Liquid N-pentane Research Articles

Measurements of the Thermal Conductivity of n-Pentane, Isopentane, 1-Pentene, and 1-Pentanol in the Temperature Range from 253 to 373 K at Pressures up to 30 MPa

In this work, thermal conductivities of a homologous series of liquids n-pentane, isopentane, 1-pentene, and 1-pentanol were measured from 253 to 373 K at pressures up to 30 MPa with a transient ho...

Speed-of-Sound Measurements in Liquid n-Pentane and Isopentane

Comprehensive and accurate measurements of the speed of sound in liquid n-pentane and isopentane were carried with a double-path-length pulse-echo instrument. The measurements cover the temperature...

An experimental study on the micro- and nanocellular foaming of polystyrene/poly(methyl methacrylate) blend composites

Abstract Polystyrene/poly(methyl methacrylate) (PS/PMMA) blends in 80:20, 50:50, and 20:80 ratios with and without calcium carbonate nanoparticles were prepared. n-Pentane was then used to foam the samples in an autoclave. After the diffusion of n-pentane gas into the polymer matrix, the samples and the gas were simultaneously cooled to obtain the liquid n-pentane phase. Phase change to liquid provided the required pressure drop for cell nucleation and consequent cell growth. The solubility of n-pentane in the samples was measured. Liquid n-pentane trapped inside created micro- and nanopores, forming a foam with closed cells. Experiments were carried out in different compositions of the materials, with and without nanoparticles, and the cell morphologies were characterized. The results of this work show that nanocellular structures can be achieved when calcium carbonate nanoparticles are added to PS/PMMA blends.

Prediction of viscosity-density dependence of liquid methane+n-butane+n-pentane mixtures using the molecular dynamics method and empirical correlations

We present a study of viscosities of n-pentane and binary and ternary methane–n-butane–n-pentane mixtures in liquid state at the temperature 360 K by the non-equilibrium molecular dynamics simulations with a modified fully flexible version of the all-atom TraPPE-EH force field. The Batchinski correlation η=C/(v−b) is used to describe the viscosities of pure n-pentane. The calculated viscosity-density dependence for liquid n-pentane is in agreement with the experimental data. We show that the viscosity-volume dependencies of liquid binary and ternary mixtures can be fitted by the Batchinski's equation as well, and the coefficients for the mixtures are obtained by linear mixing of the coefficients for pure components. The model can be used for the interpretation and interpolation of the experimental data on viscosities of hydrocarbon liquids. The Batchinski-like behavior of viscosity of liquid mixtures in some density range can be used as a test for more complex correlations, which we show by comparing the hard sphere correlation and the expanded fluid correlation for hydrocarbons.

Thermal conductivity of gaseous and liquid n-pentane

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.

Optimization of a microcontroller for the simultaneous logging of temperature and reversed-flow inverse gas chromatography measurements

ABSTRACTThe 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, and n-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.

Measuring the average volumetric heat transfer coefficient of a liquid–liquid–vapour direct contact heat exchanger

The average volumetric heat transfer coefficient in a spray column liquid–liquid–vapour direct contact evaporator has been experimentally investigated. The experiments were carried out utilising a cylindrical Perspex tube of diameter 10cm and height and 150cm. Saturated liquid n-pentane and warm water at 45°C were used as the dispersed and continuous phases, respectively. Three different dispersed flow rates (10, 15 and 20L/h) and four different continuous phase flow rates (10, 20, 30 and 40L/h) were used in the study. The effect of different parameters, such as the initial drop size, continuous and dispersed phase flow rates and sparger configuration, on the average volumetric heat transfer coefficient in the evaporator was studied. The results showed that the average volumetric heat transfer coefficient was reduced as the initial drop size increased. Also, both the continuous phase and the dispersed phase flow rates have a significant positive impact on the average volumetric heat transfer coefficient.

Hydrate formation in layers of gas-saturated amorphous ice

Layers of amorphous ice saturated with methane, ethane, propane and carbon dioxide were obtained by condensation of molecular beams of rarefied vapor and gas on a substrate cooled with liquid nitrogen. The amorphous state of such objects at low temperatures is stabilized by the high viscosity and the small value of the stationary nucleation rate of the crystal phase. Their heating in condition of high metastability is accompanied by spontaneous explosive crystallization, which leads to the formation of gas hydrates. Glass-transition and crystallization temperatures were determined by changes in their dielectric properties under heating. An increase in the gas content in layers of amorphous ice causes an increase in the crystallization temperature without any significant changes in the glass transition temperature. At atmospheric pressure in a liquid n-pentane medium the retention of gas hydrates was observed up to temperatures close to 273K. Self-preservation ensured the retention of hydrates in a metastable state at temperatures exceeding considerably their equilibrium dissociation temperatures. Samples of gas hydrates obtained at a maximum gas flow rate during the deposition contained up to 15 mass % of methane, 12 mass % of ethane, 13 mass % of propane, and 23 mass % of carbon dioxide.

Fully atomistic molecular‐mechanical model of liquid alkane oils: Computational validation

Fully atomistic molecular dynamics simulations were performed on liquid n-pentane, n-hexane, and n-heptane to derive an atomistic model for middle-chain-length alkanes. All simulations were based on existing molecular-mechanical parameters for alkanes. The computational protocol was optimized, for example, in terms of thermo- and barostat, to reproduce properly the properties of the liquids. The model was validated by comparison of thermal, structural, and dynamic properties of the normal alkane liquids to experimental data. Two different combinations of temperature and pressure coupling algorithms were tested. A simple differential approach was applied to evaluate fluctuation-related properties with sufficient accuracy. Analysis of the data reveals a satisfactory representation of the hydrophobic systems behavior. Thermodynamic parameters are close to the experimental values and exhibit correct temperature dependence. The observed intramolecular geometry corresponds to extended conformations domination, whereas the intermolecular structure demonstrates all characteristics of liquid systems. Cavity size distribution function was calculated from coordinates analysis and was applied to study the solubility of gases in hexane and heptane oils. This study provides a platform for further in-depth research on hydrophobic solutions and multicomponent systems.

On the Behavior of Solutions of Xenon in Liquid n-Alkanes: Solubility of Xenon in n-Pentane and n-Hexane

The solubility of xenon in liquid n-pentane and n-hexane has been studied experimentally, theoretically, and by computer simulation. Measurements of the solubility are reported for xenon + n-pentane as a function of temperature from 254 to 305 K. The uncertainty in the experimental data is less than 0.15%. The thermodynamic functions of solvation such as the standard Gibbs energy, enthalpy, and entropy of solvation have been calculated from Henry's law coefficients for xenon + n-pentane solutions and also for xenon + n-hexane, which were reported in previous work. The results provide a further example of the similarity between the xenon + n-alkane interaction and the n-alkane + n-alkane interactions. Using the SAFT-VR approach we were able to quantitatively predict the experimental solubility for xenon in n-pentane and semiquantitatively that of xenon in n-hexane using simple Lorentz-Berthelot combining rules to describe the unlikely interaction. Henry's constants at infinite dilution for xenon + n-pentane and xenon + n-hexane were also calculated by Monte Carlo simulation using a united atom force field to describe the n-alkane and the Widom test particle insertion method.

The Thermal Conductivity, Thermal Diffusivity, and Specific Heat of Liquid n-Pentane

The thermal conductivity and thermal diffusivity of liquid n-pentane have been measured over the temperature range from 293 to 428 K at pressures from 3.5 to 35 MPa using a transient hot-wire instrument. It was determined that the results were influenced by fluid thermal radiation, and a new expression for this effect is presented. The uncertainty of the experimental results is estimated to be better than ±0.5% for thermal conductivity and ±2% for thermal diffusivity. The results, corrected for fluid thermal radiation, are correlated as functions of temperature and density with a maximum uncertainty of ±2% for thermal conductivity and ±4% for thermal diffusivity. Derived values of the isobaric specific heat are also given.

Temperature and Density Dependences of the Dynamics of Liquid n-Pentane Studied by Molecular Dynamics Simulation

Abstract In order to elucidate the temperature and density dependences of the power spectra of the velocity autocorrelation functions, molecular dynamics simulation of liquid n-pentane has been carried out. Strong temperature dependence is observed in the frequencies lower than ∼20 cm−1, while the variation of the density makes significant effect in the whole spectral region where low-frequency phonon modes of liquids are expected to appear.

X-ray Scattering in Liquid Pentane

X-ray diffraction investigation of liquid n-pentane CH3—(CH2)3—CH3 was performed at 293 K. An angular distribution of X-ray scattered intensity was measured by applying MoK α (γ = 0.71069 Å) radiation. The electron density radial distribution function was numerically found using Fourier analysis. The mean distances between the neighbouring atoms were found. A simple model of short-range arrangement of the molecules was proposed.

Transient hot UV spectra in the collisional deactivation of highly excited trans-stilbene in liquid solvents

Collisional energy transfer of vibrationally highly excited ground state trans-stilbene, formed by isomerization and internal conversion of electronically excited cis-stilbene, was investigated in liquid n-pentane and methanol. The temporal evolution of the trans-stilbene absorption spectrum between 295 and 310 nm was reconstructed from wavelength dependent fluorescence yields. Energy-loss profiles were generated using separate shock wave studies of stilbene high temperature spectra for calibration. Most of the vibrational energy of excited trans-stilbene is transferred to the solvent within 1–2 ps. Subsequently, the cooling process continues on a 10 ps timescale due to local heating of the liquid environment.

Cryogenic atomic force microscopy

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

High pressure study on molecular conformational equilibria of n-pentane

The n-pentane molecule has the basic conformations, TT, TG, and GG. It is important for understanding the conformational behavior of chain molecules. We have studied the effect of pressure on the conformations of n-pentane in the condensed phase by using high pressure infrared spectroscopy with a diamond anvil cell up to 28.9 kbar. Compression of liquid n-pentane increases the concentration of the more globular conformers, while the TT conformer only exists as a high pressure solid. The volume changes for TT to TG, TG to GG, and TT to GG forms are −1.0±0.2, −1.1±0.3, and −2.1±0.3 cm3/mol, at 20 °C, respectively. The conformational volume changes in liquid n-alkanes are discussed in terms of the solvent-excluded volume.

Speed-of-sound measurements for liquid n-pentane and 2,2-dimethylpropane under pressure

Speeds of sound c have been measured on isotherms between 263 K and 433 K and at pressures to 210 MPa for n-pentane and to 54 MPa for 2,2-dimethylpropane. Measurements were carried out at 3 MHz using a pulse-echo-overlap technique. Rational polynomials were used to fit the ( p, c, T) results, with root-mean-square deviations of 0.036 and 0.046 per cent for n-pentane and 2,2-dimethylpropane, respectively.

Electrical breakdown of liquid hydrocarbons in a test cell with one rotating electrode

The electrical breakdown of liquid n-pentane, n-hexane, cyclo-hexane, and n-decane was investigated in a test cell with one electrode rotating. Two different electrode geometries were used: sphere-rotating sphere and sphere-rotating plane. The applied voltage was increased slowly at a constant rate until breakdown occurred. The breakdown voltage was found to decrease with increasing rotary velocity except at very low values, where a slight increase of the breakdown voltage was observed. A simple method is presented that qualitatively explains the observed effects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

液―液直接接触式熱交換器に関する実験研究

Liquid-liquid direct contact heat exchangers have many advantages over conventional multi-tubular type exchangers from the point of view of area of heat exchange and scaling. However, the mechanism of liquid-liquid direct contact heat exchange is so complicated that many experimental researches are going on.Hot water and n-Pentane are mixed and exchanged each other in a acrylic cylinder, 40 mm dia. and 220 mm height, of our experimental apparatus.It is the main object of our research to observe flooding phenomenon of n-Pentane from the cylinder since research reports about the flooding phenomenon are very rare and a portion of liquid n-Pentane still exists in hot water at higher temperature than its boiling point. The evaporation rate of n-Pentane is an important scale of exchanged heat flux between hot water and n-Pentane.We have found evaporation rate of n-Pentane (evaporated n-Pentane/injected n-Pentane) from the measurement of flooding n-Pentane. From the measurement results, the evaporation rate (λ) is expressed by superheated temperature (ΔTW) of hot water and the mass flow rate (φ=n-Pentane/hot water) . Equation of the rate is obtained as follow;λ=1-exp{-[ΔTw-(10∅+2.0)/16∅0.6]} where ΔTW = Tl-TbTl: Inlet hot water temperature (K) . Tb : Boiling temperature of water and n-Pentane mixture (K) . φ : Mass flow rate (n-Pentane/hot water) .The equation is in accord with the experimental results in all superheated temperature region at hot water flow of 8.33×10-6 (m3/s) . And it differs about 5-10% at hot water flow of 16.7×10-6 (m3/s) . The experimental equation can be adopted to estimate evaporation rate, and the experimental process is acceptable to observe the flooding phenomenon in Liquid-Liquid Direct Contanct Heat Exchange.

Photocurrent enhancement in nonpolar liquids by the addition of electron scavengers

The photocurrent from anthracene, triphenylamine, and N,N,N',N'-tetramethyl-p-phenylenediamine excited above their ionization thresholds in liquid n-pentane or n-hexane is found to be enhanced by the addition of low concentrations (/approx lt/0.02 M) of the electron scavengers perfluoromethylcyclohexane or perfluorodecalin. The enhancement is not observed in solvents of higher electron mobility (e.g.,. cyclohexane, isooctane, etc.) or for scavengers of lower electron affinity (e.g., n-perfluorohexane). For the solute naphthalene, no enhancement is observed under any conditions. The effects of excitation energy and applied electric field strength are reported.