高温高压下湿空气的焓和熵计算

本文以湿空气透平和压缩空气储能系统中的工质-湿空气为研究对象,运用所提出的一个适合计算高温高压湿空气热力学性质的对应态维里方程,对湿空气的偏差焓和偏差熵进行了计算.在湿度0≤ W≤1 kg/kg(A),温度小于573.15 K,压力小于5 MPa时,与ASHRAE用的多项式维里方程计算得到的偏差焓和偏差熵进行了比较,误差很小.用这个对应态维里方程外推计算了温度和压力分别达到600 K和15 MPa的湿空气焓和熵.计算结果表明对湿空气而言压力和湿度越大,偏差焓和偏差熵越大;温度越高,偏差焓和偏差熵越小.     

Global Warming by Geothermal Heat from Fracking: Energy Industry’s Enthalpy Footprints

Hypothetical dry adiabatic lapse rate (DALR) air expansion processes in atmosphere climate models that predict global warming cannot be the causal explanation of the experimentally observed mean lapse rate (approx.−6.5 K/km) in the troposphere. The DALR hypothesis violates the 2nd law of thermodynamics. A corollary of the heat balance revision of climate model predictions is that increasing the atmospheric concentration of a weak molecular transducer, CO₂, could only have a net cooling effect, if any, on the biosphere interface temperatures between the lithosphere and atmosphere. The greenhouse-gas hypothesis, moreover, does not withstand scientific scrutiny against the experimental data. The global map of temperature difference contours is heterogeneous with various hotspots localized within specific land areas. There are regional patches of significant increases in time-average temperature differences, (∆<T>) = 3 K+, in a ring around the arctic circle, with similar hotspots in Brazil, South Africa and Madagascar, a 2–3 K band across central Australia, SE Europe centred in Poland, southern China and the Philippines. These global-warming map hotspots coincide with the locations of the most intensive fracking operational regions of the shale gas industry. Regional global warming is caused by an increase in geothermal conductivity following hydraulic fracture operations. The mean lapse rate (d<T>/dz)_z at the surface of the lithosphere will decrease slightly in the regions where these operations have enhanced heat transfer. Geothermal heat from induced seismic activity has caused an irreversible increase in enthalpy (H) input into the overall energy balance at these locations. Investigating global warming further, we report the energy industry’s enthalpy outputs from the heat generated by all fuel consumption. We also calculate a global electricity usage enthalpy output. The global warming index, <∆T-biosphere> since 1950, presently +0.875 K, first became non-zero in the early 1970’s around the same time as natural gas usage began and has increased linearly by 0.0175 K/year ever since. Le Chatelier’s principle, applied to the dissipation processes of the biosphere’s ΔH-contours and [CO₂] concentrations, helps to explain the global warming statistics.     

Synthesis and properties of novel energetic (cyano-NNO-azoxy)furazans

Three novel energetic furazans with a cyano-NNO-azoxy group were synthesized using cyanamide and 2,2,2-tri- fluoro-N-(4-nitrosofurazan-3-yl)acetamide as the starting compounds. (Cyano-NNO-azoxy)furazans obtained display high experimental enthalpies of formation (+742 to +1073 kcal kg⁻¹), good thermal stability (Tonset = 193–222 °C) and moderate mechanical sensitivity. These compounds may be of interest as energetic fillers in solid fuels for ramjet engines and in solid composite propellants.     

Molecular structure of 6-cyclopropyl-1,5-diazabicyclo[3.1.0]hexane: gas phase electron diffraction and theoretical study

The molecular structure and conformational composition of 6-cyclopropyl-1,5-diazabicyclo[3.1.0]hexane were determined by gas phase electron diffraction and quantum chemical calculations. The gas phase electron diffraction data were well reproduced for the mixture of two conformers with anti-boat and gauche-boat mutual ring orientation having 15 and 85% relative abundance, respectively. The standard enthalpy of formation of substance under study was calculated using atomization reactions, yielding value of 307.9 ± 3.3 kJ mol^-1 in gas phase.     

The Gaussian G4 enthalpy of formation of propargylamine and propargyloxy derivatives of triazido-s-triazine

Enthalpies of formation in gas phase of three series of energetic derivatives of triazido-s-triazine containing propynyloxy, propynylamine and methylpropynylamine groups were calculated using G4 method. Contributions of each group to the enthalpy of formation of the discussed compounds were estimated in order to apply the increment method for quick estimation of this thermodynamic parameter for substituted s-triazines.     

Interactions between small molecules of biological interest. Excess enthalpies of ternary solutions of oligomers of glycine and isomeric pentoses in water at 25°C

Enthalpies of dilution of ternary aqueous solutions containing an oligomer of glycine (glycyl-glycine and glycyl-glycyl-glycine) and one of the pentoses: L-arabinose, D-lyxose, D-ribose, D-xylose, were experimentally determined. The cross coefficients of the virial expansion of the excess enthalpies were evaluated and compared with those relative to the solutions containing the same pentoses and other structure breaking solutes (glycine, urea, thiourea, biuret). The trend of these coefficients seems to depend very little on the particular pentose, with the exception of a pronounced minimum for D-ribose. Also, the cross coefficients for each of the four pentoses studied do not seem to depend on the nature of the oligomers of glycine. The results were interpreted in terms of a prevailing release of water from the hydration cosphere of the sugars. These last substances show, once more, a behavior in water more complex than that commonly thought.     

Excess enthalpy and entropy of aqueous tetramethylguanidinium perchlorate and chloride and tetramethylammonium nitrate

Heats of dilution have been measured for aqueous solutions of tetramethylguanidinium perchlorate and chloride and for tetramethylammonium nitrate at 25°C. Excess enthalpies have been calculated and combined with excess free energy data which were previously published to yield excess entropy. These results furnish further evidence for the association of the tetramethylguanidinium salts in aqueous solutions.     

Paradigms and Paradoxes: The Solubility of AgCl in Water: Some Thermochemical Issues of Aqueous Ag+ Ion

It is well established in the pedagogical literature that AgCl is insoluble in water while NaCl and KCl are soluble: applications of this difference are made in elementary studies of both qualitative and quantitative analysis. What is usually left unsaid, however, is why AgCl is so much less soluble than NaCl or KCl. This brief note addresses this issue in terms of the thermochemistry of these three metal chlorides and constituent ions as found in their solid salts, aqueous solutions and gaseous diatomic molecules.     

Adsorption studies of acetic acid dimers on activated charcoal from organic solvents

Acetic acid exists as dimers in organic solvents like benzene, toluene and xylene. Adsorption of dimeric acetic acid on activated charcoal (AC) at various temperatures from benzene, toluene and xylene solutions have been studied. The system obeys Langmuir isotherm, thus signifying a monolayer adsorption of dimers. Corrections on AC-solvent pore volume fillings, molecular cross sectional surface area of acetic acid dimers, the adsorption equilibrium constants, the free energy change and the enthalpy change values are computed at different temperatures for the three solvents. The adsorption process has been found to be physisorption type. The FTIR measurements show that the adsorbed acetic acid dimer seems to retain the cyclic structure against the open chain non-cyclic structure.