Numerical studies on orthokinetic agglomeration in a turbulent channel flow and in a stirred tank are presented. By using a lattice Boltzmann scheme to simulate the turbulent flow field, and a Monte ...Carlo algorithm to solve the particle size distribution, the dependence of the agglomeration rate on the shear rate and the turbulent transport of particles is investigated. It is found that local flow information is needed to model agglomeration and that a description in terms of a volume-averaged agglomeration rate constant
β
0 is inadequate for both geometries. Furthermore, turbulent transport of particles is found to be an important factor in the overall agglomeration rate.
Scale‐up of orthokinetic agglomeration in stirred‐tank reactors was studied numerically. A computer code based on the lattice‐Boltzmann method was used to perform large eddy simulations. To account ...for the dependence of agglomeration on hydrodynamics, the kinetic relation proposed by Mumtaz et al. was applied locally. The convection‐reaction equation governing the evolution of the particle‐number concentration was solved at the same resolution as the flow field. Three scale‐up rules were studied: scale‐up at constant Re‐number, constant specific power input, and constant impeller tip speed. Vessel sizes varying from 1 to 10,000 L were simulated. The use of two types of impellers (Rushton turbine and Pitched Blade turbine) allowed for investigating the dependence of agglomeration on the macroscopic flow pattern in a reactor. Inhomogeneities in stirred‐tank flow caused unpredictable scale‐up behavior. Scale‐up at constant power input yielded the most constant reactor performance. Impeller geometry had a drastic impact on the observed agglomeration rate, even if the difference in Po number was taken into account.
A numerical study on the scale-up behaviour of orthokinetic agglomeration in stirred tanks is presented. Large Eddy flow simulations were performed to obtain an accurate description of the turbulent ...flow encountered in stirred vessels, equipped with either a Rushton or a pitched blade turbine. Simultaneously, the convection-reaction equation for the particle number concentration is solved. Equal resolutions were used for the flow simulations and the particle concentration equation. Agglomeration was incorporated by making use of the nonlinear agglomeration model proposed by Mumtaz et al. Trans. Inst. Chem. Eng. 75 (1997) 152. Reactor performance for vessel sizes in the range of 1 to 10
000 l was simulated. Three scale-up rules (viz. constant
Re number, specific power input, and impeller tip speed) were investigated. It was found that impeller shape, vessel size, and
Re number have a profound effect on reactor performance.
The book's emphasis on types of assessment, genetic testing and counseling, and medical and psychological treatment will be exceedingly useful to health care providers navigating the new diagnostic ...criteria introduced in DSM-5.
Frontline Workers in Long-Term Care Feldman, Penny Hollander, Ed
Generations (San Francisco, Calif.),
1994, Letnik:
18, Številka:
3
Journal Article
Recenzirano
In this theme issue, 18 articles discuss the motivation for and benefits of working with old and dying people, nursing homes, ethical issues, and the training of home health care workers. Employee ...recruitment and retention and the economics of health care for the frail elderly are also addressed. (JOW)
A non-intrusive technique has been developed for measuring agglomeration rate constants beta(sub0) in a constant shear field. A particulate suspension, with a mean particle diameter d of about 10 mu ...m, is introduced into an optically accessible cylindrical Couette flow device. The suspension is illuminated by a pulsed laser and observed with a CCD camera. The recorded images are analysed offline to determine the particle number concentration and a measure of the particle size. The time evolution of these quantities is fitted to an agglomeration rate law, from which the agglomeration rate constant is subsequently derived. Test results show that the set-up is well suited to determining particle concentrations, while only relative particle size information could be obtained. One set of agglomeration rate constants, measured at 7 different shear rates between 15 and 55 s(super-1) , was obtained. A distinct maximum for beta(sub0) was found at a shear rate of 30 s(super-1), which will be the subject of further study. (Original abstract - amended)
Increasing complexity and competitiveness in research environments, the prevalence of interdisciplinary and international involvement in research projects, and the close coupling of commerce and ...academia have created an ethically challenging environment for young scientists and engineers. For the past several decades, federal research agencies have supported projects to meet the need for mentoring and ethics training in graduate education in research, often called training in the responsible conduct of research. Recently, these agencies have supported projects to identify ethically problematic behaviors and assess the efficacy of ethics education in addressing them.
With support from the National Science Foundation, the National Academy of Engineering Center for Engineering, Ethics, and Society held the workshop "Ethics Education and Scientific and Engineering Research: What's Been Learned? What Should Be Done?" on August 25 and 26, 2008.
The workshop, summarized in this volume, discussed the social environment of science and engineering education; the need for ethics education for graduate students and postdoctoral fellows in science and engineering; models for effective programs; and assessment of approaches to ethics education, among other topics.
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