Influencing Factors On Thermal Natural Ventilation In Room

The two topics on sustainable development of building are energy-saving and indoor air quality.Natural ventilation is an important technology to make building develope sustainably. The driving force on natural ventilation can be divided into wind pressure and thermal pressure.Because the outdoor wind pressure is unstable,the current design criterion only considers thermal natural ventilation.Therefore,the investigation of the nature of thermal natural ventilation in naturally ventilated building is very important for the design and control of natural ventilation systems,and the better use of natural ventilation technology.The indoor air temperature distributes in layers obviously in naturally ventilated room driven by thermal pressure.Therefore,some anterior scholars put forward the concept about the effectual thermal coefficient m.The value of m represents how much quantity of heat shares the total remaining heat quantity in the whole room,and the parameter of m is very significant for the design of national ventilation systems.m parameter can reflect synthetically the air temperature distribution in hot room,and confirming the value of m is a very complex lesson.In the current design criterion on heating and ventilation,the values of m used for the design of natural ventilated industry factories are presented by adapting the result which some former Soviet scholars gained by model experiments.But the values of m are still treated in further study for public buildings which have smaller heat power and are lower than industry factory.In this paper ,the writer regarded the public building as the study object,established the physical model of the thermal natural ventilationed room, choosed the appropriate mathematical model,and had much CFD simulation by CFD software FLUENT6.1. The paper considered all kinds of influencing factors for the indoor air temperature distribuation, and had a lot of numerical computation in order to find out the main influencing factors and influencing natures on thermal natural ventilation.In CFD simulation,the writer studied how such factors ,as heat power,the area of heat source,the height of heat source,the distance of two heat sources ,the distance of the center of ventilation inlet and the center of the ventilation outlet,the area of ventilation inlet,the distribution style of outlet,and the height of room,influence thermal ventilation,analysed the influencing nature of fluid field, velocity field, temperature field of ventilated room when these factors changed. In addition,both the values and the varying natures of the quantity of naturalventilation, the difference in temperature of entering air and venting air,the effectual thermal coefficient and the height of neutralizing surface are given.These results provided theory gist for the design of public buildings' thermal natural ventilation system.