Chapter 3

Ex.1 Give Russian equivalents of the following words. Use the dictionary if it is necessary.

Uniform-uniforming-uniformity-uniformly; general- generally- generate- generation; change-exchange-exchanging; radiant-radiation-radiate-radiator; effective-effect- ineffectively- efficiency; refrigerate- refrigerator- refrigeration-refrigerated; condition- conditioner- conditioning; differ-difference- differentiate-different.

Ex.2 Read and memorize the words and word combinations.

heat exchange	теплообмен
spontaneous	самопроизвольный
irreversible	необратимый
nature	характер, природа
non-uniform	неоднородный
diffusion thermo effect	диффузный тепловой эффект
mass exchange	массообмен
counterflow	встречное течение, противоток
log mean temperature difference	разность средних температур, определённая при температурном каротаже
contend (with)	спорить
shell and tube	кожухо-трубный (теплообменник)
extruded finned pipe	экструдированная ребристая трубка
spiral fin pipe	спиральная ребристая трубка
u-tube	двухколенчатая сифонная труба
stacked plate	многоуровневая пластина

Ex.3 Read and translate the text.

Heat exchange

Heat exchange is a spontaneous irreversible process of heat transfer in space stipulated by non-uniform temperature field. Generally, heat transfer can result from non-uniform nature of fields of other physical quantities, such as difference of concentrations (so-called diffusion thermo effect). There exist 3 types of heat exchange: conduction, convection and radiation. In practice, heat exchange is produced by these three processes at the same time. Different natural processes are defined and followed by heat exchange (e.g., evolution of stars and planets, meteorological processes on the Earth surface etc.).This also concerns engineering processes and our everyday life. In drying, evaporation cooling, diffusion heat exchange is analyzed together with mass exchange.

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. Heat exchangers are widely used in refrigeration, air conditioning, space heating, power generation, and chemical processing. One common example of a heat exchanger is the radiator in a car, in which the hot radiator fluid is cooled by the flow of air over the radiator surface.

Common types of heat exchanger flows include parallel flow, counter flow, and cross flow. In parallel flow, both fluids move in the same direction while transferring heat; in counter flow, the fluids move in opposite directions and in cross flow the fluids move at right angles to each other. The common constructions for heat exchanger include shell and tube, double pipe, extruded finned pipe, spiral fin pipe, u-tube, and stacked plate.

When engineers calculate the theoretical heat transfer in a heat exchanger, they must contend with the fact that the driving temperature difference between the two fluids varies with position. To account for this in simple systems, the log mean temperature difference (LMTD) is often used as an 'average' temperature. In more complex systems, direct knowledge of the LMTD is not available and the number of transfer units (NTU) method can be used instead.

Ex.4 Answer question about the text.

1. What is heat exchange as a process? 2. What does it result from? 3. What three types of heat exchange do you know? 4. In what processes does heat exchange take part? 5. What is a heat exchanger? 6. Where is it applied? 7. Can you give any examples of heat exchangers? 8. What is a construction of heat exchanger? 9. What parameter should engineers take into account, when they calculate the theoretical heat transfer in a heat exchanger?

Ex.5 Make up 5 sentences of your own using the following expressions.

Driving temperature difference; to vary with position; heat exchanger; counter flow; physical quantities.

Ex.6 Choose the right word or word combination from the list. Complete the sentences and translate them.

Widely used; constructions; contend with the fact; heat exchange; are defined and followed; conduction; flows; convection and radiation.

1. _________ is a spontaneous irreversible process of heat transfer in space stipulated by non-uniform temperature field. 2. There exist 3 types of heat exchange:___________ 3. Evolution of stars and planets, meteorological processes on the Earth surface by heat exchange. 4. Heat exchangers are___________ in refrigeration, air conditioning, space heating, power generation, and chemical processing. 5. Common types of heat exchanger___________ include parallel flow, counter flow, and cross flow. 6. The common___________ for heat exchanger include shell and tube, double pipe, extruded finned pipe, spiral fin pipe, u-tube, and stacked plate. 7. Engineers must___________ that the driving temperature difference between the two fluids varies with position.

Ex.7 Translate the sentences into English using the active vocabulary.

1.Все ветры в атмосфере представляют собой конвекционные потоки огромного масштаба. 2. Одним из способов регулирования температуры тела является теплообмен за счёт конвективного охлаждения кожи. 3. При большой разности давлений и температур основной теплообмен внутри Земли осуществляется за счёт конвекции. 4.Используется ли конвекция в конструкции мельниц, ветродвигателей, вытяжных труб, систем отопления помещений? 5. Такие изобретения, как термос и теплица, основаны на использовании теплообмена.

Ex.8 Give the Russian for the –ed-forms. Use these expressions in sentences of your own.

Followed by heat exchange; stipulated by non-uniform temperature field; analyzed together with mass exchange; stimulated process; constructed for efficient heat transfer; widely used; cooled by the flow of air.

Ex.9 In multiple choice questions, you have to choose the answer that you think is right from several possible answers that are listed below.

1. Convection is:

– a type of heat transfer followed by a mass transfer;

– a type of heat transfer in vacuum;

– a type of heat transfer in solid substances;

– a process of transformation of matter from one aggregative state into another.

2. Heat exchange is:

–stimulated, reversible process of heat transfer from worm bodies to cold ones;

– one of different types of heat transfer;

– a spontaneous irreversible process of heat transfer from a hotter object to a cooler object;

– a process of transformation of matter from one aggregative state into another.

3. Thermal conductivity is:

– a type of heat transfer followed by mass transfer;

– energy transfer from hotter bodies to cooler ones;

– energy transfer from cooler bodies to hotter ones;

– a type of heat transfer which takes place in liquids and gases.

4. Heat is:

– a quantity of energy taken or given by a body in the process of heat transfer;

– temperature characteristic of a body;

– one of the aggregate states of a body;

– a form of matter.

5. Radiation is:

– a type of heat transfer taking place only in solid bodies;

– energy transfer from cooler bodies to hotter ones;

– a process of transformation of matter from one aggregate state into another;

– a type of heat transfer.

Ex.10 Retell the text “Heat exchange”.