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سطر 25:
[[ملف:Vlammen gasboiler.JPG|تصغير|يمين|[[شعلة]] [[غاز طبيعي]] بغلاية منزلية]]
يستخدم في الغلايات جميع أنواع [[وقود|الوقود]] كمصدر لل[[حرارة]] لتوليد البخار, بدءا من [[فحم|الفحم]] و[[خشب|الخشب]] والوقود [[نفط|النفط]]ي و[[الغاز الطبيعي]] وصولا إلى [[الانشطار النووي]].
==Superheated steam boiler==
[[Image:Superheater.jpg|thumb|300px|A superheated boiler on a steam locomotive.]]
{{main|Superheater}}
Most boilers produce steam to be used at [[saturation temperature]]; that is, saturated steam. Superheated steam boilers vaporize the water and then further heat the steam in a ''superheater''. This provides steam at much higher temperature, but can decrease the overall thermal efficiency of the steam generating plant because the higher steam temperature requires a higher flue gas exhaust temperature.{{cn|date=November 2015}} There are several ways to circumvent this problem, typically by providing an ''[[economizer]]'' that heats the feed water, a combustion air heater in the hot flue gas exhaust path, or both. There are advantages to superheated steam that may, and often will, increase overall efficiency of both steam generation and its utilization: gains in input temperature to a turbine should outweigh any cost in additional boiler complication and expense. There may also be practical limitations in using ''wet'' steam, as entrained condensation droplets will damage turbine blades.
Superheated steam presents unique safety concerns because, if any system component fails and allows steam to escape, the high pressure and temperature can cause serious, instantaneous harm to anyone in its path. Since the escaping steam will initially be completely superheated vapor, detection can be difficult, although the intense heat and sound from such a leak clearly indicates its presence.
Superheater operation is similar to that of the coils on an air conditioning unit, although for a different purpose. The steam piping is directed through the flue gas path in the boiler furnace. The temperature in this area is typically between {{convert|1300|and|1600|C|F|0|lk=on}}. Some superheaters are radiant type; that is, they absorb heat by radiation. Others are convection type, absorbing heat from a fluid. Some are a combination of the two types. Through either method, the extreme heat in the flue gas path will also heat the superheater steam piping and the steam within. While the temperature of the steam in the superheater rises, the pressure of the steam does not and the pressure remains the same as that of the boiler.<ref>Bell, A.M. (1952) ''Locomotives'' '''1''' p 46. Virtue and Company Ltd, London</ref> Almost all steam superheater system designs remove droplets entrained in the steam to prevent damage to the turbine blading and associated piping.
===Supercritical steam generator===
[[Image:Turmkessel02.png|right|thumb|250px|Boiler for a power plant.]]
{{Main|Supercritical steam generator}}
Supercritical steam generators are frequently used for the production of [[electric power]]. They operate [[Supercritical fluid|at supercritical]] pressure. In contrast to a "subcritical boiler", a supercritical steam generator operates at such a high pressure (over {{convert|3200|psi|MPa|abbr=on|disp=or}}) that the physical turbulence that characterizes boiling ceases to occur; the fluid is neither liquid nor gas but a super-critical fluid. There is no generation of steam bubbles within the water, because the pressure is above the [[Critical temperature and pressure|critical pressure]] point at which steam bubbles can form. As the fluid expands through the turbine stages, its thermodynamic state drops below the critical point as it does work turning the turbine which turns the electrical generator from which power is ultimately extracted. The fluid at that point may be a mix of steam and liquid droplets as it passes into the [[Condenser (heat transfer)|condenser]]. This results in slightly less fuel use and therefore less [[greenhouse gas]] production. The term "boiler" should not be used for a supercritical pressure steam generator, as no "boiling" occurs in this device.
== المغلاة ==
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