Search for: enthalpy
Total 35 records
Excess enthalpy data in some binary systems containing non-electrolyte solutions and their correlations at 298.15 K - Part II, Article Physics and Chemistry of Liquids ; Volume 40, Issue 3 , 2002 , Pages 225-240 ; 00319104 (ISSN) ; Parsa, J. B ; Soltanieh, M ; Sharif University of Technology
Excess enthalpy data measured at 298.15 K were collected from the literature. The data contains 48 binary systems (812 data points). The experimental data were correlated by the Redlich-Kister equation. In this research work the following thermodynamics models were also tested, Wilson, NRTL models and their parameters were calculated. A modified NRTL with composition-dependent (α12) parameter were also proposed. The correlation of excess enthalpy data in the systems using this model provides good results
Comparison of a new numerical model with the published data for enthalpy wheel and air dehumidifier: Study of optimum speed and wall effects, Article 2005 ASME Summer Heat Transfer Conference, HT 2005, San Francisco, CA, 17 July 2005 through 22 July 2005 ; Volume 4 , 2005 , Pages 331-339 ; 0791847314 (ISBN); 9780791847312 (ISBN) ; Van Paassen, D ; Saidi, M. H ; Sharif University of Technology
In this paper the analytical and simulation modelling of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out. Using the numerical method, the performance of adiabatic rotary dehumidifier and enthalpy wheels are parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. A comparison of solutions for different conditions used in the air dehumidifier has been investigated according to the previously published studies. These approaches have been developed for enthalpy wheels. The simulated results have been compared with the published actual values of an experimental work. This...
QSPR studies for predicting gas to acetone and gas to acetonitrile solvation enthalpies using support vector machine, Article Journal of Molecular Liquids ; Volume 175 , 2012 , Pages 24-32 ; 01677322 (ISSN) ; Golmohammadi, H ; Dashtbozorgi, Z ; Acree Jr., W. E ; Sharif Unviersity of Technology
Quantitative structure-properties relationship (QSPR) has been applied to modelling and predicting the gas to acetone and gas to acetonitrile solvation enthalpies (ΔH Solv) of organic compounds using partial least squares (PLS), artificial neural network (ANN) and support vector machine (SVM) techniques. Two different datasets were assessed. The first one contained a set of gas to acetone enthalpy of solvation data of 68 different organic compounds while the second one included a total of 69 experimental data points for the enthalpy of solvation in acetonitrile. Genetic algorithm (GA) was used to search the descriptor space and select the descriptors responsible for property. After the...
A quantitative structure-property relationship for determination of enthalpy of fusion of pure compounds, Article Journal of Thermal Analysis and Calorimetry ; Volume 109, Issue 1 , June , 2012 , Pages 501-506 ; 13886150 (ISSN) ; Gohar, M. R. S ; Vayeghan, M. G ; Sharif University of Technology
In this study, the quantitative structure-property relationship method is applied to predict the enthalpy of fusion of pure chemical compounds at their normal melting point. A genetic algorithm-based multivariate linear regression is used to select the most statistically effective molecular descriptors for evaluating this property. To propose a comprehensive and predictive model, 3,846 pure chemical compounds are investigated. The root mean square of error and the average absolute deviation of the model are equal to 2.57 kJ/mol and 9.7%
Prediction of standard enthalpy of combustion of pure compounds using a very accurate group-contribution-based method, Article Energy and Fuels ; Volume 25, Issue 6 , April , 2011 , Pages 2651-2654 ; 08870624 (ISSN) ; Mirkhani, S. A ; Tofangchi Mahyari, A. R ; Sharif University of Technology
The artificial neural network-group contribution (ANN-GC) method is applied to estimate the standard enthalpy of combustion of pure chemical compounds. A total of 4590 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 99, root mean square error of 12.57 kJ/mol, and average absolute deviation lower than 0.16% for the estimated properties from existing experimental values
The effect of chemical composition on enthalpy and entropy changes of martensitic transformations in binary NiTi shape memory alloys, Article Journal of Alloys and Compounds ; Volume 487, Issue 1-2 , 2009 , Pages 363-366 ; 09258388 (ISSN) ; Amin Ahmadi, B ; Sharif University of Technology
In the present research work the binary NiTi alloys with various compositions in the range of 50.3-51 at.% Ni were used. Samples have been annealed at 850 °C for 15 min and then quenched in water. In order to characterize transformation temperatures and enthalpy changes of the forward and the reverse martensitic transformation, Differential Scanning Calorimetric (DSC) experiments were performed. The enthalpy and entropy changes as a function of Ni atomic content have been thermodynamically investigated. Results show that enthalpy and entropy changes of martensitic transformation decrease when Ni atomic content increases. The variation of enthalpy and entropy of martensitic transformation...
M.Sc. Thesis Sharif University of Technology ; Gobal, Ferydon
Generally, predicting the adsorption and Catalytic characteristics of the solids base on the primary principles is impossible; this is only possible for small molecules and single crystal surfaces. On the other hand, phenomenological approaches, which are based on experimental data, are efficient approaches in many cases. The best predictions and designs are done by those who have an extensive information “resources” about the “Reactive Substances- Catalytic-conditions” and are able to “analyze” the data based on the “chemical physical Models”. A Neural network is an extremely simplified model of the human brain that predicts a complex characteristic(s) from a series of primary...
Article 2006 ASME 51st Turbo Expo, Barcelona, 6 May 2006 through 11 May 2006 ; Volume 4 , 2006 , Pages 537-546 ; 0791842398 (ISBN); 9780791842393 (ISBN) ; Khaledi, H ; Hajilouy Benisi, A ; Sharif University of Technology
Advanced gas turbine cycles use advanced blade cooling technologies to reach high turbine inlet temperature. Accurate modeling and optimization of these cycles depend on blade cooling model. In this study, different models have been used to simulate gas turbine performance. The first model is the continuous model and the second is stage-by-stage model with alternative methods for calculating coolant, stagnation pressure loss and SPR. Variation of specific heat and enthalpy with temperature are included in both models. The composition of gas stream in turbine is changed step by step due to air cooling. These models are validated by two case study gas turbine results, which show good agreement...
Article Applied Surface Science ; Volume 258, Issue 7 , 2012 , Pages 2226-2230 ; 01694332 (ISSN) ; Parsafar, G. A ; Bayat, Y ; Sharif University of Technology
The interaction potential energy and heat of sublimation of nanoparticles of HMX crystal polymorphs are studied by using molecular dynamics methods with a previously developed force field [Bedrov, et al., J. Comput.-Aided Mol. Des. 8 (2001) 77]. Molecular dynamics simulations of nanoparticles with 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 molecules of HMX are carried out at 300 K. The intermolecular, intramolecular and total interaction energies per mole for the nanoparticles are calculated at 300 K. Then, we have calculated sublimation enthalpy of HMX crystal polymorphs with different sizes. For the all sizes, the β-HMX is found to be the most stable phase, due to having the least total...
Article Journal of Physical Organic Chemistry ; 2017 ; 08943230 (ISSN) ; Kassaee, M. Z ; Fattahi, A ; Sharif University of Technology
John Wiley and Sons Ltd 2017
Anticancer character of gold cluster has been indicated through its free radical scavenging properties. This is in contrast to its free radical promoting ability suggested by other workers. Here, we address this controversy by probing the stabilizing effects of Au3 cluster on RO• vs its impacts on RO-H bond dissociation enthalpy, at B3LYP/ LACVP+* level (RH, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, and phenyl). In the presence of Au3 cluster, bond dissociation enthalpy of O-H bond and the spin density at the RO• oxygen are reduced dramatically. These are clear evidences for both the Au3 facilitation of the RO-H bond breakage and its scavenging of RO• radical. Since O-Au anchoring...
Article Journal of Physical Organic Chemistry ; Volume 31, Issue 3 , 2018 ; 08943230 (ISSN) ; Kassaee, M. Z ; Fattahi, A ; Sharif University of Technology
John Wiley and Sons Ltd 2018
Anticancer character of gold cluster has been indicated through its free radical scavenging properties. This is in contrast to its free radical promoting ability suggested by other workers. Here, we address this controversy by probing the stabilizing effects of Au3 cluster on RO• vs its impacts on RO–H bond dissociation enthalpy, at B3LYP/ LACVP+* level (R═H, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, and phenyl). In the presence of Au3 cluster, bond dissociation enthalpy of O–H bond and the spin density at the RO• oxygen are reduced dramatically. These are clear evidences for both the Au3 facilitation of the RO–H bond breakage and its scavenging of RO• radical. Since O–Au...
Ph.D. Dissertation Sharif University of Technology ; Madaah Hosseini, Hamid Reza ; Simchi, Abdolreza
Hyperthermia (also called thermal therapy or thermotherapy) is defined as a type of cancer treatment in which body tissue is exposed to high temperatures, to damage and kill cancer cells, or to make cancer cells more sensitive to the effects of radiation and certain anticancer drugs. The temperature increase required by hyperthermia can be achieved via different heat sources, such as electromagnetic radiation waves (radiofrequency or microwave, ultrasound waves and electrical current. These techniques have shown good results, however, the major problem with present conventional methods is reaching homogenous heat distribution and therapeutic temperatures in the deep region of the tumor to be...
M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein
Access to potable water with standard quality is an inevitable component of human’s lives. Freeze desalination, by consuming lower energy compared to other techniques, relies on the exertion of a cold source which is then accompanied by simultaneous rejection of impurities from water. Regarding this, a numerical study on freeze desalination a hollow cylinder is carried out to determine the effects of the design variables such as heat flux, hydraulic diameter, initial salt concentration, and freezing time on the ice mass, ice salinity, ice generation speed, and Nusselt number on a cold surface of the inner tube. Results show that increasing the value of heat flux from -250 W/m^2 to -1000...
Comparative study on the effect of nitrogen-donor groups versus macro-ring size in O2Nx-azacrowns on the complexation with fullerene, Article Fullerenes Nanotubes and Carbon Nanostructures ; Vol. 22, issue. 4 , 2014 , pp. 322-331 ; ISSN: 1536383X ; Mahloojy, N ; Sharif University of Technology
The interaction of fullerene with a newly synthesized series of 17-to 21-membered macrocyclic ligands containing an O2N3-donor set has been investigated. The formation constants (K) arising from their complexation with fullerene macrocycles, having various ring size, were measured in CHCl3 media by UV-visible spectroscopy applying Benesi-Hildebrand (BH) equation and their stoichiometries were also determined by the Job method. The best K value was measured for 20-membered ring macrocycle in which a 1:1 complexation stoichiometry with fullerene was dominant. Furthermore, 1H NMR spectroscopy data reveled that the macrocylic ligand coordinates fullerene via the nitrogen-donor...
Melting enthalpy and entropy of freestanding metallic nanoparticles based on cohesive energy and average coordination number, Article Journal of Physical Chemistry C ; Volume 115, Issue 35 , August , 2011 , Pages 17310-17313 ; 19327447 (ISSN) ; Delavari H., H ; Madaah Hosseini, H. R ; Sharif University of Technology
An analytical model is proposed to study the effect of particle size on melting enthalpy and entropy of metallic nanoparticles (NPs). The Mott's and Regel's equations for melting entropy in the combination of core average coordination number (CAC) and surface average coordination number (SAC) of freestanding NPs are considered. Clusters of icosahedral (IC), body centered cubic (BCC), and body centered tetragonal (BCT) structure without any vacancies and defects are modeled. Using the variable coordination number made this model to be in good agreement with experimental and molecular dynamic (MD) results of different crystal structures. The model predicts melting entropy and enthalpy of...
M: XNi100- X (M = Ag, and Co) nanoparticles supported on CeO2 nanorods derived from Ce-metal organic frameworks as an effective catalyst for reduction of organic pollutants: Langmuir-Hinshelwood kinetics and mechanism, Article New Journal of Chemistry ; Volume 41, Issue 19 , 2017 , Pages 10948-10958 ; 11440546 (ISSN) ; Gholami, M. R ; Sharif University of Technology
Royal Society of Chemistry 2017
In this study, AgxNi100-x, and CoxNi100-x (x = 0, 20, 40, 60, 80, and 100) bimetallic nanoparticles were successfully decorated on the surface of CeO2 nanorods derived from Ce-metal organic frameworks (Ce-MOF). The as-synthesized products were characterized using different techniques including XRD, FE-SEM, EDX, TEM, ICP, and BET. The as-prepared nanocomposites showed remarkable catalytic activity towards the reduction of organic pollutants such as 4-nitrophenol (4-NP), and rhodamine-B dye (RhB) by NaBH4 solution, with high stability and reusability for five consecutive cycles. The obtained results indicated that among these nanocomposites, Ag80Ni20@CeO2, and Co60Ni40@CeO2 exhibited the best...
Pressure induced structural, electronic, optical and thermal properties of CsYbBr3, a theoretical investigation, Article Journal of Materials Research and Technology ; Volume 10 , 2021 , Pages 687-696 ; 22387854 (ISSN) ; Ali, M. A ; Murad, S ; Ullah, R ; Alshahrani, T ; Laref, A ; Murtaza, G ; Sharif University of Technology
Elsevier Editora Ltda 2021
This article presents the variation of structural, electronic, thermal and optical properties of a halide perovskite CsYbBr3with increasing pressure, employing density functional theory. The pressure effect was determined in range of 0-15 GPa. In which stability of CsYbBr3remains valid, as, verified from negative values of enthalpy of formation and phonon dispersion curves. A significant change was observed in lattice constant, bond lengths, bulk modulus and its pressure derivative, volume and ground state energy, with increasing pressure. The calculated electronic properties presented CsYbBr3as a semiconductor with direct band gap of 3.61 eV. However, pressure rise shift the Yb-d states...
Numerical investigation and parametric analysis of a photovoltaic thermal system integrated with phase change material, Article Applied Energy ; Volume 238 , 2019 , Pages 734-746 ; 03062619 (ISSN) ; Salari, A ; Hakkaki Fard, A ; Ma, T ; Sharif University of Technology
Elsevier Ltd 2019
In this paper, a comprehensive three-dimensional model of photovoltaic thermal system integrated with phase change material (PVT/PCM) is developed and simulated. The effect of some key parameters using parametric analysis on performance of PVT/PCM system with water as working fluid is investigated. Parameters considered in this study include the properties of PCM (i.e. melting temperature, enthalpy of fusion and thermal conductivity), solar radiation and mass flow rate. The parametric analysis ranges are selected according to the properties of the most of available PCMs on the market, which shows the practical application of the numerical research. Furthermore, a three-dimensional model of...
Thermodynamic study on the effect of O 2N 2-azacrown macrocyclic ring-size in complexation with fullerene, Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 21, Issue 5 , Oct , 2013 , Pages 394-402 ; 1536383X (ISSN) ; Aratboni, A. M ; Sharif University of Technology
The interaction of fullerene with a series of 15-19-membered macrocycles containing an O 2N 2-donor set has been investigated by UV-visible spectroscopy. The formation constants arising from the complexation of fullerene with these azacrown macrocycles, having various ring size, were determined in CHCl 3 media applying Benesi-Hildebrand equation. The stoichiometry has been found by the Job method in each case. The thermodynamic parameters, for example, formation enthalpies (δH o) and entropies (δS o), for these complexation were also determined. Experimentally, it was found that macroring size of the azacrown has a prominent effect on azacrown complexation with fullerene in terms...
Binding assessment of two arachidonic-based synthetic derivatives of adrenalin with β-lactoglobulin: Molecular modeling and chemometrics approach, Article Biophysical Chemistry ; Volume 207 , 2015 , Pages 97-106 ; 03014622 (ISSN) ; Bordbar, A. K ; Akvan, N ; Parastar, H ; Fani, N ; Gretskaya, N. M ; Bezuglov, V. V ; Haertlé, T ; Sharif University of Technology
A computational approach to predict the main binding modes of two adrenalin derivatives, arachidonoyl adrenalin (AA-AD) and arachidonoyl noradrenalin (AA-NOR) with the β-lactoglubuline (BLG) as a nano-milk protein carrier is presented and assessed by comparison to the UV-Vis absorption spectroscopic data using chemometric analysis. Analysis of the spectral data matrices by using the multivariate curve resolution-alternating least squares (MCR-ALS) algorithm led to the pure concentration calculation and spectral profiles resolution of the chemical constituents and the apparent equilibrium constants computation. The negative values of entropy and enthalpy changes for both compound indicated...