Sharif Digital Repository

A colorimeter equipped with a gas booster in conjunction with a PVT cell was used to measure the heat capacity of natural gas with different amounts of impurities. Based on new experimental and literature data, a general investigation of the isobaric specific heat capacity was carried out using the Jarrahian-Heidaryan equation of state (J-H-EOS). A model was obtained that is valid in wide ranges of pressures (0.1-40. MPa) and temperatures (250-414. K). The arithmetic average of the model's absolute error is acceptable in engineering calculations and has superiority over other methods in its class  

In this work we have applied the Dense System Equation of State (DSEOS) to electrolyte solutions. We have found that this equation of state can predict the density of electrolyte solutions very accurately. It has been tested for different electrolytes solutions at different temperatures and compositions. A hypothetical binary model has been applied to find the dependencies of parameters of this equation of state on solution temperature and composition. Using such a simple model the heat capacity of NaCl solution was calculated for which the absolute percent deviation is less than 2 %. The DSEOS is tested for the following electrolytes: Na2SO4, MgCl2, MgSO4, KCl, NaCl, and NaBr. We found that... 

To solve the controversy, regarding the existence of an analytic solution to the 1-D Ising model with nearest-neighbor (NN) and next-nearest-neighbor (NNN) interactions in the presence of a magnetic field, we apply the transfer matrix method to solve the 1-D Ising model in the presence of a magnetic field, taking both NN and NNN interactions into account. We show that it is possible to write a transfer matrix only if the number of sites is even. Even in such a case, it is impossible to diagonalize the transfer matrix in an analytic form. Therefore, we employ a numerical method to obtain the eigenvalues of the transfer matrix. Moreover, the heat capacity, magnetization, and magnetic... 

We present a rigorous full quantum mechanical model for the lattice heat capacity of mesoscopic nanostructures in various dimensions. Model can be applied to arbitrary nanostructures with known vibrational spectrum in zero, one, two, or three dimensions. The limiting case of infinitely sized multi-dimensional materials are also found, which are in agreement with well-known results. As examples, we obtain the heat capacity of fullerenes  

Ising models in nanosystems are studied in the presence of a magnetic field. For a one-dimensional (1-D) array of spins interacting via nearest-neighbour and next-nearest-neighbour interactions we calculate the heat capacity, the surface energy, the finite-size free energy and the bulk free energy per site. The heat capacity versus temperature exhibits a common wide peak for systems of any size. A small peak also appears at lower temperatures for small arrays when the ratio of magnetic field spin interaction energy over the nearest-neighbour spin-spin interaction energy, f, is within 0 < F ≤ 0.10 . The peak becomes smaller for longer array and eventually vanishes for long arrays,... 

The regularity problem of heat conduction equation corresponding to modeling of solidification based on the latent heat evolution approach is considered in the present study. It is shown that the corresponding PDE is actually semi-smooth, an issue that has not been taken into account explicitly in the related literature. A general smoothing (regularization) strategy is introduced to solve this problem. More specifically, the smoothed version of the effective heat capacity method is presented in this work. The presented approach is applied to model the quasi steady-state heat transfer problem in the continuous casting process. Numerical experiments demonstrate the success of the presented... 

A molecular dynamics simulation study has been performed to investigate the solidification and remelting of aluminum using Sutton-Chen many body potential. Different numbers of atoms from 108 to 2048 atoms were considered to find an adequate size for the system. Three different cooling and heating rates, i.e. 10 12 K/s, 10 13 K/s and 10 14 K/s, were used. The structure of the system was examined using radial distribution function. The melting and crystallization temperatures of aluminum were evaluated by calculating the variation of heat capacity during the phase transformation. Additionally, Wendt-Abraham parameters were calculated to determine the glass transition temperature. It is shown... 

The effect of electrostatic interactions on vibrational frequencies and thermodynamic properties of CO adsorbate on the Ni(111) surface is calculated by taking the first and second nearest-neighbour interactions into account. In order to obtain reasonable results, the cluster model of various surface adsorption sites with CO adsorbate is partially optimized, using Density Functional Theory and also the MP2 method for the hcp site. Comparison between DFT and MP2 results shows that DFT results are more reliable for this system. The stretching and bending frequencies of CO adsorbate are calculated using both Partial Hessian Analysis and Cluster-Adsorbate Coupling methods. Stretching and bending... 

In this paper an analytical method and a PDE-based solution to control temperature distribution in FGM plates is introduced. For the rectangular FGM plate under consideration, it is assumed that the material properties such as thermal conductivity, density, and specific heat capacity, vary in the width direction (y); and the governing heat conduction equation of the plate is a second-order partial differential equation. Since there has been little control synthesis work for PDE-based systems as compared to the abundance of control design techniques available for ordinary differential equations (ODEs), most of the proposed control approaches for continuous domain rely on discretizing the PDE... 

Application of the fiber contained fluids has been extensively increased in many industries. In the petroleum industry, fibrous fluids are utilized for different applications. For instance, they have been applied in drilling operations for hole cleaning and cutting removal. In this article, the results of the studies performed on the application of Hydrated Basil Seeds (HBS) as the herbal eco-friendly fiber on hole cleaning and filtration control were presented. In order to investigate the application of HBS on hole cleaning, Polyacrylamide (PA) was added to the pure water to provide the base fluid and HBS at different concentrations were suspended in the base fluid and the effect of HBS on... 

In recent years horizontal Ground Heat Exchangers (GHEs) has attracted a growing interest as heat source/sink for ground source heat pump systems. Horizontal GHEs initial installation costs are lower than the vertical ones; however, they require larger land area and more pipes. Therefore, it is necessary to reduce their required land area and pipe length by improving their thermal performance. In this study, a numerical modal based on 3-D simulation of GHE with computational fluid dynamics methods is developed. The model is used to evaluate the thermal performance and initial installation cost of horizontal GHEs. Four different types of horizontal GHEs: linear, spiral, horizontal and... 

Thermal optimization of the vertical continuous casting process is considered in the present study. The goal is to find the optimal distribution of the temperature and interfacial heat transfer coefficients corresponding to the primary and secondary cooling systems, in addition to the pulling speed, such that the solidification along the main axis of strand approaches to the unidirectional solidification mode. Unlike many thermal optimization of phase change problems in which the desirable (target) temperature, temperature gradient, or interface position are assumed to be a priori known, a desirable shape feature of the freezing interface (not its explicit position) is assumed to be known in... 

Metallic nanoclusters are interesting because of their utility in catalysis and sensors. The thermal and physical characteristics of metallic Pt nanoclusters with different sizes were investigated via molecular-dynamics simulations using Quantum Sutton-Chen (QSC) potential. This force field accurately predicts solid and liquid states properties as well as melting of the bulk platinum. Molecular dynamic simulations of Pt nanoclusters with 256, 456, 500, 864, 1372, 2048, 2916, 4000, 5324, 6912, 8788 atoms have been carried out at various temperatures. The Pt-Pt radial distribution function, internal energy, heat capacity, enthalpy, entropy of the nanoclusters were calculated at some... 

Massive amounts of spent lead-acid battery separators with 50 wt % silica nanoparticles (SiNPs) can be recycled for further use. One compelling application is form-stable phase change materials (FSPCMs). This study proposes a novel tertiary eutectic mixture of green and non-toxic lauric acid, palmitic acid, and paraffin, and recycled SiNPs to find a sustainable approach to deal with industrial wastes and energy consumption. Fatty acids and paraffin are promising for thermal energy storage in buildings. However, they lack sufficient thermal conductivity, mechanical strength, and suffer from leakage. To give mechanical strength, high-density polyethylene (HDPE) was added and sintered.... 

Covalently functionalized carbon nanoplatelets and non-covalent functionalized metal oxides nanoparticles (surfactant-treated) have been used to synthesize water-based nanofluids in this paper. To prove nanofluid stability, ultraviolet–visible (UV–vis) spectroscopy is used, and the results show that nanofluid is stable for sixty days for carbon and thirty days for metal oxides. The thermophysical properties are evaluated experimentally and validated with theoretical models. Thermal conductivities of f-GNPs, SiO2, and ZnO nanofluids are enhanced by 25.68%, 11.49%, and 15.42%, respectively. Lu-Li and Bruggeman's thermal conductivity models are correctly matched with the experimental data.... 

Covalently functionalized carbon nanoplatelets and non-covalent functionalized metal oxides nanoparticles (surfactant-treated) have been used to synthesize water-based nanofluids in this paper. To prove nanofluid stability, ultraviolet–visible (UV–vis) spectroscopy is used, and the results show that nanofluid is stable for sixty days for carbon and thirty days for metal oxides. The thermophysical properties are evaluated experimentally and validated with theoretical models. Thermal conductivities of f-GNPs, SiO2, and ZnO nanofluids are enhanced by 25.68%, 11.49%, and 15.42%, respectively. Lu-Li and Bruggeman's thermal conductivity models are correctly matched with the experimental data....