Study On Variable-air-volume Air-conditioning System

In this dissertation an office building variable air volume system performance was analyzed in the view of energy efficiency and system control. The annual cooling loads and control performance with different duct static pressure control were predicted and tested. And the main content are as following.Research of an office building annual cooling loads:The multi-zone cooling loads and changing with the time were presented and compared. The results indicated that the hourly cooling loads difference between zones was great which makes important to divide different zones in the VAV air- conditioning system design.Modeling of VAV air-conditioning system with different control method:A simulation program of VAV air-conditioning including duct networks, VAV boxes, fan components was presented which could be generally used to predict the system control performance and fan power under the consideration of annual cooling loads. The building thermal networks analytical theory and conduction transfer function were introduced to deduce the formula of thermal admittance for building enclosure which was added to the zone model for HVAC system simulation. Two kinds static pressure control method were presented. The zone temperature, humidity and fan power were predicted. The results showed that fan energy use reduced 50.5% in winter and 8% in summer when duct static pressure reset control was compared with constant static pressure control.Analysis of system performance with different duct layouts:The system performance and zone air temperature of three kind layouts with DSPR control were presented by simulation. The comparison of predictions indicated that the layout of the air duct might influences the fan control result and energy savings. Experimental research of VAV air-conditioning system :The experimental data were achieved from a trial implementation of the DSPR control and constant duct static pressure control method in an existing office building in Hong Kong. The energy efficiency with DSPR control was reported and the reasons affect successful application of the control method were also proposed. The performance data comparison shows the accuracy of simulation program.