| abstract |
The oxygen concentration of a gas mixture primarily of oxygen, nitrogen, and argon is determined by measurement of the shell side flow through a hollow fiber permeable membrane module having a tube side and a shell side. A sample of the gas at a low pressure is applied via a gas regulator to the tube side. Compressed air for purge flow is supplied via a first flow controller to one end of the shell side. A small portion of the tube side flow permeates the membrane, enters the shell of the module and combines with the air purge flow. The measurement of the oxygen concentration is determined by the amount of flow exiting the shell side via a flowmeter to a vent. The amount of gas permeating the membrane is dependent on the partial pressure of oxygen on both sides of the membrane. Hence, as the tube side partial pressure increases, a greater quantity of permeated gas passes to the shell side of the membrane. The remaining tube side flow exits the module via a second floor controller to the vent. Signals from the flowmeter, a thermocouple, and a pressure sensor are applied to digital processing circuit each second. The digital processing circuit uses the shell side flow, temperature in degrees Kelvin and pressure converted to an equivalent altitude, and calculates the oxygen concentration in the sample gas by applying equations stored in the digital processing circuit. |