绝热搅拌槽内流体平均剪切速率的一种计算方法

基于流体流动的剪切速率与能量耗散率、以及能量散率与流体温升速率的关系,提出了根据搅拌过程中流体温升速率计算绝热搅拌槽内流体平均剪切速率的方法,并会对一个实验室用的小型高速搅拌系统,建立了流体平均剪切速率与流体黏度及搅拌转速关系的经验模型。本方法确定的是全槽流体的平均剪切速率,其应用不受叶轮类型的限制,可用于湍流搅拌,弥补了Metzner-Otto方法的若干不足。对于控温搅拌槽,可先在绝热条件下确定平均剪切速率与搅拌转速、流体流变性参数及体积的关系。

AN APPROACH TO ESTIMATING THE AVERAGE SHEAR RATE IN AN ADIABATIC STIRRED VESSEL

Based on relationship between the shear rate and the energy dissipation rate, and relationship between the energy dissipation rate and the fluid temperature elevation rate, an approach is presented to estimating the average shear rate in an adiabatic stirred vessel according to fluid temperature elevation rate during stirring. As an example, an empirical correlation between the average shear rate and the viscosity and the stirring speed has been developed for a small high-speed stirring system. The average shear rate obtained by the presented approach is based on the fluid in the whole vessel, and application of this approach is not limited by type of the impeller, and it may also be used to stirring systems in the turbulent flow regime, thus making up some deficiencies of the Metzner-Otto approach. For the temperature-controlled vessels, one may in advance determine the correlation between the average shear rate and stirring speed, rheological parameters and volume of the fluid under adiabatic condition.