CFD Research Of The Light-Pipe System With The Function Of Natural Ventilation

Light-pipe system which combines natural lighting and natural ventilation can realize green lighting and natural ventilation at the same time. It can reduce underground or shade buildings'illumination and ventilation energy consumption effectively .This technology is fully in the person of energy-saving of architecture.The light-pipe system which is designed in this paper is composed by two concentric tubes. The inner one pasted by high reflectivity membrane is used for lighting . Through total reflection it can guide the natural lighting into the office. And the gap between the inner pipe and the outer pipe is used for ventilation which can guide the exhaust air out of the office by stack effect and wind effect. In order to improve the ventilation, Numerical simulation is used for analyzing the ventilated effect in order to offer the foundation for the actual application.From analyze the influence factors of the ventilation, it was found that H-type is the best ventilation terminal. It has the least ventilated quantity when the ratio between length and gap of the ventilated tube equals to 41.67, so it has to avoid this extremum. The ventilated quantity increases with the enlargement of the radius of the light pipe .From analyze the inlet area, height and the height of heat source when the light-pipe system who has the best structure is used in underground buildings. It was found that when the area ratio between inlet and outlet is less than 1.13, the cost of windows can be reduced effectively and that the ventilated quantity won't be reduced. The inlet should be located between the bottom and heat source. Both of the indoor air quality and energy saving can be realized. The height of heat source has great effect on the indoor temperature. The temperature efficiency will be the largest when t the height of heat source is larger. But the ventilated quantity won't change much.In shade rooms, under the function of the stack effect and wind effect, it was found that wind effect is the primary driver to indoor ventilation when the out wind is greater. And the wind pressure coefficient will be difference along with the height of inlet. The indoor effect of ventilation will has great difference when inlet is located on windward wall or leeward wall. In summer the inlet should be located on the bottom or near the upper of the wall. Here it can got the largest ventilated quantity. And in winter, in order to reduce the dissipation of the heat, the inlet should be located on the upper zone of the leeward wall.