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The basic cycle1.doc
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1 Match the key words with their translations.

Повреждение, пар, термоэлектрический привод, смесь, испаритель непосредственного охлаждения, терморегулирующий, шаговый электродвигатель, перегретый, импульс- ный электродвигатель, гидравлический удар.

2. Write your ideas of what you would like to know about a direct expansion evaporator.

3. Read the text and say if you have found the answer. A direct expansion evaporator.

All the mixture enters the evaporator, the liquid part evaporates and a pure vapour leaves the evaporator and enters the compressor. To ensure that no liquid droplets the compressor, where they could cause liquid hammering and damage, the vapour has to be somewhat superheated. The superheat is also an excellent variable for control of the expansion valve.

Of special importance is the thermostatic expansion valve, which is controlled by the vapour superheat from the evaporator. This is of prime importance for the function of a direct expansion evaporator.

The electronic expansion valve is increasingly common. The advantages, flexible control parameters and remote control, make it is very popular in supermarkets with numerous air conditioning units and refrigeration duties at different temperature levels. The most reliable valves are equipped with a heat motor, but pulse modulated and step motors are also used.

4. Fill the gaps with the necessary words.

1 All the mixture___________ the evaporator.

2 A pure vapour ________ the evaporator and _______the compressor.

3 If liquid gets the compressor, it can cause_______________.

4 The______________is increasingly common.

5. Read the text again and answer the questions.

1 Where does all the mixture enter?

2 How does the refrigerant leave the evaporator?

3 What can a drop of liquid cause in compressor?

4 Why has the vapour to be superheated?

5 What is superheated also used for?

6 Why is the thermostatic valve of special importance?

7 What are the advantages of the electronic valve?

8 What are the most reliable valves equipped with?

6. Read and translate the text from ex.3.

5

7. Write the questions to the sentence

1In a flooded evaporator the expansion of the refrigerant is seldom controlled by the superheat as in the direct expansion evaporator.

2 When the saturated mixture rises through the evaporator, the pressure decrease.

Vocabulary.

direct – прямой, непосредственный,

pure - чистый,

droplet – капать (здесь)

cause – являться причиной

liquid hammering- гидравлический удар

damage - повреждение

superheated - перегрев

the vapour has to be superheated - пар перегревают

thermostatic - терморегулирующий

mixture- смесь

advantage- преимущество

reliable- надежный

pulse modulated motor- импульсный электродвигатель

a step motor – шаговый электродвигатель

heat motor – термоэлектрический привод

to equip-оснащать

saturated- насыщенный

flooded- утопленный

pressure- давление

6

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