制冷与空调专业英语第2版 林慧珠 主编 1-1新.pptVIP

Unit One Lesson 1 Air Lesson 2 The Need of Conditioning Lesson 3 The Cleaning of Air Lesson 4 Thermal Storage Lesson 1 Air New Words Expressions: Text Notes to the Text Exercise Lesson 1 Lesson 1 New Words Expressions: Text Air is a mixture, not a compound. It is essentially composed of nitrogen, oxygen, and argon with small amounts of water vapor, carbon dioxide, and dust. Air can be liquefied and separated into its constituents by letting the more volatile nitrogen to boil off first. Text: There is a definite temperature below which a gas must be cooled before it can be liquefied.1 This is known as the critical temperature, and it is different for different gases. The critical temperatures of both oxygen and nitrogen are so low that it is impossible to liquefy these gases at ordinary temperatures however much we compress them.2 To liquefy air we must cool it to a very low temperature as well as subject it to a high pressure.3. Text: 液化空气是液态氮和液态氧的混合物。可以把较轻的氮从氧中分离出来。用这种方法可以生产工业用氧，并将其装入氧气钢罐。氮气也可以用同样的方法生产。 Text Nitrogen is an inert substance. It is a colourless, odourless, tasteless gas; does not burn; does not support combustion or respiration; is not poisonous. It does not easily unite directly with other elements. 4 At high temperatures it combines with a few metals, such as magnesium, and also with oxygen and hydrogen. Oxygen is also a colourless, odourless gas. It is somewhat heavier than air. It is the most active element in the atmosphere. It is essential to life. Argon is present in air to the extent of nearly one percent by volume. Text Carbon dioxide is introduced into the air by combustion and respiration. It is removed by green plants, which get all their carbon from the carbon dioxide in the air and produce oxygen. The balance of plant and animal life keeps the amounts of oxygen and carbon dioxide in the air constant.5 The chief factors in the air which affect human comforts