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

4. Прочитайте и переведите текст

Heat Exchangers

A heat exchanger is a device built for efficient heat transfer from one fluid to another, whether the fluids are separated by a solid wall so that they never mix, or the fluids are directly contacted. They are widely used in petroleum refineries, chemical plants, petrochemical plants, natural gas processing, refrigeration, power plants, air conditioning and space heating.

Heat exchangers may be classified according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient, in that it can transfer the most heat. In a cross-flow heat exchanger, the fluids travel roughly perpendicular to one another through the exchanger.

For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger. The exchanger's performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence.

5.Подберите эквивалентный перевод для различных видов теплообменников

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6.Вставьте следующие слова и фразы и переведите текст: plates, tube bundle, plate heat exchanger, fins, tube heat exchanger, heat transfer, surface

A typical heat exchanger, usually for higher-pressure applications, is the ________ which consists of a series of tubes, through which one of the fluids runs. The second fluid runs over the tubes to be heated or cooled. The set of tubes is called ________, and may be composed of several types of tubes: plain, longitudinally finned, etc. Another type of heat exchanger is the ________. One is composed of multiple, thin, slightly-separated plates that have very large ________ areas and fluid flow passages for________. This stacked-plate arrangement can be more effective, in a given space, than the shell and tube heat exchanger. Plate heat exchangers differ in the types of ________ that are used, and their configurations. Some plates may be stamped with "chevron" or other patterns, where others may have machined ________ and grooves.

7.Определите, являются ли следующие утверждения верными в соответствии с текстами упражнений 4 и 6

∙Heat exchangers may be classified according to the temperature of flow.

∙Fins and grooves on the heat exchanger surface intensify the heat transfer process.

∙In parallel-flow heat exchangers, two fluids enter the exchanger from opposite ends.

∙Tube heat exchanger is composed of multiple, thin, slightlyseparated plates that have very large surface areas.

∙Tube heat exchanger is usually used for higher-pressure applications.

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8. Переведите предложения

∙В пластинчатом теплообменнике поверхность теплообмена образуется гофрированными параллельными пластинами.

∙Жидкости, между которыми происходит теплообмен, движутся в каналах между пластинами.

∙Компактными и эффективными теплообменниками считаются теплообменники с оребренной поверхностью.

∙Теплообменные аппараты широко используются на нефтеперерабатывающих заводах, в химическом производстве для обработки природного газа, на электростанциях и для кондиционирования и отопления помещений.

∙Увеличение площади поверхности стенок и уменьшение сопротивления жидкости, проходящей через теплообменный аппарат, позволяют интенсифицировать процесс теплообмена.

9.Переведите 10 отличий пластинчатых и трубчатых теплообменников

Ten Points of Plate and Tubular Exchangers Comparison

In forming a comparison between plate and tubular heat exchangers there are a number of guidelines which will generally assist in the selection of the optimum exchanger for any application. In summary, these are:

1.For liquid/liquid duties, the plate heat exchanger will usually give a higher overall heat transfer coefficient and in many cases, the required pressure loss will be no higher.

2.The effective mean temperature difference will usually be higher with the plate heat exchanger.

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3.Although the tube is the best shape of flow conduit for withstanding pressure it is entirely the wrong shape for optimum heat transfer performance since it has the smallest surface area per unit of cross-sectional flow area.

4.Because of the restrictions in the flow area of the ports on plate units it is usually difficult to produce economic designs when it is necessary to handle large quantities of low-density fluids such as vapors and gases.

5.A plate heat exchanger will usually occupy far less floor space than a tubular for the same duty.

6.From a mechanical viewpoint, the plate passage is not the

optimum, and gasketed plate units are not made to withstand operating pressures much in excess of 20 kgf/cm2.

7.For most materials of construction, sheet metal for plates is less expensive per unit area than tube of the same thickness.

8.When materials other than mild steel are required, the plate will usually be more economical than the tube for the application.

9.When mild steel construction is acceptable and when a closer temperature approach is not required, the tubular heat exchanger will often be the most economic solution since the plate heat exchanger is rarely made in mild steel.

10.Plate heat exchanger use is limited by the elastomer gasket.

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10.Составьте диалог «Ten Points of Plate and Tubular Exchangers Comparison», основываясь на лексическом материале упражнения 9. Включите в диалог следующие выражения:

Agreeing (согласие)

I agree up to a point, but …

I agree with that point of view on the whole.

I completely/totally agree with that point of view.

I couldn’t agree more!

Disagreeing (несогласие)

I’m not really sure about that …

I don’t really agree with that point of view, because …

I completely/totally disagree with that point of view.

I think it’s ridiculous to say …

11. Составьте рассказ о теплообменных аппаратах

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Unit 6

FRACTIONATION

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

fractionation, fraction, distillation, product, component, interval, portion, condense, composition, contact, type, factor, vacuum, structure, process, separation, natural

2. Прочитайте и переведите следующие глаголы:

to distill, to separate, to base, to withdraw, to exit, to achieve, to return, to show, to depend, to require, to affect, to find, to feed, to take place, to liquify

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

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4. Прочитайте и переведите текст

Fractionation Columns

Fractionation is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities.

Figure depicts an industrial fractionation column separating a feed stream into one distillate fraction and one bottoms fraction. However, many industrial fractionation columns have outlets at intervals up the column so that multiple products having different boiling ranges may be withdrawn from a column distilling a multicomponent feed stream. The "lightest" products with the lowest boiling points exit from the top of the columns and the "heaviest" products with the highest boiling points exit from the bottom. Industrial fractionating columns use external reflux to achieve better separation of products. Reflux refers to the portion of the condensed overhead liquid product that returns to the upper part of the fractionating column as shown in figure. Inside the column, the downflowing reflux liquid provides cooling and condensation of upflowing vapors thereby increasing the efficacy of the distillation tower. The more reflux and more trays provided, the better is the tower's separation of lower boiling materials from higher boiling materials.

The design and operation of a fractionating column depends on the composition of the feed as well as the composition of the desired products.

Bubble-cap "trays" or "plates" are one of the types of physical devices which are used to provide good contact between the upflowing vapor and the downflowing liquid inside an industrial fractionating column.

In industrial uses, sometimes a packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum. This

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packing material can either be random dumped packing or structured sheet metal. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. Differently shaped packings have different surface areas and void space between packings. Both of these factors affect packing performance.

Fractionation columns are widely used in the chemical process industries where large quantities of liquids have to be distilled. Such industries are the petroleum processing, petrochemical production, natural gas processing, coal tar processing, brewing, liquified air separation, and hydrocarbon solvents production and similar industries, but it finds its widest application in petroleum refineries.

Figure. The schematic of a continuous fractionating column

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6. Переведите описание схемы, изображенной на рисунке

Исходная смесь (жидкость), состоящая из двух компонентов, поступает в колонну. Ректификационная колонна имеет цилиндрический корпус, внутри которого установлены контактные устройства в виде тарелок. Из ребойлера (кипятильника) в нижнюю часть колонны поступают пары, которые движутся вверх. Это восходящий поток. Пары проходят через слой жидкости на тарелках. Компонент смеси, имеющий меньшую точку кипения, в виде пара поступает в верхнюю часть колонны, а затем в конденсатор, где конденсируется. Полученная жидкость, проходя через сборник орошающей

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фракции, подается на верхнюю тарелку колонны. Это нисходящий поток. Жидкость, выходящая из низа колонны делится на две части. Одна часть направляется в кипятильник, другая – в сборник.

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

∙The “lightest” products with the lowest boiling points exit from the bottom of the columns and the “heaviest” products with the highest boiling points exit from the top.

∙Fractionation is separation of the mixture into its component parts, or fractions, based on the differences in their volatilities.

∙The composition of the feed as well as the composition of the desired products is very important for the column construction.

∙The less reflux and more trays are provided, the better is the tower's separation of lower boiling materials from higher boiling materials.

8. Ответьте на вопросы

∙What is the main application of the fractionation processes?

∙Can you name any types of fractionation columns?

∙What are the most important factors for the column construction?

∙What is the operation principle of continuous fractionating column?

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