Design accuracy

Pulsed ECM (PECM) may be a promising way to improve dimensional accuracy control and also to simplify tool design. Accuracies as fine as 0.002 mm have been quoted using current pulse lengths of ca 0.2 to 2.0 ms, at current densities of 55 A/cm. Pulse offtimes are from 1 to 2 ms (7). 

The latest tw o-phase flow research and design studies have broadened the interpretation of some of the earlier flow patterns and refined some design accuracy for selected situations. The method presented here serves as a fundamental reference source for further studies. It is suggested that the designer compare several design concept results and interpret which best encompasses the design problem under consideration. Some of the latest references are included in the Reference Section. No one reference has a solution to all two-phase flow problems. 

This approach is proven for design and prediction of the performance of multiple-bed down-flow reactors. The complication, and a critical difference between this and a bubble column, is that the gas bubbles are formed in situ. The gas flux, and thus gas hold-up, will vary over the bed height. For the down-flow beds, a simplified linear gas hold-up profile was inherent in the design models, but with no apparent penalty in design accuracy. 

SRVs should be taken very seriously. Manufactured from castings, they may not look very sophisticated, but in their design, accuracy and function, they resemble a delicate instrument whilst performing an essential role. Self-contained and self-operating devices, they must always accurately respond to system conditions and prevent catastrophic failure when other instruments and control systems fail to adequately control process limits. 

The thermal conductivity is a property of any given material, and its value must be determined experimentally. For solids, the effect of temperature on thermal conductivity is relatively small at normal temperatures. Because the conductivity varies approximately linearly with temperature, adequate design accuracy can be obtained by employing an average value of thermal conductivity based on the arithmetic-average temperature of the given material. Values of thermal conductivities for common materials at various temperatures are listed in the Appendix. 

Die heads are designed based on assumptions made in areas of unknown and/or unpredictable conditions. With the numbers of variables involved and the way they react under influences by one another, design accuracy just cannot be achieved for all resins and all processing conditions. This creates conditions for unbalanced and unstreamlined flow. 

Doppler reactivity is the other important parameter in FBR cores because it assures the intrinsic safety characteristics of the core. The present cross-section adjustment method cannot treat the Doppler reactivity which is dominated by resonance-peak broadening of cross-sections. We have launched a new study to extend the applicability of the cross-section adjustment and design accuracy evaluation system to the Doppler effect. The basic method to evaluate sensitivity of self-shielding factors has been successfully derived from a generalized perturbation theory, and a prototype system to calculate the Doppler sensitivity is now under verification. 

Dr. J. Madkowiak has committed to paper his 20 years experience as practitioner while operating company ENVIMAC GmbH and as researcher, publishing his results in journals and conference papers. Calculation methods of packed columns, presented in the book will increase the design accuracy of distillation, absorption and extraction which cause up to 60% of total processing costs in chemical industry. 

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