2018-02-14
1549
UNIT VIII
Exercise I. Make sure you pronounce the following words correctly:
Cylinder, shell, corrugated furnace, chamber, circumferential, collapse, hazard.
FIRE-TUBE BOILERS
A fire-tube or Scotch boiler is a boiler in which the water is outside the tube and the hot gases pass through the tube.
Fire-tube boilers generally consist of a cylindrical shell; they are internally fired, and are fitted with corrugated furnaces and return-tube fire tubes. These boilers are both single- and double-end type, usually having two or more furnaces in each end, either with one combustion chamber for each furnace or with a single combustion chamber serving several furnaces.
Furnaces are cylindrical shells with circumferential corrugations to afford strength against collapse and to provide for expansion. With oil fuel, burners are applied by means of a suitable furnace behind which refractory is placed. If coal fuel is used, grates are placed approximately on the horizontal centre of the furnace. To direct air through the fuel bed a wall is erected at the rear of the grates.
The purpose of the combustion chamber is to allow combustion to be completed and to distribute the flue gases to the tubes.
The advantages of a fire-tube boiler are easy maintenance and repair, ability to use feed water of doubtful quality, and adaptability to practically any fuel. As for disadvantages, they require large quantities of boiler water, are heavy and bulky, cannot raise steam quickly, and are extremely hazardous, if damaged, due to the large quantities of water and steam contained in the shells.
Exercise II. Translate the following attributive groups into Russian:
Return-tube fire tubes, double-end type boiler, single combustion chamber, combustion chamber work, flue gases distribution, oil fuel burner application, maintenance and repair expenses.
Exercise III. Form nouns from the following words. Find them in the text.
a) strong b) able c) to adapt d) to expand e) to maintain f) to repair g) to collapse
Exercise IV. Complete the sentences according to the text:
1) Fire-tube boilers consist of … 2) Double-end type boilers have two or more … 3) Furnaces are cylindrical shells with … 4) The purpose of the combustion chamber is …
Exercise V. Complete the sentences inserting the “-ed” or “-ing” form of the verbs in brackets:
1) Fire-tube boilers are easily … (maintain). 2) Fire-tube boilers can be extremely dangerous because of large quantities of water and steam …in the shells. (contain) 3) The tubes …water are usually installed underground. (contain)
4) This type of boilers is fitted with …furnaces. (corrugate) 5) District … plants can provide greater efficiency. (heat) 6) The water … up to 100ºC evaporates. (heat) 7) In a cogeneration plant, heat and electricity are ……. simultaneously. (generate)
Exercise VI. Make questions about fire-tube boilers to which the following sentences are the answers. Model: … … …? – Hot gases. (What is inside the boiler tubes?)
1) … … …? - A cylindrical shell, corrugated furnaces, fire tubes and combustion chambers. 2) … … …? - Circumferential corrugation is necessary to afford strength against collapse and to provide for expansion.
3) … … …? - At the rear of the grates.
4) … … …? - To distribute the flue gases to the tubes.
5) … … …? - Easy maintenance and adaptability to any water quality and any fuel.
Exercise VII. Working in pairs, role-play a conversation in which an engineer explains the advantages and disadvantages of a fire-tube boiler.
Exercise VIII. Read the following text without a dictionary and speak about the development of heating systems in the world.
District heating in the world
In most Russiancities, district combinedheatandpower plants (ТЭЦ, теплоэлектроцентраль) produce more than 50 % of the nation's electricity and simultaneously provide hot water for city blocks. They mostly use coal and oil-powered steamturbines for cogeneration of heat. Now, gasturbines and combined cycle designs are beginning to be widely used as well. A Soviet-era approach of using very large central stations to heat large districts of a big city or entire small cities is fading away as inefficient, much heat being lost in the piping network because of leakages and lack of proper thermal insulation.
In the United Kingdom, district heating became popular after World War II. Today, the UK government is actively supporting combined heat and power. To achieve a 60% reduction in carbon dioxide emissions, the government encourages cogeneration financially and legally. Denmark, the Netherlands and Finland have the world’s most intensive cogeneration economies.
As a whole, the European Union currently generates 11% of its electricity using cogeneration saving Europe from 2% to 60% of energy.
UNIT IX
Exercise I. Make sure you pronounce the following words correctly:
Circulate, header, longitudinal, evaporation, feature, pure, flexibility, rupture
WATER-TUBE BOILERS
Water-tube boilers are different from fire-tube boilers in that the water circulates through the boiler tubes instead of surrounding them on the outside.
Water-tube boilers may be classified in respect of the arrangement of the water tubes, as straight-tube, bent-tube or coil-tube types; with respect to the number of their water and steam drums or headers, as single-drum, two-drum, three-drum, etc., and with respect to the arrangement of the drums or headers, as cross or lateral-drum or longitudinal-drum types.
Boilers that have coils for water tubes or tubes which lie almost horizontal are said to have limited circulation, because the only circulation is that caused by the evaporation of the water.
The strong features of the water-tube boiler, as compared with the fire-tube types, are saving in weight, the possibility of using high pressure and temperatures, greater mechanical flexibility, rapid steam raising, saving in space, safety in the event of serious rupture, due to smaller water contents. The failure of a single part will not cause an explosion or any damage beyond the damage to that part.
Their more undesirable limitations are that their operation requires a greater degree of skill and engineering knowledge, and that they require for operation only pure, fresh water.
Exercise II. Translate the following attributive groups into Russian.
Water-tube boiler operation, different tube arrangement types, water and steam drums contents, space and weight saving costs, horizontal tubes water circulation limitations, greater engineering knowledge requirements.
Exercise III. Change parts of the words to form their antonyms:
1) internal 2) suitable 3) doubtful 4) ability 5) practical 6) advantage 7) to place 8) to use 9) complete 10) outside
Exercise IV. Translate the sentences paying attention to the underlined words:
in terms of – с точки зрения, что касается; instead of – вместо; in respect of, with respect to – что касается; compared with, compared to – по сравнению; result in – приводить к
1) The advantage of a fire-tube boiler is that low quality water can be used instead of pure water. 2) In terms of efficiency, a cogeneration plant recovers wasted industrial energy in the form of heat. 3) With respect to the number of furnaces, fire-tube boilers can be single and double-end types. 4) In a heat distribution system, steam can be used instead of water. 5) Heat transfer oils are generally avoided in district heating in respect of environmental issues. 6) Interms of maintenance and repair, water-tube boilers require high skills and engineering knowledge. 7) Compared with fire-tube boilers, water-tube boilers have a greater degree of safety and flexibility. 8) The invention of non-toxic and non-flammable synthetic refrigerants resulted in a wide acceptance of refrigerators first in the USA, later in Europe.
Exercise V. Translate the following sentences.
1) It is required that pure, fresh water should be used in water-tube boilers. 2) District heating systems use the heat which would be dispersed to the environment. 3) Pimlico District Heating Plant would often break down before 1950 when its modernisation started. 4) If we used more efficient energy conservation systems, CO² emissions would be reduced. 5) Solar energy would be difficult to exploit in the countries with severe climates. 6) The Sun’s rays should be employed to supply hot water or to generate electricity. 7) The construction engineers suggested that the old radiators should be replaced with a hot water under-floor heating system.
Exercise VI. Make up questions to which the following sentences are answers, according to the text.
1) … … …? - Three types in terms of the water tube arrangement, the number of drums and the drums arrangement. 2) … … …? - Because the circulation is caused by the evaporation of water only. 3) … …. …? - Weight and space saving, mechanical flexibility, high pressure possibility and safety. 4) … … …? - Pure, fresh water only.
Exercise VII. Translate the following sentences paying attention to the “ed-forms”:
1) A district heating system is typically based on combustion of fuel. 2) The heat distributed to this block of flats is provided by a local heating boiler station. 3) If damaged, a fire-tube boiler can be extremely dangerous. 4) When used with care, a refrigerator has a long life span. 5) Where required by law, the engineers specify the HVAC systems and speciality mechanical contractors build and install them. 6) The feed water heated circulated in the tubes thus distributing the heat.
Exercise VIII. Working in pairs, role-play a conversation where two engineers discuss the advantages and disadvantages of water-tube boilers and fire-tube boilers. Decide which ones are preferable in boiler stations.
Exercise IX. Read the following text without a dictionary. Give the main idea of the text. Name at least three ways in which we can cut our energy costs and reduce environmental emissions.
