Document mmDE079vqQdK6axr6yxZEbka0

6 CHAPTER 1 1959 Guide Thermodynamics, Laws of: Two laws upon which rest the classical theory of thermodynamics. These laws have been stated in many different, but equivalent ways. The First Law: (1) When work is expended in generating heat, the quantity of beat produced is proportional to the work expended; and conversely, when heat is employed in the performance of work, the quantity of heat which disappears is proportional to the work done. (Joule)* (G.P.)b; (2) If a system is caused to change from an initial state to a state by adiabatic means only, the work done is the same for ail adiabatic paths connecting the two states. (Zemansky); (3) In any power cycle or refrig eration cycle the net heat absorbed by the working substance is exactly equal to the net work done. The Second Law: (1) It is impossible for a self-acting machine, unaided by any ex ternal agency, to convey heat from a body of lower to one of higher temperature. (Clausius) (G.P.); (2) It is impossible to derive mechanical work from heat taken from a body unless there is available a body of lower temperature into which the residue not so used may be discharged. (Kelvin) (G.P.); (3) It is impossible to construct an engine that, operating in a cycle, will produce no effect other than the extraction of heat from a reservoir and the performance of an equivalent amount of work (Zemansky). Thermostat: An instrument which responds to changes in temperature, and which directly or indirectly controls tem perature. Transmittance, Thermal: The time rate of heat flow, from the fluid on the warm side to the fluid on the cold side, per (square foot) (degree temperature difference between the two fluids). Sometimes called Overall Coefficient of Heat Transfer. Common unit is Btu per (hour) (square foot) (Fahrenheit degree). Symbol U. Two-Pipe System (Steam or Water): A heating system in which one pipe is used for the supply of the besting medium to the heating unit, and another tor the return of the heating medium to the source of heat supply. The essential feature of a two-pipe 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 atmospheric pressure when desired. Vane Ratio: In air distributing devices the ratio of depth of vane to shortest opening 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 increasing the pressure or decreasing the temperature. Vapors diffuse. (ASA definition.) Vapor Heating System: A steam heating system which oper ates under pressures at or near atmospheric and which returns the condensate to the boiler or receiver by gravity. Vapor * Name* of tutbor* who lint ttated laws an gives is parenthese*. " Prom GLotaarj if Pkjtict, by LeRoy Dougherty Weld (McGraw-Hill, 1337). 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 nave a pressure equalizing and air-eliminating device at the end of the dryreturn. Velocity: A vector quantity which denotes at once the time rate and the direction of a linear motion. V TM ^*. For uniform at linear motion V -- Common units are: feet per second. 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.) 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 first layer. This coefficient is knowD 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. This unit of absolute viscosity is the poise. Values of absolute viscosity are frequently listed in centipoises, a centipoise being 1/100 of'l 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: viscosity in centipoises X 0.000672 m 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 absolute viscosity to the density of a fluid. The unit is the stoke which equals one poise gsr cu cm per gram, or 1 sq cm per sec. For conversion to nglish 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 con sists of a heating unit (fuel-burning furnace) 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 air heating system in which circulation of air is effected by a fan. Such a system may include air cleaning devices. Warm Air Heating System, Gravity: A warm air beating system in which 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. Warm Air Heating System, Perimeter: A warm air heating system of the combination panel and convection type. Warm air ducts embedded in the concrete slab of a basementless bouse, around the perimeter, received heated air from a fur nace 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. A a Alpha B 0 Beta T 7 Gamma A S Delta E t Epsilon z S Zeta THE GREEK ALPHABET H, 0t90 It K* AX Mp Eta Theta lota Kappa Lambda Mu Nv Sf 0o nv pp S 9S Nu Xi Omicron Pi Rho Sigma Tr Tu 4> <p 4> Xx *f Q a) Tau Upsilon Phi Chi Psi Omega CHAPTER 2 ABBREVIATIONS, SYMBOLS, CONVERSION FACTORS Standard Abbreviations; Standard Syaibo/s; Conversion Equations;- Graphical Symbols for Piping, Ductwork, Healing and Ventilating, Refrigerating,- Identification of Piping by Color HIS chapter contains information regarding abbrevia Foot-pound-second (system)............... ..............................fP Ttions, symbols, and conversion equations, which are of Freezing point.................................................... ................................ Gallon.................................. -............................... particular interest to the engineer engaged in heating, ventiGallons per minute.......................................... ............................gpm lating, and air conditioning. Gallons per second........................................... ABBREVIATIONS Abbreviations are shortened forms of names and expressions employed in texts and tabulations, and should not generally Gram-calorie....................................................... Horsepower........................................................ Horsepower-hour.............................................. be used as symbols in equations. Most of the following ab nnnr breviations have been compiled from a list of approved stand Inch...................................................................... ards.1 In general, the period has been omitted in all abbrevia tions, except where the omission results in the formation of an English word. inch-pound......................................................... Indicated horsepower...................................... Indicated horsepower-hour............................ Absolute........................................................................................... abs Air horsepower............................................................................air hp Alternating-current (as adjective).............................................. a-c Ampere............................................................................ -............... amp Ampere-hour...............................................................................amp-hr Kilogram.............................................................. Kilowatt.............................................................. Kilowatt-hour. !................ .................................................... kwbr Mass.................................................................................................. mass Melting point..................................................... ............................... mP Atmosphere.......................................................................... atm Average.............. avg Avoirdupois. ...................................................................................avdp Barometer..........................................................................................bar. Boiling point........................................................................................bp Brake horsepower............................................................................ bhp Brake horsepower-hour............................................................ bhp-hr British thermal unit......................................................................Btu British thermal units per hour.................................................Btuh Calorie................................................................................................. .cal Meter........................................................................................................m Micron........................................................................................... ft (mu) Miles per hour..................................................................................mpb Millimeter........................................................................................... mm Minute..................... min Molecular weight........... Mol...................................... Ounce................................ Pound................................ Founds per square inch .mol wt ___ mol ........ o* ..........lb ........psi Centigram.....................................................................................eg Centimeter.......................................................................... -.. cm Centimeter-gram-second (system)............. ..........................cgs Cubic........................................._1_,................................................ cu Cubic centimeter........................................................cu cm or cc Pounds per square inch, gage..................................................... peig Pounds per square inch, absolute.............................................. psia Revolutions per minute.................................................................rpra Revolutions per second................................................................... rpg Second................................................................................................... ec Cubic foot.......................................................................................cu ft Cubic feet per minute....................................................................cfm Cubic feet per second...................................................................... cfs Decibel.................................................................................................. db Degree*.......................................................................................deg or * Specific gravity........ ...................................................................sp er Specific heat.......................................................................................... spht Square foot............................................................................................sqft Square inch....................................................................................sq in. Watt....:................................................................................................w Watthour.......................... ................................................................ wbr Degree, Centigrade..............................................................................C Degree, Fahrenheit.............................................................................. F Degree, Kelvia...................................................................... 7........... K Degree, Rankine..................................... R Diameter..............................................................................................dia Direct-current (as adjective)........................................................ d-c Electromotive Force....................................................................... emf Feet per minute............................................................................... fpm Feet per second................... fps Foot.......................................................................................................... ft Foot-pound....................................................................................... ft-lb < Abbreviation* for Scientific and Eogioeeriiut Term*. Z10.MM1 (American Standard* Anpriitwii), It i* recommended that the abbreviation for the temperature scale, F, C, K, R, be included is expressions for numerical temperatures but, wherever feeeiole, the abbreviation for deft-ss be omitted *-r-. (8 r. SYMBOLS A letter symbol is a single character, with subscript or superscript if required, used to designate a physical magnitude in mathematical equations and expressions. Two or more sym bols together always represent a product. The following have been compiled from a selected list of approved standards.* Additional symbols and variations in the standard symbols found necessary in the individual chapters will be found in a list at the end of Chapters 3, 4, 13, and 53. y^- Acceleration, due to gravity............................................................ 9 Acceleration, linear.............................................................................. * Letter Symbol* fur m--Z10A-134S, tod Letter Symbol* for Hei end Thermodynamic*. Y10.4-1997 (American Standard* Aaaoetaboni. 7