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HEATINC VENTILATING AIR CONDITIONING GUIDE 1942 Vapor Heating System: A steam heating system which operates under pressures at or near atmospheric and which returns the condensation to the boiler or receiver by gravity. Vapor systems have thermostatic 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: Synonymous with saturation pressure in the case of a pure substance. 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 = -j-. Velocity Pressure: The difference due to velocity between total pressure and static pressure. It is supposed to equal the kinetic energy per unit volume of the fluid at the point of measurement. 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 central fan furnace system. A fan furnace system may include air washers and filters. Wet-Bulb Temperature: Thermodynamic wet-bulb temperature is the temperature at which liquid or solid water, by evaporating into air, can bring the air to saturation adiabatically at the same temperature. Wet-bulb temperature (without qualification) is the temperature indicated by a wet-bulb psychrometer constructed and used according to specifications. (A.S.M.E. Power Test Codes, Series 1932, Instruments and Apparatus, Part 18.) 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.) ABBREVIATIONS 1 Absolute.______________________ Acceleration, due to gravity.......... Acceleration, linear............ ............ Air horsepower_________________ Alternating-current (as adjective) Ampere................... ........................ Ampere-hour..... ............................ Area.................... ........................ ... Atmosphere....... ............................ Average........................................... Avoirdupois..... .............................. Barometer....................................... Boiler pressure..... -....................... Boiling point....... ...... .... ............... Brake horsepower..... ................ -- Brake horsepower-hour................. British thermal unit...................... Calorie.....................'....................... Centigram.............. ,,......... ............. Centimeter____________________ _________ abs ----------------- g _______air hp ________--a-c _,____ ....amp _____ amp-hr .... :____ a ________ atm -------------- avg _____ __ avdp ................ bar. .... ------- bp ----------------- bp ______..___bhp bhp-hr .................. Btu cal ..................... eg ___________cm From compilations of abbreviations approved by the American Standards Association, Z 10.1-1941 and 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. 844 CHAPTER 47. TERMINOLOGY Centimeter-gram-second (system)-------------------------Change in specific volume during vaporization-------- Cubic----------------------------------------------------------------Cubic foot Cubic feet per minute........ ................... ...................... Cubic feet per second------------------------------------------- Decibel----------------------------- -------------------------------Degree1-------------------------------------------------------------Degree centigrade--------------------------------------------- Degree Fahrenheit------------------------,---------------------Degree Kelvin----- ----- --------------- --- ---------------------Degree Reaumur___________ :.------------------- ---------Density, Weight per unit volume, Specific weight-- ----------- .cgs ----------------Ufg- cu ........... cu ft ______ ,cfm ________ cfs ,_______ db ___ deg or _________C _________ F ........... .... K _________ R d or p (rho) v _D_ia__m_e_t_e_r.. _________ ________ ..D or diam Direct-current (as adjective)__________________________________________________d-c Distance, linear----------- --------------------- -------- ------------------ -------------------------------------s Dry saturated vapor, Dry saturated gas at saturation, pressure and temperature, vapor in contact with liquid________________________ Subscript s Entropy. (The capital should be used for any weight, and the small letter for unit weight)-- S or s Feet per minute... _fpm Feet per second... --fps Foot- ft Foot-pound________________ ..ft-lb Foot-pound-second (system).. ....ips Force, total load___________ ..F Freezing point --fp Gallon_ --gal Gallons perminute.......................... gpm Gallons per second___________ __________________________ --.................................gps Gram................ g Gram-calorie------ --------------------------------------------------------------------------------- g-cal HeadH r h Heat content, Total heat, Enthalpy. (The capital should be used for any weight and the small letter for unit weigghhtt);.. H or h Heat content of saturated liquid, Total heat of saturated liquid. Enthalpy of saturated liquid, sometimes called heat of the liquid .M Heat content of dry saturated vapor, Total heat of dry saturated vapor, Enthalpy of dry saturated vapor.. Heat of vaporization at constant pressure. Horsepower.. Horsepower-hour.. or ftfg hp ..hp-hr Hour........ ............. Inch.. Inch-pound... Indicated horsepower.. Indicated horsepower-hour.- .......hr ...... in. .. in.-lb .ihp _ihp-hr Internal energy. Intrinsic energy. (The capital should be used for any weight and the small letter, for unit weight)-------------------------------------------------------------- U or a Kilogram1------------------------------------------------------------------------------------ -------- --------- -bg Kilowatt.. kw Kilowatthour_ kwhr Length of path of heat flow, thickness.--............ ................................ ...... ;................. L Load, total --....................................................................................W Mass ________________________________________________ ___________ _________ mass Mechanical efficiency.________ Mechanical equivalent of heat~ Melting point________________ Meter_` ...................Cm ..mp _m *It is recommended that the abbreviation for the temperature scale, F, C, K, be included in expressions for numerical temperatures but, wherever feasible, the abbreviations for degree be omitted; as 68 F. 845 i