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  Every liquid produces a vapor as the molecules near its surface free themselves from the attraction of their neighbors and fly off into space. This vapor exerts pressure on any containing vessel and the amount of pressure exerted by the vapor of any particular liquid depends solely on the temperature of the liquid surface; the higher the temperature, the greater the pressure. For any liquid a graph can be drawn showing the relationship between this vapor pressure and the temperature of the liquid surface.

   How can gas be liquefied? When heat is removed from a gas its temperature is lowered until it reaches a value corresponding to the pressure (see above) after which further removal of heat liquefies the gas. Alternatively, an increase in pressure combined with removal of heat makes it possible to liquefy the gas without reducing its temperature.

 What is superheated vapor? It is vapor removed from contact with its liquid and at a temperature higher than that which corresponds to its pressure as indicated by

the temperature-pressure-vapor relationship for that particular substance.

 What is saturated vapor? It is vapor whose temperature and pressure are in accordance

with the temperature-vapor-pressure relationship for the particular substance. Vapor in contact with its liquid is saturated.

 What is the numerical relationship between heat units and units of mechanical work? This can be expressed as follows:

1 Btu = 778 lbft. Thus, for example, the energy given up by a weight of 77.8 lb in falling 10 ft is sufficient to heat 1 lb of water through 1F. Again, since a horsepower (hp) is the rate of production of energy of an engine doing 33,000 lbft of work per minute, 1 hp =

33.000/778 or 42.4 Btu/min and therefore 2,545 Btu/h. The kilowatt (kw), (not kilowatt hour) is another unit of power and 1 kW = 1.34 hp or 3.410 Btu/h. Further, 1 kcal = 4.18 J, and 1 J/s = 1 W.

Прочитайте и переведите слова

Vapor, attraction, space, exert, contain, vessel, particular, graph, relationship, remove, correspond, alternatively, indicate, saturate, rate, power, pressure, kilowatt.

Прочитайте однокоренные слова и объясните способ их образования

Vapor – vaporize – vaporization

Attract – attractive – attraction

Contain – container – containment

Correspond – correspondence – correspondent

Indicate – indicator – indication

Saturate – saturator – saturation

Power – powerful – powerless

От существительных образуйте глаголы и переведите их на английский язык

Пар, притяжение, показание, насыщение, давление, соответствие, связь, сила.

Заполните пропуски необходимыми по смыслу словами

1. Every liquid produces ... (vapor, gas, fog).

2. For any liquid a ... can be drawn (table, picture, graph).

3. The higher the temperature of a liquid surface, the greater the ... (power, pressure, speed).

4. Vapor in contact with its liquid is ... (disappeared, saturated, overheated).

5. The rate of production of energy is ... (voltage, resistance, horsepower).

6. The kilowatt is another unit of ... (weight, velocity, power).

Ответьте на вопросы

1. What does every liquid produce?

2. What is saturated vapor?

3. What is superheated vapor?

Text 5. ENTHALPY

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   What is enthalpy? This is a term that is often used in thermodynamic calculations.

Enthalpy is the same as heat content, or the amount of heat contained in unit weight of a substance. It is measured from some arbitrarily chosen condition taken as zero. This is not strictly correct and it is accurately defined by the equation: H = I + PV/J, where H = enthalpy, I = internal (molecular) energy, P = absolute pressure, V = volume, J – is the factor to convert heat units to work units. It can be shown mathematically that if heat is added to or taken from a substance, the change in enthalpy equals the amount of heat

added or removed, provided that the pressure remains unchanged. Again, it can be shown that the increase in enthalpy during adiabatic compression is equivalent to the work done in compression.

  What is entropy? Change of entropy, which is the only thing that concerns us in

thermodynamics, is equal to the amount of heat added or removed during a reversible process, divided by the absolute temperature; if the temperature changes during the process, as it does in the case of sensible heat, the entropy change must be evaluated by dividing the process into so many small steps that the temperature may be considered constant for each step, and adding the results (integration).

 What is adiabatic compression? When a gas or vapor is compressed in such circumstances that there is insufficient time for any substantial exchange of heat between it and its surroundings, the compression is adiabatic. It can be shown that during such a process there is no change in entropy and it is mainly this fact that makes the conception of entropy so useful. The compression of vapor in a refrigerating compressor is nearly adiabatic unless a water jacket is fitted.

Прочитайте и переведите слова

Enthalpy, thermodynamic(s), calculation, equation, volume, provide, adiabatic, compression, entropy, reversible, evaluate, step, constant, integration, circumstances, insufficient, substantial, exchange, surroundings, conception, jacket, fit.

Прочитайте слова в транскрипции и выучите их наизусть

[eidiә'bætiс kәm'preSn], ['entropi], ['enTqlpi], [ri'vq:sqbl], [sq'raundiN], [i'vxljueit], ['sq:kqmstqnsiz], [inti'greiSqn], [Tq:mqudQi'nxmiks], [sqb'stxnSl]

4. Переведите и прочитайте слова и выражения

адиабатическое сжатие, энтропия, энтальпия, обратимый, окружающая среда, оценивать, определять, условия, интегрирование, термодинамика, значительный,  существенный.

Прочитайте и переведите слова и выражения

thermodynamic(s), compression, step, jacket, integration, adiabatic, equation, evaluate, circumstances, volume, provided, conception.

Переведите слова и выражения, составьте свои собственные выражения с каждым из них

объем

понятие

условия

термодинамика; термодинамический

при условии

оценивать; определять

этап; шаг

уравнение

интегрирование

рубашка

компрессия; сжатие

адиабатический

Переведите на английский язык

1. ... именно этот факт делает условие энтропии полезным.

2. ... пока не будет устроена водяная рубашка.

3. ... отсутствует изменение в энтропии ...

4. Можно математически доказать, что если добавить

 тепло веществу или лишить его тепла, ...

5. ... рост энтальпии при адиабатическом сжатии

равняется работе, выполняемой при сжатии.

Закончите следующие предложения

1. The increase in enthalpy during adiabatic compression is

equivalent …

2. Enthalpy is the same …

3. Change of entropy is equal to …

4. The compression is adiabatic when …

5. The compression of vapor in a refrigerating compressor…

…

Ответьте на вопросы

1. What is thermodynamics?

2. What is enthalpy?

3. What is entropy?

4. What is adiabatic compression?

Text 6.GAS