Scroll down for the following blog articles in this category:

• Orifice Gas Flow Calculations Excel Spreadsheet
• Air Density at Temperature and Pressure Calculator

Where to Find Orifice Gas Flow Calculation Excel Spreadsheets

If you are looking for orifice gas flow calculation excel spreadsheets, Click Here to visit our download page.  Why use online calculators or try to use the incredibly ong ISo 5167 equations for hand calculatons when you can buy a spreadsheet for gas flow, liquid flow, large bore or small bore, ISO 5167 orifice plate flow meter calculations at a very reasonable price.   Read on for information and discussion of the use of orifice gas flow calculation excel spreadsheets.

Background for Orifice Gas Flow Calculation Excel Spreadsheets

Background for Orifice Gas Flow Calculation Excel Spreadsheets

For background on orifice meters and the orifice coefficient, see the blog articles, "Excel Spreadsheets for Orifice and Venturi Flow Meter Calculations" and Calculate an Orifice Coefficient with ISO 5167."  The diagram at the left shows the general orifice meter configuration and some of the parameters used orifice gas flow calculation excel spreadsheets.  Equations from ISO 5167-2:2003 are presented in the next section.

Equations for ISO 5167 Orifice Gas Flow Calculation Excel Spreadsheets

Equations for ISO 5167 Orifice Gas Flow Calculation Excel Spreadsheets

The equations for pipes with diameter between 2 in and 40 in (50 mm to 1000 mm) are given in Reference #1 at the end of this article, ISO 5167-2:2003.  The equations are summarized here.  The commonly used equation for compressible fluid (gas) flow rate is shown at the right, where the parameters are defined as follows:

• Q is the flow rate through the pipe and orifice meter in cfs (m³/s for S.I. units)
• C_o is the orifice discharge coefficient, which is dimensionless
• A_o is the orifice  area in ft² (m² for S.I. units)
• P₁ is the upstream absolute pressure in the pipe in lb/ft² (kN/m² for S.I. units)
• P₂ is the pressure at the downstream pressure tap in lb/ft² (kN/m² for S.I. units)
• β is the D_o/D₁ = orifice diam./pipe diam., which is dimensionless
• Z is the compressibility factor of the gas at P₁, T₁
• R is the Ideal Gas Law Constant = 345.23 psia-ft³/slugmole-^oR    ( or 8.3145 kN-m/kgmole-^oK for S.I. units)
• MW is the molecular weight of the gas
• T₁ = upstream absolute temperature in the pipe, ^oR (^oK for S.I. units)    
• Y = Expansion factor  (see the equation for Y below)

Y  =  1  -  (0.351  +  0.265 β⁴ +  0.93 β⁸)[ 1 - (P₂/P₁)^1/k ]

where:  k is the Specific Heat Ratio (C_p/C_v) of the flowing gas

The orifice coefficient, C_o, can be calculated from the following equations:

Where Re is the Reynolds number in the pipe ( Re  =  DVρ/μ ).

Orifice Gas Flow Calculation Excel Spreadsheets

Orifice Gas Flow Calculation Excel Spreadsheets

The screenshot below shows an example of orifice gas flow calculation excel spreadsheets.  This spreadsheet can be used to calculate gas flow rate, required orifice diameter, or pressure difference across the orifice, if the other two parameters are known.  The orifice gas flow calculation excel spreadsheet shown if for large bore (2 in. to 40 in. diameter) and uses U.S. units.  The image shows just the worksheet to calculate gas flow rate.  Why bother to make these calculations by hand?  This Excel spreadsheet and other similar ISO 5167 orifice gas flow calculation excel spreadsheets are available in either U.S. or S.I. units at a very reasonable cost in our spreadsheet store.  There are also spreadsheets for large bore orifice meter calculations for liquid flow and for small bore orifice meter calculations (gas flow or liquid flow).  The small bore spreadsheets are for pipes with diameters between 12 inch and 1 1/2 inches (12 mm to 40 mm), and use slightly different equations from ASME MFC-14M:2001.

References:

1. U.S. Dept. of the Interior, Bureau of Reclamation, 2001 revised, 1997 third edition, Water Measurement Manual.

2. International Organization of Standards - Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full. Reference number: ISO 5167-2:2003.

3. Bengtson, Harlan H., Flow Measurement in Pipes and Ducts, An online continuing education course.

4. Bengtson, Harlan H., "Spreadsheets for ISO 5167 Orifice Plate Flow Meter Calculations," an online blog article.

5. Bengtson, Harlan H., "Orifice or Venturi Pipe Flow Meters: for Liquid Flow or Gas Flow," an Amazon Kindle ebook.

Air Density at Temperature and Pressure Calculator Spreadsheet

Where to Find an Air Density at Temperature and Pressure Calculator Spreadsheet

For a low cost Air Density at Temperature and Pressure calculator spreadsheet,  click here to go to the download page.  Why use an online calculator or look in tables, when you can get 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.

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.

Ideal Gas Law Background for an Air Density at Temperature and Pressure Calculator 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 byn 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 in an air density at temperature and pressure calculator spreadsheet.

An Air Density at Temperature and Pressure Calculator Spreadsheet

The Excel spreadsheet template shown in the screenshot at the right will calculate the density of a gas for specified molecular weight, pressure and temperature.   This Excelspreadsheet is available in either U.S. or S.I. units as a low cost spreadsheet from our download page.  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.  Theideal 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 an Air Density at Temperature and Pressure Calculator Spreadsheet

 

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, 4^th 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.