In-situ oil circulation ratio measurement system for vapor compression cycle systems

A method, the method comprising:

• receiving, from an oil level sensor in an oil collector, a signal indicative of oil in the oil collector being at a first level;
• closing, in response to the oil being at the first oil level, a valve to prevent oil from flowing from the oil collector to a low-pressure line of a vapor-compression refrigeration system (VCRS);
• separating, with an oil separator in fluid communication with the oil collector and the low pressure line, an oil flow from an oil and refrigerant flow received from the low-pressure line;
• providing the separated oil flow to the oil collector;
• receiving, from the oil level sensor, a signal indicative of oil in the oil collector being at a second level
• opening, in response to the oil being at a second level, the valve to release oil from the oil collector to the low-pressure line;
• generating an oil cycle ratio for the VCRS based on the amount of oil measured between the level and the second level;
• and
• outputting the oil cycle ratio.

A vapor-compression

• refrigeration system, comprising:
• a processor;
• a low-pressure vapor line that fluidly couples an evaporator and a compressor;
• a high-pressure liquid line fluidly connecting a condenser to the evaporator;
• a mass flow meter configured to measure a flow rate of a refrigerant and oil flow in the liquid line;
• an oil measurement loop fluidly coupled to the low-pressure vapor line, the oil measurement loop, comprising:
• an oil separator in fluid communication with the low-pressure line, the oil separator configured to receive the refrigerant and oil flow from the low-pressure line output an oil flow and a refrigerant flow;
• an oil collector configured to receive the separated oil flow from the oil separator;
• a valve configured to control an oil flow from the oil collector to the low-pressure line;
• and
• a level sensor configured to measure oil level in the oil collector, wherein the processor is configured to:
• close, in response to the oil being at or less than a first level, the valve to collect oil in the oil collector;
• and
• open, in response to the oil being at or greater than a second level, the valve to release oil from the oil collector to the low-pressure line;
• derive an oil cycle ratio based on the flow rate from the mass flow meter, a first oil level measured from the level sensor, and a second oil level measurement measured from the level sensor.