ABSTRACT
Laminar flowmeters fill a special need in flow measurement where the requirements might include low to extremely low flow rates, linear calibration and low noise, the ability to measure high-viscosity liquids, or steady low flow repeatability and control accuracy. Laminar flowmeters are intended for very low flow rates where other types of meters are either marginal in performance or cannot be used at all. Laminar flowmeters can be constructed by various methods, but the most common method is with capillary tubes. Where gas is metered, it is preferable to use calibrated commercial units instead of undertaking the design of a laminar flowmeter. The theory for laminar flowmeters is based upon the Hagen-Poiseuille Law for laminar flow and Reynolds number as a means of defining the type of flow. There are a number of guidelines for successful design of a laminar flowmeter. Changes in viscosity and density can result in flow measurement errors.
