Study On Hydraulic Characteristics Of Multiple Pump Variable Flow Chilled Water System

With the rapid development of C hina's economy,the application of the large district cooling system is becoming more and more extensive,and the comp lexit y of the chilled water system is exacerbated.The chilled water system is developed from simp le single stage pump system to comp lex multistage pump system.The increase of the number and series of pumps makes it more difficult to design,operate and control the air condit ioning chilled water system.In this paper,the design and operation control strategy of the multiple pump variable flow chilled water system in a factory area is simulated and optimized,in order to get better system design method and operation strategy.First of all,the composition,energy saving potential and scope of the multip le pump variable flow chilled water system is analyzed,and the combined operation of mult istage and multip le pumps are studied in the paper.The energy saving principle of water pump frequency conversion control is analyzed,and the differentia l pressure control method with wide application and good hydraulic stability is applied to study the follow-up pump frequency conversion control.Secondly,the original design scheme of the triple pump chilled water system in a plant air conditioning system was modeled and simulated by using the Flow master software.The problem of hydraulic imbalance of the chilled water system in the plant area is found under the original design conditions.Through simulation and calculation,the equipment selection and pipeline resistance of air conditioning chilled water system in the plant are optimized and balanced,and the results of the optimized design are remodeled and simulated,the results show that the hydraulic imbalance of the chilled water system after the optimization is greatly improved,and the end user flow can meet the design requirements.Thirdly,the summer hourly cooling load in the plant area is calculated,the variation law and scope of the cooling load in the plant area in summer are obtained.The air conditioning chilled water system in plant area are analyzed in variable load simulation,and the optimal control strategy of variable load is obtained : when the secondary pump adopts pressure difference control between supply and return main pipes and the tertiary pump adopts the most disadvantage and remote circuit pressure difference control method,the hydraulic stability of the triple pump chilled water system in the plant area is the best.Finally,on the basis of the above optimal control strategy,the frequency conversion range of secondary pumps and tertiary pumps is obtained.The integrated operation strategy of variable-frequency control of the pressure difference of the p lant area chilled water system is given,the results show that the comprehensive operation strategy can save 31.5% of the electric energy compared with the traditional control strategy of the number of water pump.