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Heating Ventilating Air Conditioning Guide 1938 HeadH or h Heat content, Total heat, Enthalpy. (Thecapital should be used for any weight and the small letter for unit weight.)Ef or h Heat content of saturated liquid, Total heat of saturated liquid, Enthalpy of saturated liquid, sometimes called heat of the liquid.. M Heat content of dry saturated vapor, Total heat of dry saturated vapor, Enthalpy of dry saturated vapor. ..hg Heat of vaporization at constant pressure.- J. or htt Horsepower.. hp Horsepower-hour.. -hp-hr Inch_____________ Inch-poundIndicated horsepowerindicated horsepower-hour.. . in.-lb -ihp ..ihp-hr Internal energy, Intrinsic energy. (The capital should be used for any weight and the smairletter for unit weight.)Uor u KilogramL_________________________________ kg Kilowatt-- Kilowatthour- ___kw _kwhr Length of path of heat flow, thickness.. Load, total___________________________ Mass... Mechanical efficiency--------------Mechanical equivalent of heat.. Melting point--------------- ---..... ..W ...m _m __ 1 ____ mp Meter_____ __ ________________ MicronMiles per hour.. -U (mu) ___ mph Minute.. Molecular weight- Mol______________ OuncePower, Horsepower, Work per unit time. ..mol- wt ____ mol ______ oz ______ P Pressure, Absolute pressure, Gage pressure. Force per unit area Quantity (total) of fluid, water, gas, heat; Quantity by volume; Total quantity of heat transferred.. Quality of steam, Pounds of dry steam per pound of mixture- Revolutions per minute.. Saturated liquid at saturation pressure and temperature, Liquid in contact with vaporSubscript { Q -_x jpm Specific gravitysp gr Specific heatsp ht or c Specific heat at constant pressureCp Specific heat at constant volumeCv Specific volume, Volume per unit weight, Volume per unit massv Square foot______________:sq ft Square inch________________________________ __________sq in. Temperature (ordinary) F or C, (Theta is used preferably only when t is used for Time in the same discussion.)______________________________________ f or 8 (theta) Temperature (absolute) F abs or K. (Capital theta is used preferably only when small theta is used for ordinary temperature.)T or 0 (capital theta) Thermal conductance* (heat transferred per unit time per degree)_______ __________--C r___ 1_ _ kA _ q R L t, -t. Thermal conductance per unit area. Unit conductance (heat transferred per . unit time per unit area per degree)---------------------------------------------------------------- Ca r = JL _ _L g =A a A RA A(h-t,), L `Terms ending isiiy designate properties independent of size or shape, sometimes called specific proper* ties. Examples are--conductivity and resistivity. Terms ending once designate quantities depending not only on the material, but also upon size and shape, sometimes called total quantities. Examples areconductance and transmittance. Terms ending ion designate rate of heat transfer. Examples are--con duction and transmission. 832 ' Chapter 45. Terminology Thermal conductivity (heat transferred per unit time per unit area, and per degree per unit length); g k= A . ~.) L .k Surface coefficient of heat transfer, Film coefficient of heat transfer, Individual coefficient of heat transfer (heat transferred per unit time per unit area per degree) JL A f h - It (In genera] / is not equal to k/L, where L is the actual thickness of the fluid film.) Over-all coefficient of heat transfer, Thermal transmittance per unit area (heat transferred per unit time per unit area per degree over-all)------------------ ------------- V _g A V = <i - t. Thermal transmission (heat transferred per unit time). Thermal resistance (degrees per unit of heat transferred per unit time)R Thermal resistivity. Vaporization values at constant pressure. Differences between values for saturated vapor and saturated liquid at the same pressureSubscript fg Velocity_____________________________ ______________________________________________ V Volume (total)V Volume per unit time, Rate at which quantity of material passes through a mn mft C~\ V. s --___ f.. __ -______ r I__, , _______________ ____ ______ ____ ______________ __ __ ___----___ --______ --____ W Watthour._____________________________________________________________________ __whr Weight of a major item, Total weight______________________________ _______________ W Weight rate, Weight per unit of power, Weight per unit of timeto Work (total);1_________________________________________ W CONVERSION EQUATIONS Fahrenheit degrees = 9/5 (centigrade degrees) + 32. Centigrade degrees = 5/9 (Fahrenheit degrees -- 32). Absolute temperature, expressed in Fahrenheit degrees = Fahrenheit degrees + 459.6. In heating and ventilating work, 460 is usually used. Absolute temperature, expressed in centigrade degrees = centigrade degrees + 273.1. 833