Conversion dynamic viscosity

The dissipation function, also called viscous dissipation, represents the irreversible conversion of kinetic energy into thermal energy. Since the dynamic viscosity p, is positive and all the terms are squared, the first two terms of the dissipation must be always positive. The bulk viscosity can be negative the Stokes hypothesis (Section 2.11) says that k = —2p/3. It turns out that the necessary condition for the dissipation function to be positive is that... 

The evolution of the dynamic viscosity rp (co, x) or of the dynamic shear complex modulus G (co.x) as a function of conversion, x, can be followed by dynamic mechanical measurements using oscillatory shear deformation between two parallel plates at constant angular frequency, co = 2irf (f = frequency in Hz). In addition, the frequency sweep at certain time intervals during a slow reaction (x constant) allows determination of the frequency dependence of elastic quantities at the particular conversion. During such experiments, storage G (co), and loss G"(co) shear moduli and their ratio, the loss factor tan8(co), are obtained ... 

Experimentally, the glass transition has also manifested itself by a sharp increase in relative rigidity (measured by dynamic-mechanical methods) and a simultaneous drastic decrease in the rate constant of the autocatalytic epoxy-amine reaction The mobility or rigidity of the system is a function of reaction conversion a in the pre-gel region it can be characterized by dynamic viscosity which is proportional to M of the reacting system. Beyond the gel point, still in the rubbery region but not close to the gel point, the dynamic modulus, G, is at low frequencies proportional to " (m a 1)... 

The constant r in the equation is called the y/scosity coefficient or dynamic viscosity. Its unit in the Sf system is Pa s (for conversion of units, 1 poise = 0.1 Pa s = = 1 dPa s). The reciprocal value of dynamic viscosity is called fluidity (fluidity coefficient). In hydrodynamics, frequent use is made of a quantity expressing the dynamic viscosity divided by density of the liquid and called kinematic viscosity... 

Conversion factors for mass, density, pressure, energy, specific energy, specific heat, thermal conductivity, dynamic viscosity, and kinematic viscosity in different systems of units are also given in Chap. 2 (Tables 2.1-2.9). 

TABLE 2.8 Conversion Factors for Units of Dynamic Viscosity... 

Using a Rheometrics mechanical spectrometer and powdered polymer samples, the authors compared the rheological behaviour of two polymers with similar chemical compositions but different structures. The rheological profiles of polymers 21 and 22 were determined between 140 and 400°C by increasing the temperature at 10°C min from 140 to 190°C and from 300 to 400°C. In the predominant region of isoimide-imide conversion (190-300°C), the temperatme was raised by 2 or 5°C increments, the dynamic viscosity rj being measured at each temperature step. At 190°C, the viscosity of poly(isoimide) 21 was approximately 5 X 10 Pas and decreased to a minimum value of 10 Pas at 243°C as the polymer softened and melted. Thermal conversion to polyimide 22 concurrently... 

For degrees Kelvin the degree symbol is omitted for example, 50 K, not 50°K. 2. For multiplication a center point is used for example, the unit of dynamic viscosity is abbreviated as N S/m, not N s/m or N X s/nT. 3. Symbols for SI units are not capitalized unless the unit is derived from a proper name, as N for Sir Isaac Newton however, unabbreviated units are not capitalized, such as newton, kelvin, hertz. Conversion Factors to SI Standard Units To Convert To Multiply by To Convert To Multiply by ... 

Relative of conversion of a key component k Vector for relative conversion Asymptotic effectiveness factor in Section 5.2.2.4 Radial heat conductivity of catalyst bed Effective heat conductivity of catalyst particle Heat conductivity of fluid film Intensity function. Chapter 4 Dynamic viscosity... 

At the same time, in a number of cases a discrepancy is observed between the position of the maximum of G" and the point where viscosity goes to infinity, for example, during network-formation of silicone rubbers [22]. In this example, the difference between these two points reaches 7% in conversion which suggests that the gel point cannot be identified with the help of dynamical mechanical measurements [12]. 

Using an earlier version of the dynamic model given in Section IV,6, Kiparissides et al (1980b) illustrated the use of such an extended Kalman Filter to infer JV(f), VJit), AJit), and X(f) from measurements taken only on conversion [X(f)J using UV turbidity spectra. Jo and Bankoff (197Q used these filters to track some of the moments of the MWD of PVAc in a solution polymerization process using measurements made on refractive index and viscosity. 

The classification criteria refer to kinematic viscosity. The following provides the conversion between dynamic and kinematic viscosity ... 

During food engineering operations, many fluids deviate from laminar flow when subjected to high shear rates. The resulting turbulent flow gives rise to an apparent increase in viscosity as the shear rate increases in laminar flow, i.e., shear stress = viscosity x shear rate. In turbulent flow, it would appear that total shear stress = (laminar stress + turbulent stress) x shear rate. The most important part of turbulent stress is related to the eddies diffusivity of momentum. This can be recognized as the atomic-scale mechanism of energy conversion and its redistribution to the dynamics of mass transport processes, responsible for the spatial and temporal evolution of the food system. 

Pascal second (pascal-second, Pa-s) n. The SI unit of dynamic (absolute) viscosity, equal to INs/m. Some conversions of older viscosity units (of which there is a bewildering plethora) to Pa-s are given in the appendix. When shear stress t assumes its alternate identify, momentum flux, the pascal-second is interpreted as Ikg/ms). 

In order to study the viscosity effect on the quenching of triplet excited state of (53) by TEMPO, chemically induced dynamic electron polarization and transient absorption spectra have been measured in ethylene glycol, 1,2-propanol and their mixtures. The results indicate that the quenching rate constant is viscosity-dependent and decreases linearly with the increase in solvent viscosity. The spectroscopy and dynamics of near-threshold excited states of the isolated chloranil radical anion have been studied using photoelectron imaging taken at 480 nm, which clearly indicates resonance-enhanced photodetachment via a bound electronic excited state. Time-resolved photoelectron imaging reveals that the excited state rapidly decays on a timescale of 130 fs via internal conversion. ... 

Dynamic LLS is famous for its application in particle sizing. G(F) obtained from a dilute dispersion is converted to the hydrod5mamic size distribution /(iSh) by means of D = Vlq and the Stokes-Einstein relation D = k TI6nr)R with k, T, and ri being the Boltzmann constant, the absolute temperature, and solvent viscosity, respectively. All the parameters in the conversion are either well-known constants or precisely measurable by other methods. Therefore, using dynamic LLS to size the particle size distribution is an absolute method without any calibration. Many commercial instruments have been successfully developed on this principle details have been compiled in a book (32). However, a combination of static and dynamic LLS can provide much more than the characterization of the weight-average molar mass and the particle size distribntion. 

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