|
In the last five to six decades, professionals and scientists using the metric system of units defined the standard reference conditions of temperature and pressure for expressing gas volumes as being 0C (273.15K; 32.00F) and 101.325kPa (1atm or 760Torr). During those same years, the most commonly used standard reference conditions for people using the imperial or U.S. customary systems was 60F (15.56C; 288.71K) and 14.696psi (1atm) because it was almost universally used by the oil and gas industries worldwide. However, the above two definitions are no longer the most commonly used in either system of units Many different definitions of standard reference conditions are currently being used by organizations all over the world. The table below lists a few of them, but there are more. Some of these organizations used other standards in the past, such as IUPAC which currently defines standard reference conditions as being 0C and 100kPa (1bar) of pressure rather since 1982, in contrast to their old standard of 0C and 101.325kPa (1atm). Another example is from the oil industry. While a standard of 60F and 14.696psi was used in the past, the current usage (particularly in North America) is predominantly of 60F and 14.73psi. Natural gas companies in Europe and South America have adopted 15C (59F) and 101.325kPa (14.696psi) as their standard gas volume reference conditions. Also, the International Organization for Standardization (ISO), the United States Environmental Protection Agency (EPA) and National Institute of Standards and Technology (NIST) each have more than one definition of standard reference conditions in their various standards and regulations. The SATP used for presenting chemical thermodynamic properties (such as those published by the National Bureau of Standards) is standardized at 100kPa (1bar) but the temperature may vary and usually needs to be specified separately if complete information is desired (see standard state). Some standards are specified at certain humidity level. Table 1: Standard reference conditions in current use Publishing or establishing entity IUPAC (former definition), NIST, ISO 10780 ICAO's ISA, ISO 13443, EEA, EGIA SPE, U.S. OSHA, SCAQMD EGIA, OPEC, U.S. EIA U.S. Army Standard Metro ISO 2314, ISO 3977-2 AMCA, air density = 0.075 lbm/ft. This AMCA standard applies only to air. EGIA: Electricity and Gas Inspection Act (of Canada) SATP: Standard Ambient Pressure and Temperature In aeronautics and fluid dynamics the term "International Standard Atmosphere" is often used to denote the variation of the principal thermodynamic variables (pressure, temperature, density, etc.) of the atmosphere with altitude at mid latitudes. Due to the fact that many definitions of standard temperature and pressure differ in temperature significantly from standard laboratory temperatures (e.g., 0C vs. ~25C), reference is often made to "standard laboratory conditions" (a term deliberately chosen to be different from the term "standard conditions for temperature and pressure", despite its semantic near identity when interpreted literally). However, what is a "standard" laboratory temperature and pressure is inevitably culture-bound, given that different parts of the world differ in climate, altitude and the degree of use of heat/cooling in the workplace. For example, schools in New South Wales, Australia use 25C at 100kPa for standard laboratory conditions. ASTM International has published Standard ASTM E41- Terminology Relating to Conditioning and hundreds of special conditions for particular materials and test methods. Other standards organizations also have specialized standard test conditions. Molar volume of a gas It is equally as important to indicate the applicable reference conditions of temperature and pressure when stating the molar volume of a gas as it is when expressing a gas volume or volumetric flow rate. Stating the molar volume of a gas without indicating the reference conditions of temperature and pressure has no meaning and it can cause confusion. The molar gas volumes can be calculated with an accuracy that is usually sufficient by using the universal gas law for ideal gases. The usual expression is: which can be rearranged thus: where (in SI metric units): = the absolute pressure of the gas, in Pa = amount of substance, in mol = the volume of the gas, in m3 = the absolute temperature of the gas, in K = the universal gas law constant of 8.3145 m3Pa/(molK) or where (in customary USA units): = the absolute pressure of the gas, in psi = number of moles, in lbmol = the volume of the gas, in ft3/lbmol = the absolute temperature of the gas absolute, in R = the universal gas law constant of 10.7316 ft3psi/(lbmolR) The molar volume of any ideal gas may be calculated at various standard reference conditions as shown below: V/n = 8.3145 273.15 / 101.325 = 22.414m3/kmol at 0C and 101.325kPa V/n = 8.3145 273.15 / 100.000 = 22.711m3/kmol at 0C and 100kPa V/n = 8.3145 298.15 / 101.325 = 24.466m3/kmol at 25C and 101.325kPa V/n = 8.3145 298.15 / 100.000 = 24.790m3/kmol at 25C and 100kPa V/n = 10.7316 519.67 / 14.696 = 379.48ft3/lbmol at 60F and 14.696psi V/n = 10.7316 519.67 / 14.730 = 378.61ft3/lbmol at 60F and 14.73psi The technical literature can be confusing because many authors fail to explain whether they are using the universal gas law constant R, which applies to any ideal gas, or whether they are using the gas law constant Rs, which only applies to a specific individual gas. The relationship between the two constants is Rs = R / M, where M is the molecular weight of the gas. The US Standard Atmosphere uses 8.31432m3Pa/(molK) as the value of R for all calculations. (See Gas constant) a b c A. D. McNaught, A. Wilkinson (1997). Compendium of Chemical Terminology, The Gold Book (2nd ed.). Blackwell Science. ISBN 0865426848. "Standard conditions for gases: Temperature, 273.15K [...] and pressure of 105pascals. IUPAC recommends that the former use of the pressure of 1 atm as standard pressure (equivalent to 1.01325 105 Pa) should be discontinued." A. D. McNaught, A. Wilkinson (1997). Compendium of Chemical Terminology, The Gold Book (2nd ed.). Blackwell Science. ISBN 0865426848. "Standard pressure: Chosen value of pressure denoted by po or p. In 1982 IUPAC recommended the value 105Pa, but prior to 1982 the value 101325 Pa (=1atm) was usually used." ISO (1994), ISO 10780:1994: Stationary source emissions - Measurement of velocity and volume flowrate of gas streams in ducts, ; a b Robert C. Weast (Editor) (1975). Handbook of Physics and Chemistry (56th ed.). CRC Press. pp.F201206. ISBN 0-87819-455-X. a b "Natural gas Standard reference conditions", ISO 13443, International Organization for Standardization, Geneva, Switzerland ISO Standards Catalogue "Extraction, First Treatment and Loading of Liquid & Gaseous Fossil Fuels", Emission Inventory Guidebook B521, Activities 050201 - 050303, September 1999, European Environmental Agency, Copenhagen, Denmark Emission Inventory Guidebook a b "Electricity and Gas Inspection Act", SOR/86-131 (defines a set of standard conditions for Imperial units and a different set for metric units) Canadian Laws "Standards of Performance for New Sources", 40 CFR--Protection of the Environment, Chapter I, Part 60, Section 60.2, 1990 New Source Performance Standards "Design and Uncertainty for a PVTt Gas Flow Standard", Journal of Research of the National Institute of Standards and Technology, Vol.108, Number 1, 2003 NIST Journal "National Primary and Secondary Ambient Air Quality Standards", 40 CFR--Protection of the Environment, Chapter I, Part 50, Section 50.3, 1998 National Ambient Air Standards "Table of Chemical Thermodynamic Properties", National Bureau of Standards (NBS), Journal of Physics and Chemical Reference Data, 1982, Vol. 11, Supplement 2. "Glossary", 2002, Compressed Air and Gas Institute, Cleveland, OH, USA Glossary a b The SI Metric System of Units and SPE Metric Standard (Notes for Table 2.3, on PDF page 25 of 42 PDF pages, define two different sets of reference conditions, one for the standard cubic foot and one for the standard cubic meter) "Air Intake Filters", ISO 5011:2002, International Organization for Standardization, Geneva, Switzerland ISO "Storage and Handling of Liquefied Petroleum Gases" and "Storage and Handling of Anhydrous Ammonia", 29 CFR--Labor, Chapter XVII--Occupational Safety and Health Administration, Part 1910, Sect. 1910.110 and 1910.111, 1993 Storage/Handling of LPG "Rule 102, Definition of Terms (Standard Conditions)", Amended December 2004, South Coast Air Quality Management District, Los Angeles, California, USA SCAQMD Rule 102 "Annual Statistical Bulletin", 2004, Editor-in-chief: Dr. Omar Ibrahim, Organization of the Petroleum Exporting Countries, Vienna, Austria OPEC Statistical Bulletin "Natural Gas Annual 2004", DOE/EIA-0131(04), December 2005, U.S. Department of Energy, Energy Information Administration, Washington, D.C., USA Natural Gas Annual 2004 Sierra Bullets L.P.. "Chapter 3 Effects of Altitude and Atmospheric Conditions". Rifle and Handgun Reloading Manual, 5th Edition. ;"Effects of Altitude and Atmospheric Conditions", Exterior Ballistics Section, Sierra's "Rifle and Handgun Reloading Manual, 5th Edition", Sedalia, MO, USA Exterior Ballistics The pressure is specified as 750 mmHg. However, the mmHg is temperature dependant, as mercury expands as temperature goes up. Here the values for the 0-20C range are given. "Gas turbines Procurement Part 2: Standard reference conditions and ratings", ISO 3977-2:1997 and "Gas turbines - Acceptance tests", ISO 2314:1989, Edition 2, International Organization for Standardization, Geneva, Switzerland ISO ANSI/AMCA Standard 210, "Laboratory Methods Of Testing Fans for Aerodynamic Performance Rating", as implied here: when accessed on October 17, 2007 The standard is given as 29.92 inHg at an unspecified temperature. This most likely corresponds to a standard pressure of 101.325 kPa, converted into ~29.921 inHg at 32F) Peter Gribbon (2001). Excel HSC Chemistry Pocket Book Years 11-12. Pascal Press. ISBN 1-74020-303-8. Fundamental Physical Properties: Molar Volumes (CODATA values for ideal gases as listed on a NIST website page) ISO 1 standard reference temperature for geometric product specifications "Standard conditions for gases" from the IUPAC Gold Book. "Standard pressure" from the IUPAC Gold Book. "STP" from the IUPAC Gold Book. "Standard state" from the IUPAC Gold Book. We are high quality suppliers, our products such as China LED Tube Lights , LED FloodLights for oversee buyer. To know more, please visits LED Tunnel Light.
Related Articles -
China LED Tube Lights, LED FloodLights,
| 
