Laminar heat transfer to Newtonian and non-Newtonian fluids in tubes

A theoretical treatment is presented which allows radial temperature and velocity profiles and the axial pressure profile to be predicted whenThe theoretical predictions have been confirmed by comparing them with experimental temperature and velocity profiles obtained for a Newtonian oil andThe experimental Nusselt numbers were also compared with the theoretical predictions and with those calculated from the generally accepted design correEmpirical methods for predicting the overall pressure drop can also give rise to large errors.     

非牛顿流体中气泡群传质的研究

CO2气泡群在液相中的传质在化工过程中广泛存在.对CO2气泡群在3种不同流体(牛顿流体、非弹性剪切变稀流体和黏弹性剪切变稀流体)中的气液传质过程进行了研究.利用CO2探针测定了不同操作条件下CO2的体积传质系数,考察了液相浓度,气体流量以及流变性质对体积传质系数的影响.结果表明:在3种流体中,体积传质系数均随气体流量的...     

Mass transfer from cylinders rotating in Newtonian fluids and dilute polymer solutions

A new theoretical expression for tubulent mass transfer from a rotating cylinder has been proposed using Levich's three-zone model. The predictions of this model, which has no adjustable parameters, were compared with available experimental data and with other correlations for Newtonian fluids and the agreement was found very satisfactory. Equally good agreement was found between the predictions of our model and the available data for mass transfer from a rotating cylinder under the conditions of maximum drag reduction.     

Momentum transfer to Newtonian and non-Newtonian fluids flowing through packed and fluidized beds

This paper deals with the flow behaviour of Newtonian and non-Newtonian fluids flowing through packed and expanded beds. With the help of tube-bundle theory a generalized average shear-stress—shear-rate relationship is derived and found to predict the flow behaviour of power law as well as non-power law fluids. Polyvinyl alcohol solutions in water, a representative of power law fluids, and grease in kerosene, a representative of nonpower law fluids, are studied. The present investigation covers the range of Reynolds number from 10^?3 to 10³. An expression for average shear-stress at minimum fluidization velocity is derived and found to agree with that of our experiment. The generalized frictional Reynolds number is defined and a design chart is also presented for the evaluation of fluidizing velocities.     

牛顿及非牛顿流体中的气泡生成与对比

采用激光成像结合CCD摄像技术分别对牛顿及非牛顿流体(甘油和羧甲基纤维素钠水溶液)中的气泡生成行为进行了研究,对2种流体气泡生成过程中气泡形状和体积变化进行了比较。分析了非牛顿流体的弹性效应对气泡生成过程气泡形状的影响。实验结果表明,在实验条件范围内,甘油中,气泡生长初期,气泡体积增加较快,到了后期,增加幅度减缓,气速对气泡生长过程气泡体积影响很小;羧甲基纤维素钠(CMC)水溶液中,气泡生长初期,气泡缓慢生长,气速对气泡体积影响很小,到了后期,气泡体积增加幅度变大,气泡体积随着气速的增大而增大。     

Liquid phase mixing in bubble columns with Newtonian and non-Newtonian fluids

A hydrodynamic model for the liquid phase in bubble columns is developed. The proposed model for fully developed turbulent Newtonian and non-Newtonian fluids is based on an energy balance and the mixing length theory. The predictions of the model are in reasonably good agreement with data on liquid velocity at the column axis and the axial dispersion coefficient. The liquid velocity data in an inverted conical bottom gas—liquid column contactor have also been measured. They are correlated by the proposed model reasonably well.     

Mass transfer from single bubbles in Newtonian liquids

The constant volume technique developed by Calderbank has been used for measuring the instantaneous mass transfer rates for single carbon dioxide bubbles with 0·46<d₀<0·85 cm in n-propanol, i-butanol, acetic acid, distilled water and n-octanol aqueous solution.The decay of mass transfer coefficient with bubble age was observed even in clean pure liquids, and the degree of the decay was high for the system of small bubble and the liquid where the solubility and the diffusivity of carbon dioxide were large. An empirical equation for mass transfer coefficient has been proposed taking the effect of bubble age into account.     

气-液-固三相气升式环流反应器中牛顿型及非牛顿型流体局部液相传质模型

A small scale isotropic mass transfer model was developed for the local liquid side mass transfer coefficients in gas-liquid-solid three-phase flow airlift loop reactor for Newtonian and non-Newtonian fluids.It is based on Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence with k1 = 3√2Dε1/3 1/π(η-1/3 1 -λ-1/3 f),where ε1 is local rate of energy dissipation,λf is the local microscale,η1 is the local Kolmogoroff scale and D is the diffusion coefficient.The capability of the proposed model is discussed in the light of experimental data obtained from 12 L gas-liquid-solid three-phase flow airlift loop reactor using Newtonian and non-Newtonian fluids.Good agreement with the experimental data was obtained over a wide range of conditions suggesting a general applicability of the proposed model.     

Forced convection heat transfer from axisymmetric bodies to non-Newtonian fluids

A theoretical analysis for forced convection heat transfer from axisymmetric bodies immersed in non-Newtonian power-law fluids has been performed. Results for the velocity shape factor, local friction coefficient, and the Nusselt number are presented for different values of Prandtl number and the power-law index. The local friction coefficient results are compared with available experimental data and it is shown that asymptotic expressions suffice to get accurate predictions of heat transfer at low and high Prandtl numbers.     

Heat transfer in laminar flow of non-Newtonian fluids

The main objective of this work is the consideration of local heat transfer coefficients for non-Newtonian power-law pseudoplastic liquid in laminar flow in circular conduits. The wall boundary conditions chosen are cases involving uniformly constant heat flux and step change in heat flux.Analytical solutions are developed for the wall temperature profile and compared with experimental data. Additionally, the experimental data have been correlated for comparison with existing relationships, hitherto not verified adequately. The limits of experimental data are:

     

Mass transfer between solid spheres and oscillating fluids — A critical review

Relative oscillatory motion between solid particles and a fluid increases the rate of interphase mass transfer due to the establishment of secondary flows (acoustic streaming). A critical survey of published data shows that mass transfer is well correlated by a theoretically founded dimensionless relation of the form where K, a, b and d depend on the Schmidt number. The equation successfully correlates experimental data for both gases and liquids over a range of frequencies F < 1 Hz to F ～ 10⁶ Hz, provided the amplitude to diameter ratio A/D is below 0.75. At higher values of this parameter, \documentclass{article}\pagestyle{empty}\begin{document}$ \bar N_{Sh} $\end{document} is better predicted by a quasi-steady model which no longer depends on A/D.     

Mass transfer between solid spheres and oscillating fluids — A critical review

Relative oscillatory motion between solid particles and a fluid increases the rate of interphase mass transfer due to the establishment of secondary flows (acoustic streaming). A critical survey of published data shows that mass transfer is well correlated by a theoretically founded dimensionless relation of the form where K, a, b and d depend on the Schmidt number. The equation successfully correlates experimental data for both gases and liquids over a range of frequencies F < 1 Hz to F ? 10⁶ Hz, provided the amplitude to diameter ratio A/D is below 0.75. At higher values of this parameter, N_Sh is better predicted by a quasi-steady model which no longer depends on A/D. Based on a paper presented at the 26th Canadian Chemical Engineering Conference, Montreal, Quebec, November 2–5, 1975.     

Power-draw analysis of a coaxial mixer with Newtonian and non-Newtonian fluids in the laminar regime

The power consumption of a new coaxial mixer composed of a wall scraping arm and a series of rods and a pitched-blade turbine mounted on the same axis of revolution and operated in a contra-rotating mode has been characterized. The work is based on experimental measurements and 3D numerical simulations in the case of homogeneous Newtonian and non-Newtonian fluids in the laminar regime. Very good agreements between experimental and numerical results have been obtained. It has been shown that the Metzner-Otto concept can be extended to account for the speed ratio between the impellers, which allows to represent the power consumption results of the coaxial mixer on a single power master curve like with a single agitator mixer.     

Mass transfer from rotating disk to non-newtonian fluids

Mass transfer to non-Newtonian fluids from a rotating disk is studied. A comparison between the two dimensional boundary layer flow over a flat plate a     

Heat transfer in bubble column and airlift bioreactors: Newtonian and non-Newtonian fermentation broths

A theoretical model has been developed for heat transfer in bubble column and airlift bioreactors, which is applicable for Newtonian and non-Newtonian fermentation media. The proposed model is based on a similarity between heat transfer in gas-sparged pneumatic reactors and turbulent natural convection. The applicability of the proposed model was discussed using a wide range of experimental data, and good agreement was obtained.     

Mass transfer from cylindrical pellets submerged in parallel flowing fluid streams

A model is proposed wherein overall mass transfer from single cylinders of benzoic acid placed in parallel flowing water streams depends on different hydrodynamic regimes prevailing along the surfaces of the cylinder. The results for laminar and turbulent conditions are correlated in terms of Sherwood and Reynolds numbers. The mass transfer in the wake region of the cylinder is observed to be significantly different from the boundary layer mass transfer through the lateral surface or the stagnation and boundary layer mass transfer through the leading frontal area.     

Mass transfer to newtonian and non-newtonian fluids from rotating cylinders

Mass transfer from rotating cylinders to Newtonian and non-Newtonian fluids is investigated. Present and previous data are analysed and correlations are presented. Free convection mass transfer correlations for vertical cylinders are found to differ from those for horizontal cylinders available in previous literature. Modified Prandtl analogy is applied, by considering the eddy penetration of the diffusion sublayer, to obtain the following expression for forced convection mass transferSh Sc^{?$\text{1}\text{3}$} = 0.62fRe which is found to correlate the present and previous data in the range of Sc, 2.6–32000, Pr, 0.72–676 and Re, 10²–10⁵ with a standard deviation of 14.6%. Differential viscosity is used to correlate mass transfer data to non-Newtonian fluids. Experimental results are seen to be lower than those predicted by the Newtonian correlation.