Analysis of cooling water pump working zone and variable frequency operation of one-pump-one-chiller combination

Based on Qianhai DCS Plant No.10 in Shenzhen, a hydraulic calculation model is developed for the one-pump-one-chiller combination cooling water systems considering the shared pressure drops of the shared main pipe and cooling towers, and the individual pressure drops of the pump branches. According to different operation modes, the pump working zones are obtained. Combined with the frequency conversion characteristic curve of the pump, the pump frequency operation zone is obtained corresponding to different flows in each pump working zone, which can be used for the frequency conversion control of the pump, and the pump operation control strategy is simplified. The pump working zone proposed in this paper can also be used for pump selection to check whether the pump is running in the high efficiency zone under all the operation conditions.