Two phase natural convection: CFD simulations and PIV measurement

Buoyancy induced flow and heat transfer are important phenomena in a wide range of engineering systems e.g. electronics and photovoltaics cooling, thermosiphon heat exchangers, solar-thermal heat absorbers, passive decay heat removal systems, etc. Such systems are subject to thermal stratification. The objective of the present work is to study the single phase and two phase (boiling) natural convection accompanied by thermal stratification. We carried out velocity and temperature measurements in a rectangular tank (0.8×0.6×0.6 m³) fitted with (a) a central tube, and (b) a 10 tube assembly; which form the heat transfer surface. Flows were measured using Particle Image Velocimetry (PIV). Additionally, computational fluid dynamic (CFD) simulations of these systems were performed: first with an assumption of no-boiling (i.e. no phase change) near the heat transfer surfaces; for which we used the open source CFD code OpenFOAM-1.6. For two phase simulations, we used the boiling model of Ganguli et al. (2010) and carried out simulations using the commercial software FLUENT 6.3. The extent of stratification and mixing has been investigated for a range of Rayleigh numbers from 4.34×10¹¹ to 2.59×10¹⁴. The flow information obtained from PIV was analyzed for insights into the dynamics of turbulent flow structures. We used the signal processing technique of discrete wavelet transform (DWT) for this purpose. From the analysis, we were able to estimate the size, velocity and energy distribution of turbulent structures in our flows. This information was used to estimate wall heat transfer coefficients. A good agreement was observed between the predicted and the experimental values of heat transfer coefficients.     

Microwave catalytic NOx and SO2 removal using FeCu/zeolite as catalyst

Non-thermal plasma technology is a promising process for flue gas treatment. Microwave catalytic NO_x and SO₂ removal simultaneously has been investigated using FeCu/zeolite as catalyst. The experimental results showed that a microwave reactor with FeCu/zeolite only could be used to microwave catalytic oxidative 91.7% NO_x to nitrates and 79.6% SO₂ to sulfate; the reaction efficiencies of microwave catalytic reduction of NO_x and SO₂ in a microwave reactor with FeCu/zeolite and ammonium bicarbonate (NH₄HCO₃) as a reducing agent could be up to 95.8% and 93.4% respectively. Microwave irradiation accentuates catalytic reduction of SO₂ and NO_x treatment, and microwave addition can increases SO₂ removal efficiency from 14.5% to 18.7%, and NO_x removal efficiency from 13.4% to 18.7%, separately. FeCu/zeolite catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectrum analysis (XPS), scanning electron microscopy (SEM) and the Brunauer Emmett Teller (BET) method. Microwave catalytic NO_x and SO₂ removal follows Langmuir-Hinshelwood (L-H) kinetics.     

Electrochemical investigation of Al–Li/Li<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>FePO<Subscript>4</Subscript> cells in oligo(ethylene glycol) dimethyl ether/LiPF<Subscript>6</Subscript>

1 M LiPF₆ dissolved in oligo(ethylene glycol) dimethyl ether with a molecular weight, 500 g mol⁻¹ (OEGDME500, 1 M LiPF₆), was investigated as an electrolyte in experimental Al–Li/LiFePO₄ cells. More than 60 cycles were achieved using this electrolyte in a Li-ion cell with an Al–Li alloy as an anode sandwiched between two Li _x FePO₄ electrodes (cathodes). Charging efficiencies of 96–100% and energy efficiencies of 86–89% were maintained during 60 cycles at low current densities. A theoretical investigation revealed that the specific energy can be increased up to 15% if conventional LiC₆ anodes are replaced by Al–Li alloy electrodes. The specific energy and the energy density were calculated as a function of the active mass per electrode surface (charge density). The results reveal that for a charge density of 4 mAh cm⁻² about 160 mWh g⁻¹ can be reached with Al–Li/LiFePO₄ batteries. Power limiting diffusion processes are discussed, and the power capability of Al–Li/LiFePO₄ cells was experimentally evaluated using conventional electrolytes.     

Dietary Inclusion of Tea Catechins Changes Fatty Acid Composition of Muscle in Goats

This study was conducted to examine dietary tea catechins (TC) supplementation on the fatty acid composition of muscle and ruminal bacteria in goats fed a maize stover-based diet. Forty goats, 8 months old (16.2 ± 1.2 kg), were randomly divided into four equal groups (10 animals in each group) and assigned to four experiment diets with TC supplementation at four levels (0, 2,000, 3,000 and 4,000 mg TC/kg feed, namely TC0, TC2000, TC3000 and TC4000, respectively). After a 60-day feeding period, all the goats were slaughtered and sampled. The results showed that dietary TC inclusion increased the average daily gain (ADG), protein content in the semimembranosus muscle and dry matter in the longissimus dorsi muscle (LD). Dietary TC supplementation increased the ratio of n-6 to n-3 fatty acid, the ratio of polyunsaturated fatty acids to saturated fatty acids was higher in TC3000 and TC4000 than in TC0 and TC2000 for LD. The current results implied that dietary inclusion of a suitable TC dose could improve the growth performance and increase the proportions of unsaturated fatty acids in muscle, and the biohydrogenation of ruminal microorganisms might change the profiles of fatty acids in the muscle of growing goats.     

Experimental investigation and material modelling of fresh and UV aged Japanese lacquer (Urushi)

Urushi is a complex natural polymer that has been used to protect and decorate objects for many hundreds of years. It is an important material as decorated objects can obtain great value and historical worth. These objects are often exposed to environments that are detrimental to both their aesthetic appeal and structural performance and restoration and conservation procedures are needed to preserve these objects over long periods of time. The conservation work requires a detailed understanding of the material properties of the Urushi lacquer film. However, Urushi exhibits complex viscoelastic behaviour under load that has not been fully characterised to date. This paper presents the sample preparation technique and experimental data from a comprehensive mechanical testing programme for Urushi film. The viscoelastic response was investigated by tests at various loading speeds and creep and recovery tests. A number of constitutive models were fitted to the creep and recovery data and a good fit was seen with a number of these, most notably a modified generalized Kelvin fluid (MGKF) model. Some samples of Urushi were artificially aged by laboratory exposure to ultraviolet (UV) irradiation before mechanical testing. The ageing increased strength and reduced the ductility of the Urushi and it was shown that the MGKF model was capable of modelling the ageing behaviour by using ageing-time dependent material parameters. The models were implemented in the commercial FEA software ABAQUS, offering the potential to accurately model the Urushi behaviour in a complex structure.     

DFT Calculation on polychlorinated phenarsazines: Their gas phase thermodynamic functions and the implications of Cl substituted position

The thermodynamic properties of 136 polychlorinated phenarsazines (PCPAZs) have been calculated by density functional theory at the B3LYP/6‐31G* level. Then, isodesmic reactions are designed to calculate Δ_fH° and Δ_fG° of PCPAZs. The relations of these thermodynamic parameters with the number and position of Cl atom substitution (N_PCS) are discussed and a relative stability order of PCPAZs is theoretically proposed according to the relative magnitude of their Δ_fG°. In addition, the values of molar heat capacities at constant pressure from 200 to 1000 K for PCPAZs are calculated, and the temperature dependence relations of this parameter are obtained using the least‐squares method.     

Wettability of porous two‐dimensional ZnO nanocrystal films

Large‐scale two‐dimensional ZnO nanocrystal films on aluminum substrate were fabricated by a one‐step hydrothermal method under mild conditions, where all the ZnO nanocrystals had a lamellar structure generally perpendicular to the substrates and formed network‐like porous configurations. The morphologies of the films were dependent on both the reaction temperature and concentration of zinc. The wettability of the ZnO films was assessed by measuring the water contact angle without any surface functionalisation. The porous structures of the as‐prepared films could effectively enhance its hydrophobicity and the water contact angle ranged from 40° to 135° depending on the surface morphology and the arrangement of ZnO planes, indicating a simple and promising route to make aluminum surface waterproof and even self‐cleaning. The hydrophobic ZnO surface could be switched to hydrophilic state by UV irradiation.     

Kinetics and Efficiency Analysis of Electrochemical Oxidation of Phenol: Influence of Anode Materials and Operational Conditions

The influence of operational parameters and anode materials on degradation kinetics, mineralization current efficiency, and energy consumption for electrochemical oxidation of phenol was studied. Phenol elimination follows pseudo‐first‐order kinetics in most cases except for the Ti/RuO₂ anode with a phenol concentration of 500 mg L^–1, where pseudo‐zero‐order kinetics is observed. The total organic carbon removal by a Ti/Sb‐SnO₂ anode follows pseudo‐first‐order kinetics in contrast to pseudo‐zero‐order kinetics by Pt and Ti/RuO₂ anodes. For a certain anode, a higher current or voltage input results in a higher reaction rate. With a Ti/Sb‐SnO₂ anode, the highest current efficiency and the lowest energy consumption are obtained, but the current efficiency decreases (increases for energy consumption) quickly as the reaction is prolonged due to the reduction of organics.     

Flow Characteristics of Gas Permeation through a PVF Porous Tube

PVF (polyvinyl formal) porous materials have attractive properties, such as noise attenuation, good structural integrity, thermal and chemical stability, high permeability and large specific surface area, for many flow‐through applications. Several characteristics of the porous material will have an impact on the permeability, and gas flow and diffusion. However, the shape and the design of the device may also have significant impact on the gas flow. A porous media model and Darcy‐Forchheimer principle were used as the basic theoretical frame. The unified governing equations were used to describe the compressible flow in and out of a PVF porous tube. A robust NND numerical scheme was used to discretize the equations and the TDBC (time‐dependent boundary conditions) were used to treat the nonreflective boundaries. Numerical simulations of an interior and exterior flow field of a PVF porous tube were completed. The detailed flow characteristics of the inner and outer flow fields of the tube were obtained. The velocity distribution of the outside of the tube compare very well with the experimental data.     

Aging and Thermal Stability of the Mixed Product of the Ether‐Soluble Fraction of Bio‐Oil and Bio‐Diesel

The storage and thermal stability of blends of the ether‐soluble fraction of bio‐oil (ES) and bio‐diesel are reported. Fuel properties such as viscosity, water content, acid number and average molecular weight of the ES/bio‐diesel blends were measured before and after aging. Compared to the aging properties of bio‐oil alone, very small changes in water content and viscosity were shown for the blends aged at 80 °C for 180 h. Chemical changes were characterized using gel permeation chromatography, showing a slight increase in the molecular weight over time. Further confirmation of the changes was provided through Fourier transform infrared spectrometry, thermal decomposition analysis using a thermogravimetric analyzer, proton assignment using proton nuclear magnetic resonance, and carbon assignment using carbon nuclear magnetic resonance. Overall, the study indicates that ES/bio‐diesel blends are stable as fuel under the conditions tested in this paper.