Document pexeENGEgb0Jmwb7yVM5xrrYD

HEATiNC VENTILATING AIR CONDITIONING CUIDE 1944 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 equipped with the neces sary 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 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 as. 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 fanfurnace system. A fan furnace system may include air washers and filters., ' Wel-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 adiabaticaily 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.) 820 CHAPTER 48 ^dblreuiationS, .Symboh, ^Standards Standard Abbreviations, Conversion Equations, Graphical Symbols foe Piping, Ductwork, Heating and Ventilating, Refrigerating, Specific Heat Table, State Codes or Standards THE abbreviations outlined herewith pertaining to heating, venti lating, and air conditioning have been compiled from a selected list of approved standards1. In general the period has been omitted in all these abbreviations except where the omission results in the formation of an English word. Grouped together in this chapter will be found a few conveniently arranged conversion equations. The graphical symbols for drawings have been abstracted from a recently approved standard2. The specific heats of a selected .list of solids, liquids, gases and vapors are given in Tables 1, 2 and 3. An outline of available state codes, standards or laws relating to the heating, ventilating, or air conditioning of various types of buildings is given in Table 4. This material was compiled by the A.S.H.V.E. and is based on information furnished by the individual states through a com prehensive survey conducted in 1943. References are given to the titles of all codes, standards or laws which relate to this field of engineering and where copies of these standards may be obtained. 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--_____________ ___labs -----------g a ...air hp ____ a-c ___amp .amp-hr __ atm -----avg __avdp __ bar. --bp .bhp .bhp-hr ___ Btu ------ cal --------- eg ____cm Abbreviations for Scientific and Engineering Terms, Z10.1-1941; Letter Symbols for Mechanics of Solid Bodies, Z10.&1942, and Letter Symbols for Heat and Thermodynamics, Z10.4-1943 (American Standards Association). 'Graphical Symbols for Use on Drawings in Mechanical Engineering, Z32.2-1941 (American Standards Association). 821