Methods for detecting surge in centrifugal compressors

A method for detecting surge in a centrifugal compressor having a compressor entrance in fluid communication with an evaporator, said evaporator adapted to receive a fluid refrigerant and disposed in a heat-exchange relationship with a liquid entering said evaporator at a suction entrance and flowing through a heat-exchange coil located in said evaporator, said method comprising automatically and periodically performing the steps of:

• generating a compressor-status parameter which defines an operating condition for said centrifugal compressor;
• calculating a set point parameter in accordance with said compressor-status parameter;
• positioning a first temperature sensor proximate said compressor entrance to measure a refrigerant temperature;
• positioning a second temperature sensor near said suction entrance to measure a liquid temperature;
• and
• using said liquid temperature, said refrigerant temperature and said set point temperature to detect surge.

A method for detecting surge in a centrifugal compressor having a compressor entrance fluidly connected to an evaporator, said evaporator flowing a refrigerant, said refrigerant received from a condenser and disposed in heat-exchange relationship with a liquid entering said evaporator at a suction entrance, said method comprising automatically and periodically performing the steps of:

• determining a first thermodynamic parameter at a first location within said liquid proximate said evaporator entrance;
• determining a second thermodynamic parameter at a second location within said refrigerant proximate said compressor;
• and
• detecting surge from said first and said second thermodynamic parameters by computing a value indicative of a parameter difference between said first thermodynamic parameter and said second thermodynamic parameters:
• and comparing said value to a set point parameter.

An apparatus for detecting surge in a centrifugal compressor in fluid communication with an evaporator at a compressor entrance, said evaporator flowing a refrigerant fluid in heat-exchange relationship with a liquid entering said evaporator proximate a evaporator suction entrance, said apparatus comprising:

• means for detecting a first temperature of said refrigerant proximate said compressor entrance;
• means for detecting a second temperature of said liquid proximate said evaporator suction entrance;
• means for determining a differential between said first temperature and said second temperatures;
• and
• means for detecting surge by comparing said differential to a set point parameter.

A method of detecting surge in a centrifugal compressor having an impeller and a compressor entrance in fluid communication with said impeller, said compressor entrance connected to a evaporator, said evaporator adapted to receive refrigerant from a condenser, said refrigerant disposed in heat-exchange relationship with a liquid entering said evaporator at a evaporator suction entrance and flowing within a heat-exchange coil disposed in said evaporator, the method comprising the steps of:

• monitoring a first temperature of said refrigerant before said refrigerant enters said compressor entrance;
• monitoring a second temperature of said liquid before said liquid enters said evaporator suction entrance;
• and
• detecting surge from calculations involving said first temperature, said second temperature and a set point temperature.

A method for detecting surge in a refrigeration system, said refrigeration system including a centrifugal compressor means having an impeller and a compressor entrance, an evaporator means for receiving a fluid refrigerant, a suction line for flowing said refrigerant from said evaporator means to said compressor entrance, said evaporator means including a heat-exchange coil means supplied with a liquid through a supply line entering said evaporator means, said liquid disposed in a heat-exchange relationship with said refrigerant within said evaporator means, the method comprising automatically and periodically performing the steps of:

• measuring a fluid temperature of said liquid proximate said supply line entering said evaporator means;
• measuring a refrigerant temperature of said refrigerant proximate said compressor entrance;
• using said fluid temperature and said refrigerant temperature to detect surge in said refrigeration system by periodically determining an operational condition of said centrifugal compressor means;
• and
• obtaining a parameter indicative of surge from said fluid temperature, said refrigerant temperature and said operational condition.