Influence of developing flow on the heat transfer in laminar oscillating pipe flow

A theoretical analysis was performed to evaluate the influence of developing flow on the heat transfer associated with laminar oscillating pipe flow. Simplified analytical approaches are briefly discussed before an investigation based on the numerical solution of the conservation equations for mass, momentum and energy is presented, assuming constant wall temperature and an incompressible viscous fluid. Focusing on operating conditions as found in heat exchangers of regenerative thermal machines, like Stirling engines or Vuilleumier heat pumps, numerous calculations of the flow field and the heat transfer have been executed covering wide ranges of the characteristic dimensionless groups. The results are presented in tems of correlations of the mean Nusselt number averaged on the pipe length and a distribution function describing the local heat transfer. Furthermore, it is shown that the derived correlations are also applicable to compressible fluid flow, provided that the relative pressure amplitude is within the limits typical of regenerative thermal machines.     

Effects ofbis homoallylic and homoallylic hydroxyl substitution on the olefinic13C resonance shifts in fatty acid methyl esters

The online version of the original article can be found at     

A SEMI-EMPIRICAL APPROACH TO PREDICT THE TOTAL COLLECTION EFFICIENCY OF ELECTROSTATIC PRECIPITATORS

Using empirical data for the effective migration velocity, the Deutsch-Anderson equation has been widely used for calculation of the total collection efficiency and design of electrostatic precipitators (ESPs). Based on a normal particle size distribution, the present paper develops a semi-empirical equation for the total collection efficiency of ESPs. The equation is then simplified and extended to other particle size distributions. The simplified equation shows that the total collection efficiency increases with increasing mass median diameter of particles and with increasing electrical field strengths. The effective migration velocity is found to be directly proportional to the mass median diameter and to the electrical field strengths for particle charging and collection. Moreover, an example is given to illustrate how to use the present simplified model in the design of ESPs.     

Analytical13C NMR: Detection,quantitation, and positional analysis of butyrate in butter oil

The amount of butyrate contained in a complex mixture of butter oil triglycerides was 10.3 mole % as determined by natural abundance¹³C Fourier transform pulse nuclear magnetic resonance (NMR) spectroscopy. This NMR technique also demonstrated the primary isomeric positioning (>97%) of the butyrl group without the need for altering or fractionating the fat mixture.     

MODELING OF THE PRESSURE DROP AND FLOW FIELD IN A ROTATING FLUIDIZED BED

Rotating fluidized beds (RFB) have found applications as dust filters, dryers, particle coaters, and granulators, and recently as catalytic reactors for the clean up of diesel exhaust. However, successful design and operation of an RFB requires an in-depth understanding of the fundamentals of the fluid dynamics involved. In this study, mechanistic models have been developed to account for the pressure drop relationship with respect to rotating speed, flow rate, properties of the granular particles, and fluidization conditions in the RFB. The models show that the total pressure drop across the bed is quadratically dependent on the rotating speed as well as the flow rate. These quadratic relationships have also been validated experimentally. The pressure drop relationship has further been validated through a full flow field numerical simulation of flow through a rotating bed with a slotted cylindrical distributor but without granular particles in the bed. Using our analytical model together with experimental results from three different types of distributors, a slotted cylinder with a thin metal screen, a perforated cylinder with a thin metal screen, and a sintered metal cylinder, three semi-empirical quadratic equations are obtained to predict the pressure drop across these distributors. A comparison of the distributor pressure drop with that across the fluidized bed (granules only) shows that the pressure drop across the distributor is appreciable and cannot be neglected in RFB applications. The higher the rotating speed, the more significant the pressure drop across the distributor.     

Decision-making and opinion formation in simple networks

In many networked decision-making settings, information about the world is distributed across multiple agents and agents’ success depends on their ability to aggregate and reason about their local information over time. This paper presents a computational model of information aggregation in such settings in which agents’ utilities depend on an unknown event. Agents initially receive a noisy signal about the event and take actions repeatedly while observing the actions of their neighbors in the network at each round. Such settings characterize many distributed systems such as sensor networks for intrusion detection and routing systems for Internet traffic. Using the model, we show that (1) agents converge in action and in knowledge for a general class of decision-making rules and for all network structures; (2) all networks converge to playing the same action regardless of the network structure; and (3) for particular network configurations, agents can converge to the correct action when using a well-defined class of myopic decision rules. These theoretical results are also supported by a new simulation-based open-source empirical test-bed for facilitating the study of information aggregation in general networks.     

“Dialdehyde Cellulose” Nanofibers by Electrospinning as Polyvinyl Alcohol Blends: Manufacture and Product Characterization

A nanofiber was obtained by electrospinning of “dialdehyde cellulose” (periodate-oxidized cellulose, DAC) and polyvinyl alcohol (PVA), using only water as the solvent. Celluloses of four different origins were fully oxidized with sodium periodate to water-soluble DAC. Aqueous solution of DAC showed inadequate spinnability regardless of the polymer concentration and the electrospinning conditions used. Addition of PVA improved the solution's viscoelasticity and, consequently, the solution's spinnability. We examined the effects of DAC/PVA composition and electrospinning parameters on fiber morphology. Highly homogeneous nanofibers were prepared from 1:1 up to 2:1 (weight) DAC/PVA blends while samples of lower viscosity or higher relative DAC contents resulted in continuous, beaded fiber networks. Characterization of the electrospun fabrics revealed a highly crosslinked DAC structure reinforced with PVA, strongly interacting through hemiacetal bonds and hydrogen bonding. Fluorescence labeling confirmed the presence of reactive aldehyde functionalities in the electrospun web. The versatile properties of DAC as reactive material can now be imparted on electrospun fiber and nanofiber material – which was not possible so far –further widening the application scope of this interesting cellulose derivative.