大学英语四级（仔细阅读）专项练习试卷2 (题后含答案及解析)
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The days, many large city buildings are equipped with their own air-conditioning systems. The systems help keep the buildings cool, but they can also damage the environment. Since they u a lot of electricity, for instance, they contribute indirectly to global warming. In addition, the water that flows through the systems is often cooled using chemicals called chlorofluorocarbons, or CFCs, that are believed to damage the Earth’ s ozone layer. Recently, though, a system has been built in the city of Toronto, Canada, that cools buildings with little damage to the environment. In the traditional air-conditioning systems found in most large buildings, water is pumped through the building in a continuous cycle. The water is first cooled to a temperature of 4°C in machines called chillers. It is then nt to individual units that cool the air in each room. As the water flows through the building, it gradually becomes warmer. Finally, it reaches the roof, where it is left to cool down naturally in a water tower. After that it is returned to the chillers, where the
cycle begins again. Toronto lies on the shore of Lake Ontario, one of North America房屋租赁公司雅俗共赏歌词’唐朝年号s Great Lakes, and the new system makes u of cold water taken from about 80 meters below the surface of the lake. At this depth, the water in the lake remains at 4°C all year round. This is exactly the temperature to which the water in air-conditioning systems is cooled. However, the water from the lake is not pumped directly into the air-conditioning systems. Instead, it is ud to cool the water that is already inside the air-conditioning systems. After that, the lake water is added to the city’中国石拱桥课文痛彻心扉是什么意思>梦见别人打蛇s ordinary water supply. Enwave, the company that developed this deep-lake cooling system, says that it us 75 percent less energy than traditional air conditioning. And since no CFCs are ud, no damage can be caud to the ozone layer. Not every city is located next to a large lake, but experts believe that systems like the one being ud in Toronto could be built elwhere by using other natural sources of cold water.
