Document zYV6p09xvjGRKwrD6949p89n

American Society of Heating and Ventilating Engineers Guide, 1930 Specific Gravity, referred to Air for Gases, and Water for Solids or Liquids. ......... .................. C Specific Volume; Volume per Unit Weight ........................... v Density; WeightperUnit Volume; Mass per Unit Volume___d or p (rho)' p = 1/p Specific Heat..... .... .....................- c Specific Heat at Constant Pres* sure______________ __ _________- Cp Specific Heat at Constant Vol ume.............................................. On Ratio of Specific Heats................ k k = cp/cT Absolute Viscosity; Coefficient of Viscosity, usually in poises or similar units of stress/shear rate_____ .__ -............................. t* (mu) Relative Viscosity; Ratio of Ab solute Viscosity of any fluid to Absolute Viscosity of Water, (If the second option is used, the context must make clear that Relative Viscosity is meant).......................... n/Vw or u (mu) Kinematic Viscosity (Absolute Viscosity divided by Density)., v (nu) Relative Kinematic Viscosity. (Relative Viscosity divided by Density). (If the second op tion is used the context must make clear that Relative Kine matic Viscosity is meant) v/vjr or Time in seconds obtained from a viscosity measurement with a specific instrument, from which v (nu) y. or v may be computed by ap propriate formulas.................... t Symbols for Thermodynamics Mechanical Equivalent of Heat. Heat Equivalent of Work..l/J or Thermometric Temperature, F or C (0 is preferably used only when t is used for Time in the same discussion)_________ X or Absolute Temperature, F abs J A 0 (theta) Entropy. (Preferably, the capi tals are used for any weight, and small letters, for unit weight)............... ............... .5 or Internal Energy; Intrinsic En ergy. Preferably, the capital is used for any weight and the small letterfor unit weight; U or Heat Content; Total Heat; En thalpy. Preferably the capital is used for any weight and the smallletterfor unitweight; Hor B or h = u -f (A) pv T Helmholtz Free Energy; Interna) Potential Function................... $ (psi) *= u -- Ts Gibbs Function; Total Potential Function-----------------------...2 or ^ (Zeta) Z ^ + (A) pv -- Ts Saturated Liquid at saturation . pressure and temperature; Liquid in contact with Vapor.,, Subf Dry Saturated Vapor; Dry Satu rated Gas at saturation pres sure and temperature; Vapor in contact with Liquid............... This system, carried to a logical conclusion, requires also subscripts for Liquid in contact with Solid, .Solid in contact with Vapor and Vapor in con Sub* tactwithSolid. However, these subscripts are not assigned at this time. Pairs of subscripts would also denote values for fusion or melting and sublima tion. Conditions at Critical Point_____ Sube Vaporization Values at Constant Pressure; Differences between Values forSaturated Vaporand Saturated Liquid at the same pressure. ............... ..... ...... . Subfg Heat Content of Saturated Liquid; Total Heat of Satu rated Liquid; Enthalpy of Sat urated 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................ he Various Values for Saturation; ' Various Values for Vaporiza tion, according to above rules......,,..........................jft, tr*. vig. etc. Saturation Pressure; Saturation Temperature...................Pi and Vi or Pg and Tg Heat of Vaporization at Constant pressure........... ................... L or htg Heat of Fusion; Heat of Sub limation, may be denoted by subscripts affixed to the sym bols Lor k. Gas Constant in equation pv = R7\_.................................. R Two values are in customary use. The first is the universal constant, corresponding to u in the above equation as volume . per mol (product of molecular weight and volume per unit weight). The second is the particular value fora given gas, corresponding to t as volume per unit weight. The second 528 Chapter 34--Symbols and Abbreviations value is the first value divided by molecular weight M. If de sired, a prime or a subscript may be used to distinguish be tween the two values. Quality of Steam, pounds of dry steam per pound of mixture-.... x Exponent of Polytropic expan sion in expression, pvn => const, Joule-Thotnson coefficient. a = (dT/dp)h-...............-......... Adiabatic Factor...... .................... n a (mu) Y Symbols for Heat Transmission6 Terms ending "ivity" designate properties independent of size or shape, sometimes called "specific properties." Examples are--conductivity and resistivity. Terms ending "ance" designate quantities depending not only on the material, but also upon size and shape, sometimes called "total quantities." Examples are--con ductance and transmittance. Terms ending "ion" designate rate of .heat transfer. Examples are--conduction and transmission. Area-..-........................................... Temperature. F or C.................... Temperature, F abs or K............ Length of path of beat flow, thickness..................... ..... .......... Total Quantity of Heat Trans ferred--__.................................... Thermal Transmission (heat transferred per unit time)_____ q -- <?/tirae A t T L Q q Thermal Conductivity (heat transferred per unit time per unit area, and per degree per unit length)................................ k _ /* (I. - t,)/L k Thermal Resistivity...................... Thermal Resistance (degrees, per unit of heat transferred per unit time per unit area............ .. 1/fc R Thermal Conductance (heat transferred per unit time per unit area, per degree)................ C J_= q/A L= t\- t* Film Conductance (heat trans ferred per unit time per unit area, per degree)........................ / Film Resistance (degrees per unit of heat transferred per unit time per unit area).................... 1// 1- <i -- li / = dJA Thermal Transmittance, or Co efficient of Heat Transfer (heat transferred per unit time per unit area, per degree)________ U ABBREVIATIONS FOR ENGINEERING AND SCIENTIFIC TERMS' Fundamental Rules lor Formation and Use Abbreviations should be used sparingly in text and with regard to the context and to the training of the reader. Terras denoting units of measure are abbreviated in the text only when preceded by the amounts indicated in numerals; thus "several inches," "one inch," "12 in." In tablular matter, specifications, maps, drawings, and texts for special purposes, the use of abbreviations is governed by the desirability of conserving space. Do not begin a sentence with a numeral followed by an abbreviation. Avoid capitals in abbreviations except in words normally capitalized. Hyphenated compound words call for hyphenated abbreviations; thus "hp-hr." With but few exceptions of abbreviations in common usage, the singular only is used; thus "in." for "inches," not "ins."; but No., Nos., Fig., Figs. Joint.report of the Committee on Heat Transmission, National Research Council and Subcommittee on Symbols for Heat and Thermodynamics. American Standards Association. Proposed Standard prepared by Sectional Committee on Scientific and Engineering Symbols and Abbreviations. 529