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Natural Circulation Boiler
In a natural circulation boiler the circulation is achieved by the difference in density when the water in the boiler is heated. In natural circulation steam boilers the circulation of water is by convection currents, which are set up during the heating of water. In most of the boilers there is a natural circulation of water the fundamental principle of which is based on the principle of Thermosiphon Thermosiphon (or thermosyphon) is a method of passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump. Thermosiphoning is used for circulation of liquids and volatile gases in heat .... See also * Controlled circulation * Forced circulation boiler * Once through steam generator Boilers {{Mech-engineering-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circulation (fluid Dynamics)
In physics, circulation is the line integral of a vector field around a closed curve. In fluid dynamics, the field is the fluid velocity field. In electrodynamics, it can be the electric or the magnetic field. Circulation was first used independently by Frederick Lanchester, Martin Kutta and Nikolay Zhukovsky. It is usually denoted Γ (Greek uppercase gamma). Definition and properties If V is a vector field and dl is a vector representing the differential length of a small element of a defined curve, the contribution of that differential length to circulation is dΓ: :\mathrm\Gamma=\mathbf\cdot \mathrm\mathbf=, \mathbf, , \mathrm\mathbf, \cos \theta. Here, ''θ'' is the angle between the vectors V and dl. The circulation Γ of a vector field V around a closed curve ''C'' is the line integral: :\Gamma=\oint_\mathbf\cdot \mathrm d \mathbf. In a conservative vector field this integral evaluates to zero for every closed curve. That means that a line integral between any two ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematically, density is defined as mass divided by volume: : \rho = \frac where ''ρ'' is the density, ''m'' is the mass, and ''V'' is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight. For a pure substance the density has the same numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity and packaging. Osmium and iridium are the densest known elements at standard conditions for temperature and pressure. To simplify comparisons of density across different s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boiler
A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation. Heat sources In a fossil fuel power plant using a steam cycle for power generation, the primary heat source will be combustion of coal, oil, or natural gas. In some cases byproduct fuel such as the carbon monoxide rich offgasses of a coke battery can be burned to heat a boiler; biofuels such as bagasse, where economically available, can also be used. In a nuclear power plant, boilers called steam generators are heated by the heat produced by nuclear fission. Where a large volume of hot gas is available from some process, a heat recovery steam generator or recovery boiler can use the heat to produce steam, with little or no extra fuel consumed; such a configuration is common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convection Currents
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convection is unspecified, convection due to the effects of thermal expansion and buoyancy can be assumed. Convection may also take place in soft solids or mixtures where particles can flow. Convective flow may be transient (such as when a multiphase mixture of oil and water separates) or steady state (see Convection cell). The convection may be due to gravitational, electromagnetic or fictitious body forces. Heat transfer by natural convection plays a role in the structure of Earth's atmosphere, its oceans, and its mantle. Discrete convective cells in the atmosphere can be identified by clouds, with stronger convection resulting in thunderstorms. Natural convection also plays a role in stellar physics. Convection is often categorised or des ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermosiphon
Thermosiphon (or thermosyphon) is a method of passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump. Thermosiphoning is used for circulation of liquids and volatile gases in heating and cooling applications such as heat pumps, water heaters, boilers and furnaces. Thermosiphoning also occurs across air temperature gradients such as those utilized in a wood fire chimney or solar chimney. This circulation can either be open-loop, as when the substance in a holding tank is passed in one direction via a heated transfer tube mounted at the bottom of the tank to a distribution point—even one mounted above the originating tank—or it can be a vertical closed-loop circuit with return to the original container. Its purpose is to simplify the transfer of liquid or gas while avoiding the cost and complexity of a conventional pump. Simple thermosiphon Natural convection of the liquid starts when heat transfer to the liquid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Controlled Circulation
A magazine is a periodical publication, generally published on a regular schedule (often weekly or monthly), containing a variety of content. They are generally financed by advertising, purchase price, prepaid subscriptions, or by a combination of the three. Definition In the technical sense a ''journal'' has continuous pagination throughout a volume. Thus '' Business Week'', which starts each issue anew with page one, is a magazine, but the '' Journal of Business Communication'', which continues the same sequence of pagination throughout the coterminous year, is a journal. Some professional or trade publications are also peer-reviewed, for example the '' Journal of Accountancy''. Non-peer-reviewed academic or professional publications are generally ''professional magazines''. That a publication calls itself a ''journal'' does not make it a journal in the technical sense; ''The Wall Street Journal'' is actually a newspaper. Etymology The word "magazine" derives from Arabic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forced Circulation Boiler
A forced circulation boiler is a boiler where a pump is used to circulate water inside the boiler. This differs from a natural circulation boiler which relies on current density to circulate water inside the boiler. In some forced circulation boilers, the water is circulated twenty times the rate of evaporation. In water tube boilers, the way the water is recirculated inside the boiler before becoming steam can be described as either natural circulation or forced circulation. In a water tube boiler, the water is recirculated inside until the vapor pressure of the water overcomes the vapor pressure inside the stream drum and becomes saturated steam. The forced circulation boiler begins the same as a natural circulation boiler, at the feed water pump. Water is introduced into the steam drum and is circulated around the boiler, leaving only as steam. What makes the forced circulation boiler different is its use of a secondary pump that circulates water through the boiler. The secondar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Once Through Steam Generator
A heat recovery steam generator (''HRSG'') is an energy recovery heat exchanger that recovers heat from a hot gas stream, such as a combustion turbine or other waste gas stream. It produces steam that can be used in a process (cogeneration) or used to drive a steam turbine (combined cycle). HRSGs HRSGs consist of four major components: the economizer, evaporator, superheater and water preheater . The different components are put together to meet the operating requirements of the unit. See the attached illustration of a Modular HRSG General Arrangement. Modular HRSGs can be categorized by a number of ways such as direction of exhaust gases flow or number of pressure levels. Based on the flow of exhaust gases, HRSGs are categorized into vertical and horizontal types. In horizontal type HRSGs, exhaust gas flows horizontally over vertical tubes whereas in vertical type HRSGs, exhaust gas flow vertically over horizontal tubes. Based on pressure levels, HRSGs can be categorized into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
