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  • Submitted: Jun 07 2011 12:25 PM
  • Last Updated: Jun 07 2011 12:25 PM
  • File Size: 178KB
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Download Valve Cv Sizing for Liquids and Gases

* * * * * 4 Votes

Estimate your valve Cv values with this workbook. There are six sheets included:

Liquid calculation by mass flow
Liquid calculation by volume flow
Gas calculation by mass flow (sub-critical)
Gas calculation by volume flow (sub-critical)
Gas calculation by mass flow (critical)
Gas calculation by volume flow (critical)

Reference material is not available for these calculations. Let us know how they compare to other methods in the comments section.

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The sheet is ok but the max/norm/min flows are mixed up in the example of the first sheet...
Jun 19 2011 07:11 AM
I will exam the sheet...
For liquids critical flow will be a function of vapour pressure and not pressure ratio.

Choked flow is a condition that occurs in a valve when the static pressure of the liquid drops below the vapor pressure, causing the liquid to flash to a vapor. The vapor bubbles occupy more volume than the same mass of liquid, resulting in restriction of the flow through the valve. When fully choked flow occurs, fluid flow through the valve will not increase when the downstream pressure is decreased. Choked flow results in high noise levels, vibration, pipe stress, and severe erosion and pitting of the valve seat and disc.

The methodology will be -
1. Calculate CV based on flow, pressure drop, spgr and piping geom factor.
2. Now with the CV selected calculate max flow possible which is a function of CV, pressure recovery factor, inlet pressure , vapour pressure,spgr, critical pressure.
Max flow possible is the choke flow. For further detail refer - http://www.mediafire.com/?dl62f22187uajre

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