Method and apparatus for measuring gas flow

A method of measuring the gas flow of a fluid flowing along a duct, the method comprising the following steps:

• a) measuring the temperature Tm and the pressure Pm of said gas under its flow conditions by means of temperature and pressure sensors disposed in the duct;
• b) determining the flow rate Qm of said gas under its flow conditions by means of a flow measuring device;
• wherein the method further comprising the following steps:
• c1 ) causing said gas to flow through a capacitive transducer which has been placed in the same thermodynamic conditions as apply to the flow gas;
• c2) measuring the capacitance of the capacitive transducer through which the gas passes, the capacitance in vacuo of said component having previously been established by measurements performed in vacuo, to determine the dielectric constant .epsilon. of the gas under its flow conditions;
• d) calculating the compressibility factor by means of a processing and control unit on the basis of the determined dielectric constant .epsilon. of the gas and the measured temperature and pressure Tm, Pm, using the following equation:
• ##EQU12## with:
• ##EQU13## R being the perfect gas constant A.sub..epsilon. and B.sub..epsilon. being coefficients depending in determined manner on the composition of the gas;
• and
• e) calculating the gas flow rate Q along the duct as reduced to predetermined reference conditions of temperature To, pressure Po, and compressibility factor Zo in the processing and control unit, using the following equation:
• Q=Qm(Pm/Po)(To/Tm)(Zo/Zm).

A method of measuring the gas flow of a fluid flowing along a duct, the method comprising the following steps:

• a) measuring the temperature Tm and the pressure Pm of said gas under its flow conditions by means of temperature and pressure sensors disposed in the duct;
• b) determining the flow rate Qm of said gas under its flow conditions by means of a flow measuring device;
• wherein the method further comprises the following steps:
• c1 ) causing said gas to flow through a capacitive transducer which has, been placed in the same thermodynamic conditions as apply to the flow of gas;
• c2) measuring the capacitance of the capacitive transducer through which the gas passes, the capacitance in vacuo of said component having previously been established by measurements performed in vacuo, to determine the dielectric constant .epsilon. of the gas under its flow conditions;
• d) calculating the compressibility factor by means of a processing and control unit on the basis of the determined dielectric constant .epsilon. of the gas and of the measured temperature and pressure Tm, Pm, using the following equation:
• ##EQU14## R being the perfect gas constant and A.epsilon. being a coefficient depending in determining manner on the composition of the gas;
• and
• e) calculating the gas flow rate Q along the duct as reduced to predetermined reference conditions of temperature To, pressure Po, and compressibility factor Zo in the processing and control unit, using the following equation:
• Q=Qm(Pm/Po)(To/Tm)(Zo/Zm).