Numerical Simulation Of Natural Ventilation In Industrial Plant With Heat Source

Natural ventilation technology has several advantages besides its good ability to effectively adjust the indoor temperature,e.g.,conservation of conventional fossil fuel energy and reducing environmental pollution,improvement of the indoor air quality by introducing the fresh air in and take the indoor pollutants out,etc.The environmental quality inside an industrial workshop is required to be at a high level for high-quality product and comfortable surroundings for workers.Hence natural ventilation is used to improve the air conditioning in any industrial plants at different areas during the summer and transition season in order to save energy consumption and lower production costs.Therefore,it has become an urgent need to address the key issues on how to prepare for natural ventilation design of the plant.According to the thermal pressure principle of natural ventilation,the neutral surface,i.e.,zero pressure difference surface,should be at a lower position for reasonable design of industrial workshop because of the following two major reasons. First,the lower location of neutral surface can let the fresh air flowing into the workshop from the open air can run through all or most of the operations area,which means natural ventilation will obviously take the heat and pollutant away from the operating area to decrease the temperature and improve the air quality.Second,the vertical distance from the exhaust exit to the neutral surface will increase if the neutral surface is at a lower position,which make the pressure for discharging the old air higher and will benefit the natural ventilation effect.An increased discharge pressure will require a smaller discharge area at a given exhaust flow rate,which means the size of the top window opening may be reduced.The leading result is the cost of the workshop civil investment may be reduced.Therefore,it's interesting to make an intensive study on the influence of different parameters,such as the air inlet and outlet position and their sizes,the heat source distribution,etc,on the natural ventilation characteristics.The author carried out the numerical simulation for the natural ventilation in a typical industrial workshop with different heat sources.First of all,the natural ventilation in a plant of iron and steel company with 2 heat sources(hot steel work line) has been numerically simulated by computational fluid dynamics(CFD) method.The numerical calculation was carried out to simulate the flow and temperature field in the workshop by a realizableκ-εturbulent model combined with a discrete ordinate(DO) radiation model,which took into account the radiation between the heat source and the wall.Comparison of the numerical results and the corresponding experimental results verified the present model and numerical method to be reasonable.Further simulation was conducted to show that improvement of the heat source distribution and the workshop structure could lead to a better natural ventilation result.An important conclusion is that natural ventilation can be enhanced when the height of the exhaust exit is properly lowered and the distance between the two hot steel work line is shortened.Then the verified model and numerical method were adopted to simulate a industrial workshop with a typical geometric features for its natural ventilation.When the heat source in the plant is fixed,the numerical calculation was carried out to simulate the flow and temperature field in the plant.The effect of the building structure,such as the air inlet area and its position,the area of the rectangular skylight, the air outlet area,etc,on ventilation was calculated.The results were discussed in detail on the ventilation rate,outlet air temperature and the mean air temperature in the working area and the effective heat coefficient,etc.Finally,when the building structure parameters is fixed,the effect of the spatial distribution of the heat source was calculated.Results were discussed and analyzed for the flow and temperature field at different location,forms and the height from the ground of the heat sources.The results and conclusion drawn from this thesis for natural ventilation design of industrial plant can provide useful references for engineering application.