Influence Of Thermodynamic Parameters Research Articles

Thermodynamic features of the regenerative system of direct fired sCO2 power cycles with oxygen combustion of methane

The article presents an analysis of the thermodynamic features of the operation of a regenerative system of sCO2 power cycles. The cycle with a two-stage pressure increase configuration is taken as a basis for calculation. The supply of energy to the working fluid is provided by the operation of the regenerative system and by oxy-fuel combustion. Methane is used as fuel. The issues of theoretically achievable heating temperatures of the working fluid in the cycle regenerative system are considered. The influence of thermodynamic parameters on the heat fluxes of the regenerative system is estimated. For the first time, an assessment was made of the relative and absolute contribution of water vapor, formed during fuel combustion, to heat flows. This study makes it possible to establish the physical quantities pressure, temperature and heat fluxes, which are necessary for further design calculations of heat exchangers to be used in industrial installations. As a result of multi-variant calculations of the cycle (when varying the temperature at the turbine inlet in the range of 500–1500 °C and pressure - from 100 to 400 bar), it was found that the temperature of the working fluid supply to the combustion chamber can be taken at the level of 2/3 of the temperature at its outlet. At operating temperatures of the working fluid at the level of 1000–1200 °C, the contribution of water vapor to regenerative heating will be 3–17%, depending on their mass content. The total theoretical heat flow to the cycle regenerative system will be 800–1000 kJ/kg CO2. The energy supply to the working fluid due to fuel combustion does not exceed 50% of the total energy supplied in the operating temperature and pressure ranges.

ENERGY-SAVING ADAPTATION OF THE VIBRATION-IMPACT BUCKET OF THE MANIPULATOR TO THE VARIABLE CHARACTERISTICS OF THE WORKING ENVIRONMENT

The paper study of the vibrating bucket of the manipulator as an excavator or tunnelling shield, with energy-saving adaptation to the aspects of the working environment for use in the construction and mining industry. The use of buckets and vibro-impact devices with automated operation allows a reduction of energy consumption for the destruction of rocks and hard soils with adaptation to their properties. The article proposes an algorithm for optimal control of the vibro-impact bucket element - a vibro-impact device using restrictions on the cutting resistance force and impact energy. The range of functioning of the vibro-impact device is determined. The optimal area of switching on the device is established, depending on the variable aspects of the working environment. 
 The integral characteristic, such as the cutting resistance force of the soil, were used. It finds that this characteristic depends on the angle of rotation of the manipulator's bucket and the soil density's attribute by the number of impacts of the DorNDI impactor. The influence of thermodynamic parameters on the impact energy during the functioning of the vibration impact device in a real environment is observed by considering the polytope index of the gas compression process in the pneumatic accumulator.
 The work establishes the critical level of the force of static cutting of soils by an excavator of the IV size group for Ukrainian production and the criterion for the transition of the cutting process from static to dynamic mode depending on the variable characteristics of the working environment. The energy characteristics of the adaptive vibration-impact bucket of the manipulator are given. Introducing the vibro-impact bucket into the industrial production of Ukraine is recommended.

METHOD FOR DETERMINING THE SEQUENCE OF REACTIONS TO PREDICT THE CONSEQUENCES OF TECHNOGENIC POLLUTION

To predict the negative consequences of man-made pollution with harmful substances, a method for determining possible ways of chemical reactions taking into account the chemical and thermodynamic properties of a given set of components, the theoretical foundations of chemical stoichiometry and thermodynamics, patterns of influence of thermodynamic parameters on the direction of chemical reactions. In this regard, chemical objects were presented in the form of multidimensional vectors, taking into account thermodynamic parameters, for the calculation of which used the methods of chemical thermodynamics. The generation of chemical reactions was carried out using the methods of mathematical statistics and combinatorics, and to determine the sequences of chemical reactions, the methods of graph theory. It is proposed to write a chemical compound as the sum of basis vectors, which allowed to represent compounds and interactions between them in n-dimensional space and to determine possible chemical interactions with the help of the main principles of work with integer vector space. Three conditions for the possibility of chemical interaction by this method are clarified and the values of enthalpy and Gibbs energy of each reaction are introduced, which are determined by the values of the corresponding potentials for each of the compounds. For the convenience of the image and further calculations, the element-enthalpy and element-gibs spaces were used separately. An algorithm for this method is created and tested, features for different boundary conditions of its use are studied, its efficiency on real chemical reaction systems is checked. An algorithm for determining the possibilities of chemical reactions in multicomponent systems to determine their man-made load on the environment is proposed.

Evaluation of the diffusive tortuosity by analyzing the molecular thermal motion displacement

Molecular thermal motion is a very meaningful process. Plenty of useful information can be extracted from molecular travel displacement. In this paper, a kerogen model with a random and complex pore network is constructed. Based on the molecular thermal motion process, the diffusive tortuosity caused by the confined pore network is investigated by the molecular dynamics simulations. The influence of thermodynamic parameters on the diffusive tortuosity is carefully studied. The results showed that the diffusive tortuosity ranges from 1.57 to 2.70 depending on the pressure. However, with the variation of temperature and porosity, the diffusive tortuosity has a little change, mainly distributed from 1.79 to 1.95. The thermal diffusive tortuosity of the complex pore network is successfully calculated by analyzing molecular thermal motion property.

Use of alternative energy sources to improve the efficiency of natural gas hydrate technology for gas offshore deposits transportation

This work has become possible due to financial and organizational support within the frames of the state budget research project under the auspices of the Ministry of Education and Science of Ukraine “Application of gas hydrate technology in the development of traditionaland gas hydrate gas deposits” No.0113U00857, “Research of influence of thermodynamic parameters of phase transitions in systems with gas hydrates on the efficiency of gas hydrate technology” No.0115U002420.

Selectivity and CO2 capture efficiency in CO2-N2 clathrate hydrates investigated by in-situ Raman spectroscopy

Thermodynamic measurements and Raman spectroscopy are performed to investigate the structure, selectivity and capture efficiency in mixed gas hydrates containing CO2 and N2. Clathrates forming conditions and dissociation pressures are provided between 270.5 K and 278.3 K (−2.5 °C and 5.3 °C). Specific CO2 Raman signatures show structure sII to be thermodynamically stable at feed gas composition of 1% and kinetically favored at ∼2%. Structure sI is stable at feed gas CO2 ranging from ∼2% up to 70%. Our Raman quantitative analysis demonstrates the removal of CO2 from a typical flue gas mixture (1–20% CO2) and from samples of 47% and 70% CO2 during hydrate crystallization. For the first time, quantitative bulk guest compositions in hydrates are directly obtained by Raman using relative cross sections of the guests’ (CO2 and N2) vibrational modes. The equilibrium data thereby generated satisfactorily compare with predictions based on thermodynamic models (CSMGem) and thus remove any ambiguity from previous literature data. It appears that CO2 molecules preferentially occupy sI large cages (51262) for a CO2 feed gas concentration in the range of 2–20% (i.e. ∼1–16% equilibrium gas compositions), whereas CO2 molecules severely compete with N2 to fill sI small cages (512) at equilibrium CO2 concentrations greater than 30%. As a consequence, the derived selectivity shows a significant decrease from ∼7.2 (at 20% CO2) to ∼3.8 for CO2-rich feed gas compositions (i.e. above 20%). In addition, the selectivity is reduced in structure sII formed at 1% CO2 feed gas composition. Then, the influence of thermodynamic parameters on hydrate selectivity and recovery fraction is described qualitatively at typical CO2 flue gas concentrations found in conventional power plants.

Effect of fuels on the autocombustion reaction synthesis of nanocrystalline gadolinium sesquioxide (Gd2O3) powder: evaluation of structure, morphology, optical and electrical properties

Nanocrystalline gadolinium sesquioxide (Gd2O3) powders were prepared by the autocombustion technique using three different fuels (citric acid, urea, and oxalyl dihydrazide). The influence of thermodynamic parameters and nature of fuel on structural transformation, phase formation, morphological characteristics, optical and electrical distinctive were comparatively studied for the first time. Gd2O3 prepared using citric acid and urea were well crystalline with cubic structure, whereas oxalyldihydrazide fuel resulted mixed cubic and monoclinic phase. Obtained structural information were further analyzed by computation of reflection intensities from a structural model, often referred to as the Rietveld method. The formation and purity of Gd2O3 nanoparticles were further confirmed by from the Fourier transform infrared (FTIR) spectra. Surface morphology of Gd2O3 favored the formation of large aggregates, instead of loose and porous particles as observed for citric acid and oxalyl dihydrazide. Optical absorption measurements were recorded in the UV-vis-NIR wavelength region and the optical band gap variations with fuel type were discussed. Electrical conductivity mechanisms in the prepared materials were identified using band gap, nearest neighbor hopping, and variable range hopping models. The citric acid- and urea-derived powders only have optical band and nearest neighbor hopping conduction. Magnetization measurements were performed at 300 K, the saturation magnetization, coercivity, and remanence of each sample was calculated and they showed paramagnetism. Photoluminescence spectra of Gd2O3 nanoparticles have been studied and observed spectroscopic features have been correlated with various transitions of Gd3+ ions.

Calculation of the equilibrium state and thermodynamic characteristics of plasma-forming gases and the plasma–“particle” system

The composition and thermodynamic characteristics of plasma-forming gases (Ar, N2, H2, and mixtures Ar + N2 and Ar + H2) depending on temperature are investigated using thermodynamic modeling. The equilibrium composition and thermodynamic properties of the plasma–“particle” system are modeled. Pure metals, oxides, technical powders, and powder mixtures were considered as the particle. The influence of power materials TiO2, Al2O3, and Fe3O4 on the variation in the plasma enthalpy is investigated. It is shown that computer modeling of the influence of thermodynamic parameters of the heterogeneous plasma jet makes it possible to optimize the modes of the plasma deposition and formation of plasma coatings. The proposed approach substantially shortens the time necessary to develop the formation technologies of coatings with the specified functional properties such as protective, antiwear, etc.

Experimental investigation of liquid-vapor ejector with conical mixing chamber

The article is devoted the design of working process of liquid-vapor ejector of a vacuum unit with conical mixing chamber, working on principle of stream thermocompression, research of influence of thermodynamic parameters and descriptions of active and passive streams on the process of mixing with the purpose of achievement of most vacuum unit efficiency. The main content of the article is study the nature of passive mixing flows with different thermodynamic properties on the geometric parameters of the mixing chamber. Experimental study of liquid-vapor ejector with conical mixing chamber on a transparent model allowed to confirm the mechanism of the working process at pressures below atmospheric pressure, namely the boiling of metastable superheated liquid, characterized by the presence of three critical sections expiry of expanding the channels to the definition section of flow separation from the walls of the channel and its position relative to the nozzle exit of active flow. Also the nature of the mixing process in the chambers of conical shape is investigated. It allows establishing maximum efficiency by optimizing the flow of liquid-vapor ejector with conical mixing chamber. The estimation of the appropriateness of units on the basis of LVE in vacuum systems through a comparative exergy analysis of basic and alternative schemes offered by the method of J. Tsatsaronis.

Performance analysis of a combined system for cold and power

This paper presents a theoretical study of a combined thermal system, which combines the Rankine cycle and the ejector refrigeration cycle. This combined cycle produces power and refrigeration simultaneously. The thermal system could use low temperature heat sources. A simulation was carried out to evaluate the cycle performance using several working fluids as R123, R141b, R245fa, R601a and R600a. A one-dimensional mathematical model of the ejector was developed using the equations governing the flow and thermodynamics based on the constant area ejector flow model. The ejector is studied in optimal operating regime. The influence of thermodynamic parameters on system performance is studied. The results show that the condenser temperature, the evaporation temperature, the extraction ratio, the fluid nature and the generating temperature have significant effects on the system performances (the coefficient of performance of the combined cycle and the entrainment ratio of the ejector).

Mutational Effect of Structural Parameters on Coiled-Coil Stability of Proteins

Understanding the parameters that influence the melting temperature of coiled-coils (CC) and their stability is very important. We have analyzed 45 CC mutants of DNA binding protein, electron transport protein, hydrolase, oxidoreductase, and transcription factors. Many mutants have been observed at Tm = 40 °C–60 °C with ΔS = 9–11 kcal/°C mol, ΔG = −400 to −450 kcal/mol, and Keq = 0.98–1.03. The multiple regression analysis of Tm reveals that influences of thermodynamic parameters are strong (R = 0.97); chemical parameters are moderate (R = 0.63); and the geometrical parameters are negligible (R = 0.19). The combination of all these three parameters exhibits a little higher influence on Tm (R = 0.98). From the analysis, it has been concluded that the thermodynamic parameters alone are very important in stability studies on protein coil mutants. Besides, the derived regression model would have been useful for the reliable prediction of the melting temperature of coil mutants.

3-Pentanone LIF at elevated temperatures and pressures: measurements and modeling

The objective of this study is to investigate 3-pentanone fluorescence experiments in a constant volume vessel at high temperature and high pressure to underline the influent parameters in conditions close to those encountered in internal combustion engines. To obtain quantitative analysis, measured fluorescence signals must be corrected by considering the influence of preponderant parameters such as temperature, pressure and gas composition. Quantitative dependences of fluorescence on thermodynamic parameters are measured and compared with the predictions of a photophysical model, which combines the effects of temperature, pressure, excitation wavelength on fluorescence quantum yield. The increase of 3-pentanone fluorescence with pressure is due to the vibrational relaxation of energy levels. The fluorescence decreases with increasing temperature, except at low temperature where the fluorescence increase is due to an activation of intersystem crossing between triplet toward singlet levels. The influences of thermodynamic parameters are based on an increase of the non-radiative decay rate with the vibrational energy level of excited electronic state and the important collisions to remove the excess vibrational energy. Experimental and calculated results show a satisfactory agreement.

IPRP (Integrated-Pyrolysis Regenerated Plant): Gas turbine and externally heated rotary-kiln pyrolysis as a biomass and waste energy conversion system. Influence of thermodynamic parameters

Sustainability is one of the main goals to achieve in order to guarantee a future for future generations and requires, among other issues, the recourse to renewable energy sources and the minimization of waste production. These two issues are contemporarily achieved when converting waste and residual biomass into energy. This paper presents an innovative concept for energy conversion of the abovementioned residual fuels; it combines a rotary-kiln pyrolyser, where the residual energy sources are converted into a medium lower heating value (LHV) syngas, with a gas turbine that produces energy, and also provides waste heat to maintain the endothermic pyrolysis reaction. Byproducts of the reaction include char and tars that have an interesting energetic content and may also be used to provide supplementary heat to the process. Through software modelling the paper analyses the influence on performance of main thermodynamic parameters, showing the possibilities of reaching an optimum for different working conditions that are characteristic of different sizes of gas turbines. This is interesting both for medium-to-big size power plants, where the IPRP efficiency is comparable to a grate-based incinerator, but at lower investment costs, and in the micro-small scale, for which there is no available technology on the market.

Langmuir−Blodgett Film Organization Resulting from Asymmetrical or Partial Types of Monolayer Transfer: Comparison for Amphiphiles of Different Geometrical Shapes

The problem of whether the Langmuir-Blodgett (LB) technique is capable of producing ordered films of molecular arrangement different from a bulk phase one is addressed for amphiphiles of rod-like and disk-like geometrical shapes. Low-angle X-ray diffraction and morphological characterization are performed for LB films deposited by means of asymmetrical and partial types of monolayer transfer. The influence of thermodynamic parameters, steric molecular peculiarities, and intermolecular interactions on the efficiency and mechanism of the monolayer transfer is considered. Molecular overturning to a multibilayer (“bulk”) arrangement is established for the case of Z-type (one-direction up-stroke) deposition of the rod-like amphiphile, and a crystalline body-centered orthorhombic (“bulk”) structure for the case of partial (“mixed” XY type) LB transfer of the diskotic films. Symmetrical Y-type deposition is found to result in almost defect-free multilayers over large scales of film surface examination. For both kinds of amphiphiles studied, the asymmetrical and partial types of LB transfer are less effective, as compared to the Y-type, in inducing periodic thin film organizations, distinct from the bulk phase structures of the amphiphiles.

Thermodynamic features of garnet film growth by chemical transport in a closed system

The results of experiments on synthesis of monocrystal garnet films by chemical transport in a close system are reported. The influence of thermodynamic parameters on the chemical transport of YIG films was studied. It was found that the conditions T=1220−1280° C, δT=5−15° C, s=0.5−1mm, P HCl 3 : P HCl=7−12 (M= Fe, Ga) are optimal for the growth of Y 3− y Gd y Ga x Fe 5− x O 12 ( y = 0, 0.4; x = 0, 0.9−1.5) films. Monocrystal YIG films and single or double layer Y 2.6Gd 0.4Ga x Fe 5− x O 12 ( x=0.9−1.5) films were synthesized.