Find Orifice Diameter for Specific Operating Parameters

These Excel spreadsheets will help you find the orifice size for an orifice flow meter, given various design parameters like the desired pressure drop, fluid properties etc. All the spreadsheets use industry-standard designs, such as ISO 5167 and ASME MFC-14M-2001

First, decide what type of orifice you're designing and download the appropriate Excel Spreadsheet (read the articles for the equations and valid operating conditions)

I'll illustrate the calculation process with an example problem (but the principles are the same for the other spreadsheets). All the spreadsheets require Excel's Goal Seek functionality because the calculations are iterative.

We will now find the orifice diameter for a small-bore liquid flow meter under the following conditions
  • Pipe diameter: 0.042m
  • Density: 1000 kg m -3
  • Viscosity: 0.001 Pa s
  • Desired pressure drop: 30 Pa
  • Flange taps
Step 1: Define the parameters as specified above, and also include an initial guess value for the orifice diameter.

Step 2: Go to Data > What If Analysis > Goal Seek. Set the difference in the guess and calculated values of the Reynolds number to zero by varying the orifice diameter.

As soon as you click OK, Excel will give the correct orifice size, as well as other parameters, like the flowrate, orifice coefficients, Reynolds Numbers etc.


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