ID: 2323

Название работы: Double pipe heat exchangers

Категория: Конспект урока

Предметная область: Иностранные языки, филология и лингвистика

Описание: The double pipe heat exchangers are quite simple exchangers for analysing. There are two possibilities: the use of a counter flow or parallel flow. In figure 1.2 we can see the development of the temperatures.

Язык: Английский

Дата добавления: 2013-01-06

Размер файла: 319.5 KB

Работу скачали: 25 чел.

Урок 1.2

Упражнение №1. Прочитайте слова.

[ju:] use, sup'erfluous, tubing, due;

[µ] suffer, much, bundle, construction, double;

[u:] fluid, conclude;

[au] counter, demounting.

Упражнение № 2. Сопоставьте слово с переводом и соответствующей ему транскрипцией.

bundle	['TE:m(q)Î]	благодаря, из-за
due to	['µ¹¶]	область, сфера
figure	['bµÍdÎ]	тепловой
other	['ÂqÏÁq]	пучок, связка
easily	['Çig¶]	другой, иной
temperature	['°ÊÁÎÁ]	иллюстрация, рисунок
thermal	['tÂmpr¶À¶]	легко, свободно
area	[dj³ t³]	температура, степень нагрева

Текст А

Double pipe heat exchangers

The double pipe heat exchangers are quite simple exchangers for analysing. There are two possibilities: the use of a counter flow or parallel flow. In figure 1.2 we can see the development of the temperatures. From this we can easily conclude that the counter flow is in any case more efficient than the parallel flow since the pipe fluid gets further cooled using this counter flow. While the temperatures T (of the cooled fluid) and t (of the warmed fluid) in the parallel flow heat exchanger can only approach each other, they can pass each other in the counter flow. In this case there has to be more transferred heat. This explains why in practice there is only counter flow in case of the double pipe heat exchangers. But there is one other advantage for the counter flow, since the maximum temperature differences between the two flows are much smaller, they suffer less thermal forces.

Figure 1.2: counter flow verses parallel flow.

Double pipe exchangers mostly consist of common water tubing. The use of two single flow areas leads to relatively low flow rates and moderate temperature differences. A straight double pipe heat exchanger as seen in the diagrams will not appear in practice. Most common are U-type or hairpin constructions. Due to the need of a removable bundle construction and the need for the ability to handle differential thermal expansions the exchanger is implemented in two parts. In figure 1.3 the fluids enter and leave the exchanger by the four nozzles on the right while the exchanger can freely expand to the left which makes the expansion joints to the other machinery superfluous and makes demounting much easier.

Figure 1.3: U-type or hairpin construction for a double pipe heat exchanger.

Figure 1.4: practical example: series of U-type constructions.

Ответьте на вопросы к тексту

1.   How can we analyse the double pipe heat exchangers?
2.   What is more efficient the counter flow or the parallel flow and why?
3.   Why is there only counter flow in case of the double pipe heat exchangers? Explain, please.
4.   Are there any other advantages for the counter flow?
5.   What do double pipe exchangers mostly consist of?
6.  What leads to relatively low flow rates and moderate temperature differences?
7.   Why is the exchanger implemented in two parts?
8.   What makes demounting much easier?

Упражнение № 3.Переведите следующие слова словосочетания на русский язык.

The double pipe heat exchanger (n.), possibility (n.), counter flow, parallel flow, temperature (n.), conclude (v.), efficient (adj.), pipe (n.), fluid (n.), approach (v.), pass(v.), transfer (v.), explain (v.), in practice, advantage (n.), thermal force, consist of (v.), common (adj.), tubing (n.),  use (n.),  single (adj.), area (n.), lead (v.), relatively (adv.), low flow, rate (n.), moderate (adj.), temperature difference, straight (adj.), appear (v.),  hairpin construction, bundle construction, removable (adj.), bundle (n.) , ability (n.), handle (v.), differential (adj.), thermal expansion, implement (v.), nozzle (n.), freely (adv.), expand (v.), expansion joint, machinery (n.), superfluous (adj.), demounting (n.).

Служебные слова:

Quite, for, from, in any case, than, since, while, each other, but, as, due to, for, which.

Упражнение № 4. Переведите следующие слова и словосочетания на английский язык.

Двухтрубный теплообменник, сделать вывод (прийти к заключению),  передавать, преимущество, перепад температур (разница температур), температурные воздействия, претерпевать (подвергаться), съемный, тепловое расширение, U-образное конструкция, моноблочная конструкция (конст. состоящая из пучка труб), температурный трубный (сильфонный) компенсатор, трубопровод, форсунка, излишний (ненужный).

Упражнение № 5. Какие из перечисленных переводов являются ошибочными.

tubing	труба	nozzle	форсунка
handle	регулировать	removable	удалять
moderate	умеренный	lead	привести, вести
relatively	относительный	freely	свободный
advantage	недостаток	than	тогда
ability	свойство	consist of	состоять из

Упражнение № 6. Сопоставьте слово А с его определением В.

А

1.  approach;
2.  transfer;
3.  advantage;
4.  flow;
5.  nozzle;
6.  possibility;
7.  water;
8.  superfluous;
9.  practice;
10.  pipe.

В

1.  something that helps you to be more successful than others, or the state of having this;
2.  to move towards or nearer to someone or something;
3.  to move from one place to another, or to move something from one place to another;
4.  a smooth steady movement of liquid, gas, or electricity;
5.  a short tube, pipe etc to direct and control the stream of liquid or gas pouring out;
6.  more than is needed or wanted;
7.  a thing that may happen or be the case;
8.  a tube through which a liquid or gas flows;
9.  when you do a particular thing, often regularly, in order to improve your skill at it;
10.  the clear liquid without colour, smell, or taste that falls as rain and that is used for drinking, washing etc.

Упражнение № 7. Определите функцию глагола to have в следующих предложениях и переведите их на русский язык.

1.  They have two possibilities.
2.  In this case there has to be more transferred heat.
3.  The engineers have explained why in practice there is only counter flow in case of the double pipe heat exchangers.
4.  The clear liquid doesn’t have colour and smell.
5.  A liquid has flown through a tube.
6.  The engineers have made demounting much easier.
7.  They had to control the stream of liquid or gas pouring out.
8.  They will have suffered less thermal forces.

Упражнение № 8. Переведите предложения, обращая внимание на модальные глаголы.

1.  We can see the development of the temperatures.
2.  The engineers could easily conclude that the counter flow was in any case more efficient than the parallel flow.
3.  We must analyse the double pipe heat exchangers.
4.  Double pipe exchangers may consist of common water tubing.
5.  We must practice a lot.
6.  The use of the two single flow areas may lead to relatively low flow rates.
7.  Students must work hard.

Текст B

Shell-and-tube heat exchangers

Most liquid-to-liquid exchangers are shell and tube. They have many advantages. Due to the high flow rates and heat transfer rates this type is more suitable for most applications than a double pipe heat exchanger. However, due to the numerous parameters it is difficult to find an optimal design. The engineers can’t do exact calculations because of the intricate geometry. Also in use it leads to pressure drops that have to be compensated by the use of a pump. These are disadvantages.

Fig. 1.5: cross section of a shell-and-tube heat exchanger.

In figure 1.5 we can see the design of a standard shell-and-tube heat exchanger. It consists of a shell on the outside and tubes inside the shell. These are made of standard steel or wrought-iron pipe. Their thickness depends on the operation pressure. The tubes are attached on front and rear ends in tube sheets and by baffles. They are placed in order to redirect the shell fluid past the tubes to enhance heat transfer. The so-called channel covers gather on both ends the fluid in the tubes. The nozzles are the inlet and outlet ports in the shell.

Figure 1.6: Shell-and-tube-heat exchanger with one shell pass and one tube pass; cross- counterflow operation.

Differences in types of shell-and-tube heat exchangers are based on the flows inside the shell and tubes. In figure 1.6 we can see a heat exchanger with one shell flow pass and one tubes flow path. The baffles lead the shell flow in such a way along the tubes that this type is a cross flow device. So this type could be classified as a shell-and-tube-heat exchanger with one shell pass and one tube pass; cross-counter flow operation.

Ответьте на вопросы к тексту:

1.  What are the advantages of liquid-to-liquid exchangers?
2.  Why is it difficult to find an optimal design?
3.  What are the disadvantages of shell-and-tube heat exchangers?
4.  What does a standard shell-and-tube heat exchanger consist of?
5.  What are tubes inside the shell and a shell on the outside made of?
6.  How are the tubes placed?
7.  What are the nozzles?
8.  What are the differences in types of shell-and-tube heat exchangers based on?
9.  Describe a cross flow device?
10.  Why is it impossible to do exact calculations?

Упражнение № 1. Найдите в тексте глагол to have и определите его функцию.

Упражнение № 2. Найдите в тексте модальные глаголы, переведите их на русский язык.

Упражнение № 3. Переведите следующие слова и словосочетания на русский язык.

Shell-and-tube heat exchangers, intricate geometry, pressure drop, pump, wrought-iron pipe, tube sheet, baffle (n.), gather (n.), inlet port, outlet port.

Упражнение № 4. Найдите перевод слов списка А в списке В.

A	В	A	В
baffle	кожух	pressure	толщина
shell	усиливать, увеличивать	along	впускной канал
enhance	перегородка	wrought-iron pipe	вдоль
gather	присоединять, скреплять	attach	выпускной канал
outlet port	складка	thickness	трубная решетка
tube sheet	давление	inlet port	стальная сварная труба

Упражнение № 5. Назовите главные и второстепенные члены подчеркнутых в тексте  предложений и укажите части речи, которыми они выражены.