Generation of steam

Steam is generated in a boiler by the application of heat to some part, which is in close contact with the water it contains. The heat raises the temperature of the water to boiling point and eventually produces steam.

Sensible heat is the one added to the water during the period in which the temperature is rising and while no steam is being generated.

When boiling point is reached, the heat necessary to convert the water into steam is latent one and cannot be measured by the thermometer. Steam heated to a temperature above that which is necessary to make water boil at the given pressure is termed superheated steam.

The total heat of superheated steam is the one required superheating to the desired temperature, plus to total heat of dry saturated steam above 32° F, and at the superheated pressure. When steam is generated in a closed vessel, the water and steam cannot be under the influence of the atmosphere, and therefore the pressure shown by the boiler is the pressure, which differs from the absolute pressure by an amount equal to atmospheric pressure. For practical purposes atmospheric pressure is taken as 15 lbs. per sq. in., and therefore the readings for the absolute pressure of steam in a boiler are 15 lbs. greater than those shown by the pressure gauge.

Лексико-семантические и фразеологические вопросы письменного перевода

Дата добавления: 2015-07-25