冷冻水泵变频频率下限分析

分析了冷冻水系统中相关设备与装置对水流量的不同要求,在考虑冷冻水管路特性、冷冻水泵及其电机与变频装置的综合效率等因素的基础上,提出了确定冷冻水泵变频频率下限或频率范围的方法与步骤。通过考察冷冻水管路阻力系数随空调负荷变化的趋势,提出了冷冻水泵“等效静扬程”的概念,指出在空调冷冻水管路中不能直接应用泵的相似定律来确定冷冻水泵变频运行的工况点或运行频率。

Analysis on the lowest frequency limit of variable frequency chilled water pump

After analyzing the various requirements of chilled water flow rate of the equipments in air-conditioning chilled water system, with consideration of the chilled water loop characteristics and the integrative efficiency of chilled water pump, pump motor and variable frequency drive (VFD), the author presents a general method to determine the lowest frequency or the operating frequency range of variable frequency chilled water pump in air-conditioning system. Meanwhile, a concept of equivalent static head is put forward on the basis of the relationship between air-conditioning (AC) loads and chilled water loop characteristics. The results show that the pump affinity laws cannot be directly used to determine the pump's operating points or the operating frequency range under the variable AC loads.