|
Saturation vapor density (SVD) is a concept closely tied with saturation vapor pressure. It is useful for getting an exact quantity of water vapor in the air from a relative humidity (RH). Given an RH percentage, the density of water in the air is given by . Alternatively, RH can be found by . As Relative Humidity is a dimensionless quantity (often expressed in terms of a percentage), vapor density can be stated in units of grams or kilograms per cubic meter. For low temperatures (below 400 kelvins or so), SVD can be approximated from the SVP by the ideal gas law: where is the number of moles, which is related by density by , where is the mass of water present and is the molar mass of water (18.01528 grams/mole). Thus, setting to 1 cubic meter, we get = = density. is the gas constant, and is the temperature in kelvin. The values shown at hyperphysics-sources〔http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html〕 indicate clearly that the saturated vapor density is stated to be 4.85 g/m3 at 273 K at which the saturated vapor pressure is 4.58 mm of Hg or 610.616447 Pa (760 mm of Hg ≈ 1 atm = 1.01325 * 105 Pa). Therefore, for particular mole number and volume the saturated vapor pressure shall not change if the temperature is not changed. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Saturation vapor density」の詳細全文を読む スポンサード リンク
|