Viscosity influencing factors

As mentioned above, the viscosity is an important physical parameter. Table 14.7 presents comparatively the values recommended by the standards for diesel fuels in the USA and Europe. It can be observed that they are in a small range, but the upper limit is somewhat higher for biodiesel with respect to petrodiesel. Actually, the fatty esters exhibit larger variation of viscosity due to their chemical nature compared with hydrocarbon molecules. Influencing factors are chain length, position, number, and nature of double bonds, as well as the nature of the... 

Other errors, which could influence the results obtained, are, for example, wall effects ( slipping ), the dissipation of heat, and the increase in temperature due to shear. In a tube, the viscosity of a flowing medium is less near the tube walls compared to the center. This is due to the occurrence of shear stress and wall friction and has to be minimized by the correct choice of the tube diameter. In most cases, an increase in tube diameter reduces the influence of wall slip on the flow rate measured, but for Newtonian materials of low viscosity, a large tube diameter could be the cause of turbulent flow. ° When investigating suspensions with tube viscometers, constrictions can lead to inhomogeneous particle distributions and blockage. Due to the influence of temperature on viscosity (see Section Influence Factors on the Viscosity ), heat dissipated must be removed instantaneously, and temperature increase due to shear must be prevented under all circumstances. This is mainly a constructional problem of rheometers. Technically, the problem is easier to control in tube rheometers than in rotating instruments, in particular, the concentric cylinder viscometers. ... 

Heller and Taber were the first to study and report data involving the use of a direct thickener for dense carbon dioxide. Their efforts focused on commercially available polymers that would be sufficiently soluble in CO2 to increase its viscosity a factor of 20. From their study, the authors found that none of the commercially available polymers were able to increase the viscosity of CO2 to the desired level. However, they were able to make certain generalizations on the influence of various polymer properties on their solubility in liquid or supercritical C02 ... 

An experiment was done keeping the ligand constant and varying the base metal. This was to evaluate whether the metal has an influencing factor on the overall cure rate. The catalysts used were cupric, manganic and ferric acetylacetonates. The concentration of catalyst varied from 1.50% to 8.00% by weight and were added alone and in combinations of two. The experiment consisted of viscosity measurements over time using a Brookfield Viscometer. 

Fig. 7.7 (a) Viscosity versus shear rate curve of polypropylene (melting index 8 g/10 min imder 2.16 Kg and 230 °C) at 230 °C, and the applieable methods in various regitms (Gahleitner 2001) (Reprinted with permission) (b) Illustration of polymta- melt viseosity changing with shear rates and various influence factors (see the text for the details)... 

Efficient separation of the precipitated calcium sulphate, which is crucial to a successful commercial process, depends on its crystallisation behaviour and the acid viscosity. These factors are influenced by the acid concentration, the temperature and the impurities in the phosphate rock which can themselves be precipitated. 

The presence of mixed surfactant adsorption seems to be a factor in obtaining films with very viscous surfaces [27], For example, in some cases, the addition of a small amount of nonionic surfactant to a solution of anionic surfactant can enhance foam stability due to the formation of a viscous surface layer possibly a liquid crystalline surface phase in equilibrium with a bulk isotropic solution phase [21, 126], To the extent that viscosity and surface viscosity influence emulsion and foam stability one would predict that stability would vary according to the effect of temperature on the viscosity. Thus, some petroleum industry processes exhibit serious foaming problems at low process temperatures, which disappear at higher temperatures [21],... 

Sub-problem 3 554 alternatives remained after screening the target properties of the blends obtained from sub-problem 2 using the linear mixing rules. Dynamic viscosity and lethal concentration are the influencing factors that determined the blend formulations. Nevertheless, the RON value cannot be predicted for all blends because the RON of the pure species is not available. So these compounds were also removed... 

Both constants used in the Arrhenius equation (Eq. 4.1) have to be more closely defined. In order to determine whether these two values are dependent on processing parameters, the above relationships are compared with measured data. The relationship found between reduction in viscosity and the various influencing factors has the following mathematical form [607] ... 

The main factors which affect the viscosity of emulsions are listed in Table 8.6. The properties of the disperse phase, the continuous phase and the emulsifying agent or agents all influence the emulsion viscosity. Each factor does not act independently and the interpretation of emulsion viscosity data is complicated by this fact and the fact that particles can deform under shear depending on the nature of the interfacial film. As we have also discussed, emulsions are complex systems, often highly structured, and at phase boundaries or on the point of inversion are very sensitive to small perturbations in the system. We will deal here first with mobile emulsions and then consider briefly the semi-solid state. 

To achieve the ultimate goal of the research, we have worked on the mechanistic model of the head-on collision which is used for prediction of the evolution of the diameter of the collision complex. Our development is based on the model of Roisman et al. [26] for high Reynolds and Weber numbers. We have extended it with consideration of significant viscosity influence. The lamella thickness and its temporal evolution are described separately such that an improvement is achieved. To apply the extended model, model parameters are obtained by simulation of the initial collision phase for which fine mesh resolution is not required. With this hybrid model, the predicted lamella thickness fits almost perfect in case of moderate Reynolds and Weber numbers. An attractive feature of the hybrid model is that the simulation time can be significantly reduced by a factor of 300 compared to the fully resolved simulation of the complete collision. 

Therefore, a cmiversion between different fluid systems is possible by changing the interface properties a cos 0 and densities. Also a conversion from laboratory measurements to reservoir conditions is possible. Table 2.10 gives some data for different fluid systems. A detailed study about the oil-brine interfacial tension and influencing factors (salinity, pH, viscosity) was published by Buckley and Fan (2007). 

The flowrate of oil into the wellbore is also influenced by the reservoir properties of permeability (k) and reservoir thickness (h), by the oil properties viscosity (p) and formation volume factor (BJ and by any change in the resistance to flow near the wellbore which is represented by the dimensionless term called skin (S). For semisteady state f/owbehaviour (when the effect of the producing well is seen at all boundaries of the reservoir) the radial inflow for oil into a vertical wellbore is represented by the equation ... 

Cure Characteristics. Methods of natural rubber production and raw material properties vary from factory to factory and area to area. Consequentiy, the cure characteristics of natural mbber can vary, even within a particular grade. Factors such as maturation, method and pH of coagulation, preservatives, dry mbber content and viscosity-stabilizing agents, eg, hydroxylamine-neutral sulfate, influence the cure characteristics of natural mbber. Therefore the consistency of cure for different grades of mbber is determined from compounds mixed to the ACSl formulation (27). The ACSl formulation is as follows natural mbber, 100 stearic acid, 0.5 zinc oxide, 6.0 sulfur, 3.5 and 2-mercaptobenzothiazole (MBT), 0.5. 

---