Document 84Vpna7wDrzz7XdvoJnvrqre

American Society of Heating and Ventilating Engineers Guide, 1931 Relative kinematic viscosity...;________ Time in seconds obtained from a vis cosity measurement with a specific instrument, from which viscosity may be computed by appropriate formulas______________ _______ ______ v/vw . / Symbols for General Thermodynamics Mechanical equivalent of heat______ ... j Heat equivalent of work________ 1/J or A Ordinary temperature, F or C (6 is pre ferably used only when t is used for Time in the same dis cussion)0 (theta) or t Absolute temperature, F abs or K..0 or (0 (capital theta) is preferably used ' only when 6 is used for ordinary temperature]. T Gas Constant in equation pv *= RT___R Two values are in customary use. , The first is the universal constant, corresponding to v in the above equa tion as volume per mol (product of molecular weight and volume per . unit weight). The second is the par*ticular value for a given gas, corre sponding to v as volume per unit weight. The second value is the first value divided by molecular weight Af. If desired, a prime or a subscript may be used to distinguish between the two values. Quality of Steam, pounds of dry steam per pound of mixture._____ ___________ x Exponent of Polytropic expansion, Pvn ** const- n Joule-Thomson coefficient, [l = (dT/dp)h-------------------------- (mu), (i Adiabatic Factor.................. Y Symbols for the Thermodynamic Quantities Entropy. (The capital should be used for any weight, and small letter, for unit weight)S' or. s Internal Energy;Intrinsic Energy. The capital should be used for any weight and the small letter for unit weight............. --.............................. U or u . Heat Content; Total Heat; Enthalpy. The capital should be used for any weight and the small letter for unit, weight..H or ` h h = u A pv . Helmholtz Free Energy; Internal Po tential Function_______ ____ ____(psi) = u -- Ts it Gibbs Function; Total Potential Func tion-------------------------------...s or. (Zeta) z = u-\-Apv -- Ts Symbols for Saturation, Vaporization, Etc. Saturated liquid at saturation pressure and temperature; Liquid in contact with vapor.________________ subscript f Dry saturated vapor; dry saturated gas at saturation pressure and tempera ture; Vapor in contact with liquid------- i-------------------------- subscript This system, carried to a logical conclusion, requires also subscripts for Liquid in contact with Solid. Solid in contact with Vapor and g Vapor in contact with Solid. How ever, these subscripts are not as signed at this time. Pairs of sub scripts would also denote values for fusion or melting and sublimation. Conditions at critical point....fc<rt{ Vaporization values at constant pres sure; Differences between values for saturated vapor and saturated liquid at the same pressure________ subscript ig Heat content of saturated liquid; Total heat of saturated liquid; Enthalpy of saturated liquid, sometimes called heat of the liquid____________________ ht Heat content of dry saturated vapor; Total heat of dry saturated vapor; Enthalpy of dry saturated vapor____ hg Various values for saturation; Various values for vaporization, according to . above rules___________________ if, ve, vtg Saturation pressure; Saturation tem perature-------------------- Pt, tt and Tt or pe. lg and Tg Heat of vaporization at constant pres sureL or htg Heat of Fusion and Heat of sublima tion may be denoted by subscipts affixed to the symbols L or h. Symbols for Heat Transmission* Terms ending "ivity" designate properties independent of size or shape, sometimes called "specific properties." Examples are--conductivity and resistivity. `Joint report of the Committee on Heat Transmission, National Research Council and Subcommittee on Symbols for Heat and Thermodynamics, American Standards Association. 8 Chapter 1----Abbreviations; Symbols and Drafting Standards 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........................ ........ -............................. A Temperature, F or C----- --___ ________ t Temperature. F abs or K--------------- ----- T Length of path of heat flow, thickness.. L Total Quantity of heat transferred------- Q Time (when t is used for tempera ture.______ ___(tau) t Thermal transmission (heat transferred per unit time)__--__ .....----- -------- ------- Q . ff = Qh Thermal conductivity (heat transferred per unit time per unit area, and per degree per unit lenth) k k_ (11 - ti)/C Thermal resistivity l/k Thermal resistance (degrees, per unit of heatfcransferred per unit time)____ R R. = `JZJl=L qkA Thermal conductance (heat transferred per unit time, per degree)________ ___ C kA c = iT L (i Thermal conductance per unit area, sometimes called Unit Conductance (heat transferred per unit time per .. unit area, per degree)--....... --............. C.< rC CA"a 1 q _k RA A ih-tt) L Surface coefficient of heat transfer, Film coefficient of heat transfer. In dividual coeffiaent of heat transfer (heat transferred per unit time per unit area, per degree).......-............. ...... h * r=7, (In general h is not equal to k/L, where L is the actual thickness of the fluid film). Thermal transmittance per unit area. Overall coefficient of heat transfer (heat transferred per unit time per unit area, per degree overall)............... q/A U = ti - tt U SYMBOLS FOR HEATING AND VENTILATING DRAWINGS* 1. The objects of this standard set of symbols are to insure the correct interpretation of drawings and to conserve drafting room time by establishing simple and unmistakable symbols for the component parts of the heating and ventilating systems,. In preparing the list of symbols an effort has been made to follow existing practice in so far as possible but the list cannot be expected to match exactly the existing practice of every drafting room. 2. Simplicity, ease of execution and unmistakable identification were carefully con sidered in selecting the symbols. Uncommon fittings and appliances such as vacuum pumps, separators, etc., have purposely been omitted in order to produce a list which can be easily remembered. It is assumed that when the scale of the drawing permits, the valves and fittings will be drawn to scale and a conventional representation is then unnecessary. 3' High pressure steam supply pipe --!--' 4. Low pressure steam supply pipe ----------------------- 5. Hot water pipe--flow ------------ --------------- 6. Return pipe--steam or water -------- ------------ 7. Air vent line From A.S.H.V.E. Cods of Minimum Requirements for the Heating and Ventilation of Buildings. 9