Experimental and numerical assessments of the variable orifice flow meters (VOFM)

Measurements of gas flow are crucial in medical applications like respiratory monitoring and mechanical ventilators. Variable area orifice Flow meters (VOFMs) are increasingly recognized for respiratory monitoring, functional assessment, and mechanical ventilation. Area variation of such a flowmeter can be achieved by setting a moving body inserted concentrically and guided through a central rod in the flowmeter, the mechanism that may affect the input-output relationship and produce bias error. Notwithstanding these problems, the VOFM has been advocated to utilize the feature of the membrane’s flexibility as a variable area orifice. Two flowmeter prototypes with flexible membranes the “Medical Flow Sensor FS2 by Hamilton” and the “Datex-Ohmeda Flow Sensor” are tested in this study. The former has a triangular orifice shape, while the latter is circular. A flow test rig is built enabling instantaneous measurements and recording of different air flow rates and differential pressure using a high-sensitivity differential pressure sensor. The experimental results are compared with the outcomes of the solved CFD model, which is solved using the FVM method. Results indicate that for a specified differential pressure (ΔP), the circular orifice sensor “Datex-Ohmeda Flow Sensor” consistently demonstrates a superior mass flow meter relative to the triangular sensor “Medical Flow Sensor FS2 by Hamilton.”