**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.