Thermal performance enhancement of shell and helical coil heat exchanger using MWCNTs/water nanofluid

Journal of Thermal Analysis and Calorimetry - Heat exchangers serve as pivotal components in industries. Enhancement in the performance of heat exchangers has been the focus of researchers in the...     

Heating performance enhancement for a road unit by using sectorial-finned pipe

Journal of Thermal Analysis and Calorimetry - This study proposes a sectorial-finned pipe in the hydronic road heating system with a three-dimensional road model to enhance the road heating...     

Correction to: Thermal performance enhancement of shell and helical coil heat exchanger using MWCNTs/water nanofluid

Journal of Thermal Analysis and Calorimetry -     

Design and performance of a miniature TDCR counting system

A portable liquid scintillation counting system based on the triple-to-double coincidence ratio (TDCR) method was developed at Sofia University “St. Kliment Ohridski”. The system consists of a miniature TDCR counter with cylindrical optical chamber and a specialized TDCR counting module named nanoTDCR. The nanoTDCR module is produced by the labZY company and provides several important new TDCR counting functionalities like: individual extending-type dead-time in each channel; simultaneous counting with two different extendable dead-times and two different coincidence windows and simultaneous TDCR counting and spectrum acquisition. The performance of the new system was tested in benchmark comparisons with the LNHB’s primary TDCR counting system of activity measurements of ²⁴¹Am, ³H, ¹⁴C and ⁶³Ni. Good agreement between the two systems was observed.     

Thermal performance enhancement of solar air collector using a novel V-groove absorber plate with pin-fins for drying agricultural products: an experimental study

Journal of Thermal Analysis and Calorimetry - An experimental investigation of a novel V-groove absorber plate with pin-fins on double-pass solar air collector was made to study the enhancement of...     

Investigation of performance enhancement of flame photometric signal using a cylindrical impactor in the spray chamber

The effect of a cylindrical impactor in the spray chamber of a flame photometer on the characteristics of the aerosol formed, on the transport-efficiency of the nebulizer-spray chamber system, as well as on the analytical signal has been investigated. The variables were: the diameter Phi of the cylindrical impactor and its position, i.e., the distance d in front of the tip of pneumatic nebulizer capillary where the impactor was fixed. The performance characteristics of an 1 mm Phi impactor was fixed at d=5 mm was superior to that of a conventional 8 mm Phi spherical bead.     

Microchip isoelectric focusing using a miniature scanning detection system

A miniature scanning fluorescent detector has been developed for plastic microchannel isoelectric focusing (mIEF) analysis. The detector, comprised of a lamp and photomultiplier tube (PMT) on a moving stage, measured the real-time distribution of fluorescently labeled peptides subjected to gel-free mIEF. During the run, the effective length of the 6-cm channel was scanned every 9 s. Analysis was completed within 5 min while still obtaining high resolution and sensitivity. In addition, the scanning detector was used to characterize peptide migration properties within the channel by providing simultaneous temporal and spatial measurements.     

Experimental performance analysis of two different passive cooling techniques for solar photovoltaic installations

Journal of Thermal Analysis and Calorimetry - At higher ambient temperatures during summer months, the cell temperature of a photovoltaic (PV) module increases to 50–60 °C and sometimes...     

Green synthesis of banana flavor using different catalysts: a comparative study of different methods

ABSTRACT

Esterification of isoamyl alcohol with acetic acid was studied using different ion-exchange resins, namely Amberlyst 15 dry, Amberlyst 16 wet, Amberlite 120-IR. Esterification was carried out using different esterification methods that are quite new (ohmic, ultrasonic probe, and ultrasonic bath) and the results were compared with microwave-assisted esterification (MAE). The highest isoamyl acetate yield (99%) was obtained by MAE, using a mixture of acetic acid and isoamyl alcohol (mole ratio of 1:2) after 2?h of reaction time. In this process, 2% Amberlyst 15 dry was used. MAE had the least specific energy consumption (0.42?kWh/g isoamyl acetate) and specific CO₂ emission (34?g/g isoamyl acetate). According to the images obtained by scanning electron microscopy, lower amounts of Amberlyst 15 dry beads were destroyed by MAE method compared to other esterification methods. In conclusion, MAE proved to be an economic and environmentally-friendly method for esterification of different flavoring compounds.     

Practical polymer film characterisation using high performance XPS methods

Summary New features of laboratory XPS instrument design have resulted in large increases in sensitivity for microprobe style analysis (spatially keyed spectroscopy). These capabilities give access to XPS valence band and other high resolution information for polymer analysis on a routine basis. Examples of the practical use of these techniques are presented.     

Photovoltaic performance enhancement using fluorene‐based copolymers containing pyrene units

A set of novel conjugated polyfluorene co‐ polymers, poly[(9,9′‐didecylfluorene‐2,7‐diyl)‐co‐(4,7′‐di‐2‐thienyl‐ 2′,1′,3′‐benzothiadiazole‐5,5‐diyl)‐co‐(pyrene‐1,6‐diyl)], are synthesized via Pd(II)‐mediated polymerization from 2,7‐bis(4′,4′,5′, 5′‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9′‐di‐n‐decylfluorene, 4, 7‐di(2‐bromothien‐5‐yl)‐2,1,3‐benzothiadiazole, and 1,6‐dibromopyrene with a variety of monomer molar ratios. The field‐effect carrier mobilities and optical, electrochemical, and photovoltaic properties of the copolymers are systematically investigated. The hole mobilities of the copolymers are found to be in the range 7.0 × 10^?5 ? 8.0 × 10^?4 cm² V^?1 s^?1 and the on/off ratios were 8 × 10³ ? 7 × 10⁴. Conventional polymer solar cells (PSCs) with the configuration ITO/PEDOT:PSS/polymer:PC₇₁BM/LiF/Al are fabricated. Under optimized conditions, the polymers display power conversion efficiencies (PCEs) for the PSCs in the range 1.99–3.37% under AM 1.5 illumination (100 mW cm^?2). Among the four copolymers, P2, containing a 2.5 mol % pyrene component incorporated into poly[9,9′‐didecylfluorene‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PFDTBT) displays a PCE of 3.37% with a short circuit current of 9.15 mA cm^?2, an open circuit voltage of 0.86 V, and a fill factor of 0.43, under AM 1.5 illumination (100 mW cm^?2). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Study of ion adsorption at passive iron by using the impedance and photoadmittance methods

Intensity-modulated photocurrent (photoadmittance) and electrochemical impedance of anodicoxidized iron electrode in neutral nitrate solutions and in the presence of Ba²⁺, Ca²⁺, Cl^?, and C₆H₅COO^? (benzoate) are studied. It is shown that the ion adsorption at passive iron affects but slightly the system’s impedance; by contrast, it affects the photocurrent value significantly: when adsorbing, the anions increase the photoeffect, while the cations decrease it. These effects are associated with the potential drop redistribution in the Helmholtz layer and the film. The dissimilar changes of the generation current in the presence of similarly charged ions at their equal concentration evidence their different adsorption activity. The correlation between the generation current and surface-active ion concentration in solution is found. The photoelectrochemical spectroscopy allows evaluating qualitatively the surface-active ion adsorption at the passive iron and judging on the ion adsorption by the dependence of the generation current on the ion concentration.     

SCR performance enhancement of NiMnTi mixed oxides catalysts by regulating assembling methods of LDHs-Based precursor

A series of NiMnTi mixed metal oxides (Ni/Mn-TiO₂, Mn/NiTi-LDO and TiO₂/NiMn-LDO, NiMnTi-LDO) were synthesized via different assembling methods and evaluated in the selective catalytic reduction of NO_x with NH₃(NH₃-SCR). As the results presented, catalysts via diverse assembling methods of LDHs templates afforded different catalytic denitrification (DeNO_x) performance, which might be related to the exposure degree of active constituents and the interaction intensity between metal components. Noticeably, compared with Ni/Mn-TiO₂, Mn/NiTi-LDO and TiO₂/NiMn-LDO catalysts, the NiMnTi-LDO catalyst deriving from one step in-situ method NiMnTi-LDH precursor template exhibited the most desirable performance at temperature window of 150–360 °C in NH₃-SCR (above 90% NO_x conversion with 95% N₂ selectivity). The specific structure and property of samples were correlated by means of a series of characterizations, where the results indicated that NiMnTi-LDO possessed the highest surface area, the strongest redox ability, the most abundant acid amount and the best dispersion.     

In vitro dissolution of uranyl acetate using different methods

The dissolution rate of a material in the lung is an important parameter in evaluating the risk to humans following accidental inhalation of a substance and is also a parameter that may be useful in characterizing particles for nuclear forensics analysis. Conventional methods of measuring dissolution rates in vitro involve exposing the material or particles to a solvent, such as water, saline, or solutions that simulate lung fluid, and measuring the fraction of material that dissolves with time. A new device for measuring dissolution rates for small samples, especially individual particles, was evaluated that incorporates a regenerated cellulose dialysis membrane fixed to the bottom of a small, 2 mL plastic cup that fits into the top of a 50 mL plastic centrifuge tube. The cup is easily transferred among a series of tubes containing solvent to measure rate of dissolution. The dialysis membrane has a diffusion rating of 20 kDa molecular weight cut off which greatly exceeds the size of the dissolved uranium molecule. The performance of the dialysis cup device was evaluated by measuring the dissolution rate of uranyl acetate in distilled water, phosphate buffered saline (PBS), and simulated lung fluid (SLF). These results were compared to the dissolution rate measured using the traditional filter sandwich method in which a sample is sealed between two hydrophilic membranes. Although the majority of uranyl acetate dissolved in SLF within 30 min using the filter sandwich method, most of the uranyl acetate was undissolved in PBS and SLF using the dialysis membrane device. Reactions between the dissolved uranyl acetate, solvent, and the dialysis membrane likely caused the membrane to swell, shrinking the pore size, and thus reducing the transport of dissolved uranium across the membrane. Use of the dialysis cup device for evaluating dissolution rates for uranium-bearing materials in solvents containing a high concentration of salts is therefore not recommended.     

Rapid hydrocarbon analysis using a miniature rectilinear ion trap mass spectrometer

A miniature ion trap mass analyzer was applied to the analysis of traces of hydrocarbons and simple heteroatomics in the vapor phase and in aqueous solution. Vapors of acetone, acetic acid, acetonitrile, benzene, butanethiol, carbon disulfide, hexane, dichloromethane, naphthalene, toluene and xylenes were detected and quantified using solid sorbent trapping and, in some cases, by passage through a membrane interface. Aqueous solutions of benzene, toluene, xylenes, hexane and a petroleum naphtha distillate were examined using the membrane interface. Sampling, detection and identification of all compounds was completed in times of less than one minute. The gas-phase samples of toluene and benzene were detected at 200 ppt (limit of detection, LOD) for toluene and 600 ppt for benzene. Identification of benzene and xylene in aqueous solutions was readily achieved with LODs of 200 and 400 ppb, respectively. Quantification over a linear dynamic range of two orders of magnitude for the aqueous samples and three orders of magnitude for the vapor-phase samples was demonstrated.     

Exploring the potential energy surface of retinal, a comparison of the performance of different methods

The ground state structure of retinal has been investigated. We found that DFT and CASSCF produce different results for the bond length alternation in a model system of retinal. Quantum mechanics/molecular mechanics calculations including the closest surrounding amino acids have been performed, using DFT and CASSCF to calculate the structure of retinal in the protein cavity. The planarity of the retinal molecule is affected by the surrounding protein. DFT and CASSCF produce different twist angles. The difference between CASSCF and DFT appears to be related to the positively charged nitrogen of the Schiff base, which leads to different pi-bond orders produced by the two methods.     

Comparison of different methods for calculating the paramagnetic relaxation enhancement of nuclear spins as a function of the magnetic field

The enhancement of the spin-lattice relaxation rate for nuclear spins in a ligand bound to a paramagnetic metal ion [known as the paramagnetic relaxation enhancement (PRE)] arises primarily through the dipole-dipole (DD) interaction between the nuclear spins and the electron spins. In solution, the DD interaction is modulated mostly by reorientation of the nuclear spin-electron spin axis and by electron spin relaxation. Calculations of the PRE are in general complicated, mainly because the electron spin interacts so strongly with the other degrees of freedom that its relaxation cannot be described by second-order perturbation theory or the Redfield theory. Three approaches to resolve this problem exist in the literature: The so-called slow-motion theory, originating from Swedish groups [Benetis et al., Mol. Phys. 48, 329 (1983); Kowalewski et al., Adv. Inorg. Chem. 57, (2005); Larsson et al., J. Chem. Phys. 101, 1116 (1994); T. Nilsson et al., J. Magn. Reson. 154, 269 (2002)] and two different methods based on simulations of the dynamics of electron spin in time domain, developed in Grenoble [Fries and Belorizky, J. Chem. Phys. 126, 204503 (2007); Rast et al., ibid. 115, 7554 (2001)] and Ann Arbor [Abernathy and Sharp, J. Chem. Phys. 106, 9032 (1997); Schaefle and Sharp, ibid. 121, 5387 (2004); Schaefle and Sharp, J. Magn. Reson. 176, 160 (2005)], respectively. In this paper, we report a numerical comparison of the three methods for a large variety of parameter sets, meant to correspond to large and small complexes of gadolinium(III) and of nickel(II). It is found that the agreement between the Swedish and the Grenoble approaches is very good for practically all parameter sets, while the predictions of the Ann Arbor model are similar in a number of the calculations but deviate significantly in others, reflecting in part differences in the treatment of electron spin relaxation. The origins of the discrepancies are discussed briefly.     

Characterization of depleted uranium oxides fabricated using different processing methods

Identifying both physical and chemical characteristics of Special Nuclear Material (SNM) production processes is the corner stone of nuclear forensics. Typically, processing markers are based on measuring an interdicted sample’s bulk chemical properties, such as the elemental or isotopic composition, or focusing on the chemical and physical morphology of only a few particles. Therefore, it is imperative that known SNM processes be fully characterized from bulk to trace level for each particle size range. This report outlines a series of particle size measurements and fractionation techniques that can be applied to a bulk SNM powders, categorizing both chemical and physical properties in discrete particle size fractions. This will be demonstrated by characterizing the process signatures of a series of different depleted uranium oxides prepared at increasing firing temperatures (350–1100 °C). Results will demonstrate how each oxides’ material density, particle size distribution, and morphology varies.     

Flow-through determination of sulphate in water using different methods: A comparison

Summary Sulphate was determined in various kinds of environmental samples using a continuous-flow system, a flow-injection system or a flow-through titrimeter. The reagents in the three cases consisted basically of DMSA(III), KNO₃ and Ba(ClO₄)₂. The results of the three methods were evaluated statistically. A comparison of the three methods is given. The advantage of the DSMA(III)-methods is shown in a comparison with the commonly used thorin method.

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Sulfatbestimmung in Wasser mit verschiedenen Methoden in einem Durchflußsystem; ein Vergleich

Zusammenfassung Die Bestimmung von Sulfat in unterschiedlichen Umweltwasserproben wurde mit drei verschiedenen Systemen vorgenommen: mit continuous-flow und flow-injection Durchflußsystemen und mit einem Durchflußtitrimeter. Die Reagentien bei den drei Bestimmungen waren DMSA(III), KNO₃ und Ba(ClO₄)₂. Die Ergebnisse wurden statistisch ausgewertet und die Methoden miteinander verglichen. Die DMSA(III)-Verfahren sind der weit verbreiteten Thorin-Methode vorzuziehen.

     

Investigation of the regeneration of the passive surface oxide layer of TiAl6V4 alloy printed by WAAM technology using different electrochemical test methods

The kinetics of oxide layer formation on surface of Ti6Al4V alloy samples is a very important property especially if their application as medical implants is planned. Damaged protective surface layer usually heals in ambient condition however; during the self-healing process toxic species can get into the surrounding living tissue. In our experiment the kinetics of the healing process proceeding at 3D printed alloy surface has been studied using electrochemical methods, among them scanning electrochemical microscopy. More than 40 min. time period was found long enough for total healing.