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Viscometers Viscometers Presentation Transcript

  • A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Viscometers only measure under one flow condition. TYPES OF VISCOMETERS:- There are different types of Viscometers given below. Rotational Viscometer rotational viscometer gathers data on a material’s viscosity behavior under different conditions.The rotational viscometer basically consists of two parts - a head unit with a motor and a spindle that is driven by the motor. The viscosity is determined by measuring the resistance of a spindle rotating in the sample.
  • Rotational viscometers can be used for the accurate measurement of viscosity for both Newtonian and non-Newtonian fluids. Newtonian fluids are those that are affected by temperature, such as water, kerosene,mineral oils etc. NonNewtonian fluids are those that change viscosity when stirred, shaken or otherwise agitated. These include paint, gels, inks, milk,ketchup etc. Why use a rotational viscometer? Rotational viscometers are ideal for determining viscosity of liquids which do not depend solely on temperature and pressure.The behaviour of non-Newtonian liquids can also be tested and analysed.
  • Viscosity is a measure of the resistance of fluids to flow. A vibrational viscometer is used for continuous direct measurement of viscosity in pipes and/or tanks. The instrument works by creating a special kind of wave in the fluid.There are many kinds of vibrational waves but viscosity can only be accessed under shear conditions so we use shear waves. To the naked eye nothing moves but when the element is submerged in the liquid and moves back and forth microscopically at high frequency the surface of the sensor shears through the liquid & energy if lost. The viscosity of the liquid is derived by the measurement og this lost energy by the instrument .Vibratory Visco.m are better suited to measure non-newtonian liquids
  •         Electromagnetic viscometer or EMV viscometer. A viscometer for bedside blood measurements was developed, consisting of an oscillating resonator The oscillating piston viscometer technology has been adapted for small sample viscosity and micro-sample viscosity testing in laboratory applications. Measurements are taken when a sample is first introduced into the measurement chamber where the piston resides. Electronics drive the piston into oscillatory motion within the measurement chamber with a controlled magnetic field. A shear stress is imposed on the liquid due to the piston travel & the viscosity is determined by measuring the travel time of the piston. The travel distance of the piston are used to calculate the viscosity according to Newton’s Law of Viscosity. It has been adapted to measure high pressure & high temperature viscosity measurements in both laboratory and process environments
  • Falling Piston Viscometers The principle of viscosity measurement in this rugged and sensitive industrial device is based on a piston and cylinder assembly. The piston is periodically raised by an air lifting mechanism, drawing the material being measured down through the clearance (gap) between the piston and the wall of the cylinder into the space which is formed below the piston as it is raised. The time of fall is a measure of viscosity, with the clearance between the piston and inside of the cylinder forming the measuring orifice. The viscosity controller measures the time of fall (time-of-fall seconds being the measure of viscosity) and displays the resulting viscosity value. Falling Piston viscometers operate on similar principles as the falling sphere viscometers, except that they measure resistance to a piston moving through a fluid. These devices are very longlasting and simple to operate, and require little maintenance.
  •  Falling-piston or falling-ball viscometer. 1 = ferromagnetic ball, 2 = electrical magnet, 3 = magnetic switch, 4 = liquid, 5 = container
  • falling sphere viscometer A viscometer is an instrument used to measure the viscosity of a fluid. The falling ball viscometer is based on Stokes’ Law. This type of viscometer consists of a circular cylinder filled by the liquid under investigation. A standard ball is allowed to fall down this tube over a calibrated distance of 100 mm. The falling time is recorded and then utilized to determine the viscosity at a preset temperature. This device has the capability of providing a more accurate, low time-consuming and a more user-friendly means of measuring viscosity in a laboratory environment. This device with a few modifications can be used as an alternative setup to the present falling sphere viscometer setup used in the undergraduate laboratory experiment for the measurement of viscosity, as it provides the necessary accuracy and precision required for this experiment.