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Cycling Losses During Screw Air Compressor Operation
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Air compressors use 10-13 % of a typical industrial facilities' total electricity. Because they often operate at part load, their part load efficiency significantly affects plant energy cost. An intensive study of screw air compressor part load efficiency confirmed that modulation only controls are accurately portrayed by traditional part load models under most conditions. It also confirmed that load-unload type controls are accurately modeled when cycle times are longer than 5 minutes. However, the study revealed compressors with cycling controls require as much as 10-25 % more power than is normally assumed when cycle times decrease below 2 minutes. This short cycle time is common in industrial environments. The study also found that combined modulating and unloading controls operate the compressor as much as 20% more efficiently than previously predicted. Several measures are recommended for improving part load efficiency by up to 25 %: • Increase receiver capacity • Install load-unload controls • Maintain compressor controls • Set higher low-unloading setpoints.
Maxwell, J. B.; Wheeler, G.; Bushnell, D. (1995). Cycling Losses During Screw Air Compressor Operation. Energy Systems Laboratory (http://esl.tamu.edu). Available electronically from