Patent ID: 8769976

Claim:
A method for controlling a refrigerant distribution in a vapour compression system, the vapour compression system comprising a compressor, a condenser, at least two evaporators fluidly connected in parallel between the compressor and a common outlet, and a a valve, which is capable of distributing refrigerant to each of the evaporators in accordance with previously defined amounts of available refrigerant for distribution as refrigerant mass flow between the at least two evaporators, for controlling a flow of refrigerant across each of the evaporators, the method comprising the steps of: a) monitoring a superheat, SH, of refrigerant at the common outlet only, said monitoring of a superheat, SH, being performed by either one of: monitoring a temperature, T, of refrigerant at the common outlet only or monitoring a pressure, P, of refrigerant at the common outlet only, b) modifying the distribution of refrigerant through the evaporators in such a manner that a mass flow of refrigerant through a first evaporator is altered while keeping the total mass flow of refrigerant through all the evaporators constant, c) when a significant change in superheat SH occurs, detecting a control parameter based on the change in mass flow of refrigerant through the first evaporator obtained during step b), wherein the significant change in superheat SH is either one of: 1) a sudden decrease in superheat SH that is prompted by liquid refrigerant being allowed to pass through the first evaporator, or 2) a sudden increase in superheat SH that is prompted by gaseous refrigerant being allowed to pass through the first evaporator, wherein said control parameter is either one of: 1) a difference in a degree of opening of the valve, which provides information about how much the mass flow of refrigerant through the first evaporator has been increased and which provides information as to how much the degree of opening can be increased before liquid refrigerant passes through the evaporator, or 2) a length of a time interval elapsing until the significant change in superheat SH occurs, which provides information as to how long it takes from fully opening a valve until liquid refrigerant passes through the evaporator, d) repeating steps a) to c) for each of the remaining evaporator(s), and e) adjusting the distribution of refrigerant through each of the evaporators on the basis of the detected control parameters.