6. Ответьте на вопросы

1. What does every liquid produce?

2. What is saturated vapor?

3. What is superheated vapor?

Text 5. ENTHALPY

1. Прочитайте текст, обращая внимание на незнакомые слова и выражения

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.

2. 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.

3. 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.

5. Прочитайте и переведите слова и выражения

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

6. 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

7. 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.

8. 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…

…

9. Ответьте на вопросы

1. What is thermodynamics?

2. What is enthalpy?

3. What is entropy?

4. What is adiabatic compression?

Text 6.GAS

1. Прочитайте текст, обращая внимание на незнакомые слова и выражения

What is a perfect gas? It is one which behaves in accordance with the gas law,

PV = MRT, where P = absolute pressure, V = volume, M = mass, T = absolute temperature, and R is a constant for the particular gas depending on its molecular weight.

The volume is directly proportional to the temperature and inversely proportional to the pressure. Oxygen, nitrogen, air and hydrogen are examples of gases which are almost perfect at moderate temperatures and pressures. The gases commonly used in refrigeration are not perfect under normal operating conditions. With the exception of carbon dioxide, their deviations from the gas law are not great at the temperatures and pressures normally prevailing in the low pressure side of a vapor compression refrigerating plant.

What is the difference between gas and vapor? The gaseous substance in contact with the liquid from which it is formed is known as a vapor and it is still called a vapor if superheated to some extent. At still higher temperatures it is known as a gas but there is no sharp line of demarcation.

What is critical temperature? Although in general a vapor may be liquefied by increasing its pressure up to the saturation value corresponding to the temperature, this is not so if the temperature is above a certain level. For any vapor this temperature above which no pressure will produce liquefaction, is called its critical temperature.

What is critical pressure? The critical pressure of a vapor is the pressure required to liquefy it at the critical temperature and is the highest pressure on the temperature – pressure graph for saturated vapor. At temperatures above critical the pressure exerted by a vapor depends on the weight of it in a given space.

1. Прочитайте и переведите слова

proportional, inversely proportional, oxygen, nitrogen, hydrogen, moderate, refrigeration, carbon dioxide, deviation, prevailing, gaseous, superheated, demarcation, saturated, exerted, condition, liquid, pressure.

2. Прочитайте и переведите слова и выражения

Demarcation (line), prevailing, proportional, moderate, inversely, superheated (gas), perfect (gas), oxygen.

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

кислород

разграничение

идеальный

перегретый

пропорциональный

умеренный

преобладающий

обратно

4. От приведенных ниже слов образуйте однокоренные слова и

переведите их на русский язык

Behave, refrigerate, operate, saturate, superheat, press, vapor, produce, liquid, form.

5. Переведите слова и выражения, составьте выражения с каждым из них

1) temperature – critical, moderate, absolute, ground, indoor

2) gas – refrigerated, superheated, liquefied, city, dry, fuel

3) proportional – directly, inversely, mean

4) steam – dead, gaseous, dry, direct, wast

6. Ответьте на вопросы

1. What is gas?

2. What is a perfect gas?

3. What is the difference between gas and vapor?

4. What is critical temperature?

5. What is critical pressure?

Text 7.BOILING

1. Прочитайте текст, обращая внимание на незнакомые слова и выражения

What is boiling point? When a liquid contained in a vessel having an opening to permit the exit of vapor is heated, its vapor pressure rises and eventually reaches that of the surrounding atmosphere. When this happens, the liquid boils and the temperature at which it does so is known as the boiling point for that particular pressure. It is therefore the temperature at which the saturation pressure of the vapor equals that of the atmosphere. When the liquid is in a closed vessel or system in contact only with its own vapor, the term boiling point is not very appropriate. It is preferable to speak of the saturation temperature, which is the temperature of the liquid surface corresponding to the pressure of the vapor in contact with it.

What happens to a gas which is allowed to expand in an engine cylinder? Conversely to the compression of a gas, the work done by an expanding gas is produced at the expense of the heat contained in the gas, which therefore falls in temperature.

What is the triple point? If a closed vessel containing only a pure liquid and its vapor is

cooled, the pressure will fall with the temperature in accordance with the pressure – temperature curve for saturated vapor. A temperature will be reached at which the liquid begins to freeze. Any further reduction in temperature will cause the transformation of

the liquid into solid. This temperature and its corresponding pressure are known as the triple point for the particular substance. Only at this temperature and pressure can the substance exist simultaneously in solid, liquid and vapor forms.

2. Прочитайте и переведите слова

Contained, opening, eventually, surrounding, appropriate, preferable, conversely, expanding, pure, triple, point, exist, simultaneously, curve, temperature, pressure, substance, transformation, corresponding.

3. Найдите в тексте 1: а) существительные, б) наречия, в) глаголы, г) прилагательные, д) причастия и выпишите их

4. Составьте сочетания из указанных ниже слов и переведите их на русский язык. Составьте предложения с этими словосочетаниями на английском языке

a) exit, appropriate, preferable, surrounding, curve.

б) pressure, temperature, gas, atmosphere, volume.

5. Составьте предложения и переведите их на русский язык

1. Curve, in accordance with, the pressure, the pressure temperature, for, will, the temperature, fall, vapor, saturated, with.

2. Contained, the work, gas, done, is at, the expense, by, an, expanding, of , the, in, the, gas, produced, heat.

3. Saturation, the, is, the surface, to, the, of, the, in, vapor, with, it, corresponding, temperature, temperature, liquid, pressure, contact, of, the.