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There are two types of air preheaters for use in steam generators in thermal power stations: One is a tubular type built into the boiler flue gas ducting, and the other is a regenerative air preheater. [1] [2] [7] These may be arranged so the gas flows horizontally or vertically across the axis of rotation.
The thermal power level is easily varied by simply increasing or decreasing the forced recirculation flow through the recirculation pumps. The two-phase fluid (water and steam) above the core enters the riser area, which is the upper region contained inside of the shroud.
The only railway use of water-tube boilers in any numbers was the Brotan boiler, invented by Johann Brotan in Austria in 1902, and found in rare examples throughout Europe, although Hungary was a keen user and had around 1,000 of them. Like the Baldwin, it combined a water-tube firebox with a fire-tube barrel.
The majority of the world's thermal power stations are driven by steam turbines, gas turbines, or a combination of the two. The efficiency of a thermal power station is determined by how effectively it converts heat energy into electrical energy, specifically the ratio of saleable electricity to the heating value of the fuel used.
In order for these boilers to operate properly, they require a long warm-up process, and are prone to thermal shock of the boiler. These boilers can be rated up to 500,000 lb/hr. [2] The wall membrane of the boiler are dual welded, (welded on either side of the wall membrane) to provide extra reinforcement for high loads.
A heating system is a mechanism for maintaining temperatures at an acceptable level; by using thermal energy within a home, office, or other dwelling. Typically, these systems are a crucial part of an HVAC (Heating, Ventilation, and Air Conditioning) system.
Condensing boiler manufacturers claim that up to 98% thermal efficiency can be achieved, [3] compared to 70%-80% with conventional designs (based on the higher heating value of fuels). Typical models offer efficiencies around 90%, which brings most brands of condensing gas boiler in to the highest available categories for energy efficiency.
In general, valves nearest to the boiler should vent the slowest, and valves furthest from the boiler should vent the fastest. [ citation needed ] Ideally, steam should reach each valve and close each and every valve at the same time, so that the system can work at maximal efficiency; this condition is known as a "balanced" system.