Document Z43jeQ1QvOrmNONxqwVkN12qd

Heating Ventilating Air Conditioning Guide 1938 and floor when supported from below. Other descriptive words include free delivery when the unit is not intended to be attached to ducts or similar resistance-producing devices, and pressure when for use with such ducts. Complete description requires the use of several of these qualifying words or phrases. See Chapter 23. Up-Feed System (steam): A steam heating system in which the supply mains are below the level of the heating units which they serve. Vacuum Heating System: A two-pipe steam heating system equip ped with the necessary accessory apparatus which will permit operating the system below atmospheric pressure when desired. Vapor: Any substance in the gaseous state. Vapor Heating System: A steam heating system which operates under pressures at or near atmospheric and which returns the condensa tion to the boiler or receiver by gravity. Vapor systems have thermo static traps or other means of resistance on the return ends of the heating units for preventing steam from entering the return mains; they also have a pressure-equalizing and air-eliminating device at the end of the dry return. Direct Vent Vapor System: A vapor heating system with air valves which do not. permit re-entry of air. Vapor Pressure: The equilibrium pressure exerted by a vapor in contact with its liquid. Velocity: The time rate of motion of a body in a fixed direction. In the fps system it is expressed in units of one foot per second. V = --. , 't Velocity Pressure: The pressure corresponding to the velocity of flow. It is a measure of the kinetic energy of the fluid. Ventilation: The process of supplying or removing air by natural or mechanical means, to or from any space. Such air may or may not have been conditioned. (See Air Conditioning.) Warm Air Heating System: A warm air heating plant consists of a heating unit (fuel-burning furnace) enclosed in a casing, from which the heated air is distributed to the various rooms of the building through ducts. If the motive head producing flow depends on the difference in weight between the heated air leaving the^casing and the cooler air entering the bottom of the casing, it is termed a gravity system. A booster fan may, however, be used in conjunction with a gravity-designed system. If a fan is used to produce circulation and the system is designed especially for fan circulation, it is termed a fan furnace system or a centralfanfurnace system. A fan furnace system may include air washers and filters. Wet-Bulb Temperature: The lowest temperature which a. water wetted' body will attain when exposed to an air current. This is the temperature of adiabatic saturation. Wet Return: That part of a return main of a steam heating system which is filled with water of condensation; . The wet return usually is below the,level of the water line in the. boiler, although not necessarily so.' See.Dry Return. .;... . 830, Chapter 45. Terminology . ABBREVIATIONS2 Absolute.......................................... ............ Acceleration, due to eravitv..........i............................ Acceleration, linear , Air horseoower............. .............. Alternating-current fas adiectivel Ampere................. ............... .............................. .......... Ampere-hour.- ................................... ................ Area................................................................................ Atmosphere........................................ ........................ Average............ ....... .......................... . Avoirdupois.............................. ......... Barometer. ........................... ......... Boiler pressure Boiling point. _... Brake horsepower................................. ......... Brake horseDOwcr-hnnr British thermal unit Calorie. .......... ............................... Centigram......................................... ..... Centimeter................................................ .. Centimeter-gram-second fsystem) Change in specific volume during vanorixation Cubic .... .............. Cubic foot................................. ............................. Cubic feet per minute........... ...................... Cubic feet per second Decibel...................................... Degree5.................. ............................. Degree centigrade.................. ................... DegreeFahrenhe.it Degree Kelvin............................. ......... Degree Reaumur Density. Weight per unit volume. Specific weight .................... A r_ r V K p ' ' d-. Diameter. Direct-current (as adjective! ____ Distance, linear.-............................................... V ............................................ j Vapor in contact with liquid.. ..Subscript g Entropy (The capital should he used (or any weight, and the small letter for unit weight.)...... ..............................:................... ................................ .'............... ...................... 5 or r Feet per minute.......................i........................................................................... ............ ..............fpm Feet per second......................................................................................... ....... ..,....... .....................fps Foot.........................................................J........... ............ ................. ......... ,!............................... ....ft Foot-pound...... ............................................................................................... ............ ...................ft-lb Foot-pound-second (system) ...fps Force, total load............ ......... ..F Freezing point.......................... Gallon.-............................... ......... .....fp --gal Gallons per minute.-.............. ..gpra Gallons per second.................. ~.gps Gram:_____ _--:.......................... Gram-calorie............................. -g -g-cal *From compilations of abbreviations approved by the American Standards Association. Z, 10 a, c, f, and i. As a general rule the period is omitted in all abbreviations except where the omission results in the formation of an English word. *It is recommended that the abbreviation for the temperature scale. F, C, K, be included id expressions for numerical temperatures but, wherever feasible, the abbreviation*for degree be omitted; as 68 F. .831