Estimating Pressure Loss in Closed Tank: Hole Size vs. Time

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Discussion Overview

The discussion centers around estimating the relationship between hole size and pressure loss over time in a closed tank scenario. Participants explore theoretical approaches to model this relationship, considering factors like gas behavior and efficiency in a pressurized environment.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant presents a scenario involving a 300 L closed tank pressurized to 20 psig, experiencing a pressure loss of 1 psi over one hour, and seeks to relate hole size to this pressure loss.
  • Another participant suggests using the conservation of mass, the equation of state, and an energy balance, referencing the Bernoulli equation as a framework for analysis.
  • A subsequent reply proposes that any calculated values should be doubled due to anticipated nozzle efficiency being around 50%.
  • Another participant notes that the gas exiting through a sufficiently large hole would likely reach sonic speeds, given the significant back pressure involved.

Areas of Agreement / Disagreement

Participants present multiple approaches and considerations, indicating that there is no consensus on a single method or outcome for relating hole size to pressure loss.

Contextual Notes

Assumptions about ideal gas behavior and nozzle efficiency are mentioned, but the discussion does not resolve the implications of these assumptions on the calculations or outcomes.

sarathane
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I am trying to figure out how to equate hole size to pressure loss/time for a closed tank. Here's the scenario:

300 L closed tank
Pressurized to 20 psig with air
Pressure loss is 1 psi over a time period of 1 hour
Temperature is 30 deg. C

How can I relate hole size to this pressure loss? Can assume ideal gas...just need a rough estimate/ball park answer.
 
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Use the conservation of mass (ie, continuity equation), the equation of state and an energy balance (ie, bernoulli equation)
 
Right - and whatever you get from that, double it, since the nozzle efficiency is probably only 50%.
 
Not to mention it will be sonic coming out of any hole that will allow a back pressure that large.
 

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