Implementation of liquid crystal thermography to determine wall temperatures and heat transfer coefficients in a tube-in-tube heat exchanger

Liquid crystal thermography was used in a water-operated concentric tube-in-tube heat exchanger to determine local annular heat transfer coefficients at the inlet region. An annular diameter ratio of 0.54 was considered with the inlet and outlet orientated perpendicularly to the axial flow direction. Both heated and cooled cases were considered at annular Reynolds numbers ranging from 1000 to 13 800. Wall temperature distributions were directly measured by means of a coating of thermo-chromic liquid crystals. Local heat transfer coefficients at the inlet were higher than those predicted by most correlations, but good agreement was obtained with some literature.The NRF, TESP, University of Stellenbosch/ University of Pretoria, SANERI/SANDENI, CSIR, EEDSM Hub and NAC.http://www.tandfonline.com/loi/ueht202017-05-31hb2017Mechanical and Aeronautical Engineerin

Investigation into using liquid crystal thermography for measuring heat transfer coefficients and wall temperature profiles at inlets and underdeveloped regions

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.In this paper the wall surface temperature distributions at the inlet regions of a tube-in-tube counter flow heat exchanger were investigated by making use of Liquid Crystal Thermography (LCT). With flow not being fully developed at the inlet region it is difficult to predict the heat transfer coefficient and the appropriate wall temperature on the inner tube under different flow conditions. In this study water was considered in the annulus in the turbulent flow with annular Reynolds numbers of 1 000, 5 000 and 10 000. Local annular heat transfer coefficients were determined from the measured wall temperature profiles and the derived local annular bulk fluid temperatures based on the measured coupled local heat transfer rate in the inner tube. It was found that Liquid Crystal Thermography allowed for the measurement of the average wall temperature which could vary significantly in the inlet region. It was also found that the local heat transfer coefficients varied within a large extent. For the particular heat exchanger under investigation here which had annular diameters of 36 mm and 19.5 mm, heat transfer coefficients reached a maximum from 150 mm onwards after the inlet.dc201

Experimental investigations into viscosity, pH and electrical conductivity of nanofluid prepared from palm kernel fibre and a mixture of water and ethylene glycol

Extensive research has been carried out on the synthesis and applications of nanofluid produced from metals, nonmetals and their oxides. However, little or no attention has been paid to bio-based nanoparticles. The need for the use of bio-based nanoparticles and bio-based nanofluids is imperative to mitigate over-dependence on toxic synthetic nanoparticles. This idea is also in line with renewable and sustainable developmental goals.Moreover, bio-based materials like palm kernel fibre (PKF) constitute environmental waste in some quarters and its conversion to useful products for engineering application will take a long time in solving environmental issues and health hazards. In this study, the top-down approach was used to synthesize nanoparticles from PKF using a ball-milling machine. The PKF nanoparticles with an average size of ∼40 nm were dispersed in an ethylene glycol (EG)/water (50:50) base fluid up to 0.5% of the volume fraction. The viscosity, pH and electrical conductivity of PKF–water and EG (50:50) were studied for temperature ranging from 10 to 60◦C. The results showed that the viscosity of the PKF-based nanofluid increases with an increase in volume fraction and decreases exponentially with an increase in the working temperature of the nanofluid. The pH and the electrical conductivity increased as the volume fraction of the PKF nanoparticle was increased from 0.1 to 0.5%. However, the pH decreased with an increase in the temperature while the electrical conductivity increased with an increase in the volume fraction. Since the notable theoretical models in the literature were unable to estimate the viscosity of the PKF–EG/water nanofluid, in the present case an empirical correlation based on dimensional analysis was proposed to estimate the viscosity of the PKF–EG/water nanofluids.http://www.ias.ac.in/matersci/index.htmlhttp://link.springer.com/journal/12034am2019Mechanical and Aeronautical Engineerin

Microwave-plasma synthesis of nano-sized silicon carbide at atmospheric pressure

A microwave plasma process operating at atmospheric pressure was developed for the synthesis of SiC nanoparticles. The process utilizes methyltrichlorosilane (MTS) as precursor, acting as both carbon and silicon source, along with an additional hydrogen feed to ensure a fully reducing reaction environment. In addition, argon served as carrier gas.. The parameters studied were the H2:MTS molar ratio and the total enthalpy, in the range 0 to 10 and 70 to 220 MJ/kg respectively. The particles size distribution ranged from 15 to 140 nm as determined by SEM and TEM micrographs. It was found that an increase in enthalpy and a higher H2:MTS ratio resulted in smaller SiC particle sizes. The adhesion of particles was a common ocuurence during the process, resulting in larger agglomerate sizes.South African National Research Foundationhttp://www.elsevier.com/locate/ceramint/hb201

Kaartje van de provincie van Zuid Holland na de laaste verbetering

Deze kaart van het zuidelijk deel van Holland komt voor in een atlas van de XVII Provinciën, uitgegeven door de Amsterdamse firma Ottens. De kaart was met name bedoeld ter oriëntatie voor reizigers. Het kaartbeeld is grotendeels gekopieerd naar de 'Nieuwe kaart der provincie van Holland' van Isaak Tirion (1739). Op de kaart van Ottens zijn echter de verveningsactiviteiten in Schieland en Rijnland ingetekend. Die activiteiten vindt men wel terug op Tirions deelkaart van het zuidelijk deel van Holland (zie elders in de collectie gedigitaliseerde kaarten van Holland en Utrecht). Mogelijk heeft Ottens ook die kaart benut

Charge breeding time investigations of electron cyclotron resonance charge breeders

To qualify electron cyclotron resonance charge breeders, the method that is traditionally used to evaluate the charge breeding time consists in generating a rising edge of the injected beam current and measuring the time in which the extracted multicharged ion beam reaches 90% of its final current. It is demonstrated in the present paper that charge breeding times can be more accurately measured by injecting short pulses of 1 + ions and recording the time resolved responses of N + ions. This method is used to probe the effect of the 1 + ion accumulation in the plasma known to disturb the buffer gas plasma equilibrium and is a step further in understanding the large discrepancies reported in charge breeding times. The experiments are conducted injecting a 85 Rb + ion beam into the Laboratoire de Physique Subatomique et de Cosmologie (LPSC) charge breeder operated with helium as a buffer gas. The time needed for the extraction of 90% of the multicharged ions in short pulse mode is found slightly shorter (9%) than the charge breeding time measured with the traditional method. The charge breeding efficiency is identical with both methods. The pulse width and amplitude of the 1 + injection pulses have been varied to study their influence on the N + response and temporal parameters are proposed to qualify the time response. The short pulse method can be used to study the influence of the ion source tuning parameters on the charge breeding temporal characteristics. For example, it is shown here that an increase of the minimum magnetic field strength of the LPSC charge breeder in the range 0.432–0.444 T improves the multicharged ion confinement in the electron cyclotron resonance plasma, and so increases the charge breeding efficiency. The short pulse method is also used to estimate the charge breeding efficiencies of radioactive Rb isotopes taking into account their half-lives and charge states. The neutron-rich heavy isotopes have short half-lives, which makes the charge state distributions shift to lower charge states and the estimated charge breeding efficiencies of high charge states being close to three times less in comparison to the stable ions.peerReviewe

Recent improvements of the LPSC charge breeder

International audiencePSC has developed the PHOENIX electron cyclotron resonance Charge Breeder since 2000. The performances have been improved over time acting on the 1+ and N+ beam optics, the base vacuum and the 1+ beam injection. A new objective is to update the booster design to enhance high charge state production and 1+ N+ efficiencies, reduce the co-extracted background beam and improve the ion source tunability. The first step, consisting in increasing the peak magnetic field at injection from 1.2 T to 1.6 T was implemented and significant improvement in 1+N+ efficiencies are reported: 12.9% of 23Na8+, 24.2% of 40Ar8+, 13.3% of 132Xe26+ and 13% of 133Cs26+. The next steps of the upgrade are presented: modification of the axial magnetic structure, significant increase of the plasma chamber radius (72 to 90 mm), plasma heating at 18 GHz (instead of 14 GHz), reduction of chemical elements composing the plasma chamber wall and the surrounding beam line

Recent improvements of the LPSC charge breeder

LPSC has developed the PHOENIX electron cyclotron resonance Charge Breeder since 2000. The performances have been improved over time acting on the 1+ and N+ beam optics, the base vacuum and the 1+ beam injection. A new objective is to update the booster design to enhance high charge state production and 1+ N+ efficiencies, reduce the co-extracted background beam and improve the ion source tunability. The first step, consisting in increasing the peak magnetic field at injection from 1.2 T to 1.6 T was implemented and significant improvement in 1+N+ efficiencies are reported: 12.9% of 23Na8+, 24.2% of 40Ar8+, 13.3% of 132Xe26+ and 13% of 133Cs26+. The next steps of the upgrade are presented: modification of the axial magnetic structure, significant increase of the plasma chamber radius (72 to 90 mm), plasma heating at 18 GHz (instead of 14 GHz), reduction of chemical elements composing the plasma chamber wall and the surrounding beam line.peerReviewe

[Kaart van het zuidelijk deel van Holland]

Deze fraaie kaart van Zuid-Holland is in de voorliggende vorm tamelijk uniek. De kaart bestaat namelijk uit 44 kaartbladen en 5 lege 'opvul'bladen, die op linnen zijn geplakt en aldus gevouwen in een foedraal eenvoudig op te bergen was. Het is daarmee als het ware een kleine wandkaart geworden. Oorspronkelijk zijn de deelkaarten echter bedoeld om opgenomen te worden in een atlas. Deze atlas werd rond 1740 vermoedelijk eerst gepubliceerd door Jacob Keizer te Almelo. Diens impressum is nog vaag zichtbaar in de cartouche linksonder: 'tot Almeloo by Jacobus Keizer'. De atlas werd vanaf circa 1750 opnieuw uitgegeven door de firma Ottens onder de titel: 'Nieuwe en zeer nette atlas van Zuyd-Holland, 't Sticht van Utrecht, en een gedeelte van Gelderland [...] t'Amsterdam, by Reinier en Josua Ottens [...]'. Dezelfde firma bracht na 1765 een ongewijzigde editie uit, nu met het impressum van de weduwe van Josua Ottens en Zoon. Nog weer later, aan het einde van de 18de eeuw, publiceerde Petrus Schenk III een editie van de atlas. De koperplaten kwamen tenslotte rond de eeuwwisseling in handen van de bekende firma Covens & Mortier, die de atlas tot 1828 in het fonds had. In dat jaar verruilden de koperplaten weer van eigenaar, maar een editie van na die tijd is niet bekend. Mogelijk zijn de koperplaten toen omgesmolten. De hier afgebeelde kaart is smaakvol ingekleurd, waarbij de Zuid-Hollandse regio's een vlakcoloriet hebben gekregen. Opvallend zijn de gebieden en lijnstructuren met een blauwe kleur (in Brabant, langs de Oude Hollandse Waterlinie en door de Gelderse Vallei); waarschijnlijk worden hiermee geïnundeerde of te inunderen gebieden en inundatiegrenzen aangeduid. In het Hollands veenweidegebied vestigt de kaart volop de aandacht op de toenmalige verveningsactiviteiten

Operation of the PHOENIX V3 ECRIS Applying Double Frequency Heating

International audiencePHOENIX V3 is an upgraded version of the V2 ECRIS to be installed at the heavy ion injector at SPIRAL2. The source is under commissioning at LPSC since 2016. One of the main upgrades of the V3 concerns the new microwave injection system including two WR62 waveguide apertures. This new plug having two waveguide ports allows running the ECRIS with the double frequency heating mode by connecting two different high power microwave sources. For the investigation of this plasma feeding method a klystron generator at 18 GHz proving up to 2 kW microwave power was used together with a traveling wave tube amplifier with a 12.75-14.5 GHz bandwidth and 650 W maximum output power. Several experiments were carried out in order to verify the performance with respect to the single frequency operation. Different ion source configurations were investigated and different frequencies and power combinations were analyzed with the aim to maximize the high charge state ion production and to reduce the ion beam instability. The results are reported here