Design For Circulating Water Monitoring System Based On ZigBee Network

This paper takes the circulating water system of a factory as the research object and designs a circulating cooling water monitoring system based on ZigBee wireless sensor network.A two-variable trial-and-error algorithm for calculating mass flow rate and outlet temperature of heat exchanger in cooling circulating water system is proposed.The algorithm establishes a constrained mathematical model of heat exchanger with the outlet temperature of cold and hot fluids as constraints.The algorithm chooses two variables of mass flow and temperature of cold fluids,and substitutes these two variables into heat balance equation and heat transfer equation of heat exchanger to carry out bivariate trial and error operation.In this way,the monitoring system can obtain real-time mass flow rate of cooling water,which can make the outlet temperature of hot fluid meet the set requirements,and can guarantee the outlet temperature of cold fluid to meet the restrictive conditions.The design of cooling water quantity of circulating water system based on single v ariable trial-and-error method will lead to unreasonable pump configuration and can not guarantee cooling effect.The algorithm can solve this problem.The calculation results of an example verify the validity and application value of the algorithm.This paper presents an algorithm for pump station allocation of circulating water system based on flow continuity control condition and maximum flow control condition.Then,a scheduling strategy based on energy efficiency optimization is proposed.According to the two-variable trial-and-error method,the strategy calculates the cooling water flow and chooses the operation mode of parallel pumps with higher total efficiency,and then changes the number of pumps in real time to adjust the working frequency of variable speed pumps,which can realize efficient,stable and economical water supply for pumping stations.Pump control module,data acquisition module and wireless network coordinator are designed.These modules possess ZigBee wireless function.The wireless network is established by ZigBee wireless coordinator,which communicates with data acquisition module to collect flow,pressure and temperature information in circulating water system.The host of the system calculates the cooling water flow by real-time operation of the two-variable trial-and-error method,and runs the optimal dispatching strategy of the pumping station.The dispatching strategy is sent to the pump control module through the coordinator to achieve the rational allocation of the number of pumps starting and stopping,and to adjust the working frequency of the variable-speed pump,thus completing the wireless monitoring of the circulating cooling water system and realizing the relevant chemical process control requirements.The circuit design and program design of wireless coordinator,control module and data acquisition module are given.The main program and configuration interface of the system are designed.The control system is simulated and verified on the platform of Matlab.