Bulk Heat Capacity Research Articles

The effect of temperature and pressure on the physicochemical properties of petroleum diesel oil and biodiesel fuel

Three commercial fuels were studied: biodiesel (based mainly of the fatty acids methyl esters of rapeseed oil), diesel oil Ekodiesel Ultra (standard petroleum diesel oil with sulphur content less than 10mg/kg), and ON BIO 10 (blend of 20vol.% of biodiesel with 80vol.% of standard petroleum diesel oil with sulphur content less than 10mg/kg). The speeds of sound were measured within the temperatures from 293 to 318K and at pressures from 0.1 to 101MPa. The densities and heat capacities were measured under atmospheric pressure in the temperature range from 273 to 363K and 283 to 359K, respectively. Using the experimental results, the physicochemical properties such as: density, isentropic bulk modulus, heat capacity, and isobaric thermal expansion were calculated in the same temperature and pressure range as the speed of sound was measured. The results obtained show that although the bulk modulus of ON BIO 10 is higher than that of diesel oil Ekodiesel Ultra over the whole pressure range, the difference is rather small and can be compensated by temperature. Isobaric thermal expansivity of biodiesel decreases with pressure slightly less than that of the diesel oil Ekodiesel Ultra. It is approximately independent of temperature and composition of the fuel at pressures 40±5MPa.

Retrieval of Model Grid-Scale Heat Capacity Using Geostationary Satellite Products. Part I: First Case-Study Application

Abstract In weather forecast and general circulation models the behavior of the atmospheric boundary layer, especially the nocturnal boundary layer, can be critically dependent on the magnitude of the effective model grid-scale bulk heat capacity. Yet, this model parameter is uncertain both in its value and in its conceptual meaning for a model grid in heterogeneous conditions. Current methods for estimating the grid-scale heat capacity involve the areal/volume weighting of heat capacity (resistance) of various, often ill-defined, components. This can lead to errors in model performance in certain parameter spaces. Here, a technique is proposed and tested for recovering bulk heat capacity using time tendencies in satellite-retrieved surface skin temperature (SST). The technique builds upon sensitivity studies that show that surface temperature is most sensitive to thermal inertia in the early evening hours. The retrievals are made within the context of a surface energy budget in a regional-scale model [the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)]. The retrieved heat capacities are used in the forecast model, and it is shown that the model predictions of temperature are improved in the nighttime during the forecast periods.

Evaluation of new diesel particulate filters based on stabilized aluminium titanate

A new generation of wall-flow diesel particulate filters based on an aluminium titanate composition has recently been developed by Corning, and marketed as the Corning Dura-Trap AT filter. The new material combines extremely high resistance to thermal stresses with a high bulk heat capacity. In this article, the test results obtained with this new material in laboratory tests, engine bench experiments and on-road vehicle durability runs are presented and discussed.

Breathing Mode Dynamics and Elastic Properties of Gold Nanoparticles

We present calculations of the bulk modulus, heat capacity, and the period of the breathing mode for spherical nanoparticles following excitation by ultrafast laser pulses. The bulk modulus and heat capacities both exhibit clear transitions upon bulk melting of the particles. Equilibrium calculations of the heat capacity show that the melting transition is sharper and occurs at a lower temperature than one would observe from an ultrafast experiment. We also observe an intriguing splitting in the low-frequency spectra of the nanoparticles and analyze this splitting in terms of Lamb's classical theory of elastic spheres. We conclude that the particles either (1) melt during the observation period following laser excitation or (2) melt an outer shell while maintaining a crystalline core. Both mechanisms for melting are commensurate with our observations.

Molecular dynamics study on the structural and thermodynamic properties of the zinc-blende phase of GaN at high pressures and high temperatures

The structural and thermodynamic properties of zinc-blende phase of GaN have been investigated systematically using the molecular dynamics method with Buckingham potential model. These properties including lattice constant, phase transition pressure (from the zinc-blende to the rock-salt structure), thermal expansion, isothermal bulk modulus, and heat capacity at constant pressure were calculated in a wide range of temperatures (300—3000K) and pressures (0—65GPa). The structural and thermodynamic parameters obtained under normal state are found to be in good agreement with the existing experimental and theoretical results. Meanwhile, some thermodynamic parameters such as isothermal bulk modulus and heat capacity at constant pressure have been predicted at elevated temperatures and high pressures based on the reliable potential model. The simulated results are of fundamental importance in material science.

Heat capacity effects associated with the hydrophobic hydration and interaction of simple solutes: a detailed structural and energetical analysis based on molecular dynamics simulations.

We examine the SPCE [H. J. C. Berendsen et al., J. Chem. Phys. 91, 6269 (1987)] and TIP5P [M. W. Mahoney and W. L. Jorgensen, J. Chem. Phys 112, 8910 (2000)] water models using a temperature series of molecular-dynamics simulations in order to study heat-capacity effects associated with the hydrophobic hydration and interaction of xenon particles. The temperature interval between 275 and 375 K along the 0.1-MPa isobar is studied. For all investigated models and state points we calculate the excess chemical potential for xenon employing the Widom particle insertion technique. The solvation enthalpy and excess heat capacity is obtained from the temperature dependence of the chemical potentials and, alternatively, directly by Ewald summation, as well as a reaction field based method. All three methods provide consistent results. In addition, the reaction field technique allows a separation of the solvation enthalpy into solute/solvent and solvent/solvent parts. We find that the solvent/solvent contribution to the excess heat capacity is dominating, being about one order of magnitude larger than the solute/solvent part. This observation is attributed to the enlarged heat capacity of the water molecules in the hydration shell. A detailed spatial analysis of the heat capacity of the water molecules around a pair of xenon particles at different separations reveals that even more enhanced heat capacity of the water located in the bisector plane between two adjacent xenon atoms is responsible for the maximum of the heat capacity found for the desolvation barrier distance, recently reported by Shimizu and Chan [J. Am. Chem. Soc. 123, 2083 (2001)]. The about 60% enlarged heat capacity of water in the concave part of the joint xenon-xenon hydration shell is the result of a counterplay of strengthened hydrogen bonds and an enhanced breaking of hydrogen bonds with increasing temperature. Differences between the two models with respect to the heat capacity in the xenon-xenon contact state are attributed to the different water model bulk heat capacities, and to the different spatial extension of the structure effect introduced by the hydrophobic particles. Similarities between the different states of water in the joint xenon-xenon hydration shell and the properties of stretched water are discussed.

Magnetic properties of the low-dimensional cuprateNa5RbCu4(AsO4)4Cl2

The magnetic properties of a new compound, Na5RbCu4(AsO4)4Cl2 are reported. The material has a layered structure comprised of square Cu4O4 tetramers. The Cu ions are divalent and the system behaves as a low-dimensional S=1/2 antiferromagnet. Spin exchange in Na5RbCu4(AsO4)4Cl2 appears to be quasi-two-dimensional and non-frustrated. Measurements of the bulk magnetic susceptibility and heat capacity are consistent with low-dimensional magnetism. The compound has an interesting, low-entropy, magnetic transition at T = 17 K.

Dielectric and thermal studies of inorganic microfillers on polymer microwave substrates—metallocene cyclic olefin copolymers (COC)

Metallocene cyclic olefin copolymers (mCOCs) are considered as potential candidates for both optical markets and electric applications because of their high transparency in the visible and near UV regions, and their high electrical resistance. In the microelectronic packaging industries, the propagation velocity of electromagnetic waves on the substrates is inversely proportional to the square root of the dielectric constant. Additionally, extents of energy losses and the elimination of stray electromagnetic radiation are all related to Dk properties. As a result, finding a way to lower Dk values for packaging materials is a trend in high-performance computing devices. This paper investigates the dielectric and thermophysical properties of mCOC by adding to it various proportions of microfillers. Three microfillers, all made up of soda-lime-borosilicate glass, were used in the tests. One of the microfillers was the original glass without surface treatment, while the other two have the methacrylato chromic chloride (MCC) treatment, and epoxy silane treatment, respectively. They were mixed with the melted mCOC and then molded to disks of 30 mm diameter and 1 mm thickness. Thermophysical properties such as the bulk density, heat capacity and thermal conductivity were measured at room temperature to understand the thermal stability and heat transport performance of the composites. Additionally, dielectric properties were measured at room temperature at 1 MHz frequency, in order to evaluate electronic wave transport characteristics and extent of energy loss.

Measuring Soil Water Content, Electrical Conductivity, and Thermal Properties with a Thermo-Time Domain Reflectometry Probe

Hydraulic and thermal regimes are coupled in surface soil. Accurate measurement of soil volumetric water content (θ) and thermal properties will improve our understanding of the hydraulic and thermal regimes. A thermo-time domain reflectometry (TDR) probe was developed to simultaneously measure θ, bulk electrical conductivity (σ), thermal conductivity (λ), heat capacity (ρc), and thermal diffusivity (α). Time domain reflectometry was used to measure θ and σ, and the dual-probe heat pulse (DPHP) method was used to determine λ, ρc, and α. Laboratory tests on two soils showed that the probe determined θ accurately and the measured σ values of saturated soil correlated well with values determined by a four-electrode probe. Measurements in agar-immobilized water produced values of λ and ρc that closely corresponded with standard values of these properties for water, an indication of the sensor's functionality in other media. Soil thermal properties as a function of θ also are presented. The results of these laboratory tests suggest that the thermo-TDR probe can be a valuable tool for simultaneously monitoring θ, σ, and soil thermal properties.

Pressure- and temperature-dependent micellization of a poly(ethylene oxide)poly(propylene oxide) triblock copolymer in aqueous solutions

Bulk moduli, densities, and heat capacities of aqueous solutions of a triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer with average composition (EO) 28 (PO) 48 (EO) 28 (where EO is ethylene oxide, PO is propylene oxide) and homopolymers with average compositions (EO) 133 and (PO) 37 have been measured as a function of temperature and concentration. Block copolymers form micelles with increasing temperature. Micellization is shown to be an endothermic transition with a ΔH of 50 ± 4 J g -1 of copolymer and with an increase of the apparent copolymer volume of 0.029±0.003 ml g -1 . The measured storage bulk moduli show that the dissolved unimer structures are nearly incompressible. The modulus decreases during micellization for copolymers or phase separation for poly(propylene oxide) (PPO). A simple two-phase model of micelles with a core of pure PPO and a mantle of water-swollen poly(ethylene oxide) chains describes both the measured bulk moduli and volume properties well. The relaxation time for unimer to micelle dynamics has been estimated from the loss bulk modulus maximum with temperature to be approximately 1 μs at 20° C.

A model for the nonradiative decay of organic phosphor triplet states in solid matrices

The heat capacities of sodium acetate NaCl mixtures and 30% β-cyclodextrin NaCl were obtained over a wide temperature range. These data in addition to heat capacity data from the literature for sodium acetate and NaCl were related to the phosphorescence lifetimes of several phosphors adsorbed individually on sodium acetate, sodium acetate NaCl , and 30% β- cyclodextrin NaCl . Several linear relationships were obtained between a phosphorescence lifetime function and the reciprocal of the bulk heat capacity data for the phosphors adsorbed on the solid matrices. In addition, consideration was given to the solid-matrix phosphorescence quantum yields of the phosphors. The relationships developed were related to solid-state theories and organic luminescence theory. The bulk heat capacity had an influence on the phosphorescence lifetime, and low-frequency vibrational modes in the solid matrices were activating vibrational modes in the excited triplet state of the phosphors which caused nonradiative transitions from the excited triplet state. These results have important implications in room-temperature solid-matrix phosphorescence analysis because a model was developed that explains some of the details of the nonradiative transition from the excited triplet state of a phosphor adsorbed on a solid matrix.

Surface specific heat of4He confined to 8-micron cylinders near the λ-point

We report measurements of the deviations from bulk heat capacity of4He confined to 8-micron cylinders in the cross-over region away from the lambda point on both sides of the transition. We compare our results with theoretical calculations based on the application of Dirichlet boundary conditions to the order parameter, and with extrapolations based on earlier measurements of the specific heat of confined helium. We find that our data somewhat favors the theoretical prediction.

Exact results in linear thermomechanics of fluid-saturated porous media

Exact results are derived relating the various bulk moduli (frame, unjacketed, and pore) and heat capacity of inhomogeneous fluid-saturated porous media to the pertinent thermal expansion coefficients and component moduli when only two porous solid constituents are present. The porous solids need not be space filling or in perfect welded contact, so these results apply to materials containing some voids or cracks interspersed between the two constituents in addition to the interior voids associated with their pores. The key ratio of fluid pressure to temperature change producing uniform expansion or contraction is shown to be independent of porosity.

Bulk thermal capacity determination for Li/BCX and Li/SOCl 2 cells

The bulk heat capacities of Li/BCX and Li/SOCl 2 cells were determined at 0 and 100% depth-of-discharge for 2.0 V cut-off voltage, in the temperature range 0 to 60 °C by a method that did not involve the destruction of the cell nor the contact of cell with a liquid. The heat capacity of Li/BCX cell is an important parameter for the design of a thermal control system for Li/BCX batteries. The heat capacities are found to be dependent on state-of-charge — increasing with depth-of-discharge. The Li/BCX DD-cell has a lower heat capacity (0.154 to 0.201 cal/(g K)) than a high rate Li/SOCl 2 D-cell (0.191 to 0.221 cal/(g K)). The results obtained by this method compare favorably well with results reported in the literature through other methods. The bulk heat capacities of the cells did not change significantly in the temperature range 0 to 60 °C.

Evaporative dissociation of ammonia cluster ions: quantification of decay fractions and isotope effects

A modified version of the evaporative ensemble model is employed to deduce relative binding energies for protonated cluster ions using previously measured metastable dissociation fractions of ammonia cluster ions, (NH{sub 3}){sub n}H{sup +}, n = 4-22, obtained by using a laser-based time-of-flight mass spectrometer equipped with a reflection. The newly derived values are found to be in good agreement with those reported earlier based on high-pressure mass spectrometry (HPMS) and several other methods employing data on dissociation dynamics. The various methods are found to be complementary. New measurements are reported for the metastable decay of deuterated cluster ions to investigate the influence of mass effects on the dissociation rate. The decay fractions of the cluster ions (ND{sub 3}){sub n}D{sup +} are found to be consistently higher than those of the corresponding (NH{sub 3}){sub n}H{sup +} by 15%. The isotope effect can be well accounted for by considering the differences of their bulk heat capacities, and such studies are found to be a promising method for measuring the heat capacities of small, unsupported cluster systems.

Design and Critical Appraisal of an Accelerated Integration Procedure for Atmospheric GCM/Mixed-Layer Ocean Models

An accelerated integration procedure (AIP) is developed for the OSU atmospheric GCM/mixed-layer ocean model. In this AIP the depth of the mixed-layer ocean is reduced by an acceleration factor {ital f}{sub {ital a}}=12 from 60 m to 5 m and the length of a solar cycle is correspondingly reduced to eliminate the increase in the amplitude of the annual cycle of oceanic temperature which would otherwise occur. Furthermore, the ground bulk heat capacity, ground water field capacity and heat of fusion for sea ice for snow on sea ice are reduced by {ital f}{sub {ital a}} to accelerate the equilibration of the ground temperature, soil water and sea ice, respectively.

Assessment of bulk modulus, thermal expansion and heat capacity of minerals

Since the heat capacity of a solid at constant pressure ( C P ) is related to the isothermal bulk modulus ( K T ) and isobaric thermal expansion ( α P ), an assessment of the experimental data on these properties is necessary to establish the internal consistency of a thermodynamic data set. Through suitable formulations of the temperature dependence of bulk modulus, thermal expansion and heat capacity at constant volume ( C V ) and the application of non-linear programming techniques, it is possible to assess the internal consistency of these data and the measured heat capacity at constant pressure. Such optimization of the data on periclase has been performed with the following results: α P = 0.3754 × 10 −4 + 0.791 × 10 −8 T − 0.784 T −2 + 0.9148 T −3 (11) K T = 1.684 × 10 6−241 T − 0.056 T 2 + 0.167 × 10 −4 T 3( bar) (12) C V = 48.02 − 0.572 × 10 6 T(13) −2 − 0.4876 × 10 11 T −4 − 0.1502 × 10 12 T −6 + 0.9836 × 10 20 T −8 V (1, 298) = 11.245 (cm 3/mol). (14) If appropriate C P data are available, it is possible to estimate the temperature dependence of α P and K T for any solid. In suitable cases, the method may be used through a combination of the data on C P and phase equilibrium to calculate K t , its pressure derivative and thermal expansion. Such optimized data for brucite are: H 0 f (1, 298.15) = −924620, S 0(1, 298.15) = 64.08 α P = 0.1002 E − 4 + 0.1468 E − 7 T + 1.8606 T −2 (18) k t = 0.5712 Mb, ( ∂K T ∂P) = 4.712 C v = 118.58 − 0.639 E + 7 T −2 + 0.34574 E + 12 T −4 − 0.10538 E + 17 T −6. (19)

Thermodynamic properties of solid sodium from quasiharmonic lattice dynamics and molecular dynamics

Quasiharmonic-lattice-dynamics and molecular-dynamics calculations were performed on metallic sodium from the low-temperature region to above melting at several different volumes. A pseudopotential model was used that consisted of a large volume-dependent potential plus a small effective two-body potential. From the molecular-dynamics results for the solid phase, we have constructed the Helmholtz free energy and calculated the thermodynamic properties up to the melting temperature. The anharmonic contributions to the internal energy and pressure are determined directly from molecular dynamics without using thermodynamic perturbation theory. Calculated and experimental values of the zero-pressure volume-temperature curve, isothermal bulk modulus, heat capacity, and Gr\"uneisen parameter are found to be in good agreement. We conclude that the pseudopotential model provides an accurate representation of the potential for energies up to melt; molecular-dynamics simulations accurately represent the classical vibrational contributions to the thermodynamic functions at high temperatures and give a meaningful evaluation of the anharmonicity. The combination of quasiharmonic-lattice-dynamic theory in the quantum regime and molecular dynamics in the classical regime provide a simple and natural representation of the vibrational thermodynamics of a solid.

Some Thermal Effects of Bubbles in Temperate Glacier Ice

AbstractGas bubbles in core samples from the Blue Glacier, Washington, were observed to be partially filled with liquid. The time and spatial dependence of liquid content in the bubbles demonstrates that thein situliquid content of the bubbles was small and liquid appeared in the bubbles as a consequence of heat flow into the sample after collection. An effective bulk heat capacity for wet bubbly ice is derived and used to analyze the relaxation process and it is shown that the warming of samples is controlled by an effective heat capacity two or more orders of magnitude larger than for pure ice. The relaxation process presents a practical difficulty for measurement ofin situwater content from core samples and the behavior of the bubbles indicates that at positions in a temperate glacier where bubbles have pressure in excess of the ice stress, bubbles may control the ice temperature and significantly restrict water flow through veins.

Some Thermal Effects of Bubbles in Temperate Glacier Ice

AbstractGas bubbles in core samples from the Blue Glacier, Washington, were observed to be partially filled with liquid. The time and spatial dependence of liquid content in the bubbles demonstrates that the in situ liquid content of the bubbles was small and liquid appeared in the bubbles as a consequence of heat flow into the sample after collection. An effective bulk heat capacity for wet bubbly ice is derived and used to analyze the relaxation process and it is shown that the warming of samples is controlled by an effective heat capacity two or more orders of magnitude larger than for pure ice. The relaxation process presents a practical difficulty for measurement of in situ water content from core samples and the behavior of the bubbles indicates that at positions in a temperate glacier where bubbles have pressure in excess of the ice stress, bubbles may control the ice temperature and significantly restrict water flow through veins.