Process Volume Effect

The real power of the Weibull analysis is the possibility to evaluate the volume effect on the mechanical characteristics of materials. Any work piece or specimen 

Using the Weibull cumulative probability function given by (4.37) Eq. 4.44 

Therefore, testing the same material first with n specimens of large volume Vi that render a scale factor i and then with n specimens of small volume Vg that 

The scale factor Xq i obtained with a series of n large specimens is lower than that competing to the same number n of small specimens. It also indicates that the value corresponding to a probability of survival of 63.2 % is lower for larger volumes. In general, it is possible to write  

Sample problems 6. and 7. of this section wUl also address the issue. Therefore, the WeibuU exponent wUl be high for good quaUty materials, but also for high process volumes. The correct expression for Eq. 4.45 is then 

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The corresponding point is shown with a full square in Fig. 5.25 that is an enlarged detail of Fig. 5.21. Taking into consideration also the process volume effect Csz =0.73 already found in sample problem N. 2 we obtain a point marked by the open square in Fig. 5.25. 

Plates Containing Bore Holes-Process Volume Effect... 

Note that it has not been considered the process volume effect since at 1.000 cycles the material is working in full plastic regime with low cycle fatigue. The process volume, then, is the entire volume ahead of the hole, from both sides. 

Catalytic gas-phase reactions play an important role in many bulk chemical processes, such as in the production of methanol, ammonia, sulfuric acid, and nitric acid. In most processes, the effective area of the catalyst is critically important. Since these reactions take place at surfaces through processes of adsorption and desorption, any alteration of surface area naturally causes a change in the rate of reaction. Industrial catalysts are usually supported on porous materials, since this results in a much larger active area per unit of reactor volume. 

In the following paper, the possibility of equilibration of the primarily adsorbed portions of polymer was analyzed [20]. The surface coupling constant (k0) was introduced to characterize the polymer-surface interaction. The constant k0 includes an electrostatic interaction term, thus being k0 > 1 for polyelectrolytes and k0 1 for neutral polymers. It was found that, theoretically, the adsorption characteristics do not depend on the equilibration processes for k0 > 1. In contrast, for neutral polymers (k0 < 1), the difference between the equilibrium and non-equilibrium modes could be considerable. As more polymer is adsorbed, excluded-volume effects will swell out the loops of the adsorbate, so that the mutual reorientation of the polymer chains occurs. 

Rheological experiments have shown that the relative viscosity of compositions filled with the above materials is an exponential function of filler content by volume. The impact of an otherwise constant quantity of filler increases in the series FP — LDP — SDP, i.e., symbatically with the probability of particle comminution in the plasticization process. This effect is most clearly apparent for... 

Generally, whenever fluids are processed in a confined space, two different types of phenomena are observed surface and volume effects. An example of a surface effect is a heterogeneously catalyzed reaction occurring at the walls of the vessel, whereas the motion of a fluid due to gravitational forces would be described as a volume effect. In brief, it can be stated that the surface effects gain in importance compared with the volume effects when the size of a reactor decreases. In particular, the reduction of length scale leads to a... 

The scale up prospects of hom type systems are very poor as it cannot effectively transmit the acoustic energy into large process volume. Usually, ultrasonic hom type systems are generally recommended for laboratory scale investigations. The disadvantages of using the hom systems at large scales of operation are ... 

This section discusses the techniques used to characterize the physical properties of solid catalysts. In industrial practice, the chemical engineer who anticipates the use of these catalysts in developing new or improved processes must effectively combine theoretical models, physical measurements, and empirical information on the behavior of catalysts manufactured in similar ways in order to be able to predict how these materials will behave. The complex models are beyond the scope of this text, but the principles involved are readily illustrated by the simplest model. This model requires the specific surface area, the void volume per gram, and the gross geometric properties of the catalyst pellet as input. 

The importance of free volume effects in diffusional processes at a molecular level should be further emphasized. An empirical relationship between viscosity and free volume was proposed by Doolittle ... 

Another contribution to AjF was observed to arise in some reactions involving high steric hindrance (see references cited in Ref. 275) this is indicated as A V, the steric volume of activation. According to observation, high pressure promotes the most hindered process. This effect has been ascribed to a displacement of the most hindered transition states toward the more compact products in the reaction profiles [285]. 

Because there is no energy barrier opposed to compositional fluctuations for compositions within the spinodal field, the decomposition mechanism is entirely a diffusional process. Unmixing effectively begins with a minimal compositional fluctuation that extends over the entire volume of the system. 

In response to recent federal and local environmental concerns (e.g., industrial emission controls and lead phase-out) and to the growing interest of refiners in cracking residual fuels, researchers have generated new families of cracking catalysts. There is now a need to review the merits of these newly developed materials. This volume contains contributions from researchers involved in the preparation and characterization of cracking catalysts. Other important aspects of fluid catalytic cracking, such as feedstocks and process hardware effects in refining, have been intentionally omitted because of time limitations and should be treated separately in future volumes. 

According to the vendor, the RSC process is effective with a waste loading of 85 to 100% by volume. The process is also capable of incorporating rubble and debris into the final product however it is limited by the size and amount of rubble it can incorporate effectively. 

Plasticizers are compounds which increase the flexibility and process -bility of polymers. It has been postulated that the added plasticizer reduces the intermolecular forces in PVC and increases the free volume. Effective plasticizers, like effective solvents, have solubility parameters within 1.8 H (Hildebrand units) of that of the polymer. 

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