Simulation On Control Method Of Air Pressure And Air Flow Rate For Variable Air Volume Air-Conditioning System

Along with the arising of intelligent buildings, more requirements for comfort air-conditioning are advanced to meet people's need and the variable air volume (VAV) air-conditioning system comes into being. In order to research the VAV air conditioning system and study the intelligent control of it, the laboratory of VAV system has been designed and built in our university, based on the software and hardware of the METASYS offered by Johnson Controls.Temperature of supply air can be controlled automatically by changing the flow rate of chilled water of the cooling coil section in the air handling unit. Through changing the rotational speed of supply fan, the static pressure of the measuring points can be maintained in the stability setting value. The sensor of VAV box can change the butterfly damper of the terminal. By adjusting the butterfly damper of the terminal, the supply air volume of the terminal can be determined. At the same time room temperature is maintained in the scope. The VAV experiment system is connected with temperature controller and static pressure controller. The network controller unit can be used to compile programs that control the operation of DDC controllers and keep watch on the equipment.As the total supply air volume of VAV air conditioning system is decided by the sum of supply air volumes of total rooms, the fan volume control has three methods: constant static pressure control, variable static pressure and total air volume control. In this dissertation the control performance with different control are predicted and tested. Based on the HVACSIM+ software the components' mathematic models and the system's emulational models are set up. The cooling loads of the controlled room which are changing with the time are added to the VAV system simulation model. Two kinds control method are simulated. The room temperature and fan power are predicted. The results showed that fan energy use reduced more when total air volume control was compared with constant static pressure control.