Abstract: Heat pipes are two-phase heat transfer devices with
high effective thermal conductivity. Due to the high heat transport
capacity, heat exchanger with heat pipes has become much smaller
than traditional heat exchangers in handling high heat fluxes. With
the working fluid in a heat pipe, heat can be absorbed on the
evaporator region and transported to the condenser region where the
vapour condenses releasing the heat to the cooling media. Heat pipe
technology has found increasing applications in enhancing the
thermal performance of heat exchangers in microelectranics, energy
saving in HVAC systems for operating rooms,surgery centers, hotels,
cleanrooms etc, temperature regulation systems for the human body
and other industrial sectors. Development activity in heat pipe and
thermosyphon technology in asia in recent years is surveyed. Some
new results obtained in Australia and other countries are also
included.
Abstract: In this paper, the innovative intelligent fuzzy weighted
input estimation method (FWIEM) can be applied to the inverse heat
transfer conduction problem (IHCP) to estimate the unknown
time-varying heat flux efficiently as presented. The feasibility of this
method can be verified by adopting the temperature measurement
experiment. We would like to focus attention on the heat flux
estimation to three kinds of samples (Copper, Iron and Steel/AISI 304)
with the same 3mm thickness. The temperature measurements are then
regarded as the inputs into the FWIEM to estimate the heat flux. The
experiment results show that the proposed algorithm can estimate the
unknown time-varying heat flux on-line.
Abstract: In the present study, the rate of NOx emission in a
combustion chamber working in conventional combustion and High
Temperature Air Combustion (HiTAC) system are examined using
CFD modeling. The effect of peak temperature, combustion air
temperature and oxygen concentration on NOx emission rate was
undertaken. Results show that in a fixed oxygen concentration,
increasing the preheated air temperature will increase the peak
temperature and NOx emission rate. In addition, it was observed that
the reduction of the oxygen concentration in the fixed preheated air
temperature decreases the peak temperature and NOx emission rate.
On the other hand, the results show that increase of preheated air
temperature at various oxygen concentrations increases the NOx
emission rate. However, the rate of increase in HiTAC conditions is
quite lower than the conventional combustion. The modeling results
show that the NOx emission rate in HiTAC combustion is 133% less
than that of the conventional combustion.
Abstract: Lattice Monte Carlo methods are an excellent
choice for the simulation of non-linear thermal diffusion
problems. In this paper, and for the first time, Lattice Monte
Carlo analysis is performed on thermal diffusion combined
with convective heat transfer. Laminar flow of water modeled
as an incompressible fluid inside a copper pipe with a constant
surface temperature is considered. For the simulation of
thermal conduction, the temperature dependence of the
thermal conductivity of the water is accounted for. Using the
novel Lattice Monte Carlo approach, temperature distributions
and energy fluxes are obtained.
Abstract: Phytases are enzymes used as an important component
in monogastric animals feeds in order to improve phosphorous
availability, since it is not readily assimilated by these animals in the
form of the phytate presented in plants and grains. As these enzymes
are used in industrial activities, they must retain its catalytic activities
during a certain storage period. This study presents information about
the stability of 4 different phytases, produced by four macromycetes
fungi through solid-state fermentation (SSF). There is a lack of data
in literature concerning phytase from macromycetes shelf-life in
storage conditions at room, cooling and freezing temperatures. The 4
phytases from macromycetes still had enzymatic activities around
100 days of storage at room temperature. At cooling temperature in
146 days of studies, the phytase from G. stipitatum was the most
stable with 44% of the initial activity, in U.gds (units per gram of
dried fermented substrate). The freezing temperature was the best
condition storage for phytases from G. stipitatum and T. versicolor.
Each condition provided a study for each mushroom phytase,
totalizing 12 studies. The phytases showed to be stable for a long
period without the addition of additives.
Abstract: Rice husk is a lignocellulosic source that can be
converted to ethanol. Three hundreds grams of rice husk was mixed
with 1 L of 0.18 N sulfuric acid solutions then was heated in an
autoclave. The reaction was expected to be at constant temperature
(isothermal), but before that temperature was achieved, reaction has
occurred. The first liquid sample was taken at temperature of 140 0C
and repeated every 5 minute interval. So the data obtained are in the
regions of non-isothermal and isothermal. It was observed that the
degradation has significant effects on the ethanol production. The
kinetic constants can be expressed by Arrhenius equation with the
frequency factors for hydrolysis and sugar degradation of 1.58 x 105
1/min and 2.29 x 108 L/mole/min, respectively, while the activation
energies are 64,350 J/mole and 76,571 J/mole. The highest ethanol
concentration from fermentation is 1.13% v/v, attained at 220 0C.
Abstract: Wheat has a bimodal starch granule population and the dependency of the rate of enzymatic hydrolysis on particle size has been investigated. Ungelatinised wheaten starch granules were separated into two populations by sedimentation and decantation. Particle size was analysed by laser diffraction and morphological characteristics were viewed using SEM. The sedimentation technique though lengthy, gave satisfactory separation of the granules. Samples (10μm and original) were digested with a-amylase using a dialysis model. Granules of 10μm (p10μm. Moreover, the digestion rate was dependent on particle size whereby smaller granules produced higher rate of release. The methodology and results reported here can be used as a basis for further evaluations designed to delay the release of glucose during the digestion of native starches.
Abstract: Plant growth is affected by the osmotic stress as well as toxicity of salt in leaves. In order to study of salt stress effects on stomatal conductance and growth rate and relationship between them as wells osmotic and Na+-specific effects on these traits, four bread wheat genotypes differing in salt tolerance were selected. Salinity was applied when the leaf 4 was fully expanded. Sodium (Na+) concentrations in flag leaf blade at 3 salinity levels (0, 100 and 200 mM NaCl) were measured. Salt-tolerant genotypes showed higher stomatal conductance and growth rate compared to salt-sensitive ones. After 10 and 20 days exposure to salt, stomatal conductance and relative growth rate were reduced, but the reduction was greater in sensitive genotypes. Growth rate was reduced severely in the first period (1-10 days) of salt commencements and it was due to osmotic effect of salt not Na+ toxicity. In the second period (11-20 days) after salt treatment growth reduced only when salt accumulated to toxic concentrations in the leaves. A positive relationship between stomatal conductance and relative growth rate showed that stomatal conductance can be a reliable indicator of growth rate, and finally can be considered as a sensitive indicator of the osmotic stress. It seems 20 days after salinity, the major effect of salt, especially at low to moderate salinity levels on growth properties was due to the osmotic effect of salt, not to Na+-specific effects within the plant.
Abstract: In this manuscript, the LBM is applied for simulating of Mixed Convection in a Lid-Driven cavity with an open side. The cavity horizontal walls are insulated while the west Lid-driven wall is maintained at a uniform temperature higher than the ambient. Prandtl number (Pr) is fixed to 0.71 (air) while Reynolds number (Re) , Richardson number (Ri) and aspect ratio (A) of the cavity are changed in the range of 50-150 , of 0.1-10 and of 1-4 , respectively. The numerical code is validated for the standard square cavity, and then the results of an open ended cavity are presented. Result shows by increasing of aspect ratio, the average Nusselt number (Nu) on lid- driven wall decreases and with same Reynolds number (Re) by increasing of aspect ratio (A), Richardson number plays more important role in heat transfer rate.
Abstract: A stack with a small critical temperature gradient is
desirable for a standing wave thermoacoustic engine to obtain a low
onset temperature difference (the minimum temperature difference to
start engine-s self-oscillation). The viscous and heat relaxation loss in
the stack determines the critical temperature gradient. In this work, a
dimensionless critical temperature gradient factor is obtained based
on the linear thermoacoustic theory. It is indicated that the
impedance determines the proportion between the viscous loss, heat
relaxation losses and the power production from the heat energy. It
reveals the effects of the channel dimensions, geometrical
configuration and the local acoustic impedance on the critical
temperature gradient in stacks. The numerical analysis shows that
there exists a possible optimum combination of these parameters
which leads to the lowest critical temperature gradient. Furthermore,
several different geometries have been tested and compared
numerically.
Abstract: The present paper is an experimental investigation of
roughness effects on nucleate pool boiling of refrigerant R113 on
horizontal circular copper surfaces. The copper samples were treated
by different sand paper grit sizes to achieve different surface
roughness. The average surface roughness of the four samples was
0.901, 0.735, 0.65, and 0.09, respectively. The experiments were
performed in the heat flux range of 8 to 200kW/m2. The heat transfer
coefficient was calculated by measuring wall superheat of the
samples and the input heat flux. The results show significant
improvement of heat transfer coefficient as the surface roughness is
increased. It is found that the heat transfer coefficient of the sample
with Ra=0.901 is 3.4, 10.5, and 38.5% higher in comparison with
surfaces with Ra of 0.735, 0.65, and 0.09 at heat flux of 170 kW/m2.
Moreover, the results are compared with literature data and the well
known Cooper correlation.
Abstract: In this study, an analysis has been performed for
free convection with radiation effect over a thermal forming
nonlinearly stretching sheet. Parameters n, k0, Pr, G represent
the dominance of the nonlinearly effect, radiation effect, heat
transfer and free convection effects which have been presented
in governing equations, respectively. The similarity
transformation and the finite-difference methods have been
used to analyze the present problem. From the results, we find
that the effects of parameters n, k0, Pr, Ec and G to the
nonlinearly stretching sheet. The increase of Prandtl number Pr,
free convection parameter G or radiation parameter k0 resulting
in the increase of heat transfer effects, but increase of the
viscous dissipation number Ec will decrease of heat transfer
effect.
Abstract: The main emphasis of metallurgists has been to process the materials to obtain the balanced mechanical properties for the given application. One of the processing routes to alter the properties is heat treatment. Nearly 90% of the structural applications are related to the medium carbon an alloyed steels and hence are regarded as structural steels. The major requirement in the conventional steel is to improve workability, toughness, hardness and grain refinement. In this view, it is proposed to study the mechanical and tribological properties of unalloyed structural (AISI 1140) steel with different thermal (heat) treatments like annealing, normalizing, tempering and hardening and compared with as brought (cold worked) specimen. All heat treatments are carried out in atmospheric condition. Hardening treatment improves hardness of the material, a marginal decrease in hardness value with improved ductility is observed in tempering. Annealing and normalizing improve ductility of the specimen. Normalized specimen shows ultimate ductility. Hardened specimen shows highest wear resistance in the initial period of slide wear where as above 25KM of sliding distance, as brought steel dominates the hardened specimen. Both mild and severe wear regions are observed. Microstructural analysis shows the existence of pearlitic structure in normalized specimen, lath martensitic structure in hardened, pearlitic, ferritic structure in annealed specimen.
Abstract: In this paper, the energy performance of a selected
UHDE Ammonia plant is optimized by conducting heat integration through waste heat recovery and the synthesis of a heat exchange
network (HEN). Minimum hot and cold utility requirements were estimated through IChemE spreadsheet. Supporting simulation was
carried out using HYSYS software. The results showed that there is
no need for heating utility while the required cold utility was found to
be around 268,714 kW. Hence a threshold pinch case was faced. Then, the hot and cold streams were matched appropriately. Also,
waste heat recovered resulted with savings in HP and LP steams of
approximately 51.0% and 99.6%, respectively. An economic analysis
on proposed HEN showed very attractive overall payback period not
exceeding 3 years. In general, a net saving approaching 35% was
achieved in implementing heat optimization of current studied UHDE Ammonia process.
Abstract: The Spalart and Allmaras turbulence model has been
implemented in a numerical code to study the compressible turbulent
flows, which the system of governing equations is solved with a
finite volume approach using a structured grid. The AUSM+ scheme
is used to calculate the inviscid fluxes. Different benchmark
problems have been computed to validate the implementation and
numerical results are shown. A special Attention is paid to wall jet
applications. In this study, the jet is submitted to various wall
boundary conditions (adiabatic or uniform heat flux) in forced
convection regime and both two-dimensional and axisymmetric wall
jets are considered. The comparison between the numerical results
and experimental data has given the validity of this turbulence model
to study the turbulent wall jets especially in engineering applications.
Abstract: Solar energy is not only sustainable but also a clean
alternative to be used as source of high temperature heat for many
processes and power generation. However, the major drawback of
solar energy is its transient nature. Especially in solar
thermochemical processing, it is crucial to maintain constant or semiconstant
temperatures inside the solar reactor. In our laboratory, we
have developed a mechanism allowing us to achieve semi-constant
temperature inside the solar reactor. In this paper, we introduce the
concept along with some updated designs and provide the optical
analysis of the concept under various incoming flux.
Abstract: In this paper the problems associated with immunity
of embedded systems used in Motor-Drive systems are investigated
and appropriate solutions are presented. Integration of VSD motor
systems (Integral Motor) while partially reducing some of these
effects, adds to immunity problem of their embedded systems. Fail
safe operation of an Integral Motor in arduous industrial
environments is considered. In this paper an integral motor with a
unique design is proposed to overcome critical issues such as heat,
vibration and electromagnetic interference which are damaging to
sensitive electronics without requirement of any additional cooling
system. Advantages of the proposed Integral motor are compactness
of combo motor and drive system with no external cabling/wiring.
This motor provides a perfect shielding for least amount of radiated
emission. It has an inbuilt filter for EMC compliance and has been
designed to provide lower EMC noise for immunity of the internal
electronics as well as the other neighbouring systems.
Abstract: As the fossil fuels kept on depleting, intense research in developing hydrogen (H2) as the alternative fuel has been done to cater our tremendous demand for fuel. The potential of H2 as the ultimate clean fuel differs with the fossil fuel that releases significant amounts of carbon dioxide (CO2) into the surrounding and leads to the global warming. The experimental work was carried out to study the production of H2 from palm kernel shell steam gasification at different variables such as heating rate, steam to biomass ratio and adsorbent to biomass ratio. Maximum H2 composition which is 61% (volume basis) was obtained at heating rate of 100oCmin-1, steam/biomass of 2:1 ratio, and adsorbent/biomass of 1:1 ratio. The commercial adsorbent had been modified by utilizing the alcoholwater mixture. Characteristics of both adsorbents were investigated and it is concluded that flowability and floodability of modified CaO is significantly improved.
Abstract: The use of neural networks is popular in various
building applications such as prediction of heating load, ventilation
rate and indoor temperature. Significant is, that only few papers deal
with indoor carbon dioxide (CO2) prediction which is a very good
indicator of indoor air quality (IAQ). In this study, a data-driven
modelling method based on multilayer perceptron network for indoor
air carbon dioxide in an apartment building is developed.
Temperature and humidity measurements are used as input variables
to the network. Motivation for this study derives from the following
issues. First, measuring carbon dioxide is expensive and sensors
power consumptions is high and secondly, this leads to short
operating times of battery-powered sensors. The results show that
predicting CO2 concentration based on relative humidity and
temperature measurements, is difficult. Therefore, more additional
information is needed.
Abstract: In this paper, we have proposed a novel FinFET with
extended body under the poly gate, which is called EB-FinFET, and
its characteristic is demonstrated by using three-dimensional (3-D)
numerical simulation. We have analyzed and compared it with
conventional FinFET. The extended body height dependence on the
drain induced barrier lowering (DIBL) and subthreshold swing (S.S)
have been also investigated. According to the 3-D numerical
simulation, the proposed structure has a firm structure, an acceptable
short channel effect (SCE), a reduced series resistance, an increased
on state drain current (I
on) and a large normalized I
DS. Furthermore,
the structure can also improve corner effect and reduce self-heating
effect due to the extended body. Our results show that the EBFinFET
is excellent for nanoscale device.