Large-scale water chiller operates under partial load at most of the time

studying the law of compressor energy efficiency ratio(EER) varying with load ratio can provide fundamental basis for the chiller running in high efficiency that.The mathematical model to determine EER

evaporating temperature and condensing temperature of single water chiller was proposed in this paper.Under the uniform load distribution condition

the mathematical model of EER with multiple same type units but different parallel operation modes was established according to different ways of bearing partial load

the operating characteristic of units were also analyzed.The results showed that the centrifugal water chiller can maintain higher EER only at 70%-100% load ratio

EER decreases sharply with the decrease of load ratio

the units' operation is controlled by single unit's load rating according to total load reduction

which can keep the total EER at high level within a wide load range.