Method for predicting surge in compressor

A method for predicting surge in a compressor, applicable to a cooling apparatus equipped with a centrifugal compressor, the method comprising the steps of:

• (1) obtaining a set of highest outlet pressure values by a performance test performed on the centrifugal compressor;
• (2) detecting a value of coolant flow rate and a value of opening degree of inlet guide vanes of the centrifugal compressor;
• (3) calculating an outlet pressure value of the centrifugal compressor with an equation below using the detected value of coolant flow rate and the detected value of opening degree of the inlet guide vanes, and multiplying the outlet pressure value by a corrective coefficient,
• Z=(P1X+P2Y+P3)3
• wherein X, Y and Z represent the value of opening degree of the inlet guide vanes, the value of coolant flow rate, and the outlet pressure value, respectively, and P1, P2 and P3 are known values of coefficients;
• and
• (4) determining if the outlet pressure value that is multiplied by the corrective coefficient is larger than or equal to one of the highest outlet pressure values corresponding to the value of opening degree of the inlet guide vanes detected in step (2), and confirming imminent surge in the centrifugal compressor if the outlet pressure value is larger than or equal to the corresponding one of the highest outlet pressure values, so as to provide a basis of preparation for surge elimination, and outputting a prompt to warn that surge is going to occur in the centrifugal compressor upon determination that the outlet pressure value is larger than or equal to the corresponding one of the highest outlet pressure values.