Abstract: The most severe damage of the turbine rotor is its
distortion. The rotor straightening process must lead, at the first
stage, to removal of the stresses from the material by annealing and
next, to straightening of the plastic distortion without leaving any
stress by hot spotting. The straightening method does not produce
stress accumulations and the heating technique, developed
specifically for solid forged rotors and disks, enables to avoid local
overheating and structural changes in the material. This process also
does not leave stresses in the shaft material. An experimental study
of hot spotting is carried out on a large turbine rotor and some of the
most important effective parameters that must be considered on
annealing and hot spotting processes are investigated in this paper.
Abstract: The mechanism of microwave heating is essentially
that of dielectric heating. After exposing the emulsion to the
microwave Electromagnetic (EM) field, molecular rotation and ionic
conduction due to the penetration of (EM) into the emulsion are
responsible for the internal heating. To determine the capability of
microwave technology in demulsification of crude oil emulsions,
microwave demulsification method was applied in a 50-50 % and 20-
80 % water-in-oil emulsions with microwave exposure time varied
from 20-180 sec. Transient temperature profiles of water-in-oil
emulsions inside a cylindrical container were measured. The
temperature rise at a given location was almost horizontal (linear).
The average rates of temperature increase of 50-50 % and 20-80 %
water-in-oil emulsions are 0.351 and 0.437 oC/sec, respectively. The
rate of temperature increase of emulsions decreased at higher
temperature due to decreasing dielectric loss of water. These results
indicate that microwave demulsification of water-in-oil emulsions
does not require chemical additions. Microwave has the potential to
be used as an alternative way in the demulsification process.
Abstract: We successfully developed a new straw combustion
technology that efficiently reduces problems with unmanageable deposits inside straw fueled boilers in Zluticka Heating Plant. The
deposits are mainly created by glass-forming melts. We plotted straw compositions in K2O-CaO-SiO2 phase diagram and illustrated
they are in the area of low-melting eutectic poi
melting of ash and the formation of deposits
compositions by injecting additives into biomass fuel
ueled points. To prevent the
deposits, we modified ash
fuel.
Abstract: The crystallization kinetics and phase transformation
of SiO2.Al2O3.0,56P2O5.1,8CaO.0,56CaF2 glass have been
investigated using differential thermal analysis (DTA), x-ray
diffraction (XRD), and scanning electron microscopy (SEM). Glass
samples were obtained by melting the glass mixture at 14500С/120
min. in platinum crucibles. The mixture were prepared from
chemically pure reagents: SiO2, Al(OH)3, H3PO4, CaCO3 and CaF2.
The non-isothermal kinetics of crystallization was studied by
applying the DTA measurements carried out at various heating rates.
The activation energies of crystallization and viscous flow were
measured as 348,4 kJ.mol–1 and 479,7 kJ.mol–1 respectively. Value of
Avrami parameter n ≈ 3 correspond to a three dimensional of crystal
growth mechanism. The major crystalline phase determined by XRD
analysis was fluorapatite (Ca(PO4)3F) and as the minor phases –
fluormargarite (CaAl2(Al2SiO2)10F2) and vitlokite (Ca9P6O24). The
resulting glass-ceramic has a homogeneous microstructure, composed
of prismatic crystals, evenly distributed in glass phase.
Abstract: In the present study, a steady-state simulation model
has been developed to evaluate the system performance of a
transcritical carbon dioxide heat pump system for simultaneous water
cooling and heating. Both the evaporator (including both two-phase
and superheated zone) and gas cooler models consider the highly
variable heat transfer characteristics of CO2 and pressure drop. The
numerical simulation model of transcritical CO2 heat pump has been
validated by test data obtained from experiments on the heat pump
prototype. Comparison between the test results and the model
prediction for system COP variation with compressor discharge
pressure shows a modest agreement with a maximum deviation of
15% and the trends are fairly similar. Comparison for other operating
parameters also shows fairly similar deviation between the test
results and the model prediction. Finally, the simulation results are
presented to study the effects of operating parameters such as,
temperature of heat exchanger fluid at the inlet, discharge pressure,
compressor speed on system performance of CO2 heat pump, suitable
in a dairy plant where simultaneous cooling at 4oC and heating at
73oC are required. Results show that good heat transfer properties of
CO2 for both two-phase and supercritical region and efficient
compression process contribute a lot for high system COPs.
Abstract: A parallel computational fluid dynamics code has been
developed for the study of aerodynamic heating problem in hypersonic
flows. The code employs the 3D Navier-Stokes equations as the basic
governing equations to simulate the laminar hypersonic flow. The cell
centered finite volume method based on structured grid is applied for
spatial discretization. The AUSMPW+ scheme is used for the inviscid
fluxes, and the MUSCL approach is used for higher order spatial
accuracy. The implicit LU-SGS scheme is applied for time integration
to accelerate the convergence of computations in steady flows. A
parallel programming method based on MPI is employed to shorten
the computing time. The validity of the code is demonstrated by
comparing the numerical calculation result with the experimental data
of a hypersonic flow field around a blunt body.
Abstract: The stability of Newtonian and Non-Newtonian extending films under local or global heating or cooling conditions are considered. The thickness-averaged mass, momentum and energy equations with convective and radiative heat transfer are derived, both for Newtonian and non-Newtonian fluids (Maxwell, PTT and Giesekus models considered). The stability of the system is explored using either eigenvalue analysis or transient simulations. The results showed that the influence of heating and cooling on stability strongly depends on the magnitude of the Peclet number. Examples of stabilization or destabilization of heating or cooling are shown for Pe
Abstract: Drying characteristics of rough rice (variety of lenjan) with an initial moisture content of 25% dry basis (db) was studied in a hot air dryer assisted by infrared heating. Three arrival air temperatures (30, 40 and 500C) and four infrared radiation intensities (0, 0.2 , 0.4 and 0.6 W/cm2) and three arrival air speeds (0.1, 0.15 and 0.2 m.s-1) were studied. Bending strength of brown rice kernel, percentage of cracked kernels and time of drying were measured and evaluated. The results showed that increasing the drying arrival air temperature and radiation intensity of infrared resulted decrease in drying time. High bending strength and low percentage of cracked kernel was obtained when paddy was dried by hot air assisted infrared dryer. Between this factors and their interactive effect were a significant difference (p
Abstract: A numerical study on the heat transfer in the thermal
barrier coatings and the substrates of a parallel-plate enclosure is
carried out. Some of the thermal barrier coatings, such as ceramics, are
semitransparent and are of interest for high-temperature applications
where radiation effects are significant. The radiative transfer equations
and the energy equations are solved by using the discrete ordinates
method and the finite difference method. Illustrative results are
presented for temperature distributions in the coatings and the opaque
walls under various heating conditions. The results show that the
temperature distribution is more uniform in the interior portion of each
coating away from its boundary for the case with a larger average of
varying refractive index and a positive gradient of refractive index
enhances radiative transfer to the substrates.
Abstract: Attempts to add fibre and polyphenols (PPs) into
popular beverages present challenges related to the properties of
finished products such as smoothies. Consumer acceptability,
viscosity and phenolic composition of smoothies containing high
levels of fruit fibre (2.5-7.5 g per 300 mL serve) and PPs (250-750
mg per 300 mL serve) were examined. The changes in total
extractable PP, vitamin C content, and colour of selected smoothies
over a storage stability trial (4°C, 14 days) were compared. A set of
acidic aqueous model beverages were prepared to further examine
the effect of two different heat treatments on the stability and
extractability of PPs. Results show that overall consumer
acceptability of high fibre and PP smoothies was low, with average
hedonic scores ranging from 3.9 to 6.4 (on a 1-9 scale). Flavour,
texture and overall acceptability decreased as fibre and polyphenol
contents increased, with fibre content exerting a stronger effect.
Higher fibre content resulted in greater viscosity, with an elevated PP
content increasing viscosity only slightly. The presence of fibre also
aided the stability and extractability of PPs after heating. A reduction
of extractable PPs, vitamin C content and colour intensity of
smoothies was observed after a 14-day storage period at 4°C. Two
heat treatments (75°C for 45 min or 85°C for 1 min) that are
normally used for beverage production, did not cause significant
reduction of total extracted PPs. It is clear that high levels of added
fibre and PPs greatly influence the consumer appeal of smoothies,
suggesting the need to develop novel formulation and processing
methods if a satisfactory functional beverage is to be developed
incorporating these ingredients.
Abstract: Even it has been recognized that Shape Memory
Alloys (SMA) have a significant potential for deployment actuators,
the number of applications of SMA-based actuators to the present
day is still quite small, due to the need of deep understanding of the
thermo-mechanical behavior of SMA, causing an important need for
a mathematical model able to describe all thermo-mechanical
properties of SMA by relatively simple final set of constitutive
equations. SMAs offer attractive potentials such as: reversible strains
of several percent, generation of high recovery stresses and high
power / weight ratios. The paper tries to provide an overview of the
shape memory functions and a presentation of the designed and
developed temperature control system used for a gripper actuated by
two pairs of differential SMA active springs. An experimental setup
was established, using electrical energy for actuator-s springs heating
process. As for holding the temperature of the SMA springs at certain
level for a long time was developed a control system in order to
avoid the active elements overheating.
Abstract: The paper presents the results of the European EIE
project “Realising the potential for small scale renewable energy
sources in the home – Kyotointhehome". The project's global aim is
to inform and educate teachers, students and their families so that
they can realise the need and can assess the potential for energy
efficiency (EE) measures and renewable energy sources (RES) in
their homes. The project resources were translated and trialled by 16
partners in 10 European countries.
A web-based methodology which will enable families to assess
how RES can be incorporated into energy efficient homes was
accomplished. The web application “KYOTOINHOME" will help
the citizens to identify what they can do to help their community
meet the Kyoto target for greenhouse gas reductions and prevent
global warming. This application provides useful information on how
the citizens can use renewable energy sources in their home to
provide space heating and cooling, hot water and electricity. A
methodology for assessing heat loss in a dwelling and application of
heat pump system was elaborated and will be implemented this year.
For schools, we developed a set of practical activities concerned with
preventing climate change through using renewable energy sources.
Complementary resources will also developed in the Romanian
research project “Romania Contribution to the European Targets
Regarding the Development of Renewable Energy Sources" -
PROMES.
Abstract: Solar water heating (SWH) systems are gaining popularity in ASEAN in the midst of increasing number of affluent population in society and environmental concerns from seemingly unchanged reliance on fossil-based fuels. The penetration of these systems and technologies into ASEAN markets is a welcome development; however there is a need for the method of assessment of their thermal performances. This paper discusses the reasons for this need and a suitable method for thermal performance evaluation of SWH systems in ASEAN. The paper also calls on research to be focused on the establishment of reliable data to be entered into the performance rating software. The establishment of accredited solar systems testing facilities can help boost the competitiveness of ASEAN solar industry.
Abstract: This paper presents the exergy analysis of a
desalination unit using humidification-dehumidification process.
Here, this unit is considered as a thermal system with three main
components, which are the heating unit by using a solar collector, the
evaporator or the humidifier, and the condenser or the dehumidifier.
In these components the exergy is a measure of the quality or grade
of energy and it can be destroyed in them. According to the second
law of thermodynamics this destroyed part is due to irreversibilities
which must be determined to obtain the exergetic efficiency of the
system.
In the current paper a computer program has been developed using
visual basic to determine the exergy destruction and the exergetic
efficiencies of the components of the desalination unit at variable
operation conditions such as feed water temperature, outlet air
temperature, air to feed water mass ratio and salinity, in addition to
cooling water mass flow rate and inlet temperature, as well as
quantity of solar irradiance.
The results obtained indicate that the exergy efficiency of the
humidifier increases by increasing the mass ratio and decreasing the
outlet air temperature. In the other hand the exergy efficiency of the
condenser increases with the increase of this ratio and also with the
increase of the outlet air temperature.
Abstract: Laser soldering is based on applying some soldering material (albumin) onto the approximated edges of the cut and heating the solder (and the underlying tissues) by a laser beam. Endogenous and exogenous materials such as indocyanine green (ICG) are often added to solders to enhance light absorption. Gold nanoshells are new materials which have an optical response dictated by the plasmon resonance. The wavelength at which the resonance occurs depends on the core and shell sizes, allowing nanoshells to be tailored for particular applications. The purposes of this study was use combination of ICG and different concentration of gold nanoshells for skin tissue soldering and also to examine the effect of laser soldering parameters on the properties of repaired skin. Two mixtures of albumin solder and different combinations of ICG and gold nanoshells were prepared. A full thickness incision of 2×20 mm2 was made on the surface and after addition of mixtures it was irradiated by an 810nm diode laser at different power densities. The changes of tensile strength σt due to temperature rise, number of scan (Ns), and scan velocity (Vs) were investigated. The results showed at constant laser power density (I), σt of repaired incisions increases by increasing the concentration of gold nanoshells in solder, Ns and decreasing Vs. It is therefore important to consider the tradeoff between the scan velocity and the surface temperature for achieving an optimum operating condition. In our case this corresponds to σt =1800 gr/cm2 at I~ 47 Wcm-2, T ~ 85ºC, Ns =10 and Vs=0.3mms-1.
Abstract: The intermittent nature of solar energy and the energy
requirements of buildings necessitate the storage of thermal energy.
In this paper a hybrid system of storing solar energy has been
analyzed. Adding a LHS medium to a commercial solar water heater,
the required energy for heating a small room was obtained in
addition to preparing hot water. In other words, the suggested hybrid
storage system consists of two tanks: a water tank as a SHS medium;
and a paraffin tank as a LHS medium. A computing program was
used to find the optimized time schedule of charging the storage
tanks during each day, according to the solar radiation conditions.
The results show that the use of such system can improve the
capability of energy gathering comparing to the individual water
storage tank during the cold months of the year. Of course, because
of the solar radiation angles and shorten daylight in December &
January, the performance will be the same as the simple solar water
heaters (in the northern hemisphere). But the extra energy stored in
November, February, March & April, can be useful for heating a
small room for 3 hours during the cold days.
Abstract: The potential, opportunities and drawbacks of biogas
technology use in Turkey are evaluated in this paper. Turkey is
dependent on foreign sources of energy. Therefore, use of biogas
technology would provide a safe way of waste disposal and recovery
of renewable energy, particularly from a sustainable domestic source,
which is less unlikely to be influenced by international price or
political fluctuations. Use of biogas technology would especially
meet the cooking, heating and electricity demand in rural areas and
protect the environment, additionally creating new job opportunities
and improving social-economical conditions.
Abstract: This paper presents the modeling results of an
innovative system for the temperature control in the interior
compartment of a stationary automobile facing the solar energy from
the sun. A very thin layer of PCM inside a pouch placed in the
ceiling of the car in which the heating energy is absorbed and release
with melting and solidification of phase change materials. As a result
the temperature of the car interior is maintained in the comfort
condition. The amount of required PCM has been calculated to be
about 755 g. The PCM-temperature controlling system is simple and
has a potential to be implemented as a practical solution to prevent
undesirable heating of the automobile-s cabin.
Abstract: In this paper, we have developed an explicit analytical
drain current model comprising surface channel potential and
threshold voltage in order to explain the advantages of the proposed
Gate Stack Double Diffusion (GSDD) MOSFET design over the
conventional MOSFET with the same geometric specifications that
allow us to use the benefits of the incorporation of the high-k layer
between the oxide layer and gate metal aspect on the immunity of the
proposed design against the self-heating effects. In order to show the
efficiency of our proposed structure, we propose the simulation of the
power chopper circuit. The use of the proposed structure to design a
power chopper circuit has showed that the (GSDD) MOSFET can
improve the working of the circuit in terms of power dissipation and
self-heating effect immunity. The results so obtained are in close
proximity with the 2D simulated results thus confirming the validity
of the proposed model.
Abstract: Organic Flash Cycle (OFC) has potential of improving
efficiency for recovery of low temperature heat sources mainly due to
reducing temperature mismatch in the heat exchanger. In this work
exergetical performance analysis of ORC is conducted for recovery of
low grade heat source. Effects of system parameters such as flash
evaporation temperature or heating temperature are theoretically
investigated on the exergy destructions (anergies) at various
components of the system as well as exergy efficiency. Results show
that exergy efficiency has a peak with respect to the flash temperature,
and the optimum flash temperature increases with the heating
temperature. The component where the largest exergy destruction
occurs varies with the flash temperature or heating temperature.