Functional Design Considerations

The screw consists of at least five distinct geometrical sections. The first three sections, feed, compression, and metering, are the same as on a conventional screw. After the metering section there is a rapid decompression followed by the extraction section, which, in turn, is followed by a rapid compression and a pump section. Two important functional requirements for good devolatilization are zero pressure in the polymer under the vent port and completely molten polymer under the vent port. 

Diffusion coefficients are very much temperature dependent. When the polymer is below the melting point, diffusion generally occurs at an extremely low rate. The polymer, therefore, should be above the melting point to increase the rate of diffusion and with it the devolatilization efficiency. Even when the polymer is in the molten state, the diffusion coefficients can often be increased substantially by increasing the temperature of the polymer melt [11]. Further, when the polymer is in the molten state, surface renewal is possible. This greatly enhances the devolatilization process. The extent of surface renewal is a strong function of the screw 

If the flight pitch is constant and the polymer melt viscosity can be described by Eq. 8.78, the maximum diehead pressure for effective devolatilization can be written as [2]  

This equation was derived by assuming a zero pressure gradient in the metering section and by using the Newtonian throughput-pressure relationship, Eq. 7.198. The optimum channel depth in the pump section Hp can be obtained by setting  

This results in the following expression for the optimum channel depth in the pump section  

---

Fuze Handbook, Up-dated The engineering textbook on fuze design is arranged in three parts (1) Fundamental principles (covers purposes, general functioning, design considerations, initiation, and explosive train)... 

In comminution processes, energy consumption is often the most important design consideration. In fact, it has been estimated that 1 per cent of global energy consumption is used in comminution. Energy consumption is a function of the size and hardness of the material and the required degree of breakage or surface area formation. Empirically... 

The split-fraction coefficients can be estimated by considering the function of the process unit, and by making use of any constraints on the stream flows and compositions that arise from considerations of product quality, safety, phase equilibria, other thermodynamic relationships and general process and mechanical design considerations. The procedure is similar to the techniques used for the manual calculation of material balances discussed in Section 4.3. 

From these selected references and others, we have confidence that the FDA and USP accept automation in general, and automated dissolution in particular. The references confirm the importance of maintaining the same basic chemistry and adhering to compendium design as closely as possible. This is not only a regulatory consideration but also one of practicality. It is extremely important that methods can be successfully transferred to other sites and apparatus (automated or otherwise). With this information we may proceed with our functional design of an automated dissolution system. 

The other members of the water-reducing admixture group possess some other function which could not be obtained by mix design considerations. 

For analytical testing purposes, there are two key considerations in designing an isolator. The first consideration is that the design of the isolator should be such that the individual utilizing the isolator is sufficiently protected from exposure to the material being tested. The second consideration is that the isolator construction must be such that the analytical equipment placed inside the isolator can function properly. These key design considerations are discussed in detail below. 

The innovative potential and the ingenuity which have gone into designing libraries, vectors and selection protocols are impressive. However, considerable input has come from structural modelling and design considerations, in the proliferation of phage-display scaffolds to provide constrained variable epitopes in different environments or contexts . In addition the method has been used to understand protein folding, protein-protein interactions and structure-function relationships in catalysis. I hope that, in this review,... 

After the dispersion leaving the reactor is separated in the settler (decanter), the liquid hydrocarbon product stream is partially flashed, forming a vapor phase, mainly isobutane. The remaining liquid is hence cooled, and it is used as the coolant in the tube bundle of the reactor. As heat is transferred there, more hydrocarbons vaporize, forming a liquid-gas mixture. Obviously, temperature gradients occur on both sides of the tube bundle as a function of reactor length. Heat transfer (and temperature control) is an important design consideration in contactors. 

---