Energy Saving Study and Analysis of Variable Frequency Screw Chiller Type Cold and Hot Water Unit
Variable frequency screw chiller type cold and hot water unit has excellent cooling and heating effect,and can meet a wide range of partial load requirements.In this paper,the system principle,component selection,control strategy,operation characteristics and economy of such units are studied,conclusions and suggestions are given.According to the developed unit,coefficient of performance(COP)under variable frequency is larger than COP under constant frequency under various partial load conditions,and increases by 2%-15%,especially COPC under refrigeration conditions.Variable frequency control makes the unit performance better under low load rate.In variable frequency and constant frequency operation,for Integrated Part Load Value(cold)-IPLVc of refrigeration condition and Integrated Part Load Value(heat)-IPLVh of heating condition,variable frequency IPLVc is significantly higher than constant frequency IPLVc,with an increase of 6.95%,variable frequency IPLVh is higher than constant frequency IPLVh,with an increase of 3.55%.Variable frequency control makes the comprehensive energy efficiency coefficient of the unit higher.When the unit runs with variable frequency,it can reduce electric energy consumption,save operation cost and reduce carbon dioxide emission every year.
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