A method for determining superheat for an air-conditioning system or a heat pump system using a virtual superheat measurement (VSM) system, the method comprising:
- providing a refrigerant;
- providing a compressor, having a compressor efficiency, configured to receive the refrigerant through a compressor inlet, to compress the refrigerant, and to discharge the refrigerant from a compressor outlet;
- providing a condenser operatively coupled to the compressor outlet via a discharge line;
- providing an evaporator operatively coupled to the condenser via a liquid line that contains a throttling device and to the compressor inlet via a suction line,
- wherein the refrigerant is capable of flowing in a closed loop from the compressor to the condenser to the evaporator and back to compressor;
- providing at least one temperature sensor configured to measure a suction temperature, a discharge temperature, and a condensing temperature in a cooling mode;
- and a suction temperature, discharge temperature, and evaporating temperature in a heating mode;
- providing storage configured to store data including the measured suction, discharge, and condensing temperatures and instructions for a processor to perform a method for calculating the a superheat or supercooling;
- providing the processor that performs the method, the processor configured to receive the measured suction, discharge, and saturated temperatures, to calculate the superheat or subcooling, and to output the calculated superheat or subcooling to an output device;
- providing the output device,
- the method in the cooling mode further comprising:
- obtaining the compressor efficiency;
- acquiring concurrent noninvasive measurements of a suction temperature, a discharge temperature, and a condensing temperature;
- determining a discharge pressure as a saturated pressure corresponding to the condensing temperature;
- determining a first discharge enthalpy and a discharge entropy, each as functions of the discharge temperature and the calculated discharge pressure;
- looping through the following steps for all possible values of suction pressure:
- guessing the suction pressure;
- determining a suction enthalpy and a suction entropy, each as functions of the guessed suction pressure and the suction temperature;
- determining a second discharge enthalpy as a function of the discharge pressure and the calculated suction entropy;
- and
- determining a second compressor efficiency as a difference between the second discharge enthalpy and the suction enthalpy divided by a difference between the first discharge enthalpy and the suction enthalpy,
- wherein the method does not acquire a concurrent measurement of a refrigerant pressure made with a pressure sensor,
- wherein the method does not include concurrent measurements on the evaporator, and
- wherein the concurrent measurements are noninvasive;
- the method in the heating mode further comprising:
- obtaining the compressor efficiency;
- acquiring concurrent noninvasive measurements of a suction temperature, a discharge temperature, and an evaporating temperature;
- determining an evaporating pressure as a saturated pressure corresponding to the evaporating temperature;
- determining a first suction enthalpy and a suction entropy, each as functions of the suction temperature and the calculated suction pressure;
- looping through the following steps for all possible values of discharge pressure:
- guessing the discharge pressure;
- determining a discharge enthalpy and a discharge entropy, each as functions of the guessed discharge pressure and the discharge temperature;
- determining a second suction enthalpy as a function of the suction pressure and the calculated discharge entropy;
- and
- determining a second compressor efficiency as a difference between the second discharge enthalpy and the suction enthalpy divided by a difference between the first discharge enthalpy and the suction enthalpy;
- wherein the method does not acquire a concurrent measurement of a refrigerant pressure made with a pressure sensor,
- wherein the method does not include concurrent measurements on the condenser, and
- wherein the concurrent measurements are noninvasive.