| After the oil crisis emerged in the1970s, the world came to realize theimportance of energy conservation and began to pay increasing attention to thedevelopment and the utilization of energy saving technologies in various fields. Givenhigh energy efficiency, pleasant thermal comfort and high air cleanliness, VAV systemdraws the attention of researchers of HVAC ever since.There are two main control schmems widely applied in VAV system. They areconstant static pressure control and static pressure reset control. Compared to constantstatic pressure control, the character of static pressure reset control is that it can resetthe pressure setpoint real time according to the changeable indoor cooling load. Thatis the reason that it can save the energy consumption of AHU fan efficiently. Giventhe problem caused by the popular scheme widely used now, which tends to causeover cooling or over heating in certain areas, this paper proposes a new scheme,which consists of two modules, static pressure reset control and supply airtemperature reset control. The scheme was realized in the HVAC system of a realoffice building located in Hongkong island by coded in VB language.In order to compare the operation impacts of optimal scheme and original scheme,the methods of experiment and simulation were both empolyed.(1) Simulative research. The VAV system of the typical floor was simplified.Mathmetical models of fan, duct and valves were established, with FORTRAN tocreat those modules. TRNSYS was used to establish the model of VAV system, whichwas certified by experimental data. Typical days in winter, summer and transitionseason were selected to calculate the energy consumption of AHU fan before and afteroptimazation. Results suggest that the optimal control scheme used in this paperreduces the AHU fan energy consumption efficiently, especially in test days of winterand transition season. The energy saving ratio reach19.38%and15.58%,respectively.(2) Experimental research. The VAV system of the typical floor were tested withtwo schemes, respectively. Operational conditions in typical days, typical months andtypical years are compared. Coefficient of transformation was introduced to evaluatethe impact of energy conservation. ADPI was adopted to evaluate the indoor thermalcomfort. Results show that the energy conservation impact of optimal scheme is more apparent than original scheme under part load situation. The saving ratio of the wholebuilding reached7.14%in a typical year. The indoor thermal comfort was improvedapparently when the optimal scheme was adopted.Both results of simulative research and experimental research prove that theoperational condition of the optimal scheme proposed in this paper accords withrequirements. It can be applied to the VAV system of actual buildings, which can notonly save the energy consumption of AHU fan efficiently, but also improve indoorthermal comfort. |
