A low-pressure hot-water system



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A low-pressure hot-water system



A low-pressure hot-water system is described below. Water in the boiler is heated, and consequently becomes less dense than the cold water in the higher parts of the system. The denser cold water sinks to displace the heated water, which is forced to rise. In this way, a circulation of water is set up-the process known as convection. The water rises up the primary flow (PF) into the hot-water storage cylinder, or tank, and is replaced by water descending the primary return (PR). If a temperature difference is maintained between the water in the primary flow and that in the primary return, then the process will continue. This is called the primary circulation and it is made more effective by connecting the primary flow to the upper region of both the boiler and the cylinder, and the primary return to the lower region of each. If a draw-off point is opened, water will be forced from it because of the height of the water in the feed tank (often this tank is also the building's main cold-water storage cistern). The hot-water supply is drawn from the top of the storage cylinder, where it collects because its density is lower than that of the colder water.

Heating water causes the dissolved air contained in cold water to be released. Consequently, a vent pipe has to be taken from the top of the storage cylinder and carried up above the level of the water in the feed tank. The pipe allows air to escape from the system and, as a result, prevents the formation of air locks.

A safety valve, set to operate at a certain pressure, is fitted to the system. Also, a draw-off point is fitted at the lowest part of the system so that it can be drained.

 

Exercise 1.

What’s the English for:


система водяного опалення низького тиску

щільний

опускати, осідати

конвекція

підніматися

прямий стояк

акумуляційний циліндр

опускатися

зворотній стояк

зливний кран

витратний бак

випаровуватися

випускати

вентиляційний канал

повітряна пробка

спускати воду


 

Exercise 2

Give the Ukrainian equivalents for the following English word–combinations:

a circulation of water, escape from the system, primary flow, becomes less dense, if a draw – off point is opened, cold water sinks, above the level of water, connect the primary flow to the upper region, in this way, heating water causes, prevents the formation of air locks, a safety valve.

 

Exercise 3.

What do the following abbreviations mean?

PR, PF, SV, W.C., H.W., B, C.W.

 

Exercise 4.

Answer the questions in English:

1. What is the function of the cold-water cistern?

2. Where on the cylinder is the primary flow connected? Why is it connected there?

3. How does heating affect cold water?

4. How can you stop the process of convection?

5. What causes water to be forced out of a draw-off point?

6. What is the most important function of the vent pipe?

7. If a safety valve is not fitted to the system, what might be the result?

 

Exercise 5.

Complete these sentences which describe how the low-pressure hot-water system works:

1. Water in the boiler is heated with the result that…

2. …is caused by the dense cold water sinking.

3. As a result of…water rises up the primary flow and is replaced by water descending the primary return.

4. …thereby continuing the process of convection.

5. The pressure at a draw-off point is due to…

6. Hot water has a lower density than cold water. Consequently …

7. The formation of air locks in the system is prevented by…

8. The operation of the safety valve results in…

9. …the system will drain.

 

 

Text 12

History of building materials

Words and word-combinations to be remembered:

to erect – зводити

to be intended for – призначатися

durable – довгочасний, міцний, надійний

fire proof – вогнетривкий

heat conductivity – теплопровідність

binder – в’яжуча речовина

portland cement – портланд цемент

improvement – вдосконалення

compressive strength – робота на тиск

 

Read and translate the text:

History of building materials

All the buildings erected nowadays are of two main types: they are intended either for housing or industrial purposes.

The main building materials are timber, stone (brick), concrete, steel, light metals, glass and plastics. Timber was one of the first materials to be used by man for constructional purposes. It is highly probable that it will be one of the last. Timber is unique among the materials of construction. It will be available when the earth's capital deposits of iron, coal, clay and the rest have been consumed.

The buildings made of stone or brick are durable and fireproof, they have poor heat conductivity.

Concrete made with natural hydraulic binders was used in antiquity, particularly by the Romans. After the decline of the Roman Empire the art of making concrete has been forgotten, and the revival came much later.

Portland cement was produced more than a century ago. From the time of its first production there was a steady.

Reinforced concrete is hardly 100 years old, but its practical application. In building began only 90 years ago. Today reinforced concrete is used in all civilized countries as one of the most important building materials. One of the essential properties of concrete is its compressive strength.

 

Exercise 1.

What’s the English for:

зводити в’яжуча речовина

призначатися портланд цемент

довгочасний, міцний вдосконалення

вогнетривкий робота на стиск

теплопровідність

 

Exercise 2.

Answer the questions in English:

1. What are building intended for?

2. What are the main building materials?

3. When was Portland cement produced?

4. When was concrete first used?

5. What are the earth’s capital deposits?

 

Exercise 3.

Complete the following sentences according to the text:

1. All the buildings are intended … .

2. The main building materials are … .

3. … was one of the first materials to be used for construction.

4. The buildings made of … are durable and fireproof.

5. Concrete made with … was used in antiquity.

6. … was produced more than a century ago.

7. The practical application of … began only 90 years ago.

8. One of the essential properties of concrete is … .

 

Exercise 4.

Translate into Ukrainian paying attention to the word “one”:

1. To determine the density of a body one must know its mass and its volume.

2. Ductile materials have greater strength than brittle ones.

3. Copper is one of the metals used in the prehistoric times.

 

Exercise 5.

Use the following sentences in all forms and tenses adding suitable adverbial modifiers where necessary:

1. People employ glass for many purposes.

2. Iron is widely used as a building material.

 

 

Text 13

Cement

Words and word-combinations to be remembered:

to fulfill – виконувати, здійснювати

to a great extent – значною мірою

to obtain – одержувати, здобувати

finesse – дрібнозернистий

to grind – розтирати, молоти

dam – гребля, дамба

to retain – утримувати, підтримувати

advantageous – сприятливий, вигідний

selection – вибір, відбір

to ensure – забезпечувати, гарантувати

aggregate – агрегат

mix – суміш

 

Read and translate the text:

Cement

The requirements to be fulfilled by concrete vary to a great extent. One of the essential properties of concrete is its compressive strength. From the time of its first production more than a century ago there was a steady and gradual improvement in the compressive strength of Portland cement until the beginning of the war. With the cements now available much higher strengths can be obtained than some 40 or 50 years ago. The increase in strength is partly due to the increased fineness to which modern cements are ground.

Cement develops heat during hydration. This is of considerable importance in certain types of concrete construction, particularly in structures of large volume, such as dams, massive retaining walls and the like. A very high rate of heat development is advantageous in work done in cold weather, so as to protect the fresh concrete from the effect of low temperatures.

It should be noted, of course, that not all properties desired can be obtained in any one cement.

Selection of the cement alone does not ensure concrete with the properties desired, which depend also on the choice of aggregates and mixes, the control of the quantity of water added to the mix, and on a series of other factors

 

Exercise 1.

What’s the English for:

виконувати утримувати

значною мірою сприятливий

одержувати вибір

дрібнозернистий забезпечувати

розтирати агрегат

дамба, гребля суміш

 

Exercise 2.

Complete the following sentences according to the text:

1. One of the essential properties of concrete is … .

2. The increase in strength is partly due to … .

3. Cement develops … during hydration.

4. A very high rate of … is advantageous in work done in cold weather, so as to protect the fresh concrete from … .

5. The properties of cement depend on … .

 

Exercise 3.

Answer the questions in English:

1. What is one of the essential properties of concrete?

2. When was a steady and gradual improvement in the compressive strength of Portland cement?

3. What is the increase in strength due to?

4. What does cement develop during hydration?

5. Why is it so important in concrete construction?

6. What do the properties of cement depend on?

 

 

Text 14

Concrete.

Words and word-combinations to be remembered:

coarse aggregate- грубий заповнювач

fine aggregate- дрібний заповнювач

slab- плита

reinforcement- арматура, посилення

spalling- розтріскування, викришення

rib- виступ

spaced- розміщений з інтервалами

Read and translate the text:

Concrete.

Concrete is made from cement, coarse aggregate (stones), fine aggregate (sand or crushed stone) and water. Coarse aggregate ranging from 5 mm to 40 mm may be used for normal work. The maximum size of the aggregate should not be greater than one quarter of the minimum thickness of the finished concrete. The normal maximum sizes are 20 mm and 40 mm (20 mm being more common). The maximum size of aggregate which should be used in small concrete sections, or where reinforcement is close together, is 10 mm.

In concrete with widely spaced reinforcement, such as solid slabs, the size of the coarse aggregate should not be greater than the minimum cover to the reinforcement otherwise spalling will occur, i.e. the breaking off of pieces of concrete below the reinforcement. For heavily reinforced sections, e.g. the ribs of main beams, the maximum size of the coarse aggregate should be either:

- 5 mm less than the minimum horizontal distance between the reinforcing rods, or,

-5 mm less than the minimum cover to the reinforcement, whichever is the smaller.

 

Exercise 1

What’s the English for:

найбільший розмір не більший ніж

суцільна плита більш розповсюджений

розламуватись на куски найменша товщина

використаний відстань між

виготовлений з... буде відбуватись

 

Exercise 2

Give the Ukrainian equivalents for the following English words and word–combinations:

ranging from, otherwise, horizontal distance, below the reinforcement, sand, the ribs of main beams, should be used, finished concrete, quarter of the minimum thickness, the maximum size, close together.

Exercise3



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