Dynamic specific heat of a supercooled liquid

Uncertainty analysis of FLiNaK thermophysical properties on convective heat transfer characteristics in circular tube

Sugar solutions such as sucrose, glucose and fructose are often used in osmotic dehydration processes. Thus, the experimental determination of their thermophysical properties is a must for designing purposes. Density, specific heat and thermal conductivity were determined in a wide range of solute concentration (10–60 °Brix) and temperature (273.15–358.15 K). Empirical equations were considered to fit the experimental data and to evaluate the data behavior. An assessment based on the Prandtl number was considered to correlate thermal and rheological data. Higher density and lower specific heat and thermal conductivity values were observed when temperature decreased and solute concentration increased. Prandtl number behaved similarly as density, indicating that momentum transfer is favored in comparison with heat transfer in more concentrated solutions at lower temperatures. A versatile polynomial model concerning the significant variables could predict the experimental values for all solutions with good accuracy (R2 > .9863 and MRE < 1.20%). Reported data and equations showed to be essential for engineering aspects and transport phenomena analysis.Practical ApplicationsSucrose, glucose and fructose solutions are commonly used in osmotic dehydration processes to promote solute incorporation, increasing shelf‐life and quality of food products. The availability of thermophysical properties in a wide range of solute concentration and temperature covers the most of conventional and nonconventional conditions for designing osmotic dehydration and many other food processes. Among the unit operations, it could be found pumping, mixing/stirring, pasteurization, sterilization, evaporation and so on. These data are useful to understand how properties change when the conditions are altered during the processes. They also provide important information about momentum and heat transfer through the fluid. By analyzing dimensionless parameters, as Prandtl number, one phenomenon or other can be favored under specific conditions. The presence of accurate mathematical models results in greater agility and reliability in the execution of processes, especially for those operating in wide ranges of temperature and solute concentration.

Viscosity of the supercooled liquid and relaxation at the glass transition of the Zr 46.75Ti 8.25Cu 7.5Ni 10Be 27.5 bulk metallic glass forming alloy

The effects of various parameters on the transport propenties of dissociating gaseous mixtures were studied. In order to take advantage of the increase in thermal conductivity and specific heat due to the dissociation, the heat of dissociation must be large,'' the molecular weight and molecular volume must be small, and both associated and dissociated molecules must be present in appreciable amounts at reasonable temperatures. Very few dissociation reactions meet all of these requirements. In order to illustrate the effects of dissociation on many properties, estimates were made for the thermal conductivity, specific heat, specific volume, and viscosity of helium-- aluminum chloride and helium--fluorine mixtures as a function of temperature at various pressures and compositions. The maxima in the thermal conductivity and specific heat curves, which are due to the heat of dissociation, can be varied over a wide range of temperatures by controlling the pressure and helium concertration. The dissociation produces a greater than linear increase in specific volume with increasing temperature. According to the calculations, a helium-- fluorine mixture has a thermal conductivity and specific heat which can be as much as a factor of two greater than the corresponding values for pure helium, while the viscosity of the mixture is approximately 10% greater than that of helium and is only slightly dependent on composition. The thermal properties and viscosity of helium-- aluminum chloride mixtures are considerably less than those of pure helium. (auth)

The study is dedicated to the consideration of lower alkyl ethers of glycerol as potential components of low-melting technical fluids (e.g., heat transfer fluids, hydraulic fluids, aircraft de-icing fluids, etc.). Four isomeric mixtures of glycerol ethers (GMME-monomethyl; GDME-dimethyl; GMEE-monoethyl; GDEE-diethyl) were synthesized from epichlorohydrin and methanol/ethanol in the presence of sodium and subjected to detailed characterization as pure compounds and as aqueous solutions (30-90 vol%). The temperature and concentration dependencies of density, viscosity, cloud point, boiling range, specific heat capacity, thermal conductivity, and rubber swelling were obtained. On the basis of the data obtained, a comparison was made between the aqueous solutions of glycerol ethers and of other common bases for low-melting liquids (glycerol, ethylene glycol, and propylene glycol). Pure glycerol ethers could potentially be used as technical fluids in a very wide temperature range-from -114 to 150 °C. It was further demonstrated that in low temperature applications (e.g., in low-temperature chiller systems) the glycerol-ether-based aqueous heat transfer fluids could provide enhanced efficiency when compared to the glycerol- or propylene-glycol-based ones due to their lower viscosities and favorable environmental properties.

Quasi steady state method to measure thermophysical parameters of cylindrical lithium ion batteries

Numerical investigation of acceleration effect on heat transfer deterioration phenomenon in supercritical water

Most previous analytical theories for microscale heat transfer are limited to low temperatures (≤100 K). We present simple yet general analytical formulae which reveal the essential features of the thermal properties of two-dimensional nanomaterials in a wide range of temperatures by full coverage of guided wave and bulk wave modes. In particular, we are able to handle the intermediate ballistic-diffusive regime. As an illustration, the formulae are applied on graphene to obtain its specific heat, thermal conductance, and thermal conductivity. The predictions are remarkably consistent with existing theories and experiments.

The development of resource-saving technologies for obtaining pure sea buckthorn oil and its compositions with other vegetable oils from dried crushed sea buckthorn cake is an urgent task. Sea buckthorn oil and its mixtures are obtained by extraction and simultaneous heat exposure, electrophysical methods of the process intensifying being considered in this case. Currently, there are no reliable data on the thermo- and electrophysical properties of dried crushed sea buckthorn cake at atmospheric pressure in the literature. Therefore, experimental studies of the thermo- and electrophysical properties of dried crushed sea buckthorn cake in a wide range of changes in state parameters are of great importance for solving theoretical and practical problems. The nature of the change in the specific heat, thermal conductivity and thermal diffusivity in the temperature range 20 ... 80 ° C and humidity 7.0 ... 17.5% was determined to be linear. In this case, the specific heat and the coefficient of thermal conductivity increase with increasing temperature while the coefficient of thermal diffusivity decreases. The nonlinear dependence of the dielectric loss coefficient on moisture was found to be due to a variety of forms of moisture binding in the sea buckthorn cake particles. It is obvious that with an increase in the cake temperature and humidity, the dielectric loss coefficient monotonically nonlinearly increases in the range of 0.46 ... 9.72. Empirical equations that make it possible to reliably determine the value of the specific mass heat capacity, thermal conductivity coefficients, thermal diffusivity and dielectric losses of dried crushed sea buckthorn cake from temperature and humidity in the range of 7.0 ... 17% with respect to absolutely dry matter were obtained as a result of studies of thermo- and electrophysical properties..

In the present article, using the methods of mathematical modeling, the thermal conductivity of silicon was obtained in a wide temperature range (0.3 ≼ T ≼ 3 kK), including the region of semiconductor-metal phase transformations. As it is known, there are two mechanisms of heat transfer in a solid: elastic lattice vibrations and free electrons, therefore, in the study of the thermal conductivity of silicon, the lattice and electronic components were taken into account. The lattice (phonon) thermal conductivity in this work was determined within the framework of the atomistic approach. The Stillinger–Weber and Kumagai–Izumi–Hara–Sakai interaction potentials were used for modeling. The results of the comparison of the phonon thermal conductivity obtained from the simulation results with the used interaction potentials are presented. The modeling of the thermal conductivity of the electronic subsystem of silicon with intrinsic conductivity in this work is based on the use of the quantum statistics of the electron gas using the Fermi–Dirac integrals. The total thermal conductivity of silicon, obtained as the sum of the electronic and phonon components, is compared with the experimental data.

Thermal conductivity transition regime of zigzag and armchair black phosphorus

Incorporating graphene nanoparticles with high thermal conductivity into a lead-based coolant can significantly increase its thermal conductivity and specific heat capacity, thereby increasing the core power density of lead–bismuth cooled reactors, reducing the amount of coolant required, and ultimately realizing a miniaturized and lightweight reactor design. The purpose of the design is of great significance to the engineering application of lead–bismuth stacks in remote areas and open seas. In this study, the thermophysical properties of metal-based graphene nanofluids are analyzed by comparing and analyzing prediction models established for the thermal conductivity, viscosity, and specific heat capacity. The strengthening mechanism of nanofluids is summarized, and a series of suitable calculation formulae for the thermophysical properties of lead–bismuth-based graphene nanofluids is proposed. The research results show that incorporating graphene nanoparticles into a lead–bismuth-based coolant can significantly improve its thermal conductivity and specific heat capacity. When the nanoparticle suspension is relatively stable, the thermal conductivity, specific heat capacity, and viscosity increase significantly with the concentration of graphene nanoparticles. When the concentration reaches 20%, the thermal conductivity and specific heat capacity of the nanofluid are enhanced by approximately 80 and 20%, respectively, whereas the viscosity is also increased by approximately 100%. Therefore, it is important to appropriately select the parameters for the addition of nanoparticles to maximize the effect of lead–bismuth-based graphene nanofluids on the heat transfer performance of the reactor core.

Temperature dependences of piezoelectric properties were studied for h001i textured ceramics of bismuth layer-structured ferroelectrics, SrBi(2)Nb(2)O(9) (SBN). The textured ceramics with varied orientation degrees were fabricated by templated, grain-growth method, and the temperature dependences of resonance frequency were estimated. Excellent temperature stability of resonance frequency was obtained for the 76% textured ceramics. The resonance frequency of the 76% textured specimens varied almost linearly over a wide temperature range. Therefore, the variation was slight, even in a high temperature region above 150 degrees C. Temperature stability of a quartz crystal oscillator is generally higher than that of a ceramic resonator around room temperature. The variation of resonance frequency for the 76% textured SrBi(2)Nb(2)O(9) was larger than that of oscillation frequency for a typical quartz oscillator below 150 degrees C also in this study. However, the variation of the textured SrBi(2)Nb(2)O(9) was smaller than that of the quartz oscillator over a wide temperature range from -50 to 250 degrees C. Therefore, textured SrBi(2)Nb(2)O(9) ceramics is a major candidate material for the resonators used within a wide temperature range.

Thermal-physical properties of nanoparticle-seeded nitrate molten salts

Thermal conductivities of Green River oil shales vary fourfold, decreasing with increasing oil yield and temperature. Values also decrease as the kerogen decomposes, but these changes are small after about 9 hours. Mineral composition, geographic location, depth of burial, axial stress, and pressure have no significant erect. The thermal properties, which are transversely isotropic, are applicable to the calculation of heat losses from in-situ recovery operations. Introduction Thermal decomposition of the essentially insoluble organic matter in oil shales is the easiest way to obtain shale oil. Proper planning of both surface and sub-surface thermal oil-shale recovery operations requires values of the thermal conductivity and diffusivity of oil shales.There are few publications reporting thermal conductivities of oil shale from the Green River formation. Gavin and Sharp reported three values for the thermal conductivity of an oil-shale sample assaying 42.7 gal/ton. Their reported values were obtained over the temperature range from 77 degrees to 167 degrees F, but the direction with respect to the bedding plane in which the measurements were taken was not indicated. Thomas presented thermal conductivity data of an oil shale assaying 30 gal/ ton and at a mean temperature of 104 degrees F, finding values parallel to the bedding plane to be 30 percent higher than those normal to it and finding essentially no effect of stress levels of 1,000 psi and above.Tihen et al. report on the thermal conductivity and diffusivity at room temperature of unconfined raw, retorted, and burned oil shales assaying from 8.6 to 58.6 gal/ton. Correlations for thermal conductivity are given for temperatures as high as 1,100 degrees F while considering the anisotropic character of the oil shales. Though bolted, samples developed cracks during heating, suggesting those results may be more applicable to rubbled pieces in subsurface cavities or large surface retorts than to the calculation of heat losses from a process zone in subsurface thermal operations.This report presents thermal conductivity data of confined Green River oil shales over a wide range of temperature, fluid pressure, axial stress, and kerogen content. The bulk of our measurements were carried out on oil shales as they are found in nature; that is, they were not previously retorted. At the higher temperatures, however, our reported values include the effects of at least some decomposition of the organic matter. Thermal conductivities of burned (organic-free) oil shales were measured on only two samples.The effects of kerogen content, fluid pressure, axial stress, temperature, orientation, heating time, and mineral composition on the thermal conductivities of oil shales were investigated. These basic results were then used together with specific gravity and a correlation of specific heat with oil yield by Fischer assay and temperature to obtain calculated thermal diffusivities for each sample. Instrumentation The transient line heat-source (probe) method, whose application is not particularly complicated by the addition of means for stressing the sample, was used in our investigation. JPT P. 97