3.8.4 Flow measurement
Little information is available on suitable flow measurement devices. It has
already been shown that pressure drop across a straight length of pipe is
relatively insensitive to flow rate in laminar region of highly shear-thinning
materials and therefore it is an unsuitable parameter for flow measurement.
In principle, the devices which depend upon the conversion of pressure into
kinetic energy (e.g. orifice and venturi meters, rotameters) can be used but
they need calibration for each fluid. The problem is compounded in practice
because the fluid may not have a constant rheology and/or may display
visco-elastic or time-dependent behaviour. Though many investigators have
studied the flow of polymer solutions through orifices, most of this work
has not been directed towards flow measurement but has related either to
the measurement of extensional viscosity or to extrusion behaviour. Both
Harris and Magnall [1972] and Edwards et al. [1985] have examined the
suitability of orifice and venturi meters for measuring the flow rates of
inelastic polymer solutions and kaolin suspensions. While Edwards et al.
[1985] were unable to bring together data for different aspect ratios, Harris and
Magnall [1972] reported satisfactory correlation for the discharge coefficient
in the turbulent regime. Despite all these difficulties, the measurement of
the flow of shear-thinning oil-water emulsions using orifice and venturi
meters has been the subject of a recent study [Pal, 1993]. The discharge
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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