Cooling water (CW) system with strong nonlinear characteristics is a critical component of central air conditioning systems. Further, variable flow control of CW pumps is a critical measure for achieving energy-saving operation of CW systems. Proportional–integral (PI) control algorithm is widely used in the variable flow control of CW systems, and fuzzy control algorithm also plays a significant role in these systems. In this study, the application of fuzzy control and PI control algorithms is experimentally studied in a CW constant temperature difference system. The results indicate that the PI control algorithm of the CW system is simple in structure, and it only requires a reasonable PI parameter setting to achieve better control effect with high accuracy, good steady-state performance, and low energy consumption. However, the PI control algorithm is not adaptive for different working conditions. The fuzzy control algorithm has better dynamic performance and the adjustment curve is smooth with small fluctuations, although its control accuracy is not high. Over the same test period, the regulation frequency of the water pump under PI control algorithm is higher than that of the fuzzy control algorithm, and the CW system exhibits better stability under the fuzzy control algorithm.

具有强大的非线性特性的冷却水（CW）系统是中央空调系统的关键组成部分。此外，CW泵的可变流量控制是实现CW系统节能运行的关键措施。比例积分（PI）控制算法被广泛应用于连续波系统的变流量控制中，模糊控制算法在这些系统中也起着重要的作用。在这项研究中，在CW恒温温差系统中对模糊控制和PI控制算法的应用进行了实验研究。结果表明，连续波系统的PI控制算法结构简单，只需要合理的PI参数设置，即可达到较好的控制效果，且精度高，稳态性能好，能耗低。然而，PI控制算法不适用于不同的工作条件。尽管控制精度不高，但模糊控制算法具有较好的动态性能，调整曲线平滑，波动小。在相同的测试周期内，PI控制算法下水泵的调节频率高于模糊控制算法，并且在模糊控制算法下，连续水系统表现出更好的稳定性。