The auto-refrigeration effect of the adiabatic flash evaporation lowers the temperature of the liquid and vapor refrigerant mixture.

8) In the evaporator the circulating refrigerant absorbs and removes heat which is subsequently rejected in the condenser and transferred elsewhere by the water or air.

9) Centrifugal compressors raise the pressure of the refrigerant by dynamic energy, using a rotating impeller, and converting it to pressure energy.

 

VIII. Fill in the blanks with appropriate words:

 

1) Heat is transferred from a … source to a higher temperature ….

2) This most common refrigeration cycle uses an … motor to drive ….

3) Since evaporation occurs when heat is absorbed, and condensation occurs when heat is released,

4) Despite the low … the low pressure causes the … to evaporate into a vapor.

5) A liquid refrigerant is the … which absorbs and removes … from the space.

6) In the condenser the hot vapor is … and condensed into a ….

7) The rejected … is carried away by either the … or the air.

8) The … reduction results in the adiabatic … of a part of the liquid ….

9) The warm air … the liquid part of the cold … mixture in the evaporator.

10) In … compressors the refrigerant is compressed when one spiral orbits around a second stationary spiral.

 

IX. Translate into English, using the active vocabulary:

 

1. Парокомпрессионное охлаждение используется в домашних холодильниках для хранения продуктов.

2. Холодильная установка выводит тепло из своей внутренней части в комнату, где она находится.

3. В холодольном цикле для приведения в действие компрессор используется электродвигатель.

4. Охладитель закачивается в испарительный змеевик, где давление низкое.

5. Теплообменник в конденсоре охлаждается вентилятором.

6. Парокомпрессионная система состоит из четырех компонентов: компрессора, конденсора, регулирующего вентиля и испарителя.

7. Перенагретый пар – это термодинамическое состояние горячего сжатого пара.

8. В регулирующем вентиле насыщенная жидкость подвергается резкому уменьшению давления.

9. Холодная смесь проходит через трубы в испарителе.

10. Возвратно-поступательный и ротационный винтовой компрессоры – это объемные компрессоры.

 

X. Answer the questions:

 

1) What is vapor-compression refrigeration used for?

2) Is a heat pump used for refrigeration?

3) What does the refrigeration cycle consist of?

4) What law is the work based on in the vapor-compression refrigeration cycle?

5) What does the refrigeration cycle use to drive a compresor?

6) What is the medium which absorbs and removes heat?

7) What components does the vapor-compression system have?

8) What is the saturated vapor?

9) What is the thermodynamic state of the hot compressed vapor?

10) What happens with the hot vapor in the condenser?

11) Where does the circulating refrigerant reject heat from the system?

12) What does a saturated liquid undergo in the expansion valve?

13) What lowers the temperature of the liquid and vapor refrigerant mixture?

14) What happens with the cold mixture in the evaporator?

15) What types of compressor do you know?

16) What compressors are positive displacement compressors?

17) How do rotary screw / centrifugal / scroll compressors work?

 

XI. Skim through the text and say in one sentence what the message of the text is. Answer the questions which follow.

 

A single-stage refrigeration system may include other equipment items that would be provided in a large commercial or industrial vapor compression refrigeration system, such as:

· A horizontal or vertical pressure vessel, equipped internally with a demister, between the evaporator and the compressor inlet to capture and remove any residual, entrained liquid in the refrigerant vapor because liquid may damage the compressor. Such pressure vessels are most often referred to as "suction line accumulators". (In other industrial processes they are called "compressor suction drums" or "knockout drums".)

· Large commercial or industrial refrigeration systems may have multiple expansion valves and multiple evaporators in order to refrigerate multiple enclosed spaces or rooms. In such systems, the condensed liquid refrigerant may be routed into a pressure vessel, called a receiver, from which liquid refrigerant is withdrawn and routed through multiple pipelines to the multiple expansion valves and evaporators.

· Some refrigeration units may have multiple stages which require the use of multiple compressors in various arrangements.

 

Refrigeration application	Short descriptions	Typical refrigerants used
Domestic refrigeration	Appliances used for keeping food in dwelling units	R-600a, R-134a
Commercial refrigeration	Holding and displaying frozen and fresh food in retail outlets	R-134a, R-404A, R-507
Food processing and cold storage	Equipment to preserve, process and store food from its source to the wholesale distribution point	R-134a, R-407C, R-410A, R-507
Industrial refrigeration	Large equipment, typically 25 kW to 30 MW, used for chemical processing, cold storage, food processing and district heating and cooling	R-134a, R-404A, R-507, R-717
Transport refrigeration	Equipment to preserve and store goods, primarily foodstuffs, during transport by road, rail, air and sea	R-134a, R-407C, R-410A
Electronic cooling	Low-temperature cooling of CMOS circuitry and other components in large computers and servers	R-134a, R-404A, R-507
Medical refrigeration		R-134a, R-404A, R-507
Cryogenic refrigeration		Ethylene, Helium

* * *

1. What other equipment items may a single-stage refrigeration system include?

2. Where is a pressure vessel? What is it for? Why?

3. What do large commercial refrigeration systems have multiple expansion valves to?

4. Why do some refrigeration units use multiple compressors?

5. What application of regrigeration do you know?

6. What is industrial refrigeration / transport refrigeration used for?

7. Where is electronic cooling used?

 

UNIT 4

I. Read and translate the text:

 

History of the refrigerator

The first known artificial refrigeration was demonstrated by William Cullen at the University of Glasgow in 1748, and relied on the vapor-compression refrigeration process explained by Michael Faraday. Between 1805, when Oliver Evans designed the first refrigeration machine that used vapor instead of liquid, and 1902 when Willis Haviland Carrier demonstrated the first air conditioner, scores of inventors contributed many small advances in cooling machinery. In 1850 or 1851, Dr. John Gorrie demonstrated an ice maker. In 1857, Australian James Harrison introduced vapor-compression refrigeration to the brewing and meat packing industries. The absorption refrigerator was invented by Baltzar von Platen and Carl Munters in 1922, while they were still students at the Royal Institute of Technology in Stockholm, Sweden. It became a worldwide success and was commercialized by Electrolux. Other pioneers included Charles Tellier, David Boyle, and Raoul Pictet.

In a few exceptional cases, mechanical refrigeration systems had been adapted by the start of the 20th century for use in the homes of the very wealthy, and might be used for cooling both living and food storage areas. One early system was installed at the mansion of Walter Pierce, an oil company executive.

Marcel Audiffren of France championed the idea of a refrigerating machine for cooling and preserving foods at home. His U.S. patents, issued in 1895 and 1908, were purchased by the American Audiffren Refrigerating Machine Company. Machines based on Audiffren's sulfur dioxide process were manufactured by General Electric in Fort Wayne, Indiana and marketed by the Johns-Manville company. The first unit was sold in 1911. Audiffren machines were expensive, selling for about $1,000 — about twice as much as an automobile cost at the time.

General Electric sought to develop refrigerators of its own, and in 1915 the first unit was assembled. In 1916 Kelvinator and Servel came out with two units among a field of competing models. This number increased to 200 by 1920. In 1918, Kelvinator had a model with automatic controls.

These home units usually required the installation of the mechanical parts, motor and compressor, in the basement or an adjacent room while the cold box was located in the kitchen. There was a 1922 model that consisted of a wooden cold box, water-cooled compressor, an ice cube tray and a 9 cubic foot compartment for $714. (A 1922 Model-T Ford cost about $450.) In 1923 Frigidaire introduced the first self-contained unit. About this same time porcelain covered metal cabinets began to appear. Ice cube trays were introduced more and more during the 1920s; up to this time freezing was not a function of the modern refrigerator.

The first refrigerator to see widespread use was the General Electric "Monitor-Top" refrigerator introduced in 1927. The compressor assembly, which emitted a substantial amount of heat, was placed above the cabinet, and surrounded with a decorative ring. Over 1,000,000 units were produced. This refrigerator used sulfur dioxide refrigerant. Many units are still functional today.

The introduction of freon expanded the refrigerator market during the 1930s, and freezer units became a little more common and requested during the 1940s. Home units did not go into mass production until after WWII. The 1950s and 60s saw technical advances like automatic defrosting and automatic ice making. Developments of the 1970s and 80s brought about more efficient refrigerators, and environmental issues banned the use of CFC (freon) refrigerants.

Refrigerators used to consume more energy than any other home appliance, but in the last twenty years, great strides have been made to make refrigerators more energy efficient. Current models that are Energy Star qualified use 50 percent less energy than models made before 1993.

Introduction of home freezer units occurred in the United States in 1940, and frozen foods began to make the transition from luxury to necessity.

 

Words to the text

to rely – полагаться, надеяться

scores – множество

to contribute – вносить вклад

brewing – пивоварение

to install – устанавливать

mansion – большой особняк, большой дом

to issue – выходить

to purchase – покупать

sulfur dioxide – диоксид серы, сернистый ангидрид

to seek – искать, разыскивать; пытаться найти

 

competing – конкурирующий

adjacent – расположенный рядом, смежный, соседний

self-contained – смонтированный в общем корпусе

cabinet – шкаф

porcelain – фарфор

defrosting – размораживание

to bann – налагать запрет; запрещать

to consume - расходовать, тратить

Energy Star – стандарт экономичного энергопотребления электроприборов

 

II. Fulfill the table using information from the text. (work in pairs or groups)

 

Date	Inventor / firm	Refrigeration system	Features of refrigerator
Start of the 20^th century
1895 – 1908
1930s – 1940s
1950s – 1960s
1970s – 1980s
2000s

 

III. Make up different kinds of questions to the text. Ask your partner about historical application of refrigeration. (Work in pair or group)

 

I group (Yes/No-questions)

Did Carrier demonstrate the first air conditioner?

II group (Wh-questions)

When did Oliver Evans design the first refrigeration machine?

 

III group (Tag-question)

 

Dr. John Gorrie demonstrated an ice maker, didn’t he?

IV. Skim through the text and say in a few sentences what the message of the text is. Answer the questions which follow.