Miscellaneous Solved Sample Problems Thermodynamics

MMSCFD conversion calculation

Million Standard Cubic Feet per Day (MMSCFD)

MMSCFD is a unit for gas flow rates expressed at standard temperature and pressure conditions. Volumetric flow of a gas depends strongly on the temperature and pressure conditions. Hence the standard temperature and pressure conditions provide a very convenient reference point with commonly known temperature and pressure value. Volumetric gas flow expressed at standard conditions can be readily converted to mass or molar flow of that gas which is independent of pressure or temperature values.

Following sample problem demonstrates how MMSCFD value can be calculated based on its volumetric flow and pressure, temperature values at which this flow rate is expressed.

Sample Problem for MMSCFD conversion

What is the MMSCFD (Million Standard Cubic Feet per Day) flowrate corresponding to 100m3/hr of nitrogen flowing through a pipe? Operating temperature of nitrogen stream is 800C. Operating pressure at the point of flow measurement is 25 bar.

Standard conditions defined by NIST to be used.

Solution

The calculation of MMSCFD, first requires the standard temperature and pressure conditions to be fixed. Standard temperature and pressure conditions defined by NIST are to be used, as specified in the problem statement.

Standard Temperature TS = 00C = 273.16 K
Standard Pressure PS = 101.325 kPa

The operating conditions are,
Volumetric gas flow V = 100m3/hr
Gas temperature T = 800C = 353.16 K
Gas pressure P = 25 bar = 2500 kPa

Gas volume is directly proportional to temperature and inversely proportional to pressure.

Gas flow at standard conditions is calculated as,
VStandard = V×(TS/T)×(P/ PS)
= 100×(273.16/353.16)×(2500/101.325) m3/hr
= 1908.4 SM3/hr
= 1908.4×(3.28)3/(1/24) ft3/day
= 1616226.3 ft3/day
Gas flow = 1616226.3/106 MMSCFD = 1.6162 MMSCFD

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