6. Decide which statements are true and which ones are false.

1. An early method of cooling air as practiced in India was to hang cotton mats over windows where they cooled incoming air by evaporation.

2. The development of highly–efficient refrigerant gases of high toxicity known as Freons was an important step.

3. The refrigerant evaporates and, in the process, dissipate the heat contained in the air.

4. The cold and dehumidified air is returned into the room by means of a blower.

5. In some units the two sets of coils can reverse functions so that in winter, the inside coils condense the refrigerant and cool rather than heat the room.

6. In some large factories a version of the earlier air–washer systems is still used to avoid a great number of coils needed otherwise.

7. Complete the following sentences by adding the phrases given in part b.

Part A

1. Carrier also devised a system…

2. When the cooled air reaches its saturation point…

3. Under these conditions the refrigerant condenses back into a liquid form…

4. Dehumidification is achieved in some systems by passing the air through silica gel …

5. In the dual–duct system, warm air and cool air travel through separate ducts and …

Part B

A. …and gives off the heat it absorbed inside.

B. …which absorbs the moisture, and in others, liquid absorbents cause dehydration.

C. …wherein conditioned air was fed from the ceiling and exhausted at floor level.

D. …are mixed to reach a desired temperature.

E. …its moisture content condenses on fins placed over the coils.

8. Answer the questions on the text.

1. What does the term “air–conditioning” mean?

2. When did modern air–conditioning have its beginning?

3. Who devised the “dew point control”?

4. What gases are known as Freons?

5. What is the main principle of air conditioner operation?

6 Alternate systems of cooling include the use of chilled water, don`t they?

7. What is dehumidification achieved by?

8. What systems are still in use in some large factories to avoid the massive amount of coils?

9. What does the design of air conditioning systems depend on?

Language Focus

9. Memorize the following pairs of derivatives, paying attention to the meaning of the prefixes.

purity – impurity	regular – irregular
efficient – inefficient	turn – return
dependent – independent	circulate – recirculate
directly – indirectly	use – reuse
variable – invariable	include – exclude
known – unknown	hydration – dehydration
important – unimportant	humidification – dehumidification
purified – unpurified	inside – outside

10. Transform as in the models.

Model 1 «Verb – Noun»: to evaporate water – evaporation of water

to use chilled water, to move air, to control temperature, to develop refrigerant gases, to absorb heat, to condense the refrigerant, to recirculate liquid

Model 2 «Noun – Noun»: evaporation of water – water evaporation