Document g2DpJ68OYy2Qz0OpmGGYeG82J

10 CHAPTER 1 1956 Guide Two-Pipe System'(Stakin'or Water): A heating system in which one pipe is used for the supply of the heating medium to the heating unit, and another for the return of the heating medium to the source of heat supply. The essential feature of a twopipe system is that each heating unit receives a direct supply of the heating medium, which medium cannot have served a preceding heating unit. Up-Feed System:. A 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 necessary accessory apparatus which will permit operating the system below atmos pheric pressure when desired. Vane Ratio: In air distributing devices the ratio of depth of vane to shortest open ing width between two adjacent grille bars. . Vapor: The gaseous form of substances which are-normally in the solid or liquid' state, and which can be changed to these states either by inpreasing-the pressure or; decreasing the temperature. - Vapors diffuse.' (A5A definition.) Vapor Heating System : A steam heating system which operates under pressures' at or near atmospheric and which returns the condensate to* the boiler or receiver bygravity. 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-equalising and air-eliminating device atihe end of the dry-; return. ' .` Velocity: A vector quantity which denotes at once the time rate and the direction- of a linear motion. V = -a37t* For uniform linear motion V = ~t Common units are: feet per second. * Ventilation: The process of supplying or removing air^by natural or mechanical; means, to or from any space. Sucnair may or .may not have been conditioned. (See} AirConditioning.) Viscosity: That property of semi-fluids, fluids and gases by virtue of which they: resist an instantaneous change'of shape "or arrangement of parts. It is the cause of fluid friction whenever adjacent layers of fluid move with relation to each other..,- The coefficient of viscosity is the resistance offered by a layer of the fluid of unit area to the motion parallel to this area of another layer of the fluid at unit distance: moving with unit velocity relative to the firsts layer. This coefficient is known as: the absolute viscosity, and in cgs units is the.force in dynes per square centimeter at, a velocity of 1 cm per second at a distance of 1 cm.; Tms unit of absolute viscosity-is the poise. Values of absolute viscosity are frequently listed in centipoises, a centiri poise being 1/100 of 1 poise. In many formulas absolute viscosity is expressed in pounds per .foot second or pounds per foot hour. Conversion from centipoises may be made as follows: visr cosity in centipoises X 0.000672 = viscosity in pounds per foot second, or viscosity in centipoises X 2.42 viscosity in pounds per foot hour. Kinematic viscosity is the ratio of absdlute viscosity to the density of a fluid. The unit is the stoke which equals one poise per cu cm per gram , or 1 sq cm per sec. For conversion to English units: kinematic viscosity in stokes X 0.001076 = kinematic viscosity in square feet per second. ' Volume, Specific: The volume of a substance per unit mass; the reciprocal of; density. Units: cubic feet per pound, cubic centimeters per gram, etc. Warm Air Heating System: A warm air heating plant consists of a heating unit' (fuel-burning fuimace) enclosed in a casing, from which the heated air is distributed, to various rooms of the building .through ducts. Warm Air Heating System, Forced: A warm airheatine system in which circular, tion of air is effected by a fan. Such a system may include air cleaning devices. Warm Air Heating System, Gravity: A warm air heating system in which the mo tive 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. Warm Air Heating System, Perimeter: A warm air heating system of the combi- nation panel and convection.type.' Warm air ducts embedded in the concrete slab of a basementless house, around the perimeter, receive heated air from a furnace and-, deliver it to the heated space through-registers placed in or: near the floor. Air is returned to the furnace from registers near the ceiling.'. CHAPTER 2 ABBREVIATIONS, SYMBOLS, CONVERSION FACTORS Standard Abbreviations; Standard Symbols; Greek Alphabet; Conversion Equations; Graphical Symbols for Piping, Ductwork, Heating and Ventilating, Refrigerating; Identification of Piping by Color THIS chapter contains information regarding abbreviations, symbols, and conversion equations, which are of particular interest to the engi neer engaged in heating, ventilating, and air conditioning. ABBREVIATIONS Abbreviations are shortened forms of names and expressions employed in texts and tabulations, and should not generally be used as symbols in equations. Most of the following abbreviations have been compiled from a list of approved standards.1 In general, the period has been omitted in all abbreviations, except .where the omission,results in the formation of an English word. Additional abbreviations applying to individual chapters will be found at the end of Chapters 3, 4, 13, 32, and 47. Absolute.............................. abs Air horsepower.............................................................................................................. air hp Alternating-current (as adjective)............................................ a-b Ampere.................................. amp Ampere-hour..................................................................... amp-hr Atmosphere.. Average....... Avoirdupois.. Barometer-- Boiling point. . atm . - avg avdp .bar. ...bp Brake horsepower................................................................ ......... ....... ;...:......... . .bhp Brake horsepower-hour.................. bhp-hr British thermal unit................................................ JBtu British thermal units per hour............................................................. Btuh Calorie....................................................... cal Centigram............................................................................................. ...........................eg Centimeter...................................................................................................................... cm Centimeter-gram-second (system)............................ ........................................... . cgs Cubic........ :.......................................................................... .............................. .............. .cii Cubic centimeter............... .......................................................... .. .cu cm or cc Cubic foot.......................... .......................................................................................... cu ft Cubic feet per minute............................................................. ............... ................... cfm Cubic feet per second........ ............................................................................................ cfs Decibel.......... ......................................................................................... '............................db Degree*................... .......................................................... ....................................... deg or Degree, Centigrade......... ...................................................:..............................................C Degree, Fahrenheit............... ....................................................... .........;........................ F Degree, Kelvin.................. .............. .............. ..................... .............................................K Degree, Rankine...................................... ..........................................................................R Diameter.................................................................................................. ...................... diam 1 Abbreviations for Scientific and Engineering Terms, Z10.1-1041 (American Standard* Ateociation). * It is recommended that the abbreviation for the temperature scale, F. C. K, R, be included in expres* fiioss for numerical temperatures but, wherever feasible, the abbreviation for degree be omitted *4^ 68 r. 11 --