How to Calculate Air Flow Rate for a Cylindrical Vessel with Perimeter Holes?

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Discussion Overview

The discussion focuses on calculating the air flow rate for a cylindrical vessel with perimeter holes under a specific vacuum condition. It involves technical aspects related to fluid dynamics and mechanical engineering principles.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant describes the dimensions and specifications of a steel cylindrical drum designed for vacuum measurement and requests assistance in calculating the required air flow rate.
  • Another participant suggests that the thread may be better suited for the mechanical engineering forum and provides an estimated flow rate of 280 SCFM, assuming a discharge coefficient of 0.7 and steady-state conditions.
  • A different participant proposes using Bernoulli's equation to calculate the flow rate, indicating that the static pressure of 1" of water can be converted into velocity pressure under ideal conditions.
  • One participant expresses skepticism about the calibration standard being used for the vacuum measurement.

Areas of Agreement / Disagreement

There is no consensus on the calculation method or the validity of the calibration standard, with differing opinions on the appropriateness of the approach and the estimated flow rate.

Contextual Notes

Assumptions include the discharge coefficient and the ideal conditions for applying Bernoulli's equation. The discussion does not resolve the implications of these assumptions on the accuracy of the flow rate calculation.

naboulsi
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We are having trouble calculating a required ft^3 per minute air flow for a particular vessel which was constructed to measure the accuracy of a vacuum machine.
Our vessel is a steel cylindrical drum 1mm thick with a diameter of 22.5" and a height of 34.5". It has 50 holes around the lower perimeter measuring 13 mm in diameter. What is the air flow rate if we pull a vacuum of 1" of H20 at a temp of 70 deg. F and Relative Humidity of 26%. Can anyone help us out?
 
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Hi naboulsi,
This probably belongs in the mechanical engineering forum. Anyway, assuming your system is maintaining 1" water vacuum, steady state, and assuming a discharge coefficient for your drilled holes of roughly 0.7 (from experience) I'd estimate your flow rate to be 280 SCFM.
 
The way to calculate it is to use Bernoulli's equation: assuming perfect nozzles, that 1" of static pressure becomes your velocity pressure.
 
That is a pretty poor sounding calibration standard.
 

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