Boiler & Steam Definitions

Boiler Horsepower (BHP): BHP is a term used to indicate the heat output of an industrial steam boiler (industrial steam generator). Technically, BHP is 33,475 BTU/hr (or 8,430 kcal/hr) which is derived from the amount of energy needed to produce 34.5 pounds of steam/hour at a pressure of 0 psig and temperature of 212°F, with feedwater at 0 psig and 212°F

Calorie (C): The amount of heat required to raise the temperature of one gram of water one degree Celsius at a pressure of one atmosphere.

Enthalpy (H or h): Thermodynamically, enthalpy is the sum of the internal energy of a body and the product of its volume, multiplied by its pressure. For the sake of boiler calculations, enthalpy is defined as the amount of heat in a fluid, usually expressed as BTU/lb or kcal/gram. In these cases, enthalpy is considered to be 0 at 32°F (0°C).

From and at 212°F: A term used to qualify the amount of steam produced by a steam boiler (steam generator). (See the section on Steaming Rate.) The qualification indicates that the amount of steam produced is at a pressure of 0 psig and 212°F, with feedwater at 0 psig and 212°F.

Gross Steaming Rate: The amount of steam produced by a boiler at the outlet flange of the boiler. This includes the amount of steam produced to heat the water in the feedwater receiver (deaerator or hotwell).

Heat of Vaporization: For steam boiler calculation purposes, this is the amount of heat required to convert water, at saturated conditions, to vapor (steam) at the same saturated conditions. Same as Latent Heat.

Latent Heat: See "Heat of Vaporization," (above).

Net Steaming Rate: The amount of steam produced, by a boiler, after blowdown and after steam is used for heating the water in the feedwater receiver (deaerator or hotwell).

Saturated Liquid: Liquid that is at a saturated pressure and temperature.

Saturated Steam: Steam (vapor) that is at a saturated pressure and temperature.

Saturated Vapor: Vapor that is at a saturated pressure and temperature.

Saturated Water: See "Saturated Liquid," (above).

Saturation Pressure: The pressure at which saturation takes place at a given temperature.

Saturation Temperature Sensible Heat: The heat (enthalpy), usually expressed as BTU/lb or Cal/g, in a liquid.

Specific Heat: The amount of heat (enthalpy) required to raise the temperature of one unit of mass, one degree. Usually expressed as BTU/lb/F or Cal/kg/C.

Steaming Rate: The rate, usually expressed in lbs/hr or kg/hr, at which a boiler produces steam. (See the section on Steaming Rate.)

Sub-cooled Liquid: A liquid that is at a temperature or pressure below the saturation temperature and pressure.

Superheat: The extra heat imparted to a vapor (steam) in heating it from a dry saturated condition. Also the corresponding rise in temperature.

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Boiler and Steam Definitions