2.6 气流原理 Air current principle

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理解气流流动的原理,可有效地指导气味控制的策略。主要有三个比较重要的概念: Understanding the principle of air current can guide us to make right strategies for odor control.

 

对流层原理 Troposphere principle:

对流层是地球大气层最低层。空气混合均匀,温度随高度上升而降低,因为阳光照射地面和地面热辐射的作用,使地表空气加热比高空空气快,地表被加热的空气受热膨胀,比重减轻而向高空上浮,使热量在对流层传播。高空的冷空气,由于密度变大而重下沉,这样就形成了气流(风)The troposphere is the lowest layer of the Earth's atmosphere. The air is very well mixed and the temperature decreases with altitude because the air in the troposphere is heated from the ground up due to thermal radiation to make the surface of the Earth absorbs energy and heats up faster than the air does. The heat is spread through the troposphere because the warmer air close to ground is slightly unstable and becomes updraft and colder air in higher attitude becomes downdraft due to the higher density. The updraft and downdraft, therefore, form “Air current” (wind).

在垃圾场,由于垃圾内部的无氧生物活动会产生大量的热量,致使垃圾表面的温度往往高于周边的地区,所以在垃圾上空总是会形成一个向上的气流,把垃圾产生的气味不断地推向高空,并在上升的同时在高空的较强的风力作用下进行水平移动和不断冷却,当上升到一定的高度,这些有气味的空气得到足够的冷却后开始下沉,这些气味重新被带回地面,这就是为什么,常常在垃圾场周边没有气味而几里外的地方气味浓厚。(下图中,红色箭头是热的上升的气流,篮色代表冷的下降的气流). In landfills, the heat produced by anaerobic biologic activities makes the temperature on landfill surface always higher than the surround area and creates an updraft of warmer air on the landfill surface bringing odor into higher attitude where the air become cold and start to form a downdraft bringing odor back to ground surface. This is why people can’t smell the odor around the landfill, whereas, the odor attacks the people who live several miles away from the landfill.

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