Document dnnGB0j9JQpOBDzy3p4RRg4O6

HEATING VENTILATING AIR CONDITIONING GUIDE 1941 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 mainsthey 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 -- -y. 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. (/t.S.Af.ii. 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.) ABBREVIATIONS1 Absolute._____ -- Acceleration, due to gravity..-___ .... Acceleration, linear-----------------------Air horsepower:.-. Alternating-current (as adjective)-- Ampere.________ _____________ Ampere-hour...... ............................ ..... Area____________________ _________ Atmosphere______ :....... .................. .. Average___ ___--11....... ............. :...... Avoirdupois___________________ ,__ Barometer................................. Boiler pressure........ ....... ... ...... ......... Boiling point.___________________ :... Brake horsepower............................... Brake horsepower-hour........ ............. British thermal unit_______________ Calorie--------------------,.............. ........ Centigram............................... Centimeter:L -- ;.. .....,------------------------abs . ................ ____ ___ S a ----------J..air hp ....... .......... a-c ........................ :____amp ----------- amp-hr A ..................................atm -------------- -------- ---avg _________________ avdp .............. bar. ------------------------------bp - ........................-- -bp ........ :..................._.bhp _____________ .....bhp-hr ........ :_____ ;.......... _Btu .............................. cal ........ -........-.............. -eg ................... ......... :__ cm U^rom compilations of abbreviations approved by the American Standards Association, Z, 10 a, c. f. and As a general rule the period is omitted in all abbreviations except where the omission results in the formation of an English word. ." CHAPTER 46. TERMINOLOGY rentimeter-gram-second (system)-------- ,--r------ .--cgs Change in specific volume during vaporization ... Cubic----- ------------------------------------------------ ---------Cubic foot.. --tifg ___cu ..cu ft Cubic feet per minute......................................... -............................................-................. -- cfm Cubic feet per second........................................ .............. ................ ............ .............................. cm DecibelDegree5- .................... ................................................................................................~..deg or` Degree centigrade...................................... --.............. -- -......................................................... C Degree Fahrenheit.--------------------------------------------- ------ ------ ---------------------------------------- Degree Degree KReealvuimn-u--r---------------------------------------------------.-.-.--------_--------------.-.-.-.-.-..........................................--.....................................................-.......................*R- Density, Weight per unit volume, Specific weight-----------;.................... d or p (rho) d =s ~v Diameter.................. Direct-current (as adjective).. ..D or diam .............. d-c Distance, linearDry saturated vapor, Dry saturated gas at saturation pressure and temperature, vapor in contact with liquid------------------ :------------------------------------------ Subscript g Entropy. (The capital should be used for any weight, and the small letter for unit weight)................. .......... .......... ........................................ ..................................... $ or s Feet per minute-.................................................-......... -................................................. 'Pm Feet per second.--......... ....... ........... ........ ................. -..................................... :............. --`P Foot-- ft Foot-pound...................... ............................................................ .............................................. ft-H5 Foot-pound-second (system)........................ --................. ........................ .................... .........1 P Freezing point--------------'.................-................. ......... ........ ...................................... ....... fP Gallon.... .................... ................ ......... ...... ..................................... ...................................sal Gallons per minute--...........................-................................ --....................................... gPra Gallons per second............. ........ .........,......... ........... ....... .......... ;....... .............. -...........--gps Gram.......... --............ ................-.............................-...... :................................. -.............. Gram-calorie............................ ................. ........................ .....................-..................... v,g_ca, Hjad______________________________ ,____________________________ __________H or h Heat content, Total heat, Enthalpy. (The capital should be used for any weight and the small letter for unit weight)--------------------------------------------------------- H or h Heat content of saturated liquid. Total heat of saturated liquid. Enthalpy of saturated liquid, sometimes called heat of the liquid.. ..hi Heat content of dry saturated vapor, Total heat of dry saturated vapor, Enthalpy of dry saturated vapor.------ .------ ------------------------------------------------------------------ Heat of vaporization at constant pressure........ ......................................................-L or hig Horsepower.--- ----------------------------------------........... ......--..................---........... ............ hp Horsepower-hour..... ........................................................................ ......... ..................... hp-hr Hour....................... :............. .................. ,......... ,..... .--.... ....... ...... ..............................---hr Inch............. ........... .............. -..................... t.............. -....... -............... --..................... --..in. Inch-pound.................. ....... ....... ..... .............. .................. -........................................... in.-lb Indicated horsepower--...........................................................-...............-............ -....... --~ihp Indicated horsepower-hour.:____ .................... ihp-hr Internal energy, Intrinsic energy. (The capital should be used for any weight and the small letter for unit weight)--------- ----- ------------------- ----------------------------- U or u Kilogram....................................... ................................ .......................................................kg Kilowatt_____ _________.;......--_--1._--_-------------.......------------kw Kilowatthour _______________ --.............. ........... ----__ ---.....--------------- -----,........... kwhr Length of path of heat flow, thickness----- .". --...... ............. ....... ---.......... 1:........ ----- L Load, total i.................................--............. -- 1.... --......... ....... ----............W Mass :............................ .... ................................................. ................. ...................... mass Mechanical efficiency........................ .... -................................. --..................... -.... ~tn Mechanical equivalent of heat--....................... -...........................-..................... -- Melting point......... ........ ..... ........................ .................................................. .................. mp Meter-..... .......... ......................... ........ ..... .... ................... ..... ~........................... -.............. 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. .. 799