Pmv Index-based Air-conditioning System, Comfort Control Study

In a conventional HVAC control system, only air temperature and air humidity are controlled. As we all know, occupants' thermal sense is mainly dependent on the six factors: inside air temperature, humidity, air velocity, mean radiant temperature, clothing and metabolism rate. The traditional HVAC control system, neglecting other factors concerned with human comfort, only considering the inside air temperature and air humidity and indirectly impacting on occupants by the two parameters control, cannot satisfy the comfort requirement of occupants and is energy wasting as well. On the basis of the study on the thermal comfort theory and thermal comfort index, the so-called comfort index control(CI control) is defined as the control of HVAC system, which takes thermal comfort index as the control parameter. So if we convert the simple inside air temperature and humidity control into the thermal comfort index such as PMV as the control target in the HVAC control system which evaluates the synthetic effects of the thermal environment on human bodies, therefore, the HVAC system control will change with the human sense, which will bring us a real "comfortable" HVAC system.PMV is the optimal choice of CI control, as it successfully related all the environmental variables with a person's thermal sense. Furthermore it has received comprehensive application in thermal environment engineering. For this reason this paper chooses the PMV index as the research object in the comfort control, and analysis of the influence to PMV index as the environmental variables change. In order to compare the two control strategies, a thermal energy model is established to undergo dynamic analysis to the thermal environment of the room. The result shows that comfort index control not only meet the thermal comfort requirement of human bodies, but also has large energy saving potential. An environmental variables optimization model is also established to optimize the environmental variables. The result shows that energy saving is obvious after optimization on the basis of the equal comfort lever.The research of PMV comfort control strategy is the key problem in realizing comfort control. Different control strategies will produce different comfort and energy saving. In general, there are two different control strategies in comfort control as follows: Direct method and indirect method. In HVAC system, the control is ofcomplicacy, nonlinear, lagging and all kinds of interrupting factors, resulting in the traditional control method based on the precise mathematics model cannot reach the satisfactory dynamic-static effect. But the intelligent control offers a new way for the HVAC system control. The fuzzy logic control is an artificial intelligent method in the intelligent control. Simulation showed that this method has satisfactory dynamic-static effect.