A refrigeration system is disposed within a refrigerator having a freezer compartment and a refrigeration compartment. The refrigeration system includes an evaporator having an inlet and an outlet. A damper is positioned so as to direct air flow into the freezer compartment or the refrigeration compartment and correspondingly block air flow to the other. A compressor is coupled to the evaporator via a conduit and a control valve is coupled to the inlet of the evaporator to control flow of refrigerant. A condenser is coupled to the control valve by a liquid line. A first temperature sensor is positioned so as to detect refrigerant temperature within the evaporator and a second temperature sensor is positioned so as to detect refrigerant temperature at the outlet of the evaporator. A first controller is coupled to the control valve and to the first and second temperature sensors to receive temperature signals therefrom. A second controller is coupled to the compressor to provide compressor signals thereto and to the damper to send damper signals thereto. The first controller controls the duty cycle of the control valve.