3.2.3Average kinetic energy of fluid
,In order to obtain the kinetic energy correction factor
for insertion in the mechanical energy balance, it is necessary to evaluate the ,
average kinetic energy per unit mass in terms of the average velocity of flow. The
calcula-tion procedure is exactly similar to that used for Newtonian fluids, (e.g. see
.([[Coulson and Richardson, 1999
3.2.4 Generalised approach for laminar flow of time-independentfluids
Approach used in section 3.2 for power-law and Bingham plastic model fluids
can be extended to other fluid models. Even if the relationship between shear
stress and shear rate is not known exactly, it is possible to use the following
approach to the problem. It depends upon the fact that the shear stress distribution
over the pipe cross-section is not a function of the fluid rheology and
is given simply by equation (3.2), which can be re-written in terms of the wall
shear stress, i.e.
Example 3.3
The shear-dependent viscosity of a commercial grade of polypropylene at 403K can
satisfactorily be described using the three constant Ellis fluid model (equation 1.15),
with the values of the constants: 0 D 1:25 104 Pas, 1=2 D 6900 Pa and D 2:80.
Estimate the pressure drop required to maintain a volumetric flow rate of 4 cm3/s
through a 50mm diameter and 20m long pipe. Assume the flow to be laminar.
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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