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Read the text: Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is a nuclear reactor. As is typical in all conventional thermal power stations the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity. As of 16 January 2013, the IAEA report there are 439 nuclear power reactors in operation operating in 31 countries. Nuclear power plants are usually considered to be base load stations, since fuel is a small part of the cost of production. Electricity was generated by a nuclear reactor for the first time ever on December 20, 1951 at the EBR-I experimental station near Arco, Idaho in the United States. On June 27, 1954, the world's first nuclear power plant to generate electricity for a power grid started operations at Obninsk, USSR. The world's first commercial scale power station, Calder Hall in England opened on October 17, 1956. The conversion to electrical energy takes place indirectly, as in conventional thermal power plants. The heat is produced by fission in a nuclear reactor (a light water reactor). Directly or indirectly, water vapor (steam) is produced. The pressurized steam is then usually fed to a multi-stage steam turbine. Steam turbines in Western nuclear power plants are among the largest steam turbines ever. After the steam turbine has expanded and partially condensed the steam, the remaining vapor is condensed in a condenser. The condenser is a heat exchanger which is connected to a secondary side such as a river or a cooling tower. The water is then pumped back into the nuclear reactor and the cycle begins again. The water-steam cycle corresponds to the Rankine cycle. A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. The most common use of nuclear reactors is for the generation of electric energy and for the propulsion of ships.
The nuclear reactor is the heart of the plant. In its central part, the reactor core's heat is generated by controlled nuclear fission. With this heat, a coolant is heated as it is pumped through the reactor and thereby removes the energy from the reactor. Heat from nuclear fission is used to raise steam, which runs through turbines, which in turn powers either ship's propellers or electrical generators.
Since nuclear fission creates radioactivity, the reactor core is surrounded by a protective shield. This containment absorbs radiation and prevents radioactive material from being released into the environment. In addition, many reactors are equipped with a dome of concrete to protect the reactor against both internal casualties and external impacts. In nuclear power plants, different types of reactors, nuclear fuels, and cooling circuits and moderators are used.
Steam turbine. The purpose of the steam turbine is to convert the heat contained in steam into mechanical energy. The engine house with the steam turbine is usually structurally separated from the main reactor building. It is so aligned to prevent debris from the destruction of a turbine in operation from flying towards the reactor. In the case of a pressurized water reactor, the steam turbine is separated from the nuclear system. To detect a leak in the steam generator and thus the passage of radioactive water at an early stage is the outlet steam of the steam generator mounted an activity meter. In contrast, boiling water reactors and the steam turbine with radioactive water applied and therefore part of the control area of the nuclear power plant.
Electric generator: The generator converts kinetic energy supplied by the turbine into electrical energy. Low-pole AC synchronous generators of high rated power are used.
Cooling system A cooling system removes heat from the reactor core and transports it to another area of the plant, where the thermal energy can be harnessed to produce electricity or to do other useful work.Typically the hot coolant is used as a heat source for a boiler, and the pressurized steam from that boiler powers one or more steam turbine driven electrical generators.
Safety valves
In the event of an emergency, two independent safety valves can be used to prevent pipes from bursting or the reactor from exploding. The valves are designed so that they can derive all of the supplied flow rates with little increase in pressure. In the case of the BWR, the steam is directed into the condensate chamber and condenses there. The chambers on a heat exchanger are connected to the intermediate cooling circuit.
Feedwater pump
The water level in the steam generator and nuclear reactor is controlled using the feedwater system. The feedwater pump has the task of taking the water from the condensate system, increasing the pressure and forcing it into either the Steam Generators (Pressurized Water Reactor) or directly into the reactor vessel (Boiling Water Reactor).
Emergency power supply
The emergency power supplies of a nuclear power plant are built up by several layers of redundancy, such as diesel generators, gas turbine generators and battery buffers. The battery backup provides uninterrupted coupling of the diesel/gas turbine units to the power supply network. If necessary, the emergency power supply allows the safe shut down of the nuclear reactor. Less important auxiliary systems such as, for example, heat tracing of pipelines are not supplied by these back ups. The majority of the required power is used to supply the feed pumps in order to cool the reactor and remove the decay heat after a shut down.
After text activity
I. Reading exercises:
Exercise 1. Read and memorize using a dictionary:
| IAEA (International Atomic Energy Agency); the EBR-I (Experimental Breeder Reactor I); load stations; a light water reactor; a multi-stage steam turbine; thereby; protective shield; a dome of concrete; casualties; align; debris; the outlet steam; an activity meter; in contrast; low-pole AC synchronous generators; safety valves; bursting; exploding; a heat exchanger; feedwater pump; Emergency power supply; redundancy; battery buffers; battery backup; uninterrupted; shut down; |
Exercise 2. Answer the questions:
1) What is a nuclear power plant?
2) How is the heat produced?
3) What doesa cooling system remove?
4) How is the water level in the steam generator and nuclear reactor controlled?
Exercise 3. Match the left part with the right:
| 1. Electricity was generated by a nuclear reactor for the first time | a).to initiate and control a sustained nuclear chain reaction |
| 2. A nuclear reactor is a device | b) ever on December 20, 1951. |
| 3. In the case of a pressurized water reactor, | c) are connected to the intermediate cooling circuit. |
| 4. The chambers on a heat exchanger | d) the steam turbine is separated from the nuclear system. |
Exercise 4. Open brackets choosing the right words:
Since nuclear (fission/splitting) creates radioactivity, the reactor (core/centre) is surrounded by a protective shield. This containment (absorbs/ejects) radiation and prevents radioactive material from being released into the environment. In addition, many reactors are (equipped /furnished), with a dome of concrete to protect the reactor against both internal casualties and external impacts. In nuclear power plants, (different/various) types of reactors, nuclear fuels, and cooling circuits and moderators are used.
THE SPEAKING MODULE
II. Speaking exercises:
Exercise 1. Learn the definitions: Nuclear power plant; nuclear reactor; reactor core; safety valve; generator.
| Nuclear power plantis a thermal power station in which the heat source is a nuclear reactor. |
| Nuclear reactor -a device used to generate power, in which nuclear fission takes place as a controlled chain reaction, producing heat energy that is generally used to drive turbines and provide electric power. Nuclear reactors are used as a source of power in large power grids and in submarines. |
| Reactor core -nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place. |
| Safety valve -a valve in a pressure container, as in a steam boiler, that automatically opens when pressure reaches a dangerous level. |
| Generator- an apparatus in which vapor or gas is formed from a liquid or solid by means of heat or chemical process, as a steam boiler, gas retort, or vessel for generating carbonic acid gas, etc. An electromechanical device that converts mechanical energy to electrical energy (usually direct current). |
Exercise 2. Ask questions to the given answers:
1) Question: ___________________________________________?
Answer: In the event of an emergency, two independent safety valves can be used to prevent pipes from bursting or the reactor from exploding.
Question: __________________________________________?
Answer: The water level in the steam generator and nuclear reactor is controlled using the feed water system.
Question: ___________________________________________?
Answer: The purpose of the steam turbine is to convert the heat contained in steam into mechanical energy.
THE WRITING MODULE
III. Writing exercises:
Exercise 1. Complete the sentences with the suggested words: radioactivity; surrounded; absorbs; in addition; to protect; casualties; different.
Since nuclear fission creates 1, the reactor core is 2 by a protective shield. This containment 3 radiation and prevents radioactive material from being released into the environment. 4, many reactors are equipped with a dome of concrete 5 the reactor against both internal 6 and external impacts. In nuclear power plants, 7 types of reactors, nuclear fuels, and cooling circuits and moderators are used.
Exercise 2. Compose a story on one of the topics (up to 100 words):
“A nuclear power plant”
“The nuclear reactor”
“Cooling system”
Lesson 5
THE READING MODULE
Read the text: Gas turbines. Heat engines.
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between. Energy is added to the gas stream in the combustor, where fuel is mixed with air and ignited. In the high pressure environment of the combustor, combustion of the fuel increases the temperature. The products of the combustion are forced into the turbine section. There, the high velocity and volume of the gas flow is directed through a nozzle over the turbine's blades, spinning the turbine which powers the compressor and, for some turbines, drives their mechanical output. The energy given up to the turbine comes from the reduction in the temperature and pressure of the exhaust gas.
Energy can be extracted in the form of shaft power, compressed air or thrust or any combination of these and used to power aircraft, trains, ships, generators, or even tanks.
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance to the high temperature state. The working substance generates work in the "working body" of the engine while transferring heat to the colder "sink" until it reaches a low temperature state. During this process some of the thermal energy is converted into work by exploiting the properties of the working substance. The working substance can be any system with a non-zero heat capacity, but it usually is a gas or liquid.
In general an engine converts energy to mechanical work. Heat engines distinguish themselves from other types of engines by the fact that their efficiency is fundamentally limited by Carnot's theorem. Although this efficiency limitation can be a drawback, an advantage of heat engines is that most forms of energy can be easily converted to heat by processes like exothermic reactions (such as combustion), absorption of light or energetic particles, friction, dissipation and resistance. Since the heat source that supplies thermal energy to the engine can thus be powered by virtually any kind of energy, heat engines are very versatile and have a wide range of applicability.
Heat engines are often confused with the cycles they attempt to mimic. Typically when describing the physical device the term 'engine' is used. When describing the model the term 'cycle' is used.
In thermodynamics, heat engines are often modeled using a standard engineering model such as the Otto cycle. The theoretical model can be refined and augmented with actual data from an operating engine, using tools such as an indicator diagram. Since very few actual implementations of heat engines exactly match their underlying thermodynamic cycles, one could say that a thermodynamic cycle is an ideal case of a mechanical engine. In any case, fully understanding an engine and its efficiency requires gaining a good understanding of the (possibly simplified or idealized) theoretical model, the practical nuances of an actual mechanical engine, and the discrepancies between the two.
In general terms, the larger the difference in temperature between the hot source and the cold sink, the larger is the potential thermal efficiency of the cycle. On Earth, the cold side of any heat engine is limited to being close to the ambient temperature of the environment, or not much lower than 300 Kelvin, so most efforts to improve the thermodynamic efficiencies of various heat engines focus on increasing the temperature of the source, within material limits. The maximum theoretical efficiency of a heat engine (which no engine ever attains) is equal to the temperature difference between the hot and cold ends divided by the temperature at the hot end, all expressed in absolute temperature or Kelvin.
The efficiency of various heat engines proposed or used today ranges from 3 percent (97 percent waste heat) for the OTEC ocean power proposal through 25 percent for most automotive engines, to 45 percent for a supercritical coal-fired power station, to about 60 percent for a steam-cooled combined cycle gas turbine.
All of these processes gain their efficiency (or lack thereof) due to the temperature drop across them.
Heat engines can be characterized by their specific power, which is typically given in kilowatts per liter of engine displacement (in the U.S. also horsepower per cubic inch). The result offers an approximation of the peak-power output of an engine. This is not to be confused with fuel efficiency, since high-efficiency often requires a lean fuel-air ratio, and thus lower power density. Examples of everyday heat engines include the steam engine, the diesel engine, and the gasoline (petrol) engine in an automobile. A common toy that is also a heat engine is a drinking bird. Also the Stirling engine is a heat engine. All of these familiar heat engines are powered by the expansion of heated gases. The general surroundings are the heat sink, providing relatively cool gases which, when heated, expand rapidly to drive the mechanical motion of the engine.
After text activity
I. Reading exercises:
Exercise 1. Read and memorize using a dictionary:
| downstream turbine, upstream rotating compressor, shaft power, sink, exploit, heat capacity, a drawback, friction, dissipation, resistance, versatile, range of applicability, mimic, refine and augment; the practical nuances, discrepancies, in general terms; ambient temperature;automotive engine; peak-power output; fuel-air ratio; Stirling engine. |
Exercise 2. Answer the questions:
1. What is a gas turbine?
2. What is a heat engine in thermodynamics and what does it perform?
3. How do heat engines distinguish themselves from other types of engines?
4.What examples of everyday heat engines do you know?
Exercise 3. Match the left part with the right:
| 1.A gas turbine, also called a combustion turbine, | a) the reduction in the temperature and pressure of the exhaust gas. |
| 2.The energy given up to the turbine comes from | b) is a type of internal combustion engine. |
| 3.A heat "source" generates thermal energy | c) which is typically given in kilowatts per liter of engine displacement. |
| 4.Heat engines can be characterized by their specific power, | d) that brings the working substance to the high temperature state. |
Exercise 4. Open brackets choosing the right words:
The products of the combustion are forced into the turbine (section/area). There, the high velocity and volume of the gas flow is (directed/ conducted) through a nozzle (over/above) the turbine's blades, spinning the turbine which powers the compressor and, for some turbines, (drives/operates) their mechanical output. The energy given up to the turbine comes from the (reduction/degradation) in the temperature and pressure of the exhaust gas.
THE SPEAKING MODULE
II. Speaking exercises:
Exercise 1. Learn the definitions: Internal combustion engine; fuel; fossil fuel; thermodynamics; heat engine; diesel engine.
| Internal combustion engine -an engine of one or more working cylinders in which the process of combustion takes place within the cylinders. |
| Fuel - material such as coal, gas, or oil that is burned to produce heat or power. |
| Fossil fuels -a natural fuel such as coal or gas, formed in the geological past from the remains of living organisms. |
| Thermodynamics-the branch of physical science concerned with the interrelationship and interconversion of different forms of energy and the behavior of macroscopic systems in terms of certain basic quantities, such as pressure, temperature, etc. |
| Heat engine -an engine that converts heat energy into mechanical energy. |
| Diesel engine - an internal-combustion engine that burns heavy oil. |
Exercise 2. Ask questions to the given answers:
2) Question: ___________________________________________?
Answer: Energy is added to the gas stream in the combustor, where fuel is mixed with air and ignited.
Question: __________________________________________?
Answer: The products of the combustion are forced into the turbine section.
Question: ___________________________________________?
Answer: Heat engines are often confused with the cycles they attempt to mimic.
THE WRITING MODULE
III. Writing exercises:
Exercise 1. Complete the sentences with the suggested words: heat engines; toy; familiar; heat sink, motion.
Examples of everyday 1 include the steam engine, the diesel engine, and the gasoline (petrol) engine in an automobile. A common 2 that is also a heat engine is a drinking bird. Also the Stirling engine is a heat engine. All of these 3 heat engines are powered by the expansion of heated gases. The general surroundings are the 4, providing relatively cool gases which, when heated, expand rapidly to drive the mechanical 5 of the engine.
Exercise 2. Compose a story on one of the topics (up to 100 words):
“Gas turbine”
“Heat engines”
Lesson 6
Read the text: Boilers. Boiler Types and Classifications
A gas/oil central heating boiler (heat generator) is like the engine of a car, this provides the heat that the facility needs to warm itself up. The size of the boiler is matched to the size of the facility.
The ideal size for a boiler is one that just copes adequately on the coldest day of the year. Most boilers are oversized by at least 30%. This is due to the way systems used to be calculated with a card calculator. These were always over-calculated "to be on the safe side." Today, the emphasis is on energy conservation, and the fact that heat loss calculations can be done very accurately, means there is no need to oversize. This allows smaller radiators and less water in the system, which in turn, means a smaller boiler and reduced costs for both installation and fuel bills.
The boiler does not directly govern the amount of radiators fitted to the system. It is the power of the pump and circulation of the water through adequately sized pipes that determines the number of radiators you can have. But the total output of all the radiators, pipes, and cylinders determines the size of the boiler.
The boiler is not the heating system; it is only one of the parts in the global heating system. A heating system consists of four main parts:
There are two general types of boilers: ''fire-tube'' and ''water-tube''. Boilers are classified as "high-pressure" or "low-pressure" and "steam boiler" or "hot water boiler." Boilers that operate higher than 15 psig are called "high-pressure" boilers.
A hot water boiler, strictly speaking, is not a boiler. It is a fuel-fired hot water heater. Because of its similarities in many ways to a steam boiler, the term ''hot water boiler'' is used.
Heating boilers are also classified as to the method of manufacture, i.e., by casting (cast iron boilers) or fabrication (steel boilers). Those that are cast usually use iron, bronze, or brass in their construction. Those that are fabricated use steel, copper, or brass, with steel being the most common material.
''Steel boilers''' are generally divided into two types: ''fire- tube'' and ''water-tube''.
Fire-tube Boilers
In fire-tube boilers, combustion gases pass through the inside of the tubes with water surrounding the outside of the tubes. The advantages of a fire-tube boiler are its simple construction and less rigid water treatment requirements.
The disadvantages are the excessive weight-per-pound of steam generated, excessive time required to raise steam pressure because of the relatively large volume of water, and inability to respond quickly to load changes, again, due to the large water volume.
The most common fire-tube boilers used in facility heating applications are often referred to as ''scotch'' or ''scotch marine'' boilers, as this boiler type was commonly used for marine service because of its compact size (fire-box integral with boiler section).
The name "fire-tube" is very descriptive. The fire, or hot flue gases from the burner, is channeled through tubes that are surrounded by the fluid to be heated. The body of the boiler is the pressure vessel and contains the fluid. In most cases, this fluid is water that will be circulated for heating purposes or converted to steam for process use.
Every set of tubes that the flue gas travels through, before it makes a turn, is considered a "pass." So, a three-pass boiler will have three sets of tubes with the stack outlet located on the rear of the boiler. A four-pass boiler will have four sets and the stack outlet at the front.
Fire-tube boilers are:
Disadvantages of fire-tube boilers include:
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