Laminar flow meter

See you tomorrow, I’ll be watching; I’m worried it’s just a gimmick

Structure and Calculation Model of Laminar Flow Meters Published on: 2017-08-23 14:34 Views: The design of flow meters is based on physical principles; for example, vortex flow meters are developed using Karman vortex theory. Although such principles exist, they are continuously refined through practical application until standards are established that are widely accepted. Structure and Calculation Model of Laminar Flow Meters http://www.abg.cc/uploads/allimg/170823/1_170823143450_1.jpg A laminar flow sensor generally consists of three components: a laminar flow generator, a flow straightener, and a pressure sensing device. The core component of a laminar flow meter is the laminar flow generator. The structural design of these laminar flow generators in laminar flow meters used both domestically and internationally is generally similar; they are typically made by stacking corrugated steel plates and flat steel plates with a certain width and a thickness of no more than 0.2 mm, and then winding them together. Such a design is equivalent to many thin-walled tubes arranged side by side, which force gas molecules to pass through parallel channels within a certain flow rate range, thereby creating laminar flow. Laminar flow meters are based on the accurate measurement of volumetric flow. The volumetric flow rate is determined by the static pressure difference generated before and after the laminar flow generator in the flow meter; by measuring this static pressure difference, the volumetric flow rate can be calculated. In laminar flow meters, the relationship between the volumetric flow rate QV and the static pressure difference (P1 – P2) before and after the laminar flow region can be expressed by Poiseuille’s equation: http://www.abg.cc/uploads/allimg/170823/1_170823143514_1.jpg http://www.abg.cc/uploads/allimg/170823/1_170823143514_2.jpg In laminar flow meters, there is a linear relationship between the volumetric flow rate and the static pressure difference. As can be seen from equation (2), the volumetric flow rate depends only on the static pressure difference at both ends of the laminar flow region, the flow coefficient K, and the viscosity of the medium being measured. K is the flow coefficient that is related only to the geometric dimensions of the laminar flow regime, and it is the most important parameter for laminar flow meters. Since r and L are difficult to measure, and the selection of the flow coefficient is directly related to the actual measurement accuracy of the corrected flow rate, the flow coefficient K is generally determined through experimental calibration. Another important parameter for the accurate measurement of volumetric flow rate is the dynamic viscosity coefficient of the medium being measured. Because the dynamic viscosity coefficient of the gas at the measurement temperature is also directly related to the actual measurement accuracy of the corrected flow rate. When the composition of the gas mixture changes, its viscosity coefficient also changes, which leads to a certain deviation in the flow measurement output signal.

Thank you all for your responses. Since the viscosities of gases vary greatly, how do laminar flow meters ensure that the gas flows in a laminar manner? I have another question!