Enthalpy of mixing of Sn-Cd system using high temperature Calvet microcalorimeter

International Nuclear Information System (INIS)

Jayanthi, K.; Iyer, V.S.; Venugopal, V.

1993-01-01

The integral enthalpy of mixing of Sn + Cd alloys were determined at 690 K for mole fraction of cadmium (X Cd ) from 0.06 to 0.958. In the present study, the use of small quantities of metals and the determination of enthalpy of mixing of an endothermic reaction without stirring the bath solution. This was possible due to the high sensitivity of the Calvet calorimeter. (author). 3 refs., 3 tabs

Enthalpy analysis and Heat Exchanger Sizing of an Air-cooled Proton Exchange Membrane Fuel Cell System

DEFF Research Database (Denmark)

Gao, Xin; Berning, Torsten; Kær, Søren Knudsen

below -20 °C in the winter which make liquid-cooled fuel cells impossible. In such cases, air-cooled fuel cell systems are deployed where the air that is fed to the fuel cell serves both as reactant supplier and coolant to remove the waste heat that is generated during fuel cell operation. In some cases...... in order to optimize the operating conditions and the performance of such a system. The adjustable parameters include the fan speed that determines the amount of air that is brought into the system, and the size and rotating speed of the rotating enthalpy wheel. In addition, computational fluid dynamics...... or an ordinary heat exchanger can fulfill the heat recovery demand. Despite the fact that the air enters the stack at a cold temperature, even the forefront of the stack is at a much elevated and desired stack temperature with the help of supplying an acceptable amount of power to an electric stack heater. So...

Numerical Investigation of Double-Cone Flows with High Enthalpy Effects

Science.gov (United States)

Nompelis, I.; Candler, G. V.

2009-01-01

A numerical study of shock/shock and shock/boundary layer interactions generated by a double-cone model that is placed in a hypersonic free-stream is presented. Computational results are compared with the experimental measurements made at the CUBRC LENS facility for nitrogen flows at high enthalpy conditions. The CFD predictions agree well with surface pressure and heat-flux measurements for all but one of the double-cone cases that have been studied by the authors. Unsteadiness is observed in computations of one of the LENS cases, however for this case the experimental measurements show that the flowfield is steady. To understand this discrepancy, several double-cone experiments performed in two different facilities with both air and nitrogen as the working gas are examined in the present study. Computational results agree well with measurements made in both the AEDC tunnel 9 and the CUBRC LENS facility for double-cone flows at low free-stream Reynolds numbers where the flow is steady. It is shown that at higher free- stream pressures the double-cone simulations develop instabilities that result in an unsteady separation.

Enthalpy-based equation of state for highly porous materials employing modified soft sphere fluid model

Science.gov (United States)

Nayak, Bishnupriya; Menon, S. V. G.

2018-01-01

Enthalpy-based equation of state based on a modified soft sphere model for the fluid phase, which includes vaporization and ionization effects, is formulated for highly porous materials. Earlier developments and applications of enthalpy-based approach had not accounted for the fact that shocked states of materials with high porosity (e.g., porosity more than two for Cu) are in the expanded fluid region. We supplement the well known soft sphere model with a generalized Lennard-Jones formula for the zero temperature isotherm, with parameters determined from cohesive energy, specific volume and bulk modulus of the solid at normal condition. Specific heats at constant pressure, ionic and electronic enthalpy parameters and thermal excitation effects are calculated using the modified approach and used in the enthalpy-based equation of state. We also incorporate energy loss from the shock due to expansion of shocked material in calculating porous Hugoniot. Results obtained for Cu, even up to initial porosities ten, show good agreement with experimental data.

Comparison of Themodynamic and Transport Property Models for Computing Equilibrium High Enthalpy Flows

Science.gov (United States)

Ramasahayam, Veda Krishna Vyas; Diwakar, Anant; Bodi, Kowsik

2017-11-01

To study the flow of high temperature air in vibrational and chemical equilibrium, accurate models for thermodynamic state and transport phenomena are required. In the present work, the performance of a state equation model and two mixing rules for determining equilibrium air thermodynamic and transport properties are compared with that of curve fits. The thermodynamic state model considers 11 species which computes flow chemistry by an iterative process and the mixing rules considered for viscosity are Wilke and Armaly-Sutton. The curve fits of Srinivasan, which are based on Grabau type transition functions, are chosen for comparison. A two-dimensional Navier-Stokes solver is developed to simulate high enthalpy flows with numerical fluxes computed by AUSM+-up. The accuracy of state equation model and curve fits for thermodynamic properties is determined using hypersonic inviscid flow over a circular cylinder. The performance of mixing rules and curve fits for viscosity are compared using hypersonic laminar boundary layer prediction on a flat plate. It is observed that steady state solutions from state equation model and curve fits match with each other. Though curve fits are significantly faster the state equation model is more general and can be adapted to any flow composition.

Pneumatic Performance Study of a High Pressure Ejection Device Based on Real Specific Energy and Specific Enthalpy

Directory of Open Access Journals (Sweden)

Jie Ren

2014-09-01

Full Text Available In high-pressure dynamic thermodynamic processes, the pressure is much higher than the air critical pressure, and the temperature can deviate significantly from the Boyle temperature. In such situations, the thermo-physical properties and pneumatic performance can’t be described accurately by the ideal gas law. This paper proposes an approach to evaluate the pneumatic performance of a high-pressure air catapult launch system, in which esidual functions are used to compensate the thermal physical property uncertainties of caused by real gas effects. Compared with the Nelson-Obert generalized compressibility charts, the precision of the improved virial equation of state is better than Soave-Redlich-Kwong (S-R-K and Peng-Robinson (P-R equations for high pressure air. In this paper, the improved virial equation of state is further used to establish a compressibility factor database which is applied to evaluate real gas effects. The specific residual thermodynamic energy and specific residual enthalpy of the high-pressure air are also derived using the modified corresponding state equation and improved virial equation of state which are truncated to the third virial coefficient. The pneumatic equations are established on the basis of the derived residual functions. The comparison of the numerical results shows that the real gas effects are strong, and the pneumatic performance analysis indicates that the real dynamic thermodynamic process is obviously different from the ideal one.

Ionic liquids. Combination of combustion calorimetry with high-level quantum chemical calculations for deriving vaporization enthalpies.

Science.gov (United States)

Emel'yanenko, Vladimir N; Verevkin, Sergey P; Heintz, Andreas; Schick, Christoph

2008-07-10

In this work, the molar enthalpies of formation of the ionic liquids [C2MIM][NO3] and [C4MIM][NO3] were measured by means of combustion calorimetry. The molar enthalpy of fusion of [C2MIM][NO3] was measured using differential scanning calorimetry. Ab initio calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic species using the G3MP2 theory. We have used a combination of traditional combustion calorimetry with modern high-level ab initio calculations in order to obtain the molar enthalpies of vaporization of a series of the ionic liquids under study.

Extremes temperatures and enthalpy in Finland and Sweden in a changing climate

International Nuclear Information System (INIS)

Venaelaeinen, A.; Saku, S.; Jylhae, K.; Nikulin, G.; Kjellstroem, E.; Baerring, L.

2009-06-01

Though risks caused by harsh weather conditions are taken into account in the planning of nuclear power plants, some exceptional weather events or combination of different events may prevent normal power operation and simultaneously endanger safe shutdown of the plant. Extreme weather events could influence, for example, the external power grid connection, emergency diesel generators (blockage of air intakes), ventilation and cooling of electric and electronics equipment rooms and the seawater intake. Due to the influence of an intensified greenhouse effect the climate is changing rapidly during the coming decades and this change is expected to have an influence also on the occurrence of extreme weather events. In this report we have examined extreme temperatures. Enthalpy is a parameter that combines air temperature and air humidity and it is used in the design of air conditioning systems. Therefore, we have included also return levels of enthalpy in our analysis. The influence of climate change on extreme temperatures is analysed based on regional climate model simulations. The reoccurrence times of high temperatures combined with high air humidity was analysed based on measurements made at five Finnish and three Swedish meteorological stations. Based on the observational records we find the 10 year return level of daily maximum temperature to be around 32 deg. C and the 100 year return level around 35 deg. C. If we look the return levels of warm and humid conditions then for example in Helsinki the 10 year return level of one week mean temperature in case mean air humidity is above 80% is 20.1 deg. C. The 10 year return level of daily maximum enthalpy is around 60 kJ/kg and the 100 year return level almost 70 kJ/kg. According to the climate model simulations the largest increase of 50-year return level of daily maximum temperature is found in southern Sweden and south-western Finland. By the end of this century the increase can be 3-5 deg. C. The largest change

Extremes temperatures and enthalpy in Finland and Sweden in a changing climate

Energy Technology Data Exchange (ETDEWEB)

Venaelaeinen, A.; Saku, S.; Jylhae, K. (Finnish Meteorological Institute (Finland)); Nikulin, G.; Kjellstroem, E.; Baerring, L. (Swedish Meteorological Institute (Sweden))

2009-06-15

Though risks caused by harsh weather conditions are taken into account in the planning of nuclear power plants, some exceptional weather events or combination of different events may prevent normal power operation and simultaneously endanger safe shutdown of the plant. Extreme weather events could influence, for example, the external power grid connection, emergency diesel generators (blockage of air intakes), ventilation and cooling of electric and electronics equipment rooms and the seawater intake. Due to the influence of an intensified greenhouse effect the climate is changing rapidly during the coming decades and this change is expected to have an influence also on the occurrence of extreme weather events. In this report we have examined extreme temperatures. Enthalpy is a parameter that combines air temperature and air humidity and it is used in the design of air conditioning systems. Therefore, we have included also return levels of enthalpy in our analysis. The influence of climate change on extreme temperatures is analysed based on regional climate model simulations. The reoccurrence times of high temperatures combined with high air humidity was analysed based on measurements made at five Finnish and three Swedish meteorological stations. Based on the observational records we find the 10 year return level of daily maximum temperature to be around 32 deg. C and the 100 year return level around 35 deg. C. If we look the return levels of warm and humid conditions then for example in Helsinki the 10 year return level of one week mean temperature in case mean air humidity is above 80% is 20.1 deg. C. The 10 year return level of daily maximum enthalpy is around 60 kJ/kg and the 100 year return level almost 70 kJ/kg. According to the climate model simulations the largest increase of 50-year return level of daily maximum temperature is found in southern Sweden and south-western Finland. By the end of this century the increase can be 3-5 deg. C. The largest change

Enthalpies of sublimation of fullerenes by thermogravimetry

Energy Technology Data Exchange (ETDEWEB)

Martínez-Herrera, Melchor; Campos, Myriam; Torres, Luis Alfonso; Rojas, Aarón, E-mail: arojas@cinvestav.mx

2015-12-20

Graphical abstract: - Highlights: • Enthalpies of sublimation of fullerenes were measured by thermogravimetry. • Results of enthalpies of sublimation are comparable with data reported in literature. • Not previously reported enthalpy of sublimation of C{sub 78} is supplied in this work. • Enthalpies of sublimation show a strong dependence with the number of carbon atoms in the cluster. • Enthalpies of sublimation are congruent with dispersion forces ruling cohesion of solid fullerene. - Abstract: The enthalpies of sublimation of fullerenes, as measured in the interval of 810–1170 K by thermogravimetry and applying the Langmuir equation, are reported. The detailed experimental procedure and its application to fullerenes C{sub 60}, C{sub 70}, C{sub 76}, C{sub 78} and C{sub 84} are supplied. The accuracy and uncertainty associated with the experimental results of the enthalpy of sublimation of these fullerenes show that the reliability of the measurements is comparable to that of other indirect high-temperature methods. The results also indicate that the enthalpy of sublimation increases proportionally to the number of carbon atoms in the cluster but there is also a strong correlation between the enthalpy of sublimation and the polarizability of each fullerene.

Free-flight measurement technique in the free-piston high-enthalpy shock tunnel

Science.gov (United States)

Tanno, H.; Komuro, T.; Sato, K.; Fujita, K.; Laurence, S. J.

2014-04-01

A novel multi-component force-measurement technique has been developed and implemented at the impulse facility JAXA-HIEST, in which the test model is completely unrestrained during the test and thus experiences free-flight conditions for a period on the order of milliseconds. Advantages over conventional free-flight techniques include the complete absence of aerodynamic interference from a model support system and less variation in model position and attitude during the test itself. A miniature on-board data recorder, which was a key technology for this technique, was also developed in order to acquire and store the measured data. The technique was demonstrated in a HIEST wind-tunnel test campaign in which three-component aerodynamic force measurement was performed on a blunted cone of length 316 mm, total mass 19.75 kg, and moment of inertia 0.152 kgm2. During the test campaign, axial force, normal forces, and pitching moment coefficients were obtained at angles of attack from 14° to 32° under two conditions: H0 = 4 MJ/kg, P0 = 14 MPa; and H0 = 16 MJ/kg, P0 = 16 MPa. For the first, low-enthalpy condition, the test flow was considered a perfect gas; measurements were thus directly compared with those obtained in a conventional blow-down wind tunnel (JAXA-HWT2) to evaluate the accuracy of the technique. The second test condition was a high-enthalpy condition in which 85% of the oxygen molecules were expected to be dissociated; high-temperature real-gas effects were therefore evaluated by comparison with results obtained in perfect-gas conditions. The precision of the present measurements was evaluated through an uncertainty analysis, which showed the aerodynamic coefficients in the HIEST low enthalpy test agreeing well with those of JAXA-HWT2. The pitching-moment coefficient, however, showed significant differences between low- and high-enthalpy tests. These differences are thought to result from high-temperature real-gas effects.

High-energy air shock study in steel and grout pipes

International Nuclear Information System (INIS)

Glenn, H.D.; Kratz, H.R.; Keough, D.D.; Duganne, D.A.; Ruffner, D.J.; Swift, R.P.; Baum, D.

1979-01-01

Voitenko compressors are used to generate 43 mm/μs air shocks in both a steel and a grout outlet pipe containing ambient atmospheric air. Fiber-optic ports provide diaphragm burst times, time-of-arrival (TOA) data, and velocities for the shock front along the 20-mm-ID exit pipes. Pressure profiles are obtained at higher enthalpy shock propagation than ever before and at many locations along the exit pipes. Numerous other electronic sensors and postshot observations are described, as well as experimental results. The primary objectives of the experiments are as follows: (1) provide a data base for normalization/improvement of existing finite-difference codes that describe high-energy air shocks and gas propagation; (2) obtain quantitative results on the relative attenuation effects of two very different wall materials for high-energy air shocks and gas flows. The extensive experimental results satisfy both objectives

Enthalpy-increment measurements for CsI(s) and Cs2CrO4(s) by high-temperature Calvet calorimetry

International Nuclear Information System (INIS)

Venugopal, V.; Agarwal, R.; Roy, K.N.; Prasad, R.; Sood, D.D.

1987-01-01

Molar thermodynamic properties of CsI(s) and Cs 2 Cr O 4 (s) have been evaluated by enthalpy-increment measurements, using a Calvet high-temperature calorimeter. Least squares analyses were performed on the enthalpy increment results. Data is presented in tabular form for the dependence of enthalpy increments on temperature, in the range 333 to 822 K, for both caesium compounds, along with the thermal properties of the compounds. Good agreement is found between the present data and previously reported results on reduced enthalpy increments of CsI(s) and Cs 2 CrO 4 (s). (U.K.)

Short Pulsed Laser Methods for Velocimetry and Thermometry in High Enthalpy Facilities, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — A suite of laser-based diagnostics is proposed to measure velocity and temperature simultaneously using unseeded techniques in high enthalpy flows relevant to...

Formation enthalpy of alkali-borosilicate glass

International Nuclear Information System (INIS)

Borisova, N.V.; Ushakov, V.M.

1991-01-01

Temperature dependence of formation enthalpy of glass of the composition 0.0438Na 2 O-0.0385K 2 O-0.3394B 2 O 3 -0.5783SiO 2 was determined using the method of high-temperature colorimetry-dissolution, mixing and differential scanning calorimetry. The glass considered has liquation nature-two-vitrification ranges at 713 K and 817 K are detected. The brightening point is 922 K. The calculation of formation enthalpy using the method of partial heat capacities is made in the temperature range of 973-1473 K. Formation enthalpy does not depend on temperature in the temperature range of 298-1273 K

Investigating ultra high-enthalpy geothermal systems: a collaborative initiative to promote scientific opportunities

Science.gov (United States)

Elders, W. A.; Nielson, D.; Schiffman, P.; Schriener, A., Jr.

2014-12-01

Scientists, engineers, and policy makers gathered at a workshop in the San Bernardino Mountains of southern California in October 2013 to discuss the science and technology involved in developing high-enthalpy geothermal fields. A typical high-enthalpy geothermal well between 2000 and 3000 m deep produces a mixture of hot water and steam at 200-300 °C that can be used to generate about 5-10 MWe of electric power. The theme of the workshop was to explore the feasibility and economic potential of increasing the power output of geothermal wells by an order of magnitude by drilling deeper to reach much higher pressures and temperatures. Development of higher enthalpy geothermal systems for power production has obvious advantages; specifically higher temperatures yield higher power outputs per well so that fewer wells are needed, leading to smaller environmental footprints for a given size of power plant. Plans for resource assessment and drilling in such higher enthalpy areas are already underway in Iceland, New Zealand, and Japan. There is considerable potential for similar developments in other countries that already have a large production of electricity from geothermal steam, such as Mexico, the Philippines, Indonesia, Italy, and the USA. However drilling deeper involves technical and economic challenges. One approach to mitigating the cost issue is to form a consortium of industry, government and academia to share the costs and broaden the scope of investigation. An excellent example of such collaboration is the Iceland Deep Drilling Project (IDDP), which is investigating the economic feasibility of producing electricity from supercritical geothermal reservoirs, and this approach could serve as model for future developments elsewhere. A planning committee was formed to explore creating a similar initiative in the USA.

Enthalpy generation from mixing in hohlraum-driven targets

Science.gov (United States)

Amendt, Peter; Milovich, Jose

2016-10-01

The increase in enthalpy from the physical mixing of two initially separated materials is analytically estimated and applied to ICF implosions and gas-filled hohlraums. Pressure and temperature gradients across a classical interface are shown to be the origin of enthalpy generation from mixing. The amount of enthalpy generation is estimated to be on the order of 100 Joules for a 10 micron-scale annular mixing layer between the solid deuterium-tritium fuel and the undoped high-density carbon ablator of a NIF-scale implosion. A potential resonance is found between the mixing layer thickness and gravitational (Cs2/ g) and temperature-gradient scale lengths, leading to elevated enthalpy generation. These results suggest that if mixing occurs in current capsule designs for the National Ignition Facility, the ignition margin may be appreciably eroded by the associated enthalpy of mixing. The degree of enthalpy generation from mixing of high- Z hohlraum wall material and low- Z gas fills is estimated to be on the order of 100 kJ or more for recent NIF-scale hohlraum experiments, which is consistent with the inferred missing energy based on observed delays in capsule implosion times. Work performed under the auspices of Lawrence Livermore National Security, LLC (LLNS) under Contract No. DE-AC52-07NA27344.

A moderate enthalpy and a low pollution load in healthy buildings

DEFF Research Database (Denmark)

Fanger, Povl Ole

1998-01-01

For the design of healthy buildings with a comfortable indoor environment, some general recommendations are provided. New research highlights the importance of controlling the enthalpy of indoor air at a moderate level, i.e., by controlling air temperature and relative humidity at a rather low...... level, still compatible with thermal comfort. A decrement of air temperature or humidity improves the perceived air quality and may decrease the required ventilation rate. A moderate air temperature and humidity plus individual control by radiation and conduction is recommended in order to decrease...

Standard molar enthalpy of formation of methoxyacetophenone isomers

International Nuclear Information System (INIS)

Amaral, Luísa M.P.F.; Morais, Victor M.F.; Ribeiro da Silva, Manuel A.V.

2014-01-01

Highlights: • Experimental and computational energetic study of methoxyacetophenone isomers. • Enthalpies of formation and phase transition determined by calorimetric techniques. • Quantum chemical calculations allowed estimation of enthalpies of formation. • Structure and energy correlations were established. - Abstract: Values of the standard (p o = 0.1 MPa) molar enthalpy of formation of 2′-, 3′- and 4′-methoxyacetophenones were derived from their standard molar energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpies of sublimation/vaporization of the compounds studied. The standard molar enthalpies of formation of the three compounds, in the gaseous phase, at T = 298.15 K, have been derived from the corresponding standard molar enthalpies of formation in the condensed phase and the standard molar enthalpies for the phase transition. The results obtained are −(232.0 ± 2.5), −(237.7 ± 2.7) and −(241.1 ± 2.1) kJ · mol −1 for 2′-, 3′- and 4′-methoxyacetophenone, respectively. Standard molar enthalpies of formation were also estimated from different methodologies: the Cox scheme as well as two different computational approaches using density functional theory-based B3LYP and the multilevel G3 methodologies

Additive scheme for calculation of solvation enthalpies of heterocyclic aromatic compounds. Sublimation/vaporization enthalpy at 298.15 K

International Nuclear Information System (INIS)

Solomonov, Boris N.; Nagrimanov, Ruslan N.; Mukhametzyanov, Timur A.

2016-01-01

Highlights: • Additivity scheme for solvation enthalpies estimation of heteroaromatic compounds was proposed. • Method for determination of vaporization/sublimation enthalpies directly at 298.15 K was developed. • Solution enthalpies of 25 heteroaromatic compounds were measured. • Vaporization/sublimation enthalpies of 44 heteroaromatic compounds were determined. • Obtained values are in good agreement with the results of conventional methods. - Abstract: Hereby we propose a method for determination of vaporization and sublimation enthalpies of heterocyclic and carbonyl-containing aromatic compounds at 298.15 K. According to this method vaporization and sublimation enthalpies at 298.15 K are determined based on enthalpies of solvation and solution. Solvation enthalpies of heteroatomatic and carbonyl-containing compounds are calculated using an additive scheme from the solvation enthalpy of closest aromatic hydrocarbon and contributions related to the exchange of CH-groups of hydrocarbon with corresponding substituent atoms or groups. Measured solution enthalpies together with calculated solvation enthalpies allowed to calculate corresponding vaporization and sublimation enthalpies at 298.15 K for a large number of heterocyclic and carbonyl-containing compounds. We have also found that in a number of cases instead of solution enthalpy in benzene at 298.15 K fusion enthalpy at the melting temperature can be used. Comparison between literature data and calculated vaporization and sublimation enthalpies demonstrates satisfactory performance of the proposed method.

Additive scheme for calculation of solvation enthalpies of heterocyclic aromatic compounds. Sublimation/vaporization enthalpy at 298.15 K

Energy Technology Data Exchange (ETDEWEB)

Solomonov, Boris N., E-mail: boris.solomonov@kpfu.ru; Nagrimanov, Ruslan N.; Mukhametzyanov, Timur A.

2016-06-10

Highlights: • Additivity scheme for solvation enthalpies estimation of heteroaromatic compounds was proposed. • Method for determination of vaporization/sublimation enthalpies directly at 298.15 K was developed. • Solution enthalpies of 25 heteroaromatic compounds were measured. • Vaporization/sublimation enthalpies of 44 heteroaromatic compounds were determined. • Obtained values are in good agreement with the results of conventional methods. - Abstract: Hereby we propose a method for determination of vaporization and sublimation enthalpies of heterocyclic and carbonyl-containing aromatic compounds at 298.15 K. According to this method vaporization and sublimation enthalpies at 298.15 K are determined based on enthalpies of solvation and solution. Solvation enthalpies of heteroatomatic and carbonyl-containing compounds are calculated using an additive scheme from the solvation enthalpy of closest aromatic hydrocarbon and contributions related to the exchange of CH-groups of hydrocarbon with corresponding substituent atoms or groups. Measured solution enthalpies together with calculated solvation enthalpies allowed to calculate corresponding vaporization and sublimation enthalpies at 298.15 K for a large number of heterocyclic and carbonyl-containing compounds. We have also found that in a number of cases instead of solution enthalpy in benzene at 298.15 K fusion enthalpy at the melting temperature can be used. Comparison between literature data and calculated vaporization and sublimation enthalpies demonstrates satisfactory performance of the proposed method.

Field tests for the comparative evaluation of heat and enthalpy exchangers in compact ventilation units; Feldvergleich von Waerme- und Enthalpieuebertragern in Kompakt-Lueftungsgeraeten - Schlussbericht

Energy Technology Data Exchange (ETDEWEB)

Frei, B.

2007-07-01

In an efficiency review on low energy buildings promoted by the Swiss Federal Office of Energy, low air humidity has been measured during thousands of annual hours. Modern compact ventilation units are being increasingly offered with transmission of heat and moisture. One possibility to raise the air humidity level is an enthalpy exchanger with steam-permeable membranes. With an enthalpy exchanger you can not only recover heat but also a good part of the humidity of the return air. In a comparative field study alternate applications with enthalpy or heat exchangers have been analysed at four different locations. Also calculations have been made to estimate how a rotating heat exchanger with ion-exchange resin would have performed. The comparative field study has shown that the enthalpy exchanger is able to raise the humidity level. Conditions for this are internal humidity loads, balanced air volume rates which correspond to occupancy as well as low leakages of the ventilation unit. Over-moistening due to the system with enthalpy exchanger was not found. The measurements have been affected by a sequence of winter months which have been partially warmer than usual. Otherwise the difference between enthalpy and heat exchangers would have been more significant. (author)

Enthalpies of Formation of Hydrazine and Its Derivatives.

Science.gov (United States)

Dorofeeva, Olga V; Ryzhova, Oxana N; Suchkova, Taisiya A

2017-07-20

Enthalpies of formation, Δ f H 298 ° , in both the gas and condensed phase, and enthalpies of sublimation or vaporization have been estimated for hydrazine, NH 2 NH 2 , and its 36 various derivatives using quantum chemical calculations. The composite G4 method has been used along with isodesmic reaction schemes to derive a set of self-consistent high-accuracy gas-phase enthalpies of formation. To estimate the enthalpies of sublimation and vaporization with reasonable accuracy (5-20 kJ/mol), the method of molecular electrostatic potential (MEP) has been used. The value of Δ f H 298 ° (NH 2 NH 2 ,g) = 97.0 ± 3.0 kJ/mol was determined from 75 isogyric reactions involving about 50 reference species; for most of these species, the accurate Δ f H 298 ° (g) values are available in Active Thermochemical Tables (ATcT). The calculated value is in excellent agreement with the reported results of the most accurate models based on coupled cluster theory (97.3 kJ/mol, the average of six calculations). Thus, the difference between the values predicted by high-level theoretical calculations and the experimental value of Δ f H 298 ° (NH 2 NH 2 ,g) = 95.55 ± 0.19 kJ/mol recommended in the ATcT and other comprehensive reference sources is sufficiently large and requires further investigation. Different hydrazine derivatives have been also considered in this work. For some of them, both the enthalpy of formation in the condensed phase and the enthalpy of sublimation or vaporization are available; for other compounds, experimental data for only one of these properties exist. Evidence of accuracy of experimental data for the first group of compounds was provided by the agreement with theoretical Δ f H 298 ° (g) value. The unknown property for the second group of compounds was predicted using the MEP model. This paper presents a systematic comparison of experimentally determined enthalpies of formation and enthalpies of sublimation or vaporization with the results of

Determination of the vacancy formation enthalpy for high purity Ni

International Nuclear Information System (INIS)

Lynn, K.G.; Snead, C.L. Jr.; Hurst, J.J.; Farrell, K.

1979-01-01

Positron-annihilation lifetime measurements have been made on Ni over a temperature range of 4.2 to 1700 K. We find a small change in the lifetime from 4.2 to 900 K indicating a very small thermal-expansion effect. A small precursor effect is observed before the onset of significant vacancy trapping. A monovacancy formation enthalpy of 1.54/sub +0.2//sup -0.1/ eV is extracted without taking divacancies into consideration in the analysis. No detrapping from mono-vacancies is observed even at the higher temperatures. The vacancy formation enthalpy extracted from the lifetime data is compared to values obtained by Doppler-broadening and angular-correlation techniques

Determination of the vacancy formation enthalpy for high purity Ni

International Nuclear Information System (INIS)

Lynn, K.G.; Snead, C.L. Jr.; Hurst, J.J.; Farrell, K.

1979-01-01

Positron-annihilation lifetime measurements have been made on Ni over a temperature range of 4.2 to 1700 K. We find a small change in the lifetime from 4.2 - 900 K indicating a very small thermal-expansion effect. A small precursor effect is observed before the onset of significant vacancy trapping. A monovacancy formation enthalpy of 1.54sub(+0.2)sup(-0.1) eV is extracted without taking divacancies into consideration in the analysis. No detrapping from mono-vacancies is observed even at the higher temperatures. The vacancy formation enthalpy extracted from the lifetime data is compared to values obtained by Doppler-broadening and angular-correlation techniques. (author)

Enthalpy of sublimation as measured using a silicon oscillator

Science.gov (United States)

Shakeel, Hamza; Pomeroy, J. M.

In this study, we report the enthalpy of sublimation of common gases (nitrogen, oxygen, argon, carbon dioxide, neon, krypton, xenon, and water vapor) using a large area silicon oscillator with a sub-ng (~0.027 ng/cm2) mass sensitivity. The double paddle oscillator design enables high frequency stability (17 ppb) at cryogenic temperatures and provides a consistent technique for enthalpy measurements. The enthalpies of sublimation are derived from the rate of mass loss during programmed thermal desorption and are detected as a change in the resonance frequency of the self-tracking oscillator. These measured enthalpy values show excellent agreement with the accepted literature values.

Determination of vapor pressures, enthalpies of sublimation, and enthalpies of fusion of benzenetriols

International Nuclear Information System (INIS)

Verevkin, Sergey P.; Schick, Christoph

2004-01-01

Molar enthalpies of sublimation of 1,2,4-, 1,2,3-, and 1,3,5-tri-hydroxy-benzene, were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The molar enthalpies of fusion and molar heat capacities of these compounds were measured by DSC. The measured data sets of vaporization, sublimation and fusion enthalpies were checked for internal consistency. Strength of the inter- and intra-molecular hydrogen bonding in di- and tri-hydroxy-benzenes have been assessed

Enthalpy-entropy compensation in protein unfolding

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

Enthalpy-entropy compensation was found to be a universal law in protein unfolding based on over 3 000 experimental data. Water molecular reorganization accompanying the protein unfolding was suggested as the origin of the enthalpy-entropy compensation in protein unfolding. It is indicated that the enthalpy-entropy compensation constitutes the physical foundation that satisfies the biological need of the small free energy changes in protein unfolding, without the sacrifice of the bio-diversity of proteins. The enthalpy-entropy compensation theory proposed herein also provides valuable insights into the Privalov's puzzle of enthalpy and entropy convergence in protein unfolding.

The enthalpy of sublimation of cubane

International Nuclear Information System (INIS)

Bashir-Hashemi, A.; Chickos, James S.; Hanshaw, William; Zhao Hui; Farivar, Behzad S.; Liebman, Joel F.

2004-01-01

The sublimation enthalpy of cubane, a key reference material for force field and quantum mechanical computations, was measured by combining the vaporization enthalpy at T = 298.15 K to the sum of the fusion enthalpy measured at T = 405 K and a solid-solid phase transition that occurs at T 394 K. The fusion and solid-solid phase transitions were measured previously. A sublimation enthalpy value of (55.2 ± 2.0) kJ mol -1 at T = 298.15 K was obtained. This value compares quite favorably the value obtained by comparing the sublimation enthalpy of similar substances as a function of their molar masses but is at odds with earlier measurements

The enthalpy of sublimation of cubane

Energy Technology Data Exchange (ETDEWEB)

Bashir-Hashemi, A.; Chickos, James S.; Hanshaw, William; Zhao Hui; Farivar, Behzad S.; Liebman, Joel F

2004-12-15

The sublimation enthalpy of cubane, a key reference material for force field and quantum mechanical computations, was measured by combining the vaporization enthalpy at T = 298.15 K to the sum of the fusion enthalpy measured at T = 405 K and a solid-solid phase transition that occurs at T 394 K. The fusion and solid-solid phase transitions were measured previously. A sublimation enthalpy value of (55.2 {+-} 2.0) kJ mol{sup -1} at T = 298.15 K was obtained. This value compares quite favorably the value obtained by comparing the sublimation enthalpy of similar substances as a function of their molar masses but is at odds with earlier measurements.

Enthalpy of formation of anisole: implications for the controversy on the O-H bond dissociation enthalpy in phenol.

Science.gov (United States)

Simões, Ricardo G; Agapito, Filipe; Diogo, Hermínio P; da Piedade, Manuel E Minas

2014-11-20

Significant discrepancies in the literature data for the enthalpy of formation of gaseous anisole, ΔfHmo(PhOCH3, g), have fueled an ongoing controversy regarding the most reliable enthalpy of formation of the phenoxy radical and of the gas phase O-H bond dissociation enthalpy, DHo(PhO-H), in phenol. In the present work ΔfHmo(PhOCH3, g) was reassessed using a combination of calorimetric determinations and high-level (W2-F12) ab initio calculations. Static-bomb combustion calorimetry led to the standard molar enthalpy of formation of liquid anisole at 298.15 K, ΔfHmo(PhOCH3, l) = −(117.1 ± 1.4) kJ·mol(-1). The corresponding enthalpy of vaporization was obtained as, ΔvapHmo(PhOCH3) = 46.41 ± 0.26 kJ·mol(-1), by Calvet-drop microcalorimetry. These results give ΔfHmo(PhOCH3, g) = −(70.7 ± 1.4) kJ·mol(-1), in excellent agreement with ΔfHmo(PhOCH3, g) = −(70.8 ± 3.2) kJ·mol(-1), obtained from the W2-F12 calculations. The ΔfHmo(PhOCH3, g) here recommended leads to ΔfHmo(PhO•, g) = 55.5 ± 2.4 kJ·mol(-)1 and DH°(PhO-H) = 368.1 ± 2.6 kJ·mol(-1).

Experimental formation enthalpies for intermetallic phases and other inorganic compounds

Science.gov (United States)

Kim, George; Meschel, S. V.; Nash, Philip; Chen, Wei

2017-01-01

The standard enthalpy of formation of a compound is the energy associated with the reaction to form the compound from its component elements. The standard enthalpy of formation is a fundamental thermodynamic property that determines its phase stability, which can be coupled with other thermodynamic data to calculate phase diagrams. Calorimetry provides the only direct method by which the standard enthalpy of formation is experimentally measured. However, the measurement is often a time and energy intensive process. We present a dataset of enthalpies of formation measured by high-temperature calorimetry. The phases measured in this dataset include intermetallic compounds with transition metal and rare-earth elements, metal borides, metal carbides, and metallic silicides. These measurements were collected from over 50 years of calorimetric experiments. The dataset contains 1,276 entries on experimental enthalpy of formation values and structural information. Most of the entries are for binary compounds but ternary and quaternary compounds are being added as they become available. The dataset also contains predictions of enthalpy of formation from first-principles calculations for comparison. PMID:29064466

Enthalpy increment measurements of NaCrO2 using a high temperature Calvet calorimeter

International Nuclear Information System (INIS)

Iyer, V.S.; Jayanthi, K.; Ramarao, G.A.; Venugopal, V.; Sood, D.D.

1991-01-01

Enthalpy increment measurements on NaCrO 2 (s) were carried out in the temperature range 323 to 839 K using a high temperature Calvet micro calorimeter. The enthalpy increment values were least-squares fitted with temperature with the constraint that (Hdeg T - Hdeg 298 ) at 298.18 K equals zero, and can be given by: (Hdeg T - Hdeg 298 ) J/mol) ± 336 = -23515 + 75.364T(K) + 0.01256T 2 (K) (323 to 839 K). The first differential of the above equation with temperature gives the constant pressure molar heat capacity of NaCrO 2 (s), which is given by: Cdeg p (NaCrO 2 , s, T) (J/K mol) = 75.364 + 0.02512T(K). The thermal properties of NaCrO 2 (s) were calculated using the molar heat capacities from the present study and Sdeg(298 K) from the literature. (orig.)

Development and analysis of an economizer control strategy algorithm to promote an opportunity for energy savings in air conditioning installations

Energy Technology Data Exchange (ETDEWEB)

Neto, Jose H.M.; Azevedo, Walter L. [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET), Belo Horizonte, MG (Brazil). Dept. de Engenharia Mecanica]. E-mail: henrique@daem.des.cefetmg.br

2000-07-01

This work presents an algorithm control strategy denominated enthalpy economizer. The objective of this algorithm strategy is to determine the adequate fractions of outside and return air flowrates entering a cooling coil based on the analysis of the outside, return and supply air enthalpies, rather than on the analysis of the dry bulb temperatures. The proposed algorithm predicts the actual opening position of the outside and return air dampers in order to provide the lower mixing air enthalpy. First, the psychometrics properties of the outside and return air are calculated from actual measurements of the dry and wet bulb temperatures. Then, three distinct cases are analyzed: the enthalpy of the outside air is lower than the enthalpy of the supply air (free cooling); the enthalpy of the outside air is higher than the enthalpy of the return air; the enthalpy of the outside air is lower than the enthalpy of the return air and higher than the temperature of the supply air. Different outside air conditions were selected in order to represent typical weather data of Brazilians cities, as well as typical return air conditions. It was found that the enthalpy control strategy could promote an opportunity for energy savings mainly during mild nights and wintertime periods as well as during warm afternoons and summertime periods, depending on the outside air relative humidity. The proposed algorithm works well and can be integrated in some commercial automation software to reduce energy consumption and electricity demand. (author)

COTHERM: Geophysical Modeling of High Enthalpy Geothermal Systems

Science.gov (United States)

Grab, Melchior; Maurer, Hansruedi; Greenhalgh, Stewart

2014-05-01

In recent years geothermal heating and electricity generation have become an attractive alternative energy resource, especially natural high enthalpy geothermal systems such as in Iceland. However, the financial risk of installing and operating geothermal power plants is still high and more needs to be known about the geothermal processes and state of the reservoir in the subsurface. A powerful tool for probing the underground system structure is provided by geophysical techniques, which are able to detect flow paths and fracture systems without drilling. It has been amply demonstrated that small-scale features can be well imaged at shallow depths, but only gross structures can be delineated for depths of several kilometers, where most high enthalpy systems are located. Therefore a major goal of our study is to improve geophysical mapping strategies by multi-method geophysical simulations and synthetic data inversions, to better resolve structures at greater depth, characterize the reservoir and monitor any changes within it. The investigation forms part of project COTHERM - COmbined hydrological, geochemical and geophysical modeling of geoTHERMal systems - in which a holistic and synergistic approach is being adopted to achieve multidisciplinary cooperation and mutual benefit. The geophysical simulations are being performed in combination with hydrothermal fluid flow modeling and chemical fluid rock interaction modeling, to provide realistic constraints on lithology, pressure, temperature and fluid conditions of the subsurface. Two sites in Iceland have been selected for the study, Krafla and Reykjanes. As a starting point for the geophysical modeling, we seek to establish petrophysical relations, connecting rock properties and reservoir conditions with geophysical parameters such as seismic wave speed, attenuation, electrical conductivity and magnetic susceptibility with a main focus on seismic properties. Therefore, we follow a comprehensive approach involving

Formation enthalpy of iron, chromium and aluminium vanadates

International Nuclear Information System (INIS)

Kesler, Ya.A.; Cheshnitskij, S.M.; Fotiev, A.A.; Tret'yakov, Yu.D.

1985-01-01

The enthalpies of formation of FeVO 4 , CrVO 4 and AlVO 4 orthovanadates are determined. The method for measuring reaction heats of direct synthesis of oxide compounds is used. All experiments have been conducted at 973 K. The measurements have been performed by the drop-calorimetry method using high temperature differential microcalorimeter. The specified enthalpy values of FeVO 4 , CrVO 4 , AlVO 4 and FeCr(VO 4 ) 2 formation are obtained

A molecular dynamics study of ambient and high pressure phases of silica: structure and enthalpy variation with molar volume.

Science.gov (United States)

Rajappa, Chitra; Sringeri, S Bhuvaneshwari; Subramanian, Yashonath; Gopalakrishnan, J

2014-06-28

Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume-for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.

Étude de l'énergétique de l'air humide et des paramétrisations physiques de l'atmosphère : propriétés de l'exergie, de l'enthalpie utilisable, de l'entropie et de l'enthalpie

OpenAIRE

Marquet , Pascal

2016-01-01

This memory describes my old research activities (since 1988) about the application to atmospheric energetics of the concept of "available enthalpy", one of the form of what is called "exergy" in general thermodynamics. This memoir also describes my new research activities, started in 2008, on the study of the Third Law of thermodynamics and the corresponding absolute definition of the moist-air entropy.; Ce mémoire de HDR retrace, d'une part, les recherches engagées depuis 1988 sur les appli...

Anomalous enthalpy relaxation in vitreous silica

DEFF Research Database (Denmark)

Yue, Yuanzheng

2015-01-01

scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hyperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....

Standard molar enthalpies of formation of 1- and 2-cyanonaphthalene

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Lobo Ferreira, Ana I.M.C.; Barros, Ana L.M.; Bessa, Ana R.C.; Brito, Barbara C.S.A.; Vieira, Joana A.S.; Martins, Silvia A.P.

2011-01-01

Highlights: → Enthalpies of formation of 1- and 2-cyanonaphthalene were measured by combustion calorimetry. → Vapor pressures of crystalline 1- and 2-cyanonaphthalene obtained by Knudsen effusion mass loss technique. → Enthalpies, entropies and Gibbs functions of sublimation at T = 298.15 K were calculated. - Abstract: The standard (p o = 0.1 MPa) molar enthalpies of formation, in the crystalline state, of the 1- and 2-cyanonaphthalene were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static-bomb combustion calorimetry. Vapor pressure measurements at different temperatures, using the Knudsen mass loss effusion technique, enabled the determination of the enthalpy, entropy, and Gibbs energy of sublimation, at T = 298.15 K, for both isomers. The standard molar enthalpies of sublimation, at T = 298.15 K, for 1- and 2-cyanonaphthalene, were also measured by high-temperature Calvet microcalorimetry. (table) Combining these two experimental values, the gas-phase standard molar enthalpies, at T = 298.15 K, were derived and compared with those estimated by employing two different methodologies: one based on the Cox scheme and the other one based on G3MP2B3 calculations. The calculated values show a good agreement with the experimental values obtained in this work.

Formation enthalpy of iron, chromium and aluminium vanadates

Energy Technology Data Exchange (ETDEWEB)

Kesler, Ya.A.; Cheshnitskij, S.M.; Fotiev, A.A.; Tret' yakov, Yu.D.

1985-04-01

The enthalpies of formation of FeVO/sub 4/, CrVO/sub 4/ and AlVO/sub 4/ orthovanadates are determined. The method for measuring reaction heats of direct synthesis of oxide compounds is used. All experiments have been conducted at 973 K. The measurements have been performed by the drop-calorimetry method using high temperature differential microcalorimeter. The specified enthalpy values of FeVO/sub 4/, CrVO/sub 4/, AlVO/sub 4/ and FeCr(VO/sub 4/)/sub 2/ formation are obtained.

New experimental heat capacity and enthalpy of formation of lithium cobalt oxide

International Nuclear Information System (INIS)

Gotcu-Freis, Petronela; Cupid, Damian M.; Rohde, Magnus; Seifert, Hans J.

2015-01-01

Highlights: • LiCoO 2 heat capacity was measured in the temperature range (160 to 953) K using DSC. • Continuous/discontinuous methods were applied on different types of calorimeters. • Enthalpy increment of LiCoO 2 was determined using drop calorimetry at T = 974 K. • Enthalpies of formation were evaluated from oxide melt drop solution calorimetry. - Abstract: The heat capacity of LiCoO 2 (O3-phase), constituent material in cathodes for lithium-ion batteries, was measured using two differential scanning calorimeters over the temperature range from (160 to 953) K (continuous method). As an alternative, the discontinuous method was employed over the temperature range from (493 to 693) K using a third calorimeter. Based on the results obtained, the enthalpy increment of LiCoO 2 was derived from T = 298.15 K up to 974.15 K. Very good agreement was obtained between the derived enthalpy increment and our independent measurements of enthalpy increment using transposed temperature drop calorimetry at 974.15 K. In addition, values of the enthalpy of formation of LiCoO 2 from the constituent oxides and elements were assessed based on measurements of enthalpy of dissolution using high temperature oxide melt drop solution calorimetry. The high temperature values obtained by these measurements are key input data in safety analysis and optimisation of the battery management systems which accounts for possible thermal runaway events

The enthalpies of formation of two dibenzocyclooctadienones

Energy Technology Data Exchange (ETDEWEB)

Perisanu, St.; Contineanu, Iulia; Banciu, M.D.; Liebman, Joel F.; Farivar, Behzad S.; Mullan, Melissa A.; Chickos, James S.; Rath, Nigam; Hillesheim, Dorothea M

2003-04-17

The standard molar enthalpies of formation ({delta}{sub f}H{sub m}{sup 0}(s)/kJ mol{sup -1}) for 2,3:6,7-dibenzocycloocta-2,6-dien-1-one and 2,3:7,8-dibenzocycloocta-2,7-dien-1-one [6H-11,12-dihydro-dibenzo[a,e]cycloocten-5-one (ketone 1) and 10H-11,12-dihydrodibenzo[a,d]-cycloocten-5-one (ketone 2), respectively] were derived from enthalpies of combustion, measured by means of a microbomb calorimeter. The fusion and vaporization enthalpies of these compounds were obtained from DSC and correlation gas chromatography measurements. The standard molar enthalpies of formation in the gas phase were calculated by combining the condensed phase standard molar enthalpies of formation with the fusion and vaporization enthalpies adjusted to 298.15 K. Values for {delta}{sub f}H{sub m}{sup 0}(g) of (-39.9{+-}5.5) and (-14.8{+-}5.3) kJ mol{sup -1} were obtained for 2,3:6,7-dibenzocycloocta-2,6-dien-1-one and 2,3:7,8-dibenzocycloocta-2,7-dien-1-one, respectively. Quantum chemical calculations are reported for the compounds investigated experimentally and an additional four isomers. Isomerization enthalpies are derived from computed energies. The enthalpies of formation are also calculated by group additivity, compared with the experimental values and then correlated with the structure of the molecules investigated. The X-ray analysis of ketone 1 is also reported.

The enthalpies of formation of two dibenzocyclooctadienones

International Nuclear Information System (INIS)

Perisanu, St.; Contineanu, Iulia; Banciu, M.D.; Liebman, Joel F.; Farivar, Behzad S.; Mullan, Melissa A.; Chickos, James S.; Rath, Nigam; Hillesheim, Dorothea M.

2003-01-01

The standard molar enthalpies of formation (Δ f H m 0 (s)/kJ mol -1 ) for 2,3:6,7-dibenzocycloocta-2,6-dien-1-one and 2,3:7,8-dibenzocycloocta-2,7-dien-1-one [6H-11,12-dihydro-dibenzo[a,e]cycloocten-5-one (ketone 1) and 10H-11,12-dihydrodibenzo[a,d]-cycloocten-5-one (ketone 2), respectively] were derived from enthalpies of combustion, measured by means of a microbomb calorimeter. The fusion and vaporization enthalpies of these compounds were obtained from DSC and correlation gas chromatography measurements. The standard molar enthalpies of formation in the gas phase were calculated by combining the condensed phase standard molar enthalpies of formation with the fusion and vaporization enthalpies adjusted to 298.15 K. Values for Δ f H m 0 (g) of (-39.9±5.5) and (-14.8±5.3) kJ mol -1 were obtained for 2,3:6,7-dibenzocycloocta-2,6-dien-1-one and 2,3:7,8-dibenzocycloocta-2,7-dien-1-one, respectively. Quantum chemical calculations are reported for the compounds investigated experimentally and an additional four isomers. Isomerization enthalpies are derived from computed energies. The enthalpies of formation are also calculated by group additivity, compared with the experimental values and then correlated with the structure of the molecules investigated. The X-ray analysis of ketone 1 is also reported

Determination of melting and solidification enthalpy of hypereutectic silumins

Directory of Open Access Journals (Sweden)

J. Piątkowski

2008-04-01

Full Text Available The study was related with determination of the values of enthalpy of melting and solidification of hypereutectic AlSi18, AlSi21 and AlSi24 silumins modified with phosphorus in the form of Cu-P. The calorimetry, preceded by thermal analysis and derivative thermal analysis (TA and DTA, respectively was carried out on a high-temperature scanning calorimeter, model MHTC-96, made by SETARAM, applying the method of direct determination of parameters of the high-temperature process, and in particular of the enthalpy of phase transformations. Modern control and measuring instruments coupled with PC computer provide a very precise tool for determination of these transformations. An additional advantage was development of appropriate software called „SETSOFT”, owing to which it was possible to determine in an easy way the enthalpy of the investigated phase transformations. Moreover, an additional thermal effect, related most probably with pre-eutectic crystallization of primary silicon, was observed and confirmed by calorimetric examinations.

Enthalpy of Formation of N2H4 (Hydrazine) Revisited.

Science.gov (United States)

Feller, David; Bross, David H; Ruscic, Branko

2017-08-17

In order to address the accuracy of the long-standing experimental enthalpy of formation of gas-phase hydrazine, fully confirmed in earlier versions of Active Thermochemical Tables (ATcT), the provenance of that value is re-examined in light of new high-end calculations of the Feller-Peterson-Dixon (FPD) variety. An overly optimistic determination of the vaporization enthalpy of hydrazine, which created an unrealistically strong connection between the gas phase thermochemistry and the calorimetric results defining the thermochemistry of liquid hydrazine, was identified as the probable culprit. The new enthalpy of formation of gas-phase hydrazine, based on balancing all available knowledge, was determined to be 111.57 ± 0.47 kJ/mol at 0 K (97.42 ± 0.47 kJ/mol at 298.15 K). Close agreement was found between the ATcT (even excluding the latest theoretical result) and the FPD enthalpy.

Treatment of refractory powders by a novel, high enthalpy dc plasma

Science.gov (United States)

Pershin, L.; Mitrasinovic, A.; Mostaghimi, J.

2013-06-01

Thermophysical properties of CO2-CH4 mixtures at high temperatures are very attractive for materials processing. In comparison with argon, at the same temperature, such a mixture possesses much higher enthalpy and higher thermal conductivity. At high temperatures, CO2-CH4 mixture has a complex composition with strong presence of CO which, in the case of powder treatment, could reduce oxidation. In this work, a dc plasma torch with graphite cathode was used to study the effect of plasma gas composition on spheroidization of tungsten carbide and alumina powders. Two different gas compositions were used to generate the plasma while the torch current was kept at 300 A. Various techniques were employed to assess the average concentration of carbides and oxides and the final shape of the treated powders. Process parameters such as input power and plasma gas composition allow controlling the degree of powder oxidation and spheroidization of high melting point ceramic powders.

Treatment of refractory powders by a novel, high enthalpy dc plasma

International Nuclear Information System (INIS)

Pershin, L; Mitrasinovic, A; Mostaghimi, J

2013-01-01

Thermophysical properties of CO 2 –CH 4 mixtures at high temperatures are very attractive for materials processing. In comparison with argon, at the same temperature, such a mixture possesses much higher enthalpy and higher thermal conductivity. At high temperatures, CO 2 –CH 4 mixture has a complex composition with strong presence of CO which, in the case of powder treatment, could reduce oxidation. In this work, a dc plasma torch with graphite cathode was used to study the effect of plasma gas composition on spheroidization of tungsten carbide and alumina powders. Two different gas compositions were used to generate the plasma while the torch current was kept at 300 A. Various techniques were employed to assess the average concentration of carbides and oxides and the final shape of the treated powders. Process parameters such as input power and plasma gas composition allow controlling the degree of powder oxidation and spheroidization of high melting point ceramic powders. (paper)

Enthalpies of a binary alloy during solidification

Science.gov (United States)

Poirier, D. R.; Nandapurkar, P.

1988-01-01

The purpose of the paper is to present a method of calculating the enthalpy of a dendritic alloy during solidification. The enthalpies of the dendritic solid and interdendritic liquid of alloys of the Pb-Sn system are evaluated, but the method could be applied to other binaries, as well. The enthalpies are consistent with a recent evaluation of the thermodynamics of Pb-Sn alloys and with the redistribution of solute in the same during dendritic solidification. Because of the heat of mixing in Pb-Sn alloys, the interdendritic liquid of hypoeutectic alloys (Pb-rich) of less than 50 wt pct Sn has enthalpies that increase as temperature decreases during solidification.

Standard molar enthalpies of formation of 2-, 3- and 4-cyanobenzoic acids

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Amaral, Luisa M.P.F.; Boaventura, Cristina R.P.; Gomes, Jose R.B.

2008-01-01

The standard (p 0 = 0.1 MPa) molar enthalpies of formation of 2-, 3- and 4-cyanobenzoic acids were derived from their standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpies of sublimation of 2- and 3-cyanobenzoic acids. The standard molar enthalpies of formation of the three compounds, in the gaseous phase, at T = 298.15 K, have been derived from the corresponding standard molar enthalpies of formation in the condensed phase and standard molar enthalpies for phase transition. The results obtained are -(150.7 ± 2.0) kJ . mol -1 , -(153.6 ± 1.7) kJ . mol -1 and -(157.1 ± 1.4) kJ . mol -1 for 2-cyano, 3-cyano and 4-cyanobenzoic acids, respectively. Standard molar enthalpies of formation were also estimated by employing two different methodologies: one based on the Cox scheme and the other one based on several different computational approaches. The calculated values show a good agreement with the experimental values obtained in this work

Enthalpy of mixing of liquid Co–Sn alloys

International Nuclear Information System (INIS)

Yakymovych, A.; Fürtauer, S.; Elmahfoudi, A.; Ipser, H.; Flandorfer, H.

2014-01-01

Highlights: • The enthalpies of mixing of liquid Co–Sn alloys between T = (673 and 1773) K. • The temperature dependence of the enthalpies of mixing was described. • Full report of measured values including polynomial coefficients. - Abstract: A literature overview of enthalpy of mixing data for liquid Co–Sn alloys shows large scattering but no clear temperature dependence. Therefore drop calorimetry was performed in the Co–Sn system at twelve different temperatures in 100 K steps in the temperature range (673 to 1773) K. The integral enthalpy of mixing was determined starting from 1173 K and fitted to a standard Redlich–Kister polynomial. In addition, the limiting partial molar enthalpy of Co in Sn was investigated by small additions of Co to liquid Sn at temperatures (673 to 1773) K. The integral and partial molar enthalpies of the Co–Sn system generally show an exothermic mixing behavior. Significant temperature dependence was detected for the enthalpies of mixing. The minimum integral enthalpy values vary with rising temperature from approx. −7820 J/mol at T = 1173 K to −1350 J/mol at T = 1773 K; the position of the minimum is between (59 and 61) at.% Co. The results are discussed and compared with literature data available for this system. X-ray studies and scanning electron microscopy of selected alloys obtained from the calorimetric measurements were carried out in order to check the completeness of the solution process

Thermochemistry of methoxythiophenes: Measurement of their enthalpies of vaporization and estimation of their enthalpies of formation in the condensed phase

International Nuclear Information System (INIS)

Temprado, Manuel; Notario, Rafael; Roux, María Victoria; Verevkin, Sergey P.

2014-01-01

Highlights: • The enthalpies of vaporization of 2- and 3-methoxythiophenes have been measured by the transpiration method. • We have estimated the enthalpies of formation of methoxythiophenes in liquid phase. • The optimized geometries of methoxythiophenes have been tabulated and compared with the experimental crystal structures. - Abstract: Enthalpies of vaporization of 2- and 3-methoxythiophenes (48.32 ± 0.30 and 48.54 ± 0.22 kJ · mol −1 , respectively) have been measured by the transpiration method using nitrogen as the carrying and protecting stream. Combustion experiments leading to enthalpies of formation in the liquid phase, Δ f H 0 m (l), for both isomers failed due to rapid darkening of freshly distilled samples even under a protecting atmosphere. However, combination of experimental vaporization enthalpies with values of the gaseous enthalpies of formation, Δ f H 0 m (g), obtained by quantum-chemical calculations from our previous work Notario et al. (2012) [24] permits establishing estimated Δ f H 0 m (l) values of −(68.3 ± 4.2) and −(80.1 ± 4.2) kJ · mol −1 , for 2- and 3-methoxythiophene, respectively

Calculating the enthalpy of vaporization for ionic liquid clusters.

Science.gov (United States)

Kelkar, Manish S; Maginn, Edward J

2007-08-16

Classical atomistic simulations are used to compute the enthalpy of vaporization of a series of ionic liquids composed of 1-alkyl-3-methylimidazolium cations paired with the bis(trifluoromethylsulfonyl)imide anion. The calculations show that the enthalpy of vaporization is lowest for neutral ion pairs. The enthalpy of vaporization increases by about 40 kJ/mol with the addition of each ion pair to the vaporizing cluster. Non-neutral clusters have much higher vaporization enthalpies than their neutral counterparts and thus are not expected to make up a significant fraction of volatile species. The enthalpy of vaporization increases slightly as the cation alkyl chain length increases and as temperature decreases. The calculated vaporization enthalpies are consistent with two sets of recent experimental measurements as well as with previous atomistic simulations.

Ionic liquids: differential scanning calorimetry as a new indirect method for determination of vaporization enthalpies.

Science.gov (United States)

Verevkin, Sergey P; Emel'yanenko, Vladimir N; Zaitsau, Dzmitry H; Ralys, Ricardas V; Schick, Christoph

2012-04-12

Differential scanning calorimetry (DSC) has been used to measure enthalpies of synthesis reactions of the 1-alkyl-3-methylimidazolium bromide [C(n)mim][Br] ionic liquids from 1-methylimidazole and n-alkyl bromides (with n = 4, 5, 6, 7, and 8). The optimal experimental conditions have been elaborated. Enthalpies of formation of these ionic liquids in the liquid state have been determined using the DSC results according to the Hess Law. The ideal-gas enthalpies of formation of [C(n)mim][Br] were calculated using the methods of quantum chemistry. They were used together with the DSC results to derive indirectly the enthalpies of vaporization of the ionic liquids under study. In order to validate the indirect determination, the experimental vaporization enthalpy of [C(4)mim][Br] was measured by using a quartz crystal microbalance (QCM). The combination of reaction enthalpy measurements by DSC with modern high-level first-principles calculations opens valuable indirect thermochemical options to obtain values of vaporization enthalpies of ionic liquids.

A DFT study on the enthalpies of thermite reactions and enthalpies of formation of metal composite oxide

Science.gov (United States)

Zhang, Yu-ying; Wang, Meng-jie; Chang, Chun-ran; Xu, Kang-zhen; Ma, Hai-xia; Zhao, Feng-qi

2018-05-01

The standard thermite reaction enthalpies (ΔrHmθ) for seven metal oxides were theoretically analyzed using density functional theory (DFT) under five different functional levels, and the results were compared with experimental values. Through the comparison of the linear fitting constants, mean error and root mean square error, the Perdew-Wang functional within the framework of local density approximation (LDA-PWC) and Perdew-Burke-Ernzerhof exchange-correlation functional within the framework of generalized gradient approximation (GGA-PBE) were selected to further calculate the thermite reaction enthalpies for metal composite oxides (MCOs). According to the Kirchhoff formula, the standard molar reaction enthalpies for these MCOs were obtained and their standard molar enthalpies of formation (ΔfHmθ) were finally calculated. The results indicated that GGA-PBE is the most suitable one out of the total five methods to calculate these oxides. Tungstate crystals present the maximum deviation of the enthalpies of thermite reactions for MCOs and these of their physical metal oxide mixtures, but ferrite crystals are the minimum. The correlation coefficients are all above 0.95, meaning linear fitting results are very precise. And the molar enthalpies of formation for NiMoO4, CuMoO4, PbZrO3 (Pm/3m), PbZrO3 (PBA2), PbZrO3 (PBam), MgZrO3, CdZrO3, MnZrO3, CuWO4 and Fe2WO6 were first obtained as -1078.75, -1058.45, -1343.87, -1266.54, -1342.29, -1333.03, -1210.43, -1388.05, -1131.07 and - 1860.11 kJ·mol-1, respectively.

Standard enthalpies of formation of some Lanthanide–Cobalt binary alloys by high temperature direct synthesis calorimetry

Energy Technology Data Exchange (ETDEWEB)

Meschel, S.V., E-mail: meschel@jfi.uchicago.edu [Illinois Institute of Technology, Thermal Processing Technology Center, 10 W. 32nd Street, Chicago, IL (United States); University of Chicago, Gordon Center of Interactive Science, 929 E 57th Street, Chicago, IL 60637 (United States); Nash, P. [Illinois Institute of Technology, Thermal Processing Technology Center, 10 W. 32nd Street, Chicago, IL (United States); Gao, Q.N.; Wang, J.C.; Du, Y. [Central South University, State Key Laboratory of Powder Metallurgy, Changsha, Hunan 410083 (China)

2013-11-25

Highlights: •Studied binary Lanthanide–Cobalt intermetallic alloys by high temperature calorimetry. •Determined the enthalpies of formation of 16 magnetostrictive alloys. •Compared the experimental measurements with theoretical predictions by two different models. -- Abstract: The standard enthalpies of formation of intermetallic compounds of some Lanthanide–Cobalt systems have been measured by high temperature direct synthesis calorimetry at 1373 ± 2 K. The following results in kJ/mol of atoms are reported: CeCo{sub 5}(−9.4 ± 3.3); Ce{sub 2}Co{sub 17}(−6.8 ± 3.2); PrCo{sub 5}(−10.5 ± 2.4); Pr{sub 2}Co{sub 17}(−6.8 ± 3.6); NdCo{sub 5}(−12.7 ± 2.6); Nd{sub 2}Co{sub 17}(−6.6 ± 2.7); SmCo{sub 5}(−12.2 ± 1.8); Sm{sub 2}Co{sub 17}(−7.2 ± 2.5); GdCo{sub 5}(−10.0 ± 2.4); Tb{sub 2}Co{sub 17}(−7.7 ± 2.9); Dy{sub 2}Co{sub 17}(−8.1 ± 2.9); HoCo{sub 3}(−17.5 ± 2.2); ErCo{sub 3}(−19.7 ± 3.3); TmCo{sub 3}(−22.9 ± 3.0); LuCo{sub 3}(−23.0 ± 2.6). The measurements are compared with values from the literature and with predicted values of the semi empirical model of Miedema and Coworkers. We also compare the measurements with predicted values by ab initio calculations. We will present a systematic picture of how the enthalpies of formation may be related to the atomic number of the Lanthanide element (LA). We will also compare the thermochemical behavior of the Fe, Co and Ni binary alloys with Lanthanide elements.

Impact of Flight Enthalpy, Fuel Simulant, and Chemical Reactions on the Mixing Characteristics of Several Injectors at Hypervelocity Flow Conditions

Science.gov (United States)

Drozda, Tomasz G.; Baurle, Robert A.; Drummond, J. Philip

2016-01-01

The high total temperatures or total enthalpies required to duplicate the high-speed flight conditions in ground experiments often place stringent requirements on the material selection and cooling needs for the test articles and intrusive flow diagnostic equipment. Furthermore, for internal flows, these conditions often complicate the use of nonintrusive diagnostics that need optical access to the test section and interior portions of the flowpath. Because of the technical challenges and increased costs associated with experimentation at high values of total enthalpy, an attempt is often made to reduce it. This is the case for the Enhanced Injection and Mixing Project (EIMP) currently underway in the Arc-Heated Scramjet Test Facility at the NASA Langley Research Center. The EIMP aims to investigate supersonic combustion ramjet (scramjet) fuel injection and mixing physics, improve the understanding of underlying physical processes, and develop enhancement strategies and functional relationships between mixing performance and losses relevant to flight Mach numbers greater than 8. The experiments will consider a "direct-connect" approach and utilize a Mach 6 nozzle to simulate the combustor entrance flow of a scramjet engine. However, while the value of the Mach number is matched to that expected at the combustor entrance in flight, the maximum value of the total enthalpy for these experiments is limited by the thermal-structural limits of the uncooled experimental hardware. Furthermore, the fuel simulant is helium, not hydrogen. The use of "cold" flows and non-reacting mixtures of fuel simulants for mixing experiments is not new and has been extensively utilized as a screening technique for scramjet fuel injectors. In this study, Reynolds-averaged simulations are utilized (RAS) to systematically verify the implicit assumptions used by the EIMP. This is accomplished by first performing RAS of mixing for two injector configurations at planned nominal experimental

Enthalpy of formation of zircon

International Nuclear Information System (INIS)

Ellison, A.J.G.; Navrotsky, A.

1992-01-01

Using high-temperature solution calorimetry in molt 2PbO · B 2 O 3 , the enthalpy of reaction of the formation of zircon, ZrSiO 4 , from its constituent oxides has been determined: Δ 4 H 977 (ZrSiO 4 ) = -27.9 (±1.9) kJ/mol. With previously reported data for the heat contents of ZrO 2 SiO 2 and ZrSiO 4 and standard-state enthalpies of formation of ZrO 2 and SiO 2 , we obtain Δ f H 298 degrees. (ZrSiO 4 ) = -2034.2 (±3.1) kJ/mol and Δ t G 298 degrees (ZrSiO 4 ) = -1919.8 kJ/mol. The free energy value is in excellent agreement with a range previously estimated from solid-state reaction equilibria. At higher temperature also the data are in close agreement with existing data, though the data sets diverge somewhat with increasing T. In this paper the limitations of the data for predicting the breakdown temperature of zircon into its constituent oxides are discussed

Standard molar enthalpies of formation of 2-furancarbonitrile, 2-acetylfuran, and 3-furaldehyde

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Amaral, Luisa M.P.F.

2009-01-01

The standard (p 0 = 0.1 MPa) molar energies of combustion of 2-furancarbonitrile, 2-acetylfuran, and 3-furaldehyde were measured by static bomb combustion calorimetry; the Calvet high-temperature microcalorimetry was used to measure the enthalpies of vaporization of these liquid compounds. The standard molar enthalpies of formation of the three compounds, in the gaseous phase, at T = 298.15 K, have been derived from the corresponding standard molar enthalpies of formation in the liquid phase and the standard molar enthalpies of phase transition, as (106.8 ± 1.1) kJ . mol -1 , -(207.4 ± 1.3) kJ . mol -1 , and -(151.9 ± 1.1) kJ . mol -1 , for 2-furancarbonitrile, 2-acetylfuran, and 3-furaldehyde, respectively. Standard molar enthalpies of formation are discussed in terms of the isomerization ortho meta. Enthalpic increment values of the introduction of the functional groups -CN, -CHO, and -COCH 3 were also compared with some other heterocycles; i.e. thiophene and pyridine

Study of containment air cooler capacity in steam air environment during accident conditions

International Nuclear Information System (INIS)

Kansal, M.; Mohan, N.; Bhawal, R.N.; Bajaj, S.S.

2002-01-01

Full text: The air coolers are provided for controlling the temperature in the reactor building during normal operation. These air coolers also serve as the main heat sink for the removal of energy from high enthalpy air-steam mixture expected in reactor building under accident conditions. A subroutine COOLER has been developed to estimate the heat removal rate of the air coolers at high temperature and steam conditions. The subroutine COOLER has been attached with the code PACSR (post accident containment system response) used for containment pressure temperature calculation. The subroutine was validated using design parameters at normal operating condition. A study was done to estimate the heat removal rate for some postulated accident conditions. The study reveals that, under accident conditions, the heat removal rate of air coolers increases several times compared with normal operating conditions

Experimental study on an innovative enthalpy recovery technology based on indirect flash evaporative cooling

DEFF Research Database (Denmark)

Nie, Jinzhe; Yuan, Shu; Fang, Lei

2018-01-01

recovery unit. The principle of the technology is to over saturate indoor exhaust air by ultrasonic atomizing humidification. The evaporation of ultrafine mists cools down indoor exhaust air to its wet-bulb temperature and makes not only sensible heat transfer but also moisture condensed in outdoor supply...... were measured to investigate and analyze its energy recover efficiencies. The results showed that in hot and humid climate, up to 71% of total heat recover efficiency could be achieved by the prototype unit, and more than 50% of the enthalpy recovered was contributed by moisture condensation...

Standard molar enthalpies of formation of monochloroacetophenone isomers

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Amaral, Luisa M.P.F.

2010-01-01

The standard (p 0 =0.1MPa) molar enthalpies of formation of the liquids 2'-, 3'-, and 4'-chloroacetophenones were derived from the standard molar energies of combustion, in oxygen, to yield CO 2 (g) and HCl . 600H 2 O(l), at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The Calvet microcalorimetry was used to measure the enthalpies of vaporization of the three compounds. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the chloroacetophenone isomers, in the gaseous phase, at T = 298.15 K. (table) An empirical scheme, developed by Cox, was used to estimate the gas-phase enthalpies of formation and the obtained values were compared with the experimental ones.

Enthalpy-entropy compensation: the role of solvation.

Science.gov (United States)

Dragan, Anatoliy I; Read, Christopher M; Crane-Robinson, Colyn

2017-05-01

Structural modifications to interacting systems frequently lead to changes in both the enthalpy (heat) and entropy of the process that compensate each other, so that the Gibbs free energy is little changed: a major barrier to the development of lead compounds in drug discovery. The conventional explanation for such enthalpy-entropy compensation (EEC) is that tighter contacts lead to a more negative enthalpy but increased molecular constraints, i.e., a compensating conformational entropy reduction. Changes in solvation can also contribute to EEC but this contribution is infrequently discussed. We review long-established and recent cases of EEC and conclude that the large fluctuations in enthalpy and entropy observed are too great to be a result of only conformational changes and must result, to a considerable degree, from variations in the amounts of water immobilized or released on forming complexes. Two systems exhibiting EEC show a correlation between calorimetric entropies and local mobilities, interpreted to mean conformational control of the binding entropy/free energy. However, a substantial contribution from solvation gives the same effect, as a consequence of a structural link between the amount of bound water and the protein flexibility. Only by assuming substantial changes in solvation-an intrinsically compensatory process-can a more complete understanding of EEC be obtained. Faced with such large, and compensating, changes in the enthalpies and entropies of binding, the best approach to engineering elevated affinities must be through the addition of ionic links, as they generate increased entropy without affecting the enthalpy.

Enthalpies of vaporization of organometallic compounds

International Nuclear Information System (INIS)

Kuznetsov, N.T.; Sevast'yanov, V.G.; Mitin, V.A.; Krasnodubskaya, S.V.; Zakharov, L.N.; Domrachev, G.A.; AN SSSR, Gor'kij. Inst. Khimii)

1987-01-01

A possibility to use the method of additive schemes for the calculation of vaporizaton enthalpies of uranium organometallic compounds is discussed while comparing the values obtained using the method with experimental data. The possibility of apriori evaluation of evaporation enthalpy values of different uranium compounds using the method of additive schemes and structural characteristics of molecules, such as the sum of ligand solid angles, is shown

Study on the enthalpy of solution and enthalpy of dilution for the ionic liquid [C3mim][Val] (1-propyl-3-methylimidazolium valine)

International Nuclear Information System (INIS)

Guan Wei; Li Long; Ma Xiaoxue; Tong Jing; Fang Dawei; Yang Jiazhen

2012-01-01

Graphical abstract: The thermodynamic cycle for estimation of the hydration enthalpy of ionic liquid [C 3 mim][Val]. Highlights: ► A new amino acid ionic liquid [C 3 mim][Val] was prepared. ► The molar enthalpies of solution of the ionic liquid. ► The hydration enthalpy of the cation [C 3 mim] + was estimated. ► The molar enthalpies of dilution, of aqueous [C 3 mim][Val] were measured. - Abstract: A new amino acid ionic liquid (AAIL) [C 3 mim][Val] (1-propyl-3-methylimidazolium valine) was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, molar solution enthalpies of the ionic liquid [C 3 mim][Val] with known amounts of water and with different concentrations in molality were measured at T = 298.15 K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C 3 mim][Val] without water, Δ s H m ∘ = (−55.7 ± 0.4) kJ · mol −1 , was obtained. The hydration enthalpy of the cation [C 3 mim] + , ΔH + ([C 3 mim] + ) = −226 kJ · mol −1 , was estimated in terms of Glasser’s theory. Using the RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, Δ D H m (m i → m f ), of aqueous [C 3 mim][Val] with various values of molality were measured. The values of Δ D H m (m i → m f ) were fitted to Pitzer’s ion-interaction model and the values of apparent relative molar enthalpy, φ L, calculated using Pitzer’s ion-interaction model.

Standard molar enthalpies of formation of copper(II) β-diketonates and monothio-β-diketonates

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Santos, Luis M.N.B.F.

2006-01-01

The standard (p o =0.1MPa) molar enthalpies of formation of the crystalline complexes of dibenzoylmethane (Hdbm), thenoyltrifluoroacetone (Httfa), monothiodibenzoylmethane (HdbmS), and monothiothenoyltrifluoroacetone (HttfaS) of copper(II) were determined, at T=298.15K, by high precision solution-reaction calorimetry. The standard molar enthalpies of sublimation of the copper(II) β-diketonate complexes were measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean molar dissociation enthalpies copper(II)-ligand, m >(Cu-L), were derived. Δ f H m o (cr)Δ cr g H m o kJ.mol -1 kJ.mol -1 Bis(dibenzoylmethanate)copper(II), Cu(dbm) 2 -364.0+/-3.9230.7+/-8.2Bis(thenoyltrifluoroacetonate)copper(II), Cu(ttfa) 2 -1824.3+/-8.3167.9+/-7.4Bis(monothiodibenzoylmethanate)copper(II), Cu(dbmS) 2 35.6+/-7.7[241+/-15]Bis(monothiothenoyltrifluoroacetonate) copper(II), Cu(ttfaS) 2 -1405.7+/-8.3[177+/-15

Boundary Layer Transition and Trip Effectiveness on an Apollo Capsule in the JAXA High Enthalpy Shock Tunnel (HIEST) Facility

Science.gov (United States)

Kirk, Lindsay C.; Lillard, Randolph P.; Olejniczak, Joseph; Tanno, Hideyuki

2015-01-01

Computational assessments were performed to size boundary layer trips for a scaled Apollo capsule model in the High Enthalpy Shock Tunnel (HIEST) facility at the JAXA Kakuda Space Center in Japan. For stagnation conditions between 2 MJ/kg and 20 MJ/kg and between 10 MPa and 60 MPa, the appropriate trips were determined to be between 0.2 mm and 1.3 mm high, which provided kappa/delta values on the heatshield from 0.15 to 2.25. The tripped configuration consisted of an insert with a series of diamond shaped trips along the heatshield downstream of the stagnation point. Surface heat flux measurements were obtained on a capsule with a 250 mm diameter, 6.4% scale model, and pressure measurements were taken at axial stations along the nozzle walls. At low enthalpy conditions, the computational predictions agree favorably to the test data along the heatshield centerline. However, agreement becomes less favorable as the enthalpy increases conditions. The measured surface heat flux on the heatshield from the HIEST facility was under-predicted by the computations in these cases. Both smooth and tripped configurations were tested for comparison, and a post-test computational analysis showed that kappa/delta values based on the as-measured stagnation conditions ranged between 0.5 and 1.2. Tripped configurations for both 0.6 mm and 0.8 mm trip heights were able to effectively trip the flow to fully turbulent for a range of freestream conditions.

Computer program for obtaining thermodynamic and transport properties of air and products of combustion of ASTM-A-1 fuel and air

Science.gov (United States)

Hippensteele, S. A.; Colladay, R. S.

1978-01-01

A computer program for determining desired thermodynamic and transport property values by means of a three-dimensional (pressure, fuel-air ratio, and either enthalpy or temperature) interpolation routine was developed. The program calculates temperature (or enthalpy), molecular weight, viscosity, specific heat at constant pressure, thermal conductivity, isentropic exponent (equal to the specific heat ratio at conditions where gases do not react), Prandtl number, and entropy for air and a combustion gas mixture of ASTM-A-1 fuel and air over fuel-air ratios from zero to stoichiometric, pressures from 1 to 40 atm, and temperatures from 250 to 2800 K.

Relationships between fusion, solution, vaporization and sublimation enthalpies of substituted phenols

International Nuclear Information System (INIS)

Yagofarov, Mikhail I.; Nagrimanov, Ruslan N.; Solomonov, Boris N.

2017-01-01

Highlights: • Method for determination of sublimation and vaporization enthalpies of phenols was developed. • Vaporization enthalpies of 28 phenols at 298 K were calculated. • Sublimation enthalpies of 26 phenols at 298 K were calculated using fusion enthalpies at melting temperatures. • Obtained values are in good agreement with the results of conventional methods. - Abstract: In this work a method for determination of sublimation and vaporization enthalpies of substituted phenols was developed. This method is a modification of solution calorimetry approach. Modification is based on the novel relations, which bind solution, vaporization and sublimation enthalpies at 298.15 K and fusion enthalpy at the melting temperature. According to novel relations the equations for calculating sublimation and vaporization enthalpies at 298.15 K were offered. Calculated values of sublimation and vaporization enthalpies of phenol derivatives containing alkyls, halogens, –OCH 3 , –NO 2 , –COCH 3 , –COOCH 3 groups, and dihydroxybenzenes were compared with literature data (298.15 K) obtained by conventional methods. In most of the cases divergence does not exceed 2–3%.

Standard molar enthalpies of formation of monochloroacetophenone isomers

Energy Technology Data Exchange (ETDEWEB)

Ribeiro da Silva, Manuel A.V., E-mail: risilva@fc.up.p [Centro de Investigacao em Quimica, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Amaral, Luisa M.P.F. [Centro de Investigacao em Quimica, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)

2010-12-15

The standard (p{sup 0}=0.1MPa) molar enthalpies of formation of the liquids 2'-, 3'-, and 4'-chloroacetophenones were derived from the standard molar energies of combustion, in oxygen, to yield CO{sub 2}(g) and HCl . 600H{sub 2}O(l), at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The Calvet microcalorimetry was used to measure the enthalpies of vaporization of the three compounds. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the chloroacetophenone isomers, in the gaseous phase, at T = 298.15 K. (table) An empirical scheme, developed by Cox, was used to estimate the gas-phase enthalpies of formation and the obtained values were compared with the experimental ones.

The thermochemistry of 2,4-pentanedione revisited: observance of a nonzero enthalpy of mixing between tautomers and its effects on enthalpies of formation.

Science.gov (United States)

Temprado, Manuel; Roux, Maria Victoria; Umnahanant, Patamaporn; Zhao, Hui; Chickos, James S

2005-06-30

The enthalpies of formation of pure liquid and gas-phase (Z)-4-hydroxy-3-penten-2-one and 2,4-pentanedione are examined in the light of some more recent NMR studies on the enthalpy differences between gas-phase enthalpies of the two tautomers. Correlation gas chromatography experiments are used to evaluate the vaporization enthalpies of the pure tautomers. Values of (51.2 +/- 2.2) and (50.8 +/- 0.6) kJ.mol(-1) are measured for pure 2,4-pentanedione and (Z)-4-hydroxy-3-penten-2-one, respectively. The value of (50.8 +/- 0.6) kJ.mol(-1) can be contrasted to a value of (43.2 +/- 0.2) kJ.mol(-1) calculated for pure (Z)-4-hydroxy-3-penten-2-one when the vaporization enthalpy is measured in a mixture of tautomers. The difference is attributed to an endothermic enthalpy of mixing that destabilizes the mixture relative to the pure components. Calculation of new enthalpies of formation for (Z)-4-hydroxy-3-penten-2-one and 2,4-pentanedione in both the gas, Delta(f)H degrees (m)(g) = (-378.2 +/- 1.2) and (-358.9 +/- 2.5) kJ.mol(-1), respectively, and liquid phases, Delta(f)H degrees (m)(l) = (-429.0 +/- 1.0) and (-410.1 +/- 1.2) kJ.mol(-1), respectively, results in enthalpy differences between the two tautomers both in the liquid and gas phases that are identical within experimental error, and in excellent agreement with recent gas-phase NMR studies.

The relationship between vapour pressure, vaporization enthalpy, and enthalpy of transfer from solution to gas: An extension of the Martin equation

International Nuclear Information System (INIS)

Srisaipet, A.; Aryusuk, K.; Lilitchan, S.; Krisnangkura, K.

2007-01-01

Martin's equation, Δ sln g G=Δ sln g G o +zδ sln g G, is extended to cover vaporization free energy (Δ l g G). The extended equation is further expanded in terms of enthalpy and entropy and then used to correlate vaporization enthalpy (Δ l g H) and enthalpy of transfer from solution to gas (Δ sln g H). Data available in the literatures are used to validate and support the speculations derived from the proposed equation

Standard molar enthalpies of formation of copper(II) {beta}-diketonates and monothio-{beta}-diketonates

Energy Technology Data Exchange (ETDEWEB)

Ribeiro da Silva, Manuel A.V. [Centro de Investigacao em Quimica, Departamento de Quimica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)]. E-mail: risilva@fc.up.pt; Santos, Luis M.N.B.F. [Centro de Investigacao em Quimica, Departamento de Quimica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)

2006-07-15

The standard (p{sup o}=0.1MPa) molar enthalpies of formation of the crystalline complexes of dibenzoylmethane (Hdbm), thenoyltrifluoroacetone (Httfa), monothiodibenzoylmethane (HdbmS), and monothiothenoyltrifluoroacetone (HttfaS) of copper(II) were determined, at T=298.15K, by high precision solution-reaction calorimetry. The standard molar enthalpies of sublimation of the copper(II) {beta}-diketonate complexes were measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean molar dissociation enthalpies copper(II)-ligand, (Cu-L), were derived. {delta}{sub f}H{sub m}{sup o} (cr){delta}{sub cr}{sup g}H{sub m}{sup o} kJ.mol{sup -1}kJ.mol{sup -1}Bis(dibenzoylmethanate)copper(II), Cu(dbm){sub 2}-364.0+/-3.9230.7+/-8.2Bis(thenoyltrifluoroacetonate)copper(II), Cu(ttfa){sub 2}-1824.3+/-8.3167.9+/-7.4Bis(monothiodibenzoylmethanate)copper(II), Cu(dbmS){sub 2}35.6+/-7.7[241+/-15]Bis(monothiothenoyltrifluoroacetonate) copper(II), Cu(ttfaS){sub 2}-1405.7+/-8.3[177+/-15].

Vapor pressures and enthalpies of vaporization of azides

International Nuclear Information System (INIS)

Verevkin, Sergey P.; Emel'yanenko, Vladimir N.; Algarra, Manuel; Manuel Lopez-Romero, J.; Aguiar, Fabio; Enrique Rodriguez-Borges, J.; Esteves da Silva, Joaquim C.G.

2011-01-01

Highlights: → We prepared and measured vapor pressures and vaporization enthalpies of 7 azides. → We examined consistency of new and available in the literature data. → Data for geminal azides and azido-alkanes selected for thermochemical calculations. - Abstract: Vapor pressures of some azides have been determined by the transpiration method. The molar enthalpies of vaporization Δ l g H m of these compounds were derived from the temperature dependencies of vapor pressures. The measured data sets were successfully checked for internal consistency by comparison with vaporization enthalpies of similarly structured compounds.

Enthalpies of formation of UAl1 and UAl3 by calorimetry

International Nuclear Information System (INIS)

Nagarajan, K.; Babu, R.; Mathews, C.K.

1993-01-01

Enthalpies of formation of the intermetallic compounds UAl 4 and UAl 3 at 298.15 K were determined by high temperature solution calorimetry in which liquid aluminium was used as the solvent. The thermal effects of dissolution of UAl 4 , UAl 3 and U in liquid aluminium were measured in separate experiments by dropping the samples held at the ambient temperature into liquid aluminium maintained at 980 K in the calorimeter. The thermal effects of dissolution of these samples at infinite dilution in liquid aluminium were derived from these measurements and based on this data the enthalpies of formation of UAl 4 and UAl 3 at 298.15 K were computed. The values obtained are ΔH f,298.15 (UAl 4 )=-126.5±13.3 kJ mol -1 and ΔH f,298.15 (UAl 3 )=-118.1±8.2 kJ mol -1 . The integral enthalpies of formation of U-Al alloys at 978 K, 1078 K and 1094 K were measured by dropping U samples maintained at the ambient temperature into liquid aluminium in the calorimeter at the experimental temperature. From the integral enthalpies of formation of U-Al alloys in the two phase regions, {U-Al}+ 4 > and {U-Al}+ 3 >, the enthalpies of formation of UAl 4 and UAl 3 , respectively, at the temperatures of measurement were derived. These results are discussed in comparison with the literature data. (orig.)

Enthalpy of mixing of liquid Cu-Fe-Hf alloys at 1873 K

Energy Technology Data Exchange (ETDEWEB)

Agraval, Pavel; Turchanin, Mikhail [Donbass State Engineering Academy, Kramatorsk (Ukraine). Metallurgical Dept.; Dreval, Liya [Donbass State Engineering Academy, Kramatorsk (Ukraine). Metallurgical Dept.; Materials Science International Services GmbH (MSI), Stuttgart (Germany)

2016-12-15

In the ternary Cu-Fe-Hf system, the mixing enthalpies of liquid alloys were investigated at 1873 K using a high-temperature isoperibolic calorimeter. The experiments were performed along the sections x{sub Cu}/x{sub Fe} = 3/1, 1/1 at x{sub Hf} = 0-0.47 and along the section x{sub Cu}/x{sub Fe} = 1/3 at x{sub Hf} = 0-0.13. The limiting partial enthalpies of mixing of undercooled liquid hafnium in liquid Cu-Fe alloys, Δ{sub mix} anti H{sub Hf}{sup ∞}, are (-122 ± 9) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 3/1), (-106 ± 9) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 1/1), and (-105 ± 2) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 1/3). In the investigated composition range, the integral mixing enthalpies are sign-changing. For the integral mixing enthalpy, an analytical expression was obtained by the least squares fit of the experimental results using the Redlich-Kister-Muggianu polynomial.

Determinations of enthalpy and partial molar enthalpy in the alloys Bi–Cd–Ga–In–Zn, Bi–Cd–Ga–Zn and Au–Cu–Sn

International Nuclear Information System (INIS)

Arslan, Hüseyin

2015-01-01

In the present study, the relations of thermodynamic associated with Chou's general solution model (GSM), the models of Muggianu and Toop have been used in order to calculate the mixing enthalpy and partial molar mixing enthalpy of mixing of Bi–Cd–Ga–In–Zn, Bi–Cd–Ga–Zn with equimolar section at a temperature of 730 K and Au–Cu–Sn with the section x Au /x Cu = 1/1 on the entire molar fraction range as a function of alloy composition at a temperature of 900 K. Some negativities are reported in the selected alloys mentioned above, particularly at high temperatures for the human health as well as difficulties in experimental measurement and high costs. Moreover, aim of us is to close the current article gap seen in the literature. In order to close the current gap seen in the literature, the article on the thermodynamic properties of the Bi–Cd–Ga–In–Zn alloys are presented in this study. - Highlights: • Thermodynamic properties of alloys in the study in given conditions were treated. • The activity of Bi seen in all models shows greatly positive deviation from ideality. • The enthalpy of Sn shows small negative values in x Au /x Cu = 1 at 900 K. • The activity of Sn shows negative deviation from ideality in the same conditions

Enthalpy-entropy compensation and the isokinetic temperature in ...

Indian Academy of Sciences (India)

Enthalpy-entropy compensation supposes that differences in activation enthalpy delta-H-++ for different reactions (or, typically inbiochemistry, the same reaction catalysed by enzymes obtained from different species) may be compensated for bydifferences in activation entropy delta-S-++. At the isokinetic temperature the ...

Enthalpy of solution of rubidium nitrate in water

International Nuclear Information System (INIS)

Weintraub, R.; Apelblat, A.; Tamir, A.

1984-01-01

Molar enthalpies of solution of RbNO 3 in water at 298.15 K were measured in an LKB calorimeter. The molar enthalpies of solution extrapolated to infinite solution are: (36788 +- 30)J. mol -1 (Alfa) and (36539 +- 52)J.mol -1 (Aldrich). (author)

Vapor pressure and enthalpy of vaporization of linear aliphatic alkanediamines

International Nuclear Information System (INIS)

Pozdeev, Vasiliy A.; Verevkin, Sergey P.

2011-01-01

Highlights: → We measured vapor pressure of diamines H 2 N-(CH 2 ) n -NH 2 with n = 3 to 12. → Vaporization enthalpies at 298 K were derived. → We examined consistency of new and available in the literature data. → Enthalpies of vaporization show linear dependence on numbers n. → Enthalpies of vaporization correlate linearly with Kovat's indices. - Abstract: Vapor pressures and the molar enthalpies of vaporization of the linear aliphatic alkanediamines H 2 N-(CH 2 ) n -NH 2 with n = (3 to 12) have been determined using the transpiration method. A linear correlation of enthalpies of vaporization (at T = 298.15 K) of the alkanediamines with the number n and with the Kovat's indices has been found, proving the internal consistency of the measured data.

[Enthalpy stabilization of chicken egg lysozyme in aqueous dimethylsulfoxide solutions].

Science.gov (United States)

Kovrigin, E L; Kirkitadze, M D; Potekhin, S A

1996-01-01

Scanning microcalorimetry data have been used to plot the dependences of the denaturation enthalpy of hen egg lysozyme on dimethylsulfoxide concentration at fixed temperatures. It has been shown that at dimethylsulfoxide concentrations below 40% (v/v) the enthalpy does not depend on pH of the medium. An increase of dimethylsulfoxide concentrations in this range leads to a linear growth of enthalpy. The rate of enthalpy growth decreases with the temperature increase. The denaturation enthalpy begins to considerably depend on pH at dimethylsulfoxide concentrations more than 40%. Spectroscopy data indicate that conformational changes occur in the protein in this range of concentrations already at room temperature, whereas according to scanning microcalorimetry, they take place at much higher temperatures. This difference is probably due to a decrease of the real temperature of protein melting below room temperature and a very inhibited character of the denaturational transition. This results in a decrease of calorimetric enthalpy at acidic pH owing to incomplete protein renaturation upon calorimeter cooling to the starting point.

Accounting for apparent deviations between calorimetric and van't Hoff enthalpies.

Science.gov (United States)

Kantonen, Samuel A; Henriksen, Niel M; Gilson, Michael K

2018-03-01

In theory, binding enthalpies directly obtained from calorimetry (such as ITC) and the temperature dependence of the binding free energy (van't Hoff method) should agree. However, previous studies have often found them to be discrepant. Experimental binding enthalpies (both calorimetric and van't Hoff) are obtained for two host-guest pairs using ITC, and the discrepancy between the two enthalpies is examined. Modeling of artificial ITC data is also used to examine how different sources of error propagate to both types of binding enthalpies. For the host-guest pairs examined here, good agreement, to within about 0.4kcal/mol, is obtained between the two enthalpies. Additionally, using artificial data, we find that different sources of error propagate to either enthalpy uniquely, with concentration error and heat error propagating primarily to calorimetric and van't Hoff enthalpies, respectively. With modern calorimeters, good agreement between van't Hoff and calorimetric enthalpies should be achievable, barring issues due to non-ideality or unanticipated measurement pathologies. Indeed, disagreement between the two can serve as a flag for error-prone datasets. A review of the underlying theory supports the expectation that these two quantities should be in agreement. We address and arguably resolve long-standing questions regarding the relationship between calorimetric and van't Hoff enthalpies. In addition, we show that comparison of these two quantities can be used as an internal consistency check of a calorimetry study. Copyright © 2017 Elsevier B.V. All rights reserved.

Standard enthalpies of formation of uranium compounds

International Nuclear Information System (INIS)

Cordfunke, E.H.P.; Ouweltjes, W.

1977-01-01

Enthalpies of solution of β-UO 2 SO 4 and α-UO 2 SeO 4 in H 2 SO 4 (aq) and of UO 2 SeO 3 in H 2 SO 4 (aq) + Ce(SO 4 ) 2 have been measured calorimetrically. Together with measurements of the enthalpy of solution of γ-UO 3 in these solvents, the standard enthalpies of formation of anhydrous β-UO 2 SO 4 , α-UO 2 SeO 4 , and UO 2 SeO 3 have been derived. The results obtained are: ΔHsub(f) 0 (s, 298.15 K)/ kcalsub(th) mol -1 : β-UO 2 SO 4 , -(440.9 +- 0.2); α-UO 2 SeO 4 , -(367.9 +- 0.8); UO 2 SeO 3 , -(363.8 +- 0.2). (author)

Enthalpy of Formation of N ₂ H ₄ (Hydrazine) Revisited

Energy Technology Data Exchange (ETDEWEB)

Feller, David [Department; Bross, David H. [Chemical; Ruscic, Branko [Chemical; Computation

2017-08-02

In order to address the accuracy of the long-standing experimental enthalpy of formation of gas-phase hydrazine, fully confirmed in earlier versions of Active Thermochemical Tables (ATcT), the provenance of that value is re-examined in light of new high-end calculations of the Feller-Peterson-Dixon (FPD) variety. An overly optimistic determination of the vaporization enthalpy of hydrazine, which created an unrealistically strong connection between the gas phase thermochemistry and the calorimetric results defining the thermochemistry of liquid hydrazine was identified as the probable culprit. The new enthalpy of formation of gas-phase hydrazine, based on balancing all available knowledge, was determined to be 111.57 ± 0.47 kJ/mol at 0 K (97.41 kJ/mol at 298.15 K). Close agreement was found between the ATcT (even excluding the latest theoretical result) and FPD enthalpies.

Standard molar enthalpies of formation of nickel(II) {beta}-diketonates and monothio-{beta}-diketonates

Energy Technology Data Exchange (ETDEWEB)

Ribeiro da Silva, Manuel A.V. [Centro de Investigacao em Quimica, Departamento de Quimica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)]. E-mail: risilva@fc.up.pt; Santos, Luis M.N.B.F. [Centro de Investigacao em Quimica, Departamento de Quimica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Giera, Edward [Faculty of Chemistry, Wroclaw University, ul. F. Joliot-Curie 14, 50-383 Wroclaw (Poland)

2007-03-15

The standard (p{sup o}=0.1MPa) molar enthalpies of formation of the crystalline diaquobis(dibenzoylmethanate)nickel(II), Ni(dbm){sub 2}(H{sub 2}O){sub 2}, diaquobis(thenoyltrifluoroacetonate)nickel(II), Ni(ttfa){sub 2}(H{sub 2}O){sub 2} bis(monothiodibenzoylmethanate)nickel(II), Ni(dbmS){sub 2} and bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni(HttfaS){sub 2} were determined, at T=298.15K, by high precision solution-reaction calorimetry. The standard molar enthalpy of sublimation of the monothiothenoyltrifluoroacetone (HttfaS) complex was measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean nickel(II)-ligand molar dissociation enthalpies, (Ni-L), were derived. {delta}{sub f}H{sub m}{sup o}(cr)/(kJ.mol{sup -1})Diaquobis(dibenzoylmethanate)nickel(II), Ni(dbm){sub 2}(H{sub 2}O){sub 2}-993.3+/-3.8Diaquobis(thenoyltrifluoroacetonate)nickel(II), Ni(ttfa){sub 2}(H{sub 2}O){sub 2}-2452.0+/-8.3Bis(monothiodibenzoylmethanate)nickel(II), Ni(dbmS){sub 2}-42.1+/-5.9Bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni(ttfaS){sub 2}-1473.5+/-8.1.

Excess molar enthalpies for binary mixtures of different amines with water

International Nuclear Information System (INIS)

Zhang, Ruilei; Chen, Jian; Mi, Jianguo

2015-01-01

Highlights: • Isothermal excess molar enthalpies for binary mixtures of different amines with water. • The Redlich–Kister equation and the NRTL model was used to fit the experimental data. • The excess molar enthalpies were discussed with different structures of amines. - Abstract: The isothermal excess molar enthalpies for binary mixtures of different amines with water were measured with a C-80 Setaram calorimeter. The experimental results indicate that the excess molar enthalpy is related to the molecular structure. The experimental excess molar enthalpies were satisfactorily fitted with the Redlich–Kister equation. They were also used to test the suitability of the NRTL model, and the deviations are a little larger than the R–K equation

Immersion enthalpies of activated carbon cloths as physical chemistry characterization parameter

International Nuclear Information System (INIS)

Rodriguez, Giovanny; Giraldo, Liliana; Moreno Juan Carlos

2009-01-01

The immersion enthalpies of five activated carbon cloths in carbon, CCl 4 , H 2 O and NaOH and HCl 0.1 M solutions are determined. The surface area values of the cloths are between 243 and 848 m 2 g-1 and exhibit a linear relationship with the immersion enthalpies in CCl 4 . The immersion enthalpies of carbon cloths are between 5.49 and 42.3 Jg-1 for CCl 4 and 3.83 and 7.54 Jg-1 for H 2 O. The immersion enthalpies in the solutions are related to the contents of acidic and basic groups and find that in the first case to increase the immersion enthalpy in NaOH increases the total acidity. Hydrophobic factor is calculated from the immersion enthalpies in CCl 4 and H 2 O, that indicate the interaction with polar and a polar compounds, and also relates to pHPZC each sample.

Prediction of failure enthalpy and reliability of irradiated fuel rod under reactivity-initiated accidents by means of statistical approach

International Nuclear Information System (INIS)

Nam, Cheol; Choi, Byeong Kwon; Jeong, Yong Hwan; Jung, Youn Ho

2001-01-01

During the last decade, the failure behavior of high-burnup fuel rods under RIA has been an extensive concern since observations of fuel rod failures at low enthalpy. Of great importance is placed on failure prediction of fuel rod in the point of licensing criteria and safety in extending burnup achievement. To address the issue, a statistics-based methodology is introduced to predict failure probability of irradiated fuel rods. Based on RIA simulation results in literature, a failure enthalpy correlation for irradiated fuel rod is constructed as a function of oxide thickness, fuel burnup, and pulse width. From the failure enthalpy correlation, a single damage parameter, equivalent enthalpy, is defined to reflect the effects of the three primary factors as well as peak fuel enthalpy. Moreover, the failure distribution function with equivalent enthalpy is derived, applying a two-parameter Weibull statistical model. Using these equations, the sensitivity analysis is carried out to estimate the effects of burnup, corrosion, peak fuel enthalpy, pulse width and cladding materials used

Low-enthalpy geothermal resources for electricity production: A demand-side management study for intelligent communities

DEFF Research Database (Denmark)

Xydis, George A.; Nanaki, Evanthia A.; Koroneos, Christopher J.

2013-01-01

The geological conditions in Greece contributed to the creation of important low-enthalpy geothermal energy resources (LEGERs). The resources are divided into low, medium and high enthalpy, or temperature, based on criteria that are generally based on the energy content of the fluid. LEGERs...... and northern part of the country, as well as in many of the Aegean Islands. The aim of this work is to review the options for managing wind load by using low-enthalpy geothermal energy for electricity (through heat pump utilisation) according to the local energy demand....... are those sources of the hot water whose temperature is between 25 and 100°C, which are used for heating residences and in the agricultural or industrial sector. The investigation for the exploitation of low-enthalpy geothermal fluids, which began around 1980, intensified in the last two decades. The low...

The determination of the enthalpy of formation and the enthalpy increment of Cd0.5 Te0.5 by Calvet calorimetry

International Nuclear Information System (INIS)

Agarwal, R.; Venugopal, V.; Sood, D.D.

1993-01-01

In the present study the enthalpy of formation of Cd 0.5 Te 0.5 compound at 785 K were determined from the two elements by direct reaction calorimetry using two different types of set-ups. The enthalpy increment values were measured by drop technique in Calvet calorimetry. (author). 3 refs., 4 tabs

Engineering Model of High Pressure Moist Air

Directory of Open Access Journals (Sweden)

Hyhlík Tomáš

2017-01-01

Full Text Available The article deals with the moist air equation of state. There are equations of state discussed in the article, i.e. the model of an ideal mixture of ideal gases, the model of an ideal mixture of real gases and the model based on the virial equation of state. The evaluation of sound speed based on the ideal mixture concept is mentioned. The sound speed calculated by the model of an ideal mixture of ideal gases is compared with the sound speed calculated by using the model based on the concept of an ideal mixture of real gases. The comparison of enthalpy end entropy based on the model of an ideal mixture of ideal gases and the model of an ideal mixture of real gases is performed. It is shown that the model of an ideal mixture of real gases deviates from the model of an ideal mixture of ideal gases only in the case of high pressure. An impossibility of the definition of partial pressure in the mixture of real gases is discussed, where the virial equation of state is used.

Experimental study on mass transfer of contaminants through an enthalpy recovery unit with polymer membrane foils

DEFF Research Database (Denmark)

Nie, Jinzhe; Fang, Lei

2014-01-01

Laboratory experimental studies were conducted to investigate the mass transfer of contaminants through a total heat recovery unit with polymer membranes foils. The studies were conducted in twin climate chambers which simulated outdoor and indoor thermal climates. One manufacturd total heat...... chemical gases were used to simulate air contaminants. The concentrations of dosed contaminants in the supply and exhaust air upstream and downstream of the total heat recovery unit were measured with Multi-Gas Monitor Innova 1316 in real time. Experiment results showed that 5% to 9% of dosed contaminants...... could transfer from exhaust air to supply air through the enthalpy recovery unit. The mass transfer efficiency of contaminants was independent of the hygro-thermal differences between indoor and outdoor climate conditions. The mass transfer ratio of the chemical contaminants in the total heat recovery...

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C1 - C10

Science.gov (United States)

Acree, William; Chickos, James S.

2016-09-01

A compendium of phase change enthalpies published in 2010 is updated to include the period 1880-2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C1 to C10. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C11 to C192. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, and a protocol for doing so are briefly discussed.

Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

International Nuclear Information System (INIS)

Kubatko, K.; Helean, K.; Navrotsky, A.; Burns, P.C.

2005-01-01

The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO 2 ) 4 O(OH) 6 ](H 2 O) 5 , metaschoepite; β-UO 2 (OH) 2 ; CaUO 4 ; Ca(UO 2 ) 6 O 4 (OH) 6 (H 2 O) 8 , becquerelite; Ca(UO 2 ) 4 O 3 (OH) 4 (H 2 O) 2 ; Na(UO 2 )O(OH), clarkeite; Na 2 (UO 2 ) 6 O 4 (OH) 6 (H 2 O) 7 , the sodium analogue of compreignacite and Pb 3 (UO 2 ) 8 O 8 (OH) 6 (H 2 O) 2 , curite. The enthalpy of formation from the binary oxides, ΔH f-ox , at 298 K was calculated for each compound from the respective drop solution enthalpy, ΔH ds . The standard enthalpies of formation from the elements, ΔH f o , at 298 K are -1791.0 ± 3.2, -1536.2 ± 2.8, -2002.0 ± 3.2, -11389.2 ± 13.5, -6653.1 ± 13.8, -1724.7 ± 5.1, -10936.4 ± 14.5 and -13163.2 ± 34.4 kJ mol -1 , respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments

Determination of formation enthalpies of incongruently fusing compounds

Energy Technology Data Exchange (ETDEWEB)

Kesler, Ya.A.; Cheshnitskij, S.M.; Fotiev, A.A.; Tret' yakov, Yu.D.

1985-04-01

Using the method of drop-calorimetry i.e. drop into the calorimeter cell being at the specified temperature of the specimen thermostated at 298 K, for studying reactions of peritectic decomposition of compounds for determining their formation enthalpies is considered. The measurements have been performed at 973 K using high temperature double microcalorimeter. The values ..delta..H/sub 1/=(367.0 +- 2.8) kJ/mol and ..delta..H/sub 2/=)343.9 +- 3.1) kJ/mol are obtained as a result of two series of measurements (6 experiments in each). The advantage of the described technique consists in the fact that the value of enthalpy of compound formation is obtained as a result of direct calorimetric measurements while in the e.m.f. method this value is determined as a coefficient in the Gibbs energy temperature dependence. The method is simple and does not require much time (one measurement takes 30-40 min).

Determination of formation enthalpies of incongruently fusing compounds

International Nuclear Information System (INIS)

Kesler, Ya.A.; Cheshnitskij, S.M.; Fotiev, A.A.; Tret'yakov, Yu.D.

1985-01-01

Using the method of drop-calorimetry i.e. drop into the calorimeter cell being at the specified temperature of the specimen thermostated at 298 K, for studying reactions of peritectic decomposition of compounds for determining their formation enthalpies is considered. The measurements have been performed at 973 K using high temperature double microcalorimeter. The values ΔH 1 =(367.0+-2.8) kJ/mol and ΔH 2 =)343.9+-3.1) kJ/mol are obtained as a result of two series of measurements (6 experiments in each). The advantage of the described technique consists in the fact that the value of enthalpy of compound formation is obtained as a result of direct calorimetric measurements while in the e.m.f. method this value is determined as a coefficient in the Gibbs energy temperature dependence. The method is simple and does not require much time (one measurement takes 30-40 min)

An empirical equation for the enthalpy of vaporization of quantum liquids

International Nuclear Information System (INIS)

Kuz, Victor A.; Meyra, Ariel G.; Zarragoicoechea, Guillermo J.

2004-01-01

An empirical equation for the enthalpy of vaporization of quantum fluids is presented. Dimensionless analysis is used to define enthalpy of vaporization as a function of temperature with a standard deviation of about 1%. Experimental data represented in these variables show two different behaviours and exhibit different maximum values of the enthalpy of vaporization, one corresponding to fluids with a triple point and the other to fluids having a lambda point. None of the existing empirical equations are able to describe this fact. Also enthalpy of vaporization of helium-3, n-deuterium and n-tritium are estimated

Vapor pressure and enthalpy of vaporization of aliphatic propanediamines

International Nuclear Information System (INIS)

Verevkin, Sergey P.; Chernyak, Yury

2012-01-01

Highlights: ► We measured vapor pressure of four aliphatic 1,3-diamines. ► Vaporization enthalpies at 298 K were derived. ► We examined consistency of new and available data in the literature. ► A group-contribution method for prediction was developed. - Abstract: Vapor pressures of four aliphatic propanediamines including N-methyl-1,3-propanediamine (MPDA), N,N-dimethyl-1,3-propanediamine (DMPDA), N,N-diethyl-1,3-propanediamine (DEPDA) and N,N,N′,N′-tetramethyl-1,3-propanediamine (4MPDA) were measured using the transpiration method. The vapor pressures developed in this work and reported in the literature were used to derive molar enthalpy of vaporization values at the reference temperature 298.15 K. An internal consistency check of the enthalpy of vaporization was performed for the aliphatic propanediamines studied in this work. A group-contribution method was developed for the validation and prediction vaporization enthalpies of amines and diamines.

Investigations of Very High Enthalpy Geothermal Resources in Iceland.

Science.gov (United States)

Elders, W. A.; Fridleifsson, G. O.

2012-12-01

reservoir, without increasing its environmental foot print. If these efforts are successful, in future such very high enthalpy geothermal systems worldwide could become significant energy resources, where ever suitable young volcanic rocks occur, such as in the western USA, Hawaii, and Alaska.

Direct measurements of the enthalpy of solution of solid solute in supercritical fluids: study on the CO2-naphthalene system.

Science.gov (United States)

Zhang, X; Han, B; Zhang, J; Li, H; He, J; Yan, H

2001-10-01

A setup for a calorimeter for simultaneously measuring the solubility and the solution enthalpy of solid solutes in supercritical fluids (SCFs) has been established. The enthalpy of solution of naphthalene in supercritical CO2 was measured at 308.15 K in the pressure range from 8.0-11.0 MPa. It was found that the enthalpy of solution (deltaH) was negative in the pressure range from 8.0 to 9.5 MPa, and the absolute value decreased with increasing pressure. In this pressure range, the dissolution of the solute was enthalpy driven. However, the deltaH became positive at pressures higher than 9.5 MPa, and the dissolution was entropy driven. Monte Carlo simulation was performed to analyze the local structural environment of the solvated naphthalene molecules in supercritical CO2 under the experimental conditions for the calorimetric measurements. By combining the enthalpy data and the simulation results, it can be deduced that the energy level of CO2 in the high compressible region is higher than that at higher pressures, which results in the large negative enthalpy of solution and the larger degree of solvent-solute clustering in the high compressible region.

Determination of vaporization enthalpies of polychlorinated biphenyls by correlation gas chromatography.

Science.gov (United States)

Puri, S; Chickos, J S; Welsh, W J

2001-04-01

The vaporization enthalpies of 16 polychlorinated biphenyls have been determined by correlation gas chromatography. This study was prompted by the realization that the vaporization enthalpy of the standard compounds used in previous studies, octadecane and eicosane, were values measured at 340 and 362 K, respectively, rather than at 298 K. Adjustment to 298 K amounts to a 7-8 kJ/mol increment in the values. With the inclusion of this adjustment, vaporization enthalpies evaluated by correlation gas chromatography are in good agreement with the values determined previously in the literature. The present results are based on the vaporization enthalpies of several standards whose values are well established in the literature. The standards include a variety of n-alkanes and various chlorinated hydrocarbons. The vaporization enthalpies of PCBs increased with the number of chlorine atoms and were found to be larger for meta- and para-substituted polychlorinated biphenyls.

Integral enthalpy of mixing of the liquid ternary Au-Cu-Sn system

International Nuclear Information System (INIS)

Knott, S.; Li, Z.; Mikula, A.

2008-01-01

The integral enthalpy of mixing of the ternary Au-Cu-Sn has been determined with a Calvet type calorimeter at 6 different cross sections at 1273 K. The substitutional solution model of Redlich-Kister-Muggianu was used for a least square fit of the experimental data in order to get an analytical expression for the integral enthalpy of mixing. The ternary extrapolation models of Kohler, Muggianu and Toop were used to calculate the integral enthalpy of mixing and to compare measured and extrapolated values. Additional calculations of the integral enthalpy of mixing using the Chou model have been performed. With the calculated data, the iso-enthalpy lines have been determined using the Redlich-Kister-Muggianu model. A comparison of the data has been made

Enthalpies of formation of selected Co{sub 2}YZ Heusler compounds

Energy Technology Data Exchange (ETDEWEB)

Yin, Ming, E-mail: myin1@hawk.iit.edu; Chen, Song; Nash, Philip

2013-11-15

Highlights: •Enthalpies of formation of selected Co{sub 2}YZ were measured by drop calorimeters. •Enthalpy decreases as the Z element approaches the top right corner of the periodic table. •For the Y element, enthalpy increases on increasing the number of d electrons. •Result of L2{sub 1} structured compounds agrees with first principles data. •Lattice parameters and related phase relationships were consistent with literature data. -- Abstract: Standard enthalpies of formation at 298 K of selected ternary Co{sub 2}-based Heusler compounds Co{sub 2}YZ (Y = Fe, Hf, Mn, Ti, V, Zr; Z = Al, Ga, In, Si, Ge, Sn) were measured by high temperature direct synthesis calorimetry. The measured enthalpies of formation (in kJ/mole of atoms) of the L2{sub 1} compounds are: Co{sub 2}FeGa (−25.8 ± 2.6); Co{sub 2}FeSi (−38.4 ± 2.2); Co{sub 2}FeGe (−11.6 ± 2.1); Co{sub 2}MnGa (−30.1 ± 2.3); Co{sub 2}MnSi (−42.4 ± 1.2); Co{sub 2}MnGe (−31.6 ± 3.0); Co{sub 2}MnSn (−15.6 ± 2.8); Co{sub 2}TiAl (−55.0 ± 3.7); Co{sub 2}TiGa (−54.2 ± 2.6); Co{sub 2}TiSi (−61.4 ± 1.7); Co{sub 2}TiGe (−59.3 ± 3.8); Co{sub 2}TiSn (−38.4 ± 2.0); Co{sub 2}VGa (−28.4 ± 1.1) and for the B2 compounds: Co{sub 2}FeAl (−22.5 ± 2.5), Co{sub 2}MnAl (−27.6 ± 2.7). Values are compared with those from first principles calculation when available and the extended semi-empirical model of Miedema. Trends in enthalpy of formation with element atomic number are discussed. Lattice parameters of the compounds with L2{sub 1} structure are determined by X-ray diffraction analysis.

Gas phase enthalpies of formation of nitrobenzamides using combustion calorimetry and thermal analysis

International Nuclear Information System (INIS)

Ximello, Arturo; Flores, Henoc; Rojas, Aarón; Adriana Camarillo, E.; Patricia Amador, M.

2014-01-01

Graphical abstract: - Highlights: • Formation enthalpies of the nitrobenzamides were derived from combustion calorimetry. • Enthalpies of vaporisation and sublimation were calculated by thermogravimetry. • From gas phase enthalpies of formation the stability of the isomers is studied. • Stability of isomers is not driven by a steric hindrance between functional groups. - Abstract: The standard molar energies of combustion of 2-nitrobenzamide, 3-nitrobenzamide and 4-nitrobenzamide were determined with an isoperibolic, static-bomb, combustion calorimeter. From the combustion results, the standard molar enthalpies of combustion and formation for these compounds in the condensed phase at T = 298.15 K were derived. Subsequently, to determine the enthalpies of sublimation, the vapour pressure data as a function of the temperature for the compounds under investigation were estimated using thermogravimetry by applying Langmuir’s equation, and the enthalpies of vaporisation were derived. Standard enthalpies of fusion were measured by differential scanning calorimetry then added to those of vaporisation to obtain reliable results for the enthalpy of sublimation. From the combustion and sublimation data, the gas phase enthalpies of formation were determined to be (−138.9 ± 3.5) kJ · mol −1 , (−122.9 ± 2.9) kJ · mol −1 and (−108.5 ± 3.7) kJ · mol −1 for the ortho, meta and para isomers of nitrobenzamide, respectively. The meaning of these results with regard to the enthalpic stability of these molecular structures is discussed herein

Isothermogravimetric determination of the enthalpies of vaporization of 1-alkyl-3-methylimidazolium ionic liquids.

Science.gov (United States)

Luo, Huimin; Baker, Gary A; Dai, Sheng

2008-08-21

Vaporization enthalpies for two series of ionic liquids (ILs) composed of 1- n-alkyl-3-methylimidazolium cations, [Imm1+] (m=2, 3, 4, 6, 8, or 10), paired with either the bis(trifluoromethanesulfonyl)amide, [Tf2N-], or the bis(perfluoroethylsulfonyl)amide anion, [beti-], were determined using a simple, convenient, and highly reproducible thermogravimetric approach, and from these values, Hildebrand solubility parameters were estimated. Our results reveal two interesting and unanticipated outcomes: (i) methylation at the C2 position of [Imm1+] affords a significantly higher vaporization enthalpy; (ii) in all cases, the [beti-] anion served to lower the enthalpy of vaporization relative to [Tf2N-]. The widespread availability of the apparatus required for these measurements coupled with the ease of automation suggests the broad potential of this methodology for determining this critical parameter in a multitude of ILs.

Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

Energy Technology Data Exchange (ETDEWEB)

K. Kubatko; K. Helean; A. Navrotsky; P.C. Burns

2005-05-11

The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

Standard enthalpies of formation of selected Rh2YZ Heusler compounds

International Nuclear Information System (INIS)

Yin, Ming; Nash, Philip

2015-01-01

The standard enthalpies of formation (Δ f H°) of selected ternary Rh-based Rh 2 YZ (Y = Cu, Fe, Mn, Ni, Ru, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) compounds were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mol of atoms) are, for the Heusler compound Rh 2 MnSn (−40.1 ± 3.6), for the B2-structured compounds: Rh 2 FeAl (−48.5 ± 2.9); Rh 2 MnAl (−72.4 ± 2.7); Rh 2 MnGa (−55.3 ± 2.0); Rh 2 MnIn (−35.3 ± 1.9), for the tetragonal compounds: Rh 2 FeSn (−28.9 ± 1.3); Rh 2 TiAl (−97.6 ± 2.2); Rh 2 TiGa (−79.0 ± 1.8); Rh 2 TiSn (−74.7 ± 3.1). Values are compared with those from first principles calculations in published papers and the Open Quantum Materials Database (OQMD). Lattice parameters of these compounds are determined using X-ray diffraction analysis (XRD). Microstructures were characterized using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). - Highlights: • Standard enthalpies of formation of Rh 2 YZ were measured using a drop calorimeter. • Measured enthalpies agree with first principles data in general. • Lattice parameters and related phase relationships were consistent with literature data. • Rh 2 TiSn of tI8 structure were reported for the first time.

Predicting the enthalpies of melting and vaporization for pure components

Science.gov (United States)

Esina, Z. N.; Korchuganova, M. R.

2014-12-01

A mathematical model of the melting and vaporization enthalpies of organic components based on the theory of thermodynamic similarity is proposed. In this empirical model, the phase transition enthalpy for the homological series of n-alkanes, carboxylic acids, n-alcohols, glycols, and glycol ethers is presented as a function of the molecular mass, the number of carbon atoms in a molecule, and the normal transition temperature. The model also uses a critical or triple point temperature. It is shown that the results from predicting the melting and vaporization enthalpies enable the calculation of binary phase diagrams.

Standard molar enthalpies of formation and of sublimation of the terphenyl isomers

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Santos, Luis M.N.B.F.; Lima, Luis M. Spencer S.

2008-01-01

The standard (p 0 = 0.1 MPa) molar enthalpies of formation in the crystalline phases of ortho, meta and para-terphenyl isomers, at T = 298.15 K, were derived from the standard molar energies of combustion, measured by mini-bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure the dependence of the vapour pressure of the crystals with the temperature, thus deriving their standard molar enthalpies of sublimation by means of the Clausius-Clapeyron equation. Combining the standard molar enthalpies of formation and sublimation of the crystalline terphenyls, the standard molar enthalpies of formation in the gaseous state, at T = 298.15 K, were derived for the three isomers. Results are provided in a table. The results show small but detectable isomerization enthalpies between the terphenyls, indicating the following relative enthalpic stabilities: m- > p- ∼ o-terphenyl

Standard molar enthalpies of formation of three N-benzoylthiocarbamic-O-alkylesters

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Santos, Luis M.N.B.F.; Schroeder, Bernd; Dietze, Frank; Beyer, Lothar

2004-01-01

The standard (p 0 =0.1 MPa) molar enthalpies of combustion in oxygen of three crystalline N-benzoylthiocarbamic-O-alkylesters, PhCONHCSOR, R=Et (Hbtcee), n-Bu (Hbtcbe), n-Hex (Hbtche), were measured at T=298.15 K by rotating bomb calorimetry. The standard molar enthalpies of sublimation of the three compounds were measured using Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively

Enthalpies of vaporization of some acetylene peroxy derivatives of carboranes-12

International Nuclear Information System (INIS)

Dibrivnyj, V.N.; Pistun, Z.E.; Van-Chin-Syan, Yu.Ya.; Yuvchenko, A.P.; Zvereva, T.D.

1999-01-01

Temperature dependences of saturated vapor pressure and vaporization enthalpies of five acetylene peroxy derivatives of carboranes-12 are determined by the Knudsen effusion method. Enthalpies and melting points of crystals, as well as temperatures of liquid compounds decomposition start are determined by the method of differential scanning calorimetry. Comparison of evaporation enthalpies determined in the study confirms the conclusions on non-additive character of intermolecular interaction in carboranes and their derivatives, which have been made previously [ru

The Calculation of Standard Enthalpies of Formation of Alkanes: Illustrating Molecular Mechanics and Spreadsheet Programs

Science.gov (United States)

Hawk, Eric Leigh

1999-02-01

How group increment methods may be used to predict standard enthalpies of formation of alkanes is outlined as an undergraduate computational chemistry experiment. The experiment requires input and output data sets. Although users may create their own data sets, both sets are provided. The input data set contains experimentally determined gas-phase standard enthalpies of formation and calculated steric energies for 10 alkanes. The steric energy for an alkane is calculated via a Molecular Mechanics approach employing Allinger's MM3 force field. Linear regression analysis on data contained in the input data set generates the coefficients that are used with the output data set to calculate standard enthalpies of formation for 15 alkanes. The average absolute error for the calculated standard enthalpies of formation is 1.22 kcal/mol. The experiment is highly suited to those interested in incorporating more computational chemistry in their curricula. In this regard, it is ideally suited for a physical chemistry laboratory, but it may be used in an organic chemistry course as well.

A new method for the determination of vaporization enthalpies of ionic liquids at low temperatures.

Science.gov (United States)

Verevkin, Sergey P; Zaitsau, Dzmitry H; Emelyanenko, Vladimir N; Heintz, Andreas

2011-11-10

A new method for the determination of vaporization enthalpies of extremely low volatile ILs has been developed using a newly constructed quartz crystal microbalance (QCM) vacuum setup. Because of the very high sensitivity of the QCM it has been possible to reduce the average temperature of the vaporization studies by approximately 100 K in comparison to other conventional techniques. The physical basis of the evaluation procedure has been developed and test measurements have been performed with the common ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C(2)mim][NTf(2)] extending the range of measuring vaporization enthalpies down to 363 K. The results obtained for [C(2)mim][NTf(2)] have been tested for thermodynamic consistency by comparison with data already available at higher temperatures. Comparison of the temperature-dependent vaporization enthalpy data taken from the literature show only acceptable agreement with the heat capacity difference of -40 J K(-1) mol(-1). The method developed in this work opens also a new way to obtain reliable values of vaporization enthalpies of thermally unstable ionic liquids.

Enthalpy changes when passing from simple to complex perovskite-like oxides

International Nuclear Information System (INIS)

Reznitskij, L.A.

1999-01-01

Formation enthalpies of complex perovskite-like oxides and their hexagonal analogs of the composition: Ba 2 ReFeO 6 , Sr 2 ReFeO 6 , Sr 2 ReMnO 6 , Ca 2 ReMnO 6 , Sr 2 WCrO 6 , Sr 2 MoCrO 6 , Ca 2 MoCrO 6 , Ca 2 WCrO 6 , Ba 3 Fe 2 ReO 9 , Ba 3 Cr 2 ReO 9 , Ba 2 RhTaO 6 and B 2 ScIrO 6 from simple oxides were calculated by approximate method using enthalpies of the cations coordination change in oxygen medium. The conclusion was made that enthalpy stabilization of the oxide with regard to simple oxides is mainly determined by the change in enthalpies of alkaline earth metal cations [ru

A combined experimental and computational investigation of excess molar enthalpies of (nitrobenzene + alkanol) mixtures

International Nuclear Information System (INIS)

Neyband, Razieh Sadat; Zarei, Hosseinali

2015-01-01

Highlights: • Excess molar enthalpies for the binary mixtures of nitrobenzene + alkanols mixtures were measured. • The infinite dilution excess partial molar enthalpies were calculated using the ab initio methods. • The PCM calculations were performed. • The computed excess partial molar enthalpies at infinite dilution were compared to experimental results. - Abstract: Excess molar enthalpies (H m E ) for the binary mixtures of {(nitrobenzene + ethanol), 1-propanol, 2-propanol, 1-butanol and 2-butanol} have been measured over the entire composition range at ambient pressure (81.5 kPa) and temperature 298 K using a Parr 1455 solution calorimeter. From the experimental results, the excess partial molar enthalpies (H i E ) and excess partial molar enthalpies at infinite dilution (H i E,∞ ) were calculated. The excess molar enthalpies (H m E ) are positive for all {nitrobenzene (1) + alkanol (2)} mixtures over the entire composition range. A state-of-the-art computational strategy for the evaluation of excess partial molar enthalpies at infinite dilution was followed at the M05-2X/6-311++G ∗∗ level of theory with the PCM model. The experimental excess partial molar enthalpies at infinite dilution have been compared to the computational data of the ab initio in liquid phase. Integrated experimental and computational results help to clarify the nature of the intermolecular interactions in {nitrobenzene (1) + alkanol (2)} mixtures. The experimental and computational work which was done in this study complements and extends the general research on the computation of excess partial molar enthalpy at infinite dilution of binary mixtures

Enthalpy of formation of titanium diboride

International Nuclear Information System (INIS)

Akhachinskij, V.V.; Chirin, N.A.

1975-01-01

The values given in the literature for the enthalpy of the formation of titanium diboride, as obtained experimentally and by theoretical estimation, range between -32 and -74.4 kcal/mol. In this paper the authors use the method of direct synthesis from elements in a Calvet calorimeter to determine the enthalpy of formation, ΔHsub(f) 0 , sub(298), of titanium diboride with the composition Tisub(1.000+-0.002)Bsub(2.056+-0.006)Csub(0.009)Nsub(0.003), which was found to be -76.78+-0.83 kcal/mol. They calculate that ΔHsub(f,298) (TiBsub(2.056)=-76.14+-0.85 kcal/mol. The procedure employed makes it possible to carry out the titanium diboride synthesis reaction with the calorimeter at room temperature

What is the enthalpy of formation of pyrazine-2-carboxylic acid?

International Nuclear Information System (INIS)

Miranda, Margarida S.; Duarte, Darío J.R.; Liebman, Joel F.

2016-01-01

There are two contemporary conflicting, indeed, incompatible determinations of measurements of the enthalpies of combustion and of formation of pyrazine-2-carboxylic acid in the literature, (−2268.0 ± 0.9 and −271.2 ± 1.1 kJ · mol −1 ) and (−2211.4 ± 0.9 and −327.8 ± 1.1 kJ · mol −1 ). The current paper discusses these two sets of values and from the use of a measurement of the enthalpy of sublimation, a newly evaluated enthalpy of formation of pyrazine itself, and of the quantum chemical calculations at the G3(MP2)//B3LYP level, the former results are accepted and the derived gas phase enthalpy of formation, −(167.6 ± 3.1) kJ · mol −1 , suggested.

Low-enthalpy geothermal resources for electricity production: A demand-side management study for intelligent communities

International Nuclear Information System (INIS)

Xydis, George A.; Nanaki, Evanthia A.; Koroneos, Christopher J.

2013-01-01

The geological conditions in Greece contributed to the creation of important low-enthalpy geothermal energy resources (LEGERs). The resources are divided into low, medium and high enthalpy, or temperature, based on criteria that are generally based on the energy content of the fluid. LEGERs are those sources of the hot water whose temperature is between 25 and 100 °C, which are used for heating residences and in the agricultural or industrial sector. The investigation for the exploitation of low-enthalpy geothermal fluids, which began around 1980, intensified in the last two decades. The low-enthalpy geothermal potential in Greece is rather significant as most of the geothermal fields have been found in regions with favourable developmental conditions, and it seems that they do not present serious environmental or technical exploitation problems. LEGER areas are abundant in Greece, mainly in the eastern and northern part of the country, as well as in many of the Aegean Islands. The aim of this work is to review the options for managing wind load by using low-enthalpy geothermal energy for electricity (through heat pump utilisation) according to the local energy demand. -- Highlights: •Approximately 45.43 GWh per year of electricity can be covered from low-enthalpy geothermal energy resources (LEGERs). •In particular, 10% of the electricity demand can be covered from the LEGER N. Kessani (NK). •The needs for LEGER contribution were increased when wind turbine (WT) production was low. •In winter, where there is abundance of wind, LEGER can be used mostly for heating. •During summer, LEGER can assist more in electricity when heating is not needed

Improved algorithm based on equivalent enthalpy drop method of pressurized water reactor nuclear steam turbine

International Nuclear Information System (INIS)

Wang Hu; Qi Guangcai; Li Shaohua; Li Changjian

2011-01-01

Because it is difficulty to accurately determine the extraction steam turbine enthalpy and the exhaust enthalpy, the calculated result from the conventional equivalent enthalpy drop method of PWR nuclear steam turbine is not accurate. This paper presents the improved algorithm on the equivalent enthalpy drop method of PWR nuclear steam turbine to solve this problem and takes the secondary circuit thermal system calculation of 1000 MW PWR as an example. The results show that, comparing with the design value, the error of actual thermal efficiency of the steam turbine cycle obtained by the improved algorithm is within the allowable range. Since the improved method is based on the isentropic expansion process, the extraction steam turbine enthalpy and the exhaust enthalpy can be determined accurately, which is more reasonable and accurate compared to the traditional equivalent enthalpy drop method. (authors)

Enthalpy of Vaporization by Gas Chromatography: A Physical Chemistry Experiment

Science.gov (United States)

Ellison, Herbert R.

2005-01-01

An experiment is conducted to measure the enthalpy of vaporization of volatile compounds like methylene chloride, carbon tetrachloride, and others by using gas chromatography. This physical property was measured using a very tiny quantity of sample revealing that it is possible to measure the enthalpies of two or more compounds at the same time.

Aerosol volatility and enthalpy of sublimation of carboxylic acids.

Science.gov (United States)

Salo, Kent; Jonsson, Asa M; Andersson, Patrik U; Hallquist, Mattias

2010-04-08

The enthalpy of sublimation has been determined for nine carboxylic acids, two cyclic (pinonic and pinic acid) and seven straight-chain dicarboxylic acids (C(4) to C(10)). The enthalpy of sublimation was determined from volatility measurements of nano aerosol particles using a volatility tandem differential mobility analyzer (VTDMA) set-up. Compared to the previous use of a VTDMA, this novel method gives enthalpy of sublimation determined over an extended temperature range (DeltaT approximately 40 K). The determined enthalpy of sublimation for the straight-chain dicarboxylic acids ranged from 96 to 161 kJ mol(-1), and the calculated vapor pressures at 298 K are in the range of 10(-6)-10(-3) Pa. These values indicate that dicarboxylic acids can take part in gas-to-particle partitioning at ambient conditions and may contribute to atmospheric nucleation, even though homogeneous nucleation is unlikely. To obtain consistent results, some experimental complications in producing nanosized crystalline aerosol particles were addressed. It was demonstrated that pinonic acid "used as received" needed a further purification step before being suspended as a nanoparticle aerosol. Furthermore, it was noted from distinct differences in thermal properties that aerosols generated from pimelic acid solutions gave two types of particles. These two types were attributed to crystalline and amorphous configurations, and based on measured thermal properties, the enthalpy of vaporization was 127 kJ mol(-1) and that of sublimation was 161 kJ mol(-1). This paper describes a new method that is complementary to other similar methods and provides an extension of existing experimental data on physical properties of atmospherically relevant compounds.

Enthalpy and void distributions in subchannels of PHWR fuel bundles

Energy Technology Data Exchange (ETDEWEB)

Park, J W; Choi, H; Rhee, B W [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1999-12-31

Two different types of the CANDU fuel bundles have been modeled for the ASSERT-IV code subchannel analysis. From calculated values of mixture enthalpy and void fraction distribution in the fuel bundles, it is found that net buoyancy effect is pronounced in the central region of the DUPIC fuel bundle when compared with the standard CANDU fuel bundle. It is also found that the central region of the DUPIC fuel bundle can be cooled more efficiently than that of the standard fuel bundle. From the calculated mixture enthalpy distribution at the exit of the fuel channel, it is found that the mixture enthalpy and void fraction can be highest in the peripheral region of the DUPIC fuel bundle. On the other hand, the enthalpy and the void fraction were found to be highest in the central region of the standard CANDU fuel bundle at the exit of the fuel channel. This study shows that the subchannel analysis is very useful in assessing thermal behavior of the fuel bundle that could be used in CANDU reactors. 10 refs., 4 figs., 2 tabs. (Author)

Enthalpy and void distributions in subchannels of PHWR fuel bundles

Energy Technology Data Exchange (ETDEWEB)

Park, J. W.; Choi, H.; Rhee, B. W. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1998-12-31

Two different types of the CANDU fuel bundles have been modeled for the ASSERT-IV code subchannel analysis. From calculated values of mixture enthalpy and void fraction distribution in the fuel bundles, it is found that net buoyancy effect is pronounced in the central region of the DUPIC fuel bundle when compared with the standard CANDU fuel bundle. It is also found that the central region of the DUPIC fuel bundle can be cooled more efficiently than that of the standard fuel bundle. From the calculated mixture enthalpy distribution at the exit of the fuel channel, it is found that the mixture enthalpy and void fraction can be highest in the peripheral region of the DUPIC fuel bundle. On the other hand, the enthalpy and the void fraction were found to be highest in the central region of the standard CANDU fuel bundle at the exit of the fuel channel. This study shows that the subchannel analysis is very useful in assessing thermal behavior of the fuel bundle that could be used in CANDU reactors. 10 refs., 4 figs., 2 tabs. (Author)

Molar volume, excess enthalpy, and Prigogine-Defay ratio of some silicate glasses with different (P,T) histories.

Science.gov (United States)

Wondraczek, Lothar; Behrens, Harald

2007-10-21

Structural relaxation in silicate glasses with different (p,T) histories was experimentally examined by differential scanning calorimetry and measurements of molar volume under ambient pressure. Temperature and pressure-dependent rates of changes in molar volume and generation of excess enthalpy were determined for sodium trisilicate, soda lime silicate, and sodium borosilicate (NBS) compositions. From the derived data, Prigogine-Defay ratios are calculated and discussed. Changes of excess enthalpy are governed mainly by changes in short-range structure, as is shown for NBS where boron coordination is highly sensitive to pressure. For all three glasses, it is shown how the relaxation functions that underlie volume, enthalpy, and structural relaxation decouple for changes in cooling rates and pressure of freezing, respectively. The magnitude of the divergence between enthalpy and volume may be related to differences in structural sensitivity to changes in the (p,V,T,t) space on different length scales. The findings suggest that the Prigogine-Defay ratio is related to the magnitude of the discussed decoupling effect.

Vapour pressure and enthalpy of vaporization of aliphatic poly-amines

International Nuclear Information System (INIS)

Efimova, Anastasia A.; Emel'yanenko, Vladimir N.; Verevkin, Sergey P.; Chernyak, Yury

2010-01-01

Molar enthalpies of vaporization of aliphatic poly-amines: 1,4-dimethylpiperazine [106-58-1], 1-(2-aminoethyl)-piperazine, [140-31-8], 1-(2-aminoethyl)-4-methyl-piperazine [934-98-5], and triethylenetetramine [112-24-3] were obtained from the temperature dependence of the vapour pressure measured by the transpiration method. A large number of the primary experimental results on temperature dependences of vapour pressures of the parent compounds have been collected from the literature and have been treated uniformly in order to derive vaporization enthalpies of poly-amines at the reference temperature 298.15 K. An internal consistency check was performed on enthalpy of vaporization values for poly-amines studied in this work.

The excess enthalpies of liquid Ge-Pb-Te alloys

International Nuclear Information System (INIS)

Blachnik, R.; Binder, J.; Schlieper, A.

1997-01-01

The excess enthalpies of liquid alloys in the ternary system Ge-Pb-Te were determined at 1210 K in a heat flow calorimeter for five sections Ge y Pb 1-y -Te with y = 0.2, 0.4, 0.5, 0.6 and 0.8 and at 1153 K for Ge 0.5 Pb 0.5 -Te. The enthalpy surface in the ternary system is determined by a valley of exothermic minima, stretching from an exothermic minimum at the composition GeTe to one at the composition PbTe in the respective binaries. The excess enthalpies in the limiting metallic binary were adapted with the Redlich-Kister formalism. For the description of the thermodynamic functions in the ternary system the equation of Bonnier was taken using ternary coefficients. The calculated curves are in good agreement with the experimental data. (orig.)

A proposal to investigate higher enthalpy geothermal systems in the USA

Science.gov (United States)

Elders, W. A.

2013-12-01

After more than 50 years of development only ~3,400 MWe of electric power is currently being produced from geothermal resources in the USA. That is only about 0.33% of the country's total installed electrical capacity. In spite of the large demonstrated potential of geothermal resources, only ~2,500 MWe of new geothermal electrical capacity are under development, and the growth rate of this environmentally benign energy resource is overshadowed by the rapid increase in the installed capacity of wind and solar energy. Most of the new geothermal developments in the USA involve relatively small, moderate-temperature, geothermal systems. In contrast, development of higher enthalpy geothermal systems for power production has obvious advantages; specifically higher temperatures yield higher power outputs per well so that fewer wells are needed, leading to smaller environmental footprints for a given size of power plant. Disadvantages include that the fact that locations of suitable geothermal systems are restricted to young volcanic terrains, production of very high enthalpy fluids usually requires drilling deeper wells and may require enhanced geothermal (EGS) technology, and drilling deep into hot hostile environments is technologically challenging. However the potential for very favorable economic returns suggests that the USA should begin developing such a program. One approach to mitigating the cost issue is to form a consortium of industry, government and academia to share the costs and broaden the scope an investigation. An excellent example of such a collaboration is the Iceland Deep Drilling Project (IDDP) which is investigating the economic feasibility of producing electricity from supercritical geothermal reservoirs. This industry-government consortium planned to drill a deep well in the volcanic caldera of Krafla in NE Iceland. However drilling had to be terminated at 2.1 km depth when 900°C rhyolite magma flowed into the well. The resultant well was highly

Enthalpy of sublimation/vaporization of trans-cyclohexyl-1,4-diamine and cis-cyclohexyl-1,2-diamine

International Nuclear Information System (INIS)

Tome, Luciana I.N.; Rosado, Mario T.S.; Nunes, Sandra C.C.; Maria, Teresa M.R.; Canotilho, Joao; Eusebio, M. Ermelinda S.

2007-01-01

The molar enthalpy of sublimation, Δ cr g H m 0 , of trans-cyclohexyl-1,4-diamine and the molar enthalpy of vaporization, Δ l g H m 0 , of cis-cyclohexyl-1,2-diamine, at the temperature 298.15 K, were determined by calorimetry. Δ cr g H m 0 (T=298.15K)=(105.0±0.8)kJ.mol -1 was obtained for the trans-isomer and Δ l g H m 0 (T=298.15K)=(62.2±1.0)kJ.mol -1 for the cis form. The molar enthalpy of fusion of the first compound, at T = 342.1 K, was determined by differential scanning calorimetry. The molar enthalpy of vaporization of the 1,4-isomer was estimated by combining the value of the enthalpy of sublimation with that of the enthalpy of fusion. The values obtained for molar standard enthalpy of vaporization and those available for the enthalpy of the diamines in the gas state were used to calculate the difference between the enthalpies of both compounds in the liquid state

Experimental Determination of the Formation Enthalpy of Calcium Cobaltate from Sol–Gel Precursors

DEFF Research Database (Denmark)

Holgate, Tim C.; Wu, NingYu; Van Nong, Ngo

2017-01-01

Calcium cobaltate (Ca3Co4O9) remains one of the most promising p-type oxide materials for high-temperature thermoelectric energy conversion. While much progress has been made in refining our understanding of the unique structure of the material, as well as optimization of the transport properties...... as observations of its decomposition into the Ca3Co2O6 phase. The reaction enthalpy of forming Ca3Co4O9 from CaCO3 and Co3O4 sol–gel precursors was determined to be +284 (±2%) kJ/mol, leading to a standard enthalpy of Ca3Co4O9 of −3307 (±3.5%) kJ/mol....

Standard molar enthalpies of formation of three methyl-pyrazole derivatives

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Cabral, Joana I.T.A.

2012-01-01

Highlights: ► Combustion calorimetry was used to determine Δ f H m ∘ (cr) of methyl-pyrazole derivatives. ► Vapour pressures were determined by the Knudsen mass-loss effusion technique. ► Gas-phase Δ f H m ∘ of the studied compounds have been derived. - Abstract: The standard (p ° = 0.1 MPa) molar enthalpies of formation of the crystalline 3-methyl-1-pyrazolecarboxamide; 3-methyl-3-pyrazoline-5-one; and 4-methyl-2-pyrazoline-5-one were derived from the standard massic energies of combustion, in oxygen, to yield CO 2 (g), H 2 O (l) and N 2 (g), at T = 298.15 K, measured by static bomb combustion calorimetry. The standard molar enthalpies of sublimation were calculated from the variation of the vapour pressures of each compound with temperature, measured by the Knudsen effusion technique. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the pyrazole derivatives, in the gaseous phase, at T = 298.15 K. The derived standard molar enthalpies of formation, in gaseous state, are analyzed in terms of enthalpic increments and interpreted in terms of molecular structure.

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds and Ionic Liquids. Sublimation, Vaporization, and Fusion Enthalpies from 1880 to 2015. Part 2. C11-C192

Science.gov (United States)

Acree, William; Chickos, James S.

2017-03-01

The second part of this compendium concludes with a collection of phase change enthalpies of organic molecules inclusive of C11-C192 reported over the period 1880-2015. Also included are phase change enthalpies including fusion, vaporization, and sublimation enthalpies for organometallic, ionic liquids, and a few inorganic compounds. Paper I of this compendium, published separately, includes organic compounds from C1 to C10 and describes a group additivity method for evaluating solid, liquid, and gas phase heat capacities as well as temperature adjustments of phase changes. Paper II of this compendium also includes an updated version of a group additivity method for evaluating total phase change entropies which together with the fusion temperature can be useful in estimating total phase change enthalpies. Other uses include application in identifying potential substances that either form liquid or plastic crystals or exhibit additional phase changes such as undetected solid-solid transitions or behave anisotropically in the liquid state.

Specification and comparative calculation of enthalpies and Gibbs formation energies of anhydrous lanthanide nitrates

International Nuclear Information System (INIS)

Del' Pino, Kh.; Chukurov, P.M.; Drakin, S.I.

1980-01-01

Analyzed are the results of experimental depermination of formation enthalpies of waterless nitrates of lanthane cerium, praseodymium, neodymium and samarium. Using method of comparative calculation computed are enthalpies of formation of waterless lanthanide and yttrium nitrates. Calculated values of enthalpies and Gibbs energies of waterless lanthanide nitrate formation are tabulated

Effects of electric fields in polymerization on enthalpy of PMAA anhydridization

Energy Technology Data Exchange (ETDEWEB)

Chang Zhenqi; Liu Gang; Zhang Zhicheng

2004-02-19

PMAA (polymethacrylic acid) polymerized by {gamma}-irradiation in electric field forms six-membered cyclic anhydride during heating process and the enthalpy of PMAA anhydridization was determined by DSC. Why the endothermic peak of PMAA anhydridization in DSC curve between 200 and 300 deg. C appears is particularly explained by calculation. The relations between applied electric field and the enthalpy of PMAA anhydridization are studied. The results show that, with the increases of the intensity of electric field in polymerization, the enthalpy of PMAA forming anhydrides nonlinearly increase, which might be related to orientation of carboxylic acid groups of the PMAA in an electric field.

Formation enthalpies of Al–Fe–Zr–Nd system calculated by using geometric and Miedema's models

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lei [Department of Mathematics and Information Science, Guangxi College of Education, Nanning 530023 (China); Wang, Rongcheng; Tao, Xiaoma; Guo, Hui; Chen, Hongmei [College of Physical Science and Technology, Guangxi University, Nanning 530004 (China); Ouyang, Yifang, E-mail: ouyangyf@gxu.edu.cn [College of Physical Science and Technology, Guangxi University, Nanning 530004 (China)

2015-04-15

Formation enthalpy is important for the phase stability and amorphous forming ability of alloys. The formation enthalpies of Fe{sub 17}RE{sub 2} (RE=Ce, Pr, Nd, Gd and Er) obtained by Miedema's theory are in good agreement with those of the experiments. The dependence of formation enthalpy on concentration of Al for intermetallic (Al{sub x}Fe{sub 1−x}){sub 17}Nd{sub 2} have been calculated by Miedema's theory and the geometric model. The solid solubility of Al in (Al{sub x}Fe{sub 1−x}){sub 17}Nd{sub 2} is coincident with the concentration dependence of formation enthalpy. The mixing enthalpies of liquid alloys and formation enthalpies of alloys for Al–Fe–Zr–Nd system have been predicted. The calculated mixing enthalpy indicates that the adding of Fe or Nd decreases monotonously the magnitude of enthalpy. The formation enthalpies of Al–Fe–Zr–Nd system indicate that the shape of the enthalpy contour map changes when the content of Al is less than 50.0 at% and then it remains unchanged except the decrease of magnitude. The formation enthalpy of Al–Fe–Zr–Nd increases with the increase of Fe and/or Nd content. The negative formation enthalpy indicates that Al–Fe–Zr–Nd system has higher amorphous forming ability and wide amorphous forming range. The certain contents of Zr and/or Al are beneficial for the formation of Al–Fe–Zr–Nd intermetallics.

A correct enthalpy relationship as thermal comfort index for livestock.

Science.gov (United States)

Rodrigues, Valéria Cristina; da Silva, Iran José Oliveira; Vieira, Frederico Márcio Corrêa; Nascimento, Sheila Tavares

2011-05-01

Researchers working with thermal comfort have been using enthalpy to measure thermal energy inside rural facilities, establishing indicator values for many situations of thermal comfort and heat stress. This variable turned out to be helpful in analyzing thermal exchange in livestock systems. The animals are exposed to an environment which is decisive for the thermoregulatory process, and, consequently, the reactions reflect states of thermal comfort or heat stress, the last being responsable for problems of sanity, behavior and productivity. There are researchers using enthalpy as a qualitative indicator of thermal environment of livestock such as poultry, cattle and hogs in tropical regions. This preliminary work intends to check different enthalpy equations using information from classical thermodynamics, and proposes a direct equation as thermal comfort index for livestock systems.

Structure of metal β-diketonates and their enthalpies of vaporization

International Nuclear Information System (INIS)

Domrachev, G.A.; Sevast'yanov, V.G.; Zakharov, L.N.; Krasnodubskaya, S.V.; AN SSSR, Moscow. Inst. Obshchej i Neorganicheskoj Khimii)

1987-01-01

Using the method of additive schemes in combinaion with the structural estimation of the degree of screening of the central atom and other elements of β-diketonate molecule while analyzing the experimental enthalpies of vaporization, the contributions of separate fragments of complexes into the enthalpy of vaporization are found. It is shown that energies of intermolecular interaction in a condensed phase of monomeric metal β-diketonates with identical substituents do not depend on the central atom type. The enthalpies of dimer dissociation in a series of rare earth dipivaloylmethanates calculated. The proposed approach is advisable fo selecting forms of metal β-diketonates, the most suitable for the purposes of deep purificaion, which are characterized by maximum chemical and physico-chemical selectivity with respect to impurities, chemical inertness to equipment material, container, etc

Standard enthalpies of formation of selected Rh{sub 2}YZ Heusler compounds

Energy Technology Data Exchange (ETDEWEB)

Yin, Ming, E-mail: myin1@hawk.iit.edu; Nash, Philip

2015-11-25

The standard enthalpies of formation (Δ{sub f}H°) of selected ternary Rh-based Rh{sub 2}YZ (Y = Cu, Fe, Mn, Ni, Ru, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) compounds were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mol of atoms) are, for the Heusler compound Rh{sub 2}MnSn (−40.1 ± 3.6), for the B2-structured compounds: Rh{sub 2}FeAl (−48.5 ± 2.9); Rh{sub 2}MnAl (−72.4 ± 2.7); Rh{sub 2}MnGa (−55.3 ± 2.0); Rh{sub 2}MnIn (−35.3 ± 1.9), for the tetragonal compounds: Rh{sub 2}FeSn (−28.9 ± 1.3); Rh{sub 2}TiAl (−97.6 ± 2.2); Rh{sub 2}TiGa (−79.0 ± 1.8); Rh{sub 2}TiSn (−74.7 ± 3.1). Values are compared with those from first principles calculations in published papers and the Open Quantum Materials Database (OQMD). Lattice parameters of these compounds are determined using X-ray diffraction analysis (XRD). Microstructures were characterized using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). - Highlights: • Standard enthalpies of formation of Rh{sub 2}YZ were measured using a drop calorimeter. • Measured enthalpies agree with first principles data in general. • Lattice parameters and related phase relationships were consistent with literature data. • Rh{sub 2}TiSn of tI8 structure were reported for the first time.

Formation enthalpy of NiBe and Ni5Be21

International Nuclear Information System (INIS)

Ivanov, M.I.; Karpova, T.F.; Dalago, N.Yu.

1981-01-01

The method of dissolution calorimetry is used to determine standard enthalpies of NiBe and Ni 5 Be 21 formation, which are 84.8+-2.2 and (-669+-37)kJ/mol. The enthalpy values of NiBe and Ni 5 Be 21 at 331 K are shown to coincide (within the limits of errors of these values) with the values at the standard temperature of 298.15 K [ru

The enthalpies of formation of neutral and charged components of saturated vapor over europium dichloride

International Nuclear Information System (INIS)

Pogrebnoj, A.M.; Kudin, L.S.

2003-01-01

Composition of saturated vapor over europium dichloride was studied by the method of high-temperature mass spectrometry in the temperature range of 1154 - 1267 K. For neutral components of the vapor, represented by monomer and dimer molecules, partial pressures were determined. Enthalpies of sublimation of europium dichloride Δ s H 0 (298 K) as monomers (338 ± 9) and dimers (407 ± 20 kJ/mol) were calculated. Equilibrium constants of ion-molecular and ion-ionic reactions were measured, their enthalpies being ascertained. Enthalpies of formation of molecules and ions Δ f H 0 (298 K) were calculated: -486 ± 11 (EuCl 2 ), -1242 ± 22 (Eu 2 Cl 4 ), 1 ± 12 (Eu 2 Cl 2 + ), -347 ± 20 (Eu 2 Cl 3 + ), -1111 ± 42 (Eu 3 Cl 5 + ), -975 ± 20 (EuCl 3 - ), -1309 ± 17(EuCl 4 - ), -1734 ± 20 (Eu 2 Cl 5 - ) kJ/mol [ru

Enthalpy of sublimation/vaporization of trans-cyclohexyl-1,4-diamine and cis-cyclohexyl-1,2-diamine

OpenAIRE

Tomé, Luciana I. N.; Rosado, Mário T. S.; Nunes, Sandra C. C.; Maria, Teresa M. R.; Canotilho, João; Eusébio, M. Ermelinda S.

2007-01-01

The molar enthalpy of sublimation, , of trans-cyclohexyl-1,4-diamine and the molar enthalpy of vaporization, , of cis-cyclohexyl-1,2-diamine, at the temperature 298.15 K, were determined by calorimetry. was obtained for the trans-isomer and for the cis form. The molar enthalpy of fusion of the first compound, at T = 342.1 K, was determined by differential scanning calorimetry. The molar enthalpy of vaporization of the 1,4-isomer was estimated by combining the value of the enthalpy of sublimat...

Analysis of experimental routines of high enthalpy steam discharge in subcooled water

Energy Technology Data Exchange (ETDEWEB)

Pacheco, Rafael R., E-mail: Rafael.rade@ctmsp.mar.mil.br [Centro Tecnologico da Marinha em Sao Paulo (CTMSP), SP (Brazil); Andrade, Delvonei A., E-mail: delvonei@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2015-07-01

The discharge of high enthalpy steam through safety release valves out from pressurizers in PWR's needs to be condensed in order to allow the treatment of possibly present radwaste within. The Direct Contact Condensation is used in a relief tank to achieve the condensation. Care must be taken to avoid the bypass of the steam through the subcooled water, what would increase the peak of pressure and the necessity of structural reinforcement of the relief tank. An experiment to determine the optimal set up of the relief tank components and their characteristics (type of sprinkler, level of water, volume of tank, discharge direction, pressure in the pressurizer among others) was executed in 2000, in the CTE 150 facility, in CTMSP. In a total, 144 routines varying its components and characteristics were made, although no comprehensive analysis of its results were yet made, since the mass of data was too big to be readily analyzed. In order to comprehensively analyze it, a VBA program is being made to compile and graphically represent the mass of data. The current state of this program allowed conclusions over the peak pressure, adiabatic assumption of the experiment, and the quality of the steam generated due to the discharge. (author)

Analysis of experimental routines of high enthalpy steam discharge in subcooled water

International Nuclear Information System (INIS)

Pacheco, Rafael R.; Andrade, Delvonei A.

2015-01-01

The discharge of high enthalpy steam through safety release valves out from pressurizers in PWR's needs to be condensed in order to allow the treatment of possibly present radwaste within. The Direct Contact Condensation is used in a relief tank to achieve the condensation. Care must be taken to avoid the bypass of the steam through the subcooled water, what would increase the peak of pressure and the necessity of structural reinforcement of the relief tank. An experiment to determine the optimal set up of the relief tank components and their characteristics (type of sprinkler, level of water, volume of tank, discharge direction, pressure in the pressurizer among others) was executed in 2000, in the CTE 150 facility, in CTMSP. In a total, 144 routines varying its components and characteristics were made, although no comprehensive analysis of its results were yet made, since the mass of data was too big to be readily analyzed. In order to comprehensively analyze it, a VBA program is being made to compile and graphically represent the mass of data. The current state of this program allowed conclusions over the peak pressure, adiabatic assumption of the experiment, and the quality of the steam generated due to the discharge. (author)

Vaporization thermodynamics and enthalpy of formation of aluminum silicon carbide

International Nuclear Information System (INIS)

Behrens, R.G.; Rinehart, G.H.

1984-01-01

The vaporization thermodynamics of aluminum silicon carbide was investigated using Knudsen effusion mass spectrometry. Vaporization occurred incongruently to give Al(g), SiC(s), and graphite as reaction products. The vapor pressure of aluminum above (Al 4 SiC 4 + SiC + C) was measured using graphite effusion cells with orifice areas between 1.1 X 10 -2 and 3.9 X 10 -4 cm 2 . The vapor pressure of aluminum obtained between 1427 and 1784 K using an effusion cell with the smallest orifice area, 3.9 X 10 -4 cm 2 , is expressed as log p (Pa) = - (18567 + or - 86) (K/T) + (12.143 + or - 0.054) The third-law calculation of the enthalpy change for the reaction Al 4 SiC 4 (s) = 4Al(g) + SiC(hex) + 3C(s) using the present aluminum pressures gives ΔH 0 (298.15 K) = (1455 + or - 79) kJ /SUP ./ mol -1 . The corresponding second-law result is ΔH 0 (298.15 K) = (1456 + or - 47) kJ /SUP ./ mol -1 . The standard enthalpy of formation of Al 4 SiC 4 (s) from the elements calculated from the present vaporization enthalpy (third-law calculation) and the enthalpies of formation of Al(g) and hexagonal SiC is ΔH 0 /SUB f/ (298.15 K) = -(221 + or - 85) kJ /SUP ./ mol -1 . The standard enthalpy of formation of Al 4 SiC 4 (s) from its constituent carbides Al 4 C 3 (s) and SiC(c, hex) is calculated to be ΔH 0 (298.15 K) = (38 + or - 92) KJ /SUP ./ mol -1

Experimental standard molar enthalpies of formation of some methylbenzenediol isomers

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Lobo Ferreira, Ana I.M.C.

2009-01-01

The present work is part of a research program on the energetics of formation of alkyl substituted benzenediols, aiming the study of the enthalpic effect of the introduction of methyl substituents into benzenediols. In this work we present the results of the thermochemical research on 2-methylresorcinol, 3-methylresorcinol, 4-methylresorcinol, and methylhydroquinone. The standard (p 0 =0.1MPa) molar enthalpies of formation, in the crystalline phase, at T = 298.15 K, of the compounds mentioned above were derived from their standard massic energies of combustion, measured by static-bomb combustion calorimetry, while the standard molar enthalpies of sublimation of those compounds were obtained by the temperature dependence of their vapour pressures determined by the Knudsen effusion technique. From experimental values, the standard molar enthalpies of formation of the studied methylbenzenediols in the gaseous phase, at T = 298.15 K were then derived. The results are interpreted in terms of structural contributions to the energetics of the substituted benzenediols and compared with the same parameters estimated from the Cox Scheme. Moreover, the standard (p 0 =0.1MPa) molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived for the four isomers of methylbenzenediols.

Effect of Calcium chloride and Cadmium chloride on the enthalpy of ...

African Journals Online (AJOL)

This paper presents the effect of two dissolved inorganic salts, CaCl2 and CdCl2 on the enthalpy of mixing of the binary 1,4 dioxane + water system has been investigated at 303.15 K in an isothermal displacement calorimeter with vapour space. A significantly increasing trend in the endothermic excess enthalpy values for ...

Vapour pressures and enthalpies of vaporization of a series of the ferrocene derivatives

International Nuclear Information System (INIS)

Emel'yanenko, Vladimir N.; Verevkin, Sergey P.; Krol, Olesya V.; Varushchenko, Raisa M.; Chelovskaya, Nelly V.

2007-01-01

Vapour pressures of the ferrocene, ferrocene-methanol, benzyl-ferrocene, and benzoyl-ferrocene have been determined by the transpiration method. The molar enthalpies of sublimation Δ cr g H m and of vaporization Δ l g H m have been determined from the temperature dependence of the vapour pressure. The molar enthalpies of fusion of these compounds were measured by d.s.c. The measured data sets of vaporization, sublimation, and fusion enthalpies were checked for internal consistency

Insights on activation enthalpy for non-Schmid slip in body-centered cubic metals

International Nuclear Information System (INIS)

Hale, Lucas M.; Lim, Hojun; Zimmerman, Jonathan A.; Battaile, Corbett C.; Weinberger, Christopher R.

2015-01-01

We use insights gained from atomistic simulation to develop an activation enthalpy model for dislocation slip in body-centered cubic iron. Using a classical potential that predicts dislocation core stabilities consistent with ab initio predictions, we quantify the non-Schmid stress-dependent effects of slip. The kink-pair activation enthalpy is evaluated and a model is identified as a function of the general stress state. Our model enlarges the applicability of the classic Kocks activation enthalpy model to materials with non-Schmid behavior

Standard molar enthalpies of formation of sodium alkoxides

International Nuclear Information System (INIS)

Chandran, K.; Srinivasan, T.G.; Gopalan, A.; Ganesan, V.

2007-01-01

The molar enthalpies of solution of sodium in methanol, ethanol, and n-propanol and of sodium alkoxides in their corresponding alcohols were measured at T=298.15K using an isoperibol solution calorimeter. From these results and other auxiliary data, the standard molar enthalpies of formation, Δ f H m o (RONa,cr) of sodium methoxide, sodium ethoxide, and sodium n-propoxide were calculated and found to be {(-366.21+/-1.38) (-413.39+/-1.45), and (-441.57+/-1.18)}kJ.mol -1 , respectively. A linear correlation has been found between Δ f H m o (RONa)andΔ f H m o (ROH) for R=n-alkyl, enabling the prediction of data for other sodium alkoxides

Standard molar enthalpies of formation of 2-, 3-, and 4-piperidinomethanol isomers

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Cabral, Joana I.T.A.

2006-01-01

The standard (p o =0.1MPa) molar energies of combustion in oxygen of 2-piperidinemethanol, 3-piperidinemethanol, and 4-piperidinemethanol, all in the crystalline phase, were measured, at T=298.15K, by static bomb calorimetry. These values were used to derive the standard molar enthalpies of combustion and the standard molar enthalpies of formation, in the condensed phase, for these compounds. Further, the standard molar enthalpies of sublimation, at T=298.15K, of these three piperidinomethanol isomers were determined by Cavet microcalorimetry. The combustion calorimetry results together with those from the Calvet microcalorimetry, were used to derive the standard molar enthalpies of formation, at T=298.15K, in the gaseous phase, of the three piperidinemethanol studied. -Δ c H m o (cr)Δ cr g H m o kJ.mol -1 kJ.mol -1 2-Piperidinemethanol3890.70+/-0.9293.02+/-0.503- Piperidinemethanol3895.3+/-1.195.9+/-1.44-Piperidinemethanol3891.3+/- 1.198.31+/-0.69

Experimental redetermination of the gas-phase enthalpy of formation of ethyl 2-thiophenecarboxylate

International Nuclear Information System (INIS)

Santos, Ana Filipa L.O.M.; Ribeiro da Silva, Manuel A.V.

2013-01-01

The condensed phase standard (p° = 0.1 MPa) molar enthalpy of formation of ethyl-2-thiophenecarboxylate was derived from the remeasured standard molar energy of combustion, in oxygen, at T = 298.15 K, by rotating bomb combustion calorimetry and the standard molar enthalpy of vaporization, at T = 298.15 K, remeasured by Calvet microcalorimetry. Combining these two values, the following enthalpy of formation in the gas phase, at T = 298.15 K, was then derived for ethyl-2-thiophenecarboxylate: −(277.7 ± 2.9) kJ · mol −1 . The calculated gas-phase enthalpy of formation of the title compound, through the G3(MP2)//B3LYP approach was found to be 278.9 kJ · mol −1 , in excellent agreement with the experimental measured value

The effects of finite rate chemical processes on high enthalpy nozzle performance - A comparison between SPARK and SEAGULL

Science.gov (United States)

Carpenter, M. H.

1988-01-01

The generalized chemistry version of the computer code SPARK is extended to include two higher-order numerical schemes, yielding fourth-order spatial accuracy for the inviscid terms. The new and old formulations are used to study the influences of finite rate chemical processes on nozzle performance. A determination is made of the computationally optimum reaction scheme for use in high-enthalpy nozzles. Finite rate calculations are compared with the frozen and equilibrium limits to assess the validity of each formulation. In addition, the finite rate SPARK results are compared with the constant ratio of specific heats (gamma) SEAGULL code, to determine its accuracy in variable gamma flow situations. Finally, the higher-order SPARK code is used to calculate nozzle flows having species stratification. Flame quenching occurs at low nozzle pressures, while for high pressures, significant burning continues in the nozzle.

Enthalpy of solution of potassium iodide in the water-formamide-dimethyl sulfoxide mixtures

International Nuclear Information System (INIS)

Belova, L.N.; Solov'ev, S.N.; Vorob'ev, A.F.

1985-01-01

Solution enthalpies are measured for potassium iodide in the water-formamide-dimethyl sulfoxide mixtures in a sealed oscillating calorimeter with an isothermal shell at a constant water molar fraction equal to 0.3; 0.5 and 0.7 at 298.15 K. A diagram of the dependence of solution enthalpies on the of mixed solvent composition is plotted. Deviations of experimental solution enthalpies from the calculated ones are negative over the entire concentration range studied, which testifies to the preferable solvatation of electrolyte by the formid and dimthyl sulfoxide molecules

Experimental standard molar enthalpies of formation of some 4-alkoxybenzoic acids

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Lobo Ferreira, Ana I.M.C.; Maciel, Fabrice M.

2010-01-01

The present work is part of a research program on the energetics of the linear 4-n-alkoxybenzoic acids, aiming the study of the enthalpic effect of the introduction of an alkoxy chain in the position 4- of the benzoic acid ring. In this work, we present the results of the thermochemical research on 4-n-alkoxybenzoic acids with the alkoxy chain length n = 2, 4, and 8. The standard (p 0 =0.1MPa) molar enthalpy of formation of crystalline 4-ethoxybenzoic acid, 4-butoxybenzoic acid, and 4-(octyloxy)benzoic acid was measured, at T = 298.15 K, by static-bomb calorimetry. These values, combined with the values of standard molar enthalpies of sublimation, were used to derive the standard molar enthalpies of formation in the gaseous phase.

Recommended sublimation pressure and enthalpy of benzene

Czech Academy of Sciences Publication Activity Database

Růžička, K.; Fulem, Michal; Červinka, C.

2014-01-01

Roč. 68, Jan (2014), s. 40-47 ISSN 0021-9614 Institutional support: RVO:68378271 Keywords : benzene * vapor pressure * heat capacity * ideal - gas thermodynamic properties * sublimation enthalpy * recommended vapor pressure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.679, year: 2014

Enthalpy of vaporization and vapor pressure of whiskey lactone and menthalactone by correlation gas chromatography

International Nuclear Information System (INIS)

Simmons, Daniel; Chickos, James

2017-01-01

Highlights: • The vapor pressure and vaporization enthalpies of cis and trans-whiskey lactone have been evaluated. • Enthalpies of vaporization and vapor pressures of (+)-isomintlactone and (−)-mintlactone were also evaluated. • The sublimation enthalpy and corresponding vapor pressure of (+) -isomintlactone at T = 298.15 K is estimated. - Abstract: Enthalpies of vaporization at T = 298.15 K of cis and trans-whiskey lactone have been evaluated by correlation gas chromatography to be (68.4 ± 1.7) kJ·mol −1 and (67.5 ± 1.7) kJ·mol −1 , respectively. The enthalpies of vaporization of isomintlactone and mintlactone also evaluated by correlation gas chromatography have been found to have vaporization enthalpies of (74.2 ± 1.8) kJ·mol −1 and (73.2 ± 1.8) kJ·mol −1 respectively. The vapor pressures for cis and trans-whiskey lactone at T = 298.15 K have been evaluated as (1.5 ± 0.09) Pa and (2.0 ± 0.1) Pa using vapor pressures of a series of lactones as standards. Vapor pressures for isomintlactone and mintlactone were evaluated as (0.26 ± 0.012) Pa and (0.33 ± 0.02) Pa, respectively. Fusion and sublimation enthalpies for (+)-isomintlactone as well as the vapor pressure of the solid have been estimated.

Temperatures and enthalpies of melting of alkali-metal perrhenates

International Nuclear Information System (INIS)

Lukas, W.; Gaune-Escard, M.

1982-01-01

Melting temperatures and enthalpies of melting were determined for alkali-metal perrhenates by differential enthalpic analysis using a high-temperature Calvet microcalorimeter. The following values were obtained: for LiReO 4 : 692 K and 24.9 kJ.mol -1 ; for NaReO 4 : 693 K and 33 kJ.mol -1 ; for KReO 4 : 828 K and 36 kJ.mol -1 ; for RbReO 4 : 878 K and 34 kJ.mol -1 ; for CsReO 4 : 893 K and 34 kJ.mol -1 . (author)

Methanol wetting enthalpy on few-layer graphene decorated hierarchical carbon foam for cooling applications

Energy Technology Data Exchange (ETDEWEB)

Paul, R., E-mail: paul24@purdue.edu [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Zemlyanov, D. [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Voevodin, A.A.; Roy, A.K. [Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, OH 45433 (United States); Fisher, T.S. [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Department of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)

2014-12-01

Vertical few-layer thick graphene petals are grown on macro-porous carbon foam surfaces having an intrinsic open porosity of 75%. This provides a hierarchical porous structure with a potential for surface adsorption/desorption or wetting/dewetting based thermal energy storage applications. Carbon foams have a combined advantage of large surface area and high thermal conductivity critical for thermal energy storage, but they are prone to oxidation and exhibit low adsorption enthalpies for lightweight hydrocarbons. Here we report graphene petal decoration of carbon foam surfaces and subsequent chemical modification through boron nitride incorporation in hexagonal carbon planes of both carbon foams and graphene petals. This chemically reactive hierarchical structure is characterized with FESEM, Raman, XRD, and XPS measurements. Methanol wetting enthalpy of this three-dimensional hierarchical material was measured with a solution calorimeter, and had shown a six fold increase (from 78 to 522 J/g of foam) as compared to the carbon foam prior to the surface modification. Influences of petal decoration on the surface morphology of carbon foam, BN chemical modification, structure and stoichiometry of the hierarchical material surface, and methanol wetting enthalpy improvement are discussed in detail. The applicability of this hierarchical porous material for thermal energy applications is established. - Highlights: • 500 nm thick few layer graphene petals decoration vertically on macroporous carbon foam surface. • Microwave heating assisted chemical treatment for boron-nitride modification. • Defective petals edges due to boron nitride domain formation. • 20 at. % boron and nitrogen incorporation. • Six fold increase in methanol wetting enthalpy on boron-nitride modification.

Methanol wetting enthalpy on few-layer graphene decorated hierarchical carbon foam for cooling applications

International Nuclear Information System (INIS)

Paul, R.; Zemlyanov, D.; Voevodin, A.A.; Roy, A.K.; Fisher, T.S.

2014-01-01

Vertical few-layer thick graphene petals are grown on macro-porous carbon foam surfaces having an intrinsic open porosity of 75%. This provides a hierarchical porous structure with a potential for surface adsorption/desorption or wetting/dewetting based thermal energy storage applications. Carbon foams have a combined advantage of large surface area and high thermal conductivity critical for thermal energy storage, but they are prone to oxidation and exhibit low adsorption enthalpies for lightweight hydrocarbons. Here we report graphene petal decoration of carbon foam surfaces and subsequent chemical modification through boron nitride incorporation in hexagonal carbon planes of both carbon foams and graphene petals. This chemically reactive hierarchical structure is characterized with FESEM, Raman, XRD, and XPS measurements. Methanol wetting enthalpy of this three-dimensional hierarchical material was measured with a solution calorimeter, and had shown a six fold increase (from 78 to 522 J/g of foam) as compared to the carbon foam prior to the surface modification. Influences of petal decoration on the surface morphology of carbon foam, BN chemical modification, structure and stoichiometry of the hierarchical material surface, and methanol wetting enthalpy improvement are discussed in detail. The applicability of this hierarchical porous material for thermal energy applications is established. - Highlights: • 500 nm thick few layer graphene petals decoration vertically on macroporous carbon foam surface. • Microwave heating assisted chemical treatment for boron-nitride modification. • Defective petals edges due to boron nitride domain formation. • 20 at. % boron and nitrogen incorporation. • Six fold increase in methanol wetting enthalpy on boron-nitride modification

Enthalpy of mixing of liquid Ag–Bi–Cu alloys at 1073 K

International Nuclear Information System (INIS)

Fima, Przemysław; Flandorfer, Hans

2014-01-01

Highlights: • Partial and integral mixing enthalpies of liquid Ag–Bi–Cu alloys were determined. • Integral mixing enthalpies are small and endothermic, similar to limiting binaries. • The ternary data were fitted on the basis of Redlich–Kister–Muggianu model. - Abstract: The Ag–Bi–Cu system is among those ternary systems which have not been fully studied yet, in particular the thermodynamic description of the liquid phase is missing. Partial and integral enthalpies of mixing of liquid ternary Ag–Bi–Cu alloys were determined over a broad composition range along six sections: x(Ag)/x(Bi) = 0.25, 1, 4; x(Ag)/x(Cu) = 1.5; x(Bi)/x(Cu) = 1.86, 4. Measurements were carried out at 1073 K using two Calvet type microcalorimeters and drop calorimetric technique. It was found that integral enthalpies of mixing are small and endothermic, similarly to limiting binary alloys. The ternary data were fitted on the basis of an extended Redlich–Kister–Muggianu model for substitutional solutions. There are no significant additional ternary interactions

Characterization of Adsorption Enthalpy of Novel Water-Stable Zeolites and Metal-Organic Frameworks

Science.gov (United States)

Kim, Hyunho; Cho, H. Jeremy; Narayanan, Shankar; Yang, Sungwoo; Furukawa, Hiroyasu; Schiffres, Scott; Li, Xiansen; Zhang, Yue-Biao; Jiang, Juncong; Yaghi, Omar M.; Wang, Evelyn N.

2016-01-01

Water adsorption is becoming increasingly important for many applications including thermal energy storage, desalination, and water harvesting. To develop such applications, it is essential to understand both adsorbent-adsorbate and adsorbate-adsorbate interactions, and also the energy required for adsorption/desorption processes of porous material-adsorbate systems, such as zeolites and metal-organic frameworks (MOFs). In this study, we present a technique to characterize the enthalpy of adsorption/desorption of zeolites and MOF-801 with water as an adsorbate by conducting desorption experiments with conventional differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). With this method, the enthalpies of adsorption of previously uncharacterized adsorbents were estimated as a function of both uptake and temperature. Our characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorption enthalpies of MOF-801 are nearly constant for a wide range of vapor uptakes.

The enthalpy of sublimation and thermodynamic functions of fermium

International Nuclear Information System (INIS)

Haire, R.G.; Gibson, J.K.

1989-01-01

The enthalpy of sublimation of fermium (Fm), element 100, has now been determined directly by measuring the partial pressure of Fm over alloys, for the temperature range of 642 to 905 K. The partial pressures were determined using Knudsen effusion and target collection techniques. Dilute (10 -5 --10 -7 atom %) solid alloys of Fm and mixtures of Fm and Es in both Sm and Yb solvents were studied. The presence of Es in two of the alloys allowed a direct comparison of the behavior of Fm and Es, where the latter could be used as a reference. It was possible to calculate enthalpies of sublimation and a hypothetical vapor pressure/temperature relationship for pure Fm metal by selecting Yb as the solvent most likely to form a nearly ideal alloy with Fm. From the experimental vapor pressure data, we derived average Second Law values of 33.8±3 kcal/mol and 23.5±3 cal/mol deg for the enthalpy and entropy of sublimation of Fm at 298 K. Third Law enthalpy values were also calculated using the experimental partial pressure data and entropies estimated from derived free energy functions and heat capacities for the solid and gaseous forms of Fm. The average Third Law values (34.8 kcal/mol and 25.1 cal/mol deg, respectively, at 298 K) are in agreement with those obtained via the Second Law. These results establish that Fm, like Es (element 99), is a divalent metal. The finding that Fm metal is the second divalent actinide element experimentally establishes the trend towards metallic divalency expected in the second half of the actinide series

Standard enthalpy of formation of Sm6UO12 acid dissolution calorimetry

International Nuclear Information System (INIS)

Venkata Krishnan, R.; Jogeswararao, G.; Ananthasivan, K.

2016-01-01

The standard molar enthalpies of formation of Δ f (298 K) of Sm 6 UO 12 have been determined by using an indigenously developed isoperibol acid solution calorimeter. The water equivalent of this calorimeter was determined by electrical calibration. The accuracy of measurement were determined by using standard materials KCl and tris(hydroxyl methyl) amino-methane (TRIS) and was found to be within ±2%. The enthalpies of solution at 298 K of Sm 2 O 3 , UO 3 and Sm 6 UO 12 were measured by using this calorimeter. From these experimental results the enthalpies of formation of Sm 6 UO 12 at 298 K were computed by using Hess's law of summation. (author)

The enthalpies of formation of alkyl carbamates: Experimental and computational redetermination

International Nuclear Information System (INIS)

Santos, Ana Filipa L.O.M.; Ribeiro da Silva, Manuel A.V.

2013-01-01

Highlights: ► Combustion calorimetry was used to redetermine Δ f H m o (cr) of methyl and ethyl carbamates. ► Δ cr g H m o of methyl and ethyl carbamates were redetermined by Calvet Microcalorimetry. ► Gas-phase Δ f H m o of the studied compounds have been derived from the experimental values of Δ f H m o (cr) and Δ cr g H m o . ► Gas-phase Δ f H m o of the studied compounds have been calculated by computational thermochemistry. ► The obtained Δ f H m o (g) for the alkylcarbamates are discussed versus literature values for the same compounds. - Abstract: In the present work, a redetermination of thermochemical data of methyl carbamate and ethyl carbamate was performed by both experimental and computational techniques. Their gas-phase standard (p o = 0.1 MPa) molar enthalpies of formation, Δ f H m o (g), at T = 298.15 K, were derived from the standard molar enthalpies of formation, in the crystalline phase, Δ f H m o (cr), and from the standard molar enthalpies of sublimation, Δ cr g H m o at T = 298.15 K, measured, respectively, by static bomb combustion calorimetry and high temperature Calvet microcalorimetry. The experimental results were compared with computational data, calculated at the G3(MP2)//B3LYP level, as well as with values reported in the literature. At the B3LYP/6-31G(d) level of theory, the molecular structure of both carbamates was obtained.

Direct determination of enthalpies of solid phase reactions by immersion method; Determination directe des enthalpies de reaction en phase solide par une methode de plongee

Energy Technology Data Exchange (ETDEWEB)

Roux, A; Richard, M; Eyraud, L; Stevanovic, M; Elston, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

It is not generally possible to measure the enthalpy change corresponding to solid phase reactions using the dynamic differential thermal analysis method because these reactions are usually too slow at the temperature of operation of present equipment. A ballistic differential thermal analysis apparatus has been developed which is based on an immersion-compensation method; it overcomes the difficulties previously encountered. This apparatus has been used after calibration for determining the enthalpies of formation of calcium and cadmium titanates. and also the Wigner energies of BeO, MgO and Al{sub 2}O{sub 3} samples irradiated at variable dose at a temperature of under 100 deg. C. (authors) [French] Il n'est generalement pas possible de mesurer la variation d'enthalpie correspondant aux reactions en phase solide par la methode d'analyse thermique differentielle dynamique. En effet, ces reactions sont le plus souvent trop lentes aux temperatures d'utilisation des dispositifs actuels. Un appareil d'analyse thermique differentielle balistique, base sur une methode de plongee avec compensation, a ete mis au point et permet de surmonter les difficultes precedentes. Apres etalonnages, cet appareil a ete utilise pour la determination des enthalpies de formation du titanate de calcium et du titanate de cadmium ainsi que pour celle des energies Wigner emmagasinees dans des echantillons de BeO, MgO et Al{sub 2}O{sub 3} irradies a une temperature inferieure a 100 deg. C et a differentes doses. (auteurs)

Mechanism of influence water vapor on combustion characteristics of propane-air mixture

Science.gov (United States)

Larionov, V. M.; Mitrofanov, G. A.; Sachovskii, A. V.; Kozar, N. K.

2016-01-01

The article discusses the results of an experimental study of the effect of water vapor at the flame temperature. Propane-butane mixture with air is burning on a modified Bunsen burner. Steam temperature was varied from 180 to 260 degrees. Combustion parameters changed by steam temperature and its proportion in the mixture with the fuel. The fuel-air mixture is burned in the excess air ratio of 0.1. It has been established that the injection of steam changes the characteristics of combustion fuel-air mixture and increase the combustion temperature. The concentration of CO in the combustion products is substantially reduced. Raising the temperature in the combustion zone is associated with increased enthalpy of the fuel by the added steam enthalpy. Reducing the concentration of CO is caused by decrease in the average temperature in the combustion zone by applying steam. Concentration of active hydrogen radicals and oxygen increases in the combustion zone. That has a positive effect on the process of combustion.

Standard molar enthalpy of formation of 1-benzosuberone: An experimental and computational study

International Nuclear Information System (INIS)

Miranda, Margarida S.; Morais, Victor M.F.; Matos, M. Agostinha R.; Liebman, Joel F.

2010-01-01

The energetics of 1-benzosuberone was studied by a combination of calorimetric techniques and computational calculations. The standard (p o = 0.1 MPa) molar enthalpy of formation of 1-benzosuberone, in the liquid phase, was derived from the massic energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The standard molar enthalpy of vaporization, at T = 298.15 K, was measured by Calvet microcalorimetry. From these two parameters the standard (p o = 0.1 MPa) molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived: -(96.1 ± 3.4) kJ . mol -1 . The G3(MP2)//B3LYP composite method and appropriate reactions were used to computationally calculate the standard molar enthalpy of formation of 1-benzosuberone, in the gaseous phase, at T = 298.15 K. The computational results are in very good agreement with the experimental value.

Characterization of Adsorption Enthalpy of Novel Water-Stable Zeolites and Metal-Organic Frameworks

Science.gov (United States)

Kim, Hyunho; Cho, H. Jeremy; Narayanan, Shankar; Yang, Sungwoo; Furukawa, Hiroyasu; Schiffres, Scott; Li, Xiansen; Zhang, Yue-Biao; Jiang, Juncong; Yaghi, Omar M.; Wang, Evelyn N.

2016-01-01

Water adsorption is becoming increasingly important for many applications including thermal energy storage, desalination, and water harvesting. To develop such applications, it is essential to understand both adsorbent-adsorbate and adsorbate-adsorbate interactions, and also the energy required for adsorption/desorption processes of porous material-adsorbate systems, such as zeolites and metal-organic frameworks (MOFs). In this study, we present a technique to characterize the enthalpy of adsorption/desorption of zeolites and MOF-801 with water as an adsorbate by conducting desorption experiments with conventional differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). With this method, the enthalpies of adsorption of previously uncharacterized adsorbents were estimated as a function of both uptake and temperature. Our characterizations indicate that the adsorption enthalpies of type I zeolites can increase to greater than twice the latent heat whereas adsorption enthalpies of MOF-801 are nearly constant for a wide range of vapor uptakes. PMID:26796523

Investigation of enthalpy and specific heat of the gallium-indium-tin eutectic alloy

International Nuclear Information System (INIS)

Roshchupkin, V.V.; Migaj, L.L.; Fordeeva, L.K.; Perlova, N.L.

1978-01-01

Enthalpy and specific heat of the fusible (melting point is 10.6 deg C) eutectic alloy (67% Ga - 20.5% In - 12.5% Sn according to mass) are determined by the mixing method. The determination was carried out in vacuum at the residual pressure of >= 1x10 -5 torr in the temperature range from 59.3 to 437.0 deg C. It is established that temperature dependence of alloy enthalpy is described by the equation: Hsub(t) - Hsub(0degC)=1.014+0.0879t-0.0000129 t 2 , where (Hsub(t) - Hsub(0degC)) is enthalpy, cal/g; t-temperature, deg C. Mean-square dispersion is +-0.6%. Temperature dependence of alloy specific heat in the temperature range under study was determined by differentiation of the equation obtained for enthalpy: Csub(p)=0.0879-0.000026t, where Csub(p)-specific heat, cal/gx deg. It is supposed that temperature increase makes it possible to decrease slightly specific heat

Measuring the enthalpies of interaction between glycine, L-cysteine, glycylglycine, and sodium dodecyl sulfate in aqueous solutions

Science.gov (United States)

Badelin, V. G.; Mezhevoi, I. N.; Tyunina, E. Yu.

2017-03-01

Calorimetric measurements of enthalpies of solution Δsol H m for glycine, L-cysteine, and glycylglycine in aqueous solutions of sodium dodecyl sulfate (SDS) with concentrations of up to 0.05 mol kg-1 are made. Standard enthalpy of solution Δsol H 0 and enthalpy of transfer Δtr H 0 of the dipeptide from water into mixed solvent are calculated. The calculated enthalpy coefficients of paired interactions of amino acids and dipeptide with SDS prove to be positive. Hydrophobic interactions between the biomolecules and SDS are found to have a major impact on the enthalpies of interaction in the three-component systems under study, within the indicated range of concentrations.

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Directory of Open Access Journals (Sweden)

Catherine Colinet

2015-11-01

Full Text Available The enthalpies of formation of transition metals diborides in various structures have been obtained from density functional theory (DFT calculations in order to determine the ground state at T = 0 K and p = 0. The evolution of the enthalpies of formation along the 3D, 4D, and 5D series has been correlated to the considered crystal structures. In the whole, the calculated values of the enthalpies of formation of the diborides in their ground state are in good agreement with the experimental ones when available. The calculated values of the lattice parameters at T = 0 K of the ground state agree well with the experimental values. The total and partial electronic densities of states have been computed. Special features of the transition metal electronic partial density of states have been evidenced and correlated to the local environment of the atoms.

Theoretical calculation of enthalpy of formation of multiconformational molecules: 1,2-ethanediol, propanediols, and glycerol

Science.gov (United States)

Dorofeeva, Olga V.; Suchkova, Taisiya A.

2018-04-01

The gas-phase enthalpies of formation of four molecules with high flexibility, which leads to the existence of a large number of low-energy conformers, were calculated with the G4 method to see whether the lowest energy conformer is sufficient to achieve high accuracy in the computed values. The calculated values were in good agreement with the experiment, whereas adding the correction for conformer distribution makes the agreement worse. The reason for this effect is a large anharmonicity of low-frequency torsional motions, which is ignored in the calculation of ZPVE and thermal enthalpy. It was shown that the approximate correction for anharmonicity estimated using a free rotor model is of very similar magnitude compared with the conformer correction but has the opposite sign, and thus almost fully compensates for it. Therefore, the common practice of adding only the conformer correction is not without problems.

Enthalpies of solution of ampicillin, amoxycillin and their binary mixtures at 310.15 K.

Science.gov (United States)

Jain, D V; Kashid, N; Kapoor, S; Chadha, R

2000-05-15

Enthalpies of solutions of ampicillin, amoxycillin and their binary mixtures have been determined at pH 2, 5, and 7 using C-80 calorimeter. The systems showed endothermic behaviour; molar enthalpies of solutions of ampicillin were determined to be 13.32, 15.89 and 23.21 kJ mol(-1) and amoxycillin were 16.32, 18.45 and 26. 25 kJ mol(-1) at pH 2, 5, and 7, respectively. The excess molar enthalpies of solution have also been calculated to find any interaction between these two drugs.

Revision of standard molar enthalpies of formation of glycine and L-alanine in the gaseous phase on the basis of theoretical calculations

International Nuclear Information System (INIS)

Dorofeeva, Olga V.; Ryzhova, Oxana N.

2009-01-01

The standard molar enthalpies of formation of urea, glycine, and L-alanine in the gaseous phase at 298.15 K were calculated by the high-level Gaussian-3X method. The agreement with the available experimental data is very good for urea and glycine and, thus, supports the high accuracy of calculated values. A significant discrepancy between theoretical and experimental enthalpy of formation values for L-alanine provides a reason to reconsider the experimental data previously used to derive the standard molar enthalpy of formation of L-alanine in the gaseous phase at 298.15 K. To obtain a more reliable value of enthalpy of sublimation at 298.15 K, the heat capacity values of gaseous L-alanine were calculated by standard statistical thermodynamics formulae using molecular parameters determined from B3LYP/cc-pVTZ calculations. With the obtained value of C p,m 0 (L-alanine, g, 298.15 K) = 112.6 ± 4.0 J . K -1 . mol -1 the original published experimental values of enthalpy of sublimation of L-alanine were readjusted to the reference temperature: Δ cr g H m (L-alanine, 298.15 K) = 135.2 ± 2.0 kJ . mol -1 . This value, together with the experimental enthalpy of formation of solid L-alanine, Δ f H m 0 (L-alanine, cr, 298.15 K) = -560.0 ± 1.0 kJ . mol -1 [S.N. Ngauv, R. Sabbah, M. Laffitte, Thermochim. Acta 20 (1977) 371-380; I. Contineanu, D.I. Marchidan, Rev. Roum. Chim. 29 (1984) 43-48], gives a new value for the enthalpy of formation of L-alanine in the gaseous phase, Δ f H m 0 (L-alanine, g, 298.15 K) = -424.8 ± 2.0 kJ . mol -1 , which is in good agreement with our theoretical G3X result, -427.6 ± 4.0 kJ . mol -1 . The same procedure for glycine allowed us to improve the literature value of the enthalpy of formation for this compound, Δ f H m 0 (glycine, g, 298.15 K) = -393.7 ± 1.5 kJ . mol -1 . As a result a set of self-consistent thermochemical data for glycine and L-alanine is proposed

Enthalpies of solution of methylcalix[4]resorcinarene in non-aqueous solvents as a function of concentration and temperature

International Nuclear Information System (INIS)

Riveros, Diana C.; Martínez, Fleming; Vargas, Edgar F.

2012-01-01

Highlights: ► The solution enthalpies of methylcalix[4]resorcinarene in alcohols have been measured. ► The solution enthalpies of methylcalix[4]resorcinarene in alcohols are endothermic. ► Enthalpies of transference are interpreted in terms of proton donor capacity of alcohols. - Abstract: Enthalpies of solution of 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxyresorci[4]arene in methanol, ethanol and propanol as a function of molal concentration at (288.15, 298.15 and 308.15) K were measured calorimetrically. The enthalpies of solvation were estimated. Using propanol as the referent solvent, transfer properties to other alcohols were also calculated. In addition, temperature dependence of the enthalpy of solution at infinite dilution was also obtained. The data were interpreted in terms of solute–solvent interactions.

Enthalpy recovery in glassy materials: Heterogeneous versus homogenous models

Science.gov (United States)

Mazinani, Shobeir K. S.; Richert, Ranko

2012-05-01

Models of enthalpy relaxations of glasses are the basis for understanding physical aging, scanning calorimetry, and other phenomena that involve non-equilibrium and non-linear dynamics. We compare models in terms of the nature of the relaxation dynamics, heterogeneous versus homogeneous, with focus on the Kovacs-Aklonis-Hutchinson-Ramos (KAHR) and the Tool-Narayanaswamy-Moynihan (TNM) approaches. Of particular interest is identifying the situations for which experimental data are capable of discriminating the heterogeneous from the homogeneous scenario. The ad hoc assumption of a single fictive temperature, Tf, is common to many models, including KAHR and TNM. It is shown that only for such single-Tf models, enthalpy relaxation of a glass is a two-point correlation function in reduced time, implying that experimental results are not decisive regarding the underlying nature of the dynamics of enthalpy relaxation. We also find that the restriction of the common TNM model to a Kohlrausch-Williams-Watts type relaxation pattern limits the applicability of this approach, as the particular choice regarding the distribution of relaxation times is a more critical factor compared with isothermal relaxation experiments. As a result, significant improvements in fitting calorimetry data can be achieved with subtle adjustments in the underlying relaxation time distribution.

Excess Enthalpies of Mixing of Binary Mixtures of NaCl, KCl, NaBr ...

African Journals Online (AJOL)

NJD

2004-07-01

Jul 1, 2004 ... NaBr and KBr in Mixed Ternary Solvent Systems at 298.15 K. Bal Raj Deshwala* ... industrial waters and their thermodynamic properties are of practical interest for .... The enthalpy of mixing (∆Hm) is the difference between the excess enthalpy of the ..... tural (categorized by softness, open- ness, and ...

Interface Enthalpy-Entropy Competition in Nanoscale Metal Hydrides

Directory of Open Access Journals (Sweden)

Nicola Patelli

2018-01-01

Full Text Available We analyzed the effect of the interfacial free energy on the thermodynamics of hydrogen sorption in nano-scaled materials. When the enthalpy and entropy terms are the same for all interfaces, as in an isotropic bi-phasic system, one obtains a compensation temperature, which does not depend on the system size nor on the relative phase abundance. The situation is different and more complex in a system with three or more phases, where the interfaces have different enthalpy and entropy. We also consider the possible effect of elastic strains on the stability of the hydride phase and on hysteresis. We compare a simple model with experimental data obtained on two different systems: (1 bi-phasic nanocomposites where ultrafine TiH2 crystallite are dispersed within a Mg nanoparticle and (2 Mg nanodots encapsulated by different phases.

Solution enthalpies of alkali metal halides in water and heavy water mixtures with dimethyl sulfoxide

International Nuclear Information System (INIS)

Egorov, G.I.

1994-01-01

Solution enthalpies of CsF, LiCl, NaI, CsI and some other halides of alkali metals and tetrabutylammonium have been measured by the method of calorimetry. Standard solution enthalpies of all alkali metals (except rubidium) halides in water and heavy water mixtures with dimethylsulfoxide at 298.15 K have been calculated. Isotopic effects in solvation enthalpy of the electrolytes mentioned in aqueous solutions of dimethylsulfoxide have been discussed. 29 refs., 2 figs., 4 tabs

Molecular simulation of excess isotherm and excess enthalpy change in gas-phase adsorption.

Science.gov (United States)

Do, D D; Do, H D; Nicholson, D

2009-01-29

We present a new approach to calculating excess isotherm and differential enthalpy of adsorption on surfaces or in confined spaces by the Monte Carlo molecular simulation method. The approach is very general and, most importantly, is unambiguous in its application to any configuration of solid structure (crystalline, graphite layer or disordered porous glass), to any type of fluid (simple or complex molecule), and to any operating conditions (subcritical or supercritical). The behavior of the adsorbed phase is studied using the partial molar energy of the simulation box. However, to characterize adsorption for comparison with experimental data, the isotherm is best described by the excess amount, and the enthalpy of adsorption is defined as the change in the total enthalpy of the simulation box with the change in the excess amount, keeping the total number (gas + adsorbed phases) constant. The excess quantities (capacity and energy) require a choice of a reference gaseous phase, which is defined as the adsorptive gas phase occupying the accessible volume and having a density equal to the bulk gas density. The accessible volume is defined as the mean volume space accessible to the center of mass of the adsorbate under consideration. With this choice, the excess isotherm passes through a maximum but always remains positive. This is in stark contrast to the literature where helium void volume is used (which is always greater than the accessible volume) and the resulting excess can be negative. Our definition of enthalpy change is equivalent to the difference between the partial molar enthalpy of the gas phase and the partial molar enthalpy of the adsorbed phase. There is no need to assume ideal gas or negligible molar volume of the adsorbed phase as is traditionally done in the literature. We illustrate this new approach with adsorption of argon, nitrogen, and carbon dioxide under subcritical and supercritical conditions.

On the Enthalpy and Entropy of Point Defect Formation in Crystals

Science.gov (United States)

Kobelev, N. P.; Khonik, V. A.

2018-03-01

A standard way to determine the formation enthalpy H and entropy S of point defect formation in crystals consists in the application of the Arrhenius equation for the defect concentration. In this work, we show that a formal use of this method actually gives the effective (apparent) values of these quantities, which appear to be significantly overestimated. The underlying physical reason lies in temperature-dependent formation enthalpy of the defects, which is controlled by temperature dependence of the elastic moduli. We present an evaluation of the "true" H- and S-values for aluminum, which are derived on the basis of experimental data by taking into account temperature dependence of the formation enthalpy related to temperature dependence of the elastic moduli. The knowledge of the "true" activation parameters is needed for a correct calculation of the defect concentration constituting thus an issue of major importance for different fundamental and application issues of condensed matter physics and chemistry.

Study of Shallow Low-Enthalpy Geothermal Resources Using Integrated Geophysical Methods

Science.gov (United States)

De Giorgi, Lara; Leucci, Giovanni

2015-02-01

The paper is focused on low enthalpy geothermal exploration performed in south Italy and provides an integrated presentation of geological, hydrogeological, and geophysical surveys carried out in the area of municipality of Lecce. Geological and hydrogeological models were performed using the stratigraphical data from 51 wells. A ground-water flow (direction and velocity) model was obtained. Using the same wells data, the ground-water annual temperature was modeled. Furthermore, the ground surface temperature records from ten meteorological stations were studied. This allowed us to obtain a model related to the variations of the temperature at different depths in the subsoil. Integrated geophysical surveys were carried out in order to explore the low-enthalpy geothermal fluids and to evaluate the results of the model. Electrical resistivity tomography (ERT) and self-potential (SP) methods were used. The results obtained upon integrating the geophysical data with the models show a low-enthalpy geothermal resource constituted by a shallow ground-water system.

Vaporization, fusion and sublimation enthalpies of the dicarboxylic acids from C4 to C14 and C16

International Nuclear Information System (INIS)

Roux, Maria Victoria; Temprado, Manuel; Chickos, James S.

2005-01-01

The fusion enthalpies of the series butanedioic acid through to tetradecanedioic acid and hexadecanedioic acids have been measured by DSC. In addition to fusion, a number of solid-solid phase transitions have also been detected in these diacids. The vaporization enthalpies of these compounds have been measured by correlation gas chromatography using the vaporization enthalpies of butanedioic, hexanedioic and decanedioic acids as standards. The vaporization enthalpies of the diacids from C 4 to C 10 correlated linearly with the number of methylene groups present. Above C 10 , the vaporization enthalpies of C 11 -C 14 and C 16 begin to deviate from linearity. The vaporization enthalpies for these compounds are dependent on the temperature of the GC column used. Similar departure from linearity has also been observed previously in the sublimation enthalpies for these compounds. The results are discussed in terms of formation of a cyclic intramolecular hydrogen bonded network in the gas phase similar to the bimolecular association observed in smaller mono-carboxylic acids at ambient temperatures

Enthalpies of mixing in binary liquid alloys of lutetium with 3d metals

Energy Technology Data Exchange (ETDEWEB)

Ivanov, Michael; Berezutski, Vadim [National Academy of Sciences, Kyiv (Ukraine). I. Frantsevich Institute for Problems of Materials Science; Usenko, Natalia; Kotova, Natalia [Taras Shevchenko National Univ., Kyiv (Ukraine). Dept. of Chemistry

2017-01-15

The enthalpies of mixing in binary liquid alloys of lutetium with chromium, cobalt, nickel and copper were determined at 1 773 - 1 947 K by isoperibolic calorimetry. The enthalpies of mixing in the Lu-Cr melts (measured up to 40 at.% Cr) demonstrate endothermic effects (ΔH = 6.88 ± 0.66 kJ . mol{sup -1} at x{sub Lu} = 0.60), whereas significant exothermic enthalpies of mixing have been established within a wide composition region for the Co-Lu, Ni-Lu and Cu-Lu liquid alloys. Minimum values of the integral enthalpy of mixing are as follows: ΔH{sub min} = -23.57 ± 1.41 kJ . mol{sup -1} at x{sub Lu} = 0.38 for the Co-Lu system; ΔH{sub min} = -48.65 ± 2.83 kJ . mol{sup -1} at x{sub Lu} = 0.40 for the Ni-Lu system; ΔH{sub min} = -24.63 ± 1.52 kJ . mol{sup -1} at x{sub Lu} = 0.37 for the Cu-Lu system.

Enthalpies of solution of methylcalix[4]resorcinarene in non-aqueous solvents as a function of concentration and temperature

Energy Technology Data Exchange (ETDEWEB)

Riveros, Diana C. [Laboratorio de Termodinamica de Soluciones, Departamento de Quimica, Facultad de Ciencias, Universidad de los Andes, Bogota D.C. (Colombia); Martinez, Fleming [Grupo de Investigaciones Farmaceutico-Fisicoquimicas, Departamento de Farmacia, Facultad de Ciencias, Universidad Nacional de Colombia, Bogota D.C. (Colombia); Vargas, Edgar F., E-mail: edvargas@uniandes.edu.co [Laboratorio de Termodinamica de Soluciones, Departamento de Quimica, Facultad de Ciencias, Universidad de los Andes, Bogota D.C. (Colombia)

2012-11-20

Highlights: Black-Right-Pointing-Pointer The solution enthalpies of methylcalix[4]resorcinarene in alcohols have been measured. Black-Right-Pointing-Pointer The solution enthalpies of methylcalix[4]resorcinarene in alcohols are endothermic. Black-Right-Pointing-Pointer Enthalpies of transference are interpreted in terms of proton donor capacity of alcohols. - Abstract: Enthalpies of solution of 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxyresorci[4]arene in methanol, ethanol and propanol as a function of molal concentration at (288.15, 298.15 and 308.15) K were measured calorimetrically. The enthalpies of solvation were estimated. Using propanol as the referent solvent, transfer properties to other alcohols were also calculated. In addition, temperature dependence of the enthalpy of solution at infinite dilution was also obtained. The data were interpreted in terms of solute-solvent interactions.

Borate-polyol complexes in aqueous solution: determination of enthalpies by thermometric titrimetry.

Science.gov (United States)

Aruga, R

1985-06-01

Enthalpies for the reaction of borate with 1,2-ethanediol, 1,2-propanediol, 1,2,3-propanetriol and d-mannitol have been determined by thermometric titrimetry. From these enthalpies and equilibrium constants taken from the literature, corresponding entropies have been calculated. The data refer to aqueous solutions at 25 degrees and I = 1.0M (NaNO(3)). The results indicate reasons for the differences in the stabilities of the complexes.

Mass spectrometric study of thermodynamic properties of gaseous lead tellurates. Estimation of formation enthalpies of gaseous lead polonates

Energy Technology Data Exchange (ETDEWEB)

Shugurov, S.M., E-mail: s.shugurov@spbu.ru; Panin, A.I.; Lopatin, S.I.; Emelyanova, K.A.

2016-10-15

Gaseous reactions involving lead oxides, tellurium oxide and lead tellurates were studied by the Knudsen effusion mass spectrometry. Equilibrium constants and reaction enthalpies were evaluated. Structures, molecular parameters and thermodynamic functions of gaseous PbTeO{sub 3} and Pb{sub 2}TeO{sub 4} were calculated by quantum chemistry methods. The formation enthalpies Δ{sub f}H{sup 0} (298.15) = −294 ± 13 for gaseous PbTeO{sub 3} and Δ{sub f}H{sup 0} (298.15) = −499 ± 12 for gaseous Pb{sub 2}TeO{sub 4} were obtained. On the base of these results the formation enthalpies of gaseous PbPoO{sub 3} and Pb{sub 2}PoO{sub 4} were estimated as −249 ± 34 and −478 ± 38, respectively. - Highlights: • Gaseous lead tellurates PbTeO{sub 3}, Pb{sub 2}TeO{sub 4} were discovered. • Their thermodynamic properties were studied using both high temperature mass spectrometry and quantum chemistry computations. • The obtained data allows to predict the formation enthalpies of gaseous lead polonates PbPoO{sub 3}, Pb{sub 2}PoO{sub 4}.

Kinetic evidence of an apparent negative activation enthalpy in an organocatalytic process

KAUST Repository

Han, Xiao

2013-08-30

A combined kinetic and computational study on our tryptophan-based bifunctional thiourea catalyzed asymmetric Mannich reactions reveals an apparent negative activation enthalpy. The formation of the pre-transition state complex has been unambiguously confirmed and these observations provide an experimental support for the formation of multiple hydrogen bonding network between the substrates and the catalyst. Such interactions allow the creation of a binding cavity, a key factor to install high enantioselectivity.

Kinetic evidence of an apparent negative activation enthalpy in an organocatalytic process

KAUST Repository

Han, Xiao; Lee, Richmond; Chen, Tao; Luo, Jie; Lu, Yixin; Huang, Kuo-Wei

2013-01-01

A combined kinetic and computational study on our tryptophan-based bifunctional thiourea catalyzed asymmetric Mannich reactions reveals an apparent negative activation enthalpy. The formation of the pre-transition state complex has been unambiguously confirmed and these observations provide an experimental support for the formation of multiple hydrogen bonding network between the substrates and the catalyst. Such interactions allow the creation of a binding cavity, a key factor to install high enantioselectivity.

Knudsen cell vaporization of rare earth nitrides: enthalpy of vaporization of HoN098

International Nuclear Information System (INIS)

Brown, R.C.; Clark, N.J.

1975-01-01

The enthalpy of vaporization of HoN 0 . 98 was measured by the weight-loss Knudsen cell technique using Motzfeldt-Whitman extrapolations to zero orifice area. A third-law enthalpy of vaporization of HoN 0 . 98 of 155.9 +- 5 kcal mole -1 was obtained compared to a second-law value of 162.0 +- 5 kcal mole -1 . Similar measurements on the nitrides of samarium, erbium, and ytterbium gave third-law enthalpies of vaporization of 126.8 +-- 5 kcal mole -1 ; 159.6 +- 5 kcal mole -1 , and 121.0 +- 5 kcal mole -1 , respectively. 7 tables

Experimental study on premixed CH{sub 4}/air mixture combustion in micro Swiss-roll combustors

Energy Technology Data Exchange (ETDEWEB)

Zhong, Bei-Jing; Wang, Jian-Hua [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

2010-12-15

Excess enthalpy combustion is a promising approach to stabilize flame in micro-combustors. Using a Swiss-roll combustor configuration, excess enthalpy combustion can be conveniently achieved. In this work, three types of Swiss-roll combustors with double spiral-shaped channels were designed and fabricated. The combustors were tested using methane/air mixtures of various equivalence ratios. Both temperature distributions and extinction limits were determined for each combustor configuration at different methane mass flow rates. Results indicate that the Swiss-roll combustors developed in the current study greatly enhance combustion stability in center regions of the combustors. At the same time, excess enthalpy combustors of the Swiss-roll configuration significantly extend the extinction limits of methane/air mixtures. In addition, the effects of combustor configurations and thermal insulation arrangements on temperature distributions and extinction limits were evaluated. With heat losses to the environment being significant, the use of thermal insulations further enhances the flame stability in center regions of the Swiss-roll combustors and extends flammable ranges. (author)

Effects of partitioned enthalpy of mixing on glass-forming ability

Energy Technology Data Exchange (ETDEWEB)

Song, Wen-Xiong; Zhao, Shi-Jin, E-mail: shijin.zhao@shu.edu.cn [Institute of Materials Science, Shanghai University, Shanghai 200072 (China)

2015-04-14

We explore the inherent reason at atomic level for the glass-forming ability of alloys by molecular simulation, in which the effect of partitioned enthalpy of mixing is studied. Based on Morse potential, we divide the enthalpy of mixing into three parts: the chemical part (Δ E{sub nn}), strain part (Δ E{sub strain}), and non-bond part (Δ E{sub nnn}). We find that a large negative Δ E{sub nn} value represents strong AB chemical bonding in AB alloy and is the driving force to form a local ordered structure, meanwhile the transformed local ordered structure needs to satisfy the condition (Δ E{sub nn}/2 + Δ E{sub strain}) < 0 to be stabilized. Understanding the chemical and strain parts of enthalpy of mixing is helpful to design a new metallic glass with a good glass forming ability. Moreover, two types of metallic glasses (i.e., “strain dominant” and “chemical dominant”) are classified according to the relative importance between chemical effect and strain effect, which enriches our knowledge of the forming mechanism of metallic glass. Finally, a soft sphere model is established, different from the common hard sphere model.

Preparation of high purity metallic protactinium. Crystal structure and dissolution enthalpy of the metal

International Nuclear Information System (INIS)

Bohet, J.

1977-01-01

Some 300 mg of Pa have been produced in a high purity metallic state. Protactinium monocarbide has been obtained by the carboreduction of Pa 2 O 5 . Protactinium iodide, produced by the direct reaction of iodine on the carbide, has been sublimated at 420 0 C and thermally dissociated at 1200 0 C on a W wire. In these conditions Pa metal has been deposited with a yield greater than 85% and presents a bct structure stable at room temperature (a=3.921+-0.001A and c=3.235+-0.001A). The fcc phase (Fm3m type) (a=5.018+-0.001A) has been obtained by quenching metallic samples (bct) heated in argon at 1500 0 C. The chemical analysis and the transformation of the fcc into bct phase by controlled heat treatments show the presence of this high temperature phase in the metal. Protactinium mononitride (5.58% N) produced by direct reaction of N on Pa at 1100 0 C presents the same fcc crystal structure but the lattice parameter is higher (a=5.047+-0.001A). The dissolution heat of metallic Pa (bct) has been determined in the aqueous solution HCl 12M - HF 0.05M at 298.15+-0.05 K. The standard formation enthalpies of the ionic species Pa(IV) and Pa(V) are respectively equal to -672+-15 kJ.mol -1 and -821+-15 kJ.mol -1

The vapor pressure and enthalpy of vaporization of M-xylene

International Nuclear Information System (INIS)

Rothenberg, S.J.; Seiler, F.A.; Bechtold, W.E.; Eidson, A.F.

1988-01-01

We measured the vapor pressure of m-xylene over the temperature range 273 to 293 deg K with a single-sided capacitance manometer. The enthalpy of vaporization was 42.2 ± 0.1 (SE) kj/ g·mol. Combining our own data with previously published data, we recommend using the values 42.0, 40.6, and 39.1 (± 0.1) (SE) kjg·mol for the enthalpy of vaporization of m-xylene at 300, 340, and 380 deg. K, respectively, and a value for the change in heat capacity on vaporization (ΔCpdeg.) of 35 ± 3 (SE) J/g·mol·K over the temperature range studied. (author)

Calorimetric measurement of the enthalpy of extraction of uranyl nitrate by tri-n-amyl phosphate

International Nuclear Information System (INIS)

Srinivasan, T.G.; Vasudeva Rao, P.R.; Venugopal, V.; Sood, D.D.

2002-01-01

Enthalpy of extraction of uranyl nitrate by tri n-amyl phosphate (TAP) and its solutions in n-dodecane has been directly measured by solution calorimetry for the first time. Measurements have been made at 303±1 K, in both forward as well as the reverse extraction modes. The enthalpies of the accompanying reactions such as the dilution of the uranyl nitrate in the aqueous phase, the hydration of TAP, the mixing of TAP and n-dodecane, the mixing of the metal-solvate (UO 2 (NO 3 ) 2 ·2TAP) and n-dodecane and mixing of the metal-solvate and TAP have also been independently measured and used to derive both the equilibrium state enthalpies and the standard state enthalpies for the extraction. Two distinct standard states have been used for the organic phase, viz., 1) all solutes infinitely diluted in diluent (ΔH*) and 2) all solutes infinitely diluted in the water saturated extractant (ΔH 0 ). The results have been compared with the enthalpies of extraction measured by employing the temperature dependence of the distribution ratio as well as calorimetry reported in the literature for extraction of uranyl nitrate by TAP and TBP. (author)

Building blocks for ionic liquids: Vapor pressures and vaporization enthalpies of 1-(n-alkyl)-imidazoles

International Nuclear Information System (INIS)

Emel'yanenko, Vladimir N.; Portnova, Svetlana V.; Verevkin, Sergey P.; Skrzypczak, Andrzej; Schubert, Thomas

2011-01-01

Highlights: → We measured vapor pressures of the 1-(n-alkyl)-imidazoles by transpiration method. → Variations on the alkyl chain length n were C 3 , C 5 -C 7 , and C 9 -C 10 . → Enthalpies of vaporization were derived from (p, T) dependencies. → Enthalpies of vaporization at 298.15 K were linear dependent on the chain length. - Abstract: Vapor pressures of the linear 1-(n-alkyl)-imidazoles with the alkyl chain C 3 , C 5 -C 7 , and C 9 -C 10 have been measured by the transpiration method. The molar enthalpies of vaporization Δ l g H m of these compounds were derived from the temperature dependencies of vapor pressures. A linear correlation of enthalpies of vaporization Δ l g H m (298.15 K) of the 1-(n-alkyl)-imidazoles with the chain length has been found.

Modified enthalpy method for the simulation of melting and ...

Indian Academy of Sciences (India)

These include the implicit time stepping method of Voller & Cross. (1981), explicit enthalpy method of Tacke (1985), centroidal temperature correction method ... In variable viscosity method, viscosity is written as a function of liquid fraction.

PREDICTION OF THE MIXING ENTHALPIES OF BINARY LIQUID ALLOYS BY MOLECULAR INTERACTION VOLUME MODEL

Institute of Scientific and Technical Information of China (English)

H.W.Yang; D.P.Tao; Z.H.Zhou

2008-01-01

The mixing enthalpies of 23 binary liquid alloys are calculated by molecular interaction volume model (MIVM), which is a two-parameter model with the partial molar infinite dilute mixing enthalpies. The predicted values are in agreement with the experimental data and then indicate that the model is reliable and convenient.

Determination of the protonation enthalpy of humic acid by calorimetric titration technique

International Nuclear Information System (INIS)

Kimuro, Shingo; Kirishima, Akira; Sato, Nobuaki

2015-01-01

Graphical abstract: The thermodynamic quantities of protonation of humic acid were determined by the combination of potentiometric titration and calorimetric titration. It was observed that the protonation enthalpy and Gibbs free energy had been affected by pH of solution. As a result, the thermodynamics of the protonation reaction of humic acid is influenced by the polyelectrolyte effect and the heterogeneity. - Highlights: • We applied calorimetric titration technique to the protonation of humic acid. • The thermodynamic quantities of protonation of humic acid were determined. • The protonation enthalpy of humic acid is affected by the heterogeneity. • Gibbs free energy of the protonation is affected by the polyelectrolyte effect. - Abstract: In this study, the calorimetric titration technique was used to determine the protonation enthalpy of two reference humic acids and polyacrylic acid. First, we obtained the apparent protonation constant of two kinds of humic acid purchased from IHSS (International Humic Substances Society) and polyacrylic acid by potentiometric titration. Second, we obtained the protonation enthalpy of them by calorimetric titration. The protonation enthalpy of humic acid was affected by pH and the ionic strength of bulk solution. From the comparison of ΔH between humic acid and polyacrylic acid, it was concluded that the pH dependence of ΔH is attributed to the heterogeneity of humic acid. And ΔH of phenolic hydroxyl group in humic acid is strongly influenced by the electric double layer of humic acid’s surface. This is considered to be a reason of the ionic strength dependence of ΔH. On the other hand, Gibbs free energy of the protonation of humic acid is affected by the electrostatic attraction with the progress of dissociation of functional groups such as carboxyl group and phenolic hydroxyl group. Consequently, the thermodynamics of the protonation of humic acid is affected by the polyelectrolyte effect and the

Vapor pressures and vaporization enthalpy of codlemone by correlation gas chromatography

International Nuclear Information System (INIS)

Schultz, Shannon M.; Harris, Harold H.; Chickos, James S.

2015-01-01

Highlights: • The vaporization enthalpy of codlemone has been evaluated. • The vapor pressure of codlemone has been evaluated from T = (298.15 to T b ) K. • Vapor pressures for the 1-alkanols standards are available from T = (298.15 to 500) K. - Abstract: The vapor pressure and vaporization enthalpy of codlemone (trans, trans 8,10-dodecadien-1-ol), the female sex hormone of the codling moth is evaluated by correlation gas chromatography using a series of saturated primary alcohols as standards. A vaporization enthalpy of (92.3 ± 2.6) kJ · mol −1 and a vapor pressure, p/Pa = (0.083 ± 0.012) were evaluated at T = 298.15 K. An equation for the evaluation of vapor pressure from ambient temperature to boiling has been derived by correlation for codlemone. The calculated boiling temperature of T B = 389 K at p = 267 Pa is within the temperature range reported in the literature. A normal boiling temperature of T B = (549.1 ± 0.1) K is also estimated by extrapolation

Energetic studies of urea derivatives: Standard molar enthalpy of formation of 3,4,4'-trichlorocarbanilide

Energy Technology Data Exchange (ETDEWEB)

Ribeiro da Silva, Maria das Dores M.C. [Centro de Investigacao em Quimica, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Ribeiro da Silva, Manuel A.V., E-mail: risilva@fc.up.p [Centro de Investigacao em Quimica, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Freitas, Vera L.S. [Centro de Investigacao em Quimica, Department of Chemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal); Roux, Maria Victoria; Jimenez, Pilar; Davalos, Juan Z. [Instituto de Quimica Fisica ' Rocasolano' , C.S.I.C., Serrano, 119, E-28006 Madrid (Spain); Cabildo, Pilar; Claramunt, Rosa M. [Departamento de Quimica Organica y Bio-Organica, Facultad de Ciencias, UNED, Senda del Rey, 9, E-28040 Madrid (Spain); Pinilla, Elena; Rosario Torres, M. [Departamento de Quimica Inorganica I, Laboratorio de Difraccion de Rayos X, Facultad de Ciencias Quimicas, E-28040 Madrid (Spain); Elguero, Jose [Instituto de Quimica Medica, C.S.I.C., Juan de la Cierva, 3, E-28006 Madrid (Spain)

2010-04-15

Thermochemical and thermophysical studies have been carried out for crystalline 3,4,4'-trichlorocarbanilide. The standard (p{sup o} = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, for the crystalline 3,4,4'-trichlorocarbanilide (TCC) was experimentally determined using rotating-bomb combustion calorimetry, as -(234.6 +- 8.3) kJ . mol{sup -1}. The standard enthalpy of sublimation, at the reference temperature of 298.15 K, was measured by the vacuum drop microcalorimetric technique, using a High Temperature Calvet Microcalorimeter as (182.1 +- 1.7) kJ . mol{sup -1}. These two thermochemical parameters yielded the standard molar enthalpy of formation of the studied compound, in the gaseous phase, at T = 298.15 K, as -(52.5 +- 8.5) kJ . mol{sup -1}. This parameter was also calculated by computational thermochemistry at M05-2X/6-311++G** and B3LYP/6-311++G(3df, 2p) levels, with a deviation less than 4.5 kJ . mol{sup -1} from experimental value. Moreover, the thermophysical study was made by differential scanning calorimetry, DSC, over the temperature interval between T = 263 K and its onset fusion temperature, T = (527.5 +- 0.4) K. A solid-solid phase transition was found at T = (428 +- 1) K, with the enthalpy of transition of (6.1 +- 0.1) kJ . mol{sup -1}. The X-ray crystal structure of TCC was determined and the three-centred N-H...O=C hydrogen bonds present analyzed.

Vaporization enthalpies of imidazolium based ionic liquids. A thermogravimetric study of the alkyl chain length dependence

International Nuclear Information System (INIS)

Verevkin, Sergey P.; Zaitsau, Dzmitry H.; Emel’yanenko, Vladimir N.; Ralys, Ricardas V.; Yermalayeu, Andrei V.; Schick, Christoph

2012-01-01

Highlights: ► Enthalpies of vaporization of ionic liquids were measured with thermogravimetry. ► We studied 1-alkyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide. ► The linear alkyl chain length was 4, 6, 8, 10, 12, 14, 16, and 18 C-atoms. ► A linear dependence on the chain length of the alkyl-imidazolium cation was found. - Abstract: Vaporization enthalpies for a series of ten ionic liquids (ILs) 1-alkyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide [C n mim][NTf 2 ], with the alkyl chain length n = 4, 6, 8, 10, 12, 14, 16, and 18 were determined using the thermogravimetric method. An internally consistent set of experimental data and vaporization enthalpies at 540 K was obtained. Vaporization enthalpies at 540 K have shown a linear dependence on the chain length of the alkyl-imidazolium cation in agreement with the experimental results measured previously with a quartz crystal microbalance. Ambiguity of Δ l g C pm o -values required for the extrapolation of experimental vaporization enthalpies to the reference temperature 298 K has been discussed.

Dominant Alcohol-Protein Interaction via Hydration-Enabled Enthalpy-Driven Binding Mechanism

Science.gov (United States)

Chong, Yuan; Kleinhammes, Alfred; Tang, Pei; Xu, Yan; Wu, Yue

2015-01-01

Water plays an important role in weak associations of small drug molecules with proteins. Intense focus has been on binding-induced structural changes in the water network surrounding protein binding sites, especially their contributions to binding thermodynamics. However, water is also tightly coupled to protein conformations and dynamics, and so far little is known about the influence of water-protein interactions on ligand binding. Alcohols are a type of low-affinity drugs, and it remains unclear how water affects alcohol-protein interactions. Here, we present alcohol adsorption isotherms under controlled protein hydration using in-situ NMR detection. As functions of hydration level, Gibbs free energy, enthalpy, and entropy of binding were determined from the temperature dependence of isotherms. Two types of alcohol binding were found. The dominant type is low-affinity nonspecific binding, which is strongly dependent on temperature and the level of hydration. At low hydration levels, this nonspecific binding only occurs above a threshold of alcohol vapor pressure. An increased hydration level reduces this threshold, with it finally disappearing at a hydration level of h~0.2 (g water/g protein), gradually shifting alcohol binding from an entropy-driven to an enthalpy-driven process. Water at charged and polar groups on the protein surface was found to be particularly important in enabling this binding. Although further increase in hydration has smaller effects on the changes of binding enthalpy and entropy, it results in significant negative change in Gibbs free energy due to unmatched enthalpy-entropy compensation. These results show the crucial role of water-protein interplay in alcohol binding. PMID:25856773

The vapor pressure and enthalpy of vaporization of M-xylene

Energy Technology Data Exchange (ETDEWEB)

Rothenberg, S J; Seiler, F A; Bechtold, W E; Eidson, A F

1988-12-01

We measured the vapor pressure of m-xylene over the temperature range 273 to 293 deg K with a single-sided capacitance manometer. The enthalpy of vaporization was 42.2 {+-} 0.1 (SE) kj/ g{center_dot}mol. Combining our own data with previously published data, we recommend using the values 42.0, 40.6, and 39.1 ({+-} 0.1) (SE) kjg{center_dot}mol for the enthalpy of vaporization of m-xylene at 300, 340, and 380 deg. K, respectively, and a value for the change in heat capacity on vaporization ({delta}Cpdeg.) of 35 {+-} 3 (SE) J/g{center_dot}mol{center_dot}K over the temperature range studied. (author)

Enthalpy - entropy compensation effect in grain boundary phenomena

Czech Academy of Sciences Publication Activity Database

Lejček, Pavel

2005-01-01

Roč. 96, č. 10 (2005), s. 1129-1133 ISSN 0044-3093 R&D Projects: GA MPO(CZ) FF-P2/053 Institutional research plan: CEZ:AV0Z10100520 Keywords : compensation effect * enthalpy * entropy * thermodynamics * grain boundary Subject RIV: BJ - Thermodynamics Impact factor: 0.842, year: 2005

Enthalpies of mixing in the ternary system aluminium chloride - potassium chloride - aluminium chloride monoamine

Energy Technology Data Exchange (ETDEWEB)

Hatem, G.; Gaune-Escard, M.; Bros, J.P. (Aix-Marseille-2 Univ., 13 - Marseille (France). Centre de Saint Jerome); Ostvold, T. (Norges Tekniske Hoegskole, Trondheim (Norway). Inst. for Uorganisk Kjemi)

1988-06-01

Quasi binary enthalpy of mixing experiments have been performed in the ternary liquid system AlCl{sub 3}-AlCl{sub 3}NH{sub 3}-KCl by mixing AlCl{sub 3} + KCl with AlCl{sub 3}NH{sub 3} keeping the ratio X{sub AlCl3}/X{sub KCl} = 1.125, 1.5 and 2.0, respectively. At X{sub AlCl3}NH{sub 3} = 0.5 and T = 270deg C the enthalpies of mixing were {approx equal} -430 J mol{sup -1} for all the quasi-binaries studied. The new enthalpy data are not fully consistent with published vapour pressure data and thermodynamic model calculations. (orig.).

Determination of standard molar enthalpies of formation of SrMoO4 micro/nano structures

International Nuclear Information System (INIS)

Guo, Yunxiao; Fan, Gaochao; Huang, Zaiyin; Sun, Jilong; Wang, Lude; Wang, Tenghui; Chen, Jie

2012-01-01

Graphical abstract: Schematic illustration of thermochemical cycle between the nano and bulk reaction systems. Highlights: ► A thermochemical cycle was designed. ► Relationship of standard molar enthalpies of formation between micro/nano and bulk SrMoO 4 was gained. ► Microcalorimetry was used as a supplementary technology. ► Standard molar enthalpies of formation of the synthesized micro/nano SrMoO 4 were obtained. ► This novel approach can be used to other micro/nano materials. - Abstract: SrMoO 4 micro/nano structures were prepared by a simple reverse microemulsion method and were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscope (SEM). In order to associate standard molar enthalpies of formation of nano SrMoO 4 with bulk SrMoO 4 , the relationship of them was obtained through designing a thermochemical cycle according to thermodynamic potential function method. Combined with microcalorimetry, the standard molar enthalpies of formation of the synthesized micro/nano SrMoO 4 at 298.15 K were gained in this paper. And the variation of standard molar enthalpies of formation of micro/nano SrMoO 4 with different morphologies and sizes was discussed.

Modified solution calorimetry approach for determination of vaporization and sublimation enthalpies of branched-chain aliphatic and alkyl aromatic compounds at T = 298.15 K

International Nuclear Information System (INIS)

Varfolomeev, Mikhail A.; Novikov, Vladimir B.; Nagrimanov, Ruslan N.; Solomonov, Boris N.

2015-01-01

Highlights: • Solution enthalpies of 18 branching-chain alkyl aromatic and aliphatic compounds in cyclohexane were measured. • Group contributions to the enthalpy of solvation due to branching and substitution in carbon chain were evaluated. • Modified solution calorimetry based approach for determination of vaporization/sublimation enthalpies was proposed. • This approach provides vaporization/sublimation enthalpies directly at T = 298.15 K. • Vaporization/sublimation enthalpies of 35 branched-chain alkyl aromatic and aliphatic compounds were determined. - Abstract: The enthalpies of solution, solvation and vaporization/sublimation are interrelated values combined in the simplest thermodynamic circle. Hence, experimental determination of vaporization/sublimation enthalpy can be substituted by experimentally simpler determination of solution enthalpy when solvation enthalpy is known. Previously it was found that solvation enthalpies of a wide range of unbranched aliphatic and aromatic solutes in saturated hydrocarbons are in good linear correlation with their molar refraction values. This allows to estimate the vaporization/sublimation enthalpy of any unbranched organic compound from its solution enthalpy in saturated hydrocarbon and molar refraction. In the present work this approach was modified for determination of vaporization/sublimation enthalpy of branched-chain alkyl aromatic and aliphatic compounds. Group contributions to the enthalpy of solvation due to the branching of carbon chain were evaluated. Enthalpies of solution at infinite dilution of 18 branched-chain aliphatic and alkyl aromatic compounds were measured at T = 298.15 K. Vaporization/sublimation enthalpies for 35 branched aliphatic and alkyl aromatic compounds were determined by using modified solution calorimetry approach. These values are in good agreement with available literature data on vaporization/sublimation enthalpies obtained by conventional methods.

Kinetics and enthalpy of crystallization of uric acid dihydrate

International Nuclear Information System (INIS)

Sádovská, Galina; Honcová, Pavla; Sádovský, Zdeněk

2013-01-01

Highlights: • The kinetic constant and growth order of crystallization of uric acid dihydrate was calculated. • The equation describing first-order crystal growth was derived. • The enthalpy of crystallization of uric acid dihydrate was determined. - Abstract: The kinetics of crystallization of uric acid dihydrate in aqueous solution with a constant ionic strength 0.3 mol dm −3 NaCl and at thermodynamic and physiological temperature (25 and 37 °C) was studied using isoperibolic reaction twin calorimeter. The enthalpy of crystallization Δ cr H = −47.3 ± 0.9 and −46.2 ± 1.4 kJ mol −1 and kinetic constant k g = 2.0 × 10 −8 and 9.6 × 10 −8 m 4 s −1 mol −1 were determined at 25 and 37 °C, respectively

Standard molar enthalpies of formation of 1-methyl-2-piperidinemethanol, 1-piperidineethanol, and 2-piperidineethanol

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Cabral, Joana I.T.A.

2006-01-01

The standard (p o =0.1MPa) molar enthalpies of combustion, Δ c H m o , for the liquid compounds 1-methyl-2-piperidinemethanol, 1-piperidineethanol, and 2-piperidineethanol, were measured by static bomb calorimetry, in oxygen, at T=298.15K. The standard molar enthalpies of vaporization, at T=298.15K, of these three liquid compounds were determined by Calvet microcalorimetry. -Δ c H m o (l)/(kJ.mol -1 )Δ l g H m o /(kJ.mol -1 )1-Methyl-2-piperidinemethanol4598.3+/-1.868. 22+/-0.711-Piperidineethanol4595.2+/-1.764.18+/-0.812 -Piperidineethanol4566.2+/-1.375.24+/-0.52 These values, were used to derive the standard molar enthalpies of formation of the compounds, at T=298.15K, in their liquid and gaseous phase, respectively. The derived standard molar enthalpies of formation, in the gaseous state, are analyzed in terms of enthalpic increments and interpreted in terms of molecular structure.

Outlook on principles for designing integrated and cascade use of low enthalpy geothermal energy in Albania

International Nuclear Information System (INIS)

Frasheri, Alfred

2000-01-01

In the countries of Western Europe, USA and Japan, the technologies of a new generation evolved to exploit high and low enthalpy geothermal sources and mineral waters. There are great experiences for modern complex exploitation of these resources, which increase natural wealth values, in European Community Countries. In Albania, rich in geothermal resources of low enthalpy and mineral waters, similar new technologies have been either partly developed or remain still untouched. Modern complex exploitation is very rare phenomena. Large numbers of geothermal energy of high and low enthalpy resources, a lot of mineral water sources and some CO 2 gas reservoirs represent the base for successfully application of modern technologies in Albania, to achieve economic effectively and success of complex exploitation. Actuality, there are many geothermal, hydrogeological, hydrochemical, biological and medical investigations and studies of thermal and mineral water resources carried out in Albania. Generally, these investigations and studies are separated each from the other. Their information and data will serve for studies and evaluations in Albania regional scale. These studies and evaluations are necessary to well know in regional plane the thermal and mineral water resources potential and geothermal market of the Albania. According to results of these new studies, the evaluation for the perspective level of the best areas in country will be necessary. After the evaluation is possible to start investments in these areas. These investments will be profitable in a short period of time. Integrated and cascade use of geothermal energy of low enthalpy it is important condition for profitable investment. In Albania, there are several geothermal energy sources that can be used. Such geothermal energy sources are natural thermal water springs and deep wells with a temperature of up to 65,5 o C. Deep abandoned oil wells can be used as 'Vertical Earth Heat Probe'. The integrated and

Characteristics of low-enthalpy geothermal applications in Greece

International Nuclear Information System (INIS)

Andritsos, N.; Dalabakis, P.; Karydakis, G.; Kolios, N.; Fytikas, M.

2011-01-01

The paper offers a brief overview of the current direct geothermal uses in Greece and discusses their characteristics, with emphasis to the economical and technical problems encountered. Greece holds a prominent place in Europe regarding the existence of promising geothermal resources (both high and low-enthalpy), which can be economically exploited. Currently, no geothermal electricity is produced in Greece. The installed capacity of direct uses at the end of 2009 is estimated at about 155 MW t , exhibiting an increase of more than 100% compared to the figures reported at the World Geothermal Congress 2005. The main uses, in decreasing share, are geothermal heat pumps, swimming and balneology, greenhouse heating and soil warming. Earth-coupled and groundwater (or seawater) heat pumps have shown a drastic expansion during the past 2-3 years, mainly due to high oil prices two years ago and easing of the license requirements for drilling shallow wells. (author)

The mixing enthalpy of the Pb-Te system

International Nuclear Information System (INIS)

Blachnik, R.; Gather, B.

1983-01-01

The thermodynamic properties of molten Pb-Te alloys were measured at 1210 K in a Setaram-Calvet-type calorimeter. It was found that the enthalpy of mixing has a pronounced minimum of -26250 +- 950 J mol - 1 at 52 mol.%Te. The results obtained are discussed in terms of an ionic model. (Auth.)

Extension of the segment-based Wilson and NRTL models for correlation of excess molar enthalpies of polymer solutions

International Nuclear Information System (INIS)

Sadeghi, Rahmat

2005-01-01

The polymer Wilson model and the polymer NRTL model have been extended for the representation of the excess enthalpy of multicomponent polymer solutions. Applicability of obtained equations in the correlation of the excess enthalpies of polymer solutions has been examined. It is found that the both models are suitable models in representing the published excess enthalpy data for the tested polymer solutions

Equivalent Temperature-Enthalpy Diagram for the Study of Ejector Refrigeration Systems

Directory of Open Access Journals (Sweden)

Mohammed Khennich

2014-05-01

Full Text Available The Carnot factor versus enthalpy variation (heat diagram has been used extensively for the second law analysis of heat transfer processes. With enthalpy variation (heat as the abscissa and the Carnot factor as the ordinate the area between the curves representing the heat exchanging media on this diagram illustrates the exergy losses due to the transfer. It is also possible to draw the paths of working fluids in steady-state, steady-flow thermodynamic cycles on this diagram using the definition of “the equivalent temperature” as the ratio between the variations of enthalpy and entropy in an analyzed process. Despite the usefulness of this approach two important shortcomings should be emphasized. First, the approach is not applicable for the processes of expansion and compression particularly for the isenthalpic processes taking place in expansion valves. Second, from the point of view of rigorous thermodynamics, the proposed ratio gives the temperature dimension for the isobaric processes only. The present paper proposes to overcome these shortcomings by replacing the actual processes of expansion and compression by combinations of two thermodynamic paths: isentropic and isobaric. As a result the actual (not ideal refrigeration and power cycles can be presented on equivalent temperature versus enthalpy variation diagrams. All the exergy losses, taking place in different equipments like pumps, turbines, compressors, expansion valves, condensers and evaporators are then clearly visualized. Moreover the exergies consumed and produced in each component of these cycles are also presented. The latter give the opportunity to also analyze the exergy efficiencies of the components. The proposed diagram is finally applied for the second law analysis of an ejector based refrigeration system.

The effect of a fourth element (Co, Cu, Fe, Pd) on the standard enthalpy of formation of the Heusler compound Ni{sub 2}MnSn

Energy Technology Data Exchange (ETDEWEB)

Yin, Ming, E-mail: myin1@hawk.iit.edu; Nash, Philip

2016-05-15

The standard enthalpies of formation of quaternary Heusler compounds (X, Ni){sub 2}MnSn (X = Co, Cu, Fe, Pd) were investigated experimentally using high temperature direct reaction calorimetry. Lattice parameters of these compounds were determined using X-ray diffraction analysis. Microstructures were identified using scanning electron microscopy and energy dispersive spectroscopy. The effect of an additional X element on the standard enthalpy of formation of the Heusler compound Ni{sub 2}MnSn is discussed. - Highlights: • Enthalpies of formation of (X,Ni){sub 2}YZ (X = Co, Cu, Fe, Pd) were measured by drop calorimeters. • Magnetic contribution to enthalpy of formation plays an important role. • Introducing a fourth element could stabilize an unstable Heusler structure. • Lattice parameters do not necessarily obey the Vegard's law. • It is possible to tailor properties of Heusler compounds with enough background information.

Kinetics and enthalpy of crystallization of uric acid dihydrate

Energy Technology Data Exchange (ETDEWEB)

Sádovská, Galina, E-mail: galina.sadovska@upce.cz; Honcová, Pavla; Sádovský, Zdeněk

2013-08-20

Highlights: • The kinetic constant and growth order of crystallization of uric acid dihydrate was calculated. • The equation describing first-order crystal growth was derived. • The enthalpy of crystallization of uric acid dihydrate was determined. - Abstract: The kinetics of crystallization of uric acid dihydrate in aqueous solution with a constant ionic strength 0.3 mol dm{sup −3} NaCl and at thermodynamic and physiological temperature (25 and 37 °C) was studied using isoperibolic reaction twin calorimeter. The enthalpy of crystallization Δ{sub cr}H = −47.3 ± 0.9 and −46.2 ± 1.4 kJ mol{sup −1}and kinetic constant k{sub g} = 2.0 × 10{sup −8} and 9.6 × 10{sup −8} m{sup 4} s{sup −1} mol{sup −1} were determined at 25 and 37 °C, respectively.

Vapour pressures and enthalpies of vapourization of a series of the linear aliphatic nitriles

International Nuclear Information System (INIS)

Emel'yanenko, Vladimir N.; Verevkin, Sergey P.; Koutek, Bohumir; Doubsky, Jan

2005-01-01

Vapour pressures and the molar enthalpies of vapourization ΔlgHm-bar of the linear aliphatic nitriles C 7 -C 17 have been determined by the transpiration method. Kovat's indices of these compounds were measured by capillary gas-chromatography. A linear correlation of enthalpies of vapourization ΔlgHm-bar at T=298.15 K of the nitriles studied with the Kovats indices has been found

Examination of hydrogen-bonding interactions between dissolved solutes and alkylbenzene solvents based on Abraham model correlations derived from measured enthalpies of solvation

Energy Technology Data Exchange (ETDEWEB)

Varfolomeev, Mikhail A.; Rakipov, Ilnaz T. [Chemical Institute, Kazan Federal University, Kremlevskaya 18, Kazan 420008 (Russian Federation); Acree, William E., E-mail: acree@unt.edu [Department of Chemistry, 1155 Union Circle # 305070, University of North Texas, Denton, TX 76203-5017 (United States); Brumfield, Michela [Department of Chemistry, 1155 Union Circle # 305070, University of North Texas, Denton, TX 76203-5017 (United States); Abraham, Michael H. [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

2014-10-20

Highlights: • Enthalpies of solution measured for 48 solutes dissolved in mesitylene. • Enthalpies of solution measured for 81 solutes dissolved in p-xylene. • Abraham model correlations derived for enthalpies of solvation of solutes in mesitylene. • Abraham model correlations derived for enthalpies of solvation of solutes in p-xylene. • Hydrogen-bonding enthalpies reported for interactions of aromatic hydrocarbons with hydrogen-bond acidic solutes. - Abstract: Enthalpies of solution at infinite dilution of 48 organic solutes in mesitylene and 81 organic solutes in p-xylene were measured using isothermal solution calorimeter. Enthalpies of solvation for 92 organic vapors and gaseous solutes in mesitylene and for 130 gaseous compounds in p-xylene were determined from the experimental and literature data. Abraham model correlations are determined from the experimental enthalpy of solvation data. The derived correlations describe the experimental gas-to-mesitylene and gas-to-p-xylene solvation enthalpies to within average standard deviations of 1.87 kJ mol{sup −1} and 2.08 kJ mol{sup −1}, respectively. Enthalpies of X-H⋯π (X-O, N, and C) hydrogen bond formation of proton donor solutes (alcohols, amines, chlorinated hydrocarbons etc.) with mesitylene and p-xylene were calculated based on the Abraham solvation equation. Obtained values are in good agreement with the results determined using conventional methods.

Measurement of the enthalpies of vaporization and sublimation of solids aromatic hydrocarbons by differential scanning calorimetry

International Nuclear Information System (INIS)

Rojas, Aaron; Orozco, Eulogio

2003-01-01

An experimental procedure is proposed for direct measurement of the heat involved in the vaporization of a solid organic compound above its normal melting temperature. This technique consists on the fusion of a solid aromatic hydrocarbon, which is then vaporized by a sudden decrease of the pressure. The direct register of heat flow as function of time by differential scanning calorimetry allows the quantifying of the enthalpy of vaporization of compounds such as phenanthrene, β-naphthol, pyrene, and anthracene. Enthalpies of vaporization were measured in an isothermal mode over a range of temperatures from 10 to 20 K above the melting temperatures of each compound, while enthalpies of fusion were determined from separate experiments performed in a scanning mode. Enthalpies of sublimation are computed from results of fusion and vaporization, and then compared with results from the literature, which currently are obtained by calorimetric or indirect techniques

High Altitude Clear Air Turbulence Project

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Air Force Flight Dynamics Laboratory conducted the High Altitude Clear Air Turbulence Project in the mid 1960s with the intention of better understanding air...

Experimental and theoretical excess molar enthalpies of ternary and binary mixtures containing 2-Methoxy-2-Methylpropane, 1-propanol, heptane

International Nuclear Information System (INIS)

Mato, Marta M.; Cebreiro, Susana M.; Paz Andrade, María Inmaculada; Legido, José Luis

2013-01-01

Highlights: • Experimental enthalpies for the ternary system MTBE + propanol + heptane were measured. • No experimental ternary values were found in the currently available literature. • Experimental enthalpies for the binary system propanol + heptane were measured. • Excess molar enthalpies are positive over the whole range of composition. • The ternary contribution is also positive, and the representation is asymmetric. -- Abstract: Excess molar enthalpies, at the temperature of 298.15 K and atmospheric pressure, have been measured for the ternary system {x 1 2-Methoxy-2-Methylpropane (MTBE) + x 2 1-propanol + (1 − x 1 − x 2 ) heptane}, over the whole composition range. Also, experimental data of excess molar enthalpy for the involved binary mixture {x 1-propanol + (1 − x) heptane} at the 298.15 K and atmospheric pressure, are reported. We are not aware of any previous experimental measurement of excess enthalpy in the literature for the ternary system presented in this study. Values of the excess molar enthalpies were measured using a Calvet microcalorimeter. The ternary contribution to the excess enthalpy was correlated with the equation due to Morris et al. (1975) [15], and the equation proposed by Myers–Scott (1963) [14] was used to fitted the experimental binary mixture measured in this work. Additionally, the experimental results are compared with the estimations obtained by applying the group contribution model of UNIFAC, in the versions of Larsen et al. (1987) [16] and Gmehling et al. (1993) [17]. Several empirical expressions for estimating ternary properties from binary results were also tested

Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling

International Nuclear Information System (INIS)

Efimova, Anastasia; Pinnau, Sebastian; Mischke, Matthias; Breitkopf, Cornelia; Ruck, Michael; Schmidt, Peer

2014-01-01

Graphical abstract: - Highlights: • Inorganic salt hydrates. • Latent heat thermal energy storage. • Thermal behavior of melting and crystallization. • Cycling stability. • Nucleation. - Abstract: Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 °C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO 3 ) 2 ·6H 2 O, Mn(NO 3 ) 2 ·4H 2 O, and KNO 3 with the melting temperature range 18–21 °C and the enthalpy of fusion of about 110 kJ kg −1 . Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation

Vapor pressures and sublimation enthalpies of novel bicyclic heterocycle derivatives

International Nuclear Information System (INIS)

Blokhina, Svetlana V.; Ol’khovich, Marina V.; Sharapova, Angelica V.; Perlovich, German L.; Proshin, Alexey N.

2014-01-01

Highlights: • The vapor pressures of novel bicyclo-derivatives of amine were measured. • Thermodynamic functions of sublimation were calculated. • The influence of substituent structure and chemical nature on the vapor pressure was studied. -- Abstract: The vapor pressures of five novel bicyclic heterocycle derivatives were measured over the temperature 341.15 to 396.15 K using the transpiration method by means of an inert gas carrier. From these results the standard enthalpies and Gibbs free energies of sublimation at the temperature 298.15 K were calculated. The effects of alkyl- and chloro-substitutions on changes in the thermodynamic functions have been investigated. Quantitative structure–property relationship on the basis HYBOT physico-chemical descriptors for biologically active compounds have been developed to predict the sublimation enthalpies and Gibbs free energies of the compounds studied

Enthalpy and high temperature relaxation kinetics of stable vapor-deposited glasses of toluene

International Nuclear Information System (INIS)

Bhattacharya, Deepanjan; Sadtchenko, Vlad

2014-01-01

Stable non-crystalline toluene films of micrometer and nanometer thicknesses were grown by vapor deposition at distinct rates and probed by fast scanning calorimetry. Fast scanning calorimetry is shown to be extremely sensitive to the structure of the vapor-deposited phase and was used to characterize simultaneously its kinetic stability and its thermodynamic properties. According to our analysis, transformation of vapor-deposited samples of toluene during heating with rates in excess 10 5 K s −1 follows the zero-order kinetics. The transformation rate correlates strongly with the initial enthalpy of the sample, which increases with the deposition rate according to sub-linear law. Analysis of the transformation kinetics of vapor-deposited toluene films of various thicknesses reveal a sudden increase in the transformation rate for films thinner than 250 nm. The change in kinetics seems to correlate with the surface roughness scale of the substrate. The implications of these findings for the formation mechanism and structure of vapor-deposited stable glasses are discussed

Standard Molar Enthalpy of Formation of RE(C5H8NS2)3(o-phen)

Institute of Scientific and Technical Information of China (English)

MENG Xiang-Xin; GAO Sheng-Li; CHEN San-Ping; YANG Xu-Wu; XIE Gang; SHI Qi-Zhen

2005-01-01

Five solid ternary complexes of RE(C5H8NS2)3(o-phen) (RE=Ho, Er, Tm, Yb, Lu) have been synthesized in absolute ethanol by rare earth chloride low hydrate reacting with the mixed ligands of ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline·H2O (o-phen·H2O) in the ordinary laboratory atmosphere without any cautions against moisture or air. IR spectra of the complexes showed that the RE3+ coordinated with six sulfur atoms of three PDC- and two nitrogen atoms of o-phen·H2O. It was assumed that the coordination number of RE3+was eight. The constant-volume combustion energies of the complexes, △cU, were determined as (-16788.46±7.74), (- 15434.53± 8.28), (- 15287.807.31), (- 15200.50±7.22) and (- 15254.34±6.61) kJ·mol-1, respectively, by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, △cH m,and standard molar enthalpies of formation, △fH m, were calculated as (-16803.95 ±7.74), (-15450.02±8.28),(-15303.29±9.28), (-15215.99±7.22), (-15269.83±6.61) kJ·mol-1 and (-1115.42±8.94), (-2477.80±9.15), (-2619.95 ±10.44), (-2670.17 ± 8.22), ( -2650.06± 8.49) kJ·mol-1, respectively.

Method of determining the enthalpy and moisture content of wet steam

International Nuclear Information System (INIS)

Silvestri, G.J. Jr.

1991-01-01

This patent describes a nuclear powered multi-stage steam turbine system wherein steam at higher than atmospheric pressure is introduced into the turbine system at a high pressure turbine element and thereafter flows through a series of turbine elements at successively decreasing pressures, wherein portions of the steam are extracted from the turbine elements at a plurality of lower pressure points and the steam is finally exhausted at a lowest pressure point, the method of determining moisture content and enthalpy of steam at a selected pressure point. It comprises sampling a small quantity of steam at the selected pressure point; super heating the steam sample to a single-phase state by reducing its pressure and bottling it in a closed measuring chamber whereby the flow energy of the sample is converted into internal energy; measuring the pressure of the steam sample within the chamber; determining the sonic velocity of the steam sample by passing a sound wave through the sample from a transmitter to a receiver located at a known distance from the transmitter and measuring the time required for the sound wave to travel from transmitter to receiver; and utilizing the measured pressure and sonic velocity of the steam sample to calculate the moisture content and enthalpy of the steam at the selected pressure point

Vapor pressures and enthalpies of vaporization of a series of γ and δ-lactones by correlation gas chromatography

International Nuclear Information System (INIS)

Kozlovskiy, Mikhail; Gobble, Chase; Chickos, James

2014-01-01

Highlights: • The vaporization enthalpies of γ-octanolactone, γ- and δ-undecanolactone and γ and δ-dodecanolactone are reported. • Equations for predicting the vapor pressures over the temperature range T = (298.15 to 350) K are provided. • Vaporization enthalpies are compared to predicted values. - Abstract: The vaporization enthalpies of γ-octanolactone, γ- and δ-undecanolactone and γ and δ-dodecanolactone used commercially as flavor ingredients are reported as are their vapor pressures over the temperature range T = (298.15 to 350) K. Vaporization enthalpies at T = 298.15 K of: (66.0 ± 3.9), (79.4 ± 4.4), (80.1 ± 4.5), (83.9 ± 4.6), and (84.61 ± 4.7) kJ · mol −1 and vapor pressures also at T = 298.15 K of: (2.8 ± 0.9), (0.12 ± 0.05), (0.09 ± 0.04), (0.04 ± 0.02), and (0.03 ± 0.02) Pa, respectively, have been evaluated by correlation gas chromatography experiments. The vaporization enthalpies of the lactones studied are reproduced within ±0.5 kJ · mol −1 using a group additivity scheme reported previously for γ- and δ-lactones. The vaporization enthalpies of the γ- and δ-lactones are compared to a similar series of ω-lactones

Enthalpies of formation of 5,6-dihydro-5-methyluracil and 5,6-dihydro-6-methyluracil

International Nuclear Information System (INIS)

Amaral, Luísa M.P.F.; Szterner, Piotr; Ribeiro da Silva, Manuel A.V.

2013-01-01

Highlights: • Δ c H m ° of two methyl-5,6-dihydrouracils have been determined by combustion calorimetry. • Vapor pressures were measured by the Knudsen effusion technique. • Gas phase enthalpies of formation of methyl-5,6-dihydrouracils, have been derived. -- Abstract: The standard (p° = 0.1 MPa) molar enthalpy of combustion, Δ c H m ° , of two crystalline compounds, 5,6-dihydro-5-methyluracil and 5,6-dihydro-6-methyluracil, were determined, at T = 298.15 K, using a static bomb combustion calorimeter. The vapor pressures as a function of the temperature were measured for those compounds, by the Knudsen effusion technique, and the standard molar enthalpies of sublimation at the mean temperature of the vapor pressure measurements were derived from the Clausius–Clapeyron equation, and corrected to T = 298.15 K using an estimated value for Δ cr g C p,m ° . These values were used to derive the standard molar enthalpies of formation of the two compounds studied, in the condensed and gaseous phases. Some considerations about the relative stability of the two isomers were made and compared with similar compounds

Reduced energy reqirement for air conditioning by using air diffusion with air flow from floor to ceiling

Energy Technology Data Exchange (ETDEWEB)

Bach, H; Dittes, W; Mangelsdorf, R; Detzer, R; Jungbaeck, E; Fitzner, K; Radtke, W; Soethout, F

1982-02-01

The condition of the air in the occupied zone in airconditioned rooms is influenced by the mixing of supply air with room air. When supplying air from the ceiling there is a mixing all over the room, when supplying from the floor or from desks there is a mixing region only in the lower area. Above this their is warm air from which the return air is drawn. For air supply from below the cooling load can be decreased. In combination with the possible enthalpy difference between room air and supply air this decrease of the cooling load influences the necessary air rate. The interdependence of various air conditioning systems and various air temperatures is shown with a computer program. The load factor for various air distribution system at various cooling loads have been measured in a room of (8 x 5)m/sup 2/ x 3m. Experiments in a smaller model room (scale 1:3) showed how the heat was transported from the mixing region to the stratification region. The theoretically gained influence of the supply air jets of the height of the mixing region and on the load rate could be verified by the experiments. For the design of the fresh air rate, experience has been gained by measurements with tracegas (N/sub 2/O) in a third room. In comparing calculations the annual energy consumption has been computed for a building assuming various air conditioning systems and typical operation data. From experience with the existing systems the conclusions have been drawn how air distribution from floor to ceiling can be installed and operated.

Temperature dependences of saturated vapor pressure and the enthalpy of vaporization of n-pentyl esters of dicarboxylic acids

Science.gov (United States)

Portnova, S. V.; Krasnykh, E. L.; Levanova, S. V.

2016-05-01

The saturated vapor pressures and enthalpies of vaporization of n-pentyl esters of linear C2-C6 dicarboxylic acids are determined by the transpiration method in the temperature range of 309.2-361.2 K. The dependences of enthalpies of vaporization on the number of carbon atoms in the molecule and on the retention indices have been determined. The predictive capabilities of the existing calculation schemes for estimation of enthalpy of vaporization of the studied compounds have been analyzed.

Application of low enthalpy geothermal energy

International Nuclear Information System (INIS)

Stancher, B.; Giannone, G.

2007-01-01

Geothermal energy comes from the superficial layers of the Earth's crust; it can be exploited in several ways, depending on its temperature. Many systems have been developed to use this clean and renewable energy resource. This paper deals with a particular application of low enthalpy geothermal energy in Latisana (district of Udine NE, Italy). The Latisana's indoor stadium is equipped with geothermal plant that uses low temperature water (29-30 0 ) to provide heating. Economic analysis shows that the cost of its plant is comparable to the cost powered by other kinds of renewable energy resources

Dependence of enthalpies of dissolution of β-alanyl-β-alanine on the composition of (water + alcohol) mixtures at 298.15 K

International Nuclear Information System (INIS)

Smirnov, Valeriy I.; Badelin, Valentin G.

2011-01-01

Highlights: · Enthalpies of dissolution of β-alanyl-β-alanine are measured in aqueous methanol, ethanol, 1-propanol and 2-propanol by calorimetry. · Standard values of dissolution and transfer enthalpies of β-alanyl-β-alanine and enthalpy coefficients of pair-wise interactions are calculated. · Dependences of the thermodynamic characteristics of dissolution of β-alanyl-β-alanine on the composition of (water + alcohol) mixtures are determined. - Abstract: The dissolution enthalpies of β-alanyl-β-alanine in aqueous methanol, ethanol, 1-propanol and 2-propanol solutions with an alcohol content up to 0.4 mole fractions have been measured calorimetrically at T = 298.15 K. The standard enthalpies of dissolution, Δ sol H o and transfer, Δ tr H o , of β-alanyl-β-alanine from water into mixed solvents and the enthalpy coefficients of pair-wise interactions, h xy , of β-alanyl-β-alanine with alcohol solvent molecules have been calculated. The results are discussed in terms of solute-solute and solute-solvent interactions.

Thermodynamic state, specific heat, and enthalpy function of saturated UO2 vapor between 3,000 K and 5,000 K

International Nuclear Information System (INIS)

Karow, H.U.

1977-02-01

The properties have been determined by means of statistical mechanics. The discussion of the thermodynamic state includes the evaluation of the plasma state and its contribution to the caloric variables-of-state of saturated oxide fuel vapor. Because of the extremely high ion and electron density due to thermal ionization, the ionized component of the fuel vapor does no more represent a perfect kinetic plasma. At temperatures around 5,000 K, UO 2 vapor reaches the collective plasma state and becomes increasingly 'metallic'. - Moreover, the nonuniform molecular equilibrium composition of UO 2 vapor has been taken into account in calculating its caloric functions-of-state. The contribution to specific heat and enthalpy of thermally excited electronic states of the vapor molecules has been derived by means of a Rydberg orbital model of the UO 2 molecule. The resulting enthalpy functions and specific heats for saturated UO 2 vapor of equilibrium composition and that for pure UO 2 gas are compared with the enthalpy and specific heat data of gaseous UO 2 at lower temperatures known from literature. (orig./HP) [de

Indigenous high volume air sampler

International Nuclear Information System (INIS)

Kotrappa, P.; Setty, N.P.N.; Raghunath, B.; Sivasubrahmanyam, P.S.

1978-01-01

A high volume air sampler for use in assessing concentrations of low levels of air borne particulates has been fabricated. The sampler will be of use in radioactive installations, conventional industries and environmental pollution analysis. It is comparable in performance with the imported Staplex air samplers. A turbine and motor system similar to the one found in conventional vacuum cleaners is used in its design. The sampler units can be produced in large numbers. (M.G.B.)

Group vector space method for estimating enthalpy of vaporization of organic compounds at the normal boiling point.

Science.gov (United States)

Wenying, Wei; Jinyu, Han; Wen, Xu

2004-01-01

The specific position of a group in the molecule has been considered, and a group vector space method for estimating enthalpy of vaporization at the normal boiling point of organic compounds has been developed. Expression for enthalpy of vaporization Delta(vap)H(T(b)) has been established and numerical values of relative group parameters obtained. The average percent deviation of estimation of Delta(vap)H(T(b)) is 1.16, which show that the present method demonstrates significant improvement in applicability to predict the enthalpy of vaporization at the normal boiling point, compared the conventional group methods.

Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling

Energy Technology Data Exchange (ETDEWEB)

Efimova, Anastasia [Brandenburgische Technische Universität (BTU) Cottbus – Senftenberg, Chair of Inorganic Chemistry, Großenhainer Str. 57, 01968 Senftenberg (Germany); Pinnau, Sebastian; Mischke, Matthias; Breitkopf, Cornelia [Technische Universität Dresden, Chair of Technical Thermodynamics, Helmholtzstr. 14, 01069 Dresden (Germany); Ruck, Michael [Technische Universität Dresden, Chair of Inorganic Chemistry, Bergstr. 66, 01062 Dresden (Germany); Schmidt, Peer, E-mail: peer.schmidt@hs-lausitz.de [Brandenburgische Technische Universität (BTU) Cottbus – Senftenberg, Chair of Inorganic Chemistry, Großenhainer Str. 57, 01968 Senftenberg (Germany)

2014-01-10

Graphical abstract: - Highlights: • Inorganic salt hydrates. • Latent heat thermal energy storage. • Thermal behavior of melting and crystallization. • Cycling stability. • Nucleation. - Abstract: Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 °C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO{sub 3}){sub 2}·6H{sub 2}O, Mn(NO{sub 3}){sub 2}·4H{sub 2}O, and KNO{sub 3} with the melting temperature range 18–21 °C and the enthalpy of fusion of about 110 kJ kg{sup −1}. Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation.

Enthalpy measurement of lithium meta-titanate by drop calorimetry and its derived heat capacity

International Nuclear Information System (INIS)

Ishioka, Rika; Mukai, Keisuke; Terai, Takayuki; Suzuki, Akihiro

2013-01-01

Highlights: • Li 2 TiO 3 was synthesized by a neutralizing method. • Enthalpy of Li 2 TiO 3 was measured by a drop calorimeter. • Heat capacity of Li 2 TiO 3 was derived as a function of temperature. -- Abstract: Enthalpy of Li 2 TiO 3 , which was synthesized by a neutralizing method and its Li/Ti ratio was determined to be Li/Ti ratio (mol/mol) = 1.97, was measured by a drop calorimeter, and its heat capacity was derived as a function of temperature. XRD (X-ray diffraction) analysis of the sample before and after the enthalpy measurement indicated no phase change during the measurement and a single phase of Li 2 TiO 3 was observed. The enthalpy data were expressed as H(T) − H(323.17) (J/g) = 2.2 × 10 −5 ·T 2 + 1.4·T + 2.7 × 10 4 /T − 5.6 × 10 2 (373–1273 K), where T is temperature in K. The heat capacity was calculated as C p (J/g K) = 2.2 × 2 × 10 −5 ·T + 1.4–2.7 × 10 4 /T 2 by differentiating the equation by temperature. These equations have accuracy of 3%

Structural studies of cyclic ureas: 3. Enthalpy of formation of barbital

International Nuclear Information System (INIS)

Ribeiro da Silva, Maria das Dores M.C.; Ribeiro da Silva, Manuel A.V.; Freitas, Vera L.S.; Roux, Maria Victoria; Jimenez, Pilar; Temprado, Manuel; Davalos, Juan Z.; Cabildo, Pilar; Claramunt, Rosa M.; Elguero, Jose

2009-01-01

A thermochemical and thermophysical study has been carried out for crystalline barbital [5,5'-diethylbarbituric acid]. The thermochemical study was made by static bomb combustion calorimetry, from which the standard (p 0 =0.1MPa) molar enthalpy of formation of the crystalline barbital, at T = 298.15 K, was derived as -(753.0 ± 1.8) kJ . mol -1 . The thermophysical study was made by differential scanning calorimetry over the temperature interval (265 to 470) K. A solid-solid phase transition was found at T = 413.3 K. The vapour pressures of the crystalline barbital were measured at several temperatures between T = (355 and 377) K, by the Knudsen mass-loss effusion technique, from which the standard molar enthalpy of sublimation, at T = 298.15 K was derived as (117.3 ± 0.6) kJ . mol -1 . The combination of the experimental results yielded the standard molar enthalpy of formation of barbital in the gaseous phase, at T = 298.15 K, as -(635.8 ± 1.9) kJ . mol -1 . This value is compared and discussed with our theoretical calculations by several methods (Gaussian-n theories G2 and G3, complete basis set CBS-QB3, density functional B3P86 and B3LYP) by means of atomization and isodesmic reaction schemes.

Enthalpy of dissociation and hydration number of methane hydrate from the Clapeyron equation

International Nuclear Information System (INIS)

Anderson, Graydon K.

2004-01-01

The enthalpies of the reactions in which methane hydrate is dissociated to methane vapor and either (1) water, or (2) ice are determined by a new analysis using the Clapeyron equation. The difference in enthalpies of the two reactions is used to infer the hydration number at the quadruple point where hydrate, ice, liquid water, and methane vapor coexist. By appropriate corrections, the hydration number at points removed from the quadruple point is also determined. The most important feature of the new analysis is the direct use of the Clapeyron equation. The method avoids the use of certain simplifying assumptions that have compromised the accuracy of previous analyses in which the Clausius-Clapeyron equation was used. The analysis takes into account the finite volumes of all phases, the non-ideality of the vapor phase, and the solubility of methane in water. The results show that the enthalpy of dissociation and hydration number are constant within experimental error over the entire (hydrate, liquid, vapor) coexistence region. The results are more accurate than but entirely consistent with almost all previous studies

Enthalpy of Vaporization and Vapor Pressures: An Inexpensive Apparatus

Science.gov (United States)

Battino, Rubin; Dolson, David A.; Hall, Michael A.; Letcher, Trevor M.

2007-01-01

A simple and inexpensive method to determine the enthalpy of vaporization of liquids by measuring vapor pressure as a function of temperature is described. The vapor pressures measured with the stopcock cell were higher than the literature values and those measured with the sidearm rubber septum cell were both higher and lower than literature…

Enthalpy and the mechanics of AdS black holes

International Nuclear Information System (INIS)

Kastor, David; Traschen, Jennie; Ray, Sourya

2009-01-01

We present geometric derivations of the Smarr formula for static AdS black holes and an expanded first law that includes variations in the cosmological constant. These two results are further related by a scaling argument based on Euler's theorem. The key new ingredient in the constructions is a two-form potential for the static Killing field. Surface integrals of the Killing potential determine the coefficient of the variation of Λ in the first law. This coefficient is proportional to a finite, effective volume for the region outside the AdS black hole horizon, which can also be interpreted as minus the volume excluded from a spatial slice by the black hole horizon. This effective volume also contributes to the Smarr formula. Since Λ is naturally thought of as a pressure, the new term in the first law has the form of effective volume times change in pressure that arises in the variation of the enthalpy in classical thermodynamics. This and related arguments suggest that the mass of an AdS black hole should be interpreted as the enthalpy of the spacetime.

Accuracy of the DLPNO-CCSD(T) method for non-covalent bond dissociation enthalpies from coinage metal cation complexes

KAUST Repository

Minenkov, Yury; Chermak, Edrisse; Cavallo, Luigi

2015-01-01

The performance of the domain based local pair-natural orbital coupled-cluster (DLPNO-CCSD(T)) method has been tested to reproduce the experimental gas phase ligand dissociation enthalpy in a series of Cu+, Ag+ and Au+ complexes. For 33 Cu+ - non-covalent ligand dissociation enthalpies all-electron calculations with the same method result in MUE below 2.2 kcal/mol, although a MSE of 1.4 kcal/mol indicates systematic underestimation of the experimental values. Inclusion of scalar relativistic effects for Cu either via effective core potential (ECP) or Douglass-Kroll-Hess Hamiltonian, reduces the MUE below 1.7 kcal/mol and the MSE to -1.0 kcal/mol. For 24 Ag+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) method results in a mean unsigned error (MUE) below 2.1 kcal/mol and vanishing mean signed error (MSE). For 15 Au+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) methods provides larger MUE and MSE, equal to 3.2 and 1.7 kcal/mol, which might be related to poor precision of the experimental measurements. Overall, for the combined dataset of 72 coinage metal ion complexes DLPNO-CCSD(T) results in a MUE below 2.2 kcal/mol and an almost vanishing MSE. As for a comparison with computationally cheaper density functional theory (DFT) methods, the routinely used M06 functional results in MUE and MSE equal to 3.6 and -1.7 kca/mol. Results converge already at CC-PVTZ quality basis set, making highly accurate DLPNO-CCSD(T) estimates to be affordable for routine calculations (single-point) on large transition metal complexes of > 100 atoms.

Accuracy of the DLPNO-CCSD(T) method for non-covalent bond dissociation enthalpies from coinage metal cation complexes

KAUST Repository

Minenkov, Yury

2015-08-27

The performance of the domain based local pair-natural orbital coupled-cluster (DLPNO-CCSD(T)) method has been tested to reproduce the experimental gas phase ligand dissociation enthalpy in a series of Cu+, Ag+ and Au+ complexes. For 33 Cu+ - non-covalent ligand dissociation enthalpies all-electron calculations with the same method result in MUE below 2.2 kcal/mol, although a MSE of 1.4 kcal/mol indicates systematic underestimation of the experimental values. Inclusion of scalar relativistic effects for Cu either via effective core potential (ECP) or Douglass-Kroll-Hess Hamiltonian, reduces the MUE below 1.7 kcal/mol and the MSE to -1.0 kcal/mol. For 24 Ag+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) method results in a mean unsigned error (MUE) below 2.1 kcal/mol and vanishing mean signed error (MSE). For 15 Au+ - non-covalent ligand dissociation enthalpies the DLPNO-CCSD(T) methods provides larger MUE and MSE, equal to 3.2 and 1.7 kcal/mol, which might be related to poor precision of the experimental measurements. Overall, for the combined dataset of 72 coinage metal ion complexes DLPNO-CCSD(T) results in a MUE below 2.2 kcal/mol and an almost vanishing MSE. As for a comparison with computationally cheaper density functional theory (DFT) methods, the routinely used M06 functional results in MUE and MSE equal to 3.6 and -1.7 kca/mol. Results converge already at CC-PVTZ quality basis set, making highly accurate DLPNO-CCSD(T) estimates to be affordable for routine calculations (single-point) on large transition metal complexes of > 100 atoms.

Enthalpy increment measurements of Sr3Zr2O7(s) and Sr4Zr3O10(s)

International Nuclear Information System (INIS)

Banerjee, A.; Dash, S.; Prasad, R.; Venugopal, V.

1998-01-01

Enthalpy increment measurements on Sr 3 Zr 2 O 7 (s) and Sr 4 Zr 3 O 10 (s) were carried out using a Calvet micro-calorimeter. The enthalpy increment values were least squares analyzed with the constraints that H 0 (T)-H 0 (298.15 K) at 298.15 K equals to zero and C p 0 (298.15 K) equals to the estimated value. The dependence of enthalpy increment with temperature is given. (orig.)

Solubility of crystalline organic compounds in high and low molecular weight amorphous matrices above and below the glass transition by zero enthalpy extrapolation.

Science.gov (United States)

Amharar, Youness; Curtin, Vincent; Gallagher, Kieran H; Healy, Anne Marie

2014-09-10

Pharmaceutical applications which require knowledge of the solubility of a crystalline compound in an amorphous matrix are abundant in the literature. Several methods that allow the determination of such data have been reported, but so far have only been applicable to amorphous polymers above the glass transition of the resulting composites. The current work presents, for the first time, a reliable method for the determination of the solubility of crystalline pharmaceutical compounds in high and low molecular weight amorphous matrices at the glass transition and at room temperature (i.e. below the glass transition temperature), respectively. The solubilities of mannitol and indomethacin in polyvinyl pyrrolidone (PVP) K15 and PVP K25, respectively were measured at different temperatures. Mixtures of undissolved crystalline solute and saturated amorphous phase were obtained by annealing at a given temperature. The solubility at this temperature was then obtained by measuring the melting enthalpy of the crystalline phase, plotting it as a function of composition and extrapolating to zero enthalpy. This new method yielded results in accordance with the predictions reported in the literature. The method was also adapted for the measurement of the solubility of crystalline low molecular weight excipients in amorphous active pharmaceutical ingredients (APIs). The solubility of mannitol, glutaric acid and adipic acid in both indomethacin and sulfadimidine was experimentally determined and successfully compared with the difference between their respective calculated Hildebrand solubility parameters. As expected from the calculations, the dicarboxylic acids exhibited a high solubility in both amorphous indomethacin and sulfadimidine, whereas mannitol was almost insoluble in the same amorphous phases at room temperature. This work constitutes the first report of the methodology for determining an experimentally measured solubility for a low molecular weight crystalline solute

Melting temperature and enthalpy variations of phase change materials (PCMs): a differential scanning calorimetry (DSC) analysis

Science.gov (United States)

Sun, Xiaoqin; Lee, Kyoung Ok; Medina, Mario A.; Chu, Youhong; Li, Chuanchang

2018-06-01

Differential scanning calorimetry (DSC) analysis is a standard thermal analysis technique used to determine the phase transition temperature, enthalpy, heat of fusion, specific heat and activation energy of phase change materials (PCMs). To determine the appropriate heating rate and sample mass, various DSC measurements were carried out using two kinds of PCMs, namely N-octadecane paraffin and calcium chloride hexahydrate. The variations in phase transition temperature, enthalpy, heat of fusion, specific heat and activation energy were observed within applicable heating rates and sample masses. It was found that the phase transition temperature range increased with increasing heating rate and sample mass; while the heat of fusion varied without any established pattern. The specific heat decreased with the increase of heating rate and sample mass. For accuracy purpose, it is recommended that for PCMs with high thermal conductivity (e.g. hydrated salt) the focus will be on heating rate rather than sample mass.

Standard formation enthalpies of Nasub(2+x)Vsub(6)Osub(16-y) bronze of kappa type

International Nuclear Information System (INIS)

Khodos, M.Ya.; Slobodin, B.V.; Surat, L.L.; Fotiev, A.A.

1980-01-01

Standard formation enthalpies of sodium oxide vanadium bronze of kappa Nasub(2+x)Vsub(6)Osub(16-y) type of different composition have been determined by the method of solution calorimetry. It has been ascertained that within the limits of homogeneity a standard formation enthalpy decreases insignificantly with the increase of bronze oxygen defectiveness and is a linear function of sodium content

Structure–property relationships in ionic liquids: Influence of branched and cyclic groups on vaporization enthalpies of imidazolium-based ILs

International Nuclear Information System (INIS)

Zaitsau, Dzmitry H.; Varfolomeev, Mikhail A.; Verevkin, Sergey P.; Stanton, Alexander D.; Hindman, Michelle S.; Bara, Jason E.

2016-01-01

Highlights: • Ionic liquids [Rmim][NTf_2] with iso-alkyl and cyclic substituents were synthesized. • Vaporization enthalpies were measured using quartz-crystal microbalance. • Data consistency was tested by comparison with the homomorph compounds. • Vaporization enthalpies of branched ILs are generally on the same level as for linear. • These findings are useful for the quick estimation of vaporization enthalpies. - Abstract: Ionic liquids (ILs) with branched and cyclic substituents are seldom studied in the literature, and as such there are little to no data characterizing their thermophysical properties. ILs with branched and cyclic substituents are just as convenient to synthesize and study as their counterparts with linear substituents, but the effects of these substituents on IL properties are not yet well-defined due to the preference for linear substituents. Standard molar vaporization enthalpies of six imidazolium based ionic liquids [Rmim][NTf_2] with iso-alkyl and cyclic substituents (R = iso-propyl, iso-butyl, sec-butyl, methylcyclopropyl, cyclopentyl and methylcyclohexyl) were derived from quartz-crystal microbalance (QCM) method. Enthalpies of vaporization measured at elevated temperatures have been adjusted to the reference temperature 298 K and tested for consistency by comparison with the homomorphy alkane, alkylbenzenes and alkyl-imidazoles. It was found that vaporization enthalpies of ILs with the iso-alkyl and cyclic groups are generally on the same level within (±2 to 3) kJ · mol"−"1 significantly compared to the analogous ILs with the imidazolium cation substituted with the linear alkyl substituents of the same chain length. These findings are useful for the quick estimation of vaporization enthalpies of various substituted IL cations (e.g. pyrrolidinium, ammonium, pyridinium, etc.).

Estimating the melting point, entropy of fusion, and enthalpy of ...

Science.gov (United States)

The entropies of fusion, enthalies of fusion, and melting points of organic compounds can be estimated through three models developed using the SPARC (SPARC Performs Automated Reasoning in Chemistry) platform. The entropy of fusion is modeled through a combination of interaction terms and physical descriptors. The enthalpy of fusion is modeled as a function of the entropy of fusion, boiling point, and fexibility of the molecule. The melting point model is the enthlapy of fusion divided by the entropy of fusion. These models were developed in part to improve SPARC's vapor pressure and solubility models. These models have been tested on 904 unique compounds. The entropy model has a RMS of 12.5 J mol-1K-1. The enthalpy model has a RMS of 4.87 kJ mol-1. The melting point model has a RMS of 54.4°C. Published in the journal, SAR and QSAR in Environmental Research

Coupling geophysical investigation with hydrothermal modeling to constrain the enthalpy classification of a potential geothermal resource.

Science.gov (United States)

White, Jeremy T.; Karakhanian, Arkadi; Connor, Chuck; Connor, Laura; Hughes, Joseph D.; Malservisi, Rocco; Wetmore, Paul

2015-01-01

An appreciable challenge in volcanology and geothermal resource development is to understand the relationships between volcanic systems and low-enthalpy geothermal resources. The enthalpy of an undeveloped geothermal resource in the Karckar region of Armenia is investigated by coupling geophysical and hydrothermal modeling. The results of 3-dimensional inversion of gravity data provide key inputs into a hydrothermal circulation model of the system and associated hot springs, which is used to evaluate possible geothermal system configurations. Hydraulic and thermal properties are specified using maximum a priori estimates. Limited constraints provided by temperature data collected from an existing down-gradient borehole indicate that the geothermal system can most likely be classified as low-enthalpy and liquid dominated. We find the heat source for the system is likely cooling quartz monzonite intrusions in the shallow subsurface and that meteoric recharge in the pull-apart basin circulates to depth, rises along basin-bounding faults and discharges at the hot springs. While other combinations of subsurface properties and geothermal system configurations may fit the temperature distribution equally well, we demonstrate that the low-enthalpy system is reasonably explained based largely on interpretation of surface geophysical data and relatively simple models.

Temperature-dependent enthalpy of oxygenation in Antarctic fish hemoglobins

DEFF Research Database (Denmark)

Fago, A.; Wells, R.M.G.; Weber, Roy E.

1997-01-01

The effect of temperature on the oxygen-binding properties of the hemoglobins of three cold-adapted Antarctic fish species, Dissostichus mawsoni, Pagothenia borchgrevinki and Trematomus, sp., has been investigated under different pH values and buffer conditions. A clear non linear van't Hoff plot...... (logP(50) vs 1/T) of D. mawsoni hemoglobin indicates that the enthalpy of oxygenation (slope of the plot) is temperature dependent and that at high temperatures oxygen-binding becomes less exothermic. Nearly linear relationships were found in the hemoglobins of the other two species. The data were...... oxygen binding. The degree of the temperature dependence of the heat of oxygenation observed in these hemoglobins seems to reflect the differences in their allosteric effects rather than a specific molecular adaptation to low temperatures. Moreover, this study indicates that the disagreement between...

A study of the vaporization enthalpies of some 1-substituted imidazoles and pyrazoles by correlation-gas chromatography.

Science.gov (United States)

Lipkind, Dmitry; Plienrasri, Chatchawat; Chickos, James S

2010-12-23

The vaporization enthalpies of 1-methyl-, 1-ethyl-, 1-phenyl-, and 1-benzylimidazole, 1-methyl- and 1-phenylpyrazole, and trans-azobenzene are evaluated by correlation-gas chromatography (C-GC) using a variety of azines and diazines as standards. The vaporization enthalpies obtained by C-GC when compared to literature values are approximately 14 kJ·mol(-1) smaller for the imidazoles and 6 kJ·mol(-1) smaller for the pyrazoles. The literature vaporization enthalpies of 1-methylpyrrole and 1-methylindole, two closely related compounds with one less nitrogen, are reproduced by C-GC. These results suggest that the magnitude of the intermolecular interactions present in 1-substituted imidazoles and pyrazoles are significantly larger than the those present in the reference compounds and greater than or equal in magnitude to the enhanced intermolecular interactions observed previously in aromatic 1,2-diazines. The vaporization enthalpy and vapor pressure of a trans-1,2-diazine, trans-azobenzene, measured by C-GC using similar standards reproduced the literature values within experimental error.

Heat Effect of the Protonation of Glycine and the Enthalpies of Resolvation of Participating Chemical Species in Water-Dimethylsulfoxide Solvent Mixtures

Science.gov (United States)

Isaeva, V. A.; Sharnin, V. A.

2018-02-01

Enthalpies of the protonation of glycine in water‒dimethylsulfoxide (DMSO) mixed solvents are determined calorimetrically in the range of DMSO mole fractions of 0.0 to 0.9, at T = 298.15 K and an ionic strength μ = 0.3 (NaClO4). It is established that the protonation of glycine becomes more exothermic with an increasing mole fraction of DMSO, and the enthalpies of resolvation of glycine and glycinium ions in water‒DMSO solvent mixtures are calculated. It is shown that the small changes in the enthalpy of protonation observed at low mole fractions of DMSO are caused by the contributions from the solvation of proton and protonated glycine cancelling each other out. The enthalpy term of the Gibbs energy of the reaction leading to the formation of glycinium ion is estimated along with the enthalpy of resolvation of the reacting species in the water‒DMSO mixed solvent.

Experimental characterization of meteoric material exposed to a high enthalpy flow in the Plasmatron

Science.gov (United States)

Zavalan, Luiza; Bariselli, Federico; Barros Dias, Bruno; Helber, Bernd; Magin, Thierry

2017-04-01

Meteoroids, disintegrated during their entry in the atmosphere, contribute massively to the input of cosmic metals to Earth. Yet, this phenomenon is not well understood. Experimental studies on meteor material degradation in high enthalpy facilities are scarce and often do not provide quantitative data which are necessary for the validation of the simulation tools. In this work, we tried to duplicate typical meteor flight conditions in a ground testing facility to analyze the thermo-chemical degradation mechanisms by reproducing the stagnation point region conditions. The VKI Plasmatron is one of the most powerful induction-coupled plasma wind-tunnels in the world. It represents an important tool for the characterization of ceramic and ablative materials employed in the fabrication of Thermal Protection Systems (TPS) of spacecraft. The testing methodology and measurement techniques used for TPS characterization were adapted for the investigation of evaporation and melting in samples of basalt (meteorite surrogate) and ordinary chondrite. The materials were exposed to stagnation point heat fluxes of 1 MW/m2 and 3 MW/m2. During the test, numerous local pockets were formed at the surface of the samples by the emergence of gas bubbles. Images recorded through a digital 14bit CCD camera system clearly revealed the frothing of the surface for both tested materials. This process appeared to be more heterogeneous for the basaltic samples than for the ordinary chondritic material. Surface temperature measurements obtained via a two-color pyrometer showed a maximum surface temperature in the range between 2160 and 2490 Kelvins. Some of the basaltic samples fractured during the tests. This is probably due to the strong thermal gradients experienced by the material in these harsh conditions. Therefore, the surface temperature measurements suffered sudden drops in correspondence with the fracturing time. Emission spectra of air and ablated species were collected with resolution

Formation enthalpies of LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

Energy Technology Data Exchange (ETDEWEB)

Qi, Jianqi [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California, Davis, CA 95616 (United States); College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Laboratory of High Energy Density Physics of Ministry of Education, Sichuan University, Chengdu 610064 (China); Guo, Xiaofeng [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California, Davis, CA 95616 (United States); Mielewczyk-Gryn, Aleksandra [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California, Davis, CA 95616 (United States); Faculty of Applied Physics and Mathematics, Department of Solid State Physics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk (Poland); Navrotsky, Alexandra, E-mail: anavrotsky@ucdavis.edu [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California, Davis, CA 95616 (United States)

2015-07-15

High-temperature oxide melt solution calorimetry using 3Na{sub 2}O·MoO{sub 3} at 802 °C was performed for interlanthanide perovskites LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La{sub 2}O{sub 3}, Ho{sub 2}O{sub 3}, Er{sub 2}O{sub 3}, Tm{sub 2}O{sub 3} and Yb{sub 2}O{sub 3}). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be −8.3±3.4 kJ/mol for LaHoO{sub 3}, −9.9±3.0 kJ/mol for LaErO{sub 3}, −10.8±2.7 kJ/mol for LaTmO{sub 3} and −12.3±2.9 kJ/mol for LaYbO{sub 3}. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds. - Graphical abstract: A linear relationship between the enthalpy of formation and the tolerance factor for interlanthanide LaLn'O{sub 3} (Ln'=Ho, Er, Tm, and Yb) and other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites. - Highlights: • Interlanthanide perovskites were synthesized by solid state reactions. • Their enthalpies of formation were measured by oxide melt solution calorimetry. • ΔH{sub f,ox} shows a linear relationship with tolerance factor.

Theoretical and experimental investigation of the destruction of graphites in a flow of dissociated air

Science.gov (United States)

Bovina, T. A.; Zviagin, Y. V.; Markelov, N. V.; Chudetskiy, Y. V.

1986-01-01

A method is presented for calculating the heating and erosion of blunt bodies made of graphite in a high-enthalpy flow of dissociated air, assuming chemical equilibrium on the surface and taking account of the thermal effects of combustion and sublimation of graphite. The analysis involves the use of a finite difference scheme to solve an equation of unsteady heat conduction. Attention is given to the equilibrium vaporization of C, C2 and C3 molecules. The calculations agree well with experimental data for a wide range of temperatures and stagnation pressures.

The solvent effect on the enthalpy of hydrolysis of cyclic adenosine 3',5'-monophosphate : a quantum chemical study

NARCIS (Netherlands)

Scheffers - Sap, Miek; Buck, H.M.

1978-01-01

The solvent effect on the enthalpy of hydrolysis has been studied by the Extended-Hückel method for the hydrolysis reactions of cyclic adenosine 3',5'-monophosphate (cyclic 3',5'-AMP) and related cyclic phosphate diesters. The results show that the difference in enthalpy of hydrolysis between cyclic

Standard partial molar heat capacities and enthalpies of formation of aqueous aluminate under hydrothermal conditions from integral heat of solution measurements

International Nuclear Information System (INIS)

Coulier, Yohann; Tremaine, Peter R.

2014-01-01

Highlights: • Heats of solution of NaAlO 2 (s) were measured at five temperatures up to 250 °C. • Standard molar enthalpies of solution were determined from the measured heats of solution. • Standard molar enthalpies of solution were correlated with the density model. • The density model allows us to determine the standard molar heat capacities of reaction. - Abstract: Heats of solution of sodium aluminum oxide, NaAlO 2 (s), were measured in aqueous sodium hydroxide solutions using a Tian–Calvet heat-flow calorimeter (Setaram, Model C80) with high pressure “batch cells” made of hastelloy C-276, at five temperatures from (373.15 to 523.15) K, steam saturation pressure, and concentrations from (0.02 to 0.09) mol · kg −1 . Standard molar enthalpies of solution, Δ soln H ∘ , and relative standard molar enthalpies, [H ∘ (T) − H ∘ (298.15 K)], of NaAl(OH) 4 (aq) were determined from the measured heats of solution. The results were fitted with the “density” model. The temperature dependence of Δ soln H ∘ from the model yielded the standard molar heat capacities of reaction, Δ soln C p ∘ , from which standard partial molar heat capacities for aqueous aluminate, C p ∘ [A1(OH) 4 − ,aq], were calculated. Standard partial molar enthalpies of formation, Δ f H ∘ , and entropies, S ∘ , of A1(OH) 4 − (aq) were also determined. The values for C p ∘ [A1(OH) 4 − ,aq] agree with literature data determined up to T = 413 K from enthalpy of solution and heat capacity measurements to within the combined experimental uncertainties. They are consistent with differential heat capacity measurements up to T = 573 K from Schrödle et al. (2010) [29] using the same calorimeter, but this method has the advantage that measurements could be made at much lower concentrations in the presence of an excess concentration of ligand. To our knowledge, these are the first standard partial molar heat capacities measured under hydrothermal conditions by the

Excess enthalpies of the ternary mixtures: {tetrahydrofuran + 3-methylpentane + (octane or decane)} at the temperature 298.15 K

International Nuclear Information System (INIS)

Wang Zhaohui; Benson, George C.; Lu, Benjamin C.-Y.

2003-01-01

Measurements of excess molar enthalpies at the temperature 298.15 K in a flow microcalorimeter, are reported for the two ternary mixtures {X 1 C 4 H 8 O + X 2 CH 3 CH 2 CH(CH 3 )CH 2 CH 3 + (1-X 1 -X 2 )CH 3 (CH 2 ) v-2 CH 3 } with v=8 and 10. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann-Fried model, using only the physical properties of the components and their binary mixtures

Solid-State Characterization and Relative Formation Enthalpies To Evaluate Stability of Cocrystals of an Antidiabetic Drug.

Science.gov (United States)

Duggirala, Naga Kiran; Frericks Schmidt, Heather L; Lei, Zhaohui; Zaworotko, Michael J; Krzyzaniak, Joseph F; Arora, Kapildev K

2018-05-07

The current study integrates formation enthalpy and traditional slurry experiments to quickly assess the physical stability of cocrystal drug substance candidates for their potential to support drug development. Cocrystals of an antidiabetic drug (GKA) with nicotinamide (NMA), vanillic acid (VLA), and ethyl vanillin (EVL) were prepared and characterized by powder X-ray diffractometry (PXRD), spectroscopic, and thermal techniques. The formation enthalpies of the cocrystals, and their physical mixtures (GKA + coformer) were measured by the differential scanning calorimetry (DSC) method reported by Zhang et al. [ Cryst. Growth Des. 2012 , 12 ( 8 ), 4090 - 4097 ]. The experimentally measured differences in the relative formation enthalpies obtained by integrating the heat flow of each cocrystal against the respective physical mixture were correlated to the physical stability of the cocrystals in the solid state. The relative formation enthalpies of all of the cocrystals studied suggest that the cocrystals are not physically stable at room temperature versus their physical mixtures. To further address relative stability, the cocrystals were slurried in 30% v/v aqueous ethanol, and it was observed that all of the cocrystals revert to GKA within 48 h at room temperature. The slurry experiments are consistent with the relative instability of the cocrystals with respect to their physical mixtures suggested by the DSC results.

Free Energy, Enthalpy and Entropy from Implicit Solvent End-Point Simulations.

Science.gov (United States)

Fogolari, Federico; Corazza, Alessandra; Esposito, Gennaro

2018-01-01

Free energy is the key quantity to describe the thermodynamics of biological systems. In this perspective we consider the calculation of free energy, enthalpy and entropy from end-point molecular dynamics simulations. Since the enthalpy may be calculated as the ensemble average over equilibrated simulation snapshots the difficulties related to free energy calculation are ultimately related to the calculation of the entropy of the system and in particular of the solvent entropy. In the last two decades implicit solvent models have been used to circumvent the problem and to take into account solvent entropy implicitly in the solvation terms. More recently outstanding advancement in both implicit solvent models and in entropy calculations are making the goal of free energy estimation from end-point simulations more feasible than ever before. We review briefly the basic theory and discuss the advancements in light of practical applications.

Free Energy, Enthalpy and Entropy from Implicit Solvent End-Point Simulations

Directory of Open Access Journals (Sweden)

Federico Fogolari

2018-02-01

Full Text Available Free energy is the key quantity to describe the thermodynamics of biological systems. In this perspective we consider the calculation of free energy, enthalpy and entropy from end-point molecular dynamics simulations. Since the enthalpy may be calculated as the ensemble average over equilibrated simulation snapshots the difficulties related to free energy calculation are ultimately related to the calculation of the entropy of the system and in particular of the solvent entropy. In the last two decades implicit solvent models have been used to circumvent the problem and to take into account solvent entropy implicitly in the solvation terms. More recently outstanding advancement in both implicit solvent models and in entropy calculations are making the goal of free energy estimation from end-point simulations more feasible than ever before. We review briefly the basic theory and discuss the advancements in light of practical applications.

Standard Molar Enthalpy of Formation of RE(C5H8NS2)3(C12H8N2)

Institute of Scientific and Technical Information of China (English)

Meng Xiangxin; Shuai Qi; Chen Sanping; Xie Gang; Gao Shengli; Shi Qizhen

2005-01-01

Four solid ternary complexes of RE (C5H8NS2)3(C12H8N2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamate (APDC) and 1, 10-phenanthroline*H2O (o-phen*H2O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes show that the RE3+ coordinated with six sulfur atoms of three PDC- and two nitrogen atoms of o-phen*H2O. It was assumed that the coordination number of RE3+ is eight. The constant-volume combustion energies of the complexes, ΔcU, were determined as (-16937.88±9.79 ), (-17588.79±8.62 ), (-17747.14±8.25 ) and (-17840.37±8.87 ) kJ*mol-1, by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, ΔcHθm, and standard molar enthalpies of formation, ΔfHθm, were calculated as (-16953.37±9.79), (-17604.28±8.62), (-17762.63±8.25), (-17855.86±8.87) kJ*mol-1 and (-857.04±10.52), (-282.43±9.58), (-130.08±9.13), (-55.75±9.83) kJ*mol-1.

High strength air-dried aerogels

Science.gov (United States)

Coronado, Paul R.; Satcher, Jr., Joe H.

2012-11-06

A method for the preparation of high strength air-dried organic aerogels. The method involves the sol-gel polymerization of organic gel precursors, such as resorcinol with formaldehyde (RF) in aqueous solvents with R/C ratios greater than about 1000 and R/F ratios less than about 1:2.1. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be air dried at ambient temperatures and pressures. The method significantly reduces the time and/or energy required to produce a dried aerogel compared to conventional methods using either supercritical solvent extraction. The air dried gel exhibits typically less than 5% shrinkage.

The enthalpy of solid scandium in the temperature range 406 - 1812 K

International Nuclear Information System (INIS)

Lyapunov, K.M.; Baginskij, A.V.; Stankus, S.V.

2001-01-01

Enthalpy of pure scandium was measured on massive calorimeter in the range from 406 to 1812 K by mixing method. The enthalpy of face centered close cubic lattice - body centered cubic lattice transformation is equal to ΔH t 4068 J/mol. Obtained value within the limits of error is compatible with the results given earlier (4009 J/mol). The dependence of the middle specific heat of scandium C p (T) on the temperature was shown in correlation with the results of other works. The results of the conducted experiments reinforce the conclusion made earlier about an absence (or a little) in the decomposition of an anharmonic component of the oscillation specific heat of scandium C p a (T) members proportional to the first or the second degrees of temperature [ru

Evaluation of enthalpy of interfacial reactions from temperature dependency of interfacial equilibrium

International Nuclear Information System (INIS)

Kallay, Nikola; Cop, Ana

2005-01-01

Temperature dependency of equilibrium at metal oxide-aqueous electrolyte solution interface was analyzed by numerical simulation. Derivations of inner surface potential with respect to temperature were performed at constant values of several different parameters. When surface charge density in inner plane was kept constant the reasonable results were obtained, i.e. the electrostatic contribution to enthalpy of protonation of amphotheric surface sites was found to be positive in the pH region below the point of zero potential and negative above this point. All other examined possibilities produced opposite results. Derivation of empirical interfacial equilibrium constant at constant surface potential indicated that electrostatic effect on protonation entropy is negligible and that electrostatic contributions to reaction Gibbs energy and enthalpy are equal and directly related to the surface potential in the inner plane

Isotope effect in enthalpy of solvation of the lithium ion

International Nuclear Information System (INIS)

Krestov, G.A.; Egorov, G.I.; Korolev, V.P.

1989-01-01

At 298.15 K, the authors determined the standard enthalpies of solution for 6 LiCl and 7 LiCl in water, heavy water, dimethylsulfoxide (DMSO) and aqueous solutions of DMSO. The authors have established that solvation of 6 Li + is differentiated in water and DMSO to a greater degree than for 7 Li +

Oxidation potentials, Gibbs energies, enthalpies and entropies of actinide ions in aqueous solutions

International Nuclear Information System (INIS)

1977-01-01

The values of the Gibbs energy, enthalpy, and entropy of different actinide ions, thermodynamic characteristics of the processes of hydration of these ions, and the presently known ionization potentials of actinides are given. The enthalpy and entropy components of the oxidation potentials of actinide elements are considered. The curves of the dependence of the Gibbs energy of ion formation on the atomic number of the element and the Frost diagrams are analyzed. The diagram proposed by Frost represents the graphical dependence of the Gibbs energy of hydrated ions on the degree of oxidation of the element. Using the Frost diagram it is easy to establish whether a given ion is stable to disproportioning

Standard enthalpies of formation of selected Ru{sub 2}YZ Heusler compounds

Energy Technology Data Exchange (ETDEWEB)

Yin, Ming, E-mail: myin1@hawk.iit.edu; Nash, Philip

2015-06-15

Highlights: • Standard enthalpies of formation of Ru{sub 2}YZ were measured using a drop calorimeter. • Result of L2{sub 1} structured compounds agrees with first principles data. • Lattice parameters and related phase relationships were consistent with literature data. • Ru{sub 2}HfSn, Ru{sub 2}TiSn, Ru{sub 2}VGa, Ru{sub 2}VSi, Ru{sub 2}VSn of L2{sub 1} structure were reported for the first time. - Abstract: The standard enthalpies of formation of selected ternary Ru-based Heusler compounds Ru{sub 2}YZ (Y = Fe, Hf, Mn, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) were measured using high temperature direct reaction calorimetry. The measured enthalpies of formation (in kJ/mole of atoms) of the Heusler compounds are, Ru{sub 2}FeGe (−19.7 ± 3.3); Ru{sub 2}HfSn (−24.9 ± 3.6); Ru{sub 2}MnSi (−46.0 ± 2.6); Ru{sub 2}MnGe (−29.7 ± 1.0); Ru{sub 2}MnSn (−20.6 ± 2.4); Ru{sub 2}TiSi (−94.9 ± 4.0); Ru{sub 2}TiGe (−79.1 ± 3.2); Ru{sub 2}TiSn (−60.6 ± 1.8); Ru{sub 2}VSi (−55.9 ± 1.7);for the B2-structured compounds, Ru{sub 2}FeSi (−28.5 ± 0.8); Ru{sub 2}HfAl (−70.8 ± 1.9); Ru{sub 2}MnAl (−32.3 ± 1.9); Ru{sub 2}MnGa (−25.3 ± 3.0); Ru{sub 2}TiAl (−62.7 ± 3.5); Ru{sub 2}VAl (−30.9 ± 1.6); Ru{sub 2}ZrAl (−64.5 ± 1.5). Values were compared with those from published first principles calculations and the OQMD (Open Quantum Materials Database). Lattice parameters of these compounds were determined using X-ray diffraction analysis (XRD). Microstructures were identified using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS)

Low-tmperature Heat Capacities and Standard Molar Enthalpy of Formation of 4-Nitrobenzyl Alcohol

Institute of Scientific and Technical Information of China (English)

MENG, Qingfen; TAN, Zhicheng; WANG, Xiaohuan; DONG, Yaping; LI, Wu; SHI, Quan

2009-01-01

Low-temperature heat capacities of 4-nitrobenzyl alcohol (4-NBA) have been measured by a high precision automated adiabatic calorimeter over the temperature range from 78 to 396 K. The melting temperature, the molar calculated in the range from 80 to 400 K at the interval of 5 K. The constant-volume energy and standard molar en- at T=298.15 K. The standard molar enthalpy of formation has been derived, ΔfHom(C7H7NO3, s)=-(206.49± namic quantities through a Hess thermochemical cycle.

Diluent and extractant effects on the enthalpy of extraction of uranium(VI) and americium(III) nitrates by trialkyl phosphates

International Nuclear Information System (INIS)

Srinivasan, T.G.; Vasudeva Rao, P.R.; Sood, D.D.

1998-01-01

The effect of various diluents such as n-hexane, n-heptane n-octane, isooctane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-hexadecane, cyclohexane, benzene, toluene, p-xylene, mesitylene and o-dichlorobenzene on the enthalpy of extraction of uranyl nitrate by tri-n-amyl phosphate (TAP) over the temperature range 283 K--333 K has been studied. The results indicate that the enthalpy of extraction does not vary significantly with the diluents studied. Also enthalpies of extraction of uranyl nitrate and americium(III) nitrate by neutral organo phosphorous extractants such as tri-n-butyl phosphate (TBP), tri-n-amyl phosphate (TAP), tri-sec-butyl phosphate (TsBP), tri-isoamyl phosphate (TiAP) and tri-n-hexyl phosphate (THP) have been studied. An attempt has been made to explain the trends, on the basis of the nature of the solvate formed and the different terms which contribute to the overall enthalpy change

Enthalpies of potassium iodide dissolution in dimethyl acetamide mixtures with water

International Nuclear Information System (INIS)

Privalova, N.M.; Gritsenko, S.I.; Vorob'ev, A.F.

1986-01-01

Enthalpies of potassium iodide dissolution in mixed dimethyl acetamide - water solvent at 298.15 K in the whole range of dimethyl acetamide compositions are measured by the calorimetric method. From the plots of KI dissolution enthalpy dependence and dependence of experimental ΔH p∞ 0 value deviations from calculational ones on solvent composition, as well as from the results of calculation of solvate shell composition of potassium iodide ions in the mixed solvent, it is obvious that in the region of 0-15 mol% concentrations of dimethyl acetamide insufficient enrichment of solvate ion shells by dimethyl acetamide (DMAA) occurs, in the region of 15-40 mol% DMAA compositions enrichment of solvate shells of ions by water occurs, in the region of 40-100 mol% DMAA enrichment of solvate ion shells by the organic component in comparison with mixture compostion occurs. Maximum enrichment of solvate ion shells by mixture components in three above mentioned regions of the mixed solvent occurs at 10, 30 and 80 mol% DMAA concentrations

SGC method for predicting the standard enthalpy of formation of pure compounds from their molecular structures

International Nuclear Information System (INIS)

Albahri, Tareq A.; Aljasmi, Abdulla F.

2013-01-01

Highlights: • ΔH° f is predicted from the molecular structure of the compounds alone. • ANN-SGC model predicts ΔH° f with a correlation coefficient of 0.99. • ANN-MNLR model predicts ΔH° f with a correlation coefficient of 0.90. • Better definition of the atom-type molecular groups is presented. • The method is better than others in terms of combined simplicity, accuracy and generality. - Abstract: A theoretical method for predicting the standard enthalpy of formation of pure compounds from various chemical families is presented. Back propagation artificial neural networks were used to investigate several structural group contribution (SGC) methods available in literature. The networks were used to probe the structural groups that have significant contribution to the overall enthalpy of formation property of pure compounds and arrive at the set of groups that can best represent the enthalpy of formation for about 584 substances. The 51 atom-type structural groups listed provide better definitions of group contributions than others in the literature. The proposed method can predict the standard enthalpy of formation of pure compounds with an AAD of 11.38 kJ/mol and a correlation coefficient of 0.9934 from only their molecular structure. The results are further compared with those of the traditional SGC method based on MNLR as well as other methods in the literature

Accurate Gas Phase Formation Enthalpies of Alloys and Refractories Decomposition Products

KAUST Repository

Minenkov, Yury; Sliznev, Valery V.; Cavallo, Luigi

2017-01-01

predicted the ΔHf values of a series of these compounds having a group 4, 6, or 14 metal. The ΔHf values in question were derived within a composite Feller-Dixon-Peterson (FDP) scheme based protocol that combines the DLPNO-CCSD(T) enthalpy of ad hoc designed

Electrical resistivities and solvation enthalpies for solutions of salts in liquid alkali metals

International Nuclear Information System (INIS)

Hubberstey, P.; Dadd, A.T.

1982-01-01

An empirical correlation is shown to exist between the resistivity coefficients drho/dc for solutes in liquid alkali metals and the corresponding solvation enthalpies Usub(solvn) of the neutral gaseous solute species. Qualitative arguments based on an electrostatic solvation model in which the negative solute atom is surrounded by a solvation sphere of positive solvent ion cores are used to show that both parameters are dependent on the charge density of the solute atom and hence on the extent of charge transfer from solvent to solute. Thus as the charge density of the solute increases, the solvation enthalpy increases regularly and the resistivity coefficients pass through a maximum to give the observed approximately parabolic drho/dc versus Usub(solvn) relationship. (Auth.)

Enthalpy-Entropy Compensation in the Binding of Modulators at Ionotropic Glutamate Receptor GluA2

DEFF Research Database (Denmark)

Krintel, Christian; Francotte, Pierre; Pickering, Darryl S

2016-01-01

of 5 was examined with x-ray crystallography, showing that the only change compared to that of earlier compounds was the orientation of Ser-497 pointing toward the hydroxyl group of 5. The favorable enthalpy can be explained by the formation of a hydrogen bond from the side-chain hydroxyl group of Ser...... of modulators BPAM97 (2) and BPAM344 (3) into a hydroxyl group (BPAM557 (4) and BPAM521 (5), respectively), leads to a more favorable binding enthalpy (ΔH, kcal/mol) from −4.9 (2) and −7.5 (3) to −6.2 (4) and −14.5 (5), but also a less favorable binding entropy (−TΔS, kcal/mol) from −2.3 (2) and −1.3 (3) to −0......-497 to the hydroxyl group of 5, whereas the unfavorable entropy might be due to desolvation effects combined with a conformational restriction of Ser-497 and 5. In summary, this study shows a remarkable example of enthalpy-entropy compensation in drug development accompanied with a likely explanation...

The intermetallic ThRh5: microstructure and enthalpy increments

International Nuclear Information System (INIS)

Banerjee, Aparna; Joshi, A.R.; Kaity, Santu; Mishra, R.; Roy, S.B.

2013-01-01

Actinide intermetallics are one of the most interesting and important series of compounds. Thermochemistry of these compounds play significant role in understand the nature of bonding in alloys and nuclear fuel performance. In the present paper we report synthesis and characterization of thorium based intermetallic compound ThRh 5 (s) by SEM/EDX technique. The mechanical properties and enthalpy increment as a function of temperature of the alloy has been measured. (author)

Problem-based learning in teaching chemistry: enthalpy changes in systems

Science.gov (United States)

Ayyildiz, Yildizay; Tarhan, Leman

2018-01-01

Problem-based learning (PBL) as a teaching strategy has recently become quite widespread in especially chemistry classes. Research has found that students, from elementary through college, have many alternative conceptions regarding enthalpy changes in systems. Although there are several studies focused on identifying student alternative conceptions and misunderstandings of this subject, studies on preventing the formation of these alternative conceptions are limited.

Combustion energies and standard molar enthalpies of formation for the complexes of the first-row transitional metal chlorides with L-α-histidine

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

Seven novel solid complexes of the first-row transitional metal with L-α-histidine were synthesized, and their compositions were determined. The constant-volume combustion energies of the complexes were measured by a precision rotation bomb calorimeter. The standard molar enthalpies of combustion and the standard molar enthalpies of formation were calculated. The results indicated thatthe plots of the standard enthalpies of formation against the atomic number of the metal show a regularity of zigzag.

Investigation of variation of additional enthalpy of proteins with respect to pH by statistical mechanical methods

International Nuclear Information System (INIS)

Oylumoglu, G.

2005-01-01

In this study variation of additional enthalpy with respect to pH has been investigated by the statistical mechanical methods.. To bring up the additional effect, the partition function of the proteins are calculated by single protein molecule approximation. From the partition function, free energies of the proteins are obtained and by this way additional free energy has been used in the calculation of the terms in the thermodynamical quantity. Additional enthalpy H D has been obtained by taking effective electric field E and constant dipole moment M as thermodynamical variables and using Maxwell Equations. In the presented semi phenomenological theory, necessary data are taken from the experimental study of P.L. Privalov. The variation in the additional enthalpy H D has been investigated in the pH interval of 1-5 and the results of the calculations are discussed for Lysozyme

Calorimetric determination of the enthalpy of 1-butyl-3-methylimidazolium bromide synthesis: a key quantity in thermodynamics of ionic liquids.

Science.gov (United States)

Paulechka, Yauheni U; Kabo, Andrey G; Blokhin, Andrey V

2009-11-05

The enthalpy of the 1-butyl-3-methylimidazolium bromide [C(4)mim]Br ionic liquid synthesis reaction 1-methylimidazole (liq) + 1-bromobutane (liq) --> [C(4)mim]Br (liq) was determined in a homemade small-volume isoperibol calorimeter to be Delta(r)H degrees (298) = -87.7 +/- 1.6 kJ x mol(-1). The activation energy for this reaction in a homogeneous system E(A) = 73 +/- 4 kJ x mol(-1) was found from the results of calorimetric measurements. The formation enthalpies for the crystalline and liquid [C(4)mim]Br were determined from the calorimetric data: Delta(f)H degrees (298)(cr) = -178 +/- 5 kJ x mol(-1) and Delta(f)H degrees (298)(liq) = -158 +/- 5 kJ x mol(-1). The ideal-gas formation enthalpy of this compound Delta(f)H degrees (298)(g) = 16 +/- 7 kJ x mol(-1) was calculated using the methods of quantum chemistry and statistical thermodynamics. The vaporization enthalpy of [C(4)mim]Br, Delta(vap)H degrees (298) = 174 +/- 9 kJ x mol(-1), was estimated from the experimental and calculated formation enthalpies. It was demonstrated that vapor pressure of this ionic liquid cannot be experimentally determined.

Facing the challenge of predicting the standard formation enthalpies of n-butyl-phosphate species with ab initio methods

Science.gov (United States)

Saab, Mohamad; Réal, Florent; Šulka, Martin; Cantrel, Laurent; Virot, François; Vallet, Valérie

2017-06-01

Tributyl-phosphate (TBP), a ligand used in the PUREX liquid-liquid separation process of spent nuclear fuel, can form an explosive mixture in contact with nitric acid that might lead to a violent explosive thermal runaway. In the context of safety of a nuclear reprocessing plant facility, it is crucial to predict the stability of TBP at elevated temperatures. So far, only the enthalpies of formation of TBP are available in the literature with rather large uncertainties, while those of its degradation products, di-(HDBP) and mono-(H2MBP), are unknown. In this goal, we have used state-of-the art quantum chemical methods to compute the formation enthalpies and entropies of TBP and its degradation products di-(HDBP) and mono-(H2MBP) in gas and liquid phases. Comparisons of levels of quantum chemical theory revealed that there are significant effects of correlation on their electronic structures, pushing for the need of not only high level of electronic correlation treatment, namely, local coupled cluster with single and double excitation operators and perturbative treatment of triple excitations, but also extrapolations to the complete basis to produce reliable and accurate thermodynamics data. Solvation enthalpies were computed with the conductor-like screening model for real solvents [COSMO-RS], for which we observe errors not exceeding 22 kJ mol-1. We thus propose with final uncertainty of about 20 kJ mol-1 standard enthalpies of formation of TBP, HDBP, and H2MBP which amounts to -1281.7 ± 24.4, -1229.4 ± 19.6, and -1176.7 ± 14.8 kJ mol-1, respectively, in the gas phase. In the liquid phase, the predicted values are -1367.3 ± 24.4, -1348.7 ± 19.6, and -1323.8± 14.8 kJ mol-1, to which we may add about -22 kJ mol-1 error from the COSMO-RS solvent model. From these data, the complete hydrolysis of TBP is predicted as an exothermic phenomena but showing a slightly endergonic process.

Effect of the initial stage of annealing on modeling of enthalpy relaxation in a hyperquenched glass

DEFF Research Database (Denmark)

Zhang, Yanfei; Guo, Xiaoju; Yue, Yuanzheng

2013-01-01

One of the major challenges in glass relaxation study is to establish a universal model describing the enthalpy relaxation in both the hyperquenched glass (HQG) (i.e., far from equilibrium) and the partially annealed hyperquenched glass(AHQG). In particular, the detailed features of the enthalpy ...... proposed composite relaxation function [L. Hornboell, et al., Chem. Phys. Lett. 1-3 (2010) 37] is a reasonable approach for describing those features. In addition, our modeling results imply that the structural heterogeneity plays a crucial role in relaxation of HQG....

Excess molar enthalpies of binary systems containing 2-octanone, hexanoic acid, or octanoic acid at T = 298.15 K

International Nuclear Information System (INIS)

Liao, Wei-Chen; Lin, Ho-mu; Lee, Ming-Jer

2012-01-01

Highlights: → An isothermal titration calorimeter was used for enthalpy data measurement. → The investigated binary systems contain 2-octanone, hexanoic acid, or octanoic acid. → The excess enthalpies are all positive except for mixtures containing DMSO and DMF. → The Peng-Robinson equation with two parameters yielded the best representation. - Abstract: An isothermal titration calorimeter was used to measure the excess molar enthalpies (H E ) of six binary systems at T = 298.15 K under atmospheric pressure. The systems investigated include (1-hexanol + 2-octanone), (1-octanol + 2-octanone), (1-hexanol + octanoic acid), (1-hexanol + hexanoic acid), {N,N-dimethylformamide (DMF) + hexanoic acid}, and {dimethyl sulfoxide (DMSO) + hexanoic acid}. The values of excess molar enthalpies are all positive except for the DMSO- and the DMF-containing systems. In the 1-hexanol with hexanoic acid or octanoic acid systems, the maximum values of H E are located around the mole fraction of 0.4 of 1-hexanol, but the H E vary nearly symmetrically with composition for other four systems. In addition to the modified Redlich-Kister and the NRTL models, the Peng-Robinson (PR) and the Patel-Teja (PT) equations of state were used to correlate the excess molar enthalpy data. The modified Redlich-Kister equation correlates the H E data to within about experimental uncertainty. The calculated results from the PR and the PT are comparable. It is indicated that the overall average absolute relative deviations (AARD) of the excess enthalpy calculations are reduced from 18.8% and 18.8% to 6.6% and 7.0%, respectively, as the second adjustable binary interaction parameter, k bij , is added in the PR and the PT equations. Also, the NRTL model correlates the H E data to an overall AARD of 10.8% by using two adjustable model parameters.

Melting point gram-atomic volumes and enthalpies of atomization for liquid elements

International Nuclear Information System (INIS)

Lamoreaux, R.H.

1976-01-01

Values of the gram-atomic volumes and enthalpies of atomization to the monatomic ideal gas state for liquid elements at their melting points are collected to facilitate predictions of the behavior of mixed systems. Estimated values are given for experimentally undetermined quantities

Corollary from the Exact Expression for Enthalpy of Vaporization

OpenAIRE

A. A. Sobko

2011-01-01

A problem on determining effective volumes for atoms and molecules becomes actual due to rapidly developing nanotechnologies. In the present study an exact expression for enthalpy of vaporization is obtained, from which an exact expression is derived for effective volumes of atoms and molecules, and under certain assumptions on the form of an atom (molecule) it is possible to find their linear dimensions. The accuracy is only determined by the accuracy of measurements of thermodynamic paramet...

The vaporization enthalpy and vapor pressure of S (+)-methamphetamine at T = 298.15 K by correlation gas chromatography

International Nuclear Information System (INIS)

Thornton, Melissa; Gobble, Chase; Chickos, James

2014-01-01

Highlights: • The vaporization enthalpy of (d)-methamphetamine was measured. • The vapor pressure of (d)-methamphetamine as a function of temperature was evaluated. • The vapor pressure of 4-benzylpiperidine as a function of temperature was evaluated. - Abstract: The vaporization enthalpy and vapor pressure of S (+)-methamphetamine is evaluated by correlation-gas chromatography. A vaporization enthalpy of (58.7 ± 4.3) kJ · mol −1 and a vapor pressure, p = (38 ± 9) Pa has been obtained using a variety of secondary aliphatic amines as standards. In addition, equations describing the vapor pressure temperature dependence are provided for standards and S (+)-methamphetamine covering the temperature range from T = 298.15 K to the boiling temperature. Boiling temperatures are reproduced within an interval of 8 K or less

Vapor pressure and enthalpy of vaporization of oil of catnip by correlation gas chromatography

International Nuclear Information System (INIS)

Simmons, Daniel; Gobble, Chase; Chickos, James

2016-01-01

Highlights: • Vaporization enthalpies of the nepetalactones from oil of catnip have been evaluated. • Vapor pressures from T = (298.15 to 350) K have been evaluated. • Oil of catnip has a vapor pressure similar to DEET at T = 298.15 K. - Abstract: The vaporization enthalpy and vapor pressure of the two nepetalactones found in Nepeta cataria have been evaluated by correlation gas chromatography. Vaporization enthalpies at T = 298.15 K of {(68.0 ± 1.9) and (69.4 ± 1.9)} kJ ⋅ mol"−"1 have been derived for the minor diastereomer, (4aS,7S,7aS)-nepetalactone, and major one, (4aS,7S,7aR)-nepetalactone, respectively. Vapor pressures also at T = 298.15 K of p = (1.2 ± 0.04) Pa and (0.91 ± 0.03) Pa have been evaluated for the minor and the major stereoisomer. In addition to being of interest because of the remarkable effect it has on various felids, oil of catnip is also quite effective in repelling mosquitoes, comparable to diethyl-m-toluamide (DEET). The vapor pressures evaluated in this work suggest that the two stereoisomers have similar volatility to DEET at ambient temperatures.

Solution enthalpy of potassium iodide in furfural and its mixtures with dimethylsulfoxide

International Nuclear Information System (INIS)

Vlasenko, K.K.; Belov, A.A.; Vorob'ev, A.F.

1986-01-01

Solution enthalpy of potassium iodide in furfural-dimethylsulfoxide mixtures at 298.15 K and furfural concentration 17.3-100% are determined experimentally. K + and I - ion solvate shell composition, which in the general case doesn't correspond to the mixed solvent composition, is calculated

The vaporization enthalpies and vapor pressures of fatty acid methyl esters C18, C21 to C23, and C25 to C29 by correlation - gas chromatography

International Nuclear Information System (INIS)

Chickos, James S.; Zhao Hui; Nichols, Gary

2004-01-01

Vapor pressures and vaporization enthalpies for methyl heptadecanoate and methyl heneicosanoate to methyl octacosanoate exclusive of methyl tricosanoate are evaluated as a function of temperature over the temperature range T = 298.15-450 K by correlation gas chromatography. The results are generated by an extrapolative process using literature values for methyl tetradecanoate to methyl eicosanoate as standards. Relationships for calculating vapor pressures of the title compounds from T = 298.15 to 450 K are provided. Experimental fusion enthalpies are also reported for the methyl esters from methyl hexadecanoate to methyl octacosanoate excluding methyl tridecanoate. Vaporization enthalpies and fusion enthalpies adjusted for temperature to T = 298.15 K are combined to provide sublimation enthalpies. The results are compared to available literature values. A rationale for the linear relationship observed between enthalpies of vaporization and enthalpies of transfer from solution to the vapor is also provided

Calibration of a T-History calorimeter to measure enthalpy curves of phase change materials in the temperature range from 40 to 200 °C

International Nuclear Information System (INIS)

Rathgeber, Christoph; Schmit, Henri; Hennemann, Peter; Hiebler, Stefan

2014-01-01

Thermal energy storage using phase change materials (PCMs) provides high storage capacities in small temperature ranges. For the design of efficient latent heat storage, the enthalpy curve of a PCM has to be measured with high precision. Measurements are most commonly performed with differential scanning calorimetry (DSC). The T-History method, however, proved to be favourable for the characterization of typical PCMs due to large samples and a measuring procedure close to conditions found in applications. As T-History calorimeters are usually individual constructions, performing a careful calibration procedure is decisive to ensure optimal measuring accuracy. We report in this paper on the calibration of a T-History calorimeter with a working range from 40 to 200 °C that was designed and built at our institute. A three-part procedure, consisting of an indium calibration, a measurement of the specific heat of copper and measurements of three solid–liquid PCMs (stearic acid, dimethyl terephthalate and d-mannitol), was performed and an advanced procedure for the correction of enthalpy curves was developed. When comparing T-History enthalpy curves to literature data and DSC step measurements, good agreement within the uncertainty limits demanded by RAL testing specifications was obtained. Thus, our design of a T-History calorimeter together with the developed calibration procedure provides the measuring accuracy that is required to identify the most suitable PCM for a given application. In addition, the dependence of the enthalpy curve on the sample size can be analysed by comparing results obtained with T-History and DSC and the behaviour of the bulk material in real applications can be predicted. (paper)

Estimation of formation enthalpies of vanadates by Born-Gaber cycle method

International Nuclear Information System (INIS)

Golovkin, B.G.

1993-01-01

Principle possibility of calculating Gibbs energy of ionic compound formation as a function of thermochemical radii of component ions of temperature and pressure is shown. Formula for determination of thermochemical radii of polyatomic ions is suggested. Enthalpies of formation of 81 vanadates were estimated with the use of Kapustinsky equation and Born-Gaber cycle

Enthalpy of mixing and heat of vaporization of ethyl acetate with benzene and toluene at 298.15 k and 308.15 k

OpenAIRE

K. L. Shivabasappa; P. Nirguna Babu; Y. Jagannadha Rao

2008-01-01

The present work was carried out in two phases. First, enthalpy of mixing was measured and then the heat of vaporization for the same mixtures was obtained. The data are useful in the design of separation equipments. From the various designs available for the experimental determination of enthalpy of mixing, and heat of vaporization, the apparatus was selected, modified and constructed. The apparatus of enthalpy of mixing was tested with a known system Benzene - i-Butyl Alcohol and the data o...

Study of mixed radiative thermal mass transfer in the case of spherical liquide particle evaporation in a high temperature thermal air plasma

International Nuclear Information System (INIS)

Garandeau, S.

1984-01-01

Radiative transfer in a semi-transparent non-isothermal medium with spherical configuration has been studied. Limit conditions have been detailed, among which the semi-transparent inner sphere case is a new case. Enthalpy and matter transfer equations related to these different cases have been established. An adimensional study of local conservation laws allowed to reveal a parameter set characteristic of radiation coupled phenomena thermal conduction, convection, diffusion. Transfer equations in the case of evaporation of a liquid spherical particle in an air thermal plasma have been simplified. An analytical solution for matter transfer is proposed. Numerical solution of radiative problems and matter transfer has been realized [fr

Enthalpies of proton adsorption onto Bacillus licheniformis at 25, 37, 50, and 75 °C

Science.gov (United States)

Gorman-Lewis, Drew

2011-03-01

Understanding bacterial surface reactivity requires many different lines of investigation. Toward this end, we used isothermal titration calorimetry to measure heats of proton adsorption onto a Gram positive thermophile Bacillus licheniformis at 25, 37, 50, and 75 °C. Proton adsorption under all conditions exhibited exothermic heat production. Below pH 4.5, exothermic heats decreased as temperature increased above 37 °C; above pH 4.5, there was no significant difference in heats evolved at the temperatures investigated. Total proton uptake did not vary significantly with temperature. Site-specific enthalpies and entropies were calculated by applying a 4-site, non-electrostatic surface complexation model to the calorimetric data. Interpretation of site-specific enthalpies and entropies of proton adsorption for site L1, L2, and L4 are consistent with previous interpretations of phosphoryl, carboxyl, and hydroxyl/amine site-identities, respectively, and with previous calorimetric measurements of proton adsorption onto mesophilic species. Enthalpies and entropies for surface site L3 are not consistent with the commonly inferred phosphoryl site-identity and are more consistent with sulfhydryl functional groups. These results reveal intricacies of surface reactivity that are not detectable by other methods.

Molar enthalpy of mixing and refractive indices of choline chloride-based deep eutectic solvents with water

International Nuclear Information System (INIS)

Ma, Chunyan; Guo, Yanhua; Li, Dongxue; Zong, Jianpeng; Ji, Xiaoyan; Liu, Chang

2017-01-01

Highlights: • Molar enthalpy of mixing and refractive indices for binary mixtures of different deep eutectic solvents with water. • The Redlich–Kister equation and the NRTL model was used to fit the experimental data. • The NRTL model with fitted parameters were used to predict the vapour pressure and compared with experimental data. - Abstract: The molar enthalpies of mixing were measured for binary systems of choline chloride-based deep eutectic solvents (glycerol, ethylene glycol and malonic acid) with water at 298.15 K and 308.15 K, and atmospheric pressure with an isothermal calorimeter. Refractive indices were also measured at 303.15 K and atmospheric pressure. The binary mixtures of {chcl/glycerol (1:2) + water, chcl/ethylene glycol (1:2) + water} showed exothermic behaviour over the entire range of composition, while the binary mixture of {chcl/malonic acid (1:1) + water} showed endothermic behaviour at first and then changed to be exothermic with the increasing content of chcl/malonic acid (1:1). Experimental refractive indices were fitted with the Redlich–Kister equation, and experimental molar enthalpies of mixing were correlated with the Redlich–Kister equation and the non-random two-liquid (NRTL) model. The NRTL model with the fitted parameters was used to predict the vapour pressures of these three mixtures. For mixtures of {chcl/glycerol (1:2) + water} and {chcl/ethylene glycol (1:2) + water}, the predicted vapour pressures agreed well with the experimental results from the literature. While for mixture of {chcl/malonic acid (1:1) + water}, the predicted vapour pressures showed deviation at the high concentration of chcl/malonic acid (1:1), and this was probably because of the complex molecular interaction between chcl/malonic acid (1:1) and water.

EXCESS MOLAR ENTHALPIES OF 1-OCTENE + DIMETHYLCARBONATE OR DIETHYLCARBONATE OR 1,2-PROPYLCARBONATE AT 363.15 K AND 413.15 K

Directory of Open Access Journals (Sweden)

M. A. KRÄHENBÜHL

1998-03-01

Full Text Available The excess molar enthalpies of 1-octene + dimethylcarbonate or diethylcarbonate or 1,2-propylcarbonate have been measured at two high temperatures 363.15 K and 413.15 K and for pressures varying from 18 to 20 bar with an isothermal flow-calorimeter. All these mixtures have exhibited positive HEm.

A method for the estimation of the enthalpy of formation of mixed oxides in Al2O3-Ln2O3 systems

International Nuclear Information System (INIS)

Vonka, P.; Leitner, J.

2009-01-01

A new method is proposed for the estimation of the enthalpy of formation (Δ ox H) of various Al 2 O 3 -Ln 2 O 3 mixed oxides from the constituent binary oxides. Our method is based on Pauling's concept of electronegativity and, in particular, on the relation between the enthalpy of formation of a binary oxide and the difference between the electronegativities of the oxide-forming element and oxygen. This relation is extended to mixed oxides with a simple formula given for the calculation of Δ ox H. The parameters of this equation were fitted using published experimental values of Δ ox H derived from high-temperature oxide melt solution calorimetry. Using our proposed method, we obtained a standard deviation (σ) of 4.87 kJ mol -1 for this data set. Taking into account regularities within the lanthanide series, we then estimated the Δ ox H values for Al 2 O 3 -Ln 2 O 3 mixed oxides. The values estimated using our method were compared with those obtained by Aronson's and Zhuang's empirical methods, both of which give significantly poorer results. - Graphical abstract: Enthalpy of formation of Ln-Al-O oxides from the constituent binary ones.

The system analysis of temperature and melting enthalpy of intermetallic compounds of antimony-lanthanoids system of Sb Ln, Sb2Ln composition

International Nuclear Information System (INIS)

Badalova, M.A.; Chamanova, M.; Dodkhoev, E.S.; Badalov, A.; Abdusalyamova, M.N.

2015-01-01

Present article is devoted to system analysis of temperature and melting enthalpy of intermetallic compounds of antimony-lanthanoids system of Sb Ln, Sb 2 Ln composition. The melting enthalpy was estimated. The temperature value was determined.

The standard enthalpies of formation of L-asparagine and L-{alpha}-glutamine

Energy Technology Data Exchange (ETDEWEB)

Contineanu, Iulia, E-mail: icontineanu@yahoo.com [Institute of Physical Chemistry ' I.G. Murgulescu' , Spl. Independentei 202, Bucharest (Romania); Neacsu, Ana, E-mail: anna_matache@yahoo.com [Institute of Physical Chemistry ' I.G. Murgulescu' , Spl. Independentei 202, Bucharest (Romania); Perisanu, Stefan T., E-mail: stefan.perisanu@upb.ro [Laboratory of General Chemistry, Polytechnic University of Bucharest, str. Polizu nr. 1, Bucuresti (Romania)

2010-01-10

The energies of combustion of L-asparagine and L-{alpha}-glutamine were measured in a static bomb adiabatic calorimeter. Corrections were made for the heats due to the ignition of sample and for the nitric acid formation. The derived enthalpies of formation in solid state of asparagine monohydrate, nonhydrated asparagine and glutamine are respectively -1084.1 {+-} 3.0, -788.1 {+-} 4.7 and -834.3 {+-} 4.6 kJ mol{sup -1}. The data of enthalpy of formation are compared with the literature values and with estimated values by means of group additivity, using parameters recommended by Domalski and Hearing. The discrepancies between experimental and calculated values are explained by considering the number and strength of intermolecular hydrogen bonds. The dehydration of asparagine monohydrate and the possible melting of the three amino acids were investigated by means of DSC. Glutamine melts without considerable decomposition at about 182 {sup o}C, while asparagines decompose during the fusion process (208 {sup o}C).

Enthalpies of solution of N,N,N',N'-tetramethylurea in amides, dimethylsulphoxide, and acetone at 298.15 K

International Nuclear Information System (INIS)

Ivanov, Evgeniy V.; Smirnov, Valeriy I.

2008-01-01

The enthalpies of solution Δ sol H m m were determined for N,N,N',N'-tetramethylurea in formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, and acetone. Measurements were made at 298.15 K and molalities m = (0.004 to 0.031) mol . kg -1 with a precise isoperibol ampoule-type calorimeter. Standard enthalpies of solution Δ sol H m 0 and transfer Δ tr H m 0 from one solvent to another were computed. The enthalpies of solution of the solute in the hydrogen-non-bonding media were found to be endothermic and weak depending on the nature of methylation in a solvent molecule. It was concluded that the solvent proton-donor ability and existing steric hindrances for hydrogen bonding and other intermolecular interactions play the key role in solvation of tetramethylurea

Experimental investigation of the enthalpy and mass flow distribution between subchannels in a BWR cluster geometry (PELCO-S)

International Nuclear Information System (INIS)

Herkenrath, H.; Hufschmidt, W.

1979-01-01

Experiments based on the subchannel isokinetic technique have been carried out at the JRC of the European Community at Ispra, using a purposely designed 16-rod test section, simulating in a rather accurate way a typical BWR geometry. The adopted system allows the simultaneous determination of mass flow and enthalpy, at the end of the bundle active length, in four characteristic subchannels of the 16-rod lattice. The results show some pronounced flow and enthalpy variations within the bundle, not accurately taken into account by current subchannel codes, such as COBRA-3C. In particular low values both in mass flow and enthalpy have been found in corner subchannel, in disagreement with code predictions, but confirming previous General Electric experiments carried out in a 9-rod test section. This report deals only with the experimental procedure and the results

Down-Hole Heat Exchangers: Modelling of a Low-Enthalpy Geothermal System for District Heating

Directory of Open Access Journals (Sweden)

M. Carlini

2012-01-01

Full Text Available In order to face the growing energy demands, renewable energy sources can provide an alternative to fossil fuels. Thus, low-enthalpy geothermal plants may play a fundamental role in those areas—such as the Province of Viterbo—where shallow groundwater basins occur and conventional geothermal plants cannot be developed. This may lead to being fuelled by locally available sources. The aim of the present paper is to exploit the heat coming from a low-enthalpy geothermal system. The experimental plant consists in a down-hole heat exchanger for civil purposes and can supply thermal needs by district heating. An implementation in MATLAB environment is provided in order to develop a mathematical model. As a consequence, the amount of withdrawable heat can be successfully calculated.

Interaction of a weak and a strong shock in reacting high enthalpy flow; Wechselwirkung einer starken und einer schwachen Stosswelle in reagierender Hochenthalpiestroemung

Energy Technology Data Exchange (ETDEWEB)

Schnieder, M.

1998-11-01

In the free piston driven shock tunnel HEG the interaction of shock waves in front of a blunt body is studied in reacting high enthalpy flow. The influence of high temperature effects is of interest. The so called type IV interaction produces a free jet that impinges onto the body and creates high pressure and heat loads on the body surface. A cylinder wedge model is used. At the cylinder surface pressure and heat flux are measured. Holographic interferometry and schlieren optic are applied to visualize the flow. The measured loads show unsteady behaviour. At higher Reynolds numbers the upper bow shock shows a strong disturbance. It is assumed that this disturbance is caused by an unstable shear layer if the convective Mach number (i.e. the Mach number of the flow relative to a frame of reference moving with the shear layer structures) is larger than one. A study of the influence of dissociation on the convective Mach number shows, that the convective Mach number increases. Numerical calculations and an analytical model, which is based on the ideal dissociating gas model and the Fay Riddell solution to stagnation point flows are discussed in comparison with the experiments. (orig.)

Vapor pressures and vaporization enthalpy of (−) α-bisabolol and (dl) menthol by correlation gas chromatography

International Nuclear Information System (INIS)

Keating, Leasa; Harris, Harold H.; Chickos, James S.

2017-01-01

Highlights: • The vaporization enthalpy and vapor pressure of (−) α-bisabolol and (dl)-menthol have been measured as a function of temperature. • Vapor pressures, vaporization enthalpies and boiling temperatures have been compared to available literature data. • Vapor pressures of (l)-menthol are compared to (dl)-menthol. - Abstract: The vapor pressures and vaporization enthalpies of (−) α-bisabolol and (dl)-menthol, two GRAS chemicals (generally recognized as safe) are evaluated by correlation gas chromatography using a series of saturated primary alcohols as standards. Vaporization enthalpies of (96.6 ± 2.4) and (74.2 ± 2.8) kJ mol −1 and vapor pressures of p/Pa = (0.020 ± 0.003) and (4.5 ± 0.44) were evaluated at T = 298.15 K for (−) α-bisabolol and (dl)-menthol, respectively, and compared to literature values. The vapor pressures of both compounds from T = (298.15 to 500) K have been derived from correlations using vapor pressures of a series of 1-alkanols and corresponding gas chromatographic retention times at 10 K intervals. The results were fit to a second order polynomial. Calculated normal boiling temperatures of T B = (574.8 and 492.7) K are calculated for (−) α-bisabolol and (dl)-menthol, respectively. A normal boiling temperature of T B = (485.2, and 489.7) K has previously been reported for (dl)-menthol. Vapor pressures for both (l)-menthol and (dl)-menthol from a previous study and (dl)-menthol from this study are compared with literature values.

Calculation of partial enthalpies in argon-krypton mixtures by NPT molecular dynamics

NARCIS (Netherlands)

Sindzingre, P.; Massobrio, C.; Ciccotti, G.; Frenkel, D.

1989-01-01

In an earlier paper, we have indicated how, by using a particle-insertion technique, partial molar enthalpies and related quantities can be evaluated from simulations on a single state point. In the present paper we apply this method to a Lennard-Jones argon-krypton mixture. For this particular

Experimental-numerical study of heat flow in deep low-enthalpy geothermal conditions

NARCIS (Netherlands)

Saeid, S.; Al-Khoury, R.; Nick, H.M.; Barends, F.

2014-01-01

This paper presents an intensive experimental-numerical study of heat flow in a saturated porous domain. A temperature and a flow rate range compared to that existing in a typical deep low-enthalpy hydrothermal system is studied. Two main issues are examined: the effect of fluid density and

Standard molar enthalpies of formation of 2-chloroquinoline, 4-chloroquinoline, 6-chloroquinoline and 4,7-dichloroquinoline by rotating-bomb calorimetry

International Nuclear Information System (INIS)

Ribeiro da Silva, Manuel A.V.; Matos, Maria Agostinha R.; Amaral, Luisa M.P.F.

2006-01-01

The standard (p o =0.1MPa) molar enthalpies of combustion, Δ c H m - bar , for crystalline 2-, 4-, 6-chloroquinoline and 4,7-dichloroquinoline were determined at the temperature 298.15K using a rotating-bomb combustion calorimeter. The standard molar enthalpies of sublimation, Δ cr g H m o , at T= 298.15K, were determined by Calvet microcalorimetry. The results were as follows: -Δ c H m o (cr)/(kJ.mol -1 )Δ cr g H m o /(kJ.mol -1 )2-Chloroquinoline4492.5+/-1.684.3+/-2.64-Chloroquinoline4508.4 +/ -1.678.6+/-1.76-Chloroquinoline4508.2+/-1.680.8+/-1.94,7-Dichloroquinoline 4353.3+/-1.389.5+/-2.3 These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively. The derived standard molar enthalpies of formation, in the gaseous state, are analysed in terms of enthalpic increments and interpreted in terms of molecular structure

ENTHALPY EU PROJECT: ENABLING THE DRYING PROCESS TO SAVE ENERGY AND WATER, REALISING PROCESS EFFICIENCY IN THE DAIRY CHAIN

OpenAIRE

Berta ALVAREZ PENEDO; Sandra FORSTNER; Alexandru RUSU

2016-01-01

The EU funded ENTHALPY project aims to significantly reduce the consumption of water and energy in milk powder production to increase efficiency in the dairy production chain. Using a systematic approach, ENTHALPY project focusses on innovations within the post-harvest chain representing the highest energy and water consumption such as RF heating, solar thermal energy, mono-disperse atomising, dryer modelling, inline monitoring, enzymatic cleaning and membrane technology,

The Role of Structural Enthalpy in Spherical Nucleic Acid Hybridization.

Science.gov (United States)

Fong, Lam-Kiu; Wang, Ziwei; Schatz, George C; Luijten, Erik; Mirkin, Chad A

2018-05-23

DNA hybridization onto DNA-functionalized nanoparticle surfaces (e.g., in the form of a spherical nucleic acid (SNA)) is known to be enhanced relative to hybridization free in solution. Surprisingly, via isothermal titration calorimetry, we reveal that this enhancement is enthalpically, as opposed to entropically, dominated by ∼20 kcal/mol. Coarse-grained molecular dynamics simulations suggest that the observed enthalpic enhancement results from structurally confining the DNA on the nanoparticle surface and preventing it from adopting enthalpically unfavorable conformations like those observed in the solution case. The idea that structural confinement leads to the formation of energetically more stable duplexes is evaluated by decreasing the degree of confinement a duplex experiences on the nanoparticle surface. Both experiment and simulation confirm that when the surface-bound duplex is less confined, i.e., at lower DNA surface density or at greater distance from the nanoparticle surface, its enthalpy of formation approaches the less favorable enthalpy of duplex formation for the linear strand in solution. This work provides insight into one of the most important and enabling properties of SNAs and will inform the design of materials that rely on the thermodynamics of hybridization onto DNA-functionalized surfaces, including diagnostic probes and therapeutic agents.

A Simple Experiment for Determining Vapor Pressure and Enthalpy of Vaporization of Water.

Science.gov (United States)

Levinson, Gerald S.

1982-01-01

Laboratory procedures, calculations, and sample results are described for a freshman chemistry experiment in which the Clausius-Clapeyron equation is introduced as a means of describing the variation of vapor pressure with temperature and for determining enthalpy of vaporization. (Author/SK)

Enthalpy-entropy compensation for the solubility of drugs in solvent mixtures: paracetamol, acetanilide, and nalidixic acid in dioxane-water.

Science.gov (United States)

Bustamante, P; Romero, S; Pena, A; Escalera, B; Reillo, A

1998-12-01

In earlier work, a nonlinear enthalpy-entropy compensation was observed for the solubility of phenacetin in dioxane-water mixtures. This effect had not been earlier reported for the solubility of drugs in solvent mixtures. To gain insight into the compensation effect, the behavior of the apparent thermodynamic magnitudes for the solubility of paracetamol, acetanilide, and nalidixic acid is studied in this work. The solubility of these drugs was measured at several temperatures in dioxane-water mixtures. DSC analysis was performed on the original powders and on the solid phases after equilibration with the solvent mixture. The thermal properties of the solid phases did not show significant changes. The three drugs display a solubility maximum against the cosolvent ratio. The solubility peaks of acetanilide and nalidixic acid shift to a more polar region at the higher temperatures. Nonlinear van't Hoff plots were observed for nalidixic acid whereas acetanilide and paracetamol show linear behavior at the temperature range studied. The apparent enthalpies of solution are endothermic going through a maximum at 50% dioxane. Two different mechanisms, entropy and enthalpy, are suggested to be the driving forces that increase the solubility of the three drugs. Solubility is entropy controlled at the water-rich region (0-50% dioxane) and enthalpy controlled at the dioxane-rich region (50-100% dioxane). The enthalpy-entropy compensation analysis also suggests that two different mechanisms, dependent on cosolvent ratio, are involved in the solubility enhancement of the three drugs. The plots of deltaH versus deltaG are nonlinear, and the slope changes from positive to negative above 50% dioxane. The compensation effect for the thermodynamic magnitudes of transfer from water to the aqueous mixtures can be described by a common empirical nonlinear relationship, with the exception of paracetamol, which follows a separate linear relationship at dioxane ratios above 50%. The

The CPA Equation of State and an Activity Coefficient Model for Accurate Molar Enthalpy Calculations of Mixtures with Carbon Dioxide and Water/Brine

Energy Technology Data Exchange (ETDEWEB)

Myint, P. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hao, Y. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Firoozabadi, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2015-03-27

Thermodynamic property calculations of mixtures containing carbon dioxide (CO₂) and water, including brines, are essential in theoretical models of many natural and industrial processes. The properties of greatest practical interest are density, solubility, and enthalpy. Many models for density and solubility calculations have been presented in the literature, but there exists only one study, by Spycher and Pruess, that has compared theoretical molar enthalpy predictions with experimental data [1]. In this report, we recommend two different models for enthalpy calculations: the CPA equation of state by Li and Firoozabadi [2], and the CO₂ activity coefficient model by Duan and Sun [3]. We show that the CPA equation of state, which has been demonstrated to provide good agreement with density and solubility data, also accurately calculates molar enthalpies of pure CO₂, pure water, and both CO₂-rich and aqueous (H₂O-rich) mixtures of the two species. It is applicable to a wider range of conditions than the Spycher and Pruess model. In aqueous sodium chloride (NaCl) mixtures, we show that Duan and Sun’s model yields accurate results for the partial molar enthalpy of CO₂. It can be combined with another model for the brine enthalpy to calculate the molar enthalpy of H₂O-CO₂-NaCl mixtures. We conclude by explaining how the CPA equation of state may be modified to further improve agreement with experiments. This generalized CPA is the basis of our future work on this topic.

A Lithium-Air Battery Stably Working at High Temperature with High Rate Performance.

Science.gov (United States)

Pan, Jian; Li, Houpu; Sun, Hao; Zhang, Ye; Wang, Lie; Liao, Meng; Sun, Xuemei; Peng, Huisheng

2018-02-01

Driven by the increasing requirements for energy supply in both modern life and the automobile industry, the lithium-air battery serves as a promising candidate due to its high energy density. However, organic solvents in electrolytes are likely to rapidly vaporize and form flammable gases under increasing temperatures. In this case, serious safety problems may occur and cause great harm to people. Therefore, a kind of lithium-air that can work stably under high temperature is desirable. Herein, through the use of an ionic liquid and aligned carbon nanotubes, and a fiber shaped design, a new type of lithium-air battery that can effectively work at high temperatures up to 140 °C is developed. Ionic liquids can offer wide electrochemical windows and low vapor pressures, as well as provide high thermal stability for lithium-air batteries. The aligned carbon nanotubes have good electric and heat conductivity. Meanwhile, the fiber format can offer both flexibility and weavability, and realize rapid heat conduction and uniform heat distribution of the battery. In addition, the high temperature has also largely improved the specific powers by increasing the ionic conductivity and catalytic activity of the cathode. Consequently, the lithium-air battery can work stably at 140 °C with a high specific current of 10 A g -1 for 380 cycles, indicating high stability and good rate performance at high temperatures. This work may provide an effective paradigm for the development of high-performance energy storage devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exergy analysis of an adiabatic compressed air energy storage system using a cascade of phase change materials

International Nuclear Information System (INIS)

Tessier, Michael J.; Floros, Michael C.; Bouzidi, Laziz; Narine, Suresh S.

2016-01-01

Adiabatic compressed air energy storage is an emerging energy storage technology with excellent power and storage capacities. Currently, efficiencies are approximately 70%, in part due to the issue of heat loss during the compression stage. An exergy analysis is presented on a novel adiabatic compressed air energy storage system design utilizing a cascade of PCMs (phase change materials) for waste heat storage and recovery. The melting temperatures and enthalpies of the PCMs were optimized for this system and were shown to be dependent on the number of PCMs, the number of compression stages, and the maximum compression ratio. Efficiencies of storage and recovery using this approach are predicted to be as high as 85%, a 15% increase over current designs which do not incorporate PCMs. - Highlights: • A compressed air energy storage plant using phase change materials is proposed. • Increasing number of phase change materials increases roundtrip exergy efficiency. • A thermodynamic model allows melting points and latent heats required to be predicted.

High-throughput liquid-absorption air-sampling apparatus and methods

Science.gov (United States)

Zaromb, Solomon

2000-01-01

A portable high-throughput liquid-absorption air sampler [PHTLAAS] has an asymmetric air inlet through which air is drawn upward by a small and light-weight centrifugal fan driven by a direct current motor that can be powered by a battery. The air inlet is so configured as to impart both rotational and downward components of motion to the sampled air near said inlet. The PHTLAAS comprises a glass tube of relatively small size through which air passes at a high rate in a swirling, highly turbulent motion, which facilitates rapid transfer of vapors and particulates to a liquid film covering the inner walls of the tube. The pressure drop through the glass tube is 20% for vapors or airborne particulates in the 2-3.mu. range and >50% for particles larger than 4.mu.. In conjunction with various analyzers, the PHTLAAS can serve to monitor a variety of hazardous or illicit airborne substances, such as lead-containing particulates, tritiated water vapor, biological aerosols, or traces of concealed drugs or explosives.

High-throughput liquid-absorption air-sampling apparatus and methods

International Nuclear Information System (INIS)

2000-01-01

A portable high-throughput liquid-absorption air sampler [PHTLAAS] has an asymmetric air inlet through which air is drawn upward by a small and light-weight centrifugal fan driven by a direct current motor that can be powered by a battery. The air inlet is so configured as to impart both rotational and downward components of motion to the sampled air near said inlet. The PHTLAAS comprises a glass tube of relatively small size through which air passes at a high rate in a swirling, highly turbulent motion, which facilitates rapid transfer of vapors and particulates to a liquid film covering the inner walls of the tube. The pressure drop through the glass tube is 20% for vapors or airborne particulates in the 2--3 microns range and > 50% for particles larger than 4 microns. In conjunction with various analyzers, the PHTLAAS can serve to monitor a variety of hazardous or illicit airborne substances, such as lead-containing particulates, tritiated water vapor, biological aerosols, or traces of concealed drugs or explosives

Vapor pressures and enthalpies of vaporization of a series of 1- and 2-halogenated naphthalenes

International Nuclear Information System (INIS)

Verevkin, Sergey P.

2003-01-01

Molar enthalpies of vaporization, Δ l g H m 0 , of 1-methyl-naphthalene, 1-chloro-napthalene, 2-chloro-naphthalene, 1-bromo-naphthalene, 2-bromo-naphthalene, and 1-iodo-naphthalene, as well as molar enthalpies of sublimation, Δ s g H m 0 , of 2-chloro-naphthalene and 2-bromo-naphthalene have been obtained from the temperature dependence of the vapor pressure determined with the transpiration method. These values and the correlation gas-chromatography method, based on the Kovat's index, have been used to determine Δ l g H m 0 and Δ s g H m 0 of 2-iodo-naphthalene. Results obtained in this work have been compared with those from the literature and found consistent

Measurement of polyurethane foam - air partition coefficients for semivolatile organic compounds as a function of temperature: Application to passive air sampler monitoring.

Science.gov (United States)

Francisco, Ana Paula; Harner, Tom; Eng, Anita

2017-05-01

Polyurethane foam - air partition coefficients (K PUF-air ) for 9 polycyclic aromatic hydrocarbons (PAHs), 10 alkyl-substituted PAHs, 4 organochlorine pesticides (OCPs) and dibenzothiophene were measured as a function of temperature over the range 5 °C-35 °C, using a generator column approach. Enthalpies of PUF-to-air transfer (ΔH PUF-air , kJ/mol) were determined from the slopes of log K PUF-air versus 1000/T (K), and have an average value of 81.2 ± 7.03 kJ/mol. The log K PUF-air values at 22 °C ranged from 4.99 to 7.25. A relationship for log K PUF-air versus log K OA was shown to agree with a previous relationship based on only polychlorinated biphenyls (PCBs) and derived from long-term indoor uptake study experiments. The results also confirm that the existing K OA -based model for predicting log K PUF-air values is accurate. This new information is important in the derivation of uptake profiles and effective air sampling volumes for PUF disk samplers so that results can be reported in units of concentration in air. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Enthalpies of Dissolution of Crystalline Naproxen Sodium in Water and Potassium Hydroxide Aqueous Solutions at 298 K

Science.gov (United States)

Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.; Bychkova, S. A.; Volkov, A. V.; Skvortsov, I. A.

2018-03-01

The enthalpies of dissolution of crystalline naproxen sodium in water and aqueous solutions of KOH at 298.15 K are measured by direct calorimetric means in a wide range of concentrations. The acid-base properties of naproxen sodium at ionic strength I 0 and I = 0.1 (KNO3) and a temperature of 298.15 K are studied by spectrophotometric means. The concentration and thermodynamic dissociation constants are determined. The standard enthalpies of the formation of naproxen sodium and the products of its dissociation in aqueous solution are calculated.

Investigation on the transient enthalpy of coal combustion

Energy Technology Data Exchange (ETDEWEB)

Fu, Pei-fang; Wang, Na; Yu, Bo; Zhang, Bin; Liu, Yang; Zhou, Huai-chun [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

2013-07-01

The transient enthalpy ({Delta}h) of coal/char combustion of the three different coals (including anthracite, bituminous, and lignite) during the process of combustion is determined as a function of burn-off degree by using thermo-gravimetric-differential scanning calorimeter (TG-DSC) simultaneous thermal analyzer, and The error of determining calorific values of coals/chars is less 5% compared the results of TG-DSC with that of an automatic isoperibol calorimeter. It is found that In the initial stage, all the {Delta}h of coals are greater than that of the char pyrolysized from parent coal for many of volatiles contained more a great deal of heat per unit mass oxidized at low temperature, it also imply that coal is more easily ignited than char corresponded; And in the middle stage, all the {Delta}h of coals is lower than that of the char pyrolysized, so the pyrolysized char oxidation can supply much more of thermo-energy per unit mass. {Delta}h are almost a constant when the burn-off degree is equal to between 0.35/0.15 and 0.95/0.85 for ZCY bituminous coal/char and JWY anthracite/char, between 0.35/0.35 and 0.75/0.9 for SLH lignite/char; In the later stage, the {Delta}h of the coal/char decreased with the burn-off degree, it imply that the activity of the coal/char decreases. Therefore, coal pyrolysis changes not only the structure of char, but also the property of release heat; the transient enthalpy of coal/char combustion has been in change with the burn-out degree.

Effect of halogen substitution on the enthalpies of solvation and hydrogen bonding of organic solutes in chlorobenzene and 1,2-dichlorobenzene derived using multi-parameter correlations

Energy Technology Data Exchange (ETDEWEB)

Varfolomeev, Mikhail A.; Rakipov, Ilnaz T.; Khachatrian, Artashes A. [Department of Physical Chemistry, Kazan Federal University, Kremlevskaya 18, Kazan 420008 (Russian Federation); Acree, William E., E-mail: acree@unt.edu [Department of Chemistry, 1155 Union Circle # 305070, University of North Texas, Denton, TX 76203-5017 (United States); Brumfield, Michela [Department of Chemistry, 1155 Union Circle # 305070, University of North Texas, Denton, TX 76203-5017 (United States); Abraham, Michael H. [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

2015-10-10

Graphical abstract: - Highlights: • Enthalpies of solution measured for 43 solutes dissolved in chlorobenzene. • Enthalpies of solution measured for 72 solutes dissolved in 1,2-dichlorobenzene. • Mathematical expressions derived for predicting enthalpies of solvation of solutes in chlorobenzene. • Mathematical expressions derived for predicting enthalpies of solvation of solutes in 1,2-chlorobenzene. - Abstract: Enthalpies of solution at infinite dilution at 298 K, Δ{sub soln}H{sup A/Solvent}, have been measured by isothermal solution calorimetry for 43 and 72 organic solutes dissolved in chlorobenzene and 1,2-dichlorobenzene, respectively. The measured Δ{sub soln}H{sup A/Solvent} data, along with published Δ{sub soln}H{sup A/Solvent} values taken from the published literature for solutes dissolved in both chlorobenzene solvents, were converted to enthalpies of solvation, Δ{sub solv}H{sup A/Solvent}, using standard thermodynamic equations. Abraham model correlations were developed from the experimental Δ{sub solv}H{sup A/Solvent} data. The best derived correlations describe the experimental gas-to-chlorobenzene and gas-to-1,2-dichlorobenzene enthalpies of solvation to within standard deviations of 1.5 kJ mol{sup −1} and 1.9 kJ mol{sup −1}, respectively. Enthalpies of X−H…π (X – O, N, and C) hydrogen bond formation of proton donor solutes (alcohols, amines, chlorinated hydrocarbons, etc.) with chlorobenzene and 1,2-dichlorobenzene were calculated based on the Abraham solvation equation. Obtained values are in good agreement with the results determined using conventional methods.

ENTHALPY EU PROJECT: ENABLING THE DRYING PROCESS TO SAVE ENERGY AND WATER, REALISING PROCESS EFFICIENCY IN THE DAIRY CHAIN

Directory of Open Access Journals (Sweden)

Berta ALVAREZ PENEDO

2016-11-01

Full Text Available The EU funded ENTHALPY project aims to significantly reduce the consumption of water and energy in milk powder production to increase efficiency in the dairy production chain. Using a systematic approach, ENTHALPY project focusses on innovations within the post-harvest chain representing the highest energy and water consumption such as RF heating, solar thermal energy, mono-disperse atomising, dryer modelling, inline monitoring, enzymatic cleaning and membrane technology,

Isosteric Vapor Pressure – Temperature Data for Water Sorption in Hardened Cement Paste: Enthalpy, Entropy and Sorption Isotherms at Different Temperatures

DEFF Research Database (Denmark)

Radjy, Fariborz; Sellevold, Erik J.; Hansen, Kurt Kielsgaard

. The accuracies for pressure, enthalpy and entropy are found to be 0.5% or less. PART II: The TPA-system has been used to generate water vapor pressure – temperature data for room temperature – and steam cured hardened cement pastes as well as porous vycor glass. The moisture contents range from saturated to dry...... and the temperatures range from 2 to 95 °C, differing for the specimen types. The data has been analyzed to yield differential enthalpy and entropy of adsorption, as well as the dependence of the relative vapor pressure on temperature at various constant moisture contents. The implications for the coefficient......PART I: In order to generate isosteric (constant mass) vapor pressure – temperature data (P-T data) for adsorbed pore water in hydrated cement paste, the Thermo Piestic Analysis system (the TPA system) described herein was developed. The TPA system generates high precision equilibrium isosteric P...

Determination of molar enthalpy of sublimation in case of orotic acid as obtained from experimental and computational data

Science.gov (United States)

Marochkin, Ilya I.; Altova, Ekaterina P.; Chilingarov, Norbert S.; Vilkova, Anna L.; Shishkov, Igor F.

2018-03-01

Saturated vapor pressure, ln(p/Pa) = (-21316 ± 511)/(T/K)+(41.64 ± 0.11), and enthalpy of sublimation of orotic acid, Δsub Hm0 (Tm) = 177 ± 4 kJ/mol, were determined by means of Knudsen effusion mass spectrometry in the temperature range of 423÷493 K. The computational approaches supported the experimental results reported. The theoretical estimation of the gas-phase enthalpy of formation for orotic acid was done with different working reactions used.

Relation between the adsorbed quantity and the immersion enthalpy in catechol aqueous solutions on activated carbons.

Science.gov (United States)

Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

2012-01-01

An activated carbon, Carbochem(TM)-PS230, was modified by chemical and thermal treatment in flow of H(2), in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pK(a). The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g(-1) for catechol aqueous solutions in a range of 20 at 1500 mg·L(-1).

Relation Between the Adsorbed Quantity and the Immersion Enthalpy in Catechol Aqueous Solutions on Activated Carbons

Directory of Open Access Journals (Sweden)

Liliana Giraldo

2011-12-01

Full Text Available An activated carbon, CarbochemTM—PS230, was modified by chemical and thermal treatment in flow of H2, in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pKa. The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG, the immersion enthalpies obtained are between 21.5 and 45.7 J·g−1 for catechol aqueous solutions in a range of 20 at 1500 mg·L−1.

Vapor pressures and enthalpies of vaporization of a series of the linear aliphatic aldehydes

Czech Academy of Sciences Publication Activity Database

Verevkin, S. P.; Krasnykh, E. L.; Vasiltsova, T. V.; Koutek, Bohumír; Doubský, Jan; Heintz, A.

2003-01-01

Roč. 206, - (2003), s. 331-339 ISSN 0378-3812 Institutional research plan: CEZ:AV0Z4055905 Keywords : aldehydes * vapor pressure * enthalpy of vaporization Subject RIV: CC - Organic Chemistry Impact factor: 1.165, year: 2003

Enthalpy model for heating, melting, and vaporization in laser ablation

OpenAIRE

Vasilios Alexiades; David Autrique

2010-01-01

Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu) target in a helium (He) background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model th...

On determination of enthalpies of complex formation reactions by means of temperature coefficient of complexing degree

International Nuclear Information System (INIS)

Povar, I.G.

1995-01-01

Equations describing the relation between temperature coefficient of ∂lnα/∂T complexing degree and the sum of changes in the enthalpy of complex formation of the composition M m L n δH mn multiplied by the weight coefficients k mm , are presented. A method to determine changes in the enthalpy of certain ΔH mm reactions from ∂lnα/∂T derivatives has been suggested. The best approximating equation from lnα/(T) dependence has been found. Errors of thus determined δH mm values are estimated and the results of calculation experiment for the system In 3+ -F - are provided. 10 refs., 2 figs., 3 tabs

The relation between inversion enthalpy and adsorption parameters for an activated carbon in aqueous Pb2+ solutions

International Nuclear Information System (INIS)

Giraldo, Liliana; Moreno, Juan Carlos

2006-01-01

We report the preparation of an activated carbon obtained by impregnation of mineral carbon samples with a phosphoric acid solution (50%).The obtained material, exhibits a superficial area of 586 m 2 .g -1 and a total pore volume of 0.37 cm 3 g -1 . With respect to the chemical properties, the activated carbon shows an increased number of acidic sites (0.92 meq g -l ) compared to basic sites (0.63 meq g-1) which yields a material with almost neutral characteristics (PHpzc: 7.4). At a pH: 4.0 the amount of Pb 2 + absorbed and the immersion enthalpy values for the activated carbon reached a maximum with values of 15.7 mg -1 y 27.6 Jg -1 respectively. It was established that similar behaviour occurs for the two properties, absorption and immersion enthalpy, as a function of pH. In addition, a second order function that relates the adsorption constant and immersion enthalpy, and the adsorption constant and pH of the solution are presented

The relation between immersion enthalpy and adsorption parameters for an activated carbon in aqueous Pb2+solutions

International Nuclear Information System (INIS)

Girado, Liliana; Moreno, Juan Carlos

2006-01-01

We report the preparation of an activated carbon obtained by impregnation of mineral carbon samples with phosphoric acid solution (50%). the obtained material, exhibits a superficial area of 586 m 2 .g -1 and a total pore volume of 0,37 cm 3 g -1 . with respect to the chemical properties, the activated carbon shows an increased number of acidic sites (0,92 meq g -1 ) compared to basic sites (0,63 meq g -1 ) which yields a material with almost neutral characteristics (pH p zc: 7,4). At a pH: 4.0 the amount of pb2+ absorbed and the immersion enthalpy values for the activated carbon reached maxim with values of 15.7 mg -1 y 27,6 Jg -1 respectively. it was established that similar behavior occurs for the two properties, absorption and immersion enthalpy, as a function of pH. in addition, a second order function that relates the adsorption constant and immersion enthalpy, and the adsorption constant and ph of the solution are presented

Standard Test Method for Calculation of Stagnation Enthalpy from Heat Transfer Theory and Experimental Measurements of Stagnation-Point Heat Transfer and Pressure

CERN Document Server

American Society for Testing and Materials. Philadelphia

2005-01-01

1.1 This test method covers the calculation from heat transfer theory of the stagnation enthalpy from experimental measurements of the stagnation-point heat transfer and stagnation pressure. 1.2 Advantages 1.2.1 A value of stagnation enthalpy can be obtained at the location in the stream where the model is tested. This value gives a consistent set of data, along with heat transfer and stagnation pressure, for ablation computations. 1.2.2 This computation of stagnation enthalpy does not require the measurement of any arc heater parameters. 1.3 Limitations and ConsiderationsThere are many factors that may contribute to an error using this type of approach to calculate stagnation enthalpy, including: 1.3.1 TurbulenceThe turbulence generated by adding energy to the stream may cause deviation from the laminar equilibrium heat transfer theory. 1.3.2 Equilibrium, Nonequilibrium, or Frozen State of GasThe reaction rates and expansions may be such that the gas is far from thermodynamic equilibrium. 1.3.3 Noncat...

Prediction of the enthalpies of vaporization for room-temperature ionic liquids: Correlations and a substitution-based additive scheme

International Nuclear Information System (INIS)

Kabo, Gennady J.; Paulechka, Yauheni U.; Zaitsau, Dzmitry H.; Firaha, Alena S.

2015-01-01

Highlights: • The available literature data on Δ l g H for ionic liquids were analyzed. • Correlation equations for Δ l g H were derived using symbolic regression. • A substitution-based incremental scheme for Δ l g H was developed. • The proposed scheme has an advantage over the existing predictive procedures. - Abstract: The literature data on the enthalpies of vaporization for aprotic ionic liquids (ILs) published by the end of May 2014 were analyzed and the most reliable Δ l g H m values were derived for 68 ILs. The selected enthalpies of vaporization were correlated with density and surface tension using symbolic regression and a number of effective correlation equations were proposed. The substitution-based incremental scheme for prediction of the enthalpies of vaporization of imidazolium, pyridinium and pyrrolidinium ILs was developed. The standard error of the regression for the developed scheme is significantly lower than that for the atom-based group-contribution schemes proposed earlier

High surface area carbon for bifunctional air electrodes applied in zinc-air batteries

Energy Technology Data Exchange (ETDEWEB)

Arai, H [on leave from NTT Laboratories (Japan); Mueller, S; Haas, O [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1999-08-01

Bifunctional air electrodes with high surface area carbon substrates showed low reduction overpotential, thus are promising for enhancing the energy efficiency and power capability of zinc-air batteries. The improved performance is attributed to lower overpotential due to diffusion of the reaction intermediate, namely the peroxide ion. (author) 1 fig., 2 refs.

High-throughput liquid-absorption air-sampling apparatus and methods

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-07-11

A portable high-throughput liquid-absorption air sampler [PHTLAAS] has an asymmetric air inlet through which air is drawn upward by a small and light-weight centrifugal fan driven by a direct current motor that can be powered by a battery. The air inlet is so configured as to impart both rotational and downward components of motion to the sampled air near said inlet. The PHTLAAS comprises a glass tube of relatively small size through which air passes at a high rate in a swirling, highly turbulent motion, which facilitates rapid transfer of vapors and particulates to a liquid film covering the inner walls of the tube. The pressure drop through the glass tube is < 10 cm of water, usually < 5 cm of water. The sampler's collection efficiency is usually > 20% for vapors or airborne particulates in the 2--3 microns range and > 50% for particles larger than 4 microns. In conjunction with various analyzers, the PHTLAAS can serve to monitor a variety of hazardous or illicit airborne substances, such as lead-containing particulates, tritiated water vapor, biological aerosols, or traces of concealed drugs or explosives.

Prediction of the vapor pressure and vaporization enthalpy of 1-n-alkyl-3-methylimidazolium-bis-(trifluoromethanesulfonyl) amide ionic liquids.

Science.gov (United States)

Diedenhofen, Michael; Klamt, Andreas; Marsh, Kenneth; Schäfer, Ansgar

2007-09-07

The vapor pressures and vaporization enthalpies of a series of 1-n-alkyl-3-methylimidazolium-bis-(trifluoromethanesulfonyl) amide ionic liquids have been predicted with two different approaches using the COSMO-RS method and quantum chemical gas phase calculations. While the calculated enthalpies are in good agreement with the experimental data, COSMO-RS seems to underestimate the vapor pressures by roughly 0.5-4 log units dependent on the IL and approach used.

New calculation method for thermodynamic properties of humid air in humid air turbine cycle – The general model and solutions for saturated humid air

International Nuclear Information System (INIS)

Wang, Zidong; Chen, Hanping; Weng, Shilie

2013-01-01

The article proposes a new calculation method for thermodynamic properties (i.e. specific enthalpy, specific entropy and specific volume) of humid air in humid air turbine cycle. The research pressure range is from 0.1 MPa to 5 MPa. The fundamental behaviors of dry air and water vapor in saturated humid air are explored in depth. The new model proposes and verifies the relationship between total gas mixture pressure and gas component pressures. This provides a good explanation of the fundamental behaviors of gas components in gas mixture from a new perspective. Another discovery is that the water vapor component pressure of saturated humid air equals P S , always smaller than its partial pressure (f·P S ) which was believed in the past researches. In the new model, “Local Gas Constant” describes the interaction between similar molecules. “Improvement Factor” is proposed for the first time by this article, and it quantitatively describes the magnitude of interaction between dissimilar molecules. They are combined to fully describe the real thermodynamic properties of humid air. The average error of Revised Dalton's Method is within 0.1% compared to experimentally-based data. - Highlights: • Our new model is suitable to calculate thermodynamic properties of humid air in HAT cycle. • Fundamental behaviors of dry air and water vapor in saturated humid air are explored in depth. • Local-Gas-Constant describes existing alone component and Improvement Factor describes interaction between different components. • The new model proposes and verifies the relationship between total gas mixture pressure and component pressures. • It solves saturated humid air thoroughly and deviates from experimental data less than 0.1%

Air pollution forecast in cities by an air pollution index highly correlated with meteorological variables

International Nuclear Information System (INIS)

Cogliani, E.

2001-01-01

There are many different air pollution indexes which represent the global urban air pollution situation. The daily index studied here is also highly correlated with meteorological variables and this index is capable of identifying those variables that significantly affect the air pollution. The index is connected with attention levels of NO 2 , CO and O 3 concentrations. The attention levels are fixed by a law proposed by the Italian Ministries of Health and Environment. The relation of that index with some meteorological variables is analysed by the linear multiple partial correlation statistical method. Florence, Milan and Vicence were selected to show the correlation among the air pollution index and the daily thermic excursion, the previous day's air pollution index and the wind speed. During the January-March period the correlation coefficient reaches 0.85 at Milan. The deterministic methods of forecasting air pollution concentrations show very high evaluation errors and are applied on limited areas around the observation stations, as opposed to the whole urban areas. The global air pollution, instead of the concentrations at specific observation stations, allows the evaluation of the level of the sanitary risk regarding the whole urban population. (Author)

Impact of individually controlled facially applied air movement on perceived air quality at high humidity

Energy Technology Data Exchange (ETDEWEB)

Skwarczynski, M.A. [Faculty of Environmental Engineering, Institute of Environmental Protection Engineering, Department of Indoor Environment Engineering, Lublin University of Technology, Lublin (Poland); International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, Copenhagen (Denmark); Melikov, A.K.; Lyubenova, V. [International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, Copenhagen (Denmark); Kaczmarczyk, J. [Faculty of Energy and Environmental Engineering, Department of Heating, Ventilation and Dust Removal Technology, Silesian University of Technology, Gliwice (Poland)

2010-10-15

The effect of facially applied air movement on perceived air quality (PAQ) at high humidity was studied. Thirty subjects (21 males and 9 females) participated in three, 3-h experiments performed in a climate chamber. The experimental conditions covered three combinations of relative humidity and local air velocity under a constant air temperature of 26 C, namely: 70% relative humidity without air movement, 30% relative humidity without air movement and 70% relative humidity with air movement under isothermal conditions. Personalized ventilation was used to supply room air from the front toward the upper part of the body (upper chest, head). The subjects could control the flow rate (velocity) of the supplied air in the vicinity of their bodies. The results indicate an airflow with elevated velocity applied to the face significantly improves the acceptability of the air quality at the room air temperature of 26 C and relative humidity of 70%. (author)

Determination of the vacancy formation enthalpy in chromium by positron annihilation

International Nuclear Information System (INIS)

Loper, G.D.; Smedskjaer, L.C.; Chason, M.K.; Siegel, R.W.

1985-01-01

Doppler broadening of the positron annihilation lineshape in 99.99 at. % pure chromium was measured over the temperature range 296 to 2049 0 K. The chromium sample was encapsulated in sapphire owing to its high vapor pressure near melting. Saturation-like behavior of the lineshape was observed near the melting temperature (2130 0 K). A two-state trapping model fit to the data yielded a vacancy formation enthalpy of 2.0 +- 0.2 eV. This result is discussed in relation to extant empirical relations for vacancy migration and self-diffusion in metals and to data from previous self-diffusion and annealing experiments in chromium. It is concluded that the observed vacancy ensemble is unlikely to be responsible for the measured self-diffusion behavior. The implications of the present results in terms of our understanding of mechanisms for self-diffusion in chromium and other refractory bcc metals are discussed

Standard molar enthalpies of formation of hydroxy-, chlor-, and bromapatite

Energy Technology Data Exchange (ETDEWEB)

Cruz, Fernando J.A.L. [Centro de Quimica Estrutural, Complexo Interdisciplinar, Instituto Superior Tecnico 1049-001 Lisbon (Portugal); Minas da Piedade, Manuel E. [Departamento de Quimica e Bioquimica, Faculdade de Ciencias, Universidade de Lisboa, 1749-016 Lisbon (Portugal); Calado, Jorge C.G. [Centro de Quimica Estrutural, Complexo Interdisciplinar, Instituto Superior Tecnico 1049-001 Lisbon (Portugal)]. E-mail: jcalado@ist.utl.pt

2005-10-15

The standard (p{sup 0} =0.1MPa) molar enthalpies of formation in the crystalline state of hydroxyapatite, chlorapatite and a preliminary value for bromapatite, at T=298.15K, were determined by reaction-solution calorimetry as: {delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2},cr]=-(13399+/-11)kJ.mol{sup -1},{delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}Cl{sub 2},cr]=-(13231+/-82)kJ.mol{sup -1},and{delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}Br{sub 2},cr]=-(13063+/-81)kJ.mol{sup -1}. A critical assessment of these results and of previously published data is made. Finally, the standard molar enthalpy of formation of iodapatite is estimated as {delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}I{sub 2},cr]=-12949kJ.mol{sup -1}, from a linear correlation of {delta}{sub f}H{sub m}{sup 0} [Ca{sub 10}(PO{sub 4}){sub 6}X{sub 2},cr] (X=OH, F, Cl, Br) against the corresponding {delta}{sub f}H{sub m}{sup 0} [CaX{sub 2},cr].

Determination of the enthalpy of fusion and thermal diffusivity for ternary Cu_6_0_−_xSn_xSb_4_0 alloys

International Nuclear Information System (INIS)

Zhai, W.; Zhou, K.; Hu, L.; Wei, B.

2016-01-01

Highlights: • The increasing Sn content reduces the liquidus temperature. • High Sn content results in lower enthalpy of fusion by polynomial functions. • The thermal diffusivity drops from the solid toward the semi-solid state. • Undercoolability of alloys with primary Cu_2Sb phase is stronger than others. - Abstract: The liquidus and solidus temperatures, enthalpy of fusion, and the temperature dependence of thermal diffusivity for ternary Cu_6_0_−_xSn_xSb_4_0 alloys were systematically measured by DSC and laser flash methods. It is found that both the liquidus temperature and the enthalpy of fusion decrease with the rise of Sn content, and their relationships with alloy composition were established by polynomial functions. The thermal diffusivity usually drops from the solid toward the semi-solid state. The undercoolability of those liquid Cu_6_0_−_xSn_xSb_4_0 alloys with primary Cu_2Sb solid phase is stronger than the others with primary β(SnSb) intermetallic compound, and the increase of cooling rate facilitates further undercooling. Microstructural observation indicates that both of the primary Cu_2Sb and β(SnSb) intermetallic compounds in ternary Cu_6_0_−_xSn_xSb_4_0 alloys grow in faceted mode, and develop into coarse flakes and polygonal blocks.

Influences of the Air in Metal Powder High Velocity Compaction

Directory of Open Access Journals (Sweden)

Liu Jun

2017-01-01

Full Text Available During the process of metal powder high velocity impact compaction, the air is compressed sharply and portion remains in the compacts. In order to study the Influences, a discrete density volleyball accumulation model for aluminium powder was established with the use of ABAQUS. Study found that the powder porosity air obstruct the pressing process because remaining air reduced strength and density of the compacts in the current high-speed pressing (V≤100m/s. When speed further increased (V≥100m/s, the temperature of the air increased sharply, and was even much higher than the melting point of the material. When aluminium powder was compressed at a speed of 200m/s, temperatures of air could reach 2033 K, far higher than the melting point of 877 K. Increased density of powders was a result of local softening and even melt adhesive while air between particles with high temperature and pressure flowed past.

Enthalpies of dilution of aqueous Li{sub 2}B{sub 4}O{sub 7} solutions at 298.15K and application of ion-interaction model

Energy Technology Data Exchange (ETDEWEB)

Yin Guoyin [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Yao Yan [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008 (China) and Graduate School of Chinese Academy of Sciences, Beijing 100039 (China)]. E-mail: yaoy@isl.ac.cn; Jiao Baojuan [Department of Chemistry, Northwest University, Xi' an 710069 (China); Chen Sanping [Department of Chemistry, Northwest University, Xi' an 710069 (China); Gao Shengli [Department of Chemistry, Northwest University, Xi' an 710069 (China)

2005-09-15

The enthalpies of dilution have been measured for aqueous Li{sub 2}B{sub 4}O{sub 7} solutions from 0.0212 to 2.1530molkg{sup -1} at 298.15K. The relative apparent molar enthalpies, L{sub {phi}}, and relative partial molar enthalpies of the solvent and solute, L-bar{sub 1} and L-bar{sub 2} were calculated. The thermodynamic properties of the complex aqueous solutions were represented with a modified Pitzer ion-interaction model.

Air-stable magnesium nanocomposites provide rapid and high-capacity hydrogen storage without using heavy-metal catalysts

Science.gov (United States)

Jeon, Ki-Joon; Moon, Hoi Ri; Ruminski, Anne M.; Jiang, Bin; Kisielowski, Christian; Bardhan, Rizia; Urban, Jeffrey J.

2011-04-01

Hydrogen is a promising alternative energy carrier that can potentially facilitate the transition from fossil fuels to sources of clean energy because of its prominent advantages such as high energy density (142 MJ kg-1 ref. 1), great variety of potential sources (for example water, biomass, organic matter), light weight, and low environmental impact (water is the sole combustion product). However, there remains a challenge to produce a material capable of simultaneously optimizing two conflicting criteria—absorbing hydrogen strongly enough to form a stable thermodynamic state, but weakly enough to release it on-demand with a small temperature rise. Many materials under development, including metal-organic frameworks, nanoporous polymers, and other carbon-based materials, physisorb only a small amount of hydrogen (typically 1-2 wt%) at room temperature. Metal hydrides were traditionally thought to be unsuitable materials because of their high bond formation enthalpies (for example MgH2 has a ΔHf˜75 kJ mol-1), thus requiring unacceptably high release temperatures resulting in low energy efficiency. However, recent theoretical calculations and metal-catalysed thin-film studies have shown that microstructuring of these materials can enhance the kinetics by decreasing diffusion path lengths for hydrogen and decreasing the required thickness of the poorly permeable hydride layer that forms during absorption. Here, we report the synthesis of an air-stable composite material that consists of metallic Mg nanocrystals (NCs) in a gas-barrier polymer matrix that enables both the storage of a high density of hydrogen (up to 6 wt% of Mg, 4 wt% for the composite) and rapid kinetics (loading in <30 min at 200 °C). Moreover, nanostructuring of the Mg provides rapid storage kinetics without using expensive heavy-metal catalysts.

The gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide from combustion calorimetry, vapor pressure measurements, and ab initio calculations.

Science.gov (United States)

Emel'yanenko, Vladimir N; Verevkin, Sergey P; Heintz, Andreas

2007-04-04

Ionic liquids are attracting growing interest as alternatives to conventional molecular solvents. Experimental values of vapor pressure, enthalpy of vaporization, and enthalpy of formation of ionic liquids are the key thermodynamic quantities, which are required for the validation and development of the molecular modeling and ab initio methods toward this new class of solvents. In this work, the molar enthalpy of formation of the liquid 1-butyl-3-methylimidazolium dicyanamide, 206.2 +/- 2.5 kJ.mol-1, was measured by means of combustion calorimetry. The molar enthalpy of vaporization of 1-butyl-3-methylimidazolium dicyanamide, 157.2 +/- 1.1 kJ.mol-1, was obtained from the temperature dependence of the vapor pressure measured using the transpiration method. The latter method has been checked with measurements of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, where data are available from the effusion technique. The first experimental determination of the gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide, 363.4 +/- 2.7 kJ.mol-1, from thermochemical measurements (combustion and transpiration) is presented. Ab initio calculations of the enthalpy of formation in the gaseous phase have been performed for 1-butyl-3-methylimidazolium dicyanamide using the G3MP2 theory. Excellent agreement with experimental results has been observed. The method developed opens a new way to obtain thermodynamic properties of ionic liquids which have not been available so far.

Making sense of enthalpy of vaporization trends for ionic liquids: new experimental and simulation data show a simple linear relationship and help reconcile previous data.

Science.gov (United States)

Verevkin, Sergey P; Zaitsau, Dzmitry H; Emel'yanenko, Vladimir N; Yermalayeu, Andrei V; Schick, Christoph; Liu, Hongjun; Maginn, Edward J; Bulut, Safak; Krossing, Ingo; Kalb, Roland

2013-05-30

Vaporization enthalpy of an ionic liquid (IL) is a key physical property for applications of ILs as thermofluids and also is useful in developing liquid state theories and validating intermolecular potential functions used in molecular modeling of these liquids. Compilation of the data for a homologous series of 1-alkyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide ([C(n)mim][NTf2]) ILs has revealed an embarrassing disarray of literature results. New experimental data, based on the concurring results from quartz crystal microbalance, thermogravimetric analyses, and molecular dynamics simulation have revealed a clear linear dependence of IL vaporization enthalpies on the chain length of the alkyl group on the cation. Ambiguity of the procedure for extrapolation of vaporization enthalpies to the reference temperature 298 K was found to be a major source of the discrepancies among previous data sets. Two simple methods for temperature adjustment of vaporization enthalpies have been suggested. Resulting vaporization enthalpies obey group additivity, although the values of the additivity parameters for ILs are different from those for molecular compounds.

Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C211H17NO(s)

Institute of Scientific and Technical Information of China (English)

Di You-Ying; Wang Da-Qi; Shi Quan; Tan Zhi-Cheng

2008-01-01

This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO(s) have been mea- sured by a precision automated adiabatic calorimeter over the temperature range from T=78 K to T=400 K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342- 364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO(s) relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol preci- sion oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.

Vapor pressures and standard molar enthalpies, entropies and Gibbs energies of sublimation of two hexachloro herbicides using a TG unit

International Nuclear Information System (INIS)

Vecchio, Stefano

2010-01-01

The vapor pressures above the solid hexachlorobenzene (HCB) and above both the solid and liquid 1,2,3,4,5,6-hexachlorocyclohexane (lindane) were determined in the ranges 332-450 K and 347-429 K, respectively, by measuring the mass loss rates recorded by thermogravimetry under both isothermal and nonisothermal conditions. The results obtained were compared with those taken from literature. From the temperature dependence of vapor pressure derived by the experimental thermogravimetry data the molar enthalpies of sublimation Δ cr g H m o ( ) were selected for HCB and lindane as well as the molar enthalpy of vaporization Δ l g H m o ( ) for lindane only, at the middle of the respective temperature intervals. The melting temperatures and the molar enthalpies of fusion Δ cr l H m o (T fus ) of lindane were measured by differential scanning calorimetry. Finally, the standard molar enthalpies of sublimation Δ cr g H m o (298.15 K) were obtained for both chlorinated compounds at the reference temperature of 298.15 K using the Δ cr g H m o ( ), Δ l g H m o ( ) and Δ cr l H m o (T fus ) values, as well as the heat capacity differences between gas and liquid and the heat capacity differences between gas and solid, Δ l g C p,m o and Δ cr g C p,m o , respectively, both estimated by applying a group additivity procedure. Therefore, the averages of the standard (p o = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation at 298.15 K, have been derived.

Study of the distributions of flow rate and enthalpy in the sub-channels of a bundle geometry of nuclear reactors in one and two-phase flow

International Nuclear Information System (INIS)

Bayoumi, M.A.A.

1976-10-01

A bibliographic study shows that the experimental studies examined, have been developed to understand the phenomenon acting on the mixing between the sub-channels of which geometries are such these of rod bundles used in some nuclear reactors. Experimental devices and tests have been developed to study the influence of the following parameters, operating conditions, pressure, flow rate, power brought to the bundle and inlet temperature on the distribution of flow rates and vapor content among the different sub-channels. By means of non isokinetic sampling, one has determined the enthalpy of the fluid participating to the mixing between the communicating sub-channels and it has been shown that the value of this enthalpy depends strongly on the type of fluid flow and that this enthalpy cannot be either the enthalpy of one of the two sub-channels, nor (always) an average of these two enthalpies. The experimental results have been compared with calculations developed with the code FLICA, concerning the mass velocity distribution, the exchange term of linear momentum, and the variation of the transversal enthalpy with regard to the type of fluid flow. A study of local void ratio measurement, by means of optical probes, has been proposed. The present study has been carried out with a smooth geometry [fr

Sub-Tg enthalpy relaxation in an unstable oxide glass former: insights into the structural heterogeneity

DEFF Research Database (Denmark)

Yue, Yuanzheng; Zhang, Yanfei

Structural heterogeneity plays a crucial role in determining functionality of glasses. In this work we have found that the sub-Tg enthalpy relaxation pattern in a hyperquenched glass is highly sensitive to structural heterogeneity. As a consequence, the former can be used as an effective approach...... to detect and quantify the structural heterogeneity in glass-forming liquids. However, the chemical nature of structural heterogeneity should be revealed by other means such as high resolution microscopic and spectroscopic methods. To study the impact of the structural heterogeneity on the sub-Tg relaxation...... chemical features and degrees of structural heterogeneity in glass-forming liquids. This finding contributes to the microscopic origin of both the primary and secondary relaxation in terms of structural heterogeneity. Finally the results provide insights into the relation between structural heterogeneity...

Stable isotope studies of some low enthalpy geothermal systems in Kenya

Science.gov (United States)

Tole, Mwakio P.

Oxygen and hydrogen isotope compositions of some low enthalpy geothermal systems in Kenya have been determined. Plots on δ 18O versus δD diagrams show that the compositions do not deviate appreciably from local meteoric water values. This would indicate that local meteoric waters are heated at depth and rise to the surface without much interaction with the country rocks. This is interpreted to be the case for the geothermal systems at Majimoto and Narosura, which have salinities of less than 350 ppm TDS and calculated reservoir temperatures of less than 110°C. The geothermal systems at Kapedo and Homa mountain which have high salinities (> 2 000 ppm TDS) and relatively higher calculated reservoir temperatures (> 150° C) are interpreted to have been operating for long periods of time, such that the rocks through which the present day geothermal waters are circulating have attained isotopic equilibrium with local meteoric waters.

High-energy components of 'designer gasoline and designer diesel fuel' I. Heat capacities, enthalpy increments, vapor pressures, critical properties, and derived thermodynamic functions for bicyclopentyl between the T=(10 and 600) K

International Nuclear Information System (INIS)

Chirico, R.D.; Steele, W.V.

2004-01-01

Measurements leading to the calculation of the standard thermodynamic properties for gaseous bicyclopentyl (Chemicals Abstracts registry number [1636-39-1]) are reported. Experimental methods include adiabatic heat-capacity calorimetry, comparative ebulliometry, and differential-scanning calorimetry (d.s.c.). The critical temperature was determined by d.s.c. and the critical pressure and critical density were estimated. Standard molar entropies, standard molar enthalpies, and standard molar Gibbs free energies of formation are reported at selected temperatures between T=(298.15 and 600) K. Formation properties were calculated with a literature value for the enthalpy of combustion in the liquid phase. All results are compared with available literature values

Thermodynamic diagrams for high temperature plasmas of air, air-carbon, carbon-hydrogen mixtures, and argon

CERN Document Server

Kroepelin, H; Hoffmann, K-U

2013-01-01

Thermodynamic Diagrams for High Temperature Plasmas of Air, Air-Carbon, Carbon-Hydrogen Mixtures, and Argon provides information relating to the properties of equilibrium gas plasmas formed from hydrocarbons, from air without argon, from pure argon, and from mixtures of air and carbon at various compositions, temperatures and pressures. The data are presented in graphical rather than tabular form to provide a clearer picture of the plasma processes investigated. This book is composed of four chapters, and begins with the introduction to the characteristics of plasmas, with emphasis on their th

Enthalpy of dilution and volumetric properties of N-glycylglycine in aqueous xylitol solutions at T = 298.15 K

Energy Technology Data Exchange (ETDEWEB)

Liu Min, E-mail: panpanliumin@163.co [College of Chemistry and Chemical Engineering, Liao Cheng University, Liaocheng, Shandong 252059 (China); Wang Lili; Li Guangqian; Dong Lina; Sun Dezhi [College of Chemistry and Chemical Engineering, Liao Cheng University, Liaocheng, Shandong 252059 (China); Zhu Lanying [College of Life Science and Bioengineering, Liao Cheng University, Liaocheng, Shandong 252059 (China); Di Youying [College of Chemistry and Chemical Engineering, Liao Cheng University, Liaocheng, Shandong 252059 (China)

2011-06-15

Highlights: Enthalpies of dilution of N-glycylglycine in aqueous xylitol solutions were determined at 298.15 K. The homogeneous enthalpic interaction coefficients were calculated. Apparent molar volumes of the ternary systems were calculated from the data of densities. Limiting partial molar volumes and limiting partial molar volumes of transfer were deduced. - Abstract: The enthalpy of dilution of N-glycylglycine ({Delta}{sub dil}H{sub m}) in aqueous xylitol solutions has been determined by means of flow-mix isothermal microcalorimetry at the temperature of 298.15 K. The homogeneous enthalpic interaction coefficients (h{sub 2}, h{sub 3}, and h{sub 4}) which characterize the interactions of examined N-glycylglycine in aqueous xylitol solutions have been calculated according to the excess enthalpy concept based on the values of dilution enthalpy. It has been found that the enthalpic pair interaction coefficients (h{sub 2}) in the systems investigated are negative and become less negative as the molality of xylitol increases. Values of the density ({rho}) of the ternary homogeneous systems were also measured with a quartz vibrating-tube densimeter at the temperature of 298.15 K. The values of the apparent molar volume (V{sub {phi}}) of the ternary systems were calculated from the data of density, which have been used to deduce limiting partial molar volumes of N-glycylglycine (V{sub {phi}}{sup o}) and limiting partial molar volumes of transfer ({Delta}{sub trs}V{sub {phi}}{sup o}) from water to aqueous xylitol solutions at different concentrations. The results have been discussed based on solute-solute interactions and solvation effects.

Enthalpy of dilution and volumetric properties of N-glycylglycine in aqueous xylitol solutions at T = 298.15 K

International Nuclear Information System (INIS)

Liu Min; Wang Lili; Li Guangqian; Dong Lina; Sun Dezhi; Zhu Lanying; Di Youying

2011-01-01

Highlights: → Enthalpies of dilution of N-glycylglycine in aqueous xylitol solutions were determined at 298.15 K. → The homogeneous enthalpic interaction coefficients were calculated. → Apparent molar volumes of the ternary systems were calculated from the data of densities. → Limiting partial molar volumes and limiting partial molar volumes of transfer were deduced. - Abstract: The enthalpy of dilution of N-glycylglycine (Δ dil H m ) in aqueous xylitol solutions has been determined by means of flow-mix isothermal microcalorimetry at the temperature of 298.15 K. The homogeneous enthalpic interaction coefficients (h 2 , h 3 , and h 4 ) which characterize the interactions of examined N-glycylglycine in aqueous xylitol solutions have been calculated according to the excess enthalpy concept based on the values of dilution enthalpy. It has been found that the enthalpic pair interaction coefficients (h 2 ) in the systems investigated are negative and become less negative as the molality of xylitol increases. Values of the density (ρ) of the ternary homogeneous systems were also measured with a quartz vibrating-tube densimeter at the temperature of 298.15 K. The values of the apparent molar volume (V φ ) of the ternary systems were calculated from the data of density, which have been used to deduce limiting partial molar volumes of N-glycylglycine (V φ o ) and limiting partial molar volumes of transfer (Δ trs V φ o ) from water to aqueous xylitol solutions at different concentrations. The results have been discussed based on solute-solute interactions and solvation effects.

Low-temperature heat capacity and standard molar enthalpy of formation of 9-fluorenemethanol (C14H12O)

International Nuclear Information System (INIS)

Di, You-Ying; Tan, Zhi-Cheng.; Sun, Xiao-Hong; Wang, Mei-Han; Xu, Fen; Liu, Yuan-Fa; Sun, Li-Xian; Zhang, Hong-Tao

2004-01-01

Low-temperature heat capacities of the 9-fluorenemethanol (C 14 H 12 O) have been precisely measured with a small sample automatic adiabatic calorimeter over the temperature range between T=78 K and T=390 K. The solid-liquid phase transition of the compound has been observed to be T fus =(376.567±0.012) K from the heat-capacity measurements. The molar enthalpy and entropy of the melting of the substance were determined to be Δ fus H m =(26.273±0.013) kJ · mol -1 and Δ fus S m =(69.770±0.035) J · K -1 · mol -1 . The experimental values of molar heat capacities in solid and liquid regions have been fitted to two polynomial equations by the least squares method. The constant-volume energy and standard molar enthalpy of combustion of the compound have been determined, Δ c U(C 14 H 12 O, s)=-(7125.56 ± 4.62) kJ · mol -1 and Δ c H m compfn (C 14 H 12 O, s)=-(7131.76 ± 4.62) kJ · mol -1 , by means of a homemade precision oxygen-bomb combustion calorimeter at T=(298.15±0.001) K. The standard molar enthalpy of formation of the compound has been derived, Δ f H m compfn (C 14 H 12 O,s)=-(92.36 ± 0.97) kJ · mol -1 , from the standard molar enthalpy of combustion of the compound in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle

Prediction of flame formation in highly preheated air combustion

International Nuclear Information System (INIS)

Yang, Jang Sik; Choi, Gyung Min; Kim, Duck Jool; Katsuki, Masashi

2008-01-01

Fundamental information about the ignition position and shape of a flame in highly preheated air combustion was obtained, and the suitability of the suggested reduced kinetic mechanism that reflects the characteristics of the highly preheated air combustion was demonstrated. Flame lift height and flame length with variations of premixed air temperature and oxygen concentration were measured by CH chemiluminescence intensity, and were computed with a reduced kinetic mechanism. Flame attached near a fuel nozzle started to lift when preheated air temperature became close to auto-ignition temperature and/or oxygen concentration reduced. The flame lift height increased but the flame length decreased with decreasing preheated air temperature and flame length reversed after a minimum value. Calculated results showed good agreement with those of experiment within tolerable error. Flame shape shifted from diffusion flame shape to partial premixed flame shape with increasing lift height and this tendency was also observed in the computation results

Prediction of flame formation in highly preheated air combustion

Energy Technology Data Exchange (ETDEWEB)

Yang, Jang Sik; Choi, Gyung Min; Kim, Duck Jool [Pusan National University, Busan (Korea, Republic of); Katsuki, Masashi [Osaka University, Osaka (Japan)

2008-11-15

Fundamental information about the ignition position and shape of a flame in highly preheated air combustion was obtained, and the suitability of the suggested reduced kinetic mechanism that reflects the characteristics of the highly preheated air combustion was demonstrated. Flame lift height and flame length with variations of premixed air temperature and oxygen concentration were measured by CH chemiluminescence intensity, and were computed with a reduced kinetic mechanism. Flame attached near a fuel nozzle started to lift when preheated air temperature became close to auto-ignition temperature and/or oxygen concentration reduced. The flame lift height increased but the flame length decreased with decreasing preheated air temperature and flame length reversed after a minimum value. Calculated results showed good agreement with those of experiment within tolerable error. Flame shape shifted from diffusion flame shape to partial premixed flame shape with increasing lift height and this tendency was also observed in the computation results

Thermodynamic and transport properties of air and its products of combustion with ASTMA-A-1 fuel and natural gas at 20, 30, and 40 atmospheres

Science.gov (United States)

Poferl, D. J.; Svehla, R. A.

1973-01-01

The isentropic exponent, molecular weight, viscosity, specific heat at constant pressure, thermal conductivity, Prandtl number, and enthalpy were calculated for air, the combustion products of ASTM-A-1 jet fuel and air, and the combustion products of natural gas and air. The properties were calculated over a temperature range from 300 to 2800 K in 100 K increments and for pressures of 20, 30 and 40 atmospheres. The data for natural gas and ASTM-A-1 were calculated for fuel-air ratios from zero to stoichiometric in 0.01 increments.

A compilation of correlation parameters for predicting the enthalpy and thermal conductivity of solid foods within the temperature range of -40 C to +40 C

Energy Technology Data Exchange (ETDEWEB)

Amos, N.D. [Comvita New Zealand Limited, Private Bag 1, Te Puke 3153 (New Zealand); Willix, J.; North, M.F. [AgResearch Limited, MIRINZ Centre, Ruakura Campus, East Street, Private Bag 3123, Hamilton (New Zealand); Chadderton, T. [Crop and Food Research Ltd, PO Box 5114, Nelson (New Zealand)

2008-11-15

This paper presents thermal conductivity data for 40 foods, enthalpy data for 58 foods and density data for nine foods, along with the compositions of the foods. Measurements cover a range of solid food types (including meats, fats, offal, fish, dairy products and horticultural products). Some measurements reported are for foods that have never before been studied, others have been published elsewhere, but are included here for convenience. Thermal conductivity was measured using a guarded hot-plate apparatus, enthalpy using an adiabatic calorimeter and density using a water displacement meter. Thermal conductivity and enthalpy values were measured within the temperature range of -40 C to +40 C. (author) [French] Cette publication presente des donnes sur la conductivite thermique, l'enthalpie et la densite respectivement de 40, 58 et 9 produits alimentaires, ainsi que leurs compositions. Les mesures couvrent une variete de types de produits alimentaires (viande, matieres grasses, abats, poisson, produits laitiers, produits horticoles). Certaines sont rapportees pour des produits qui n 'ant jamais ete etudie auparavant, d'autres ant ete publie ailleurs mais sont aussi inclues pour plus de commodite. La conductivite thermique a ete mesure avec un appareil a plaque electrique protegee, l'enthalpie avec un calorimetre adiabatique et la densite avec un appareil mesurant Ie deplacement d'eau. La conductivite thermique et l'enthalpie ont ete toutes les mesures pour une fourchette de temperatures allant de -40 C a 40 C. (orig.)

Enthalpies of formation of Cd0.917Sr0.083, Cd0.857Sr0.143 and Cd0.667Sr0.333 intermetallic compounds

International Nuclear Information System (INIS)

Agarwal, Renu; Singh, Ziley

2008-01-01

Cadmium is expected to be the solvent for pyrochemical processing of the metallic nuclear fuel. Therefore, thermodynamic properties of cadmium with various fuel and clad elements are of interest. Enthalpies of formation of the intermetallic compounds of Cd-Sr system, Cd 0.917 Sr 0.083 , Cd 0.857 Sr 0.143 and Cd 0.667 Sr 0.333 were determined by precipitation using Calvet calorimeter. Enthalpies of formation of the compounds were found to be -3.05 ± 0.5 kJ mol -1 at 723 K, -14.2 ± 0.7 kJ mol -1 at 843 K and -28.4 ± 0.8 kJ mol -1 at 863 K, respectively. Enthalpies of formation of Cd 0.917 Sr 0.083 and Cd 0.857 Sr 0.143 were also determined by partial enthalpy of formation measurements and the values were found to be -3.9 ± 1.1 kJ mol -1 at 723 K and -13.42 ± 1.2 kJ mol -1 at 843 K, respectively. Miedema model was used to estimate the enthalpies of formation of these compounds and the estimated values were compared with the experimentally determined values

Performance Analysis of Window Type Air Conditioning with Addition of Heat Exchanger Equipment

Directory of Open Access Journals (Sweden)

I Ketut Gede Wirawan

2012-11-01

Full Text Available One manner to be used to increase refregration effect is by flowing hot refrigerant out from condensor, it is then touched with the refrigerant out from evaporator on a heat exchanger of counterflow type. Experiment was done by taking samples of pressure at suction (p1 and discharge (p2 of compressor and box temperature (Tr1, Tr2, Tr3, Tr4. By knowing of pressure at suction (p1, the enthalpy into compressor is known. By assuming the process is isentropic (compressor, isobar (condenser and evaporator, and isenthalpy (expansion valve, the enthalpy into condensor, expansion valve and evaporator were known. In 60 minutes, compression work of air conditioning with heat exchanger is 31,588 kJ/kg, and without heat exchanger is 33,796 kJ/kg. Effect refrigeration average with modification is 155,55 kJ/kg and without modification was 153,40 kJ/kg so that coefficient of performance with modification more than without modification. Air conditioning with modification had initial refrigration rate was 67,193 J/s and 0,043 J/s at the end minute, meanwhile, refrigeration without modification had cooling rate at start 66,538 J/s and 0,935 J/s at the end.

The thermodynamic properties of the upper continental crust: Exergy, Gibbs free energy and enthalpy

International Nuclear Information System (INIS)

Valero, Alicia; Valero, Antonio; Vieillard, Philippe

2012-01-01

This paper shows a comprehensive database of the thermodynamic properties of the most abundant minerals of the upper continental crust. For those substances whose thermodynamic properties are not listed in the literature, their enthalpy and Gibbs free energy are calculated with 11 different estimation methods described in this study, with associated errors of up to 10% with respect to values published in the literature. Thanks to this procedure we have been able to make a first estimation of the enthalpy, Gibbs free energy and exergy of the bulk upper continental crust and of each of the nearly 300 most abundant minerals contained in it. Finally, the chemical exergy of the continental crust is compared to the exergy of the concentrated mineral resources. The numbers obtained indicate the huge chemical exergy wealth of the crust: 6 × 10 6 Gtoe. However, this study shows that approximately only 0.01% of that amount can be effectively used by man.

Partial enthalpies of Bi and Te in Bi-Te melts and of In and Te in In-Te melts

International Nuclear Information System (INIS)

Yassin, Abeer; Amzil, Abdelhamid; Castanet, Robert

2000-01-01

Full text.Calorimetric measurement are reported which allow the enthalpic behaviour of Bi-Te melts to be established. Further work is required, however, to supplement results obtained for In-Te melts. The partial enthalpies of bismuth and tellurium in the Bi-Te melts at 755K and those of indium and tellurium in the In-Te melts at 1010 and 987K were measured at high dilution by direct reaction calorimetry (drop method) with the help of a Tian-Calvet calorimeter. The limiting partial enthalpies of the components were deduced by extrapolation at infinite dilution: Δh f,∞ B i(755K)/KJ.mol -1 = -34.0 and Δh f,∞ Te(755K) /KJ·mol -1 = -24.1 in the Bi-Te melts Δh f,∞ In(1010K) /KJ·mol -1 = -75.9 and Δh f,∞ Te(1010K) /KJ·mol -1 = -47.8 in the In-Te melts Δh f,∞ In(987K) /KJ·mol -1 = -75.2 and Δh f,∞ Te(987K) /KJ·mol -1 = -48.0 in the In-Te melts

Enthalpy of mixing and heat of vaporization of ethyl acetate with benzene and toluene at 298.15 k and 308.15 k

Directory of Open Access Journals (Sweden)

K. L. Shivabasappa

2008-03-01

Full Text Available The present work was carried out in two phases. First, enthalpy of mixing was measured and then the heat of vaporization for the same mixtures was obtained. The data are useful in the design of separation equipments. From the various designs available for the experimental determination of enthalpy of mixing, and heat of vaporization, the apparatus was selected, modified and constructed. The apparatus of enthalpy of mixing was tested with a known system Benzene - i-Butyl Alcohol and the data obtained was in very good agreement with literature values. Experiments were then conducted for mixtures of Ethyl Acetate with Benzene and Toluene. The experimental data was fitted to the standard correlations and the constants were evaluated. Heat of vaporization data were obtained from a static apparatus and tested for accuracy by conducting experiments with a known system Benzene - n-Hexane and the data obtained were found to be in agreement with literature values. Experiments were then conducted to measure heat of vaporization for the mixtures of Ethyl Acetate with Benzene and Toluene. Using experimental data of enthalpy of mixing from the first phase, and heat capacity data, the heat of vaporization were calculated.

NEDO project reports. High performance industrial furnace development project - High temperature air combustion

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-21

For the purpose of reducing energy consumption, a NEDO project 'Developmental research on high efficiency industrial furnaces' was carried out from FY 1993 to FY 1999 by The Japan Industrial Furnaces Manufacturers Association, and the paper outlined the details of the project. Industrial furnaces handled in this R and D can bring 30% reduction of the energy consumption and approximately 50% NOx reduction, and were given the 9th Nikkei global environmental technology prize. In the study of combustion phenomena of high temperature air combustion, the paper arranged characteristics of flame, the base of gaseous fuel flame, the base of liquid fuel flame, the base of solid fuel flame, etc. Concerning high temperature air combustion models for simulation, fluid dynamics and heat transfer models, and reaction and NOx models, etc. As to impacts of high temperature air combustion on performance of industrial furnaces, energy conservation, lowering of pollution, etc. In relation to a guide for the design of high efficiency industrial furnaces, flow charts, conceptual design, evaluation method for heat balance and efficiency using charts, combustion control system, applicability of high efficiency industrial furnaces, etc. (NEDO)

NEDO project reports. High performance industrial furnace development project - High temperature air combustion

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-21

For the purpose of reducing energy consumption, a NEDO project 'Developmental research on high efficiency industrial furnaces' was carried out from FY 1993 to FY 1999 by The Japan Industrial Furnaces Manufacturers Association, and the paper outlined the details of the project. Industrial furnaces handled in this R and D can bring 30% reduction of the energy consumption and approximately 50% NOx reduction, and were given the 9th Nikkei global environmental technology prize. In the study of combustion phenomena of high temperature air combustion, the paper arranged characteristics of flame, the base of gaseous fuel flame, the base of liquid fuel flame, the base of solid fuel flame, etc. Concerning high temperature air combustion models for simulation, fluid dynamics and heat transfer models, and reaction and NOx models, etc. As to impacts of high temperature air combustion on performance of industrial furnaces, energy conservation, lowering of pollution, etc. In relation to a guide for the design of high efficiency industrial furnaces, flow charts, conceptual design, evaluation method for heat balance and efficiency using charts, combustion control system, applicability of high efficiency industrial furnaces, etc. (NEDO)

Pemanfaatan Energi Gas Buang Motor Diesel Stasioner untuk Pemanas Air

OpenAIRE

Rahardjo Tirtoatmodjo

1999-01-01

Exhaust gas from a diesel engine is having a big deal of energy. In a stationer diesel engine, the enthalpy of water will be increased by flowing the water in a spiral pipe which is located in the exhaust manifold of the engine. Using copper pipes in this heat exchanger, it's efficiency is found up to 69,5 %. Abstract in Bahasa Indonesia : Gas buang dari motor diesel masih memiliki sejumlah energi panas yang cukup tinggi. Pada motor diesel stasioner, dengan mengalirkan air pada pipa spiral ya...

Vapour pressures and enthalpies of vaporization of a series of the linear n-alkyl acetates

Czech Academy of Sciences Publication Activity Database

Krasnykh, E. L.; Verevkin, S. P.; Koutek, Bohumír; Doubský, Jan

2006-01-01

Roč. 38, č. 6 (2006), s. 717-723 ISSN 0021-9614 Institutional research plan: CEZ:AV0Z40550506 Keywords : aliphatic acetates * transpiration method * vapour pressure * enthalpy of vaporization Subject RIV: CC - Organic Chemistry Impact factor: 1.842, year: 2006

Liquid-Liquid Equilibrium and Excess Enthalpies in the Binary System 2-Methylpentane + N,N-Dimethylformamide

Czech Academy of Sciences Publication Activity Database

Bendová, Magdalena; Řehák, K.; Matouš, J.; Novák, J. P.

2004-01-01

Roč. 49, č. 5 (2004), s. 1318-1322 ISSN 0021-9568 Institutional research plan: CEZ:AV0Z4072921 Keywords : liquid-liquid equilibrium * excess enthalpies * thermodynamic models Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.368, year: 2004

Using Enthalpy as a Prognostic Variable in Atmospheric Modelling with Variable Composition

Science.gov (United States)

2016-04-14

Sela, personal communication, 2005). These terms are also routinely neglected in models. In models with a limited number of gaseous tracers, such as...so-called energy- exchange term (second term on the left- hand side) in Equation (5). The finite-difference schemes in existing atmospheric models have...equation for the sum of enthalpy and kinetic energy of horizontal motion is solved. This eliminates the energy- exchange term and automatically

The impact of temperature and humidity on perception and emission of indoor air pollutants

DEFF Research Database (Denmark)

Fang, Lei; Clausen, Geo; Fanger, Povl Ole

1996-01-01

Sensory response to air polluted by five building materials under different combinations of temperature and humidity in the ranges 18°C-28°C and 30%-70% was studied in the laboratory. The experiments were designed to study separately the impact of temperature and humidity on the perception of air...... polluted by materials, and on the emission of pollutants from the materials. At all tested pollution levels of the five materials, the air was perceived significantly less acceptable with increasing temperature and humidity, and the impact of temperature and humidity on perception decreased with increasing...... pollution level. A significant linear correlation between acceptability and enthalpy of the air was found to describe the influence of temperature and humidity on perception. The impact of temperature and humidity on sensory emission was less significant than the impact on perception; however, the sensory...

Glass transition memorized by the enthalpy-entropy compensation in the shear thinning of supercooled metallic liquids

Science.gov (United States)

Zhang, Meng; Liu, Lin

2018-06-01

To unravel the true nature of glass transition, broader insights into glass forming have been gained by examining the stress-driven glassy systems, where strong shear thinning, i.e. a reduced viscosity under increasing shear rate, is encountered. It is argued that arbitrarily small stress-driven shear rates would ‘melt’ the glass and erase any memory of its thermal history. In this work, we report a glass transition memorized by the enthalpy-entropy compensation in strongly shear-thinned supercooled metallic liquids, which coincides with the thermal glass transition in both the transition temperature and the activation Gibbs free energy. Our findings provide distinctive insights into both glass forming and shear thinning, and enrich current knowledge on the ubiquitous enthalpy-entropy compensation empirical law in condensed matter physics.

Low enthalpy geothermal for oil sands (LEGO)

Energy Technology Data Exchange (ETDEWEB)

NONE

2008-07-01

Geothermal energy is generated by the slow decay of radioactive materials within the Earth. Geothermal energy resources include the water from hot springs used for heating; the withdrawal of high temperature steam from deep wells; and the use of stable ground or water temperatures near the Earth's surface to heat or cool buildings or in industrial processes. Heat pumps are used to transfer heat or water from the ground into buildings in winter. This paper discussed low enthalpy geothermal options for oil sands processes in order to reduce the use of natural gas and emissions from greenhouse gases (GHGs). The study was also conducted to aid in the development of a portfolio of renewable energy options for the oil and gas sector. The study estimated the costs and benefits of operating a shallow geothermal borehole cluster for meeting a portion of process heat demands for the Nexen's Albian mine. The costs and benefits of operating thermo-chillers integrated with a shallow geothermal borehole cluster for waste heat mitigation were also evaluated. The study showed that geothermal designs can be used to meet a portion of oil sands process heat and cooling demands. Mining operators may reduce carbon emissions and energy costs for process heat demands by installing closed loop borehole heat exchangers. Geothermal heat storage capacity can also be used to increase the efficiency of thermal chillers. It was concluded that pilot plant studies would contribute to a better understanding of the technology. tabs., figs.

Heat pipe heat exchanger for heat recovery in air conditioning

Energy Technology Data Exchange (ETDEWEB)

Abd El-Baky, Mostafa A.; Mohamed, Mousa M. [Mechanical Power Engineering Department, Faculty of Engineering, Minufiya University, Shebin El-Kom (Egypt)

2007-03-15

The heat pipe heat exchangers are used in heat recovery applications to cool the incoming fresh air in air conditioning applications. Two streams of fresh and return air have been connected with heat pipe heat exchanger to investigate the thermal performance and effectiveness of heat recovery system. Ratios of mass flow rate between return and fresh air of 1, 1.5 and 2.3 have been adapted to validate the heat transfer and the temperature change of fresh air. Fresh air inlet temperature of 32-40{sup o}C has been controlled, while the inlet return air temperature is kept constant at about 26{sup o}C. The results showed that the temperature changes of fresh and return air are increased with the increase of inlet temperature of fresh air. The effectiveness and heat transfer for both evaporator and condenser sections are also increased to about 48%, when the inlet fresh air temperature is increased to 40{sup o}C. The effect of mass flow rate ratio on effectiveness is positive for evaporator side and negative for condenser side. The enthalpy ratio between the heat recovery and conventional air mixing is increased to about 85% with increasing fresh air inlet temperature. The optimum effectiveness of heat pipe heat exchanger is estimated and compared with the present experimental data. The results showed that the effectiveness is close to the optimum effectiveness at fresh air inlet temperature near the fluid operating temperature of heat pipes. (author)

Enthalpy model for heating, melting, and vaporization in laser ablation

Directory of Open Access Journals (Sweden)

Vasilios Alexiades

2010-09-01

Full Text Available Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu target in a helium (He background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model that connects the thermodynamics and underlying kinetics of this challenging phase change problem in a self-consistent way.

The relation between relaxed enthalpy and volume during physical aging of amorphous polymers and selenium

Czech Academy of Sciences Publication Activity Database

Slobodian, P.; Říha, Pavel; Rychwalski, R. W.; Emri, I.; Sáha, P.; Kubát, J.

2006-01-01

Roč. 42, č. 10 (2006), s. 2824-2837 ISSN 0014-3057 R&D Projects: GA AV ČR IAA2060401 Institutional research plan: CEZ:AV0Z20600510 Keywords : Enthalpy relaxation * Polymer aging Subject RIV: BJ - Thermodynamics Impact factor: 2.113, year: 2006

Applicability of the theory of thermodynamic similarity to predict the enthalpies of vaporization of aliphatic aldehydes

Science.gov (United States)

Esina, Z. N.; Korchuganova, M. R.

2015-06-01

The theory of thermodynamic similarity is used to predict the enthalpies of vaporization of aliphatic aldehydes. The predicted data allow us to calculate the phase diagrams of liquid-vapor equilibrium in a binary water-aliphatic aldehyde system.

Security of bottle to fill in a high pressure air

Science.gov (United States)

Todic, M.; Latinovic, T.; Golubovic-Bugarski, V.; Majstorovic, A.

2018-01-01

Charging the bottle of high pressure air isolation devices is performed by a high-pressure compressor. The charging time is in function of the compressor capacity and the intensity of the nominal pressure of the air in the bottle. However, in accident situations this time is long and therefore high-pressure accumulators are used where the filling time of the bottle of isolation apparatus has been drastically reduced. Due to the short filling time of the bottle through the air flow, there is a thermodynamic load of bottle material that could endanger the safety of users and other participants in the area. It is therefore necessary to determine the critical parameters of the rapid charge and their intensity.

A Mixed Enthalpy-Temperature Finite Element Method For Generalized Phase-Change Problems

DEFF Research Database (Denmark)

krabbenhøft, Kristian; Damkilde, Lars

2003-01-01

In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground ...... freezing and solar energy storage. The phase-change problem is characterized by an abrupt change in enthalpy per unit temperature in a narrow temperature range around the freezing point....

A Mixed Enthalpy-Temperature Finite Element Method For Generalized Phase-Change Problems

DEFF Research Database (Denmark)

krabbenhøft, Kristian; Damkilde, Lars

2003-01-01

In a large number of problems of engineering interest the transition of the material from one phase to another is of vital importance in describing the overall physical behaviour. Common applications include metal casting, freezing and thawing of foodstuffs and other biological materials, ground...... freezing and solar energy storage. The phase-change problem is characterized by an abrupt change in enthalpy per unit temperature in a narrow temperature range around the freezing point....

Group additivity values for enthalpies of formation (298 K), entropies (298 K), and molar heat capacities (300 K < T < 1500 K) of gaseous fluorocarbons

International Nuclear Information System (INIS)

Van Otterloo, Maren K.; Girshick, Steven L.; Roberts, Jeffrey T.

2007-01-01

A group additivity method was developed to estimate standard enthalpies of formation and standard entropies at 298 K of linear radical and closed-shell, gaseous fluorocarbon neutrals containing four or more carbon atoms. The method can also be used to estimate constant pressure molar heat capacities of the same compounds over the temperature range 300 K to 1500 K. Seventeen groups and seven fluorine-fluorine interaction terms were defined from 12 fluorocarbon molecules. Interaction term values from Yamada and Bozzelli [T. Yamada, J.W. Bozzelli, J. Phys. Chem. A 103 (1999) 7373-7379] were utilized. The enthalpy of formation group values were derived from G3MP2 calculations by Bauschlicher and Ricca [C.W. Bauschlicher, A. Ricca, J. Phys. Chem. A 104 (2000) 4581-4585]. Standard entropy and molar heat capacity group values were estimated from ab initio geometry optimization and frequency calculations at the Hartree-Fock level using the 6-31G(d) basis set. Enthalpies of formation for larger fluorocarbons estimated from the group additivity method compare well to enthalpies of formation found in the literature

Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of Ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals

Directory of Open Access Journals (Sweden)

Rudolf Naef

2017-06-01

Full Text Available The calculation of the standard enthalpies of vaporization, sublimation and solvation of organic molecules is presented using a common computer algorithm on the basis of a group-additivity method. The same algorithm is also shown to enable the calculation of their entropy of fusion as well as the total phase-change entropy of liquid crystals. The present method is based on the complete breakdown of the molecules into their constituting atoms and their immediate neighbourhood; the respective calculations of the contribution of the atomic groups by means of the Gauss-Seidel fitting method is based on experimental data collected from literature. The feasibility of the calculations for each of the mentioned descriptors was verified by means of a 10-fold cross-validation procedure proving the good to high quality of the predicted values for the three mentioned enthalpies and for the entropy of fusion, whereas the predictive quality for the total phase-change entropy of liquid crystals was poor. The goodness of fit (Q2 and the standard deviation (σ of the cross-validation calculations for the five descriptors was as follows: 0.9641 and 4.56 kJ/mol (N = 3386 test molecules for the enthalpy of vaporization, 0.8657 and 11.39 kJ/mol (N = 1791 for the enthalpy of sublimation, 0.9546 and 4.34 kJ/mol (N = 373 for the enthalpy of solvation, 0.8727 and 17.93 J/mol/K (N = 2637 for the entropy of fusion and 0.5804 and 32.79 J/mol/K (N = 2643 for the total phase-change entropy of liquid crystals. The large discrepancy between the results of the two closely related entropies is discussed in detail. Molecules for which both the standard enthalpies of vaporization and sublimation were calculable, enabled the estimation of their standard enthalpy of fusion by simple subtraction of the former from the latter enthalpy. For 990 of them the experimental enthalpy-of-fusion values are also known, allowing their comparison with predictions, yielding a correlation

Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of Ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals.

Science.gov (United States)

Naef, Rudolf; Acree, William E

2017-06-25

The calculation of the standard enthalpies of vaporization, sublimation and solvation of organic molecules is presented using a common computer algorithm on the basis of a group-additivity method. The same algorithm is also shown to enable the calculation of their entropy of fusion as well as the total phase-change entropy of liquid crystals. The present method is based on the complete breakdown of the molecules into their constituting atoms and their immediate neighbourhood; the respective calculations of the contribution of the atomic groups by means of the Gauss-Seidel fitting method is based on experimental data collected from literature. The feasibility of the calculations for each of the mentioned descriptors was verified by means of a 10-fold cross-validation procedure proving the good to high quality of the predicted values for the three mentioned enthalpies and for the entropy of fusion, whereas the predictive quality for the total phase-change entropy of liquid crystals was poor. The goodness of fit ( Q ²) and the standard deviation (σ) of the cross-validation calculations for the five descriptors was as follows: 0.9641 and 4.56 kJ/mol ( N = 3386 test molecules) for the enthalpy of vaporization, 0.8657 and 11.39 kJ/mol ( N = 1791) for the enthalpy of sublimation, 0.9546 and 4.34 kJ/mol ( N = 373) for the enthalpy of solvation, 0.8727 and 17.93 J/mol/K ( N = 2637) for the entropy of fusion and 0.5804 and 32.79 J/mol/K ( N = 2643) for the total phase-change entropy of liquid crystals. The large discrepancy between the results of the two closely related entropies is discussed in detail. Molecules for which both the standard enthalpies of vaporization and sublimation were calculable, enabled the estimation of their standard enthalpy of fusion by simple subtraction of the former from the latter enthalpy. For 990 of them the experimental enthalpy-of-fusion values are also known, allowing their comparison with predictions, yielding a correlation coefficient R

Experimental measurement of enthalpy increments of Th0.25Ce0.75O2

International Nuclear Information System (INIS)

Babu, R.; Balakrishnan, S.; Ananthasivan, K.; Nagarajan, K.

2013-01-01

Thorium has been suggested as an alternative fertile material for a nuclear fuel cycle, and an inert matrix for burning plutonium and for waste disposal. The third stage of India's nuclear power programme envisages utilization of thorium and plutonium as a fuel in Advanced Heavy Water Reactor (AHWR) and Accelerator Driven Sub-critical Systems (ADSS). Solid solutions of ThO 2 -PuO 2 are of importance because of coexistence of Th with Pu during the breeding cycle. CeO 2 is used as a PuO 2 analog due to similar ionic radii of cations and similar physico-chemical properties of the oxides. ThO 2 forms a homogeneous solid solution with the cubic fluorite structure when doped with Ce in the entire compositional range. In the development of mixed oxide nuclear fuels, knowledge of thermodynamic properties of thorium oxide and its mixtures has become extremely importance for understanding the fuel behavior during irradiation and for predicting the performance of the fuel under accidental conditions. Thermodynamic functions such as the enthalpy increment and heat capacity of the theria-ceria solid solution have not been measured experimentally. Hence, the enthalpy increments of thoria-ceria solid solutions, Th 0.25 Ce 0.75 O 2 by inverse drop calorimetry in the temperature range 523-1723 K have been measured. The measured enthalpy increments were fitted in to polynomial functions by using the least squares method and the other thermodynamic functions such as heat capacity, entropy and Gibbs energy functions were computed in the temperature range 298-1800 K. The reported thermodynamic functions for Th 0.25 Ce 0.75 O 2 forms the first experimental data and the heat capacity of (Th,Ce)O 2 solid solutions was shown to obey the Neumann-Kopp's rule. (author)

Fractured Anhydrite as a Geothermal Source in a Low Enthalpy Context (Southern Permian Basin, Netherlands)

NARCIS (Netherlands)

Daniilidis, Alexandros; Herber, Marinus

2015-01-01

Increased heat flow associated with the presence of salt domes could be beneficial for geothermal energy applications in a low enthalpy nvironment. Anhydrite layers within such salt domes could be a potential geothermal target. These layers are known to undergo brittle deformation, which in turn can

Air-side performance of a micro-channel heat exchanger in wet surface conditions

Directory of Open Access Journals (Sweden)

Srisomba Raviwat

2017-01-01

Full Text Available The effects of operating conditions on the air-side heat transfer, and pressure drop of a micro-channel heat exchanger under wet surface conditions were studied experimentally. The test section was an aluminum micro-channel heat exchanger, consisting of a multi-louvered fin and multi-port mini-channels. Experiments were conducted to study the effects of inlet relative humidity, air frontal velocity, air inlet temperature, and refrigerant temperature on air-side performance. The experimental data were analyzed using the mean enthalpy difference method. The test run was performed at relative air humidities ranging between 45% and 80%; air inlet temperature ranges of 27, 30, and 33°C; refrigerant-saturated temperatures ranging from 18 to 22°C; and Reynolds numbers between 128 and 166. The results show that the inlet relative humidity, air inlet temperature, and the refrigerant temperature had significant effects on heat transfer performance and air-side pressure drop. The heat transfer coefficient and pressure drop for the micro-channel heat exchanger under wet surface conditions are proposed in terms of the Colburn j factor and Fanning f factor.

High Performance Cathodes for Li-Air Batteries

Energy Technology Data Exchange (ETDEWEB)

Xing, Yangchuan

2013-08-22

The overall objective of this project was to develop and fabricate a multifunctional cathode with high activities in acidic electrolytes for the oxygen reduction and evolution reactions for Li-air batteries. It should enable the development of Li-air batteries that operate on hybrid electrolytes, with acidic catholytes in particular. The use of hybrid electrolytes eliminates the problems of lithium reaction with water and of lithium oxide deposition in the cathode with sole organic electrolytes. The use of acid electrolytes can eliminate carbonate formation inside the cathode, making air breathing Li-air batteries viable. The tasks of the project were focused on developing hierarchical cathode structures and bifunctional catalysts. Development and testing of a prototype hybrid Li-air battery were also conducted. We succeeded in developing a hierarchical cathode structure and an effective bifunctional catalyst. We accomplished integrating the cathode with existing anode technologies and made a pouch prototype Li-air battery using sulfuric acid as catholyte. The battery cathodes contain a nanoscale multilayer structure made with carbon nanotubes and nanofibers. The structure was demonstrated to improve battery performance substantially. The bifunctional catalyst developed contains a conductive oxide support with ultra-low loading of platinum and iridium oxides. The work performed in this project has been documented in seven peer reviewed journal publications, five conference presentations, and filing of two U.S. patents. Technical details have been documented in the quarterly reports to DOE during the course of the project.

Magnetic Refrigeration Technology for High Efficiency Air Conditioning

Energy Technology Data Exchange (ETDEWEB)

Boeder, A; Zimm, C

2006-09-30

Magnetic refrigeration was investigated as an efficient, environmentally friendly, flexible alternative to conventional residential vapor compression central air conditioning systems. Finite element analysis (FEA) models of advanced geometry active magnetic regenerator (AMR) beds were developed to minimize bed size and thus magnet mass by optimizing geometry for fluid flow and heat transfer and other losses. Conventional and magnetocaloric material (MCM) regenerator fabrication and assembly techniques were developed and advanced geometry passive regenerators were built and tested. A subscale engineering prototype (SEP) magnetic air conditioner was designed, constructed and tested. A model of the AMR cycle, combined with knowledge from passive regenerator experiments and FEA results, was used to design the regenerator beds. A 1.5 Tesla permanent magnet assembly was designed using FEA and the bed structure and plenum design was extensively optimized using FEA. The SEP is a flexible magnetic refrigeration platform, with individually instrumented beds and high flow rate and high frequency capability, although the current advanced regenerator geometry beds do not meet performance expectations, probably due to manufacturing and assembly tolerances. A model of the AMR cycle was used to optimize the design of a 3 ton capacity magnetic air conditioner, and the system design was iterated to minimize external parasitic losses such as heat exchanger pressure drop and fan power. The manufacturing cost for the entire air conditioning system was estimated, and while the estimated SEER efficiency is high, the magnetic air conditioning system is not cost competitive as currently configured. The 3 ton study results indicate that there are other applications where magnetic refrigeration is anticipated to have cost advantages over conventional systems, especially applications where magnetic refrigeration, through the use of its aqueous heat transfer fluid, could eliminate intermediate

Vapor pressures and standard molar enthalpies, entropies, and Gibbs free energies of sublimation of 2,4- and 3,4-dinitrobenzoic acids

International Nuclear Information System (INIS)

Vecchio, Stefano; Brunetti, Bruno

2009-01-01

The vapor pressures of the solid and liquid 2,4- and 3,4-dinitrobenzoic acids were determined by torsion-effusion and thermogravimetry under both isothermal and non-isothermal conditions, respectively. From the temperature dependence of vapor pressure derived by the experimental torsion-effusion and thermogravimetry data the molar enthalpies of sublimation Δ cr g H m 0 ( ) and vaporization Δ l g H m 0 ( ) were determined, respectively, at the middle of the respective temperature intervals. The melting temperatures and the molar enthalpies of fusion of these compounds were measured by d.s.c. Finally, the results obtained by all the methods proposed were corrected at the reference temperature of 298.15 K using the estimated heat capacity differences between gas and liquid for vaporization experiments and the estimated heat capacity differences between gas and solid for sublimation experiments. Therefore, the averages of the standard (p o = 0.1 MPa) molar enthalpies, entropies and Gibbs free energies of sublimation at 298.15 K, have been derived.

Accurate Gas Phase Formation Enthalpies of Alloys and Refractories Decomposition Products

KAUST Repository

Minenkov, Yury

2017-01-17

Accurate gas phase formation enthalpies, ΔHf, of metal oxides and halides are critical for the prediction of the stability of high temperature materials used in the aerospace and nuclear industries. Unfortunately, the experimental ΔHf values of these compounds in the most used databases, such as the NIST-JANAF database, are often reported with large inaccuracy, while some other ΔHf values clearly differ from the value predicted by CCSD(T) methods. To address this point, in this work we systematically predicted the ΔHf values of a series of these compounds having a group 4, 6, or 14 metal. The ΔHf values in question were derived within a composite Feller-Dixon-Peterson (FDP) scheme based protocol that combines the DLPNO-CCSD(T) enthalpy of ad hoc designed reactions and the experimental ΔHf values of few reference complexes. In agreement with other theoretical studies, we predict the ΔHf values for TiOCl2, TiOF2, GeF2, and SnF4 to be significantly different from the values tabulated in NIST-JANAF and other sources, which suggests that the tabulated experimental values are inaccurate. Similarly, the predicted ΔHf values for HfCl2, HfBr2, HfI2, MoOF4, MoCl6, WOF4, WOCl4, GeO2, SnO2, PbBr4, PbI4, and PbO2 also clearly differ from the tabulated experimental values, again suggesting large inaccuracy in the experimental values. In the case when largely different experimental values are available, we point to the value that is in better agreement with our results. We expect the ΔHf values reported in this work to be quite accurate, and thus, they might be used in thermodynamic calculations, because the effects from core correlation, relativistic effects, and basis set incompleteness were included in the DLPNO-CCSD(T) calculations. T1 and T2 values were thoroughly monitored as indicators of the quality of the reference Hartree-Fock orbitals (T1) and potential multireference character of the systems (T2).

Characterization of melting and solidification in a real scale PCM-air heat exchanger: Numerical model and experimental validation

International Nuclear Information System (INIS)

Dolado, Pablo; Lazaro, Ana; Marin, Jose M.; Zalba, Belen

2011-01-01

Research highlights: → A mathematical model of a PCM-air heat exchanger is developed and validated. → Validation range is 0.7-2.1 m/s for airflow and 8-45 o C for air inlet temperature. → Better λPCM lead to minor improvement as the main resistance is mostly on air side. → 1 o C mismatch in the PCM h-T curve could lead to errors of up to 20% in power. → The accuracy of material properties' data used as inputs in the model is stressed. -- Abstract: This paper describes the models developed to simulate the performance of a thermal energy storage (TES) unit in a real scale PCM-air heat exchanger, analyzing the heat transfer between the air and a commercially available and slab macroencapsulated phase change material (PCM). The models are based on one-dimensional conduction analysis, utilizing finite differences method, and implicit formulation, using the thermo-physical data of the PCM measured in the laboratory: enthalpy and thermal conductivity as functions of temperature. The models can take into account the hysteresis of the enthalpy curve and the convection inside the PCM, using effective conductivity when necessary. Two main paths are followed to accomplish the modeling: the thermal analysis of a single plate, and the thermal behavior of the entire TES unit. Comparisons between measurements and simulations are undertaken to evaluate the models. Average errors of less than 12% on thermal power are obtained for the entire cycle. Once the model is validated, a series of parameters and variables is studied to verify their influence on the behavior and design of the TES unit.

Power-feedwater enthalpy operating domain for SBWR applying Monte Carlo simulation

International Nuclear Information System (INIS)

Quezada-Garcia, S.; Espinosa-Martinez, E.-G.; Vazquez-Rodriguez, A.; Varela-Ham, J.R.; Espinosa-Paredes, G.

2014-01-01

In this work the analyses of the feedwater enthalpy effects on reactor power in a simplified boiling water reactor (SBWR) applying a methodology based on Monte Carlo's simulation (MCS), is presented. The MCS methodology was applied systematically to establish operating domain, due that the SBWR are not yet in operation, the analysis of the nuclear and thermalhydraulic processes must rely on numerical modeling, with the purpose of developing or confirming the design basis and qualifying the existing or new computer codes to enable reliable analyses. (author)

The Relationship between Lattice Enthalpy and Melting Point in Magnesium and Aluminium Oxides. Science Notes

Science.gov (United States)

Talbot, Christopher; Yap, Lydia

2013-01-01

This "Science Note" presents a study by Christopher Talbot and Lydia Yap, who teach IB Chemistry at Anglo-Chinese School (Independent), Republic of Singapore, to pre-university students. Pre-university students may postulate the correlation between the magnitude of the lattice enthalpy compound and its melting point, since both…

Sequential water molecule binding enthalpies for aqueous nanodrops containing a mono-, di- or trivalent ion and between 20 and 500 water molecules† †Electronic supplementary information (ESI) available: Detailed description of the experimental and computational modeling methods. Isolation, BIRD and UVPD sequence for [Ru(NH3)6]3+·(H2O)169–171, nanoESI spectra for 2+ and 3+ ions. Detailed description of the isotope distribution simulation program. Comparison between experimental and simulated 1+, 2+ and 3+ ion isotope distributions. Wavelength dependence of the deduced sequential binding enthalpies. Comparison of experimental UVPD binding enthalpies to the liquid drop model at different temperatures. Complete list of binding enthalpies and average number of water molecules lost upon UVPD. See DOI: 10.1039/c6sc04957e Click here for additional data file.

Science.gov (United States)

Heiles, Sven; Cooper, Richard J.; DiTucci, Matthew J.

2017-01-01

Sequential water molecule binding enthalpies, ΔH n,n–1, are important for a detailed understanding of competitive interactions between ions, water and solute molecules, and how these interactions affect physical properties of ion-containing nanodrops that are important in aerosol chemistry. Water molecule binding enthalpies have been measured for small clusters of many different ions, but these values for ion-containing nanodrops containing more than 20 water molecules are scarce. Here, ΔH n,n–1 values are deduced from high-precision ultraviolet photodissociation (UVPD) measurements as a function of ion identity, charge state and cluster size between 20–500 water molecules and for ions with +1, +2 and +3 charges. The ΔH n,n–1 values are obtained from the number of water molecules lost upon photoexcitation at a known wavelength, and modeling of the release of energy into the translational, rotational and vibrational motions of the products. The ΔH n,n–1 values range from 36.82 to 50.21 kJ mol–1. For clusters containing more than ∼250 water molecules, the binding enthalpies are between the bulk heat of vaporization (44.8 kJ mol–1) and the sublimation enthalpy of bulk ice (51.0 kJ mol–1). These values depend on ion charge state for clusters with fewer than 150 water molecules, but there is a negligible dependence at larger size. There is a minimum in the ΔH n,n–1 values that depends on the cluster size and ion charge state, which can be attributed to the competing effects of ion solvation and surface energy. The experimental ΔH n,n–1 values can be fit to the Thomson liquid drop model (TLDM) using bulk ice parameters. By optimizing the surface tension and temperature change of the logarithmic partial pressure for the TLDM, the experimental sequential water molecule binding enthalpies can be fit with an accuracy of ±3.3 kJ mol–1 over the entire range of cluster sizes. PMID:28451364

Junior High School Pupils' Perceptions of Air

African Journals Online (AJOL)

cce

Abstract. The study examined Junior High School (JHS) pupils' ideas of the concept air. The ... Stavy (1991) reported that students in his physics class had ... Research studies found that even after having been taught the particulate theory and.

Bayesian Statistical Mechanics: Entropy-Enthalpy Compensation and Universal Equation of State at the Tip of Pen

Directory of Open Access Journals (Sweden)

Evgeni B. Starikov

2018-02-01

Full Text Available This work has shown the way to put the formal statistical-mechanical basement under the hotly debated notion of enthalpy-entropy compensation. The possibility of writing down the universal equation of state based upon the statistical mechanics is discussed here.

Determination of saturation pressure and enthalpy of vaporization of semi-volatile aerosols: the integrated volume mentod

Science.gov (United States)

This study presents the integrated volume method for estimating saturation pressure and enthalpy of vaporization of a whole aerosol distribution. We measure the change of total volume of an aerosol distribution between a reference state and several heated states, with the heating...

Prediction of enthalpy of fusion of pure compounds using an Artificial Neural Network-Group Contribution method

International Nuclear Information System (INIS)

Gharagheizi, Farhad; Salehi, Gholam Reza

2011-01-01

Highlights: → An Artificial Neural Network-Group Contribution method is presented for prediction of enthalpy of fusion of pure compounds at their normal melting point. → Validity of the model is confirmed using a large evaluated data set containing 4157 pure compounds. → The average percent error of the model is equal to 2.65% in comparison with the experimental data. - Abstract: In this work, the Artificial Neural Network-Group Contribution (ANN-GC) method is applied to estimate the enthalpy of fusion of pure chemical compounds at their normal melting point. 4157 pure compounds from various chemical families are investigated to propose a comprehensive and predictive model. The obtained results show the Squared Correlation Coefficient (R 2 ) of 0.999, Root Mean Square Error of 0.82 kJ/mol, and average absolute deviation lower than 2.65% for the estimated properties from existing experimental values.

Large high altitude air shower observatory (LHAASO) project

International Nuclear Information System (INIS)

He Huihai

2010-01-01

The Large High Altitude Air Shower Observatory (LHAASO) project focuses mainly on the study of 40 GeV-1 PeV gamma ray astronomy and 10 TeV-1 EeV cosmic ray physics. It consists of a 1 km 2 extensive air shower array with 40 000 m 2 muon detectors, 90,000m 2 water Cerenkov detector array, 5 000 m 2 shower core detector array and an air Cerenkov/fluorescence telescope array. Prototype detectors are designed with some of them already in operation. A prototype array of 1% size of LHAASO will be built at the Yangbajing Cosmic Ray Observatory and used to coincidently measure cosmic rays with the ARGO-YBJ experiment. (authors)

Analytic Methods for Tactical Air Warfare. Air Campaign and High-Energy Laser Propagation Analyses

National Research Council Canada - National Science Library

Lee, David

2004-01-01

.... The report describes a probabilistic model of campaigns for air superiority between two opponents, an analysis of force concentration in deterministic Lanchester campaigns, and an analysis of high...

The Correlation of Standard Entropy with Enthalpy Supplied from 0 to 298.15 K

Science.gov (United States)

Lambert, Frank L.; Leff, Harvey S.

2009-01-01

As a substance is heated at constant pressure from near 0 K to 298 K, each incremental enthalpy increase, dH, alters entropy by dH/T, bringing it from approximately zero to its standard molar entropy S degrees. Using heat capacity data for 32 solids and CODATA results for another 45, we found a roughly linear relationship between S degrees and…

Hypothetical air ingress scenarios in advanced modular high temperature gas cooled reactors

International Nuclear Information System (INIS)

Kroeger, P.G.

1988-01-01

Considering an extremely hypothetical scenario of complete cross duct failure and unlimited air supply into the reactor vessel of a modular high temperature gas cooled ractor, it is found that the potential air inflow remains limited due to the high friction pressure drop through the active core. All incoming air will be oxidized to CO and some local external burning would be temporarily possible in such a scenario. The accident would have to continue with unlimited air supply for hundreds of hours before the core structural integrity would be jeopardized

Enthalpies of formation of europium alkoxides: What lessons can be drawn from them

International Nuclear Information System (INIS)

Branco, Joaquim B.; Carretas, José M.; Epple, Matthias; Cruz, Adelaide; Pires de Matos, A.; Leal, João Paulo

2014-01-01

Highlights: • First time measurement of europium(II) alkoxides enthalpy of formation. • Calculation of alkoxides thermochemical radii and M–O distances in this environment. • Comparison of experimental EXAFS distance with the calculated ones. • Hints on the type of bond existing in these compounds. • Correlation of bond type and possible use as catalysts. - Abstract: The synthesis and characterization of two europium alkoxides, Eu(OCH 3 ) 2 and Eu(OC 2 H 5 ) 2 , were described. For the first time the enthalpies of formation of divalent lanthanide alkoxides were determined by using reaction-solution calorimetry. The values obtained are Δ f H 0 [Eu(OCH 3 ) 2 ,cr] = −850.5 ± 5.0 kJ/mol and Δ f H 0 [Eu(OC 2 H 5 ) 2 ,cr] = −902.5 ± 5.5 kJ/mol, respectively. Since these compounds have a large use as catalysts or catalysts precursors, the first step of the reaction of them with CO 2 was addressed, which permits to have an idea of the kind of bond involved in those compounds. Moreover, insertion of CO 2 in the europium oxygen bond and formation of metal carboxylate complexes, is in both cases presumably bidentate

Three-dimensional quantitative structure-property relationship (3D-QSPR) models for prediction of thermodynamic properties of polychlorinated biphenyls (PCBs): enthalpy of vaporization.

Science.gov (United States)

Puri, Swati; Chickos, James S; Welsh, William J

2002-01-01

Three-dimensional Quantitative Structure-Property Relationship (QSPR) models have been derived using Comparative Molecular Field Analysis (CoMFA) to correlate the vaporization enthalpies of a representative set of polychlorinated biphenyls (PCBs) at 298.15 K with their CoMFA-calculated physicochemical properties. Various alignment schemes, such as inertial, as is, and atom fit, were employed in this study. The CoMFA models were also developed using different partial charge formalisms, namely, electrostatic potential (ESP) charges and Gasteiger-Marsili (GM) charges. The most predictive model for vaporization enthalpy (Delta(vap)H(m)(298.15 K)), with atom fit alignment and Gasteiger-Marsili charges, yielded r2 values 0.852 (cross-validated) and 0.996 (conventional). The vaporization enthalpies of PCBs increased with the number of chlorine atoms and were found to be larger for the meta- and para-substituted isomers. This model was used to predict Delta(vap)H(m)(298.15 K) of the entire set of 209 PCB congeners.

Metal-air batteries with high energy density: Li-air versus Zn-air

Energy Technology Data Exchange (ETDEWEB)

Lee, Jang-Soo; Sun, Tai Kim; Cao, Ruiguo; Choi, Nam-Soon; Lee, Kyu Tae; Cho, Jaephil [Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology (UNIST), Ulsan (Korea, Republic of); Liu, Meilin [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA (United States)

2011-01-01

In the past decade, there have been exciting developments in the field of lithium ion batteries as energy storage devices, resulting in the application of lithium ion batteries in areas ranging from small portable electric devices to large power systems such as hybrid electric vehicles. However, the maximum energy density of current lithium ion batteries having topatactic chemistry is not sufficient to meet the demands of new markets in such areas as electric vehicles. Therefore, new electrochemical systems with higher energy densities are being sought, and metal-air batteries with conversion chemistry are considered a promising candidate. More recently, promising electrochemical performance has driven much research interest in Li-air and Zn-air batteries. This review provides an overview of the fundamentals and recent progress in the area of Li-air and Zn-air batteries, with the aim of providing a better understanding of the new electrochemical systems. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Quantum statistical vibrational entropy and enthalpy of formation of helium-vacancy complex in BCC W

Energy Technology Data Exchange (ETDEWEB)

Wen, Haohua [Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, 519082, Zhuhai (China); Woo, C.H., E-mail: chung.woo@polyu.edu.hk [ME Department, The Hong Kong Polytechnic University, Hong Kong SAR (China)

2016-12-15

High-temperature advance-reactor design and operation require knowledge of in-reactor materials properties far from the thermal ground state. Temperature-dependence due to the effects of lattice vibrations is important to the understanding and formulation of atomic processes involved in irradiation-damage accumulation. In this paper, we concentrate on the formation of He-V complex. The free-energy change in this regard is derived via thermodynamic integration from the phase-space trajectories generated from MD simulations based on the quantum fluctuation-dissipation relation. The change of frequency distribution of vibration modes during the complex formation is properly accounted for, and the corresponding entropy change avoids the classical ln(T) divergence that violates the third law. The vibrational enthalpy and entropy of formation calculated this way have significant effects on the He kinetics during irradiation.

Hybrid Solar-Geothermal Energy Absorption Air-Conditioning System Operating with NaOH-H2O—Las Tres Vírgenes (Baja California Sur), “La Reforma” Case

OpenAIRE

Yuridiana Rocio Galindo-Luna; Efraín Gómez-Arias; Rosenberg J. Romero; Eduardo Venegas-Reyes; Moisés Montiel-González; Helene Emmi Karin Unland-Weiss; Pedro Pacheco-Hernández; Antonio González-Fernández; Jorge Díaz-Salgado

2018-01-01

Solar and geothermal energies are considered cleaner and more useful energy sources that can be used to avoid the negative environmental impacts caused by burning fossil fuels. Several works have reported air-conditioning systems that use solar energy coupled to geothermal renewable energy as a thermal source. In this study, an Absorption Air-Conditioning System (AACS) used sodium hydroxide-water (NaOH-H2O) instead of lithium bromide-water to reduce the cost. Low enthalpy geothermal heat was ...

An evaluation of interferences in heat production from low enthalpy geothermal doublets systems

DEFF Research Database (Denmark)

Willems, Cees J. L.; Nick, Hamidreza M.; Weltje, Gert Jan

2017-01-01

Required distance between doublet systems in low enthalpy geothermal heat exploitation is often not fully elucidated. The required distance aims to prevent negative interference influencing the utilisation efficiency of doublet systems. Currently production licence areas are often issued based...... and minimal required production temperature. The results of this study can be used to minimize negative interference or optimise positive interference aiming at improving geothermal doublet deployment efficiency. (C) 2017 The Authors. Published by Elsevier Ltd....

Utilization of secondary energy - major uses in the fermentation and beverage industries

Energy Technology Data Exchange (ETDEWEB)

Koch, H J

1986-01-01

With 18,5% the fermentation and beverage industry (not including liquors, wine and champagne) has the highest share of energy consumption within the food industry. At the same time, these two branches dispose of high secondary energy potentials which remain to be exploited yet. Secondary energy utilization primarily consists in the economic cooling of wort providing for the utilization of process water (80-82/sup 0/C), utilization of air-containing or air-void water vapors from wort boiling processes for technological heating processes, utilization of refrigerator super-heat enthalpies, the use of energy, conserving high-short heaters for larger units, in particular, and utilization of flue gas enthalpies with gaseous energy sources as the most efficient ones.

Vapor pressures and sublimation enthalpies of seven heteroatomic aromatic hydrocarbons measured using the Knudsen effusion technique

International Nuclear Information System (INIS)

Goldfarb, Jillian L.; Suuberg, Eric M.

2010-01-01

The vapor pressures of seven heteroatom-containing cyclic aromatic hydrocarbons, ranging in molecular weight from (168.19 to 208.21) g . mol -1 were measured over the temperature range of (301 to 486) K using the isothermal Knudsen effusion technique. The compounds measured include: anthraquinone, 9-fluorenone, 9-fluorenone oxime, phenoxazine, phenoxathiin, and 9H-pyrido[3,4-b]indole. These solid-state sublimation measurements provided values that are compared to vapor pressures of parent aromatic compounds (anthracene and fluorene) and to others with substituent groups in order to examine the effects of alcohol, ketone, pyridine, and pyrrole functionality on this property. The enthalpies and entropies of sublimation for each compound were determined from the Clausius-Clapeyron equation. Though there is no consistent trend in terms of the effects of substitutions on changes in the enthalpy or entropy of sublimation, we note that the prevalence of enthalpic or entropic driving forces on vapor pressure depend on molecule-specific factors and not merely molecular weight of the substituents.

Enthalpy of solution of α- and β-cyclodextrin in water and in some organic solvents

International Nuclear Information System (INIS)

Belica, Sylwia; Sadowska, Monika; Stępniak, Artur; Graca, Anna; Pałecz, Bartłomiej

2014-01-01

Highlights: • A great influence of crystalline water on the energetic of dissolving compounds. • The strongest interaction between β-cyclodextrin and DMSO. • The enthalpic pair interaction coefficient, h βCD-EtOH , obtained is positive. • Predominating effects of the partial dehydration of the molecules – βCD-EtOH. -- Abstract: The calorimetric measurements of solution enthalpy of α-cyclodextrin, β-cyclodextrin in water (H 2 O), dimetyloformamid (DMF), dimethyl sulfoxide (DMSO) and aqueous ethanol solutions (H 2 O + EtOH) at 298.15 K were made. The experimental results were used to calculate the enthalpic coefficients of the interactions between cyclodextrin and ethanol molecules in water based on McMillan–Mayer’s model. The results were compared with literature data and with hydrodynamic radii of cyclodextrin in examined solvents and with donor numbers of these solvents. In order to check, if the inclusion complex formation between the solvent with the highest enthalpy of solution and cyclodextrin has happened, the calorimetric isothermal titration measurements were made and the results were interpreted

The propagation of high power CW scanning electron beam in air

International Nuclear Information System (INIS)

Korenev, Sergey; Korenev, Ivan

2002-01-01

The question of propagation of high power electron beam in air presents the scientific and applied interests. The high power (80 kW) CW electron accelerator 'Rhodotron' with kinetic energy of electrons 5 and 10 MeV was used in the experiments. The experimental results for propagation of scanning electron beams in air are presented and discussed

Energetics and stability of azulene: From experimental thermochemistry to high-level quantum chemical calculations

International Nuclear Information System (INIS)

Sousa, Clara C.S.; Matos, M. Agostinha R.; Morais, Victor M.F.

2014-01-01

Highlights: • Experimental standard molar enthalpy of formation, sublimation azulene. • Mini-bomb combustion calorimetry, sublimation Calvet microcalorimetry. • High level composite ab initio calculations. • Computational estimate of the enthalpy of formation of azulene. • Discussion of stability and aromaticity of azulene. - Abstract: The standard (p 0 = 0.1 MPa) molar enthalpy of formation for crystalline azulene was derived from the standard molar enthalpy of combustion, in oxygen, at T = 298.15 K, measured in a mini-bomb combustion calorimeter (aneroid isoperibol calorimeter) and the standard molar enthalpy of sublimation, at T = 298.15 K, measured by Calvet microcalorimetry. From these experiments, the standard molar enthalpy of formation of azulene in the gaseous phase at T = 298.15 K was calculated. In addition, very accurate quantum chemical calculations at the G3 and G4 composite levels of calculation were conducted in order to corroborate our experimental findings and further clarify and establish the definitive standard enthalpy of formation of this interesting non-benzenoid hydrocarbon

Search and Rescue in the High North: An Air Force Mission?

Science.gov (United States)

2013-12-01

at the strange new things in the land of the midnight sun. What wouldn’t surprise him are the things that never change: six months of darkness ...8-98) Prescribed by ANSI Std Z39-18 November–December 2013 Air & Space Power Journal | 5 Conway Search and Rescue in the High North Feature tourism ...official sanction of the Department of Defense, Air Force, Air Education and Training Command, Air University, or other agencies or departments of

An improved high-performance lithium-air battery.

Science.gov (United States)

Jung, Hun-Gi; Hassoun, Jusef; Park, Jin-Bum; Sun, Yang-Kook; Scrosati, Bruno

2012-06-10

Although dominating the consumer electronics markets as the power source of choice for popular portable devices, the common lithium battery is not yet suited for use in sustainable electrified road transport. The development of advanced, higher-energy lithium batteries is essential in the rapid establishment of the electric car market. Owing to its exceptionally high energy potentiality, the lithium-air battery is a very appealing candidate for fulfilling this role. However, the performance of such batteries has been limited to only a few charge-discharge cycles with low rate capability. Here, by choosing a suitable stable electrolyte and appropriate cell design, we demonstrate a lithium-air battery capable of operating over many cycles with capacity and rate values as high as 5,000 mAh g(carbon)(-1) and 3 A g(carbon)(-1), respectively. For this battery we estimate an energy density value that is much higher than those offered by the currently available lithium-ion battery technology.

Changes of enthalpy slope in subcooled flow boiling

Energy Technology Data Exchange (ETDEWEB)

Collado, Francisco J.; Monne, Carlos [Universidad de Zaragoza-CPS, Departamento de Ingenieria Mecanica-Motores Termicos, Zaragoza (Spain); Pascau, Antonio [Universidad de Zaragoza-CPS, Departamento de Ciencia de los Materiales y Fluidos-Mecanica de Fluidos, Zaragoza (Spain)

2006-03-01

Void fraction data in subcooled flow boiling of water at low pressure measured by General Electric in the 1960s are analyzed following the classical model of Griffith et al. (in Proceedings of ASME-AIChE heat transfer conference, 58-HT-19, 1958). In addition, a new proposal for analyzing one-dimensional steady flow boiling is used. This is based on the physical fact that if the two phases have different velocities, they cannot cover the same distance - the control volume length - in the same time. So a slight modification of the heat balance is suggested, i.e., the explicit inclusion of the vapor-liquid velocity ratio or slip ratio as scaling time factor between the phases, which is successfully checked against the data. Finally, the prediction of void fraction using correlations of the net rate of change of vapor enthalpy in the fully developed regime of subcooled flow boiling is explored. (orig.)

Mechanism of ion adsorption to aqueous interfaces: Graphene/water vs. air/water.

Science.gov (United States)

McCaffrey, Debra L; Nguyen, Son C; Cox, Stephen J; Weller, Horst; Alivisatos, A Paul; Geissler, Phillip L; Saykally, Richard J

2017-12-19

The adsorption of ions to aqueous interfaces is a phenomenon that profoundly influences vital processes in many areas of science, including biology, atmospheric chemistry, electrical energy storage, and water process engineering. Although classical electrostatics theory predicts that ions are repelled from water/hydrophobe (e.g., air/water) interfaces, both computer simulations and experiments have shown that chaotropic ions actually exhibit enhanced concentrations at the air/water interface. Although mechanistic pictures have been developed to explain this counterintuitive observation, their general applicability, particularly in the presence of material substrates, remains unclear. Here we investigate ion adsorption to the model interface formed by water and graphene. Deep UV second harmonic generation measurements of the SCN - ion, a prototypical chaotrope, determined a free energy of adsorption within error of that for air/water. Unlike for the air/water interface, wherein repartitioning of the solvent energy drives ion adsorption, our computer simulations reveal that direct ion/graphene interactions dominate the favorable enthalpy change. Moreover, the graphene sheets dampen capillary waves such that rotational anisotropy of the solute, if present, is the dominant entropy contribution, in contrast to the air/water interface.

Thermodynamic study of rhodamine 123-calf thymus DNA interaction: determination of calorimetric enthalpy by optical melting study.

Science.gov (United States)

Masum, Abdulla Al; Chakraborty, Maharudra; Pandya, Prateek; Halder, Umesh Chandra; Islam, Md Maidul; Mukhopadhyay, Subrata

2014-11-20

In this paper, the interaction of rhodamine123 (R123) with calf thymus DNA has been studied using molecular modeling and other biophysical methods like UV-vis spectroscopy, fluoremetry, optical melting, isothermal titration calorimetry, and circular dichroic studies. Results showed that the binding energy is about -6 to -8 kcal/mol, and the binding process is favored by both negative enthalpy change and positive entropy change. A new method to determine different thermodynamic properties like calorimetric enthalpy and heat capacity change has been introduced in this paper. The obtained data has been crossed-checked by other methods. After dissecting the free-energy contribution, it was observed that the binding was favored by both negative hydrophobic free energy and negative molecular free energy which compensated for the positive free energies due to the conformational change loss of rotational and transitional freedom of the DNA helix.

High efficiency steel filters for nuclear air cleaning

International Nuclear Information System (INIS)

Bergman, W.; Conner, J.; Larsen, G.; Lopez, R.; Turner, C.; Vahla, G.; Violet, C.; Williams, K.

1991-01-01

The authors have, in cooperation with industry, developed high-efficiency filters made from sintered stainless-steel fibers for use in several air-cleaning applications in the nuclear industry. These filters were developed to overcome the failure modes in present high-efficiently particulate air (HEPA) filters. HEPA filters are made from glass paper and glue, and they may fail when they get hot or wet and when they are overpressured. In developing steel filters, they first evaluated the commercially available stainless-steel filter media made from sintered powder and sintered fiber. The sintered-fiber media performed much better than sintered-powder media, and the best media had the smallest fiber diameter. Using the best media, prototype filters were then built for venting compressed gases and evaluated in their automated filter tester

An Investigation of Applications for Thermodynamic Work Potential Methods: Working Tables and Charts for Estimation of Thermodynamic Work Potential in Equilibrium Mixtures of Jet-A and Air

Science.gov (United States)

Mavris, Dimitri; Roth, Bryce; McDonald, Rob

2002-01-01

The objective of this report is to provide a tool to facilitate the application of thermodynamic work potential methods to aircraft and engine analysis. This starts with a discussion of the theoretical background underlying these methods, which is then used to derive various equations useful for thermodynamic analysis of aircraft engines. The work potential analysis method is implemented in the form of a set of working charts and tables that can be used to graphically evaluate work potential stored in high-enthalpy gas. The range of validity for these tables is 300 to 36,000 R, pressures between between 0.01 atm and 100 atm, and fuel-air ratios from zero to stoichiometric. The derivations and charts assume mixtures of Jet-A and air as the working fluid. The thermodynamic properties presented in these charts were calculated based upon standard thermodynamic curve fits.

Enthalpy of formation of vanadates of iron, chromium, and aluminum

Energy Technology Data Exchange (ETDEWEB)

Kesler, Y.A.; Cheshnitskii, S.M.; Fotiev, A.A.; Tret' yakov, Y.D.

1985-09-01

The study of vanadates of iron, aluminum and chromium is of importance for the analysis of the functioning of catalysts of organic synthesis reactions and for the study of vanadium corrosion of structural materials. Of principal interest, however, are the processes in the treatment of vanadium-containing metallurgical slags and waste from thermal power plants, in which these compounds play a major role. At the same time, the thermochemical properties of these substances, which are necessary for creating the physicochemical foundations of industrially important processes, have not been investigated sufficiently. The authors therefore undertake here a study of the compounds FeVO/sub 4/, AIVO/sub 4/, CrVO/sub 4/ and FeCr(VO/sub 4/)/sub 2/, to determine their enthalpies of formation.

Dosimetric Effects of Air Pockets Around High-Dose Rate Brachytherapy Vaginal Cylinders

International Nuclear Information System (INIS)

Richardson, Susan; Palaniswaamy, Geethpriya; Grigsby, Perry W.

2010-01-01

Purpose: Most physicians use a single-channel vaginal cylinder for postoperative endometrial cancer brachytherapy. Recent published data have identified air pockets between the vaginal cylinders and the vaginal mucosa. The purpose of this research was to evaluate the incidence, size, and dosimetric effects of these air pockets. Methods and Materials: 25 patients receiving postoperative vaginal cuff brachytherapy with a high-dose rate vaginal cylinders were enrolled in this prospective data collection study. Patients were treated with 6 fractions of 200 to 400 cGy per fraction prescribed at 5 mm depth. Computed tomography simulation for brachytherapy treatment planning was performed for each fraction. The quantity, volume, and dosimetric impact of the air pockets surrounding the cylinder were quantified. Results: In 25 patients, a total of 90 air pockets were present in 150 procedures (60%). Five patients had no air pockets present during any of their treatments. The average number of air pockets per patient was 3.6, with the average total air pocket volume being 0.34 cm 3 (range, 0.01-1.32 cm 3 ). The average dose reduction to the vaginal mucosa at the air pocket was 27% (range, 9-58%). Ten patients had no air pockets on their first fraction but air pockets occurred in subsequent fractions. Conclusion: Air pockets between high-dose rate vaginal cylinder applicators and the vaginal mucosa are present in the majority of fractions of therapy, and their presence varies from patient to patient and fraction to fraction. The existence of air pockets results in reduced radiation dose to the vaginal mucosa.

Optimization analysis of high temperature heat pump coupling to desiccant wheel air conditioning system

DEFF Research Database (Denmark)

Sheng, Ying; Zhang, Yufeng; Fang, Lei

2014-01-01

The high temperature heat pump and desiccant wheel (HTHP&DW) system can make full use of heat released from the condenser of heat pump for DW regeneration without additional heat. In this study, DW operation in the HTHP&DW system was investigated experimentally, and the optimization analysis...... of HTHP&DW system was carried out. The performance of DW had influence on the dehumidification (evaluated by dehumidification and regeneration effectiveness) and cooling load (evaluated by thermal and adiabatic effectiveness). The results show that the enthalpy increase occurred in all the experiments...... of the system. When the regeneration temperature is 63°C, the maximal dehumidification effectiveness is 35.4% and the satisfied adiabatic effectiveness is 88%, which contributes to the optimal balance between dehumidification and cooling. © 2014 Tianjin University and Springer-Verlag Berlin Heidelberg....

Vapor pressures and sublimation enthalpies of seven heteroatomic aromatic hydrocarbons measured using the Knudsen effusion technique

Energy Technology Data Exchange (ETDEWEB)

Goldfarb, Jillian L., E-mail: JillianLGoldfarb@gmail.co [Division of Engineering, Brown University, Providence, RI 02912 (United States); Suuberg, Eric M., E-mail: Eric_Suuberg@brown.ed [Division of Engineering, Brown University, Providence, RI 02912 (United States)

2010-06-15

The vapor pressures of seven heteroatom-containing cyclic aromatic hydrocarbons, ranging in molecular weight from (168.19 to 208.21) g . mol{sup -1} were measured over the temperature range of (301 to 486) K using the isothermal Knudsen effusion technique. The compounds measured include: anthraquinone, 9-fluorenone, 9-fluorenone oxime, phenoxazine, phenoxathiin, and 9H-pyrido[3,4-b]indole. These solid-state sublimation measurements provided values that are compared to vapor pressures of parent aromatic compounds (anthracene and fluorene) and to others with substituent groups in order to examine the effects of alcohol, ketone, pyridine, and pyrrole functionality on this property. The enthalpies and entropies of sublimation for each compound were determined from the Clausius-Clapeyron equation. Though there is no consistent trend in terms of the effects of substitutions on changes in the enthalpy or entropy of sublimation, we note that the prevalence of enthalpic or entropic driving forces on vapor pressure depend on molecule-specific factors and not merely molecular weight of the substituents.

Direct Determination Of γ′ / γ′+γ / γ Phase Boundaries In Ni-Al-Cr System Based On Enthalpy Of Formation Results Obtained By Calorimetric Solution Method

Directory of Open Access Journals (Sweden)

Maciąg T.

2015-09-01

Full Text Available The work is a continuation of the research carried out on a high-temperature calorimeter solution type on alloys from Ni-Al-Cr system. Thanks to the construction innovation introduced by authors the device allows the determination of the formation enthalpy of alloys at ambient and elevated temperatures. Experiments described in this article were carried out at three temperatures: 873K, 996K and 1150K on the alloys of the chemical compositions from the Ni75Al25 ÷ Ni87Cr13 section of the Ni-Al-Cr system. On the basis of changes in the enthalpy of formation with increasing chromium content of the alloys, points corresponding to places of phase boundaries γ′ / γ′+γ / γ in Ni-Al-Cr system were determined. A similar relationship was observed in previous studies of alloys from Ni75Al25÷Ni75Cr25 section. For precise determination of these characteristic points a statistical model was applied

Is the perception of clean, humid air indeed affected by cooling the respiratory tract?

Science.gov (United States)

Burek, Rudolf; Polednik, Bernard; Guz, Łukasz

2017-07-01

The study aims at determining exposure-response relationships after short exposure to clean air and long exposure to air polluted by people. The impact of water vapor content in the indoor air on its acceptability (ACC) was assessed by the occupants after a short exposure to clean air and an hour-long exposure to increasingly polluted air. The study presents a critical analysis pertaining to the stimulation of olfactory sensations by the air enthalpy suggested in previous models and proposes a new model based on the Weber-Fechner law. Our assumption was that water vapor is the stimulus of olfactory sensations. The model was calibrated and verified in field conditions, in a mechanically ventilated and air conditioned auditorium. Measurements of the air temperature, relative humidity, velocity and CO2 content were carried out; the acceptability of air quality was assessed by 162 untrained students. The subjective assessments and the measurements of the environmental qualities allowed for determining the Weber coefficients and the threshold concentrations of water vapor, as well as for establishing the limitations of the model at short and long exposure to polluted indoor air. The results are in agreement with previous studies. The standard error equals 0.07 for immediate assessments and 0.17 for assessments after adaptation. Based on the model one can predict the ACC assessments of trained and untrained participants.

High-energy metal air batteries

Science.gov (United States)

Zhang, Ji-Guang; Xiao, Jie; Xu, Wu; Wang, Deyu; Williford, Ralph E.; Liu, Jun

2013-07-09

Disclosed herein are embodiments of lithium/air batteries and methods of making and using the same. Certain embodiments are pouch-cell batteries encased within an oxygen-permeable membrane packaging material that is less than 2% of the total battery weight. Some embodiments include a hybrid air electrode comprising carbon and an ion insertion material, wherein the mass ratio of ion insertion material to carbon is 0.2 to 0.8. The air electrode may include hydrophobic, porous fibers. In particular embodiments, the air electrode is soaked with an electrolyte comprising one or more solvents including dimethyl ether, and the dimethyl ether subsequently is evacuated from the soaked electrode. In other embodiments, the electrolyte comprises 10-20% crown ether by weight.

Determination of the free enthalpies of formation of borosilicate glasses

International Nuclear Information System (INIS)

Linard, Y.

2000-01-01

This work contributes to the study of the thermochemical properties of nuclear waste glasses. Results are used to discuss mechanisms and parameters integrated in alteration models of conditioning materials. Glass is a disordered material defined thermodynamically as a non-equilibrium state. Taking into account one order parameter to characterise its configurational state, the metastable equilibrium for the glass was considered and the main thermochemical properties were determined. Calorimetric techniques were used to measure heat capacities and formation enthalpies of borosilicate glasses (from 3 to 8 constitutive oxides). Formation Entropies were measured too, using the entropy theory of relaxation processes proposed by Adam and Gibbs (1965). The configurational entropy contribution were determined from viscosity measurements. This set of data has allowed the calculation of Gibb's free energies of dissolution of glasses in pure water. By comparison with leaching experiments, it has been demonstrated that the decreasing of the dissolution rate at high reaction progress cannot be associated to the approach of an equilibrium between the sound glass and the aqueous solution. The composition changes of the reaction area at the glass surface need to be considered too. To achieve a complete description of the thermodynamic stability, the equilibrium between hydrated de-alkalinized glass and/or the gel layer with the aqueous solution should also be evaluated. (author)

Flat plate solar air heater with latent heat storage

Science.gov (United States)

Touati, B.; Kerroumi, N.; Virgone, J.

2017-02-01

Our work contains two parts, first is an experimental study of the solar air heater with a simple flow and forced convection, we can use thatlaste oneit in many engineering's sectors as solardrying, space heating in particular. The second part is a numerical study with ansys fluent 15 of the storage of part of this solar thermal energy produced,using latent heat by using phase change materials (PCM). In the experimental parts, we realize and tested our solar air heater in URER.MS ADRAR, locate in southwest Algeria. Where we measured the solarradiation, ambient temperature, air flow, thetemperature of the absorber, glasses and the outlet temperature of the solar air heater from the Sunrise to the sunset. In the second part, we added a PCM at outlet part of the solar air heater. This PCM store a part of the energy produced in the day to be used in peak period at evening by using the latent heat where the PCMs present a grateful storagesystem.A numerical study of the fusion or also named the charging of the PCM using ANSYS Fluent 15, this code use the method of enthalpies to solve the fusion and solidification formulations. Furthermore, to improve the conjugate heat transfer between the heat transfer fluid (Air heated in solar plate air heater) and the PCM, we simulate the effect of adding fins to our geometry. Also, four user define are write in C code to describe the thermophysicalpropriety of the PCM, and the inlet temperature of our geometry which is the temperature at the outflow of the solar heater.

High-Performance Lithium-Air Battery with a Coaxial-Fiber Architecture.

Science.gov (United States)

Zhang, Ye; Wang, Lie; Guo, Ziyang; Xu, Yifan; Wang, Yonggang; Peng, Huisheng

2016-03-24

The lithium-air battery has been proposed as the next-generation energy-storage device with a much higher energy density compared with the conventional lithium-ion battery. However, lithium-air batteries currently suffer enormous problems including parasitic reactions, low recyclability in air, degradation, and leakage of liquid electrolyte. Besides, they are designed into a rigid bulk structure that cannot meet the flexible requirement in the modern electronics. Herein, for the first time, a new family of fiber-shaped lithium-air batteries with high electrochemical performances and flexibility has been developed. The battery exhibited a discharge capacity of 12,470 mAh g(-1) and could stably work for 100 cycles in air; its electrochemical performances were well maintained under bending and after bending. It was also wearable and formed flexible power textiles for various electronic devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-Performance Carbon Aerogel Air Cathodes for Microbial Fuel Cells

KAUST Repository

Zhang, Xiaoyuan

2016-08-11

Microbial fuel cells (MFCs) can generate electricity from the oxidation of organic substrates using anodic exoelectrogenic bacteria and have great potential for harvesting electric energy from wastewater. Improving oxygen reduction reaction (ORR) performance at a neutral pH is needed for efficient energy production. Here we show a nitrogen doped (≈4 wt%) ionothermal carbon aerogel (NDC) with a high surface area, large pore volume, and hierarchical porosity, with good electrocatalytic properties for ORR in MFCs. The MFCs using NDC air cathodes achieved a high maximum power density of 2300 mW m−2, which was 1.7 times higher than the most commonly used Pt/C air cathodes and also higher than most state-of-the-art ORR catalyst air cathodes. Rotating disk electrode measurements verified the superior electrocatalytic activity of NDC with an efficient four-electron transfer pathway (n=3.9). These findings highlight NDC as a better-performing and cost-efficient catalyst compared with Pt/C, making it highly viable for MFC applications.

Experimental and predicted data of excess molar enthalpies and excess molar volumes for the ternary system (1,3-dichlorobenzene + benzene + 1-chlorohexane) at T = 298.15 K

International Nuclear Information System (INIS)

Mato, Marta M.; Verdes, Pedro V.; Paz Andrade, M.I.; Legido, José Luis

2014-01-01

Graphical abstract: - Highlights: • Experimental enthalpy and densitiy for the mixture 1,3-dichlorobenzene + benzene + 1-chlorohexane were measured. • The excess molar volumes were calculated from the densities of the pure liquids and their mixtures. • The Cibulka equation was used to correlate the ternary contribution of the excess molar properties. • The experimental data were used to test several empirical equations. - Abstract: Experimental excess molar enthalpies, densities and excess molar volumes for the ternary system {x 1 1,3-dichlorobenzene + x 2 benzene + (1 − x 1 − x 2 ) 1-chlorohexane} have been determined at the temperature of 298.15 K and atmospheric pressure. Values of excess molar enthalpies were measured using a Calvet microcalorimeter, and excess molar volumes were determined from the densities of the pure liquids and mixtures, using a vibrating-tube densimeter. The results were fitted by means of different variable degree polynomials. Smooth representations of the results are presented and used to construct constant contours of excess molar enthalpy and excess molar volume on Roozeboom diagrams. Several empirical expressions that have been suggested for use with parameters and predicting excess properties of ternary mixtures from the experimental binary data were tested

The vapor pressure and vaporization enthalpy of R-(+)-menthofuran, a hepatotoxin metabolically derived from the abortifacient terpene, (R)-(+)-pulegone by correlation gas chromatography

International Nuclear Information System (INIS)

Gobble, Chase; Chickos, James S.

2016-01-01

Highlights: • The vaporization enthalpy and vapor pressure of R-(+) menthofuran is evaluated. • The normal boiling temperature is predicted and compared to experimental and predicted values. • A vapor pressure equation as a function of temperature for menthofuran is evaluated. - Abstract: The vapor pressure as a function of temperature and its vaporization enthalpy at T = 298.15 K of R-(+)-menthofuran, a substance metabolically derived from R-(+)-pulegone that is both a flavoring agent at low concentrations and a hepatotoxin at larger ones, is evaluated by correlation-gas chromatography. A vapor pressure p/Pa = (36 ± 12) has been evaluated at T = 298.15 K, and a normal boiling temperature of T_b/K = 482.4 K is predicted. A boiling temperature of T_b/K = 374.3 compares with the literature value of T_b/K = 371.2 at reduced pressure, p/kPa = 2.93. The vaporization enthalpy of (56.5 ± 3.0) kJ·mol"−"1 compares to an estimated value of (57.8 ± 2.9) kJ·mol"−"1.

Effects of air vessel on water hammer in high-head pumping station

International Nuclear Information System (INIS)

Wang, L; Wang, F J; Zou, Z C; Li, X N; Zhang, J C

2013-01-01

Effects of air vessel on water hammer process in a pumping station with high-head were analyzed by using the characteristics method. The results show that the air vessel volume is the key parameter that determines the protective effect on water hammer pressure. The maximum pressure in the system declines with increasing air vessel volume. For a fixed volume of air vessel, the shape of air vessel and mounting style, such as horizontal or vertical mounting, have little effect on the water hammer. In order to obtain good protection effects, the position of air vessel should be close to the outlet of the pump. Generally, once the volume of air vessel is guaranteed, the water hammer of a entire pipeline is effectively controlled

Effects of air vessel on water hammer in high-head pumping station

Science.gov (United States)

Wang, L.; Wang, F. J.; Zou, Z. C.; Li, X. N.; Zhang, J. C.

2013-12-01

Effects of air vessel on water hammer process in a pumping station with high-head were analyzed by using the characteristics method. The results show that the air vessel volume is the key parameter that determines the protective effect on water hammer pressure. The maximum pressure in the system declines with increasing air vessel volume. For a fixed volume of air vessel, the shape of air vessel and mounting style, such as horizontal or vertical mounting, have little effect on the water hammer. In order to obtain good protection effects, the position of air vessel should be close to the outlet of the pump. Generally, once the volume of air vessel is guaranteed, the water hammer of a entire pipeline is effectively controlled.

The Enthalpy of Decomposition of Hydrogen Peroxide: A General Chemistry Calorimetry Experiment

Science.gov (United States)

Marzzacco, Charles J.

1999-11-01

A calorimetry experiment involving the catalytic decomposition of aqueous hydrogen peroxide is presented. The experiment is simple, inexpensive, and colorful. In its simplest form, it can be performed in less than one hour; therefore, it is quite suitable for high school labs, which often have time restrictions. The chemicals required are household or commercial 3% H2O2(aq) and 0.50 M Fe(NO3)3(aq). Styrofoam cup calorimeters and thermometers with a range from 20 to 50 oC are also required. Ideally, the thermometers should be precise to 0.01 oC. The temperature of the H2O2 solution is monitored before and after the Fe(NO3)3 catalyst is added. The addition of the catalyst results in a color change and the evolution of heat and bubbles of oxygen. At the conclusion of the reaction, the color of the reaction mixture returns to that of the original Fe(NO3)3 solution. The heat change for the reaction is determined from the temperature change, the specific heat of the solution, and the calorimeter constant. The experimental enthalpy change for the reaction is in excellent agreement with the literature value.

Correlation between experimental data of protonation of aromatic compounds at (+) atmospheric pressure photoionization and theoretically calculated enthalpies.

Science.gov (United States)

Ahmed, Arif; Lim, Dongwon; Choi, Cheol Ho; Kim, Sunghwan

2017-06-30

The theoretical enthalpy calculated from the overall protonation reaction (electron transfer plus hydrogen transfer) in positive-mode (+) atmospheric-pressure photoionization (APPI) was compared with experimental results for 49 aromatic compounds. A linear relationship was observed between the calculated ΔH and the relative abundance of the protonated peak. The parameter gives reasonable predictions for all the aromatic hydrocarbon compounds used in this study. A parameter is devised by combining experimental MS data and high-level theoretical calculations. A (+) APPI Q Exactive Orbitrap mass spectrometer was used to obtain MS data for each solution. B3LYP exchange-correlation functions with the standard 6-311+G(df,2p) basis set was used to perform density functional theory (DFT) calculations. All the molecules with ΔH toluene clusters produced protonated ions, regardless of the desolvation temperature. For molecules with ΔH >0, molecular ions were more abundant at typical APPI desolvation temperatures (300°C), while the protonated ions became comparable or dominant at higher temperatures (400°C). The toluene cluster size was an important factor when predicting the ionization behavior of aromatic hydrocarbon ions in (+) APPI. The data used in this study clearly show that the theoretically calculated reaction enthalpy (ΔH) of protonation with toluene dimers can be used to predict the protonation behavior of aromatic compounds. When compounds have a negative ΔH value, the types of ions generated for aromatic compounds could be very well predicted based on the ΔH value. The ΔH can explain overall protonation behavior of compounds with ΔH values >0. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Enthalpies of combustion and formation of {alpha}-D-glucoheptono-1,4-lactone and {alpha},{beta}-glucooctanoic-1,4-lactone

Energy Technology Data Exchange (ETDEWEB)

Amador, Patricia [Facultad de Ciencias Qui' micas, Benemerita Universidad Autonoma de Puebla, 14 Sur y Av. San Claudio, Col. Manuel, C.P. 72570 Puebla Pue (Mexico)], E-mail: cs000721@siu.buap.mx; Mata, Marian Y.; Flores, Henoc [Facultad de Ciencias Qui' micas, Benemerita Universidad Autonoma de Puebla, 14 Sur y Av. San Claudio, Col. Manuel, C.P. 72570 Puebla Pue (Mexico)

2008-05-15

The standard molar energies of combustion, {delta}{sub c}U{sub m}{sup 0}(cr,298.15K), of {alpha}-D-glucoheptono-1,4-lactone (GH) and {alpha},{beta}-glucooctanoic-1,4-lactone (GO) were obtained by micro-combustion calorimetry. The obtained values are -(2924.6 {+-} 2.3) kJ . mol{sup -1} and -(3459.5 {+-} 2.5) kJ . mol{sup -1}, respectively. From combustion energies, the standard molar enthalpies of formation in crystalline phase, {delta}{sub f}H{sub m}{sup 0}(cr,298.15K), for GH and GO were determined as -(1546.2 {+-} 2.5) kJ . mol{sup -1} and -(1690.6 {+-} 2.7) kJ . mol{sup -1}, respectively. Also it was found that when the hydroxyl group number increases in the aldonolactones their standard molar enthalpies of formation increase too.

Degradation kinetics of cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside during hot air and vacuum drying in mulberry (Morus alba L.) fruit: A comparative study based on solid food system.

Science.gov (United States)

Zhou, Mo; Chen, Qinqin; Bi, Jinfeng; Wang, Yixiu; Wu, Xinye

2017-08-15

The aim of this study is to ascertain the degradation kinetic of anthocyanin in dehydration process of solid food system. Mulberry fruit was treated by hot air and vacuum drying at 60 and 75°C. The contents of cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside were determined by using high performance liquid chromatography. Kinetic and thermodynamic parameters were calculated for analysing the degradation characteristics. Model fitting results showed monomeric anthocyanin degradations were followed the second-order kinetic. Vacuum drying presented high kinetic rate constants and low t 1/2 values. Thermodynamic parameters including the activation energy, enthalpy change and entropy change appeared significant differences between hot air and vacuum drying. Both heating techniques showed similar effects on polyphenol oxidase activities. These results indicate the anthocyanin degradation kinetic in solid food system is different from that in liquid and the oxygen can be regarded as a catalyst to accelerate the degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enthalpy-Driven RNA Folding: Single-Molecule Thermodynamics of Tetraloop–Receptor Tertiary Interaction†

Science.gov (United States)

Fiore, Julie L.; Kraemer, Benedikt; Koberling, Felix; Edmann, Rainer; Nesbitt, David J.

2010-01-01

RNA folding thermodynamics are crucial for structure prediction, which requires characterization of both enthalpic and entropic contributions of tertiary motifs to conformational stability. We explore the temperature dependence of RNA folding due to the ubiquitous GAAA tetraloop–receptor docking interaction, exploiting immobilized and freely diffusing single-molecule fluorescence resonance energy transfer (smFRET) methods. The equilibrium constant for intramolecular docking is obtained as a function of temperature (T = 21–47 °C), from which a van’t Hoff analysis yields the enthalpy (ΔH°) and entropy (ΔS°) of docking. Tetraloop–receptor docking is significantly exothermic and entropically unfavorable in 1 mM MgCl2 and 100 mM NaCl, with excellent agreement between immobilized (ΔH° = −17.4 ± 1.6 kcal/mol, and ΔS° = −56.2 ± 5.4 cal mol−1 K−1) and freely diffusing (ΔH° = −17.2 ± 1.6 kcal/mol, and ΔS° = −55.9 ± 5.2 cal mol−1 K−1) species. Kinetic heterogeneity in the tetraloop–receptor construct is unaffected over the temperature range investigated, indicating a large energy barrier for interconversion between the actively docking and nondocking subpopulations. Formation of the tetraloop–receptor interaction can account for ~60% of the ΔH° and ΔS° of P4–P6 domain folding in the Tetrahymena ribozyme, suggesting that it may act as a thermodynamic clamp for the domain. Comparison of the isolated tetraloop–receptor and other tertiary folding thermodynamics supports a theme that enthalpy- versus entropy-driven folding is determined by the number of hydrogen bonding and base stacking interactions. PMID:19186984

Optimization of the exploitation system of a low enthalpy geothermal aquifer with zones of different transmissivities and temperatures

International Nuclear Information System (INIS)

Tselepidou, K.; Katsifarakis, K.L.

2010-01-01

Market penetration of renewable energy sources, such as geothermal energy, could be promoted even by small cost reductions, achieved through improved development design. This paper deals with optimization of the exploitation system of a low enthalpy geothermal aquifer, by means of the method of genetic algorithms, which has been successfully used in similar problems of groundwater resources management. With respect to water flow, the aquifer consists of two zones of different transmissivities, while from the thermal point of view it may bear any number of zones with different temperatures. The optimization process comprises the annual pumping cost of the required flow and the amortization cost of the pipe network, which carries the hot water from the wells to a central water tank, situated at the border of the geothermal field. Results show that application of the proposed methodology allows better planning of low enthalpy geothermal heating systems, which may be crucial in cases of marginal financial viability. (author)

High-pressure, ambient temperature hydrogen storage in metal-organic frameworks and porous carbon

Science.gov (United States)

Beckner, Matthew; Dailly, Anne

2014-03-01

We investigated hydrogen storage in micro-porous adsorbents at ambient temperature and pressures up to 320 bar. We measured three benchmark adsorbents: two metal-organic frameworks, Cu3(1,3,5-benzenetricarboxylate)2 [Cu3(btc)2; HKUST-1] and Zn4O(1,3,5-benzenetribenzoate)2 [Zn4O(btb)2; MOF-177], and the activated carbon MSC-30. In this talk, we focus on adsorption enthalpy calculations using a single adsorption isotherm. We use the differential form of the Claussius-Clapeyron equation applied to the Dubinin-Astakhov adsorption model to calculate adsorption enthalpies. Calculation of the adsorption enthalpy in this way gives a temperature independent enthalpy of 5-7 kJ/mol at the lowest coverage for the three materials investigated. Additionally, we discuss the assumptions and corrections that must be made when calculating adsorption isotherms at high-pressure and adsorption enthalpies.

Improved simplified scheme of atom equivalents to calculate enthalpies of formation of alkyl radicals

International Nuclear Information System (INIS)

Castro, Eduardo A.

2002-01-01

An improved simplified method of atom equivalents is applied to the calculation of enthalpies of formation of several alkyl radicals. Some statistical mechanics and thermodynamic corrections are added to compare theoretical values with available experimental data. The estimation is quite satisfactory and the average error is similar to current experimental uncertainties, thus providing a direct and simple procedure for this sort of calculation when experimental results are unavailable or/and as an independent check when experimental data are in doubt. (Author) [es

Low-cost low-enthalpy geothermal heat for freshwater production: Innovative applications using thermal desalination processes

KAUST Repository

Bundschuh, Jochen; Ghaffour, NorEddine; Mahmoudi, Hacè ne; Goosen, Mattheus F A; Mushtaq, Shahbaz; Hoinkis, Jan

2015-01-01

The study is dedicated to exploring different types of low-cost low-enthalpy geothermal and their potential integration with conventional thermal-based water desalination and treatment technologies to deliver energy efficient, environmentally friendly solutions for water desalination and treatment, addressing global water crises. Our in-depth investigation through reviews of various low-enthalpy geothermal and conventional thermal-based technologies suggest that the geothermal option is superior to the solar option if low-cost geothermal heat is available because it provides a constant heat source in contrast to solar. Importantly, the stable heat source further allows up-scaling (> 1000 m3/day), which is not currently possible with solar. Solar-geothermal hybrid constellations may also be suitable in areas where both sources are available. The review also discovers that the innovative Membrane distillation (MD) process is very promising as it can be used for many different water compositions, salinity and temperature ranges. Either the geothermal water itself can be desalinated/treated or the geothermal heat can be used to heat feed water from other sources using heat exchangers. However, there are only few economic analyses for large-scale MD units and these are based on theoretical models using often uncertain assumptions resulting in a large variety of results.

Low-cost low-enthalpy geothermal heat for freshwater production: Innovative applications using thermal desalination processes

KAUST Repository

Bundschuh, Jochen

2015-03-01

The study is dedicated to exploring different types of low-cost low-enthalpy geothermal and their potential integration with conventional thermal-based water desalination and treatment technologies to deliver energy efficient, environmentally friendly solutions for water desalination and treatment, addressing global water crises. Our in-depth investigation through reviews of various low-enthalpy geothermal and conventional thermal-based technologies suggest that the geothermal option is superior to the solar option if low-cost geothermal heat is available because it provides a constant heat source in contrast to solar. Importantly, the stable heat source further allows up-scaling (> 1000 m3/day), which is not currently possible with solar. Solar-geothermal hybrid constellations may also be suitable in areas where both sources are available. The review also discovers that the innovative Membrane distillation (MD) process is very promising as it can be used for many different water compositions, salinity and temperature ranges. Either the geothermal water itself can be desalinated/treated or the geothermal heat can be used to heat feed water from other sources using heat exchangers. However, there are only few economic analyses for large-scale MD units and these are based on theoretical models using often uncertain assumptions resulting in a large variety of results.

The high efficiency steel filters for nuclear air cleaning

International Nuclear Information System (INIS)

Bergman, W.; Larsen, G.; Lopez, R.; Williams, K.; Violet, C.

1990-08-01

We have, in cooperation with industry, developed high-efficiency filters made from sintered stainless-steel fibers for use in several air-cleaning applications in the nuclear industry. These filters were developed to overcome the failure modes in present high-efficiency particulate air (HEPA) filters. HEPA filters are made from glass paper and glue, and they may fail when they get hot or wet and when they are overpressured. In developing our steel filters, we first evaluated the commercially available stainless-steel filter media made from sintered powder and sintered fiber. The sintered-fiber media performed much better than sintered-powder media, and the best media had the smallest fiber diameter. Using the best media, we then built prototype filters for venting compressed gases and evaluated them in our automated filter tester. 12 refs., 20 figs

Collecting performance of an evacuated tubular solar high-temperature air heater with concentric tube heat exchanger

International Nuclear Information System (INIS)

Wang, Ping-Yang; Li, Shuang-Fei; Liu, Zhen-Hua

2015-01-01

Highlights: • A novel evacuated tube solar high temperature air heater is designed. • The solar air heater system consists of 30 linked collecting units. • Every unit consisted of a evacuated tube, a simplified CPC and concentric tube. • The flow air is heated over temperature of 200 °C. - Abstract: A set of evacuated tube solar high temperature air heaters with simplified CPC (compound parabolic concentrator) and concentric tube heat exchanger is designed to provide flow air with a temperature of 150–230 °C for industrial production. The solar air heater system consists of 30 linked collecting units. Each unit includes a simplified CPC and an all-glass evacuated tube absorber with a concentric copper tube heat exchanger installed inside. A stainless steel mesh layer with high thermal conductivity is filled between the evacuated tube and the concentric copper tube. Air passes through each collecting unit, and its temperature increases progressively. An experimental investigation of the thermal performance of the air heater is performed, and the experimental results demonstrate the presented high-temperature solar air heater has excellent collecting performance and large output power, even in the winter. The measured thermal efficiency corresponding to the air temperature of 70 °C reaches 0.52. With the increase of air temperature, thermal efficiency reaches 0.35 at an air temperature of 150 °C, and 0.21 at an air temperature of 220 °C.

Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming.

Science.gov (United States)

Cronin, Timothy W; Tziperman, Eli

2015-09-15

High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback--consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state--slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼ 10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the "lapse rate feedback" in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates.

Energy and enthalpy distribution functions for a few physical systems.

Science.gov (United States)

Wu, K L; Wei, J H; Lai, S K; Okabe, Y

2007-08-02

The present work is devoted to extracting the energy or enthalpy distribution function of a physical system from the moments of the distribution using the maximum entropy method. This distribution theory has the salient traits that it utilizes only the experimental thermodynamic data. The calculated distribution functions provide invaluable insight into the state or phase behavior of the physical systems under study. As concrete evidence, we demonstrate the elegance of the distribution theory by studying first a test case of a two-dimensional six-state Potts model for which simulation results are available for comparison, then the biphasic behavior of the binary alloy Na-K whose excess heat capacity, experimentally observed to fall in a narrow temperature range, has yet to be clarified theoretically, and finally, the thermally induced state behavior of a collection of 16 proteins.

Water as a solute in aprotic dipolar solvents. 2. D2O-H2O solute isotope effects on the enthalpy of water dissolution in nitromethane, acetonitrile and propylene carbonate at 298.15 K

International Nuclear Information System (INIS)

Ivanov, Evgeniy V.; Smirnov, Valeriy I.

2010-01-01

The enthalpies of solution of ordinary (H 2 O) and heavy (D 2 O) water in nitromethane (NM), acetonitrile (ACN) and propylene carbonate (PC) were measured calorimetrically at 298.15 K. Standard (at the infinite dilution) enthalpies of solution and solvation, along with D 2 O-H 2 O solute isotope effects on the quantities in question, were calculated. The enthalpies of solution of water H/D isotopologues were found to be positive by sign and substantially increasing in magnitude on going from ACN and PC to NM, whereas the corresponding positive solute H/D isotope effect changes in a consequence: NM > ACN > PC. The qualitative interrelations between the enthalpy-isotopic effect of dissolution (solvation) of water and the electron-accepting/donating ability of aprotic dipolar solvent (within a series considered) were found.

PTV analysis of the entrained air into the diesel spray at high-pressure injection

Science.gov (United States)

Toda, Naoki; Yamashita, Hayato; Mashida, Makoto

2014-08-01

In order to clarify the effect of high-pressure injection on soot reduction in terms of the air entrainment into spray, the air flow surrounding the spray and set-off length indicating the distance from the nozzle tip to the flame region in diffusion diesel combustion were investigated using 300MPa injection of a multi-hole injector. The measurement of the air entrainment flow was carried out at non-evaporating condition using consecutive PTV (particle tracking velocimetry) method with a high-speed camera and a high-frequency pulse YAG laser. The set-off length was measured at highpressure and high-temperature using the combustion bomb of constant volume and optical system of shadow graph method. And the amount of air entrainment into spray until reaching set-off length in diffusion combustion was studied as a factor of soot formation.

Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

Science.gov (United States)

Fan, Chao; Pashley, Richard M.

2016-01-01

The enthalpy of vaporization (?H[subscript vap]) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a…

Air filtration and indoor air quality

DEFF Research Database (Denmark)

Bekö, Gabriel

2006-01-01

Demands for better indoor air quality are increasing, since we spend most of our time indoors and we are more and more aware of indoor air pollution. Field studies in different parts of the world have documented that high percentage of occupants in many offices and buildings find the indoor air...... decent ventilation and air cleaning/air filtration, high indoor air quality cannot be accomplished. The need for effective air filtration has increased with increasing evidence on the hazardous effects of fine particles. Moreover, the air contains gaseous pollutants, removal of which requires various air...... cleaning techniques. Supply air filter is one of the key components in the ventilation system. Studies have shown that used ventilation filters themselves can be a significant source of indoor air pollution with consequent impact on perceived air quality, sick building syndrome symptoms and performance...

Assessment of semiempirical enthalpy of formation in solution as an effective energy function to discriminate native-like structures in protein decoy sets.

Science.gov (United States)

Urquiza-Carvalho, Gabriel Aires; Fragoso, Wallace Duarte; Rocha, Gerd Bruno

2016-08-05

In this work, we tested the PM6, PM6-DH+, PM6-D3, and PM7 enthalpies of formation in aqueous solution as scoring functions across 33 decoy sets to discriminate native structures or good models in a decoy set. In each set these semiempirical quantum chemistry methods were compared according to enthalpic and geometric criteria. Enthalpically, we compared the methods according to how much lower was the enthalpy of each native, when compared with the mean enthalpy of its set. Geometrically, we compared the methods according to the fraction of native contacts (Q), which is a measure of geometric closeness between an arbitrary structure and the native. For each set and method, the Q of the best decoy was compared with the Q0 , which is the Q of the decoy closest to the native in the set. It was shown that the PM7 method is able to assign larger energy differences between the native structure and the decoys in a set, arguably because of a better description of dispersion interactions, however PM6-DH+ was slightly better than the rest at selecting geometrically good models in the absence of a native structure in the set. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Air Quality Standards for Particulate Matter (PM) at high altitude cities

International Nuclear Information System (INIS)

Bravo Alvarez, H.; Sosa Echeverria, R.; Sanchez Alvarez, P.; Krupa, S.