Abstract: In this paper, the exergy analysis of vapor absorption
refrigeration system using LiBr-H2O as working fluid is carried out
with the modified Gouy-Stodola approach rather than the classical
Gouy-Stodola equation and effect of varying input parameters is also
studied on the performance of the system. As the modified approach
uses the concept of effective temperature, the mathematical
expressions for effective temperature have been formulated and
calculated for each component of the system. Various constraints and
equations are used to develop program in EES to solve these
equations. The main aim of this analysis is to determine the
performance of the system and the components having major
irreversible loss. Results show that exergy destruction rate is
considerable in absorber and generator followed by evaporator and
condenser. There is an increase in exergy destruction in generator,
absorber and condenser and decrease in the evaporator by the
modified approach as compared to the conventional approach. The
value of exergy determined by the modified Gouy-Stodola equation
deviates maximum i.e. 26% in the generator as compared to the
exergy calculated by the classical Gouy-Stodola method.
Abstract: Silica was extracted from agriculture waste rice husk
ash (RHA) and was used as the silica source for synthesis of
RMCM-48 and RSBA-16. An alkali fusion process was utilized to
separate silicate supernatant and the sediment effectively. The
CTAB/Si and F127/Si molar ratio was employed to control the
structure properties of the obtained RMCM-48 and RSBA-16
materials. The N2 adsorption-desorption results showed the
micro-mesoporous RSBA-16 possessed high specific surface areas
(662-1001 m2/g). All the obtained RSBA-16 materials were applied as
the adsorbents for acetone adsorption. And the breakthrough tests
clearly revealed that the RSBA-16(0.004) materials could achieve the
highest acetone adsorption capacity of 181 mg/g under 1000 ppmv
acetone vapor concentration at 25oC, which was also superior to
ZSM-5 (71mg/g) and MCM-41 (157mg/g) under same test conditions.
This can help to reduce the solid waste and the high adsorption
performance of the obtained materials could consider as potential
adsorbents for acetone adsorption.
Abstract: In the present work, fly ash geopolymer based
composites including polyester (PES) waste were studied. Specimens
of three compositions were prepared: (a) fly ash geopolymer with 5%
PES waste; (b) fly ash geopolymer mortar with 5% PES waste; (c) fly
ash geopolymer mortar with 6.25% PES waste. Compressive and
bending strength measurements, water absorption test and
determination of thermal conductivity coefficient were performed.
The results showed that the addition of sand in a mixture of
geopolymer with 5% PES content led to higher compressive strength,
while it increased water absorption and reduced thermal conductivity
coefficient. The increase of PES addition in geopolymer mortars
resulted in a more dense structure, indicated by the increase of
strength and thermal conductivity and the decrease of water
absorption.
Abstract: Activated carbons (M4P0, M4P2, and M5P2) used in
this research were produced from palm shell and polyetherether
ketone (PEEK) via carbonization, impregnation and microwave
activation. The adsorption/desorption process was carried out using
static volumetric adsorption. Regeneration is important in the overall
economy of the process and waste minimization. This work focuses
on the thermal regeneration of the CO2 exhausted microwave
activated carbons. The regeneration strategy adopted was thermal
with nitrogen purge desorption with N2 feed flow rate of 20 ml/min
for 1 h at atmospheric pressure followed by drying at 150oC.Seven
successive adsorption/regeneration processes were carried out on the
material. It was found that after seven adsorption regeneration cycles;
the regeneration efficiency (RE) for CO2 activated carbon from palm
shell only (M4P0) was more than 90% while that of hybrid palm
shell-PEEK (M4P2, M5P2) was above 95%. The cyclic adsorption
and regeneration shows the stability of the adsorbent materials.
Abstract: In this research (using induction furnace process)
nodular iron with three different percentages of copper (residual,
0.5% and 1,2%) was obtained. Chemical analysis was performed by
mass spectrometry and microstructures were characterized by Optical
Microscopy (ASTM E3) and Scanning Electron Microscopy (SEM).
The study of mechanical behavior was carried out in a mechanical
test machine (ASTM E8) and a Pin on disk tribometer (ASTM G99)
was used to assess wear resistance. It is observed that the dissolution
of copper in crystal lattice increases the pearlite structure improving
the wear and hardness behavior, but producing a contrary effect on
the energy absorption.
Abstract: In this paper, extract of papaya leaves are used as a
natural dye and combined by variations of solvent concentration
applied on DSSC (Dye-Sensitized Solar Cell). Indonesian geographic
located on the equator line occasions the magnitude of the potential
to develop organic solar cells made from extracts of chlorophyll as a
substitute for inorganic materials or synthetic dye on DSSC material.
Dye serves as absorbing photons which are then converted into
electrical energy. A conductive coated glass layer called TCO
(Transparent Conductive Oxide) is used as a substrate of electrode.
TiO2 nanoparticles as binding dye molecules, redox couple iodide/
tri-iodide as the electrolyte and carbon as the counter electrode in the
DSSC are used. TiO2 nanoparticles, organic dyes, electrolytes, and
counter electrode are arranged and combined with the layered
structure of the photo-catalyst absorption layer. Dye absorption
measurements using a spectrophotometer at 400-800 nm light
spectrum produces a total amount of chlorophyll 80.076 mg/l. The
test cell at 7 watt LED light with 5000 lux luminescence was
obtained Voc and Isc of 235.5 mV and 14 μA, respectively.
Abstract: This paper presents nonlinear pulse propagation characteristics for different input optical pulse shapes with various input pulse energy levels in semiconductor optical amplifiers. For simulation of nonlinear pulse propagation, finite-difference beam propagation method is used to solve the nonlinear Schrödinger equation. In this equation, gain spectrum dynamics, gain saturation are taken into account which depends on carrier depletion, carrier heating, spectral-hole burning, group velocity dispersion, self-phase modulation and two photon absorption. From this analysis, we obtained the output waveforms and spectra for different input pulse shapes as well as for different input energies. It shows clearly that the peak position of the output waveforms are shifted toward the leading edge which due to the gain saturation of the SOA for higher input pulse energies. We also analyzed and compared the normalized difference of full-width at half maximum for different input pulse shapes in the SOA.
Abstract: The purpose of this study is to compare Self
Compacting Concrete (SCC) and Conventional Concrete (CC) in
terms of their capillary water absorption. During the comparison of
SCC and CC, the effects of two different factors were also
investigated: concrete strength class and curing condition. In the
study, both SCC and CC were produced in three different concrete
classes (C25, C50 and C70) and the other parameter (i.e. curing
condition) was determined as two levels: moisture and air curing. It
was observed that, for both curing environments and all strength
classes of concrete, SCCs had lower capillary water absorption values
than that of CCs. It was also detected that, for both SCC and CC,
capillary water absorption values of samples kept in moisture curing
were significantly lower than that of samples stored in air curing.
Additionally, it was determined that capillary water absorption values
for both SCC and CC decrease with increasing strength class of
concrete for both curing environments.
Abstract: This work is focused on the study of valuation of
recycled concrete aggregates, by measuring certain properties of
concrete in the fresh and hardened state. In this study, rheological
tests and physic-mechanical characterization on concretes and
mortars were conducted with recycled concrete whose geometric
properties were identified aggregates. Mortars were elaborated with
recycled fine aggregate (0/5mm) and concretes were manufactured
using recycled coarse aggregates (5/12.5 mm and 12.5/20 mm). First,
a study of the mortars was conducted to determine the effectiveness
of polycarboxylate superplasticizer on the workability of these and
their action deflocculating of the recycled sand. The rheological
behavior of mortars based on fine aggregate recycled was
characterized. The results confirm that the mortars composed of
different fractions of recycled sand (0 /5) have a better mechanical
properties (compressive and flexural strength) compared to normal
mortar. Also, the mechanical strengths of concretes made with
recycled aggregates (5/12.5 mm and 12.5/20 mm), are comparable to
those of conventional concrete with conventional aggregates,
provided that the implementation can be improved by the addition of
a superplasticizer.
Abstract: Preparation of nanoparticles of cerium oxide and
adsorption of bovine serum albumin on them were studied. Particle
size distribution and influence of pH on zeta potential of prepared
CeO2 were determined. Average size of prepared cerium oxide
nanoparticles was 9 nm. The simultaneous measurements of the
bovine serum albumin adsorption and zeta potential determination of
the (adsorption) suspensions were carried out. The adsorption
isotherms were found to be of typical Langmuir type; values of the
bovine serum albumin adsorption capacities were calculated.
Increasing of pH led to decrease of zeta potential and decrease of
adsorption capacity of cerium oxide nanoparticles. The maximum
adsorption capacity was found for strongly acid suspension (am =
118 mg/g). The samples of nanoceria with positive zeta potential
adsorbed more bovine serum albumin on the other hand, the samples
with negative zeta potential showed little or no protein adsorption.
Surface charge or better say zeta potential of CeO2 nanoparticles
plays the key role in adsorption of proteins on such type of materials.
Abstract: Metallic foams have good potential for lightweight
structures for impact and blast mitigation. Therefore it is important to
find out the optimized foam structure (i.e. cell size, shape, relative
density, and distribution) to maximise energy absorption. In this
paper, quasistatic compression and microstructural characterization
of closed-cell aluminium foams of different pore size and cell
distributions have been carried out. We present results for two
different aluminium metal foams of density 0.49-0.51 g/cc and 0.31-
0.34 g/cc respectively that have been tested in quasi-static
compression. The influence of cell geometry and cell topology on
quasistatic compression behaviour has been investigated using optical
microscope and computed tomography (micro-CT) analysis. It is
shown that the deformation is not uniform in the structure and
collapse begins at the weakest point.
Abstract: The Proton Exchange Membranes (PEM) are largely studied because they operate at low temperatures and they are suitable for mobile applications. However, there are some deficiencies in their operation, mainly those that use ethanol as a hydrogen source, that require a certain attention. Therefore, this research aimed to develop Nafion® composite membranes, mixing clay minerals, kaolin and halloysite to the polymer matrix in order to improve the ethanol molecule retentions and, at the same time, to keep the system’s protonic conductivity. The modified Nafion/Kaolin, Nafion/Halloysite composite membranes were prepared in weight proportion of 0.5, 1.0 and 1.5. The membranes obtained were characterized as to their ethanol permeability, protonic conductivity and water absorption. The composite morphology and structure are characterized by SEM and EDX and the thermal behavior is determined by TGA and DSC. The analysis of the results shows ethanol permeability reduction from 48% to 63%. However, the protonic conductivity results are lower in relation to pure Nafion®. As to the thermal behavior, the Nafion® composite membranes were stable up to a temperature of 325ºC.
Abstract: Hydrogen fuel is a zero-emission fuel which uses electrochemical cells or combustion in internal engines, to power vehicles and electric devices. Methods of hydrogen storage for subsequent use span many approaches, including high pressures, cryogenics and chemical compounds that reversibly release H2 upon heating. Most research into hydrogen storage is focused on storing hydrogen as a lightweight, compact energy carrier for mobile applications. With the accelerating demand for cleaner and more efficient energy sources, hydrogen research has attracted more attention in the scientific community. Until now, full implementation of a hydrogen-based energy system has been hindered in part by the challenge of storing hydrogen gas, especially onboard an automobile. New techniques being researched may soon make hydrogen storage more compact, safe and efficient. In this overview, few hydrogen storage methods and mechanism of hydrogen uptake in carbon nanotubes are summarized.
Abstract: Fly ash is a waste material of coal firing thermal
plants that is released from thermal power plants. It was defined as
very fine particles that are drifted upward which are taken up by the
flue gases. The emerging amount of fly ash in the world is
approximately 600 million tons per year. In our country, it is
expected that will be occurred 50 million tons of waste ash per year
until 2020. The fly ashes can be evaluated by using as adsorbent
material. The purpose of this study is to investigate the possibility of
use of various fly ashes (Tuncbilek, Catalagzi, Orhaneli) like lowcost
adsorbents for heavy metal adsorption. First of all, fly ashes
were characterized. For this purpose; analyses such as XRD, XRF,
SEM and FT-IR were performed.
Abstract: We propose a phenomenological model for the
process of polymer desorption. In so doing, we omit the usual
theoretical approach of incorporating a fictitious viscoelastic
stress term into the flux equation. As a result, we obtain a
model that captures the essence of the phenomenon of trapping
skinning, while preserving the integrity of the experimentally
verified Fickian law for diffusion. An appropriate asymptotic
analysis is carried out, and a parameter is introduced to represent
the speed of the desorption front. Numerical simulations are
performed to illustrate the desorption dynamics of the model.
Recommendations are made for future modifications of the
model, and provisions are made for the inclusion of experimentally
determined frontal speeds.
Abstract: The state and stability of hemoglobin adsorbed on the
glass surface was investigated using slab optical waveguide (SOWG)
spectroscopy. The peak position of the absorption band of hemoglobin
adsorbed on the glass surface was same as that of the hemoglobin in
solution. This result suggests that no significant denaturation occurred
by adsorption. The adsorption of hemoglobin is relatively strong that
the hemoglobin molecules even remained adsorbed after rinsing the
cell with buffer solution. The peak shift caused by the reduction of
adsorbed hemoglobin was also observed.
Abstract: Adsorption of CS2 vapors has been studied on
different types of activated carbons obtained from different source
raw materials. The activated carbons have different surface areas and
are associated with varying amounts of the carbon-oxygen surface
groups. The adsorption of CS2 vapors is not directly related to surface
area, but is considerably influenced by the presence of carbonoxygen
surface groups. The adsorption decreases on increasing the
amount of carbon-oxygen surface groups on oxidation and increases
when these surface groups are eliminated on degassing. The
adsorption is maximum in case of the 950°-degassed carbon sample
which is almost completely free of any associated oxygen. The
kinetic data as analysed by Empirical diffusion model and Linear
driving force mass transfer model indicate that the adsorption does
not involve Fickian diffusion but may be considered as a pseudo first
order mass transfer process. The activation energy of adsorption and
isosteric enthalpies of adsorption indicate that the adsorption does not
involve interaction between CS2 and carbon-oxygen surface groups,
but hydrophobic interactions between CS2 and C-C atoms in the
carbon lattice.
Abstract: Group contribution methods such as the UNIFAC are
very useful to researchers and engineers involved in synthesis,
feasibility studies, design and optimization of separation processes.
They can be applied successfully to predict phase equilibrium and
excess properties in the development of chemical and separation
processes. The main focus of this work was to investigate the
possibility of absorbing selected volatile organic compounds (VOCs)
into polydimethylsiloxane (PDMS) using three selected UNIFAC
group contribution methods. Absorption followed by subsequent
stripping is the predominant available abatement technology of
VOCs from flue gases prior to their release into the atmosphere. The
original, modified and effective UNIFAC models were used in this
work. The thirteen selected VOCs that have been considered in this
research are: pentane, hexane, heptanes, trimethylamine, toluene,
xylene, cyclohexane, butyl acetate, diethyl acetate, chloroform,
acetone, ethyl methyl ketone and isobutyl methyl ketone. The
computation was done for solute VOC concentration of 8.55x10-8
which is well in the infinite dilution region. The results obtained in
this study compare very well with those published in literature
obtained through both measurements and predictions. The phase
equilibrium obtained in this study show that PDMS is a good
absorbent for the removal of VOCs from contaminated air streams
through physical absorption.
Abstract: The current work focuses on rephrasing the harmful
effects of mercury that is being released from a number of sources.
Most of the sources are from the industrial waste water. Different
techniques of mercury removal have been discussed and a brief
comparison among these has been made. The experimental work has
been conducted for two most widely used methods of mercury
removal and comparison in terms of their efficiency has been made.
Abstract: Photo-BJMOSFET (Bipolar Junction Metal-Oxide-
Semiconductor Field Effect Transistor) fabricated on SOI film was proposed. ITO film is adopted in the device as gate electrode to reduce
light absorption. Depletion region but not inversion region is formed
in film by applying gate voltage (but low reverse voltage) to achieve
high photo-to-dark-current ratio. Comparisons of photoelectriccharacteristics
executed among VGK=0V, 0.3V, 0.6V, 0.9V and 1.0V
(reverse voltage VAK is equal to 1.0V for total area of 10×10μm2). The
results indicate that the greatest improvement in photo-to-dark-current
ratio is achieved up to 2.38 at VGK=0.6V. In addition,
photo-BJMOSFET is compatible with CMOS integration due to big
input resistance