Recirculating Flow System Research Articles

Separation of gas and organic/water mixtures by MFI type zeolite membranes synthesized in a flow system

MFI type zeolite membranes were synthesized in a recirculating flow system at 95 °C where the synthesis solution was flown over the tubular α-alumina supports. The performance of the membranes for the separation of binary gas mixtures and alcohol/water liquid mixtures was investigated. A membrane synthesized by two consecutive synthesis steps had a separation selectivity of 15 and 11 for equimolar mixtures of n-C 4H 10/CH 4 and n-C 4H 10/N 2 at 200 °C, respectively. The membrane selectively permeated large n-C 4H 10 over small CH 4 and N 2, suggesting that the separation is essentially adsorption-based and the membrane has few nonselective intercrystalline pores. The selectivities in the pervaporation separation of 5% ethanol/95% water mixture were 43 and 23 with permeate fluxes of 0.2 and 1.9 kg/m 2 h at 25 and 85 °C, respectively. The separation performance of membranes showed that MFI type membranes prepared in a recirculating flow system can be used both in the separation of gas and liquid mixtures.

Model extension and improvement for simulator-based software safety analysis

One of the major concerns when employing digital I&C system in nuclear power plant is digital system may introduce new failure mode, which differs with previous analog I&C system. Various techniques are under developing to analyze the hazard originated from software faults in digital systems. Preliminary hazard analysis, failure modes and effects analysis, and fault tree analysis are the most extensive used techniques. However, these techniques are static analysis methods, cannot perform dynamic analysis and the interactions among systems. This research utilizes “simulator/plant model testing” technique classified in (IEEE Std 7-4.3.2-2003, 2003. IEEE Standard for Digital Computers in Safety Systems of Nuclear Power Generating Stations) to identify hazards which might be induced by nuclear I&C software defects. The recirculation flow system, control rod system, feedwater system, steam line model, dynamic power-core flow map, and related control systems of PCTran–ABWR model were successfully extended and improved. The benchmark against ABWR SAR proves this modified model is capable to accomplish dynamic system level software safety analysis and better than the static methods. This improved plant simulation can then futher be applied to hazard analysis for operator/digital I&C interface interaction failure study, and the hardware-in-the-loop fault injection study.

310 実験と数値計算によるミニチャンネル伝熱機構の解明(数値計算)(2)(OS3-2 マイクロ・ナノフルイズ,OS3 マイクロ・ナノフルイズ,オーガナイズドセッション)

The authors have reported that minichannel flow system had high heat transfer coefficient. We investigated experimentally and numerically the heat transfer and flow structure of single and array minichannel combined with impingement flow system. The diameter D of the channel was 1.27 mm and length to diameter ratio L/D was 5. The minichannel array was so called shower head which was constructed by 19 minichannels located at the apex of equilateral triangle, the side length S of which was 4 mm. The mechanism of high heat transfer was studied numerically by the Reynolds averaged Navier-Stokes equation and k-co turbulence model. The limiting streamline pattern was correlated well to the surface heat flux distribution. The high heat transfer in the single minichannel was achieved by suppressing the development of boundary layer under strong pressure gradient near the channel inlet and by the formation of large recirculating flow system in the downstream plenum of the minichannel exit. These heat transfer mechanisms became dominant when the channel size fallen into the regime of minichannel. The heat transfer performance of minichannel array was equivalent to that of impingement jet.

Sickle erythrocytes increase prostacyclin and endothelin-1 production by cultured human endothelial cells under flow conditions.

We investigated the effects of sickle erythrocytes on the production of vasotone mediators in endothelial cells (ECs) using an in vitro recirculating flow system. Sickle erythrocytes increased the EC production of two important vasoactivators, prostacyclin and endothelin-1, under venous wall shear stress conditions of 1dyncm2. The presence of interleukin-1 in the perfusion system, as a model for inflammatory cytokine effects, enhanced the overall amounts of released prostacyclin but did not affect the production of endothelin-1. This study demonstrates the effects of sickle erythrocytes on the function and metabolism of ECs under vascular flow environments. The altered production of vasoactivators may contribute to the vasotone instability and vasoocclusive crises in sickle cell anemia.

Shear-induced platelet activation and adhesion on human pulmonary artery endothelial cells seeded onto hydrophilic polymers.

We evaluated platelet activation and adhesion on two plasma polymerized surfaces, N-vinyl pyrrolidone (NVP) and gamma-butyro lactone (GBL), which have been shown previously to promote endothelial cell growth and adhesion as well as fibronectin-coated glass (1 microg/cm(2)) coverslips. Human pulmonary artery endothelial cells were seeded onto coverslips at a low density ( approximately 20,000 cells/cm(2)) and grown to confluence (3-5 days). The materials, both with and without ECs, were then exposed to a shear rate of 400 s(-1) in a closed loop recirculating flow system containing human platelet-rich plasma. Plasma samples were taken at 0, 5, 15, 30, and 60 min and analyzed for platelet and coagulation activation. The coverslips were examined for EC coverage and platelet adherence. EC retention over a 1-h period was approximately 75% for all three materials. All three materials without ECs were highly platelet activating having similar P-selectin expression, platelet factor 4 (PF4) release, mepacrine uptake, and microparticle production. Both microparticle production and platelet adhesion were significantly lower in EC-seeded materials. Dense granule and PF4 release were both slightly diminished in all three materials seeded with ECs. P-selectin expression was reduced slightly for GBL, but remained the same for the other two materials. The EC-seeded materials displayed favorable characteristics with respect to platelet activation and adhesion; however, they still demonstrated some thrombogenic tendencies due to EC loss and exposure of the underlying substrate. Therefore, both EC coverage and EC hemostatic function are important factors in determining the thromboresistance of an EC-seeded surface.

COMBINED USE OF AN ELECTRONIC ANTIFOULING TECHNOLOGY AND BRUSH PUNCHING FOR SCALE REMOVAL IN A WATER-COOLED PLAIN TUBE

The objective of the present study was to investigate the benefit of the combined use of an electronic antifouling (EAF) technology and brush punching for scale removal in a shell-and-tube heat exchanger. Two fouling experiments were conducted with new plain tubes: one without an EAF treatment and the other with it. Scale inside the two tubes was produced in a recirculation-flow system with an artificially hardened water of 7.5 mol/m3. After passing tap water through each tube for 4 days, the fouling resistance in the tube with the EAF treatment was measured and found to be 46% less than in the one without the EAF treatment. Subsequent brush punching of the tube for the case with the EAF treatment cleaned almost all of the remaining scale, thus recovering the initial overall heat transfer coefficient values, resulting in zero fouling resistance. However, for the case without the EAF treatment, brush punching was not effective in removing scale. Both the present experiment and earlier SEM photographs support the benefit of the combined use of the EAF technology and brush punching on scale removal in heat exchangers.

Methods and apparatus for in situ investigations with the scanning force microscope

Various methods of carrying out time resolved in situ monitoring of crystallization processes with the scanning force microscope (SFM) were tested and improved. First investigations, taking place in static liquids, were performed in a simple cup sample holder and in the liquid cell supplied by the manufacturers of the SFM. Continuous flow conditions were realized with a new recirculating flow system, which in addition allows temperature control. The different apparative approaches were tested with lab-grown crystals of L-ascorbic acid and lithium fluoride, as well as freshly cleaved fragments of the naturally occurring mineral calcite.

An In Vitro Evaluation of an Artificial Heart

Interactions between human blood and the Penn State Artificial Heart were examined in vitro to study the effects of various operating conditions on the hematologic response. A dual-loop recirculating flow system that accommodated human blood was developed and blood was subjected for 3 hr to various operating conditions known to alter fluid mechanics in the artificial ventricle. The operating conditions investigated were: 60 beats/min at 50% systolic duration, 60 beats/min at 30% systolic duration, and 90 beats/min at 50% systolic duration. Quantification of plasma free hemoglobin provided a direct indicator of hemolysis in the flow system. Platelet number and beta-thromboglobulin levels were monitored to investigate thrombotic activity, and levels of complement 3a were measured to examine complement system activation. The system was effective in demonstrating the relative hemolytic properties of the operating conditions. Ninety beats/min induced 37% more hemolysis than 60 beats/min at 50% systolic duration, and 50% systolic duration induced 32% more hemolysis than 30% systolic duration at 60 beats/min. There were no statistically significant changes in either platelet number or beta-thromboglobulin levels during the 3 hr recirculation period. Increases were seen in complement 3a levels, but these appeared to be surface-induced and not sensitive to the different operating conditions. These studies demonstrate the usefulness of the flow system in examining the relative hemolytic properties of the artificial ventricle, and suggest that bulk turbulent stresses may play a more important role than laminar wall shear stresses in mediating blood damage in this artificial ventricle.

Trapping and measurement of short-lived alkylating agents in a recirculating flow system

A procedure has been developed for estimating the survival time of short-lived alkylating agents in a flow system at physiological temperature and pH. The system simulated the slow release into the bloodstream of a reactive compound formed in the liver. A solution of the reactive compound was injected slowly into a fast stream of aqueous fluid and immediately mixed. After a delay (up to 1 min) determined by a length of tube, during which hydrolysis took place, the surviving reactive compound was trapped on a column of immobilized thiol (thiol-Sepharose), and the fluid was recirculated via a reservoir. The system was used to study the hydrolysis of the pyrrolizidine alkaloid metabolites dehydromonocrotaline, dehydro-anacrotine and dehydroretrorsine. The S-bound pyrrolic moiety in the trap was measured colorimetrically and hydrolysis rates were estimated after a series of 1-h runs with different delay times. Hydrolysis of dehydroretrorsine was very rapid, whereas the hydrolysis of dehydromonocrotaline and dehydro-anacrotine fitted biphasic first-order reactions, with a faster first phase. By isolating and identifying the trapped products from dehydromonocrotaline it was shown that the two phases involved hydrolysis of the 7- and 9-ester groups, respectively. The results supported the view that a proportion of the reactive metabolites from the alkaloids monocrotaline and anacrotine would be able to survive long enough to be transported from the liver to the lungs of a rat. The flow system would be applicable to the study of other types of short-lived metabolites.

Enzymatic production and analysis of d-xylulose with a recirculating flow system and post-column liquid chromatographic detection using a co-immobilized enzyme reaction and a chemically modified electrode

A pure d-xylulose and standard was produced by isomerization of d-xylose in a recirculating flow system incorporating an enzyme reactor containing immobilized xylose isomerase. The d-xylulose formed was purified chromatographically. A selective chromatographic detection system was used in the post-column mode. It consisted of a co-immobilized enzyme reactor (CIMER) with xylose isomerase, mutarotase and glucose dehydrogenase on-line with a chemically modified electrode for selective elctrochemical oxidation of NADH. The pure standard was compared with commercially available d-xylulose, which was confirmed to contain impurities of d-glucose and d-xylose.

Fuzzy logic control application for BWR recirculation flow control system.

There has been increasing necessity for load following and/or AFC (Automatic Frequency Control) operation along with the growth in the share of nuclear power generation in the electric power network. Fuzzy logic control was investigated for application to a BWR recirculation flow control system, in order to obtain a rapid generator power response within an allowable neutron flux overshoot. The proposed controller has two control loops, generator power and neutron flux loop. The fuzzy logic is utilized for weighing these control loops and for controlling the neutron flux. By evaluating the controller performance by numerical simulations on the step response for generator power demand with the model BWR recirculation flow system, more rapid response was obtained than that for conventional proportional plus integral controllers with no neutron flux overshoot beyond alarm activation level.

Effects of Hydrazine on Functional Morphology of Rainbow Trout Embryos and Larvae

Abstract This study was designed to mimic conditions that could exist during an accidental spill of hydrazine, a fuel for missiles and jet engines. Twelve-day-old eggs of rainbow trout Salmo gairdneri were exposed to nominal hydrazine concentrations of 0.01, 0.1, 1.0, and 5.0 mg/liter. The eggs were exposed for 48 hours and subsequently maintained in a recirculating-flow system. Exposure to the various concentrations of hydrazine did not result in significant mortality or reduction in hatching. Aberrations in morphogenesis of larvae included loss of muscular control, reduced growth rates, and loss of tactile sensitivity at concentrations of 1.0 and 5.0 mg/liter.

Kinetics and photochemistry of NO3. Part 1.—Absolute absorption cross-section

The free radical NO3 was generated by the reaction of NO2 with ozone. A recirculating flow system was used so that concentrations of ozone ≈ 5 × 1017 molecule cm–3 could be used. The absorption spectrum of NO3 in the wavelength range 498–671 nm was obtained.An absolute absorption cross-section was obtained at λ≈ 662 nm by using reactant concentrations such that all NO2 was converted to NO3 and no NO3 was lost: that is, the [NO2] added provided the absolute measure of [NO3] in the system. The conditions used were [NO2] [graphic omitted] 1012 molecule cm–3; [O3] [graphic omitted] 3 × 1017 molecule cm–3. At the absorption peak (λ≈ 663 nm) the cross-section is (121 ± 20)× 10–19 cm2 at T= 294 ± 4 K. A comparison is given of this value with the results of other workers, and some implications for the photochemistry of NO3 are suggested.