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A series of experimental investigations was carried out to study the kinetics of spontaneous heterogeneous boiling-up of superheated n-pentane in two glass tubes. It was determined that the isobaric temperature dependences of the mean lifetime of the superheated liquid that were measured under similar conditions have threshold values in the temperature ranges of 100–115, 120–125, and 130–140°C. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work reports the nucleate boiling heat transfer characteristics of n-pentane on smooth and enhanced surfaces. Surface modifications were carried out on stainless steel surfaces by fabricating microholes of diameter between 0.3 and 0.7 mm arrays using electric discharge machining. Pool boiling experiments were carried out at normal atmospheric pressure. Experiments have been performed for applied effective heat flux range between 1 and 10 W cm−2. An enhancement of 20–45% in heat transfer coefficient was observed on the enhanced surface compared to the smooth surface. The heat transfer improvement in the enhanced surface can be attributed to more active nucleation sites, better rewetting phenomenon, and favorable bubble growth and release mechanism. Further changing the material from steel to brass enhances the heat transfer coefficient by 20%. This will be a viable option as a cooling technology for high-power electronic industries. [ABSTRACT FROM AUTHOR]

The interaction of recirculated NOX with two-stage fuels in the early combustion process is not fully understood, especially at lower temperatures. Recently developed kinetic combustion models try to reproduce these interactions. To validate and improve these new models, accurate quantitative measurements of temperature in the combustion process are necessary. Previous works used Rayleigh or LIF techniques and have not reached an accuracy appropriate for the kinetic models. The present work demonstrates the feasibility of 1D spatially-resolved temperature measurements in a rapid compression machine with Raman scattering for the first time. The temperature data is measured with high precision during the first stage ignition of n-pentane as a two-stage fuel. Additionally, the temperature data is needed to determine possible NO detection limits. Therefore, the influence on combustion temperatures from NOX-doping are compared with undoped gas mixtures is determined by spontaneous Raman scattering of N2 excited by a KrF* excimer laser. The results show that spatially resolved N2-Raman thermometry is feasible with a precision of approximately 3 % by investigating 30 averaged shots. The measured temperature profile in the first stage reveals a remarkable temperature difference between the edges and the inner area of the combustion volume due to differences in the reactivity, which is affected by chemistry and heat loss. Additionally, the NO detection limit is determined to be 30 ppm when averaging 10 single shots during an NO-doped N2 mixture.

The boiling-up kinetics of superheated n-pentane in a glass tube has been studied by means of a high-speed video filming and a fast-acting pressure sensor. The top of the tube is sealed. It is shown that, as the threshold temperature is approached, the boiling-up of a superheated liquid is accompanied by significant pressure jumps and oscillations, whereas the formation of a vapor film can begin from self-organization in the near-wall layer of the liquid. [ABSTRACT FROM AUTHOR]

Hydrogen can be blended with other surrogate fuels to avoid its hazard as a highly flammable and explosive gas. The effect of hydrogen addition on the ignition delay times of n -pentane, 3-pentanone, and 1-pentene was investigated by measuring the ignition delay times in a rapid compression machine. The experiments were performed at pressures of 10, 15, and 20 bar, equivalence ratios 0.5 and 1 and for temperatures ranging from 650 to 970 K. The molar ratios of hydrogen in the fuel mixtures were 0, 25 and 50%. The experimental data were simulated using recent models from literature, yielding good agreement. The overall observations conclude to a minor effect of hydrogen addition in the case of n- pentane and 3-pentanone, resulting in a decrease of the reactivity when the mole fraction of hydrogen increases. Hydrogen does however not impact the ignition delay times of 1-pentene significantly. Kinetic analysis is performed to shed light into the processes responsible for this phenomenon. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effect of Gelatin on the solubility and diffusivity of normal pentane in poly (vinyl alcohol) (PVA)/Gelatin (Gel) blends. The processibility of PVA was enhanced after adding the gelatin as plasticizer to PVA which gelatin could extend the process widow of PVA with destroying the hydrogen bonding of the polymer matrix. Therefore, the PVA/Gel blends with different concentrations were prepared by simple solution-casting method. The intermolecular suitable interactions in PVA/Gel blends were confirmed using the FTIR, XRD and SEM/EDX analyzes. In the following, the effect of various factors like temperature, pressure and gelatin content on the thermodynamic parameters like specific free volume, solubility and diffusivity was investigated. It was shown that there was a relationship between the specific free volume of the blends with the solubility and diffusivity of normal pentane in blends. The specific free volume of blends was determined by applying the PVT data and the Sanchez-Lacombe (SL) equation of state, in which it was enhanced with increasing of the temperature and gelatin in blends, respectively. Also, the solubility and diffusivity of normal pentane in samples were determined by the magnetic suspension balance (MSB) system. The results presented that the solubility and diffusivity of n-pentane improved with increasing of gelatin content in blend, pressure and temperature decrement, respectively. [ABSTRACT FROM AUTHOR]

Flow boiling is a complex process but very efficient for thermal management in different sectors; enhancing flow boiling heat transfer properties is a research field of great interest. This study proposes the use of various nanomaterials, carbon-based materials, and metal oxides; in n-pentane as a hydrocarbon-based refrigerant to enhance the flow boiling heat transfer coefficient. This thermal property has been experimentally evaluated using a vertical evaporation device of glass with an internal diameter of 20 mm. The results have shown that proposed nanomaterials dispersion in n-pentane has a limited effect on the thermophysical properties and is conditioned by their dispersibility but promotes a significant increment of pentane heat transfer coefficient (h), increasing the overall heat transfer coefficient (U) of the evaporator. The enhanced heat transfer performance is attributed to the behavior of nanoparticles under working conditions and their interaction with the working surface, promoting a higher generation of nucleation sites. The observed behavior suggests a heat transfer mechanism transition from forced convection to nucleate heat transfer, supported by visual observations. [ABSTRACT FROM AUTHOR]

When converting C5 hydrocarbons to light olefins by catalytic pyrolysis, the generation of low valueadded methane will affect the atomic utilization efficiency of C5 hydrocarbons. To improve the atomic utilization efficiency, different generation pathways of light olefins and methane in the catalytic pyrolysis of C5 hydrocarbons were analyzed, and the effects of reaction conditions and zeolite types were investigated. Results showed that light olefins were mainly formed by breaking the C2-C3 bond in the middle position, while methane was formed by breaking the C1-C2 bond at the end. Meanwhile, it was discovered that the hydrogen transfer reaction could be reduced by about 90% by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity (WHSV) and high temperature operations, thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%, respectively. Moreover, the fraction ratio of terminal C1-C2 bond cleavage was reduced, which would reduce the selectivity of methane to 6.63% and 1.83%. Therefore, zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHSV will be conducive to maximize light olefins and to decrease methane. [ABSTRACT FROM AUTHOR]

[Display omitted] • The oxidation reaction mechanism of n-pentane was investigated. • The n-pentane oxidation reaction process was controlled by ring-closing and H-atom transfer reactions. • Thirteen reaction pathways initiated by the addition of oxygen to the active site of the n-pentyl radical were elucidated. The oxidation reaction mechanism of n-pentane is investigated using density functional theory and transition state theory as a case study to elucidate the combustion characteristics of liquids with low boiling points. This study divides the oxidation reaction of n-pentane into four steps. First, n-pentane decomposes to form n-pentyl radicals C 5 H 11 and H, CH 3 and C 4 H 9 , and C 2 H 5 and C 3 H 7 radicals. Second, n-pentane primarily undergoes H-abstraction reactions with H, CH 3 , C 2 H 5 , and C 3 H 7 radicals to form the C 5 H 11 radicals. Subsequently, C 5 H 11 radicals react with O 2 in an addition reaction to form n-pentyl peroxy radicals ROO. Finally, ROO radical undergoes internal H-atom transfer to form hydroperoxy pentyl radicals QOOH, which then undergoes cyclization and bond scission to produce cyclic ethers, alkenes, aldehydes, OH radicals, and HO 2 radicals. Results indicate that n-pentane readily decomposes into C 2 H 5 and C 3 H 7 radicals, with a bond dissociation energy of 367.1 KJ/mol. The H-abstraction reactions involving H and CH 3 radicals have the fastest rates, which require the lowest energy barriers of 21.6 and 41.9 KJ/mol, respectively. The reaction between C 5 H 11 and O 2 is a barrierless addition reaction. The oxidation of n-pentane, which leads to the formation of 2-methyloxirane and OH radicals, exhibits the fastest reaction rate. [ABSTRACT FROM AUTHOR]

The effect of temperature and pressure on the nucleation of the vapor phase and the velocity of the vapor front in the initial stage of activated boiling-up of n-pentane on the surface of a quartz fiber was studied. Using a developed approach combining the “pump-probe” and laser Doppler velocimetry methods, this velocity was tracked in the course of sequential change in the degree of superheating with respect to the liquid–vapor equilibrium line. The studied interval according to the degree of superheating was 40–100 °C (at atmospheric pressure). In order to spatiotemporally localize the process, the activation of boiling-up at the end of the light guide was applied using a short nanosecond laser pulse. A spatial locality of measurements was achieved in units of micrometers, along with a time localization at the level of nanoseconds. An increase in temperature at a given pressure was found to lead to an increase in the speed of the transition process with a coefficient of about 0.2 m/s per degree, while an increase in pressure at a given temperature leads to a decrease in the transition process speed with a coefficient of 25.8 m/s per megapascal. The advancement of the vapor front velocity measurements to sub-microsecond intervals from the first signs of boiling-up did not confirm the existence of a Rayleigh expansion stage with a constant velocity.

The kinetic study of free radical polymerization of styrene in the presence of n-pentane is a challenging and relevant topic because of its commercial and scientific value. Although this reaction has been carried out for decades, its kinetics are not fully understood. Thus, this polymerization is a current research topic mainly focused on the diffusive effects and ways to make more economical and efficient processes. This work presents a study focused on analyzing the kinetic effect of n-pentane addition during the bulk free-radical polymerization of styrene to contribute to the comprehension of phenomena which take place during this reaction. To reach this goal, we extended and implemented a model previously developed by one of the authors to perform the simulation and prediction of experimental data reported in the literature at different reaction conditions and multiple n-pentane amounts. Results obtained with the model allow us to explain the polymerization evolution in terms of the diffusive effects and the explicit theoretical description of the repetitive units that a terminal segment from a long radical involved in the termination stage can move (Usegm). That lets us identify the effects produced by the presence of n-pentane in the theoretical transition region from chemical to diffusive control in the termination reaction. This region is relevant due to its relationship with the increasing polymerization rate and the onset of the auto-acceleration effect. The comparison of the theoretical evolution of the weight-average molecular weight (Mw) against experimental data indicates that to enhance their correlation is necessary to consider not only the solvation effect but also the transfer effect produced by the presence of n-pentane during the polymerization. [ABSTRACT FROM AUTHOR]

Flow boiling is a complex process but very efficient for thermal management in different sectors; enhancing flow boiling heat transfer properties is a research field of great interest. This study proposes the use of various nanomaterials, carbon-based materials, and metal oxides; in n-pentane as a hydrocarbon-based refrigerant to enhance the flow boiling heat transfer coefficient. This thermal property has been experimentally evaluated using a vertical evaporation device of glass with an internal diameter of 20 mm. The results have shown that proposed nanomaterials dispersion in n-pentane has a limited effect on the thermophysical properties and is conditioned by their dispersibility but promotes a significant increment of pentane heat transfer coefficient (h), increasing the overall heat transfer coefficient (U) of the evaporator. The enhanced heat transfer performance is attributed to the behavior of nanoparticles under working conditions and their interaction with the working surface, promoting a higher generation of nucleation sites. The observed behavior suggests a heat transfer mechanism transition from forced convection to nucleate heat transfer, supported by visual observations.

Direct production of light olefins, building blocks of chemical industry, can be attained by developing efficient catalysts for Fischer-Tropsch synthesis (FTS). The nature of FTS complicates the catalyst development process as the product distribution is affected by the components and the preparation methods of the catalyst. In this work, high-throughput (HT) methodology is employed to overcome this problem by testing many different catalyst formulations. Fast performance screening of 40 different a-Al2O3 supported Fe-Mn based catalysts promoted with Cu, K and Ni, using different impregnation agents, was performed in a HT test system at atmospheric pressure. Promising catalyst candidates identified by HT analysis were further subjected to high pressure FTS in a conventional system. Results indicate that coupled with Mn, Ni promoted CH4 production, Cu increased CO conversion, K enhanced olefin selectivity and olefin-to-paraffin ratio. In double promotion of Cu and K, Cu balanced the activity and stability loss due to K, while K enhanced olefin selectivity. n-pentane aided impregnation slightly enhanced catalytic performance. Differences observed in catalytic performance were regarded as related to the structural changes caused by promoter and impregnation type based on characterization data obtained by H2-TPR, XRD, SEM, EDS mapping and N2 adsorption. [ABSTRACT FROM AUTHOR]

Recent combustion research has focused on low temperature combustion to meet engine emission regulations and to advance the development of low temperature homogenous compression ignition engines. Autoignition studies in this temperature regime are primarily performed by Rapid Compression Machines (RCMs) which are sensitive to the heat transfer characteristics of the experimental device. RCMs are widely used to measure autoignition data such as ignition delay and species concentration. Measured ignition delays from RCMs are typically reported at an adiabatic condition; however, this assumption may produce a systematic error in ignition delay measurement as heat transfer is observed to reduce the pressure and temperature during the autoignition process, e.g., a longer ignition delay has a greater pressure and temperature drops. RCMs are custom built and have unique design characteristics that affect the heat transfer during the autoignition process. In addition, depending on the diluent composition (e.g., helium versus nitrogen or argon), different heat transfer characteristics are expected. As a result, autoignition results at similar conditions may vary from facility to facility or depending on the used diluent. The dependency of the measured data on the used facility or diluent may produce uncertainty in the data which impact the development of high-fidelity combustion mechanisms. In this work, a new method is developed and utilized to eliminate heat transfer from the ignition delay data. To evaluate the new method, the autoignition of n-pentane mixtures in the low temperature regime were investigated using an RCM. To vary the heat transfer, the compression ratio of the RCM was changed and the ignition delays were measured at similar pressure and temperature conditions. The tests were performed at an equivalence ratio of approximately one and nitrogen and argon as diluents. By applying the new method, the effect of heat transfer on the ignition delays were eliminated successfully and ignition delays at adiabatic condition were determined. A detailed kinetic model of n-pentane was used to simulate the measured adiabatic ignition delay, which agreed well with the experimental data. [ABSTRACT FROM AUTHOR]

In the present work, the boiling heat transfer coefficient (BHTC) and fluid flow characteristics of graphene oxide nanoplatelets (GONPs) nano-suspensions in an annular heat exchanger (AHEX) were experimentally investigated. The BHTC, pressure drop (PD) and the friction factor (FF) of the heat exchanger was quantified, and effects of various operating conditions including heat flux (HF), flow rate (FR), the temperature of the nano-suspension and the mass concentration (MC) of the GONPs on the HTC and the PD of the system was assessed. Results showed that by increasing the HF, the weight concentration of the GONPs, and the temperature of the working fluid, the BHTC of the system increases. Also, the presence of GONPs can augment the friction forces, viscosity, and, as a result, increase the PD and the FF of the system. For all the experiments, the BHTC of the system was more significant than water. A comparison between water-perfluorohexane and water- n-pentane nano-emulsions revealed that water-n pentane has better thermal performance and lower PD in comparison with perfluorohexane despite the presence of the GONPs within the bulk of the nano-emulsion.

n-pentane catalytic cracking was studied over a series of MFI zeolites with varying SiO2/Al2O3 ratios (30, 80, 280, 500, and 1500) using a fixed-bed reactor operated at temperature 550–650 °C. Other MFI zeolites (SiO2/Al2O3 = 280) with various crystal morphology and size (such as large crystal and nano size) were also synthesized and tested for n-pentane cracking. The effects of MFI zeolite modification with ammonia and phosphorus on its physiochemical properties and catalytic activity were investigated. Among the parent MFI zeolites, MFI (280) demonstrated high selectivity (51%) towards light olefins (C3=/C2= = 0.7) at 650 °C with undesired C1–C4 alkanes (38%). Surface modified MFI (280) zeolites of different crystal size and morphology showed improvement towards propylene selectivity by suppressing undesired reactions. Phosphorous-modified MFI zeolite with a large crystal size was found to improve light olefin selectivity (52.2%) with C3=/C2= = ∼1.3 and reduce undesired C1–C4 alkanes (8%) formation due to suppressed strong acidic sites. The characterization and evaluation results for the modified MFI (280) revealed that the incorporation of phosphorous created moderate acidic sites, which were stabilized by some non-framework aluminum species, thereby leading to suppressing the formation of undesired C1–C4 alkanes with improved light olefins selectivity.

A series of ReaxFF reactive molecular dynamic simulations are performed to investigate the combustion of n-pentane, isopentane and neopentane. The effects of temperature and the n-pentane-to-O2 ratio on the number of main radical and molecular products for the combustion of n-pentane are analyzed, the combustion characteristics of n-pentane, isopentane and neopentane are compared, and the spontaneous combustion characteristic of n-pentane is discussed in this work. The results indicated that the main reactions involved in the early stage of n-pentane, isopentane and neopentane combustion are the pyrolysis of these working fluids, and then, O2 molecules are involved in the oxidation reactions. The content of O2 in reaction systems has a very obvious effect on the combustion of n-pentane. With the increase in the O2 content, the consumption rate of n-pentane is significantly accelerated, and the rate of increase in the total fragments number is also significantly increased. Neopentane burns most intensely, followed by isopentane, and finally n-pentane. A faster heating rate will be accompanied by more intense spontaneous combustion of n-pentane and more product formation, which will cause greater harm to the surrounding area. Thus, in order to reduce the possibility of damage caused by leakage combustion of flammable working fluid, the heat source temperature and open flame around the organic Rankine cycle system should be strictly controlled, and some flame retardants are recommended to be added to the working fluid to reduce the flammability while ensuring the economy of the organic Rankine cycle. This study is conducive to the safety of n-pentane, isopentane and neopentane used in industrial fields. [ABSTRACT FROM AUTHOR]

The metal modified ZSM-5 catalysts has been widely used in the aromatization of light alkanes. To investigate the effect of Si/Al ratio of ZSM-5 zeolites, a series of Zn/ZSM-5 catalysts with different Si/Al ratios have been prepared by wet impregnation and tested for n-pentane aromatization. The results indicated that, the introduced Zn species consumed the strong Brønsted acid sites and inhibited the undesired cracking reactions effectively. With the increase of Si/Al ratio of ZSM-5 zeolites, the n-pentane conversion decreased obviously due to the reduced acid content and strength, while the selectivity to BTX remained almost unchanged. Attributed to the weakened cracking and hydrogen-transfer reactions with increasing Si/Al ratio, the selectivity to light alkanes decreased, while that to olefins increased remarkably. Further, the possible reaction pathways have been proposed to better elucidate the changing product distribution with the Si/Al ratios. [ABSTRACT FROM AUTHOR]

Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• SVUV-PIMS was used for the concentration determination and species identification of pyrolysis products. • An updated kinetic model of n-pentane pyrolysis was developed and validated. • The rate of production and sensitivity analyses were conducted to depict reactant and product species profiles. • Alkenes were produced with higher concentration compared to other product species. In a flow reactor, the pyrolysis process of n-pentane in the 450–750 °C temperature range was investigated at 760 Torr. The pyrolysis products, particularly free radicals and isomers, were identified using synchrotron radiation vacuum ultraviolet photoionization mass spectrometry, and their mole fractions were determined. In this study, the existing n-pentane pyrolysis kinetic model was updated according to the C 5 -mechanism, and the new pyrolysis data were validated. The rate of production and sensitivity analyses were conducted to determine the significant reactions controlling the pyrolysis of fuel and their effects on the reactant concentration and product species profiles. The unimolecular decomposition reaction and free radical attack reaction via H attack dominate n-pentane pyrolysis at atmospheric pressure. Alkenes including 1-pentene, 1-butene, propene and ethylene are produced with higher concentrations than other product species in n-pentane pyrolysis. [ABSTRACT FROM AUTHOR]

In the present work, the boiling heat transfer coefficient (BHTC) and fluid flow characteristics of graphene oxide nanoplatelets (GONPs) nano-suspensions in an annular heat exchanger (AHEX) were experimentally investigated. The BHTC, pressure drop (PD) and the friction factor (FF) of the heat exchanger was quantified, and effects of various operating conditions including heat flux (HF), flow rate (FR), the temperature of the nano-suspension and the mass concentration (MC) of the GONPs on the HTC and the PD of the system was assessed. Results showed that by increasing the HF, the weight concentration of the GONPs, and the temperature of the working fluid, the BHTC of the system increases. Also, the presence of GONPs can augment the friction forces, viscosity, and, as a result, increase the PD and the FF of the system. For all the experiments, the BHTC of the system was more significant than water. A comparison between water-perfluorohexane and water- n-pentane nano-emulsions revealed that water-n pentane has better thermal performance and lower PD in comparison with perfluorohexane despite the presence of the GONPs within the bulk of the nano-emulsion. [ABSTRACT FROM AUTHOR]

To understand the synergistic effect of hydrogen-enriched combustion of hydrocarbons in the high temperatures, ignition delay times of lean (φ = 0.5) n -pentane/hydrogen mixtures with various hydrogen volumetric contents (X H2 = 0–95%) were measured in a shock tube at pressures of 2, 10 and 20 atm. As expected, the ignition delay time of n -pentane is decreased when doping with hydrogen. Interestingly, the effect of hydrogen addition on auto-ignition is nonlinear. Note that even the hydrogen proportion is as large as 95%, the ignition delay time of the binary mixture exhibits the n -pentane-like activation energy and pressure dependence characteristics. Reasons for the above-mentioned behaviors were analyzed. • New ignition delay time data of hydrogen/ n -pentane/O 2 /Ar mixtures were provided. • Hydrogen doping can nonlinearly promote the auto-ignition of n -pentane. • The binary mixture exhibits the n -pentane like activation energy. • Hydrogen addition can promote the H-abstractions of the n -pentane. [ABSTRACT FROM AUTHOR]

Copyright of Zeitschrift für Physikalische Chemie is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Combustion chemistry models have been developed with inherent uncertainties in them. Whether a model that is developed using fundamental combustion experiments is capable to reproduce practical combustion processes within typical levels of measurement uncertainty is an open question. This paper quantifies the uncertainty of engine autoignition simulation using the uncertainties in the selected chemical kinetic model and then minimizes the model prediction uncertainty using various experiments. The method adopts a deterministic framework of uncertainty quantification, termed bound-to-bound data collaboration , and applies it to simulate the autoignition of n- pentane in a standard octane rating experiment. The results show that simulation of the end-gas autoignition using a comprehensively tested n- pentane model coupled with a two-zone engine combustion model yields an uncertainty substantially higher than that of engine experiment (as indicated by the cycle-to-cycle variation of the autoignition timing measurement). In-cylinder thermochemical conditions are found to be less important than the kinetic parameters in determining the model uncertainty. The large model uncertainty can be reduced by constraining the simulation with consistent experimental data and their measurement uncertainties, including those from fundamental experiments that measure ignition delays, species concentrations, flame speeds, and more significantly from autoignition experiments in well-calibrated engines. [ABSTRACT FROM AUTHOR]

Energy optimization is performed on hybrid solar-geothermal power plant working according to Organic Rankine Cycle and installed in southern Tunisia. The performances of four different configurations of the power plant are studied. Mass and energy balances are established for the different compounds. The effects of the main operating parameters such as the geothermal water temperature, ambient temperature and direct normal irradiation on the power plant performances are analyzed. A code is established using Engineering Equation Solver software (EES) to perform the required calculations. Obtained results show that the hybrid solar-geothermal power plant with a heat recovery system is the most suitable configuration design giving a better overall energy efficiency of 15.77 and13.11% and a maximum net power of 1089 and 1882 kW in winter and summer, respectively. However, in the summer season, using a heat recovery system can valuable only when the water temperature is higher than 66°C. For air-cooled condenser, the suitable condensing pressure is 1 bar in winter and 1.9 bars in summer. [ABSTRACT FROM AUTHOR]

• 3-D simulations of falling film flow around curved egg-shaped tubes are conducted. • The influence of Re and inter-tube spacing on falling film flow are examined. • The average film thickness firstly increases and then decreases as the increase of Re. • Film thickness of basin zone is thinner than the prediction results of circular tube. Shell-side falling film flow is extremely important for the heat transfer performance of spiral wound heat exchangers used in liquefied process of natural gas. In this paper, 3-D simulations using hydrocarbon (n-pentane) as the testing fluid are conducted to study the fluid flow characteristic of heat exchanger with curved egg-shaped tube. The effects of different Re numbers (Re) and longitudinal inter-tube spacing (S) on the inter-tube flow modes and the distribution of film thickness (δ) with Re varying from 327 to 2944 are investigated. The axial and circumferential distribution of δ is analyzed qualitatively and quantitatively. The results show that when Re is relatively small (327 and 736), the effect of S on average value of δ (δ a) is negligible. When Re is relatively large (1472 and 2944), the increase of S would thicken δ on tube lower perimeter. When Re increased from 327 to 2944, δ a firstly increases and then decreases as the increase of Re and the ratio (L b) of the axial length of basin zone to the axial measurement range increases from 52% to 76%. In addition, δ of basin zone is almost always much lower (59.23% thinner when Re = 2944) than the classic prediction results of equal-perimeter circular tube. [ABSTRACT FROM AUTHOR]

While there is consensus on the fact that OOQOOH radicals, produced by two oxygen additions from alkyl radicals, are the heart of the low-temperature oxidation of alkanes, the determination of the isomeric distribution and the quantification of their derived products (ketohydroperoxides and diones) are still a challenge. For the first time, heavy oxygenated products produced during alkane oxidation have been investigated using electron/ion coincidence mass spectrometry. The investigated prototype reaction is n -pentane oxidation carried out in a jet-stirred reactor (temperatures from 585 to 665 K, pressure of 1.1 bar, lean mixture). Identification attempts were made for m/z 100 and 118 species using coincident mass-tagged Slow PhotoElectron Spectra obtained by electron-ion coincidence mass spectrometry combined with first principle computations, consisting in the determination of their adiabatic ionization energies and the Franck-Condon envelope of the photoionization spectra. 4-hydroperoxypentan-2-one has been confirmed as the dominant obtained ketohydroperoxide, as predicted by up-to-date kinetic models. However, difficulties due to fragmentation has made impossible the identification of the ketohydroperoxides present in lower amounts. In parallel, C 5 H 8 O 2 isomers were identified, showing the possible formation, in addition to diones, of species with a ketone and an enol function. In addition, we provide new information on the first steps of the fragmentation pathways of C 5 ketohydroperoxides. From the shape of their corresponding peaks on mass spectra and the energy and temperature dependence of their signal, ions at m/z 43, 57 and 85 have been identified as fragments from ketohydroperoxides. Taking into account these fragmentations lowers, by more than a factor of 10, the previously observed deviation between experiments and modeling for ketohydroperoxide mole fractions. The formation of the C 1 -C 2 carboxylic acids, predicted from Korcek decomposition, was also observed, but with a favored formation of acetic acid versus formic acid that what was predicted for propane. [ABSTRACT FROM AUTHOR]

Air-light hydrocarbon mixing gas is a new type of fuel with great potential, and its key component is n-pentane. In this study, a reduced n-pentane mechanism with NO X is developed for combustion simulation at atmospheric pressure, including 81 species and 348 elementary reactions. First, the dominant species and reactions for n-pentane combustion are recognized by the reaction pathway analysis based on the detailed mechanism. Then, a novel multistep reduction strategy with intersection thought is proposed to reduce the detailed mechanism of n-pentane. Ignition delay time and laminar flame speed are separately selected as the target parameters for validation. The two reduced mechanisms are developed by using the directed relation graphs (DRG) method, the directed relation graphs with error propagation (DRGEP) method, and the full species sensitivity analysis (FSSA) method. Species in the intersection mechanism of the above two mechanisms obtained with multistep reduction are treated as important species. Sensitivity analysis (SA) is further performed to remove the uncertain species, combined with the result of reaction pathway analysis, a reduced n-pentane mechanism including 77 species and 336 reactions is obtained. On this basis, a reduced NO X mechanism (4 species and 12 reactions) is incorporated. Then, the key kinetic parameters of the mechanism are optimized and adjusted according to the results of brute force sensitivity analysis. Finally, the proposed mechanism is validated by using the related data of ignition delay times, laminar flame speeds, premixed flame species profiles, and jet-stirred reactor (JSR) species profiles. The results indicate that the proposed mechanism shows good model performance. This study can provide significant assistance for subsequent research on air-light hydrocarbon mixing gas. • A novel multistep reduction strategy with intersection thought is proposed. • The brute force sensitivity analysis is used to optimize the reduced mechanism. • The proposed compact mechanism covers important details of low- and high-temperature reactions. • The proposed mechanism predicts combustion characteristics and captures species evolution trends with sufficient accuracy. [ABSTRACT FROM AUTHOR]

• The kinetics and dynamics of the boiling-up of superheated n -pentane was studied. • The spontaneous boiling-up occurred at atmospheric pressure and above. • We calculate the linear velocity of an evaporation front of superheated liquid. • The velocity increases with the depth of entry into the metastable region. • The velocity depends on the configuration of the liquid-vapor interface. An experimental study of the kinetics and dynamics of spontaneous boiling-up of superheated n -pentane in a thermostated glass tube was carried out using high-speed video recording. The boiling-up occurred both at steady atmospheric pressure (in the temperature range from 100.3 to 125.3 °C) and during pressure reduction (from 105.3 to 135.3 °C). The top of the tube is sealed. The linear propagation velocity of an evaporation front of a superheated liquid has been calculated from the video frames. It has been shown that this value lies in the range from 0.30 to 2.23 m/s, increases with the depth of entry into the metastable region, and depends on the configuration of the liquid-vapor interface. [ABSTRACT FROM AUTHOR]

Mixtures appear to hold more promise in organic Rankine cycle (ORC) system than pure working fluids due to their better performance. The key limiting factor for the screening of mixture in the medium- and high temperature ORC system is its thermal stability. ReaxFF reactive molecular dynamic simulations and density functional theory calculations are performed in this study to investigate the thermal decomposition mechanism of n-pentane/n-butane mixture and predict its thermal stability. The results show that the presence of n-butane improves the thermal stability of n-pentane. According to the initial decomposition time, decomposition rates and apparent activation energies of mixture and pure working fluids, n-pentane/n-butane mixture has a better thermal stability than n-pentane and worse than n-butane. Based on the decomposition temperature ranges of n-pentane and n-butane, it can be determined that the n-pentane/n-butane mixture is stable at 280 °C. Therefore, the safe use temperature of the mixture can be roughly predicted based on the thermal stability data of the known working fluids and comparing the thermal decomposition of the mixture with these known working fluids. This paper provides a simple, economical and fast way for the safe use temperature prediction of mixture. • The decomposition mechanism of hydrocarbon mixture is first investigated. • Initial decomposition pathways of n-pentane and n-butane are analyzed. • Thermal stability of n-pentane/n-butane mixture is better than pure n-hexane. • Safe use temperature can be roughly predicted based on the decomposition characteristics. [ABSTRACT FROM AUTHOR]

A comprehensive, chemically detailed mechanism for the combustion of 2-methyl-2-butene and n -pentane is presented to provide insights into the different sooting tendencies of these two structurally different C 5 hydrocarbons. A hierarchically assembled mechanism has been developed to specifically target speciation data from low-pressure premixed flames of 2-methyl-2-butene [Ruwe et al., Combust. Flame, 175, 34-46, 2017] and newly measured mole fraction data for a fuel-rich (ɸ =1.8) n -pentane flame, in which species profiles up to phenol were quantified. The partially isomer-resolved chemical composition of this flame was determined using flame-sampling molecular-beam mass spectrometry with single-photon ionization by tunable, synchrotron-generated vacuum-ultraviolet radiation. The presented model, which includes a newly determined, consistent set of the thermochemistry data for the C 5 species, presents overall satisfactory capabilities to predict the mole fraction profiles of common combustion intermediates. The analysis of the model predictions revealed the fuel-structure dependencies (i.e. saturated vs. unsaturated and linear vs. branched) of the formation of small aromatic species that are considered as soot precursors. The propensity of the 2-methyl-2-butene flame to form larger concentrations of aromatic species was traced back to the readily available formation routes of several small precursor molecules and the efficient formation of "first aromatic rings" beyond benzene. [ABSTRACT FROM AUTHOR]

The purpose of this research work is to prepare and assess the catalytic performance of platinum (Pt) dealuminated mordenite for the of n-hexane, n-pentane and light naphtha isomerization. The Pt dealuminated mordenite was prepared by dealumination of commercial mordenite catalyst by refluxing using hydrochloric acid at 100 °C in various time durations (0.50, 1.0, and 3.0 h). The commercial as well as dealuminated mordenite catalysts were examined by X-ray diffraction analysis, X-ray fluorescence, N 2 adsorption-desorption, Fourier-transform infrared spectroscopy, temperature-programmed desorption (NH 3 -TPD), scanning electron microscopy, and transmission electron microscopy with high resolutions XRD and BET surface area analysis. These afore mentioned studies confirm that the dealumination process exhibit an increasing the external surface area and improved the total acidity with retaining the structure of mordenite. The catalytic performance was investigated for the of n-hexane, n-pentane and light naphtha isomerization by varying factors such as, temperature, reaction pressure, hydrogen flow, hourly mass feed flow rate and catalyst mass. Among the catalysts, the dealuminated catalyst with SiO 2 /Al 2 O 3 ratio of 40% exhibited highest conversion Pt–Cl–Al 2 O 3 operate set the lowest temperature on and selectivity. The density functional theory (DFT) calculation implies that the activation free energy for isomerization of n-hexane varies with the position of interacting C–H bond with mordenite (Pt/Mordenite) cluster. Besides, the activation energy for the n-pentane isomerization is lesser than the n-hexane isomerization. Image 1 • The commercial mordenite zeolite was dealuminated (Si/Al = 28, 32, 40, and 50) successfully by acid leaching method. • N 2 sorption study, SEM and TEM confirms the enhanced textural properties and suitable morphology of mordenite (40) support. • Higher conversion and selectivity was seen over Pt/mordenite (40) catalyst for the isomerization of n-alkanes at 200 °C. • The DFT results showed that free energy activation of mordenite cluster varies with the position of interacting C–H bond. [ABSTRACT FROM AUTHOR]

An experimental study was undertaken to assess the heat-transfer coefficient (HTC) of graphene nanoplatelets-pentane nanofluid inside a gravity-assisted heat pipe (HP). Influence of various parameters comprising heat flux, mass fraction of the nanoparticles, installation angle and filling ratio (FR) of the working fluid on the HTC of the HP was investigated. Results showed that the HTC of the HP was strongly improved due to the presence of the graphene nanoplatelets. Also, by enhancing the heat flux, the HTC of the HP was improved. Two trade-off behaviors were identified. The first trade-off belonged to the available space in the evaporator and the heat-transfer coefficient of the system. Another trade-off was identified between the installation angle and the residence time of the working fluid inside the condenser unit. The installation angle and the FR of the HP were identified in which the HTC of the HP was the highest. The value of installation angle and filling ratio were 65° and 0.55, respectively. Likewise, the highest HTC was obtained at the largest mass fraction of the graphene nanoplatelets which was at wt. % = 0.3. The improvement in the HTC of the HP was ascribed to the Brownian motion and thermophoresis effects of the graphene nanoplatelets. [ABSTRACT FROM AUTHOR]

BACKGROUND Over the past few decades, tri‐n‐butyl phosphate (TBP) has been a widely used and irreplaceable extractant that can extract a variety of heavy metal ions and inorganic acids. The conventional process of tri‐n‐butyl phosphate synthesis has the problem of low yield. The in situ vapor stripping method was developed to intensify the tri‐n‐butyl phosphate synthesis reaction. RESULTS: In this work, the coupling process of in situ vapor stripping and reaction was proposed for the first time in the process of synthesis of TBP. It was found that the reaction of high concentration hydrogen chloride and 1‐butanol would produce water, which resulted in increasing the possibility of side reactions, especially when the temperature was higher than 55 °C. In the lower temperature range, n‐pentane was selected as the stripping medium, which effectively removed hydrogen chloride from the reaction system by in situ vapor stripping. The FT‐IR analysis confirmed that TBP can be synthesized successfully by the vapor stripping process. In addition, the effects of n‐pentane volume, temperature and stripping time on the yield of TBP and the amount of hydrogen chloride stripped were investigated. By applying the optimum reaction conditions, the yield of TBP was increased to 94%, larger than that of the current industrial process whose yield is only 80%. CONCLUSION: The in situ vapor stripping process is demonstrated to be an effective method for intensification of the esterification process in TBP synthesis. It can be used for other reactions which generate volatile gases as the byproduct. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The physicochemical properties of alumina–platinum catalysts with supports prepared by mixing aluminum and zirconium hydroxides have been studied. The chemisorption and nonoxidative conversion of methane in the presence of the above systems have been investigated. The effect of the zirconium content on the activity and selectivity of the conversion of chemisorbed CH4 and n-C5H12 into aromatic hydrocarbons has been established. [ABSTRACT FROM AUTHOR]

Fuel development for solvent deasphalting (SDA), by means of which it is possible to obtain high yields of deasphalted oil (DAO) with acceptable quality for subsequent refining in catalytic cracking processes and hydrocracking in particular, is nowadays becoming increasingly important. In this paper, an experimental study of the SDA of tar (vacuum residue) with n-pentane at various extraction temperatures and pressures was undertaken, and this made it possible to determine the effect of the phase state of the solvent on the yield, composition, and properties of the separation products,. It was shown that transfer of pentane from the liquid phase state to the region of a subcritical and then supercritical fluid (SCF) increases the solubility of the tar components and the yield of the DAO for fixed values of the solvent density. Despite some decrease in the quality of the DAO in the case of supercritical extraction at temperatures close to the critical temperature of the solvent (220°C), the phase state of the pentane has little effect on the metal content of the products, the carbon residue content of the DAO, and the softening point of the asphalt for the given yields. [ABSTRACT FROM AUTHOR]

Abstract The mutual oxidation of n -pentane and NO 2 at 500–1000 K has been studied at equivalence ratios of 0.5 and 1.33 by using an atmospheric-pressure jet stirred reactor (JSR). N -pentane, O 2 , NO, NO 2 , CO, CO 2 , CH 2 O, C 2 H 4 , and CH 3 CHO are simultaneously quantified, in-situ by using an electron-impact molecular beam mass spectrometer (EI-MBMS), a micro-gas chromatograph (μ-GC), and a mid-IR dual-modulation faraday rotation spectrometer (DM-FRS). Both fuel lean and rich experiments show that, in 550–650 K, NO 2 addition inhibits low temperature oxidation. With an increase of temperature to the negative temperature coefficient (NTC) region (650–750 K), NO 2 addition weakens the NTC behavior. In 750–1000 K, high temperature oxidation is accelerated with NO 2 addition and shifted to lower temperature. Two kinetic models, a newly developed RMG n -pentane/NO x model and Zhao's n -pentane/NO x model (Zhao et al., 2018, Submitted) were validated against experimental data. Both models were able to capture the temperature-dependent NO 2 sensitization characteristics successfully. The results show that although NO 2 addition in n -pentane has similar effects to NO at many conditions due to fast NO and NO 2 interconversion at higher temperature, it affects low temperature oxidation somewhat differently. When NO 2 /NO interconversion is slow, NO 2 is relatively inert while NO can strongly promote or inhibit oxidation. Highlights • NO 2 shows three temperature dependent effects on n -pentane oxidation. • When NO 2 /NO interconversion is slow, NO 2 is relatively inert on the oxidation. • NO 2 and NO have similar sensitization effects at fast NO 2 /NO interconversion. • Reactions RO 2 = QOOH, RO 2 +NO = RO + NO 2 , and RO 2 +M = C 5 H 10 +HO 2 +M explain the NO 2 effects. [ABSTRACT FROM AUTHOR]

With increasingly stringent environmental regulations, desulfurization for gasoline oil production has become an important issue. Nowadays, desulfurization technologies have become an integral part of environmental catalysis studies. It is also important for processing of fuel for fuel-cells, which has a strict requirement for sulfur content for internal combustion engines. In this study, we focused on the preparation and characterization of magnesium hydroxide/aluminum supported NiO, ZnO, ZrO2, NiO-ZnO, NiO-ZrO2, adsorbents for the adsorptive desulfurization of liquid fuels. These hydrotalcite adsorbents were prepared by co-precipitation method and used for adsorption of thiophene (in n-pentane, as model fuel) and dibenzothiophene at ambient temperature and pressure. The physicochemical behaviors of the fresh adsorbents such as structure, composition, and bonding modes were determined using X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), energy dispersive X-Ray analysis (EDAX), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The sulfur concentration in the mixture (thiophene and n-pentane) was measured by UV-Vis spectrophotometry. The percentages of thiophene removal and the adsorption capacity (mg of sulfur per g of adsorbent) of the five adsorbents were compared. The adsorption performance confirmed that NiO-ZrO2 and NiO-ZnO adsorbents are more efficient in removing thiophene/dibenzothiophene than that of three other adsorbents. The qualitative studies using XPS confirmed the efficient adsorption nature of modified hydrotalcite adsorbents on dibenzothiophene.

One of the most common and reliable methods of water treatment is the method of thermal distillation. Despite the reliability of the method, its application is constrained by high energy intensity. The most effective way to reduce the cost of production of distillate is the use of thermal transformers, providing regenerate and heat recovery phase transformations of the distillate. The use of working fluid with the most favorable thermodynamic properties is of paramount importance for the creation of high efficiency thermotransformers. The work is considered working fluid for high-temperature heat pumps and the results of the calculation-experimental study of high-temperature vapor compression heat-pumping distiller on natural working substance n-pentan.

Abstract The low temperature oxidation of n-pentane with nitric oxide (NO) addition has been investigated at 500–800 K in an atmospheric jet stirred reactor (JSR). The molar fraction of NO in the mixture is varied between 0 to 1070 ppm to study its chemical sensitization effect on low temperature oxidation of both fuel lean and rich n-pentane/oxygen mixtures. N-pentane, O 2 , CO, CO 2 , CH 2 O, C 2 H 4 , CH 3 CHO, NO, and NO 2 are quantified simultaneously, in-situ by using an electron impact molecular beam mass spectrometer (MBMS), a micro-gas chromatograph (µ-GC), and a sensitive mid-IR dual-modulation faraday rotation spectrometer (DM-FRS). The experimental results reveal that NO addition delays the onset temperature of low temperature oxidation of n-pentane between 550–650 K, but reduces the negative temperature coefficient (NTC) behavior in the NTC region (650–750 K) and dramatically shifts the onset of high temperature fuel oxidation to an intermediate temperature (750–800 K). A recently developed n-pentane/NO x model by using Reaction Mechanism Generation (RMG) and a new n-pentane/NO x model in the present work were used to predict the experimental results. The results show that the three distinct temperature-dependent characteristics of NO sensitized n-pentane oxidation are captured appropriately by these two models at both fuel rich and lean conditions, while the onset temperature of low temperature oxidation is not accurately predicted by these two models. It shows that the RMG model has a better prediction of the onset delay of n-pentane oxidation than Zhao's model, while Zhao's model performs better at NTC and intermediate temperature regions. Besides RO 2 + NO, additional fuel/NO x reaction pathway, like R + NO 2 , RO + NO, and RO + NO 2 , and the interconversion reactions among NO, NO 2 , and HONO may need to be further studied. [ABSTRACT FROM AUTHOR]

PVTx-properties of the HO - n-CH and HO - n-CH mixtures are measured in the temperature range 303-680 K at pressures up to 60 MPa. The measurements were carried out along 265 liquid and vapor isochors in a density range of 63-713 kg/m. The measurements were performed for 15 concentrations between 0.110 and 0.987 mole fractions of HO for the CH mixtures and for 11 concentrations between 0.166 and 0.977 mole fractions of HO for the CH mixtures. The temperatures and pressures on the three-phase and two-phase boundary curves were obtained for the mixtures from isochors using the kink or inflection method. The data for the critical parameters of the upper and lower branches of the critical curves were obtained from the boundary curves by the method of rectilinear diameter. The measured three-phase data were used to estimate the value of the upper final critical point. [ABSTRACT FROM AUTHOR]

Hydrous and anhydrous isothermal experiments on n-pentane and n-octadecane were conducted at 300–375℃ for durations up to 1094 h to evaluate the cracking and hydrolysis of hydrocarbons, using fused silica capillary capsules as micro-reactors. The chemical compositions of the gaseous products during cracking of n-octadecane at 350 and 375℃ were methane, ethane, propane, and n-butane. The aqueous product in the hydrolysis of n-pentane and n-octadecane at 300–375℃ was alcohol. Alkenes and hydrogen were not detected throughout all the isothermal experiments. Results showed that the gaseous yields were characterized by higher contents of wet gas than those in natural gas accumulations. Mechanisms regulating the enrichment of methane in reservoirs should be further studied. The hydrolysis and oxidation of hydrocarbon were relatively limited in the absence of iron-bearing mineral buffers, suggesting that hydrocarbons might be more stable in iron-poor reservoirs (e.g. carbonate and quartz arenite) than in iron-bearing-mineral-rich ones (e.g. mudstone and arkose) under deep burial conditions. The absence of hydrogen was ascribed to its high diffusion rate in fused silica than in gold tube; any hydrogen produced in the reaction tends to diffuse out of the fused silica capsule with no or limited hydrogen accumulation, similar to those in geological environment. The diffusion of hydrogen should be considered during calculating the volume and pressure changes in the thermal cracking of oil to gas in reservoirs, because the loss of hydrogen would result in a decrease in the conversion rate of oil to gas. [ABSTRACT FROM AUTHOR]

The state and size of the metal on the surface of aluminum oxide and the acidic properties of the support depending on the concentration of supported platinum were studied in this work. The effect of the Pt content of the alumina-platinum catalyst on the activation (chemisorption) of methane was investigated, and the composition of hydrocarbon fragments formed in this case was calculated. The sample most active in a reaction of the joint conversion of methane with n-pentane, which was performed for the production of aromatic hydrocarbons under nonoxidizing conditions, was established. The effect of the temperature of n-pentane supply to the reaction atmosphere was studied for the 0.6%Pt/Al2O3 catalyst. The degree of enrichment of the resulting aromatic hydrocarbons and the quantity of incorporated methane activated on the catalyst surface were determined with the use of isotope mass spectrometry. [ABSTRACT FROM AUTHOR]

Measurements of the thermal conductivity of n-pentane performed for the first time, in a coaxial cylinder cell operating in steady state conditions are reported. The measurements of the thermal conductivity of n-pentane were carried out along nine isotherms in the liquid state and fourteen isotherms in the gaseous state. The present data cover the temperature range from 300 K to 620 K and the pressure range from 0.1 to 50 MPa. An analysis of the various sources of error leads to an estimated uncertainty of approximately ±1.5%. A comparison is provided with the previous experimental works. [ABSTRACT FROM AUTHOR]

The utilization of a microcontroller board, optimized for the simultaneous data logging of chromatographic information, the oven temperature, and remote transfer to a personal computer, is investigated, with the goal to extend the capabilities of a gas chromatograph (Shimadzu GC-14A) which does not include a built-in data logging module. An initial comparison of the chromatographic peaks obtained from solute injections, collected both by a dedicated analog-to-digital expansion card and the microcontroller board, demonstrated the latter’s ability to perform accurate analog signal digitization. Afterward, the evaporation of three organic liquids (methanol, acetone, andn-pentane) was studied by reversed-flow inverse gas chromatography. From the temperature variation of the experimentally determined rates, the respective thermodynamic functions of enthalpy and entropy changes of acetone and methanol evaporation were determined. The small deviations from the theoretical values indicate the reliability of the proposed methodology. More importantly, it was made apparent that by utilizing automatic data logging instead of the carrier gas flow reversal procedure, the monitoring of rapid physicochemical phenomena was performed with better accuracy, while the duration of the experiments was decreased with the reduced consumption of gas chromatographic consumables. [ABSTRACT FROM PUBLISHER]

The solvent deasphalting (SDA) process is a heavy oil upgrading process in which deasphalted oil (DAO) is extracted from heavy oil feedstock by precipitating asphaltene using an excess amount of alkane solvent (C3-C6). After the extraction, solvent recovery should be carried out for separating the solvent from the DAO in order to recycle the expensive solvent. In the conventional solvent recovery method, the mixture of solvent and DAO is heated to evaporate the solvent, which requires massive heat energy, resulting in reduced process efficiency. In this study, CO 2 is applied for the first time to selectively separate solvent from DAO at a relatively low temperature. The experimental results in a batch separator indicate that the temperature required for high solvent recovery of over 80% decreases from 200 °C to 40 °C when using CO 2 compared to the conventional method. The theoretical approach using Hansen distance calculation based on the Hansen solubility parameter (HSP) was used to verify the mechanism of solvent separation using CO 2 . The results suggest that the increase in the interaction between CO 2 and solvent causes the separation of solvent from DAO, leading to an increase in solvent recovery. Also, numerical simulation results show the possibility of continuous operation for solvent recovery using CO 2 . [ABSTRACT FROM AUTHOR]

Attractiveness in advanced low-temperature combustion engines drives a constantly updated understanding of low-temperature oxidation chemistry. In this work, the low-temperature oxidation chemistry of n -pentane in two jet-stirred reactors at atmospheric pressure and in the temperature range of 500–825 K was investigated using combined analysis methods of synchrotron vacuum ultraviolet photoionization mass spectrometry, gas chromatography, and Fourier transform infrared spectroscopy. Furthermore, the gaseous mixture from JSR was collected in acetonitrile for subsequent product characterization using flow injection analysis, high-pressure and ultra-high-pressure liquid chromatography coupled to a Thermo Scientific™ Orbitrap® Q-Exactive high-resolution mass spectrometry. Numerous intermediate species were identified by these analytical methods, which contributed to unraveling the low-temperature oxidation reaction network of n -pentane. A detailed n -pentane model was tentatively developed to reduce deviations between experimental measurements and model predictions by updating the rate constants of C 5 keto-hydroperoxide decomposition, C 5 hydroperoxy cyclic ether decomposition, and Korcek reactions of C 5 keto-hydroperoxide, and by introducing pressure-dependent rate constants for the reaction classes of Q ˙ OOH + O 2 , Q ˙ OOH decompositions, concerted HȮ 2 -elimination of RȮ 2 , C 5 keto-hydroperoxide decomposition, C 5 hydroperoxy cyclic ether decomposition, and Korcek reactions of C 5 keto-hydroperoxide, and by adding more detailed sub-mechanisms for C 5 cyclic ethers and C 5 keto-hydroperoxides. This updated model was validated against a set of available experimental data, including jet-stirred reactor species data and ignition delay times. These exploratory updates of the kinetic model reveal the considerable influence of the rate constants of hydroperoxide decomposition and the pressure-dependent rate constants of key reaction classes on the kinetic model predictions, highlighting the future demands for high-precision quantum chemistry calculations of the pressure-dependent rate constants of the aforementioned reaction classes to reduce mechanism uncertainties and to develop accurate and robust chemical kinetic models. [ABSTRACT FROM AUTHOR]

An experimental study was undertaken to assess the heat-transfer coefficient (HTC) of graphene nanoplatelets-pentane nanofluid inside a gravity-assisted heat pipe (HP). Influence of various parameters comprising heat flux, mass fraction of the nanoparticles, installation angle and filling ratio (FR) of the working fluid on the HTC of the HP was investigated. Results showed that the HTC of the HP was strongly improved due to the presence of the graphene nanoplatelets. Also, by enhancing the heat flux, the HTC of the HP was improved. Two trade-off behaviors were identified. The first trade-off belonged to the available space in the evaporator and the heat-transfer coefficient of the system. Another trade-off was identified between the installation angle and the residence time of the working fluid inside the condenser unit. The installation angle and the FR of the HP were identified in which the HTC of the HP was the highest. The value of installation angle and filling ratio were 65° and 0.55, respectively. Likewise, the highest HTC was obtained at the largest mass fraction of the graphene nanoplatelets which was at wt. % = 0.3. The improvement in the HTC of the HP was ascribed to the Brownian motion and thermophoresis effects of the graphene nanoplatelets.