# Compressible methane flows

1. Apr 25, 2007

### cantabile

What are the governing equations for compressible fluid flow?
Specifically; methane gas inlet pressure of 25 psi through a 3/8" dia. pipe and I need to relate this to a methane flow of 392,000 BTU/ hr @ 55-60psi 59 F and RH 60% (i.e. ISO 2314) through an as yet undetermined diameter pipe, assume methane has 1,000 BTU/cu. ft. @ ISO 2314. I'm not sure if there's sufficient gas @ 25 psi through the 3/8" tube to meet the demand. Thanks for your insights!

2. Apr 25, 2007

### quark

First get the mass flowrate of methane. If you know the calorific value in btu/lb (better NCV or LHV), then total heat flowrate/LHV gives you mass flowrate of methane in lb/hr. That is the mass flowrate you require at any pressure. For piping calculation, if you can get an equation that directly deals with mass flowrates, nothing is better. Otherwise, get the density of methane at 25psi (a?g?) and the corresponding temperature and calculate the volumetric flowrate. Use the emperical equations given in Crane TP410 or in your local codes, if any.