The pressure inside the flow channel drops compared to the pressure outside of it, and the degree to which the pressure changes depends on the mass flow rate of the fluid. Once the fluid exits it, the flow becomes turbulent again. When the fluid enters the flow channel, its turbulent motion becomes laminar inside this channel. It is marked with number 2 on the illustration. In other types of positive displacement flow meters pistons, rotors, or oscillating or nutating disks could be in place of the gears.Ī laminar flow meter has a filter inside, known as the flow channel, which resembles a grill. In the illustration, the flow in sections 1 and 3 of the pipe is turbulent, while the flow in the middle section 2 is laminar.Ī simplified diagram of a positive displacement flow meter with a gear mechanism shown in purple. It means that layers within the liquid move in parallel to other layers. Actually, laminar flow does not mean that every single particle moves in parallel to all the other particles. One is turbulent flow, where the particles in the liquid move chaotically, and the other is laminar flow, where particles move in parallel to each other. When a liquid flows through a restricted environment, for example, though a channel or a pipe, there are two possible ways it can flow. Two of the most common volumetric flow rate meters are laminar and positive displacement flow meters. The volumetric flow rate is calculated based on the difference in fluid pressure within the meter and outside of it, as we can see on the pressure gauges. The flow in the sections before and after the flow meter is turbulent, with particles in the fluid moving arbitrarily. In this section layers of fluid move in parallel to other layers.
On the other hand, other industries are less demanding and can afford to choose other features over the accuracy, such as low cost.Ī laminar flow meter induces laminar flow in a section of the pipe, for which the flow rate is measured. For example, aerospace engineering is one field that values accuracy. For example, some jobs call for high precision and low error rates, such as 1% or less. Other meters do not work well when the flow of fluid is intermittent.Īnother feature to consider is the accuracy of the flow meters. The viscosity of the fluids is also important - some meters work well only within a certain viscosity range. Ensuring that the sensor does not come in contact with the fluid is one of the ways to prolong the longevity of such flow meters.
Their components that are in direct contact with the fluid are made from materials that can withstand these environments and are shaped to minimize wear-out. Heavy-duty flow meters are meant to work with corrosive fluids and to withstand harsh environments, such as extreme temperatures and pressure. The environment, which the meters are intended for, is one of these considerations. Flow meters have different features, depending on their purpose.
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