The Basics of Process Technology (Основы технологических процессов). Учебное пособие

There are five dominant classes of systems: Isolated Systems, Adiabatic Systems, Diathermic Systems, Closed Systems, Open Systems. As time passes in an isolated system, internal differences in the system tend to even out and pressures and temperatures tend to equalize, as do density differences. A system in which all equalizing processes have gone practically to completion, is considered to be in a state of thermodynamic equilibrium. In thermodynamic equilibrium, a system's properties are, by definition, unchanging in time. Systems in equilibrium are much simpler and easier to understand than systems which are not in equilibrium.

The central concept of thermodynamics is that of energy, the ability to do work. As stipulated by the first law, the total energy of the system and its surroundings is conserved. It may be transferred into a body by heating, compression, or addition of matter, and extracted from a body either by cooling, expansion, or extraction of matter.

When a system is at equilibrium under a given set of conditions, it is said to be in a definite state. The state of the system can be described by a number of intensive variables and extensive variables. The properties of the system can be described by an equation of state which specifies the relationship between these variables.

A thermodynamic process may be defined as the energetic evolution of a thermodynamic system proceeding from an initial state to a final state. Typically, each thermodynamic process is distinguished from other processes, in energetic character, according to what parameters, as temperature, pressure, or volume, etc., are held fixed. Furthermore, it is useful to group these processes into pairs, in which each variable held constant is one member of a conjugate pair. The seven most common thermodynamic processes are isobaric process, isochoric process, isothermal process, adiabatic process, isentropic process and isenthalpic process.

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6. Сопоставьте выражения:

7. Закончите предложения, используя следующие слова: temperature, enthalpy, pressure, heat, volume, entropy

∙An isobaric process occurs at a constant … .

∙An isochoric process, or isometric/isovolumetric process, occurs at a constant … .

∙An isothermal process occurs at a constant … .

∙An adiabatic process occurs without loss or gain of … .

∙An isentropic process (reversible adiabatic process) occurs at a constant … .

∙An isenthalpic process occurs at a constant… .

8.Переведите текст, выучите наизусть определения четырех законов термодинамики

Laws of Thermodynamics

In thermodynamics, there are four laws which can be applied to systems about which one knows nothing other than the balance of energy and matter transfer.

The four laws are:

∙The zeroth law of thermodynamics about the thermodynamic equilibrium is an equivalence relation.

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If two thermodynamic systems are separately in thermal equilibrium with a third, they are also in thermal equilibrium with each other.

∙The first law of thermodynamics, about the conservation of energy.

The change in the internal energy of a closed thermodynamic system is equal to the sum of the amount of heat energy supplied to the system and the work done on the system.

∙The second law of thermodynamics, about entropy.

The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.

∙The third law of thermodynamics, about absolute zero temperature.

As a system asymptotically approaches absolute zero of temperature, all processes virtually cease and the entropy of the system asymptotically approaches a minimum value; also stated as: "the entropy of all systems and of all states of a system is zero at absolute zero".

9. Ответьте на вопросы

1.What is the object of thermodynamics study?

2.What types of boundaries do you know?

3.What intensive variables can you name?

4.When does the entropy of the system approach a minimum value?

5.What systems are easier to understand and to study?

6.When does the isentropic process occur?

7.What system can you consider closed?

10. Переведите предложения

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1.Теплота, сообщаемая системе, расходуется на изменение внутренней энергии системы и на совершение системой работы против внешних сил.

2.Температура, давление, объем – это те параметры, с помощью которых можно описать энергетический характер системы.

3.Обмен теплотой, работой, веществом между системой и внешней средой осуществляется через границу, которая может быть воображаемой или реальной.

4.Раздел теоретической физики, в котором физические свойства макроскопических систем изучаются с помощью термодинамического метода, называется термодинамикой.

5.Различают два типа термодинамических параметров: экстенсивные и интенсивные.

6.Большую роль играет адиабатный процесс, который происходит без теплообмена между системой и внешней средой.

7.Открытой системой называется термодинамическая система, которая может обмениваться веществом с внешней средой.

11. Составьте рассказ о том, что изучает термодинамика

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Unit 4

HEAT TRANSFER

1.Прочитайте следующие интернациональные слова вслух и, основываясь на значениях соответствующих русских слов, определите их значение:

thermal, physics, result, classical, convection, radiation, combination, spontaneous, electromagnetic, electric, mechanism, transport, generate, gradient, microstructure, approximation, spectral, cosmic, spectrum

2. Прочитайте и переведите следующие глаголы:

to stop, to act, to emitte, to split, to attract, to encounter, to present, to refer, to transfer, to force, to design, to rise, to form, to cool, to shroud, to occur, to like

3.Подберите эквивалентный перевод словосочетаний из колонки А в колонке В

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4. Переведите и озаглавьте текст

In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. Heat transfer always occurs from a hot body to a cold one, a result of the second law of thermodynamics. Heat transfer can never be stopped; it can only be slowed down. Classical transfer of thermal energy occurs only through conduction, convection, radiation or any combination of these.

Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences.

Thermal radiation is electromagnetic radiation emitted from the surface of an object which is due to the object's temperature. Infrared radiation from a common household radiator or electric heater is an example of thermal radiation.

Convective heat transfer is a mechanism of heat transfer occurring because of bulk motion of fluids. It is split into two categories: natural (or free) convection and forced (or advective) convection. Natural convection is a mechanism, or type of heat transport in which the fluid motion is not generated by any external source (like a pump, fan, suction device, etc.) but only by density differences in the fluid occurring due to temperature gradients. Natural convection has attracted a great deal of attention by researchers because of its presence both in nature, seen in the rising plume of hot air from fire, oceanic currents, and sea-wind formation, and in engineering applications like formation of microstructures during the cooling of molten metals. Forced convection is often encountered by engineers designing or analyzing heat exchangers, pipe flow, and flow over a plate at a different temperature than the stream. However, in any forced convection situation, some amount of natural convection is always present. When the natural convection is not negligible, such flows are typically referred to as mixed convection.

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5.Составьте предложения, подобрав следующие словосочетания:

thermal conduction, natural convection, convective heat transfer, thermal radiation, advective convection

a.… is a mechanism, or type of heat transport in which the fluid motion is not generated by any external source but only by density differences in the fluid occurring due to temperature gradients.

b.… is electromagnetic radiation.

c.… is a mechanism, or type of heat transport in which fluid motion is generated by an external source.

d.… is a mechanism of heat transfer occurring because of bulk motion of fluids.

e.… is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature.

6.Определите, являются ли следующие утверждения верными в соответствии с текстом упражнения 4

∙Transfer of thermal energy occurs only through conduction and radiation or any combination of these.

∙Infrared radiation is an example of thermal radiation.

∙Natural convection is a mechanism, or type of heat transport in which the fluid motion is generated by external source.

∙The second law of thermodynamics describes heat transfer from a hot body to a cold one.

∙Density differences in the fluid are the result of temperature gradients.

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7. Прочитайте и переведите текст

Black Body

In physics, a black body is an object that absorbs all electromagnetic radiation that falls onto it. No radiation passes through it and none is reflected. It is this lack of both transmission and reflection to which the name refers. These properties make black bodies ideal sources of thermal radiation. That is, the amount and wavelength of electromagnetic radiation they emit is directly related to their temperature. Real objects never behave as full-ideal black bodies, and instead the emitted radiation at a given frequency is a fraction of what the ideal emission would be. The emissivity of a material specifies how well a real body radiates energy as compared with a black body. This emissivity depends on factors such as temperature, emission angle, and wavelength. However, it is typical in engineering to assume that a surface's spectral emissivity and absorptivity do not depend on wavelength, so that the emissivity is a constant. This is known as the grey body assumption.

In astronomy, objects such as stars are frequently regarded as black bodies, though this is often a poor approximation. An almost perfect black-body spectrum is exhibited by the cosmic microwave background radiation. Hawking radiation is black-body radiation emitted by black holes.

8. Ответьте на вопросы по тексту упражнения 7

∙What is a black body in the theory of heat transfer?

∙What kind of body can you name grey?

∙What properties make a black body the ideal source of thermal radiation?

∙What type of radiation do the black holes emit?

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9. Переведите текст письменно

Перенос тепла между телами, имеющими различную температуру, называется теплообменом. Теплообмен осуществляется благодаря разности температур. В соответствии со вторым законом термодинамики тепло самопроизвольно переходит от более нагретого тела к менее нагретому. Тела, участвующие в теплообмене, называются теплоносителями. Различают три способа распространения тепла: теплопроводность, конвекция и тепловое излучение. Теплопроводность представляет собой перенос тепла вследствие беспорядочного движения микрочастиц при их соприкосновении друг с другом. Конвекция – это перенос тепла вследствие движения и перемешивания макроскопических объемов газа или жидкости. Тепловое излучение – это процесс распространения электромагнитных колебаний с различной длиной волны. Часто теплообмен осуществляется несколькими способами одновременно. Такой теплообмен называется смешанным или сложным.

10. Составьте рассказ о видах теплообмена

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Unit 5

HEAT EXCHANGERS

1.Прочитайте следующие интернациональные слова вслух и, основываясь на значениях соответствующих русских слов, определите их значение:

contact, natural, perpendicular, maximize, turbulence, fluid, gas, conditioning, minimize, elastomer, design, parallel, typical, channel, effective, configuration, coefficient, construction, optimum, material

2. Прочитайте и переведите следующие глаголы:

to build, to mix, to classify, to enter, to design, to maximize, to minimize, to affect, to consist, to heat, to cool, to differ, to stamp, to induce, to occupy

3.Подберите эквивалентный перевод словосочетаний из колонки А в колонке В

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