Viscometry viscometer, design

Equation (4.4) is an unwitting statement that the velocity (l/t) of a sol s planar flow is inversely proportional to t. A capillary viscometer is designed to maintain r, l, V, and t (1 atm) constant, so that ti, is direcdy proportional to tt. The generalized equation for a single measurement (single-point viscometry) is... 

Measurements taken from a series of different ct arrived at in situ by dilution in specially designed viscometers comprise the capillary viscometry technique known as dilution viscometry. Neither single-point nor dilution viscometry is suitable for suspensions, because of the unreliability of their , resulting from heterogeneities of particle size, shape, and interaction. Variations in t- are conducive to slippage, wall effects, and turbulence. 

The single-capillary viscometer (SCV) is represented in Fig. la. Its design is a direct extrapolation of classical viscometry measurement. It is composed of a small capillary, through which the solvent flows at a constant flow rate, and a differential pressure transducer (DPT), which measures the pressure drop across the capillary. SCV obeys PoiseuiUe s law and the pressure drop AP across the capillary depends on the geometry of the capillary, on flow rate Q, and on viscosity of the fluid 7j according to... 

Viscometry Detection Although single and dual capillary viscometers are stiU in use, most commercially available detectors offered today are based on the four capillary bridge design originally developed by Haney [17]. 

Not only is temperature rise an important consideration in viscometry, where great care must be taken in the design of viscometers to permit adequate temperature regulation, but it... 

Not only is this an important consideration in viscometry, where great care must be taken in the design of viscometers to permit adequate temperature regulation, but it also must be taken into account in the design of processing systems. In the steady-state operation of extruders, for example, virtually all the energy required to melt and maintain the polymer in the molten state is supplied by the mechanical drive. Here, however, we will limit our considerations to isothermal flows. 

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