Optimizing Control Of The Cooling Tower Subsystem In The Heating Ventilating And Air-Conditioning System Based On Lonworks Technology

In the heating ventilating and air-conditioning system(HVAC),the energy consumption of the water-loop sub-system,which consists of cooling towers and chiller plants,is about 55 percent of that of the whole system,and the energy consumption of the cooling towers is about 15 percent of whole systems'.At present,the air-conditioning cooling tower system design is based on the most adverse working conditions throughout the year.So that how to improve their working conditions and saving the energy have great significance.In general,the design of the HVAC system is under the assumption that the system is working on the largest loads,however in fact the HVAC system is usually run on a part of loads.If the optimum work point of the HVAC system could be found by certain methods and the energy matching of different devices in the system could be adjusted by control systems,the energy consumption of the system would be greatly reduced.In this thesis,by analyzing the operation process of air conditioning water system and the power consumption characteristics of cooling tower system,we present an online optimization of set-point for cooling tower system of HVAC to make cooling tower system of HVAC can realize the best operation and reduce energy consumption. According to heat exchange characteristics of central air-conditioning cooling tower system and the traditional principle of thermodynamics,this thesis presents a relatively simple model of equation for heat exchange.To identify the unknown parameters of heat exchange model several different numerical methods are used。The parameters calculated by the Levin Berger - Ma quart method can more accurately reflect the thermal model for cooling tower.Based on this we presents a optimizing control method for cooling tower system,and it makes the total energy consumption of the central air-conditioning cooling tower water systems and refrigerator system of coordination minimize,while the SUMT method is used to solve the optimal operating point between the cooling tower fan and water pump.We also resolve the coordination problem between cooling tower subsystem and chiller subsystem of HVAC water system by visiting a table established by interpolating to data of optimizing work point.The simulation results based on experiment data verifies the validity of the methods proposed and program in this thesis.