Tag Archives: ideal gas law

Gas Compressibility Factor Calculator Excel Spreadsheet

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Where to Find a Gas Compressibility Factor Calculator Excel Spreadsheet

To obtain a gas compressibility factor calculator Excel spreadsheet, click here to visit our spreadsheet store.  Look in the Fluid Properties category on the Download page.  This Excel spreadsheet is intended for calculation of the compressibility factor of a gas using the Redlich-Kwong equation of state. You can buy a convenient gas compressibility factor calculator Excel spreadsheet  for a very reasonable price.  This spreadsheet calculates the compressibility factor of a gas from the gas temperature, gas pressure, and the critical pressure and critical temperature of the gas.  It is available in either U.S. or S.I. units.  Read on for information about using a gas compressibility factor calculator Excel spreadsheet.

Background for Gas Compressibility Factor Calculator Excel Spreadsheet

The compressibility factor of a gas is used in several types of calculations including calculation of real gas density.  The Ideal Gas Law, PV = nRT, can be used to calculate the density of a gas that exhibits ideal gas behavior by introducing the molecular weight of the gas and solving for gas density to give:  ρ = MW*P/R*T.
For information on the use of the ideal gas to calculate gas density, see the article, “Air Density Calculator Excel Spreadsheet.”

Conditions required for ideal gas behavior are pressure << critical pressure and/or temperature >> critical temperature.  For gases that don’t exhibit ideal gas behavior, the compressibility factor, Z can be introduced to give:     ρ = Z*MW*P/R*T.

The Redlich-Kwong Equation of State

One possibility for a gas compressibility factor calculator Excel spreadsheet is through the use of the Redlich-Kwong equation of state, which is shown below:

Gas Compressibility Factor Calculator Excel Spreadsheet - Redlich-Kwong Equation of StateA, B, and h are constants calculated as shown.  The compressibility factor, Z, can be calculated for known values of the gas temperature, T, the gas temperature, P, and the critical temperature and pressure of the gas.  The temperatures should be in K and the pressures in atm for use of the equations given above.  Calculation of Z requires an iterative calculation because the equations can’t be solved explicitly for Z.

Example Gas Compressibility Factor Calculator Excel Spreadsheet

An example gas compressibility factor calculator Excel spreadsheet is partially shown in the image below.  This Excel spreadsheet can be used to calculate the compressibility factor of a gas, based on user input values for gas temperature, gas pressure, and the critical temperature and pressure of the gas.  This Excel spreadsheet, as well as others for fluid property calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.

Gas Compressibility Factor Calculator Excel Spreadsheet ScreenshotReferences

1. Otto Redlich, and J.N.S. Kwong, “On the Thermodynamics of Solutions. V. An Equation of State. Fugacities of Gaseous Solutions”, Chemical Reviews 44 pp. 233-244 (1949).

2. Bengtson, Harlan H.,  Redlich Kwong Compressibility Factor Spreadsheet, an informational online blog article.

Air Density Calculator Excel Spreadsheet

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Where to Find an Air Density Calculator Excel Spreadsheet

To find an air density calculator Excel spreadsheet to use as an air density calculator, click here to visit our spreadsheet store.  Why use an online calculator or look in tables, when you can get an air density calculator excel spreadsheet to use as an air density calculator here? Read on for information about Excel spreadsheets that can be used to calculate the density of air (and other gases) at different pressures and temperatures with the ideal gas law.

Gas density background for an Air Density Calculator Excel Spreadsheet

Pressure and temperature have significant effects on the density of gases, so some means of determining the density of air and other gases at specified temperatures and pressures is needed for a variety of fluid mechanics applications.  Fortunately, the ideal gas law provides a means of doing this for many gases over ranges of temperature and pressure that are of interest.

The Ideal Gas Law for use in an Air Density Calculator Excel Spreadsheet

A common form for the ideal gas law equation is PV = nRT, giving the relationship among T, the absolute temperature of the gas; P, its absolute pressure; V, the volume occupied by n moles of the gas; and R, the ideal gas law constant.

The density of the gas can be introduced into this equation, through the fact that molecular weight (MW) has units of mass/mole, so that n = m/MW.  This leads to the ideal gas law written as:  PV = (m/MW)RT.  Solving this equation for m/V (which is equal to the gas density, ρ) gives the following equation for gas density as a function of its MW, pressure and temperature:  ρ = (MW)P/RT.

A commonly used set of U.S. units for this equation is as follows:

ρ = density of the gas in slugs/ft3,

MW = molecular weight of the gas in slugs/slugmole (or kg/kgmole, etc.) (NOTE: MW of air = 29),

P = absolute gas pressure in psia (NOTE: Absolute pressure equals pressure measured by a guage plus atmospheric pressure.),

T = absolute temperature of the gas in oR (NOTE: oR = oF + 459.67)

R = ideal gas constant in psia-ft3/slugmole-oR.

For conditions under which air can be treated as an ideal gas (see the next section), the ideal gas law in this form can be used to calculate the density of air at different pressures and temperatures.

The air density calculator excel spreadsheet template shown in the screenshot below will calculate the density of a gas for specified molecular weight, pressure and temperature.   This Excelair density calculator excel spreadsheet spreadsheet is available at a very reasonable price in our spreadsheet store and can be used with either U.S. or S.I. units.  These spreadsheets also contain tables of critical temperature and critical pressure for several common gases.

But When Can I Use the Ideal Gas Law to Calculate the Density of Air?

A good question indeed, because air and other gases for which you may need a density value are real gases, not ideal gases.  It is fortunate, however, that many real gases behave almost exactly like an ideal gas over a wide range of temperatures and pressures.  The Critical Temp and Press for Air Density Calculator Excel Spreadsheetideal gas law works best for high temperatures (relative to the critical temperature of the gas) and low pressures (relative to the critical pressure of the gas).  See table at the left for values of critical temperature and critical pressure for several common gases.  For many practical, real situations, the ideal gas law gives quite accurate values for the density of air (and many other gases) at different pressures and temperatures.

S.I. Units for the Ideal Gas Law

The ideal gas law is a dimensionally consistent equation, so it can be used with any consistent set of units.  For SI units the ideal gas law parameters are as follows:

ρ = density in kg/m3,

P = absolute gas pressure in pascals (N/m2),

T = absolute temperature in oK (NOTE: oK = oC + 273.15)

R = ideal gas constant in Joules/kgmole-K

References:

1. Bengtson, Harlan H., Flow Measurement in Pipes and Ducts, An online PDH course for Professional Engineers

2. Munson, B. R., Young, D. F., & Okiishi, T. H., Fundamentals of Fluid Mechanics, 4th Ed., New York: John Wiley and Sons, Inc, 2002.

3. Applied Thermodynamics ebook, http://www.taftan.com/thermodynamics/

4. Bengtson, Harlan H., “Gas Property Calculator Spreadsheet,” an Amazon Kindle e-book.

 

Orifice and Venturi Flow Meter Calculations Spreadsheet

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Introduction to Orifice and Venturi Flow Meter Calculations Spreadsheet

For an orifice and venturi flow meter calculations spreadsheet, click here to visit our spreadsheet store.  Read on for information about Excel spreadsheets that can be used as orifice and venturi flow meter, pipe flow rate calculators.

Excel spreadsheets are convenient for differential pressure flow meter calculations,  for meters such as the commonly used orifice flow meter and venturi meter.  The general equation for differential pressure flow meters can be built into the spreadsheets with Excel formulas.  Also, for gas flow, the ideal gas law can be used to calculate the gas density based on its temperature, pressure, and molecular weight.  An Excel spreadsheet can also be used to calculate the orifice coefficient for anorifice meter with one of the ISO standard pressure tap configurations.

Background for an Orifice and Venturi Flow Meter Calculation Spreadsheet

Orifice and Venturi Flow Meter Calculations Spreadsheet diagramOrifice and venturi meters both function by sending pipe flow through a constricted area (the orifice plate or the venturi throat), as shown in the diagrams at the right.  Due to the increased fluid velocity passing through the constriction, there will be a decreased pressure at that location.   The pipe flow rate can then be calculated from the measured pressure difference between the undisturbed pipe flow and the flow through the constriction.

The general equation for calculating fOrifice and Venturi Flow Meter Calculations Spreadsheet Equationlow rate through either an orifice or venturi meter is shown at the left, where the parameters in the equation and their units are as follows:

 

  • Q is the flow rate through the pipe and through the meter  (cfs – U.S. or m3/s – S.I.)
  • Cd is the discharge coefficient, which is dimensionless
  • Ao is the constricted area perpendicular to flow  (ft2 – U.S. or m2 – S.I.)
  • P1 is the undisturbed upstream pressure in the pipe  (lb/ft2 – U.S. or N/m2 – S.I.)
  • P2 is the pressure in the pipe at the constricted area, Ao (lb/ft2 – U.S. or N/m2 – S.I.)
  • β = D2/D1 = (diam. at A2/pipe diam.), which is dimensionless
  • ρ is the fluid density (slugs/ft3 – U.S. or kg/m3 – S.I.)

Orifice and Venturi Flow Meter Calculations Spreadsheet Screenshot

The image below shows an Excel spreadsheet that can be used as a pipe flow rate calculator, based on the measured pressure difference across a flow nozzle, venturi, or Orifice flow meter.  This spreadsheet is suitable when the fluid density is known (as for a liquid) and the meter coefficient, C, is known.  For this spreadsheet and another to calculate the density of a gas using the ideal gas law model, click here to visit our spreadsheet store.

Orifice and Venturi Flow Meter Calculations Spreadsheet ScreenshotReferences

1. Munson, B. R., Young, D. F., & Okiishi, T. H., Fundamentals of Fluid Mechanics, 4th Ed., New York: John Wiley and Sons, Inc, 2002.

2. U.S. Dept. of the Interior, Bureau of Reclamation, 2001 revised, 1997 third edition, Water Measurement Manual, available for on-line use or download at: http://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/index.htm

3. International Organization of Standards – ISO 5167-1:2003 Measurement of fluid flow by means of pressure differential devices, Part 1: Orifice plates, nozzles, and Venturi tubes inserted in circular cross-section conduits running full. Reference number: ISO 5167-1:2003.

4. Bengtson, Harlan H., “Orifice and Venturi Flow Meters: for Liquid Flow and Gas Flow.” an Amazon Kindle e-book.