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The water level of these boilers was around 3/4 of the height of the tube tiers, [3] so that the upper tubes were filled with steam rather than water. Above the tube banks a single flat spiral tube was used as an economiser or feedwater heater. [2] The furnace used to fire these large boilers was annular, often with four or more separate firedoors.
A slightly more successful adoption was the use of hybrid water-tube / fire-tube systems. As the hottest part of a locomotive boiler is the firebox , it was an effective design to use a water-tube design here and a conventional fire-tube boiler as an economiser (i.e. pre-heater) in the usual position.
Direct electric resistance tank water heaters are not included in the Energy Star program; however, the Energy Star program does include electric heat pump units with energy factors of 200% or higher. Tankless gas water heaters (as of 2015) must have an energy factor of 90% or higher for Energy Star qualification.
The Nissan Xterra is a truck-based compact SUV manufactured and marketed by Nissan from 1999 to 2015 across two generations; the first (1999–2004) sharing a platform and many of its major exterior parts from the front doors forward with the Nissan (D22) Frontier pickup [1] – and the second (2005–2015) sharing the Nissan F-Alpha platform with the Frontier and Pathfinder.
The move to water-tube boilers had already begun, with designs such as the Babcock & Wilcox or the Belleville. The three-drum arrangement was lighter and more compact for the same power. [1] The new generation of "small-tube" water-tube boilers used water-tubes of around 2 inches (5 cm) diameter, compared to older designs of 3 or 4 inches.
A hot water storage tank where one of the heat sources is solar heating A, that is sent into the hot water storage tank via a smaller pump B (circle with triangle) and the heat exchanger spiral in the hot water storage tank. The other spiral C can be used for a e.g. oil-fired boiler or a wood burner.
In nuclear power plants called pressurized water reactors, large heat exchangers called steam generators are two-phase, shell-and-tube heat exchangers which typically have U-tubes. They are used to boil water recycled from a surface condenser into steam to drive a turbine to produce power. Most shell-and-tube heat exchangers are either 1, 2, or ...
The cooling water used to condense the steam in the condenser returns to its source without having been changed other than having been warmed. If the water returns to a local water body (rather than a circulating cooling tower), it is often tempered with cool 'raw' water to prevent thermal shock when discharged into that body of water.