Document 8VR7dKxZe0dgZaGOkom9D625k

4 CHAPTER 1 1956 Guide Dry: To separate or remove a liquid or vapor from another substance. The liquid may be water, but the term is also used for the removal of liquid or vapor forms of other substances. Dust: An air suspension (aerosol) of solid particles of any material. (See also Chapter 8.) : , Enthalpy: A term used in lieu of total heal or heat content. Expressible in Btu per pound. Mathematically defined as h = u + pv/J. When a change occurs at con stant pressure, as when water is boiled, the change in enthalpy is equal to the heat added; in this case latent heat. Enthalpy, Free: A thermodynamic property which serves as a measure of the available energy of a system with respect to surroundings at the same temperature and same pressure as that of the system. No process involving an increase in avail able energy can occur spontaneously. Enthalpy, Specific: A term sometimes applied to enthalpy per unit weight, the English unit being Btu per pound. , Entropy: The ratio of the heat added to a substance to the absolute temperature at which it is added. Mathematically, for a reversible process, dS = dQ/T or S *= fdQ/T. . These formulas are applicable when temperature is not constant. During a re versible adiabatic change, entropy: is constant. During a reversible isothermal . change, the heat absorbed by the substance is equal to the' product of the absolute temperature of the substance and its change of entropy. Entropy, Specific: A term sometimes applied to entropy per unit weight, the English unit being Btu per (Fahrenheit degree, absolute) (pound). Equivalent Evaporation: The amount of water a boiler would evaporate, in pounds per hour, if it received feed water at 212 F and vaporized it at the same temperature and corresponding atmospheric pressure. Fan Furnace System: See Warm Air Heating System. Fog: Suspended liquid droplets generated by condensation from the gaseous to the liquid state, or by breaking up a liquid into a dispersed state, such as by splashing foaming, and atomizing. (See also Chapter 8.) Force: The action on a body which tends to change its relative condition as to rest or motion. Fumes: Smoke; aromatic smoke; odor emitted, as of flowers; a smoky or vaporous exhalation, usually odorous, as that from concentrated nitric acid. The wordfumes is so broad and inclusive that its usefulness as a technical term is very limited. Its principal definitive characteristic is that it implies an odor: The terms vapor, smoke, fog, etc., which can be more strictly defined, should be used whenever possible., r. Also defined as solid particles generated .by condensation from the gaseous state,' generally, after volatilization from molten metals, etc., and often accompanied by a chemical reaction such as oxidation. Fumes flocculate and sometimes coalesce. (See also Chapter 8.) , Furnace: That part of a boiler or warin air heating plant in which combustion ta^es place. Also a complete heating unit for transferring heat, from fuel being bnrnea to the air supplied to a heating system. ; . Furnace Volume (Total): The total furnace volume for horizontal-return tubular/ boilers and water-tub boilers is the cubical contents of the furnace between the grate and "the first plane of entry into or between tubes. It therefore includes the volume behind the bridge wall as in ordinary horizontal-return tubular boiler settings, unless manifestly ineffective (t.e., ho gas flow taking place through.it), as in the case of waste-heat boilers with auxiliary coal furnaces, where one part of the furnace is out of action when the other is being used. For Scotch or other internally-fired boilers, it is the cubical contents of the furnace/flues and combustion chamber, up to the plane of first entry into the tubes. (ASME Power Test Codes, Series 1929.) Grate Area: The area of the grate surface, measured in square feet, to be used in estimating.the rate of burning-fuel.;. This area is;construed'.tb mean the area meas ured in the plane of the top surface of the grate, except that with special furnaces,, such as those having magazine feed, or special shapes, the grate area shall be the mean area.of the active part; of the fuel bed taken perpendicular to the path of the gases through it. For furnaces having a*secondary grate, such as those in double grate down-draft boilers, the effective area shall be taken as the area of the upper grate plus one-eighth of the area of the lower grate, both areas'being estimated as previously defined. Gravity, Specific: The ratio of the mass of a unit volume of a substance to. the. mass of the same volume of a standard substance at a standard temperature. 'Water Terminology 5 at 39.2 F is the standard substance usually refetyqd 'tar: dmaitrat `the same temperature and pressure as the gas, is often taken as;tbe. Standard [substance: Gravity Warm Air Heating System: SeeWarm Air 'Heating SysterkC-'r sf.t Head, Dynamic: Same as Total Pressure expressed in height of liquid. Heat: That form of energy which transfers from phe'.`system to. another, by virtue of the temperature difference which exists between the two systems, wheu'they are placed in communication. ~ 'v Heat, Humid: Ratio of increase of enthalpy, per pound of dry air-tc rise -of; tem perature under conditions of constant pressure and constant humidity ratio. 7 V\- i Heat, Latent: A term used to express the energy involved in a change of state! ? Heat, Sensible: A term used in heating and cooling to indicate any portion ofbeat which changes only the temperature of the substances involved;. 7 '>7 Heat of the Liquid: The increase in enthalpy per unit weight of a saturated liquid as its temperature increases from a chosen base temperature. ;For water, .the base temperature.is usually taken as 32 F. vrsnpi Heat, Specific: The heat absorbed (or given up) by a unit ihass of af Substance when its temperature is increased (or decreased) by 1- deg. Common .Units: Btu per (pound) (Fahrenheit degree), calories per.Xgram)-(Centigrade degree)., For gases, both specific heat at constant pressure (cp) and specific heat at constant voJ-qme(cT) are frequently used. In air conditioning, cp is usually used. ; r, ? Heat, Total 2 See Enthalpy. Heat Transmission, Coefficient: Any one of a number of coefficients used in the calculation of heat transmission by conduction, convection, and radiation, through various materials and structures. (See thermal conductance, thermal conductivity, thermal resistance, thermal resistivity, thermal transmittance, etc.) Heating Element, Electric: A unit assembly consisting of a resistor, insulated sup ports, and terminals for connecting the resistor to electric power. Heating Unit, Electric: A structure containing one or more heating elements, electrical terminals or leads, electric insulation, ana a frame or casing, all assembled together in one unit. Hot Water Heating System: A heating system in which water is used as the me^ dium by whichheat is carried from the boiler to the heating units. Humidify: To increase ,by any process, the density of water vapor within a given space. : : Huinldistat: A regulatory device, actuated by changes.in humidity, used for the automatic control ofrelative humidity. . 1 . Humidity: Water vapor within a given space. . ----- Humidity, Absolute: The weight of water vapor per unit volume, pounds per cubic foot or grams per cubic centimeter. * v* ' Humidity, Relative: The ratio of the mol fraction of water vapor.in a mixture to the mol fraction of water vapor in saturated air at the same dry-bulb temperature and barometric pressure. (See discussion in Chapter 3.) Also defined in various texts as the ratio of the actual partial pressure of the water vapor in a space to the saturation pressure of pure water at the same temperature. Humidity Ratio: in a mixture of water vapor and air, the weight of water vapor per pound of dry air. Symbol, W. Also called Specific Humidity. Humidity, Specific: SeeHumidity Ratio. Hygrostat : Same as Humidistai. Inch of Water: A unit of pressure equal to the pressure exerted by a column of liquid water 1 in. high at a.standard temperature. The standard temperature is sometimes taken as 0 C and sometimes as 62 F. One inch of waterat 62 F = 5.1971b per sq.ft. ..... - - -d Insolation (Thermal): A material having a relatively high resistance to heat flow; and used principally tp retard the flow of heat. Isobaric: An adjective used to indicate a change takipg place at constant pressure: Isothermal: An adjective used to indicate a change taking place at constant temperature. . - s ;*"4- . Load, Estimated Design : In a heating or cooling system, the sum of the useful heat transfer, plus heat transfer from or to the connected piping, plus heat transfer occurring in any auxiliary apparatus connected to.the system. The units are Btu per hour or, in heating, equivalent direct radiation (EDJR).. .. Load, Estimated Maximum : In a heating or cooling system, the Calculated maxi* mum heat transfer that the system will be called upon to provide.