract: A method for monitoring a refrigerant charge in a vapour compression system (1) is disclosed, the vapour compression system (1) including a compressor unit (2), a heat rejecting heat exchanger (3), a high pressure expansion device (4), a receiver (5), at least one expansion device (9, 10), and at least one evaporator (11, 12) arranged in a refrigerant path. A change in net mass flow into or out of the receiver (5) and/or a change in net enthalpy flow into or out of the receiver (5) is detected, and a pressure inside the receiver (5) is monitored as a function of time, following the detected change in net mass flow and/or in net enthalpy flow. A time constant being representative for dynamics of the receiver (5) is derived, based on the monitored pressure as a function of time, and information regarding a refrigerant charge in the vapour compression system (1) is derived, based on the derived time constant.

Abstract: A method for terminating defrosting of an evaporator (104) is disclosed. The evaporator (104) is part of a vapour compression system (100). The vapour compression system (100) further comprises a compressor unit (101), a heat rejecting heat exchanger (102), and an expansion device (103). The compressor unit (101), the heat rejecting heat exchanger (102), the expansion device (103) and the evaporator (104) are arranged in a refrigerant path, and an air flow is flowing across the evaporator (104). When ice is accumulated on the evaporator (104), the vapour compression system (100) operates in a defrosting mode. At least one temperature sensor (305) monitors a temperature Tair, of air leaving the evaporator (104). A rate of change of Tair is monitored and defrosting is terminated when the rate of change of the temperature, Tair, approaches zero.

Abstract: A method for terminating defrosting of an evaporator (104) is disclosed. The evaporator (104) is part of a vapour compression system (100). The vapour compression system (100) further comprises a compressor unit (101), a heat rejecting heat exchanger (102), and an expansion device (103). The compressor unit (101), the heat rejecting heat exchanger (102), the expansion device (103) and the evaporator (104) are arranged in a refrigerant path, and an air flow is flowing across the evaporator (104). When ice is accumulated on the evaporator (104), the vapour compression system (100) operates in a defrosting mode. At least one temperature sensor (305) monitors a temperature Tair, of air leaving the evaporator (104). A rate of change of Tair is monitored and defrosting is terminated when the rate of change of the temperature, Tair, approaches zero.

Abstract: A method for terminating defrosting of an evaporator (104) is disclosed. The evaporator (104) is part of a vapour compression system (100). The vapour compression system (100) further comprises a compressor unit (101), a heat rejecting heat exchanger (102), and an expansion device (103). The compressor unit (101), the heat rejecting heat exchanger (102), the expansion device (103) and the evaporator (104) are arranged in a refrigerant path, and an air flow is flowing across the evaporator (104). When ice is accumulated on the evaporator (104), the vapour compression system (100) operates in a defrosting mode. At least two temperature sensors (306, 307) monitor an evaporator inlet temperature, Te,in, at a hot gas inlet (304) of the evaporator (104) and an evaporator outlet temperature, Te,out, at a hot gas outlet (305) of the evaporator (104). A difference between Te,in and Te,out, is monitored and defrosting is terminated when the rate of change of the difference between Te,in and Te,out approaches zero.

Abstract: A method for controlling a supply of refrigerant to an evaporator of a vapour compression system, such as a refrigeration system, an air condition system or a heat pump. During normal operation, the opening degree of the expansion valve is controlled on the basis of an air temperature, Tair, of air flowing across the evaporator and/or on the basis of superheat of refrigerant leaving the evaporator. If at least one sensor used for obtaining Tair or the superheat is malfunctioning, operation of the vapour compression system is switched to a contingency mode. A reference temperature, Tout, ref, is calculated, based on previously obtained values of a temperature, Tout, of refrigerant leaving the evaporator, during a predefined previous time interval, and subsequently the opening degree of the expansion valve is controlled on the basis of the obtained temperature, Tout, in order to reach the calculated reference temperature, Tout, ref.

Abstract: A method for controlling a supply of refrigerant to an evaporator (2) of a vapour compression system (1), such as a refrigeration system, an air condition system or a heat pump. During normal operation, the opening degree of the expansion valve (3) is controlled on the basis of an air temperature, Tair, of air flowing across the evaporator (2) and/or on the basis of superheat of refrigerant leaving the evaporator (2). In the case that at least one sensor (5, 6, 23, 24) used for obtaining Tair or the superheat is malfunctioning, operation of the vapour compression system (1) is switched to a contingency mode.

Abstract: A control arrangement for controlling a superheat of a vapour compression system includes a first sensor and a second sensor for measuring control parameters allowing a superheat value to be derived, a first controller arranged to receive a signal from the first sensor, a second controller arranged to receive a superheat value derived by a subtraction element, and to supply a control signal, based on the derived superheat value and a reference superheat value, and a summation element arranged to receive input from the the controllers, the summation element being arranged to supply a control signal for controlling opening degree of the expansion device. According to a first aspect the control arrangement includes a low pass filter arranged to receive a signal from the first sensor and to supply a signal to the subtraction element. According to a second aspect the first controller includes a PD element.

Abstract: A method for controlling a supply of refrigerant to an evaporator (2) of a vapour compression system (1) is disclosed. During a system identification phase an opening degree (12) of the expansion valve (3) is alternatingly increased and decreased, and a maximum temperature difference, (S4?S2)max, between temperature, S4, of air flowing away from the evaporator (2) and temperature, S2, of refrigerant leaving the evaporator (2) is determined. During normal operation, the supply of refrigerant to the evaporator (2) is controlled by calculating a reference temperature, S2,ref, based on the monitored temperature, S4, and the maximum temperature difference, (S4?S2)max, determined during the system identification phase. The supply of refrigerant to the evaporator (2) is controlled in order to obtain a temperature, S2, of refrigerant leaving the evaporator (2) which is substantially equal to the calculated reference temperature, S2,ref.

Abstract: A method for controlling a vapor compression system during start-up is disclosed. The rate of change, ?T1, of the temperature of refrigerant entering the evaporator, and the rate of change, ?T2, of the temperature of refrigerant leaving the evaporator are compared. Based on the comparing step, a refrigerant filling state of the evaporator is determined. The opening degree of the expansion device is then controlled according to a first control strategy in the case that it is determined that the evaporator is full or almost full, and according to a second control strategy in the case that it is determined that the evaporator is not full. Thereby it is ensured that a maximum filling degree of the evaporator is quickly reached, without risking that liquid refrigerant passes through the evaporator.

Abstract: A method for calibrating a temperature sensor arranged in a vapor compression system is disclosed. The opening degree of an expansion device is alternatingly increased and decreased. Simultaneously a temperature of refrigerant entering the evaporator and a temperature of refrigerant leaving the evaporator are monitored. For each cycle of the opening degree of the expansion device, a maximum temperature, T1, max, of refrigerant entering the evaporator, and a minimum temperature, T2, min, of refrigerant leaving the evaporator are registered. A calibration value, ?T1, is calculated as ?T1=C?(T2, min?T1, max) for each cycle, and a maximum calibration value, among the calculated values is selected. Finally, temperature measurements performed by the first temperature sensor are adjusted by an amount defined by ?T1, max.

Abstract: A method for controlling a supply of refrigerant to an evaporator (5) of a vapor compression system (1), such as a refrigeration system, an air condition system or a heat pump, is disclosed. The vapor compression system (1) comprises an evaporator (5), a compressor (2), a condenser (3) and an expansion device (4) arranged in a refrigerant circuit. The method comprises the steps of: Actuating a component, such as an expansion valve (4), a fan or a compressor (2), of the vapor compression system (1) in such a manner that a dry zone in the evaporator (5) is changed; measuring a temperature signal representing a temperature of refrigerant leaving the evaporator (5); analyzing the measured temperature signal, e.g.

Abstract: A method for controlling a supply of refrigerant to an evaporator (2) of a vapour compression system (1), such as a refrigeration system, an air condition system or a heat pump. The opening degree of the expansion valve (3) is controlled on the basis of an air temperature, Tair, of air flowing across the evaporator (2), and in order to reach a reference air temperature, Tair, ref. The opening degree is set to the calculated opening degree, overlaid with a perturbation signal. A temperature signal, S2, representing a temperature of refrigerant leaving the evaporator (2) is monitored and analysed. In the case that the analysis reveals that a dry zone of the evaporator (2) is approaching a minimum length, the opening degree of the expansion valve (3) is decreased. This provides a safety mechanism which ensures that liquid refrigerant is prevented from passing through the evaporator (2).

Abstract: A method for determining wire connections in a vapor compression system (1) is disclosed. The vapor compression system comprises a compressor, a condenser, an expansion device (2) and an evaporator (3) being fluidly interconnected in a refrigerant path, and two or more sensor devices (7, 8, 9, 10, 11) arranged for measuring variables which are relevant for the operation of the vapor compression system (1). The method comprises the steps of changing an operational setting, e.g. an opening degree of the expansion device (2) for the vapor compression system (1), monitoring variable values, such as temperatures, being measured by at least two sensor devices (7, 8, 9, 10, 11), e.g.

Abstract: A method for controlling operation of a vapour compression system (1) is provided, the vapour compression system (1) comprising two or more refrigeration entities, such as display cases. A signal representing a reference power consumption is received and compared to an actual power consumption of the vapour compression system (1). Based on the comparison, local controllers (3) calculate a setpoint temperature for a corresponding refrigeration entity, in order to obtain a power consumption which is equal to the reference power consumption. Each refrigeration entity is controlled in accordance with the calculated setpoint temperatures.

Abstract: A control arrangement (1) for controlling a superheat of a vapour compression system is disclosed. The control arrangement (1) comprises a first sensor (4) and a second sensor (5) for measuring control parameters allowing a superheat value to be derived; a first controller (6) arranged to receive a signal from the first sensor (4), a second controller (10) arranged to receive a superheat value derived by a subtraction element (9), and to supply a control signal, based on the derived superheat value, and in accordance with a reference superheat value, and a summation element (8) arranged to receive input from the first controller (6) and from the second controller (10), said summation element (8) being arranged to supply a control signal for controlling opening degree of the expansion device (3) on the basis of the received input.

Abstract: A method for controlling a vapour compression system during start-up is disclosed. The rate of change, ?T1, of the temperature of refrigerant entering the evaporator, and the rate of change, ?T2, of the temperature of refrigerant leaving the evaporator are compared. Based on the comparing step, a refrigerant filling state of the evaporator is determined. The opening degree of the expansion device is then controlled according to a first control strategy in the case that it is determined that the evaporator is full or almost full, and according to a second control strategy in the case that it is determined that the evaporator is not full. Thereby it is ensured that a maximum filling degree of the evaporator is quickly reached, without risking that liquid refrigerant passes through the evaporator.

Abstract: A method for calibrating a temperature sensor arranged in a vapour compression system is disclosed. The opening degree of an expansion device is alternatingly increased and decreased. Simultaneously a temperature of refrigerant entering the evaporator and a temperature of refrigerant leaving the evaporator are monitored. For each cycle of the opening degree of the expansion device, a maximum temperature, T1, max, of refrigerant entering the evaporator, and a minimum temperature, T2, min, of refrigerant leaving the evaporator are registered. A calibration value, ?T1, is calculated as ?T1=C?(T2, min?T1, max) for each cycle, and a maximum calibration value, among the calculated values is selected. Finally, temperature measurements performed by the first temperature sensor are adjusted by an amount defined by ?T1, max.

Abstract: A method for controlling a supply of refrigerant to an evaporator (5) of a vapour compression system (1), such as a refrigeration system, an air condition system or a heat pump, is disclosed. The vapour compression system (1) comprises an evaporator (5), a compressor (2), a condenser (3) and an expansion device (4) arranged in a refrigerant circuit. The method comprises the steps of: Actuating a component, such as an expansion valve (4), a fan or a compressor (2), of the vapour compression system (1) in such a manner that a dry zone in the evaporator (5) is changed; measuring a temperature signal representing a temperature of refrigerant leaving the evaporator (5); analysing the measured temperature signal, e.g.

Abstract: A method for determining wire connections in a vapour compression system (1) is disclosed. The vapour compression system comprises a compressor, a condenser, an expansion device (2) and an evaporator (3) being fluidly interconnected in a refrigerant path, and two or more sensor devices (7, 8, 9, 10, 11) arranged for measuring variables which are relevant for the operation of the vapour compression system (1). The method comprises the steps of changing an operational setting, e.g. an opening degree of the expansion device (2) for the vapour compression system (1), monitoring variable values, such as temperatures, being measured by at least two sensor devices (7, 8, 9, 10, 11), e.g.