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Sunday, September 28, 2008

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In earlier discussion on "Another descrepancy found in API Std 521Jan 2007", the question is related to inclusion of specific heat ratio (k). This post is the follow-up and below presented the detail discussion and derivation of Mach no and critical pressure.

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One of the important assumption taken by API is consider ISOTHERMAL flow for Mach number, Critical pressure and pressure drop calculation. This concept is important as it affect the inclusion or exclusion of k in the formula. API consideration of ISOTHERMAL flow is reasonable as the fluid discharge to flare or vent network, the network is rather large and long and it possibly has sufficient time for heat transfer from metal or ambient. ISOTHERMAL flow is best suit for long pipeline modeling.

Above has shown that the by considering isothermal flow, the k factor should be omitted from the Mach number and critical pressure calculation.

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posted by Webworm, 5:55 AM


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