Heat transfer between particle beds and submerged surfaces

Theoretical modelling of heat transfer to particle beds comprises two sequential steps: transfer from the heating surface to contacting particles followed by transfer to the interior of the bed. Two different limiting case can be formulated for the second step: unmixed and homogeneously mixed bed. In the case, heat is transferred gradually via a repeated sequence of heat transfer in the gap between adjacent particles and conduction in the particulate material. In the second case, heat is transferred to the interior of the bed by mixing of particles which have previously attained the temperature of the heating surface. On the other hand, the mixing motion maintains a homogeneous lower temperature throughout the bed. Theory predicts a significant and easily measurable difference in the behaviour of heat transfer coefficients for the two regimes at long contact times t: unmixed beds ∝ $$ \sqrt t $$ and homogeneously mixed beds ∝ 1/t. For short times t, both regimes show the same behaviour, namely of t. From a theoretical standpoint, it makes sense to differentiate further between the behaviour patterns of unmixed beds: at long times t, instantaneous heat transfer coefficients are independent of heat transfer form the heating surface to adjacent particles. Comparison with experimental result from literature shows that the derived models, which are consistent, are suitable for describing the heat transfer from submerged surfaces to unmixed and mixed beds of particles.     

Analysis of nonorthogonal designs: The 2k factorial experiment.

Asimple unweighted means ANOVA of a 2k factorial experiment with unequal and disproportionate cell frequencies resulted in the same sums of squares and F tests as the more complex Method 1 analysis recommended by J. E. Overall et al (see record 1975-20136-001). (6 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of the temperature dependence of the fracture stress of sharp notched bending specimens of a structural steel with respect to intermediate transitions

The flow and fracture stresses, σ_y^g and σ_f^g (δ = crack tip displacement), of sharply notched bending specimens of a structural steel U St 37-1 are measured in the temperature range from full scale to small scale yielding. The best adaption of the experimental results for σ_f^g is obtained by a curve which exhibits an intermediate transition, i.e. which follows in a temperature range between an upper, T_tM¹ and a lower, T_tl¹, transition temperature to the curve σ_y^g(T) for the flow stress with a constant δ = δ₁. This transition corresponds to that of the slip to the twin nucleated fracture. Two analyses [3,5] according to the local fracture stress, σ_f^*, concept show that the amount and the temperature dependence of σ_f^* are somewhat different for both methods, but that both exhibit an increase of σ_f^* in the transition range. It is concluded that each transition in the nucleation mode of the fracture is connected with such a transition in the fracture stress. It may, however, become indistinct or even be covered by the scatter of the experimental points.     

1H-NMR of the amidation of syndiotactic poly(methacrylic acid) with carbodiimide

Summary The reaction of syndiotactic poly(methacrylic acid) with dicyclohexylcarbodiimide in the presence of benzylamine yields syndiotactic methacrylic acid-methacryloyl-N-benzylamide copolymers. A limiting conversion to amide of about 62% and a tendency of alternation for the monomer units is observed by¹H-NMR. The amidation is accompanied by the formation of a smaller amount of cyclic imide as a side reaction. The imide portion can also be transformed into amide by a consecutive hydrolysis step.     

Nuclear susceptibility of liquid He3—I

An accurate study of the nuclear molar susceptibility of liquid He ³ has been made. Particularly emphasized was the comparison of in the liquid with that in solid He ³ . The experimental results of this work define a three-dimensional surface T/C versus temperatureT and molar volumeV between 0.35 and 2.2° K and between 26 and 37 cm ³ /mole. HereC is the molar Curie constant of solid He ³ , assumed to beN _A µ ² /k _B T, where is the nuclear magnetic moment and N _A Avogadro's number. The measurements were accomplished using a carefully designed pulsed NMR set, and sample-and-hold circuitry with a digital voltmeter for readout. Most of the measurements were made at fixed temperature relative to a sample of bcc solid He ³ , usually at a density of 22.50 cm ³ /mole. These data were complemented by measurement of versusT at fixed pressure. Except at the highest temperatures, the scatter in the values was about 0.3%, and the results are estimated to be accurate within ±0.5%. At sufficiently high temperatures, the susceptibility is found to tend asymptotically towards Curie's law by comparison with solid He ³ . The deviation from Curie's law, to temperatures near 0.5° K, could be empirically written as (1–T/C)=bT ^d whereb andd are density-dependent parameters. Comparison with theories and previous measurements of the nuclear susceptibility are made. Below 1° K, the present results are about midway between those of Beal and Hatton ⁹ and those of Thomson, Meyer, and Adams. ⁸ Research supported by a grant from the National Science Foundation and from the AROD. The results have been presented as an Abstract inBull. Am. Phys. Soc. 14, 601 (1969), submitted in partial fulfillment for the Ph.D. in physics by J. R. Thompson, May 1969.     

Effect of formulation composition on the properties of controlled release tablets prepared by roller compaction

This study discusses the effect of formulation composition on the physical characteristics and drug release behavior of controlled-release formulations made by roller compaction. The authors used mixture experimental design to study the effect of formulation components using diclofenac sodium as the model drug substance and varying relative amounts of microcrystalline cellulose (Avicel), hydroxypropyl methylcellulose (HPMC), and glyceryl behenate (Compritol). Dissolution studies revealed very little variability in drug release. The t₇₀ values for the 13 formulations were found to vary between 260 and 550 min. A reduced cubic model was found to best fit the t₇₀ data and gave an adjusted r-square of 0.9406. Each of the linear terms, the interaction terms between Compritol and Avicel and between all three of the tested factors were found to be significant. The longest release times were observed for formulations having higher concentrations of HPMC or Compritol. Tablets with higher concentrations of Avicel showed reduced ability to retard the release of the drug from the tablet matrix. Crushing strength showed systematic dependence on the formulation factors and could be modeled using a reduced quadratic model. The crushing strength values were highest at high concentrations of Avicel, while tablets with a high level of Compritol showed the lowest values. A predicted optimum formulation was derived by a numerical, multiresponse optimization technique. The validity of the model for predicting physical attributes of the product was also verified by experiment. The observed responses from the calculated optimum formulation were in very close agreement with values predicted by the model. The utility of a mixture experimental design for selecting formulation components of a roller compacted product was demonstrated. These simple statistical tools can allow a formulator to rationally select levels of various components in a formulation, improve the quality of products, and develop more robust processes.     

Use or disposal of by-products and spent material from the vegetable oil processing industry in Europe

The tendency in the oil and fat industry in Europe as far as by-products and spent material are concerned is to use and regenerate as much as possible for chemical-technical purposes. Materials with a high thermal value which are not suitable or profitable for use in chemical-technical products will in the future probably be utilized as a fuel in combination with fuel oil. By-products and spent material that cannot be exploited in the manners outlined above will be deposited in dumps. Incineration is another possibility. However, the quantities of waste must be of a considerable magnitude if this method is not to be too expensive.     

Technische Projekt- und Arbeitsorganisation in Anlagenbauunternehmen

Engineering project and labour organization in plant construction companies . Problems and trouble-shooting in the organization of engineering projects are discussed with special emphasis being laid on the prerequisites for the use of matrix-oriented company structures. The current form of project organization, the tasks of project management, the make up of the project team, the project directives and general prerequisites of works organization which are embodied in factory rules and regulations are dealt with.