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Encyclopedia > Standard conditions for temperature and pressure

In chemistry and other sciences, STP or standard temperature and pressure is a standard set of conditions for experimental measurements, to enable comparisons to be made between sets of data. Internationally, the current STP defined by the IUPAC (International Union of Pure and Applied Chemistry) is an absolute pressure of 100.00 kPa (1 bar) and a temperature of 273.15 K (0 °C).[1] Other organizations have established a variety of alternative definitions for the standard reference conditions of temperature and pressure, such as the SATP amongst others. Chemistry - the study of interactions of chemical substances with one another and energy based on the structure of atoms, molecules and other kinds of aggregrates Chemistry (from Egyptian kÄ“me (chem), meaning earth[1]) is the science concerned with the reactions, transformations and aggregations of matter, as well as accompanying... Part of a scientific laboratory at the University of Cologne. ... The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ... The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin in Canberra, Australia. ... Wikipedia does not yet have an article with this exact name. ... This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ...


In industry and commerce, it is necessary to define the standard reference conditions of temperature and pressure when expressing a gas volume or a volumetric flow rate because the volume of a gas varies with the temperature and pressure of the gas. The available data on the various definitions of standard reference conditions clearly indicates that the IUPAC's STP is not a universally accepted definition of the standard conditions of temperature and pressure. For that reason, simply stating that a gas flow rate is 10,000 m³/h (i.e. cubic meters per hour) at "standard conditions" or at "STP" has no meaning unless the reference conditions that were applied are clearly stated. This article does not cite any references or sources. ...


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. Six F-16 Fighting Falcons with the U.S. Air Force Thunderbirds aerial demonstration team fly in delta formation in front of the Empire State Building. ... Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluids (liquids and gases) in motion. ... The International Standard Atmosphere (ISA) is a model of the standard variation of pressure, temperature, density, and viscosity with altitude in the Earths atmosphere. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ...

Contents

Definitions used in the past

For a great many years, most engineers, chemists, physicists and other scientists using the metric system of units defined the standard reference conditions of temperature and pressure for expressing gas volumes as being 0 °C (273.15 K) and 101.325 kPa (i.e., 1 atmosphere of absolute pressure). During those same years, the most commonly used standard reference conditions for people using the Imperial or customary USA system of units was 60 °F (520 °R) and 14.696 psia (i.e., 1 atmosphere of absolute pressure) because it was almost universally used by the oil and gas industries worldwide. The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... Wikipedia does not yet have an article with this exact name. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... The Imperial units or the Imperial system is a collection of English units, first defined in the Weights and Measures Act of 1824, later refined (until 1959) and reduced. ... The U.S. customary units (more commonly known in the US as English units or standard units) are the non-metric units of measurement that are presently used in the United States, in some cases alongside the metric system of units. ... Fahrenheit is a temperature scale named after the German-Dutch physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ... Rankine is a now rarely used temperature scale named after the Scottish engineer and physicist William John Macquorn Rankine, who proposed it in 1859. ... A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in²) is a non-SI unit of pressure based on avoirdupois units. ...


The above two definitions are no longer the most commonly used definitions in either the metric, Imperial or the customary USA system of units. Some of the many different definitions currently in use are presented in the next section.


It was also common in the past, when using the metric system of units, to refer to a Normal Cubic Meter (Nm³) and to define it as being at 0 °C (273.15 K) and 101.325 kPa (i.e. 1 atmosphere of absolute pressure). As shown in the following section, that notation is no longer appropriate unless the specific reference conditions are explicitly stated, since there are currently many different metric system definitions of what constitutes standard reference conditions.


In the same manner, it is also no longer appropriate to refer to a standard cubic foot (scf) unless the specific reference conditions are explicitly stated, again because there are currently many different definitions of the standard reference condition in both the Imperial and the customary U.S. systems of units. In particular, OPEC and a majority of the natural gas industry in North America have adopted 60 °F and 14.73 psia as their standard reference conditions for expressing natural gas volumes and flow rates (rather than the 60 °F and 14.696 psia commonly used previously). A standard cubic foot is a measure of quantity of gas, equal to a cubic foot of volume at 60 degrees Fahrenheit and either 14. ... Logo The Organization of the Petroleum Exporting Countries (OPEC) is made up of Algeria, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates, and Venezuela; since 1965 its international headquarters have been in Vienna, Austria. ...


Definitions in current use

There are a great many different definitions of the standard reference conditions currently being used. Table 1 presents twelve such variations of standard condition definitions - and there are quite a few others as well.


As shown in the table, the IUPAC (International Union of Pure and Applied Chemistry) currently defines standard reference conditions as being 0 °C and 1 bar (i.e., 100 kPa) of absolute pressure rather than the 1 atmosphere (i.e. 101.325 kPa) of absolute pressure used in the past. In fact, the IUPAC's current definition has been in existence since 1982.[2] The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ...


As further shown in the table, the oil and gas industries have to a large extent changed from their past usage of 60 °F and 14.696 psia to their current usage of 60 °F and 14.73 psia. This is especially true of the natural gas industry in North America.


For the SATP used in presenting chemical thermodynamic properties (such as those published by the National Bureau of Standards as included in Table 1) that the pressure is standardized at 1 bar (100 kPa) but the temperature may vary and needs to be specified separately. As a non-regulatory agency of the United States Department of Commerce’s Technology Administration, the National Institute of Standards (NIST) develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. ...


It should also be noted that 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. This article does not cite any references or sources. ... EPA redirects here. ... NIST logo The National Institute of Standards and Technology (NIST, formerly known as The National Bureau of Standards) is a non-regulatory agency of the United States Department of Commerce’s Technology Administration. ...


The table makes it quite obvious that it is absolutely necessary to clearly state the temperature and pressure reference conditions whenever expressing a gas volume or gas volumetric flowrate. It is equally important to state whether the gas volume is expressed on a dry basis or a wet basis. As noted in the table, some of the current definitions of the reference conditions include a specification of the percent relative humidity (% RH).

Table 1: Standard reference conditions in current use
Temperature Absolute pressure Relative humidity Publishing or establishing entity
°C kPa % RH
0 100.000   IUPAC (present definition)[1]
0 101.325   IUPAC (former definition),[1] NIST,[3] ISO 10780[4]
15 101.325 0 [4], [5] ISA,[5] ISO 13443,[6] EEA,[7] EGIA[8]
20 101.325   EPA,[9] NIST[10]
25 101.325   EPA[11]
25 100.000   SATP[12]
20 100.000 0 CAGI[13]
15 100.000   SPE[14]
°F psia  % RH
60 14.696   SPE,[14] OSHA,[15] SCAQMD[16]
60 14.73   EGIA,[8] OPEC,[17] EIA[18]
59 14.503 78 Army Standard Metro[19]
59 14.696 60 ISO 2314, ISO 3977-2[20]

Notes:

  • 101.325 kPa = 1 atmosphere = 1.01325 bar ≈ 14.696 psi
  • 100.000 kPa = 1 bar ≈ 14.504 psi
  • 14.503 psi ≈ 750 mmHg ≈ 100.0 kPa ≈ 1 bar
  • 14.696 psi ≈ 1 atm = 101.325 kPa
  • 14.73 psi ≈ 30 inHg ≈ 1.0156 bar ≈ 101.560 kPa
  • All pressures are absolute pressures (not gauge pressures)
  • 59 °F = 15 °C
  • 60 °F ≈ 15.6 °C
  • dry = 0 percent relative humidity = 0 % RH

The full names of the entities listed in Table 1:

IUPAC logo The International Union of Pure and Applied Chemistry (IUPAC) (Pronounced as eye-you-pack) is an international non-governmental organization established in 1919 devoted to the advancement of chemistry. ... NIST logo The National Institute of Standards and Technology (NIST, formerly known as The National Bureau of Standards) is a non-regulatory agency of the United States Department of Commerce’s Technology Administration. ... The International Civil Aviation Organization (ICAO), an agency of the United Nations, develops the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. ... The International Standard Atmosphere (ISA) is a model of the standard variation of pressure, temperature, density, and viscosity with altitude in the Earths atmosphere. ... This article does not cite any references or sources. ... European Environment Agency (EEA), agency of the European Union devoted to establishing a monitoring network for the monitoring of the European environment. ... EPA redirects here. ... CAGI may refer to TsAGI, Russian Central Aerohydrodynamic Institute Compressed Air and Gas Institute, Cleveland, Ohio, [1], an industry association This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Society of Petroleum Engineers is a professional organization whose mission is to collect, disseminate, and exchange technical knowledge concerning the exploration, development and production of oil and gas resources, and related technologies for the public benefit; and to provide opportunities for professionals to enhance their technical and professional competence. ... OSHA logo The United States Occupational Safety and Health Administration (OSHA) is an agency of the United States Department of Labor. ... The Organization of the Petroleum Exporting Countries (OPEC) is made up of Algeria, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates and Venezuela; since 1965, its international headquarters have been in Vienna, Austria. ... The Energy Information Administration (EIA), as part of the U.S. Department of Energy, collects and disseminates data on energy reserves, production, consumption, distribution, prices, technology, and related international, economic, and financial matters. ...

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[21] 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 much 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: The ideal gas law, or universal gas equation, is an equation of state of an ideal gas. ...


P cdot V = n cdot R cdot T


…which can be rearranged thus:


frac{V}{n} = frac{R cdot T}{P}


where (in SI metric units):

P = the gas absolute pressure, in Pa
n = number of moles, in mol
V / n = the gas molar volume, in m³/mol
T = the gas absolute temperature, in K
R = the universal gas law constant of 8.3145 m³·Pa/(mol·K)

or where (in customary USA units): The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... The gas constant (also known as the universal or ideal gas constant, usually denoted by symbol R) is a physical constant used in equations of state to relate various groups of state functions to one another. ...

P = the gas absolute pressure, in psia
n = number of moles, in lbmol
V / n = the gas molar volume, in ft³/lbmol
T = the gas absolute temperature, in °R
R = the universal gas law constant of 10.7316 ft³·psia/(lbmol·°R)

The molar volume of any ideal gas may be calculated at various standard reference conditions as shown below: A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in²) is a non-SI unit of pressure based on avoirdupois units. ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... Rankine is a now rarely used temperature scale named after the Scottish engineer and physicist William John Macquorn Rankine, who proposed it in 1859. ...

  • V / n = 8.3145 × 273.15 / 101.325 = 22.414 m³/kmol at 0 °C and 101.325 kPa absolute pressure
  • V / n = 8.3145 × 273.15 / 100.000 = 22.711 m³/kmol at 0 °C and 100 kPa absolute pressure
  • V / n = 10.7316 × 519.67 / 14.696 = 379.48 ft³/lbmol at 60 °F and 14.696 psia absolute pressure
  • V / n = 10.7316 × 519.67 / 14.730 = 378.61 ft³/lbmol at 60 °F and 14.73 psia absolute pressure

The technical literature can be very 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.


It may be of interest to note that the US Standard Atmosphere still uses 8.31432 m³·Pa/(mol·K) as the value of R for all calculations. (See Gas constant) The U.S. Standard Atmosphere is a series of models that define values for atmospheric temperature, density, pressure and other properties over a wide range of altitudes. ... The gas constant (also known as the universal or ideal gas constant, usually denoted by symbol R) is a physical constant used in equations of state to relate various groups of state functions to one another. ...


References

  1. ^ a b c "Compendium of Terminology", 2nd Edition, 1997, IUPAC Secretariat, Research Triangle Park, P.O. Box 13757, NC, USA (former and present definitions)  IUPAC Compendium
  2. ^ IUPAC recommended standard pressure of 1 bar in 1982 IUPAC Compendium
  3. ^ "NIST Standard Reference Data Base 7 Users Guide", December 1969, NIST, Gaithersburg, MD, USA  NIST Data Base 7
  4. ^ "Stationary source emissions – Measurement of velocity and volume flow rate of gas streams in ducts", ISO 10780, International Organization for Standardization, Geneva, Switzerland  ISO
  5. ^ "Handbook of Physics and Chemistry", 56th Edition, pp.F201-F206, CRC Press, Boca Raton, FL, USA
  6. ^ "Natural gas – Standard reference conditions", ISO 13443, International Organization for Standardization, Geneva, Switzerland  ISO
  7. ^ "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
  8. ^ 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
  9. ^ "Standards of Performance for New Sources", 40 CFR--Protection of the Environment, Chapter I, Part 60, Section 60.2, 1990  New Source Performance Standards
  10. ^ "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
  11. ^ "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
  12. ^ "Table of Chemical Thermodynamic Properties", National Bureau of Standards (NBS), Journal of Physics and Chemical Reference Data, 1982, Vol. 11, Supplement 2.
  13. ^ "Glossary", 2002, Compressed Air and Gas Institute, Cleveland, OH, USA  Glossary
  14. ^ a b "The SI Metric System of Units and SPE Metric Standard (Notes for Table 2.3 on page 25)", June 1982, Richardson, TX, USA (defines standard cubic foot and standard cubic meter)  SPE
  15. ^ "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
  16. ^ "Rule 102, Definition of Terms (Standard Conditions)", Amended December 2004, South Coast Air Quality Management District, Los Angeles, California, USA  SCAQMD Rule 102
  17. ^ "Annual Statistical Bulletin", 2004, Editor-in-chief: Dr. Omar Ibrahim, Organization of the Petroleum Exporting Countries, Vienna, Austria  OPEC Statistical Bulletin
  18. ^ "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
  19. ^ "Effects of Altitude and Atmospheric Conditions", Exterior Ballistics Section, Sierra's "Rifle and Handgun Reloading Manual, 5th Edition", Sedalia, MO, USA  Exterior Ballistics
  20. ^ "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
  21. ^ Fundamental Physical Properties: Molar Volumes (CODATA values for ideal gases as listed on a NIST website page)

This article does not cite any references or sources. ... CODATA (Committee on Data for Science and Technology) was established in 1966 as an interdisciplinary committee of the International Council of Science (ICSU), formerly the International Council of Scientific Unions. ... As a non-regulatory agency of the United States Department of Commerce’s Technology Administration, the National Institute of Standards (NIST) develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. ...

External links


  Results from FactBites:
 
Standard conditions for temperature and pressure - Wikipedia, the free encyclopedia (1681 words)
In chemistry and other sciences, STP or standard temperature and pressure is a standard set of conditions for experimental measurements, to enable comparisons to be made between sets of data.
In industry and commerce, it is necessary to define the standard reference conditions of temperature and pressure when expressing a gas volume or a volumetric flow rate because the volume of a gas varies with the temperature and pressure of the gas.
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.
Standard temperature and pressure - definition of Standard temperature and pressure in Encyclopedia (315 words)
Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time.
In chemistry, the term standard temperature and pressure (abbreviated STP) denotes an exact reference temperature of 0°C (273.15 K) and pressure of 1 atm (defined as 101.325 kPa).
When used to calculate performance at any pressure altitude other than sea level, the temperature is adjusted using the prescribed lapse rate which is -6.5 °C/km for the first 11 km.
  More results at FactBites »


 

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