Abstract: In order to compare the performance of the carbon dioxide and HFC-125 heat pumps for medium-and high-temperature heating, both heat pump cycles were optimized using a simulation method. To fairly compare the performance of the cycles by using different working fluids, each cycle was optimized from the viewpoint of heating COP by two design parameters. The first is the gas cooler exit temperature and the other is the ratio of the overall heat conductance of the gas cooler to the combined overall heat conductance of the gas cooler and the evaporator. The inlet and outlet temperatures of secondary fluid of the gas cooler were fixed at 40/90°C and 40/150°C.The results shows that the HFC-125 heat pump has 6% higher heating COP than carbon dioxide heat pump when the heat sink exit temperature is fixed at 90ºC, while the latter outperforms the former when the heat sink exit temperature is fixed at 150ºC under the simulation conditions considered in the present study.
Abstract: Hybridization refers to the crossing breeding of two
plants. Coefficient of Parentage (COP) is used by the plant breeders
to determine the genetic diversity across various varieties so as to
incorporate the useful characters of the two varieties to develop a
new crop variety with particular useful characters. Genetic Diversity
is the prerequisite for any cultivar development program. Genetic
Diversity depends upon the pedigree information of the varieties
based on particular levels. Pedigree refers to the parents of a
particular variety at various levels. This paper discusses the searching
and analyses of different possible pairs of varieties selected on the
basis of morphological characters, Climatic conditions and Nutrients
so as to obtain the most optimal pair that can produce the required
crossbreed variety. An algorithm was developed to determine the
coefficient of parentage (COP) between the selected wheat varieties.
Dummy values were used wherever actual data was not available.
Abstract: Predictions of flow and heat transfer characteristics and shape optimization in internally finned circular tubes have been performed on three-dimensional periodically fully developed turbulent flow and thermal fields. For a trapezoidal fin profile, the effects of fin height h, upper fin widths d1, lower fin widths d2, and helix angle of fin ? on transport phenomena are investigated for the condition of fin number of N = 30. The CFD and mathematical optimization technique are coupled in order to optimize the shape of internally finned tube. The optimal solutions of the design variables (i.e., upper and lower fin widths, fin height and helix angle) are numerically obtained by minimizing the pressure loss and maximizing the heat transfer rate, simultaneously, for the limiting conditions of d1 = 0.5~1.5 mm, d2 = 0.5~1.5 mm, h= 0.5~1.5mm, ? = 10~30 degrees. The fully developed flow and thermal fields are predicted using the finite volume method and the optimization is carried out by means of the multi-objective genetic algorithm that is widely used in the constrained nonlinear optimization problem.
Abstract: Heating systems are a necessity for regions which
brace extreme cold weather throughout the year. To maintain a comfortable temperature inside a given place, heating systems
making use of- Hydronic boilers- are used. The principle of a single
pipe system serves as a base for their working. It is mandatory for these heating systems to control the room temperature, thus
maintaining a warm environment. In this paper, the concept of regulation of the room temperature over a wide range is established
by using an Adaptive Fuzzy Controller (AFC). This fuzzy controller automatically detects the changes in the outside temperatures and
correspondingly maintains the inside temperature to a palatial value. Two separate AFC's are put to use to carry out this function: one to
determine the quantity of heat needed to reach the prospective temperature required and to set the desired temperature; the other to control the position of the valve, which is directly proportional to the
error between the present room temperature and the user desired temperature. The fuzzy logic controls the position of the valve as per
the requirement of the heat. The amount by which the valve opens or closes is controlled by 5 knob positions, which vary from minimum to maximum, thereby regulating the amount of heat flowing through the valve. For the given test system data, different de-fuzzifier
methods have been implemented and the results are compared. In order to validate the effectiveness of the proposed approach, a fuzzy controller has been designed by obtaining a test data from a real time
system. The simulations are performed in MATLAB and are verified with standard system data. The proposed approach can be implemented for real time applications.
Abstract: Non-uniform current distribution in polymer
electrolyte membrane fuel cells results in local over-heating,
accelerated ageing, and lower power output than expected. This
issue is very critical when fuel cell experiences water flooding. In
this work, the performance of a PEM fuel cell is investigated under
cathode flooding conditions. Two-dimensional partially flooded
GDL models based on the conservation laws and electrochemical
relations are proposed to study local current density distributions
along flow fields over a wide range of cell operating conditions.
The model results show a direct association between cathode inlet
humidity increases and that of average current density but the
system becomes more sensitive to flooding. The anode inlet
relative humidity shows a similar effect. Operating the cell at
higher temperatures would lead to higher average current densities
and the chance of system being flooded is reduced. In addition,
higher cathode stoichiometries prevent system flooding but the
average current density remains almost constant. The higher anode
stoichiometry leads to higher average current density and higher
sensitivity to cathode flooding.
Abstract: This paper was to study the clothes dryer using waste
heat from a split type air conditioner with a capacity of 12,648 btu/h.
The drying chamber had a minimum cross section area with the size
of 0.5 x 1.0 m2. The chamber was constructed by sailcloth and was
inside folded with aluminium foil. Then, it was connected to the
condensing unit of an air conditioner. The experiment was carried out
in two aspects which were the clothes drying with and without
auxiliary fan unit. The results showed that the drying rate of clothes
in the chamber installed with and without auxiliary fan unit were
2.26 and 1.1 kg/h, respectively. In case of the chamber installed with
a auxiliary fan unit, the additional power of 0.011 kWh was
consumed and the drying rate was higher than that of clothes drying
without auxiliary fan unit. Without auxiliary fan unit installation, no
energy was required but there was a portion of hot air leaks away
through the punctured holes at the wall of the drying chamber, hence
the drying rate was dropped below. The drying rate of clothes drying
using waste heat was higher than natural indoor drying and
commercial dryer which their drying rate were 0.17 and 1.9 kg/h,
respectively. It was noted that the COP of the air conditioner did not
change during the operating of clothes drying.
Abstract: The paper presents the results of microhardness and
microstructure of low carbon steel surface melted using carbon
dioxide laser with a wavelength of 10.6μm and a maximum output
power of 2000W. The processing parameters such as the laser power,
and the scanning rate were investigated in this study. After surface
melting two distinct regions formed corresponding to the melted zone
MZ, and the heat affected zone HAZ. The laser melted region
displayed a cellular fine structures while the HAZ displayed
martensite or bainite structure. At different processing parameters,
the original microstructure of this steel (Ferrite+Pearlite) has been
transformed to new phases of martensitic and bainitic structures. The
fine structure and the high microhardness are evidence of the high
cooling rates which follow the laser melting. The melting pool and
the transformed microstructure in the laser surface melted region of
carbon steel showed clear dependence on laser power and scanning
rate.
Abstract: Nowadays, desalination of salt water is considered an important industrial process. In many parts of the world, particularly in the gulf countries, the multi-stage flash (MSF) water desalination has an essential contribution in the production of fresh water. In this study, a simple mathematical model is defined to design a MSF desalination system and the feasibility of using the MSF desalination process in proximity of a 42 MW power plant is investigated. This power plant can just provide 10 ton/h superheated steam from low pressure (LP) section of heat recovery steam generator (HRSG) for thermal desalting system. The designed MSF system with gained output ratio (GOR) of 10.3 has 24 flashing stages and can produce 2480 ton/d of fresh water. The expected performance characteristics of the designed MSF desalination plant are determined. In addition, the effect of motive water pressure on the amount of non-condensable gases removed by water jet vacuum pumps is investigated.
Abstract: The present study addresses problems and solutions
related to new functional food production. Wheat (Triticum aestivum
L) bran obtained from industrial mill company “Dobeles
dzirnavieks”, was used to investigate them as raw material like
nutrients for Bifidobacterium lactis Bb-12. Enzymatic hydrolysis of
wheat bran starch was carried out by α-amylase from Bacillus
amyloliquefaciens (Sigma Aldrich). The Viscozyme L purchased
from (Sigma Aldrich) were used for reducing released sugar.
Bifidibacterium lactis Bb-12 purchased from (Probio-Tec® CHR
Hansen) was cultivated in enzymatically hydrolysed wheat bran
mash. All procedures ensured the number of active Bifidobacterium
lactis Bb-12 in the final product reached 105 CFUg-1. After enzymatic
and bacterial fermentations sample were freeze dried for analysis of
chemical compounds. All experiments were performed at Faculty of
Food Technology of Latvia University of Agriculture in January-
March 2013. The obtained results show that both types of wheat bran
(enzymatically treated and non-treated) influenced the fermentative
activity and number of Bifidibacterium lactis Bb-12 viable in wheat
bran mash. Amount of acidity strongly increase during the wheat
bran mash fermentation. The main objective of this work was to
create low-energy functional enzymatically and bacterially treated
food from wheat bran using enzymatic hydrolysis of carbohydrates
and following cultivation of Bifidobacterium lactis Bb-12.
Abstract: In this work, simulation algorithms for contact drying
of agitated particulate materials under vacuum and at atmospheric
pressure were developed. The implementation of algorithms gives a
predictive estimation of drying rate curves and bulk bed temperature
during contact drying. The calculations are based on the penetration
model to describe the drying process, where all process parameters
such as heat and mass transfer coefficients, effective bed properties,
gas and liquid phase properties are estimated with proper
correlations. Simulation results were compared with experimental
data from the literature. In both cases, simulation results were in good
agreement with experimental data. Few deviations were identified
and the limitations of the predictive capabilities of the models are
discussed. The programs give a good insight of the drying behaviour
of the analysed powders.
Abstract: The study of the fouling deposition of pink guava
juice (PGJ) is relatively new research compared to milk fouling
deposit. In this work, a new experimental set-up was developed to
imitate the fouling formation in heat exchanger, namely a continuous
flow experimental set-up heat exchanger. The new experimental setup
was operated under industrial pasteurization temperature of PGJ,
which was at 93°C. While the flow rate and pasteurization period
were based on the experimental capacity, which were 0.5 and 1
liter/min for the flow rate and the pasteurization period was set for 1
hour. Characterization of the fouling deposit was determined by
using various methods. Microstructure of the deposits was carried
out using ESEM. Proximate analyses were performed to determine
the composition of moisture, fat, protein, fiber, ash and carbohydrate
content. A study on the hardness and stickiness of the fouling deposit
was done using a texture analyzer. The presence of seedstone in pink
guava juice was also analyzed using a particle analyzer. The findings
shown that seedstone from pink guava juice ranging from 168 to
200μm and carbohydrate was found to be a major composition
(47.7% of fouling deposit consists of carbohydrate). Comparison
between the hardness and stickiness of the deposits at two different
flow rates showed that fouling deposits were harder and denser at
higher flow rate. Findings from this work provide basis knowledge
for further study on fouling and cleaning of PGJ.
Abstract: The compression-absorption heat pump (C-A HP), one
of the promising heat recovery equipments that make process hot
water using low temperature heat of wastewater, was evaluated by
computer simulation. A simulation program was developed based on
the continuity and the first and second laws of thermodynamics. Both
the absorber and desorber were modeled using UA-LMTD method. In
order to prevent an unfeasible temperature profile and to reduce
calculation errors from the curved temperature profile of a mixture,
heat loads were divided into lots of segments. A single-stage
compressor was considered. A compressor cooling load was also
taken into account. An isentropic efficiency was computed from the
map data. Simulation conditions were given based on the system
consisting of ordinarily designed components. The simulation results
show that most of the total entropy generation occurs during the
compression and cooling process, thus suggesting the possibility that
system performance can be enhanced if a rectifier is introduced.
Abstract: The increasing demand for sufficient and clean
energy forces industrial and service companies to align their strategies towards efficient consumption. This trend refers also to the
residential building sector. There, large amounts of energy consumption are caused by house and facility heating. Many of the
operated hot water heating systems lack hydraulic balanced working
conditions for heat distribution and –transmission and lead to
inefficient heating. Through hydraulic balancing of heating systems,
significant energy savings for primary and secondary energy can be
achieved. This paper addresses the use of KNX-technology (Smart
Buildings) in residential buildings to ensure a dynamic adaption of
hydraulic system's performance, in order to increase the heating
system's efficiency. In this paper, the procedure of heating system
segmentation into hydraulically independent units (meshes) is
presented. Within these meshes, the heating valve are addressed and
controlled by a central facility server. Feasibility criteria towards
such drivers will be named. The dynamic hydraulic balance is
achieved by positioning these valves according to heating loads, that
are generated from the temperature settings in the corresponding
rooms. The energetic advantages of single room heating control
procedures, based on the application FacilityManager, is presented.
Abstract: The reliable results of an insulated oval duct
considering heat radiation are obtained basing on accurate oval
perimeter obtained by integral method as well as one-dimensional
Plane Wedge Thermal Resistance (PWTR) model. This is an extension
study of former paper of insulated oval duct neglecting heat radiation.
It is found that in the practical situations with long-short-axes ratio a/b
4.5% while t/R2
Abstract: For fire safety purposes, the fire resistance and the
structural behavior of reinforced concrete members are assessed to
satisfy specific fire performance criteria. The available prescribed
provisions are based on standard fire load. Under various fire
scenarios, engineers are in need of both heat transfer analysis and
structural analysis. For heat transfer analysis, the study proposed a
modified finite difference method to evaluate the temperature profile
within a cross section. The research conducted is limited to concrete
sections exposed to a fire on their one side. The method is based on
the energy conservation principle and a pre-determined power
function of the temperature profile. The power value of 2.7 is found
to be a suitable value for concrete sections. The temperature profiles
of the proposed method are only slightly deviate from those of the
experiment, the FEM and the FDM for various fire loads such as
ASTM E 119, ASTM 1529, BS EN 1991-1-2 and 550 oC. The
proposed method is useful to avoid incontinence of the large matrix
system of the typical finite difference method to solve the
temperature profile. Furthermore, design engineers can simply apply
the proposed method in regular spreadsheet software.
Abstract: Shape memory alloy (SMA) actuators have found a
wide range of applications due to their unique properties such as high
force, small size, lightweight and silent operation. This paper presents
the development of compact (SMA) actuator and cooling system in
one unit. This actuator is developed for multi-fingered hand. It
consists of nickel-titanium (Nitinol) SMA wires in compact forming.
The new arrangement insulates SMA wires from the human body by
housing it in a heat sink and uses a thermoelectric device for rejecting
heat to improve the actuator performance. The study uses
optimization methods for selecting the SMA wires geometrical
parameters and the material of a heat sink. The experimental work
implements the actuator prototype and measures its response.
Abstract: As a simple to method estimate the plant heating energy
capacity of an apartment complex, a new load calculation method has
been proposed. The method which can be called as unit building
method, predicts the heating load of the entire complex instead of
summing up that of each apartment belonging to complex.
Comparison of the unit heating load for various floor sizes between the
present method and conventional approach shows a close agreement
with dynamic load calculation code. Some additional calculations are
performed to demonstrate it-s application examples.
Abstract: This paper presents a NDT by infrared thermography with excitation CO2 Laser, wavelength of 10.6 μm. This excitation is the controllable heating beam, confirmed by a preliminary test on a wooden plate 1.2 m x 0.9 m x 1 cm. As the first practice, this method is applied to detecting the defect in CFRP heated by the Laser 300 W during 40 s. Two samples 40 cm x 40 cm x 4.5 cm are prepared, one with defect, another one without defect. The laser beam passes through the lens of a deviation device, and heats the samples placed at a determinate position and area. As a result, the absence of adhesive can be detected. This method displays prominently its application as NDT with the composite materials. This work gives a good perspective to characterize the laser beam, which is very useful for the next detection campaigns.
Abstract: Dual phase steels (DPS)s have a microstructure
consisting of a hard second phase called Martensite in the soft Ferrite
matrix. In recent years, there has been interest in dual-phase steels,
because the application of these materials has made significant usage;
particularly in the automotive sector Composite microstructure of
(DPS)s exhibit interesting characteristic mechanical properties such
as continuous yielding, low yield stress to tensile strength
ratios(YS/UTS), and relatively high formability; which offer
advantages compared with conventional high strength low alloy
steels(HSLAS). The research dealt with the characterization of
damage in (DPS)s. In this study by review the mechanisms of failure
due to volume fraction of martensite second phase; a new method is
introduced to identifying the mechanisms of failure in the various
phases of these types of steels. In this method the acoustic emission
(AE) technique was used to detect damage progression. These failure
mechanisms consist of Ferrite-Martensite interface decohesion and/or
martensite phase fracture. For this aim, dual phase steels with
different volume fraction of martensite second phase has provided by
various heat treatment methods on a low carbon steel (0.1% C), and
then AE monitoring is used during tensile test of these DPSs. From
AE measurements and an energy ratio curve elaborated from the
value of AE energy (it was obtained as the ratio between the strain
energy to the acoustic energy), that allows detecting important
events, corresponding to the sudden drops. These AE signals events
associated with various failure mechanisms are classified for ferrite
and (DPS)s with various amount of Vm and different martensite
morphology. It is found that AE energy increase with increasing Vm.
This increasing of AE energy is because of more contribution of
martensite fracture in the failure of samples with higher Vm. Final
results show a good relationship between the AE signals and the
mechanisms of failure.
Abstract: The flow and heat transfer mechanism in convex
corrugated tubes have been investigated through numerical
simulations in this paper. Two kinds of tube types named as symmetric
corrugated tube (SCT) and asymmetric corrugated tube (ACT) are
modeled and studied numerically based on the RST model. The
predictive capability of RST model is examined in the corrugation wall
in order to check the reliability of RST model under the corrugation
wall condition. We propose a comparison between the RST modelling
the corrugation wall with existing direct numerical simulation of Maaß
C and Schumann U [14]. The numerical results pressure coefficient at
different profiles between RST and DNS are well matched. The
influences of large corrugation tough radii to heat transfer and flow
characteristic had been considered. Flow and heat transfer comparison
between SCT and ACT had been discussed. The numerical results
show that ACT exhibits higher overall heat transfer performance than
SCT.