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  What is the Joule-Thomson effect? If a perfect gas is allowed to expand freely, without doing work (e.g. through a throttle valve) there is no change in its temperature. In practice, however, the temperature changes slightly, because work is done by or against the intermolecular forces. This change, known as the Joule-Thomson effect, may be a rise or fall. In the case of air and similar gases at high pressures and low temperatures it is a fall. This fact is used in the laboratory for the production of extremely low temperatures.

  What are the principal ways in which heat is produced? The sun provides the earth with a continuous supply of heat. Many chemical reactions result in the formation of molecules which have a smaller store of heat energy than those from which they were produced, the difference is transferred to the surroundings which are thereby heated. Combustion is the most important case of such a chemical change. In human beings, animals, plants and even vegetables and fruits after gathering, a kind of slow combustion is always in progress, so that these also are sources of heat. Whenever two substances are in contact and one moves relatively to the other, the energy which has to be expended in producing the movement, that is to say in overcoming frictional resistance, appears as heat. Thus pumping water through a pipe, or circulating air through a duct by means of a fan, or driving a machine of any kind, are all processes in which the energy expended is converted into heat. The compression of gas produces heat because the piston or other

moving surface which pushes the molecules of gas forward “speeds them up”. Whenever an electric current flows, the electrical energy appears as heat directly, as in the case of an electric heater or lamp, or part of it does so while the rest is converted into mechanical power and so ultimately into heat, as in the electric motor.

Прочитайте и переведите слова

Throttle, valve, intermolecular, Joule-Thomson effect, extremely, supply, result in, store, combustion, source, relatively, expend, frictional, resistance, pump, pipe, circulating, whenever, compression, molecule.

Прочитайте слова, обратите внимание на особенности их написания и произношения

1) valve, wave, value, volume

2) expend, expand, expanse, expect

3) effect, affect, agreed, afraid

4) pump, pipe, paper, power

5) source, south, thought, supper, supreme

6) store, story, strong, stroke

Из указанного ниже списка слов выберите термины и переведите их на русский язык

Paper, valve, supper, stroke, combination, combustion, expense, expand, wave, volume, surface, resistance, substance, contact, water, compression.

Закончите предложения и переведите их на русский язык

1. The pressure will fall with the temperature in accordance with the...

2. Any further reduction in temperature...

3. In practice, the temperature changes ...

4. This fact is used in the laboratory ...

5. Combustion is the most important case ...

6. The sun provides the earth with ...

7. Pumping water, driving machine of any kind and etc. are all the processes ...

Переведите предложения на английский язык

1. На практике, однако, температура незначительно

 меняется, так как совершается работа межмолекулярными силами

или против них.

2. Этот факт используется для получения крайне низких

температур в лабораторных условиях.

3. Это изменение, известное как эффект Джоуля-Томсона,

сопровождается повышением или понижением температуры.

Ответьте на следующие вопросы

1. What is combustion?

2. What does resist mean?

3. What is the Joule – Thomson effect?

4. What does the compression of gas produce and why?

Text 9. REFRIGERATION

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  What is refrigeration? Refrigeration is the transfer of heat from a substance to be cooled to somewhere else. As heat flows naturally from anybody into any other colder body with which it is in contact, refrigeration is simple when a supply of some suitable colder substance is available. For example, fish can be cooled by packing ice around them. Where a suitable colder substance is not available then one has to be produced, a complicated procedure involving the expenditure of energy: it is a process of this kind that is usually implied when the term refrigeration is used. Nearly all refrigerating plants utilize the lowering of temperature which results from the controlled evaporation of a liquefied gas. When only small refrigerating effects are required they can be obtained by the direct application of electricity through a suitable thermocouple.

 How does such a thermocouple operate? In its simplest form a thermoelectric cooling device consists of pairs of semiconductor blocks connected in series and arranged as a sandwich, one face of which becomes hot and the other cold when a suitable direct current is applied. Therefore in effect, heat is taken from one side and discharged on the other an ample heat sink being provided for its removal.

What is a heat sink? A heat sink is a means for disposing of unwanted heat, usually by using it to increase the temperature of water, which is then run to waste.

Прочитайте и переведите слова

Piston, to push, heater, ultimately, refrigeration, to transfer, expenditure, to imply, refrigerating plant, to result from, controlled evaporation, thermocouple, device, semiconductor block, in series, face, direct current, in effect, to discharge, sink.

3. Словам под буквой а) подберите соответствующий перевод из б):

а)

semiconductor

charge

face

plant

to result from

to result in

heater

in series

thermocouple

evaporation

refrigeration

б)

охлаждение

приводить к

обогреватель

поверхность, сторона

последовательно

термопара

заряд

испарение

вытекать из

полупроводник

завод, установка

Прочитайте и переведите слова, обращая внимание на способы их образования

a) to conduct – conductor – semiconductor – conductance – conductivity

б) to charge – charge – chargeable – discharge – recharge

в) vapor – vaporize – vaporization – evaporation

г) refrigerate – refrigerator – refrigeration

д) to heat – heat – heater – overheat – superheat – superheater –superheating – overheating

К указанным ниже глаголам подберите подходящие по смыслу существительные, переведите на русский язык

a) to compress, to heat, to transfer, to convert, to push, to generate, to cool.

б) liquid, molecules, current, gas, energy, face.

Закончите предложения и переведите их на русский язык.

1. Fish can be cooled …

2. Refrigeration is the transfer …

3. Heat is taken from one side and …

4. A heat sink is a …

Ответьте на вопросы

1. What does the compression of gas produce?

2. What is refrigeration?

3. How do all refrigerating plants operate?

4. How does a thermocouple operate?

Text 10. FRIGISTOR