Heat Capacity Of Sample Research Articles

Preparation and study on thermophysical properties of inorganic salt hydrate as energy storage materials

In this paper, the preparation methods of new inorganic salt hydrate mixtures and their experimentally tested thermophysical properties are presented. Two inorganic salt hydrates mixed together at different weight proportions to study their thermodynamic properties for energy storage applications. Three samples having weight proportions of salt mixtures as 70:30, 80:20 and 90:10 are prepared and Differential Scanning Calorimetry (DSC) is used as a thermal analyzer to find the thermal stability of the samples. The DSC results of the salt hydrate are observed for determining the melting temperatures, latent heats and specific heats during melting and freezing process. The melting point, heat of fusion, and heat capacity of the salt hydrate samples are observed as 46.6 °C , 133.81 J/g and 8.75 J/gK for 70:30, 47.28 °C, 169.91 J/g and 15.95 J/gK for 80:20 and 47.26 °C, 173.96 J/g and 14.20 J/gK for 90:10. The time requirements for the completion of melting and freezing process of the salt mixture results are compared. Thermal and heat transfer characteristics of the newly prepared salt mixtures are experimentally investigated for the purpose of recommending it to use as thermal energy storage medium. The inexpensive inorganic salt hydrate mixtures, with greater enthalpy, higher heat storage capacity and good thermal reliability, shows great potential for heat storage applications in the low temperature solar thermal applications like water heaters, building space heating applications, domestic solar cookers and dryers.

Specific heat and thermal conductivity of municipal solid waste and its effect on landfill fires

Municipal Solid Waste (MSW) landfills are sources of physical, chemical and microbiological processes and as a result, gases and heat are generated as by-products. The generated heat flows from the higher to lower temperature regions within the landfill. Specific heat and thermal conductivities are two important properties that determine heat flow in MSW landfills. The goal of this study was to determine the thermal conductivity and specific heat capacity of MSW samples of Indian origin and to study its effect on landfill fires. Thermal conductivity and specific heat capacity of waste samples collected from dumpsite at Bhandewadi landfill, Nagpur & Bellahalli landfill, Bangalore (India) and the synthetic MSW (prepared in the lab) were determined using newly designed and fabricated experimental set-up. Results showed that moisture and organic content of MSW are directly proportional to specific heat capacity and indirectly proportional to thermal conductivity. Thermal conductivity of MSW is directly proportional to its density and specific heat is indirectly proportional to the density of MSW. MSW with specific heat and thermal conductivity in the range 0.003 J/g. K − 0.47 J/g. K and 0.35–3.6 J/s. m. K, respectively were found between 30 and 75 °C with 5% to 25% moisture content. As the temperature increases above 75 °C, decrease in thermal conductivity & increase in specific heat was observed and thermal conductivity of 0.07 J/s. m. K was observed at 130–140 °C. As a result of this, heat does not flow and gets concentrated in that region leading to landfill fire.

Synthesis, Structure, and Thermophysical Properties of EuGaGe2O7

The europium gallium germanate EuGaGe2O7 has been prepared by solid-state reaction in air in the temperature range 1273–1473 K using a stoichiometric mixture of Eu2O3, Ga2O3, and GeO2. Its crystal structure has been determined by X-ray diffraction (sp. gr. P21/c, a = 7.1693(7) A, b = 6.57008(6) A, c = 12.7699(1) A, β = 117.4522(5)°, V = 533.768(8) A3). The heat capacity of polycrystalline samples has been determined by differential scanning calorimetry in the temperature range 350–1053 K and the experimental data have been used to calculate the thermodynamic properties (enthalpy increment, entropy change, and reduced Gibbs energy change) of EuGaGe2O7.

Journal of Physics: Conference Series High-pressure specific heat technique to uncover novel states of quantum matter

AC-specific heat measurements remain as the foremost thermodynamic experimental method to underpin phase transitions in tiny samples. However, its performance under combined extreme conditions of high-pressure, very low temperature and intense magnetic fields needs to be broadly extended for investigation of quantum phase transition in strongly correlated electron systems. In this communication, we discuss the determination of specific heat on the quantum paramagnetic—insulator SrCu2(BO3)2 by applying the AC-specific heat technique under extreme conditions. In order to apply this technique to insulating samples we sputtered a metallic thin film-heater and attached thermometer onto sample. Besides that, we performed full frequency scans with the aim to get quantitative specific heat data. Our results show that we can determine the sample heat capacity within 5% of accuracy respect to an adiabatic technique. This allows to uncover low energy scales that characterize the ground state of quantum spin entanglement in SrCu2(BO3)2.

Heat Capacity of Compounds in the Bi2O3–TiO2 System

The Bi12TiO20, Bi4Ti3O12, and Bi2Ti4O11 bismuth titanates have been prepared by solid-state reactions, via multistep firing of stoichiometric mixtures of their constituent oxides in air at temperatures from 1003 to 1273 K (Bi12TiO20, to 1123 K). The heat capacity of polycrystalline samples of the synthesized compounds has been determined by differential scanning calorimetry in the temperature range 330–1050 K. The Cp(T) curves of Bi4Ti3O12 and Bi2Ti4O11 show peaks at temperatures of 943 and 509 K, respectively, due to ferroelectric phase transitions. The experimental data have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy change of the bismuth titanates.

Characteristics study of foulants on air cooled heat exchangers of a gas processing plant in the Middle East

Fouling of heat exchangers in energy and power plant industry, oil and gas industry, pharmaceutical and food process industry, industrial waste heat recovery is a major problem which needs to be solved urgently. In the United Arab Emirates, a majority of oil & gas processing plants are located in the desert where water accessibility is limited, thus fin-fan type of heat exchangers are used for cooling and/or heating applications. Such harsh environments cause external fouling which becomes an unavoidable problem in these heat exchangers. With increased humidity and high process temperatures, the dust particulates start to stick on the outer surface of heat exchangers which drastically reduces the thermal performance and increases power consumption. In order to identify possible methods to control and/or eliminate such kinds of external fouling, it is important to identify the composition and morphology of such foulants. This study presents the characterization of selected fouling samples collected from several fin-fan type air cooled heat exchangers taken from a gas processing plant. Scanning electron microscope (SEM) tests were carried out to determine the physical characteristics of sample foulant. Variability in sizes and shapes was found between samples due, perhaps, to different working temperature ranges of the selected heat exchangers. X-ray diffraction (XRD) analyses revealed presence of quartz, calcite, and alumina with traces of halite and hematite. Laser flash analysis (LFA) was conducted to quantify the specific heat capacity, thermal diffusivity and thermal conductivity of the fouling samples. The diversity of these fouling samples reflects complexity with respect to their potential removal and effects on heat transfer characteristics. Though, this research work is a case study for a specific petrochemical plant, however, findings in this study can be adopted by other industries involved in similar chemical processing in the Middle East as well as other countries having similar weather and geological conditions.

Heat capacity and thermal diffusivity of heavy oil saturated rock materials at high temperatures

As well-known the rate of heat extraction depends on the thermal conductivity, $$Q = - \, \lambda \left( T \right){\text{grad }}T$$ , and the fluids flow characteristics, while amounts of heat recovery depends on heat capacity of reservoir rocks, $$Q = \left( {1 - \phi } \right)\rho C_{\text{P}} T$$ , where $$\phi$$ is the porosity. In the present work the laser-flash (LFA 457) and differential scanning calorimeter (DSC 204 F1) techniques were employed on a heavy oil saturated natural rock sample for accurate measurements of the thermal diffusivity and heat capacity over a temperature range from (294 to 1024) K and from (306 to 771) K, respectively. The density of the sample at room temperature was 2300 kg m−3 and the porosity was 17.1%. The sample for the present study comes from Russian Oil Field (Eastern Siberia, Russia). The expanded uncertainty of the thermal diffusivity and heat capacity measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be 3% and 1%, respectively. At low temperatures (below approximately 373 K), the sharp increases (up to η = 2.3) of the thermal diffusivity anisotropy was observed. Based on the measured thermal diffusivity and heat-capacity data, thermal conductivity of the same oil saturated rock sample was calculated using the thermodynamic relation $$\lambda = a\rho C_{\text{P}}$$ . The effect of temperature and various physical and chemical processes, such as thermal decomposition (chemical reactions) of pore heavy oil occurred in the sample during the heating in distinct temperature ranges were studied. The effect of pore heavy oil decomposition (under thermal stress) on the measured values of heat capacity and other thermophysical properties of rock sample at high temperatures (around 700 K) was experimentally observed. Also, we experimentally found weak temperature maximum of the heat-capacity of the sample under study in the low temperature range (around 380 K).

MAGNETOCALORIC EFFECT AND HEAT CAPACITY OF MAGNETIC FLUIDS

The magnetic fluids based on magnetite nanoparticles were synthesized using mixed surfactants (oleic acid/alkenyl succinic anhydride) dispersed in different carrier media (polyethylsiloxane and dialkyldiphenyl). The physicochemical properties of magnetic fluids (density, viscosity, saturation magnetization, magnetic phase concentration, magnetic core size) were determined. Magnetic fluids are stable in a wide temperature range. All the samples of the magnetic fluids exhibit typical superparamagnetic behavior. The magnetocaloric effect and the specific heat capacity of the magnetic fluids were first direct determined at 288–350 K in a magnetic field of 0–1.0 T. The field dependences of the magnetocaloric effect have a classic linear form. The temperature dependences of the magnetocaloric effect of magnetic fluids in magnetic fields have an extreme character. Thermodynamic parameters of magnetic fluids (magnetization namely enthalpy/entropy change) were determined. The specific heat capacity of magnetic fluid samples in a zero magnetic field was obtained at different temperatures (at 278–350 K) on a differential scanning calorimeter and on the original microcalorimeter. The temperature dependences of the heat capacity of magnetic fluids in magnetic fields have an extreme character. It was established that the difference in heat capacity values obtained in and without the magnetic field is within the experimental error. The extreme character of the heat capacity is reflected in the magnetocaloric effect temperature dependences.

Thermodynamic Properties of Nanosized Cobaltite (Nickelite) Cuprate Manganites LaMgCoCuMnO6 and LaMgNiCuMnO6

The temperature dependences of the specific heat capacities of nanosized samples of lanthanum magnesium cobaltite cuprate manganite LaMgCoCuMnO6 and lanthanum magnesium nickelite cuprate manganite LaMgNiCuMnO6 are studied via calorimetry in the temperature range of 298.15–673 K. Curve $$C_{p}^{ \circ }$$(T) shows that LaMgCoCuMnO6 and LaMgNiCuMnO6 undergo second-order phase transitions at 398 and 523 K, respectively. The standard specific heat capacities of the above compounds are calculated with independent means based on characteristic Debye temperatures determined via the Koref and Nernst–Lindemann equations. Their values agree satisfactorily with experimental data. The temperature dependences of functions S°(T), H°(T) – H°(298.15), and Фхх(T) are calculated.

Temperature effect on thermal-diffusivity and heat-capacity and derived values of thermal-conductivity of reservoir rock materials

A laser flash method (micro-flash apparatus LFA 457) and differential scanning calorimeter (DSC 204 F1) were employed to study of the temperature effect on the thermophysical properties (thermal diffusivity $$a$$, heat capacity $$C_{\text{P}}$$ and thermal conductivity $$\lambda$$) of the natural reservoir rock sample. A relationship between the thermophysical properties behavior and the physical–chemical processes (thermal decomposition of pore heavy oil and volatilization of pore fluids) occurring in the rock’s pore fluids during heating in distinct temperature ranges was established. The measurements of the thermal-diffusivity have been made over the temperature range from 295 to 774 K. The isobaric heat capacities (CP) of the same sample were measured in the temperature range from 308 to 768 K. Uncertainties of the measurements are 3% and 1% for $$a$$ and $$C_{\text{P}}$$, respectively. The significant effect of thermal decomposition on the measured values of heat-capacity of reservoir rock sample at high temperatures (above 680 K) was experimentally found. We experimentally observed temperature anomaly of the heat capacity of rock sample in distinct temperature ranges, around 380 K (low-temperature range) and 680 K (high-temperature range).We attribute these anomalies to the dehydration (evolution of the volatile matter, VM, devolatilization) and aromatization of the carbon (thermal decomposition), which are known to occur under heat treatment. This leads to unusual increasing the heat capacity at high temperatures. Measured values of thermal diffusivity ($$a$$) and heat capacity ($$C_{\text{P}}$$) together with density data ($$\rho = { 2210}\;{\text{kg}}\;{\text{m}}^{ - 3}$$) were used to calculate the derived key properties, thermal conductivities ($$\lambda$$) of the rock sample, using very well-known relation, $$\lambda = a\rho C_{\text{P}}$$.

The effect of lattice disorder on the low-temperature heat capacity of (U1\u2212yThy)O2 and 238Pu-doped UO2

The low-temperature heat capacity of (U1−yThy)O2 and 238Pu-doped UO2 samples were determined using hybrid adiabatic relaxation calorimetry. Results of the investigated systems revealed the presence of the magnetic transition specific for UO2 in all three intermediate compositions of the uranium-thorium dioxide (y = 0.05, 0.09 and 0.12) and in the 238Pu-doped UO2 around 25 K. The magnetic behaviour of UO2 exposed to the high alpha dose from the 238Pu isotope was studied over time and it was found that 1.6% 238Pu affects the magnetic transition substantially, even after short period of time after annealing. In both systems the antiferromagnetic transition changes intensity, shape and Néel temperature with increasing Th-content and radiation dose, respectively, related to the increasing disorder on the crystal lattice resulting from substitution and defect creation.

Heat Capacity and Thermodynamic Functions of DyInGe2O7 and HoInGe2O7 Germanates in the Temperature Range 350–1000 K

The compounds DyInGe2O7 and HoInGe2O7 were synthesized by multistage calcination of stoichiometric mixtures of the constituent oxides (solid-phase synthesis) in air in the temperature range 1273–1473 K. The high-temperature heat capacities of polycrystalline samples of dysprosium–indium and holmium–indium mixed-cation germanates were measured by differential scanning calorimetry. The thermodynamic properties of the investigated oxides were calculated using the Cp = f(T) experimental data.

Preparation and characterization of nano‐enhanced myristic acid using metal oxide nanoparticles for thermal energy storage

Fatty acids have been broadly used as phase change materials (PCMs) for thermal energy storage. However, low thermal conductivity limits their performances. This paper investigates the influence of metal oxide nanoparticle addition on myristic acid (MA) as nano-enhanced PCM (NEPCM). Stability, chemical, and thermal properties were considered. Four types of nanoaprticles, TiO2, CuO, Al2O3, and ZnO, were dispersed in MA at 0.1, 0.5, 1, and 2 wt%. Stability and dispersion were checked by sediment photograph capturing and scanning electron microscopy/energy-dispersive spectroscopy. The Fourier-transformed infrared (FTIR) and X-ray diffraction analysis confirmed no chemical interaction between the nanoparticles and MA. The results revealed a ratio of thermal conductivity of 1.50, 1.49, 1.45, and 1.37, respectively, for 2 wt% of ZnO, Al2O3, CuO, and TiO2. The T-history method confirmed this enhancement. The latent heat thermal energy storage (LHTES) properties of the nano-enhanced MA were evaluated using differential scanning calorimetry. The latent heat capacities of nano-enhanced MA samples have dropped between 9.64 and 5.01 % compared with pure MA, and phase change temperature range was not affected significantly. The NEPCM was subjected to 500 thermal cycling, it showed a good thermal reliability as LHTES properties remained unchanged, while FTIR analysis showed similar characteristics compared with uncycled samples, indicating a good chemical stability. Based on the results regarding with the LHTES properties, cycling thermal reliability, and higher thermal conductivity improvement, it can be achieved that the MA/Al2O3 (2.0 wt%) and MA/ZnO (2.0 wt%) composites could be better PCMs for solar TES applications.

Optimal experiment design for thermal property estimation using a boundary condition of the fourth kind with a time-limited heating period

An optimal design of a three-layer experimental apparatus where a thin heater is placed between two identical samples is proposed. It allows thermal conductivity and volumetric heat capacity of high-conductivity materials to be estimated when the heating period is finite and the heater heat capacity is not negligible. Once the thermal field within the sample is known and the sensitivity coefficients are computed, a D-optimum criterion is applied in order to minimize the area of the confidence region of the estimates. Three experimental variables (experiment duration, heating duration and sensor location) are investigated for different values of the heater heat capacity. For instance, when it is 5% of the sample heat capacity, the optimal experiment duration is of about 4% longer than that occurring when the heater is neglected. However, the heater heat capacity does not affect the optimal heating duration and the optimal sensor locations.

ДОСЛІДЖЕННЯ ТЕПЛОФІЗИЧНИХ ХАРАКТЕРИСТИК ФОРМУВАЛЬНОГО РОЗЧИНУ БІОДЕГРАДАБЕЛЬНОГО ЇСТІВНОГО ПОКРИТТЯ/ПЛІВКИ

Їстівні покриття і плівки – вид біодеградабельної полімерної упаковки, яка не потребує індивідуального збору та особливих умов утилізації. Активне використання біоупаковки дозволить значно скоротити екологічне навантаження на довкілля. Дослідження залежності питомої теплоти випаровування вологи від вмісту вологи у матеріалі їстівного покриття, а також масової теплоємності матеріалу цього покриття від температури, проводили з використанням спеціалізованого калориметричного приладу ДКМИ-01, який розроблено в Інституті технічної теплофізики НАН України. Встановлено, що питома теплота випаровування вологи обох зразків значно перебільшує питому теплоту випаровування води rв = 2430,5 кДж/кг за температури 30 ºС, що підтверджує, що вся волога наявна у зразках є зв’язаною. Відповідно до отриманих експериментальних результатів теплоємність зразка без ПВС має більші значення (3598,89-3830,69 Дж/кг∙К за умови нагрівання зразка від 32,5 до 92,5 оС), що обумовлено властивістю матеріалу. За допомогою термічного аналізу встановлено, що більше механічно-та адсорбційно-зв’язаної вологи містить зразок з ПВС за рахунок водневих зав’язків, які утворюють полімолекулярний шар адсорбційно-зв’язаної вологи. ПВС дозволяє створювати екологічно безпечні матеріали, які мають відмінні показники якості. Встановлена закомірність буде впливати на тривалість висушування їстівного покриття з на поверхні виробів, що вимагатиме використання додаткового обладнання з метою інтенсифікації процесу або додаткових виробничих площ. Встановлено, що найкращою для прогнозування зразка без ПВС є степенева модель ŷ = 2937,76∙х0,054∙х, а за наявності ПВС – ŷ = 3455,23∙е0,001∙х. Отримані математичні моделі дозволяють раціоналізувати технологічні розрахунки у виробничих умовах.

A model for thermal gradient and heat flow in central Chile: The role of thermal properties

The aim of this work is to quantify variations in heat flow and thermal gradient patterns at the latitude of central Chile and to evaluate the role of thermal properties of macro-geological units within the lithosphere. We developed a numerical thermal model for a continental-scale cross section at 33∘S latitude, integrating available and new data on geometry and dynamics of subduction, as well as thermal and mechanical properties for the continental and oceanic lithosphere, and asthenosphere. The model compares heat flow and thermal gradient curves against homogeneous inputs for radiogenic heat production (RHP) and thermal conductivity. The results of this model were calibrated with results of thermal gradient measurements at different morpho-tectonic domains. The results show that both, cold slab subduction and mantle wedge advection, play major roles in the regional thermal structure. Variations with respect to regional tendency are due to changes in thermal properties. The fore-arc has an average thermal gradient from 12 to 16∘C/km, whereas in the High Andes Cordillera it reaches up to values in the range between 20 and 28∘C/km. Model results indicate that thermal gradient increases eastward up to ∼25∘C/km in the easternmost foreland, which is a stable domain. The consistency of the model with respect to seismic record is discussed. Variation in composition and thermal properties is common at subduction zones due to dynamic petrologic processes. The RHP of the exposed upper crust units was obtained from more than 1000 in-situ measurements, whereas thermal conductivity, specific heat capacity and density of samples were obtained in the laboratory. The calculated RHP of upper crust is ∼2.0 μW/m3, which is responsible for ∼15–40% of the heat flow that reaches the surface.

High-Temperature Heat Capacity of Y0.65Pr0.35BiGeO5 and Y0.65Nd0.35BiGeO5 in the Range 350–1000 K

Oxides Y0.65Pr0.35BiGeO5 and Y0.65Nd0.35BiGeO5 have been synthesized by a ceramic method. The heat capacity of fine crystalline samples has been studied in the range 350–1000 K by differential scanning calorimetry. The Cp = f(T) dependences can be described by the Maier–Kelley equation. The thermodynamic functions of these oxides—changes in enthalpy, entropy, and reduced Gibbs energy—have been calculated from the experimental data on high-temperature heat capacity.

High-Temperature Heat Capacity of Y0,65Pr0,35BiGeO5 and Y0,65Nd0,35BiGeO5 in the Range 350–1000 K

Oxides Y0.65Pr0.35BiGeO5 and Y0.65Nd0.35BiGeO5 have been synthesized by a ceramic method. The heat capacity of fine crystalline samples has been studied in the range 350–1000 K by differential scanning calorimetry. The Cp = f(T) dependences can be described by the Maier–Kelley equation. The thermodynamic functions of these oxides—changes in enthalpy, entropy, and reduced Gibbs energy—have been calculated from the experimental data on high-temperature heat capacity.

Experimental study on thermophysical properties of molten salt nanofluids prepared by high-temperature melting

Heat storage is a key technology in solar thermal power, helps solar thermal power eliminate the instability in energy supply for the grid, and provides continuous and stable high-quality electrical energy to improve power system efficiency and extend system life. Molten salt is an important material for heat storage and heat transfer in solar thermal power. In recent years, nanofluid technology has been applied to investigate heat storage and transfer materials, such as molten salt, to improve heat capacity. However, the nanofluid technology is hampered by the easy agglomeration of nanoparticles in molten salts, and this phenomenon degrades the performance of the molten salt nanofluids. To reduce or prevent agglomeration, a two-step method with high-temperature melting in preparing molten salt nanofluids is developed recently. Molten salt nanofluids obtained by high-temperature melting show good stability and long time to agglomerate. This paper presented the study on the thermophysical properties of molten salt nanofluids prepared by high-temperature melting method. The molten salt nanofluids possessed low-melting point salt as base liquid and SiO2 with a diameter of 20 nm as nanoparticles. The specific heat of this type of molten salt nanofluid was tested, and the optimum concentration of nanoparticles was determined. Results showed that the specific heat capacities of the molten salt nanofluid samples with different mass fractions of nanoparticles were higher than those of pure molten salt. The average specific heat of molten salt nanofluid with a mass fraction of 0.5% was the highest at 1.950 J/(g K), which was 24.5% more than that of pure molten salt. The thermophysical properties of molten salt nanofluids with a mass fraction of 0.5% and prepared by high-temperature melting were experimentally tested and compared with those of pure molten salt. These properties included melting point, primary crystallization point, thermal conductivity, viscosity, latent heat, and density. The molten salt nanofluids showed good performance for heat storage and transfer.

Measurements and analysis of the thermal properties of a sedimentary succession in Yangtze plate in China

A geological stratum is a rock or soil layer that has internally consistent characteristics and is distinguishable from adjacent layers. A stratigraphic section contains reference information for the strata of an associated sedimentary area. In this paper, the thermal properties of 36 rock formations in a succession of the Yangtze plate in China are studied. Thermal properties are analyzed with an emphasis on rock formations, rock lithological types and dry/saturated conditions. The results show that thermal conductivity varies dramatically with different rock lithological types, which range from 0.72 W m−1 K−1 to 4.49 W m−1 K−1. The analysis of biochemical sedimentary rocks shows that silicate has the highest thermal conductivity, followed by dolomite and limestone; this variation is due to the differences in rock-forming minerals. The thermal conductivity of the clastic rocks is mainly determined by the type of minerals, the porosity and the water content. Compared to dry samples, the thermal conductivity and volumetric heat capacity of saturated samples are higher. Moreover, the thermal conductivity data of nine other locations in the Yangtze plate are compared with the stratigraphic data. This analysis shows that thermal conductivity matches very well for most of the geological formations, with the exception of sandstone, which exhibits a significant deviation across formations. Finally, the thermal properties for the Yangtze plate are mapped for insight on their spatial distribution.