US Patent 7841825 Method for predicting surge in compressor

A method for predicting surge in a compressor is provided, which is applicable to a cooling apparatus equipped with a centrifugal compressor. A set of highest outlet pressure values is obtained by a performance test performed on the centrifugal compressor. A coolant flow rate value and an opening percentage value of inlet guide vanes of the centrifugal compressor are measured. An outlet pressure value of the centrifugal compressor is calculated with an equation using the measured coolant flow rate value and the measured opening percentage value. The outlet pressure value is compared with one of the highest outlet pressure values corresponding to the measured opening percentage value, and if the outlet pressure value is larger than or equal to the highest corresponding outlet pressure value, it confirms imminent surge in the centrifugal compressor, so as to provide a basis of preparation for surge elimination.