Heat Transfer in Coiled Square Tubes for Laminar Flow of Slurry of Microencapsulated Phase Change Material

Passive heat transfer enhancement using a slurry of microencapsulated phase-change material (MEPCM) flowing in a laminar regime through a coiled duct of square cross section was evaluated. The phase-change material is n-octadecane. The flow behavior and heat transfer performance of water and MEPCM suspensions in various configurations (conical spiral, in-plane spiral, and helical spiral) of coiled tubes of square cross section was investigated. The results are compared with those for water as the base fluid flowing through a straight tube. A computational fluid dynamics (CFD) approach is used to simulate the laminar flow of water with MEPCM suspension in these geometries. The liquid suspension properties are expressed as functions of the volumetric concentration of MEPCM particles and the temperature. Improved heat transfer performance was obtained as the concentration of MEPCM suspension increased from 1 to 10%. However, the overall performance in terms of the pumping power consumed for unit heat transferred worsened.     

AC-driven,color- and brightness-tunable organic light-emitting diodes constructed from an electron only device

In this paper, a color- and brightness-tunable organic light-emitting diode (OLED) is reported. This OLED was realized by inserting a charge generation layer into an electron only device to form an n-i-p-i-n structure. It is shown that, by changing the polarity of applied voltage, only the p-i-n junction operated under positive bias can emit light and, by applying an AC voltage, emission from both junctions was realized. It is also shown that, by using a combination of blue- and red-emiting layers in two p-i-n junctions, both the color and brightness of the resulting white OLED can be tuned independently by changing the positive and negative amplitudes of the AC voltage.     

Polymerization of polyaniline under various concentrations of ammonium peroxydisulfate and hydrochloric acid by ultrasonic irradiation

Effects of various molar ratios of monomer (aniline), oxidant (ammonium peroxydisulfate), and dopant (hydrochloric acid) on the polymerization of polyaniline (PANI) were investigated using direct ultrasonic irradiation technique. The effects of varying molar ratio of dopant and oxidant on the structural stability, morphology, and electrical conductivity of the prepared PANI were studied. Firstly, a scheme derived from electrical conductivity point of view, by varying the molar ratio of ammonium peroxydisulfate (APS). As the molar ratio of APS to aniline (ANI) varied from 0.1 to 1.25, the conductivity of PANI reached a maximum of 0.24 S/cm at a ratio of 1. Thereafter, by fixing the optimized molar ratio of APS and aniline the molar ratio of hydrochloric acid (HCl) was varied. The conductivity of PANI increased with an increase of HCl concentration and reached a maximum of 0.5 S/cm at an HCl concentration of 2 M. Finally, the formation mechanism for polymerization of PANI were discussed using Fourier transform infrared spectra, ultraviolet–visible spectra, nuclear magnetic resonance spectroscopy, and X-ray diffraction spectroscopy. The final product is in protonated form, possessing structural stability and electrically conductive.     

Effect of octa(aminopropyl) polyhedral oligomeric silsesquioxane (OapPOSS) functionalized graphene oxide on the mechanical,thermal, and hydrophobic properties of waterborne polyurethane composites

A novel graphene nanomaterial functionalized by octa(aminopropyl) polyhedral oligomeric silsesquioxane (OapPOSS) was synthesized and then confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), Raman spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM EDX), atomic force microscopy, and X‐ray diffraction. The obtained functionalized graphene (OapPOSS‐GO) was used to reinforce waterborne polyurethane (WPU) to obtain OapPOSS‐GO/WPU nanocomposites by in situ polymerization. The thermal, mechanical, and hydrophobic properties of nanocomposites as well as the dispersion behavior of OapPOSS‐GO in the polymer were investigated by TGA, a tensile testing machine, water contact angle tests, and field emission SEM, respectively. Compared with GO/WPU and OapPOSS/WPU composites, the strong interfacial interaction between OapPOSS‐GO and the WPU matrix facilitates a much better dispersion and load transfer from the WPU matrix to the OapPOSS‐GO. It was found that the tensile strength of the OapPOSS‐GO/WPU composite film with 0.20 wt % OapPOSS‐GO exhibited a 2.5‐fold increase in tensile strength, compared with neat WPU. Better thermal stability and hydrophobicity of nanocomposites were also achieved by the addition of OapPOSS‐GO. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44440.     

Energy and exergy analysis of kalina cycle system (KCS) 34 with mass fraction ammonia-water mixture variation

Further utilization of waste heat produced by power plant system will increase the efficiency of the whole power plant system. The Kalina Cycle offers alternative solution to generate additional power from waste heat or from low temperature geothermal resources. The modeling application on energy system is used to study the basic design of thermal system, which uses Kalina Cycle for further utilization of geothermal brine water. If this geothermal brine water were not used in the Kalina Cycle, it would be reinjected to the geothermal reservoir and its remaining energy content would have been wasted. The study of this process is done by Cycle Tempo 5.0 simulation software, to obtain the data of efficiency, energy and exergy that could be generated from the heat source. An ammonia-water mixture is used as a working fluid on Kalina cycle system (KCS) 34. In order to obtain the maximum power output and maximum efficiency, the system will be optimized on the mass fraction of working fluid and also on the turbine output pressure. The result of the study shows that the maximum efficiency and power output are achieved at 78% ammonia-water mixture. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Nasruddin is a faculty member of Mechanical Engineering Department University of Indonesia. He received his Bachelor degree from the same university. He then obtained Master of Engineering (MEng.) from K.U. Leuven (Belgium). He received Doktor der Ingenieurwissenschaften (Dr.-Ing.) from RWTH Aachen University (Germany) in 2005. He has more than 13 years of experiences in lecture and research in engineering thermodynamics. He is a member of ASHRAE. Rama Usvika received his Engineer degree in Mechanical Engineering from the University of Indonesia in 1996. He then obtained MSc degree in Energy and Environmental Engineering from Ecole des Mines de Nantes (France) in 2005. Mr. Rama currently serves as Engineering Manager for Power Generation projects at PT. Rekayasa Industri, Indonesia’s premier Engineering & Construction company. He has more than 12 years of experiences in engineering, procurement, construction and commissioning of In-dustrial Process and Power plants. He is a member of ASME, the author and co-author of several papers on Power and Energy topics.     

Economic production quantity model for deteriorating inventory with random machine unavailability and shortage

Both random machine unavailability and shortage are common occurrences in manufacturing industries. In this paper, machine unavailability is considered in deriving an economic production quantity (EPQ) model for deteriorating items. We develop four EPQ models for deteriorating inventory with random machine unavailability and shortage. The study considers lost sales, backorder and two kinds of machine unavailability distributions. Numerical examples are provided to illustrate the theory. Key parameter changes that affect costs are shown in the sensitivity analysis. From the results of the sensitivity analysis, it is shown that the random machine unavailability parameter and holding cost have significant effects on the optimal total cost and production down-time.     

Integration of promotion and production decisions in sales and operations planning

This paper presents a new modelling framework for developing a sales and operations plan that integrates promotion and production planning decisions. We adopt a rich demand function that captures the dynamics and heterogeneity of consumer response to price promotions by simulating purchase incidence, consumer choice and quantity decisions, as well as household’s inventory level. Our numerical study reveals interesting findings on the benefits of developing an integrated sales and operations plan as well as the optimal timing and number of promotions, and more importantly, how these findings are influenced by the mutual dependence of marketing- and production-related factors.     

A facile method for production of high-purity silica xerogels from bagasse ash

In this paper, we systematically report the synthesis of mesoporous silica xerogels in high purity from bagasse ash. The bagasse ash was chosen as the raw material due to its availability and low-price, and environmental considerations also were important. Silica was extracted as sodium silicate from bagasse ash using NaOH solution. The sodium silicate was then reacted with HCl to produce silica gel. To produce high-purity silica xerogels, three different purification methods were investigated, i.e., acid treatment, ion exchange treatment, and washing with de-mineralized water. We were able to produce high-purity silica (>99 wt.%) by washing the produced gels with either de-mineralized water or with ion exchange resin. The specific surface area of the prepared silica xerogels ranged from 69 to 152 m² g^?1 and the pore volume ranged from 0.059 to 0.137 cm³ g^?1. The pore radii were 3.2–3.4 nm, which indicated that the silica xerogels was mesoporous. From the adsorption characterization, it was obvious that adsorptive capacity was better for high-purity silica xerogels compared with low-purity. The maximum adsorption capacity by high-purity silica xerogel was 0.18 g-H₂O/g-SiO₂. Finally, we demonstrate the potential of bagasse ash for mesoporous silica production with its excellent adsorptive capacity that makes it beneficial as an environmental solution.