Урок 3.7

Упражнение 1. Прочитайте слова.

[i] e'xpansion; е'vaporators; ex'changer; e'ffect; e'lectrical; elect'ricity; e'xcept; ex'tract (v.); rec'iprocating; degree; ref 'rigerant.

Упражнение 2. Сопоставьте слово с переводом и соответствующей ему транскрипцией.

1) evaporator; 2) medium; 3) vaporization; 4) reciprocating; 5) cylinder; 6) coil;

1) ['ÅJdIqÅ]; 2) ["ÈÂip(¶)Ïai'zÂi¿(Â)Í]; 3) [i'È∙p¶ÏÂitq]; 4) ['ÉIÎIndq]; 5) [ÏI'sIÃÏqÐÂIËIN]; 6) ['иIl];

1) поршневой; 2) испаритель; 3) испарение; 4) среда (вещество); 5) змеевик; 6) цилиндр.

Текст А

Evaporators and Compressors

An evaporator is a heat exchanger in which the liquid refrigerant is vaporized and extracts heat from the surrounding air, chilled water, brine, or other substance to produce a refrigeration effect. Evaporators used in air-conditioning can be classified according to the combination of the medium to be cooled and the type of refrigerant feed; broadly 2 types are used in comfort applications:

Direct expansion coils are air coolers, and the refrigerant is fed according to its degree of superheat after vaporization.

Flooded shell-and-tube liquid coolers is similar in construction to a shell-and-tube water-cooled condenser, except that it’s liquid refrigeration inlet is at the bottom and the vapor outlet is at the top. Water velocity inside the copper tubes is usually between 4 and 12 ft/sec and the water-side pressure drop is normally below 10 psig. Flooded liquid coolers can provide larger evaporating surface area and need minimal space. They are widely used in large central air-conditioning systems.

The compressor compresses the refrigerant gas, causing it to become much warmer than the outside air. The refrigerant enters the compressor on the "suction side" and after it leaves the compressor, the refrigerant is referred to as "hot gas”. Four types of electrical chillers (Figure 3.14) dominate the market: reciprocating compressors, scroll compressors, screw compressors, centrifugal compressors. Reciprocating compressors are driven by a motor and use pistons, cylinders and valves to compress the refrigerant. Scroll compressors feature two involute scrolls, one stationary and one orbiting around the first. Power input to the scroll compressor is about 5 to 10% less than to the reciprocating compressor. A scroll compressor also operates more smoothly and is quieter. Screw compressors are based on a mechanism made up of two threaded rotors (screws) that are coupled together. Twin-screw compressors are more efficient than reciprocating compressors. Centrifugal compressors are made up of a rotor located inside a special chamber. The characteristics of a centrifugal compressor make it ideal for air conditioning applications because it is suitable for variable loads, has few moving parts, and is economical to operate. They are the most widely used refrigeration compressors in large air-conditioning systems but are used only in water cooled configurations due to lower compression ratios.

Notes:

psig (pounds per square inch gauged) фунт на квадратный дюйм индикаторный.

Figure 3.14 Ciller system.

Ответьте на вопросы к тексту:

1. What is an evaporator?

2. How can evaporators used in air-conditioning be classified?

3. What is the difference between flooded shell-and-tube liquid coolers and shell-and-tube water-cooled condenser?

4. How does the compressor work?

5. What types of electrical chillers do dominate the market?

6. What are reciprocating compressors driven by?

7. How does a scroll compressor operate?

8. What are screw compressors based on?

9. What are the centrifugal compressors made up of?

10. Why is the centrifugal compressor ideal for air conditioning applications?

11. Why are the centrifugal compressors used only in water cooled configurations?

Упражнение 3. Переведите слова и словосочетания на русский язык.

Vaporize (v.); extract (v.); surrounding air; brine (n.); substance; classify (v.); according to; combination (n.); medium (n.); refrigerant feed; broadly (adv.); application; coil (n.); superheat (n.); vaporization (n.); flooded shell-and-tube liquid cooler; construction (n.); shell-and-tube water-cooled condenser; except (v.); liquid refrigeration inlet; bottom (n.); vapor outlet; top (n.); water velocity; inside; below; flooded liquid cooler; provide (v.); evaporating surface area; central air-conditioning systems; refrigerant gas, cause (v.); outside air; suction side; electrical chiller; dominate (v.); reciprocating compressor; scroll compressor; screw compressor; centrifugal compressor; drive by (v.); motor (n.); piston (n.); cylinder (n.); valve (n.); feature (n.); involute scroll; stationary; orbiting; power input; operate (v.); smoothly; base on (v.); threaded rotor; couple together; chamber (n.); compression ratio.

Упражнение 4.Переведите слова и словосочетания на английский язык.

Газообразный хладагент; сторона пониженного давления, сторона всасывания; поршневой компрессор; спиральный компрессор; винтовой компрессор; центробежный (ротационный) компрессор; скрученный, закрученный; спираль; потребляемая мощность; нарезной ротор(винт); соединять, связывать; коэффициент сжатия (уплотнения); охлаждающий раствор солей; перегрев, избыточное тепло; змеевик непосредственного охлаждения; окружающий воздух; затопленный кожухотрубный жидкостный охладитель; область парообразующей поверхности; центральная система кондиционирования воздуха.

Упражнение 5. Сопоставьте слово (A) с его определением (B).

(А)

1. refrigerant;

2. evaporator;

3. cooler;

4. compressor;

5. condenser;

6. scroll;

7. screw;

(В)

1. an apparatus or container for condensing vapour;

2. a machine used to supply air or other gas at increased pressure;

3. a device used to turn the liquid form of a chemical into its gaseous form;

4. a thin pointed piece of metal that you push and turn in order to fasten pieces of metal or wood together;

5. a substance used for refrigeration;

6. a machine for cooling something;

7. a design shaped like a piece of rolled up paper.

Упражнение 6. Переведите предложения и определите функцию причастия I и II (Participle I & II), обратите внимание на независимый причастный оборот.

1. Local systems may be totally shut off in the unused spaces providing potential energy savings.

2. Serving only a single zone, local heating systems have only one point of control.

3. Employees found under the influence of alcohol will be immediately removed from the job site.

4. Heat transfer oils used in liquid systems offer freeze protection.

5. Evaporators used in air-conditioning can be classified according to the combination of the medium to be cooled and the type of refrigerant feed.

6. Screw compressors are based on a mechanism made up of two threaded rotors.

7. An evaporator is a heat exchanger extracting heat from the air.

8. The electrical chillers dominating the market are scroll compressors, screw compressors, centrifugal compressors and others.

9. Having few moving parts, centrifugal compressor is economical to operate.

10. Providing larger evaporating surface area, flooded liquid coolers need minimal space.

11. The system objectives having been determined, the architect choose the type of system.

12. The centrifugal compressor being ideal for air conditioning applications, the engineers used them a lot.

13. Time permitting, they will come next week.

14. Your attempt falling, no one will help us.

Упражнение 7. Заполните пропуски, используя данные слова.

Are used; is used; is; reenters; to absorb.

Expansion process

The final step in the refrigeration cycle …….. the expansion of the refrigerant in an expansion valve. This relieves the pressure built up by the compressor. Temperature is thus reduced even further allowing the refrigerant …….. more heat from the interior space when it …….. the evaporator. For large chillers, electronic thermostatic expansion valves ……. as expansion device, whereas in smaller systems such as window air conditioners capillary tube ……. .

Упражнение 8. Образуйте существительные от следующих глаголов, используя суффикс –ment и переведите их.

Accomplish; assign; assess; govern; enforce; environ; equipment; move; manage; replace; require; supple; treat.

Упражнение 9. Задайте 5 вопросов различных типов к тексту А.

Текст В