Kapillaariviscometrejä

Kapillaariviscometrejä, known in English as capillary viscometers, are instruments used to measure the dynamic viscosity of a fluid. They operate on the principle that the time it takes for a known volume of fluid to flow through a narrow tube of precise dimensions is directly proportional to its viscosity. This phenomenon is described by the Hagen-Poiseuille equation, which relates the flow rate, pressure drop, tube radius, tube length, and the fluid's viscosity.

There are several types of capillary viscometers, each with its own advantages and applications. The Ubbelohde viscometer is a popular type that uses a suspended level bulb to ensure consistent driving pressure and minimize errors due to variations in the volume of fluid. Ostwald viscometers are another common design, where the fluid flows under gravity between two marked points. Cannon-Fenske viscometers are also widely used, particularly for opaque liquids.

The process of measurement typically involves filling the viscometer with the fluid sample, allowing it to reach thermal equilibrium, and then measuring the time it takes for the fluid to flow between two calibrated marks. This flow time, along with the viscometer's calibration constant (determined using fluids of known viscosity), allows for the calculation of the fluid's dynamic viscosity. Capillary viscometers are valued for their simplicity, accuracy, and relatively low cost, making them suitable for both laboratory and industrial settings. They are employed in various fields, including petrochemicals, food processing, and pharmaceuticals, to control product quality and understand fluid behavior.