Abstract: Nowadays, solar energy is used for energy purposes such as the use of thermal energy for domestic, industrial and power applications, as well as the conversion of the sunlight into electricity by photovoltaic cells. In this study, the thermodynamic simulation of the solar Rankin cycle with phase change material (paraffin) was first studied. Then energy and exergy analyses were performed. For optimization, a single and multi-objective genetic optimization algorithm to maximize thermal and exergy efficiency was used. The parameters discussed in this paper included the effects of input pressure on turbines, input mass flow to turbines, the surface of converters and collector angles on thermal and exergy efficiency. In the organic Rankin cycle, where solar energy is used as input energy, the fluid selection is considered as a necessary factor to achieve reliable and efficient operation. Therefore, silicon oil is selected for a high-temperature cycle and water for a low-temperature cycle as an operating fluid. The results showed that increasing the mass flow to turbines 1 and 2 would increase thermal efficiency, while it reduces and increases the exergy efficiency in turbines 1 and 2, respectively. Increasing the inlet pressure to the turbine 1 decreases the thermal and exergy efficiency, and increasing the inlet pressure to the turbine 2 increases the thermal efficiency and exergy efficiency. Also, increasing the angle of the collector increased thermal efficiency and exergy. The thermal efficiency of the system was 22.3% which improves to 33.2 and 27.2% in single-objective and multi-objective optimization, respectively. Also, the exergy efficiency of the system was 1.33% which has been improved to 1.719 and 1.529% in single-objective and multi-objective optimization, respectively. These results showed that the thermal and exergy efficiency in a single-objective optimization is greater than the multi-objective optimization.
Abstract: In this study, a form-stable composite Paraffin/Nanoclay (PA-NC) has been prepared by absorbing PA into porous particles of NC to be used for low-temperature latent heat thermal energy storage. The leakage test shows that the maximum mass fraction of PA that can be incorporated in NC without leakage is 60 wt.%. Differential scanning calorimetry (DSC) has been used to measure the thermal properties of the PA and PA-NC both before and after incorporation in plasterboard (PL). The mechanical performance of the samples has been evaluated in flexural mode. The thermal energy storage performance has been studied using a small test chamber (100 mm × 100 mm × 100 mm) made from 10 mm thick PL and measuring the temperatures using thermocouples. The flammability of the PL+PL-NC has been discussed using a cone calorimeter. The results indicate that the form composite PA has good potential for use as thermal energy storage materials in building applications.
Abstract: Fabric as the first and most common layer that is in permanent contact with human skin is a very good interface to provide coverage, as well as heat and cold insulation. Phase change materials (PCMs) are organic and inorganic compounds which have the capability of absorbing and releasing noticeable amounts of latent heat during phase transitions between solid and liquid phases at a low temperature range. PCMs come across phase changes (liquid-solid and solid-liquid transitions) during absorbing and releasing thermal heat; so, in order to use them for a long time, they should have been encapsulated in polymeric shells, so-called microcapsules. Microencapsulation and nanoencapsulation methods have been developed in order to reduce the reactivity of a PCM with outside environment, promoting the ease of handling, decreasing the diffusion and evaporation rates. Methods of incorporation of PCMs in textiles such as electrospinning and determining thermal properties had been summarized. Paraffin waxes catch a lot of attention due to their high thermal storage density, repeatability of phase change, thermal stability, small volume change during phase transition, chemical stability, non-toxicity, non-flammability, non-corrosive and low cost and they seem to play a key role in confronting with climate change and global warming. In this article, we aimed to review the researches concentrating on the characteristics of PCMs and new materials and methods of microencapsulation.
Abstract: Melting of Paraffin Wax (P116) dispersed with Al2O3 nanoparticles in a rectangular latent heat storage unit (LHSU) is numerically investigated. The storage unit consists of a number of vertical and identical plates of nano-enhanced phase change material (NEPCM) separated by rectangular channels in which heat transfer fluid flows (HTF: Water). A two dimensional mathematical model is considered to investigate numerically the heat and flow characteristics of the LHSU. The melting problem was formulated using the enthalpy porosity method. The finite volume approach was used for solving equations. The effects of nanoparticles’ volumetric fraction and the Reynolds number on the thermal performance of the storage unit were investigated.
Abstract: Solar energy is available abundantly in the world, but it is not continuous and its intensity also varies with time. Due to above reason the acceptability and reliability of solar based thermal system is lower than conventional systems. A properly designed heat storage system increases the reliability of solar thermal systems by bridging the gap between the energy demand and availability. In the present work, two dimensional numerical simulation of the melting of heat storage material is presented in the horizontal annulus of double pipe latent heat storage system. Longitudinal fins were used as a thermal conductivity enhancement. Paraffin wax was used as a heat-storage or phase change material (PCM). Constant wall temperature is applied to heat transfer tube. Presented two-dimensional numerical analysis shows the movement of melting front in the finned cylindrical annulus for analyzing the thermal behavior of the system during melting.
Abstract: Introduction: Craniopharyngiomas (CPs) are rare epithelial tumors located mainly in the sellar/parasellar region. CPs have been classified histopathologically, genetically, clinically and prognostically into two distinctive subtypes: adamantinomatous and papillary variants. Aim: To examine the pattern of expression of both the β-catenin and epidermal growth factor receptor (EGFR) in surgically resected samples of adamantinomatous CP, and to asses for the possibility of using anti-EGFR in the management of ACP patients. Materials and methods: β-catenin and EGFR immunostaining was performed on paraffin-embedded tissue sections of 18 ACP cases. Result: 17 out of 18 cases (94%) of ACP exhibited strong nuclear/cytoplasmic expression of β-catenin, 15 (83%) of APC cases were positive for EGFR. Conclusion: Nuclear accumulation of β-catenin is a diagnostic hallmark of ACP. EGFR positivity in most cases of ACP could qualify the use of anti-EGFR therapy.
Abstract: Hybrid propulsion combines beneficial properties of both solid and liquid rockets, such as multiple restarts, throttability as well as simplicity and reduced costs. A nitrous oxide (N2O)/paraffin-based hybrid rocket engine demonstrator is currently under development at the Italian Aerospace Research Center (CIRA) within the national research program HYPROB, funded by the Italian Ministry of Research. Nitrous oxide belongs to the class of self-pressurizing propellants that exhibit a high vapor pressure at standard ambient temperature. This peculiar feature makes those fluids very attractive for space rocket applications because it avoids the use of complex pressurization systems, leading to great benefits in terms of weight savings and reliability. To avoid feed-system-coupled instabilities, the phase change is required to occur through the injectors. In this regard, the oxidizer is stored in liquid condition while target chamber pressures are designed to lie below vapor pressure. The consequent cavitation and flash vaporization constitute a remarkably complex phenomenology that arises great modelling challenges. Thus, it is clear that the design of the injection system is fundamental for the full exploitation of hybrid rocket engine throttability. The Analytical Hierarchy Process has been used to select the injection architecture as best compromise among different design criteria such as functionality, technology innovation and cost. The impossibility to use engineering simplified relations for the dimensioning of the injectors led to the needs of applying a numerical approach based on OpenFOAM®. The numerical tool has been validated with selected experimental data from literature. Quantitative, as well as qualitative comparisons are performed in terms of mass flow rate and pressure drop across the injector for several operating conditions. The results show satisfactory agreement with the experimental data. Modeling assumptions, together with their impact on numerical predictions are discussed in the paper. Once assessed the reliability of the numerical tool, the injection plate has been designed and sized to guarantee the required amount of oxidizer in the combustion chamber and therefore to assure high combustion efficiency. To this purpose, the plate has been designed with multiple injectors whose number and diameter have been selected in order to reach the requested mass flow rate for the two operating conditions of maximum and minimum thrust. The overall design has been finally verified through three-dimensional computations in cavitating non-reacting conditions and it has been verified that the proposed design solution is able to guarantee the requested values of mass flow rates.
Abstract: The aim of the study is to improve the understanding
of latent and sensible thermal energy storage within a paraffin wax
media by an array of cylindrical tubes arranged both in in-line and
staggered layouts. An analytical and experimental study is carried out
in a horizontal shell-and-tube type system during melting process.
Pertamina paraffin-wax was used as a phase change material (PCM),
while the tubes are embedded in the PCM. From analytical study we
can obtain the useful information in designing a thermal energy
storage such as: the motion of interface, amount of material melted at
any time in the process, and the heat storage characteristic during
melting. The use of staggered tubes is proposed compared to in-line
layout in a heat exchanger as thermal storage. The experimental study
is used to verify the validity of the analytical predictions. From the
comparisons, the analytical and experimental data are in a good
Abstract: Paraffinic oils were submitted to microbial action. The
microorganisms consisted of bacteria of the genera Pseudomonas sp.
and Bacillus lincheniforms. The alterations in interfacial tension were
determined using a tensometer and applying the hanging drop
technique at room temperature (299 K ±275 K). The alteration in the
constitution of the paraffins was evaluated by means of gas
chromatography. The microbial activity was observed to reduce
interfacial tension by 54 to 78%, as well as consuming the paraffins
C19 to C29 and producing paraffins C36 to C44. The LIFirr technique
made it possible to determine the microbial action quickly.
Abstract: 15 strains of oil-destructing microorganisms were
isolated from oil polluted soil of Western Kazakhstan. Strains 2-A
and 41-3 with the highest oil-destructing activities were chosen from
them. It was shown that these strains oxidized n-alkanes very well,
but isoalkanes, isoparaffin, cycloparaffin and heavy aromatic
compounds were destructed very slowly. These both strains were
tested as preparations for bioremediation of oil-polluted soil in model
and field experiments. The degree of utilizing of soil oil by this
preparation was 79-84 % in field experiments.
Abstract: An investigation of noise in a micro stepping motor is
considered to study in this article. Because of the trend towards higher
precision and more and more small 3C (including Computer,
Communication and Consumer Electronics) products, the micro
stepping motor is frequently used to drive the micro system or the
other 3C products. Unfortunately, noise in a micro stepped motor is
too large to accept by the customs. To depress the noise of a micro
stepped motor, the dynamic characteristics in this system must be
studied. In this article, a Visual Basic (VB) computer program speed
controlled micro stepped motor in a digital camera is investigated.
Karman KD2300-2S non-contract eddy current displacement sensor,
probe microphone, and HP 35670A analyzer are employed to analyze
the dynamic characteristics of vibration and noise in a motor. The
vibration and noise measurement of different type of bearings and
different treatment of coils are compared. The rotating components,
bearings, coil, etc. of the motor play the important roles in producing
vibration and noise. It is found that the noise will be depressed about
3~4 dB and 6~7 dB, when substitutes the copper bearing with plastic
one and coats the motor coil with paraffin wax, respectively.
Abstract: It is shown that a modified UNIFAC model can be
applied to predict solubility of hydrocarbon gases and vapors in
hydrocarbon solvents. Very good agreement with experimental data
has been achieved. In this work we try to find best way for predicting
dimethyl ether solubility in liquid paraffin by using group
Abstract: The quantum mechanics simulation was applied for
calculating the interaction force between 2 molecules based on atomic level. For the simple extractive distillation system, it is ternary
components consisting of 2 closed boiling point components (A,lower boiling point and B, higher boiling point) and solvent (S). The
quantum mechanics simulation was used to calculate the intermolecular force (interaction force) between the closed boiling
point components and solvents consisting of intermolecular between
A-S and B-S.
The requirement of the promising solvent for extractive distillation
is that solvent (S) has to form stronger intermolecular force with only
one component than the other component (A or B). In this study, the
systems of aromatic-aromatic, aromatic-cycloparaffin, and paraffindiolefin
systems were selected as the demonstration for solvent
selection. This study defined new term using for screening the solvents called relative interaction force which is calculated from the
quantum mechanics simulation. The results showed that relative
interaction force gave the good agreement with the literature data
(relative volatilities from the experiment). The reasons are discussed. Finally, this study suggests that quantum mechanics results can improve the relative volatility estimation for screening the solvents leading to reduce time and money consuming
Abstract: The problem on the conservation programme of the Royal Thai Navy Sea Turtle Nursery, Phang-nga Province, Thailand is high mortality rate of juvenile green sea turtle (Cheloniamydas) on nursing period. So, during May to October 2012, postmortem examinations of juvenile green sea turtle were performed to determine the causes of dead. Fresh tissues of postmortem of 15 juvenile green sea turtles (1-3 months old) were investigated using paraffin section technique. The results showed normal ultrastructure of all tissue organs. These instances reviewed the health and stability of the environments in which juvenile green sea turtles live and concern for the survival rate. The present article also provides guidance for a review of the biology, guidelines for appropriate postmortem tissue, normal histology and sampling collection and procedures. The data also provides information for conservation of this endangered species in term of acknowledging and encouraging people to protect the animals and their habitats in nature.
Abstract: Modeling of a heterogeneous industrial fixed bed
reactor for selective dehydrogenation of heavy paraffin with Pt-Sn-
Al2O3 catalyst has been the subject of current study. By applying
mass balance, momentum balance for appropriate element of reactor
and using pressure drop, rate and deactivation equations, a detailed
model of the reactor has been obtained. Mass balance equations have
been written for five different components. In order to estimate
reactor production by the passage of time, the reactor model which is
a set of partial differential equations, ordinary differential equations
and algebraic equations has been solved numerically.
Paraffins, olefins, dienes, aromatics and hydrogen mole percent as
a function of time and reactor radius have been found by numerical
solution of the model. Results of model have been compared with
industrial reactor data at different operation times. The comparison
successfully confirms validity of proposed model.
Abstract: In the present study, a procedure was developed to
determine the optimum reaction rate constants in generalized
Arrhenius form and optimized through the Nelder-Mead method. For
this purpose, a comprehensive mathematical model of a fixed bed
reactor for dehydrogenation of heavy paraffins over Pt–Sn/Al2O3
catalyst was developed. Utilizing appropriate kinetic rate expressions
for the main dehydrogenation reaction as well as side reactions and
catalyst deactivation, a detailed model for the radial flow reactor was
obtained. The reactor model composed of a set of partial differential
equations (PDE), ordinary differential equations (ODE) as well as
algebraic equations all of which were solved numerically to
determine variations in components- concentrations in term of mole
percents as a function of time and reactor radius. It was demonstrated
that most significant variations observed at the entrance of the bed
and the initial olefin production obtained was rather high. The
aforementioned method utilized a direct-search optimization
algorithm along with the numerical solution of the governing
differential equations. The usefulness and validity of the method was
demonstrated by comparing the predicted values of the kinetic
constants using the proposed method with a series of experimental
values reported in the literature for different systems.
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: Performance of a cobalt doped sol-gel derived silica (Co/SiO2) catalyst for Fischer–Tropsch synthesis (FTS) in slurryphase reactor was studied using paraffin wax as initial liquid media. The reactive mixed gas, hydrogen (H2) and carbon monoxide (CO) in a molar ratio of 2:1, was flowed at 50 ml/min. Braunauer-Emmett- Teller (BET) surface area and X-ray diffraction (XRD) techniques were employed to characterize both the specific surface area and crystallinity of the catalyst, respectively. The reduction behavior of Co/SiO2 catalyst was investigated using the Temperature Programmmed Reduction (TPR) method. Operating temperatures were varied from 493 to 533K to find the optimum conditions to maximize liquid fuels production, gasoline and diesel.