Expansion valve control system

A vapor compression system, comprising:

• a condenser configured to transfer heat from a refrigerant to a cooling fluid;
• an evaporator configured to transfer heat from the refrigerant to a conditioning fluid;
• an expansion valve configured to direct the refrigerant from the condenser to the evaporator;
• a sensor configured to provide feedback indicative of a temperature of the conditioning fluid exiting the evaporator;
• and
• a controller comprising a memory and processing circuitry, wherein the processing circuitry is configured to:
• receive a signal from the sensor indicative of the temperature of the conditioning fluid exiting the evaporator;
• determine a temperature difference between the temperature of the conditioning fluid exiting the evaporator and a saturated temperature of the refrigerant within the evaporator;
• adjust operation of the expansion valve based on a comparison of the temperature difference and a temperature difference set point, wherein the temperature difference set point is a variable temperature difference set point;
• and
• adjust a value of the variable temperature difference set point based on data indicative of a capacity of the evaporator.

A method of controlling an expansion valve of a vapor compression system, the method comprising:

• detecting a temperature of a conditioning fluid exiting a heat exchanger;
• determining a temperature difference between the temperature of the conditioning fluid and a saturated temperature of a refrigerant within the heat exchanger;
• adjusting the expansion valve toward a closed position based on a determination that the temperature difference is less than a temperature difference set point, wherein the temperature difference set point is a variable temperature difference set point;
• adjusting a value of the variable temperature difference set point based on data indicative of a capacity of the heat exchanger;
• and
• adjusting the expansion valve toward an open position based on a determination that the temperature difference is greater than the variable temperature difference set point.