Methanol–Water System for Solvothermal Synthesis of YVO4:Eu with High Photoluminescent Intensity

A methanol–water mixed solvent was used as a reaction medium for the preparation of Eu³⁺-doped YVO₄ phosphor materials. These were synthesized by a solvothermal method at 150°–300°C using a 10 vol% solution of water in methanol as the reaction medium followed by calcination at 1000°–1200°C. The phase composition and optical properties of the products were characterized by X-ray diffraction, scanning electron microscope, and photoluminescence spectroscopy. The powders obtained were composed of spherical particles ∼0.5 μm in size, with an internal structure that was different for samples prepared under subcritical and supercritical conditions of methanol. After the calcination, the powders obtained at 240°–300°C retained the initial raspberry-like morphology, whereas the morphology of samples prepared at 150°–210°C changed significantly due to noticeable sintering. The fluorescence intensity exhibited by the prepared samples was higher than the fluorescence intensity shown by one of the best commercial YVO₄:Eu phosphors having a large particle size.     

Effect of amylose/amylopectin content,milling methods,particle size,sugar, salt and oil on the puffed product characteristics of a traditional thai rice-based snack food (Khao Kriap Waue)

Factors affecting the quality of Khao Kriap Waue (KKW)-a traditional Thai glutinous-rice-based puffed-snack were studied. The moisture content and expansion ratio of KKW were positively correlated to amylopectin and negatively correlated to the amylose content of the flour, while hardness and bulk density were negatively correlated to amylopectin and positively correlated to amylose. Wet-milled flour produced good-quality puffed KKW, unlike dry milled flour. The smaller the flour particle size the better the product quality The addition of sugar and salt helped improve puffed product quality. The optimum amounts of added sugar and salt were 200–300 g and 0–20 g per kg of flour, respectively. Adding oil did not improve the processing and puffed product quality of KKW.     

A comparison of flow characteristics of refrigerants flowing through adiabatic straight and helical capillary tubes

This paper presents a numerical investigation of the flow characteristics of helical capillary tubes compared with straight capillary tubes. The homogenous two-phase flow model developed is based on the conservation of mass, energy, and momentum of the fluids in the capillary tube. This model is validated by comparing it with the experimental data of both straight and helical capillary tubes. Comparisons of the predicted results between the straight and helical capillary tubes are presented, together with the experimental results for straight capillary tubes obtained by previous researchers. The results show that the refrigerant flowing through the straight capillary tube provides a slightly lower pressure drop than that in the helical capillary tube, which resulted in a total tube length that was longer by about 20%. In addition, for the same tube length, the mass flow rate in the helical capillary tube with a coil diameter of 40 mm is 9% less than that in the straight tube. Finally, the results obtained from the present model show reasonable agreement with the experimental data of helical capillary tubes and can also be applied to predict the flow characteristics of straight capillary tubes by changing to straight tube friction factors, for which Churchill's equation was used in the present study.     

New proposed two-phase multiplier and evaporation heat transfer coefficient correlations for R134a flowing at low mass flux in a multiport minichannel

New correlations of the two-phase multiplier and heat transfer coefficient of R134a during evaporation in a multiport minichannel at low mass flux are proposed. The experimental results were obtained from a test using a counter-flow tube-in-tube heat exchanger with refrigerant flowing in the inner tube and hot water in the gap between the outer and inner tubes. Test section is composed of the extruded multiport aluminium inner tube with an internal hydraulic diameter of 1.2 mm and an acrylic outer tube with an internal hydraulic diameter of 25.4 mm. The experiments were performed at heat fluxes between 10 and 35 kW/m², and a refrigerant mass flux between 45 and 155 kg/(m² s). Some physical parameters that influenced the frictional pressure drop and heat transfer coefficient are examined and discussed in detail. The pressure drop and heat transfer coefficient results are also compared with existing correlations. Finally, new correlations for predicting the frictional pressure drop and heat transfer coefficient at low mass fluxes are proposed.     

Nucleate pool boiling heat transfer of TiO2–R141b nanofluids

Nucleate pool boiling heat transfer of a refrigerant-based-nanofluid was investigated at different nanoparticle concentrations and pressures. TiO₂ nanoparticles were mixed with the refrigerant HCFC 141b at 0.01, 0.03 and 0.05 vol%. The experiment was performed using a cylindrical copper tube as a boiling surface. Pool boiling experiments of nanofluid were conducted and compared with that of the base refrigerant. The results indicate that the nucleate pool boiling heat transfer deteriorated with increasing particle concentrations, especially at high heat fluxes. At 0.05 vol%, the boiling heat transfer curves were suppressed. At high pressures of 400 and 500 kPa, the boiling heat transfer coefficient at a specific excess temperature was almost the same.     

Optimization of extraction parameters for quantification of fermentation volatile by‐products in industrial ethanol with solid‐phase microextraction and gas chromatography

The rapid growth of the biofuels industry resulted in new research needs in chemical analysis. Methods for screening and quantification of impurities resulting from changes in feedstock, process and purification are needed. Direct sample injection methods are often not sensitive for lower concentrations. This research, developed an analytical method to simultaneously quantify fermentation volatile by‐products in industrial corn‐based ethanol. These include acetaldehyde, ethyl vinyl ether, 1,1‐diethoxyethane, isoamyl alcohol, isoamyl acetate, styrene, 2‐pentylfuran, ethyl hexanoate, ethyl octanoate, and ethyl decanoate. Headspace solid‐phase microextraction (SPME) coupled with gas chromatography–mass spectrometry (GC–MS) and GC‐FID were used. The effects of SPME coating, concentration, time, and salting out were tested. The optimized method used Carboxen/PDMS 85 µm coating with 10% (v/v) ethanol, 20 s headspace extraction, and no salt addition. The method had values of R² between 0.93 and >0.99 and relative standard deviations between 0.10 and 11.96%. The method detection limits were between 9.5 × 10^?4 to 9.7 × 10^?8 mol/L.This is one of the most comprehensive quantification methods for volatile impurities in raw ethanol to date. This new method was used to quantify 10 prevalent impurities in corn‐based industrial ethanol. Copyright © 2015 The Institute of Brewing & Distilling     

A simulation for predicting the refrigerant flow characteristics including metastable region in adiabatic capillary tubes

Assumptions that no metastable flow phenomenon and flow in two-phase region is homogeneous have been used exclusively to study the flow characteristics in capillary tubes used as an expansion and controlling device in refrigerating systems. However, some experimental results show that due to the delay of vapourization, the onset of vapourization may not take place at the end of the sub-cooled liquid region. The two-phase flow in small diameter tubes may be also not entirely homogeneous due to phase interaction. In this paper, a mathematical model based on conservations of mass, energy and momentum is presented to simulate the refrigerant flow in adiabatic capillary tubes. Different from most previous studies, the metastable flow region is accounted in the model and the annular flow is also assumed to take place in the two-phase region. The model is validated by comparing with the experimental data reported in literature. The agreement between experimental and simulation results indicates that the model with appropriate correlations of pressure at vapourization and slip ratio can be used to predict the two-phase flow behaviour of refrigerant in capillary tubes. Copyright © 2002 John Wiley & Sons, Ltd.     

Correlations for sizing adiabatic capillary tubes

This paper presents new correlations for the practical sizing of adiabatic capillary tubes used as an expansion device in small refrigerating and air-conditioning systems. The governing equation based on conservation of mass, energy and momentum is modelled. The developed model is used as an effective tool for studying the effects of relevant parameters on capillary tube length and developing the correlation. In this model, Colebrook's equation is used to determine the friction factor. The two-phase viscosity models are varied depending on the type of refrigerant and are based on the recommendations from past research. By varying the model input parameters, it is possible to show that for all refrigerants, the length decreases as the mass flow rate increases, increases as subcooling increases, increases as tube diameter increases, decreases as tube roughness increases and increases as condensing temperature increases. After the developed model is validated by comparing with existing experimental data, correlations for sizing capillary tubes, which contains the relevant parameters, namely condensing temperature, degree of subcooling, refrigerant mass flow rate, capillary tube inner diameter and roughness, are presented. Different from previous studies, correlations are presented for an extensive number of refrigerants and a wide range of operations. The developed correlations are validated with previous studies and found to agree well with the experimental data. The correlations can be used to integrate with system models working with alternative refrigerants for practical design and optimization. Copyright © 2003 John Wiley & Sons, Ltd.     

A neural predictive model for characterising impact cushioning curves

This paper describes a predictive characterisation model for impact cushioning curves. The model involves establishing an appropriate set of random discrete experimental points, network training and curve characterisation. Preliminary tests have found that the approach is able to predict quite accurately the impact cushioning curve characteristics to within ±2% error. The results achieved indicate that this approach can substantially reduce the number of experimental points required when characterising new impact cushioning materials. The algorithms used to obtain a set of randomly distributed training data and generate the requisite points for curve characterisation are also discussed and found to be suitable for this purpose.