Sharif Digital Repository

In this paper, a unique and applicable method was developed for calculation of efficiency (and mass and heat transfer coefficients) of randomly-packed distillation columns. This method has potential advantages; e.g., unlike all the available methods, it can calculate efficiency without using any empirical mass transfer and hydraulic correlations, and without the need to estimate the operational and hydraulic parameters of an operating column. It, therefore, will be free of errors and limitations of such empirical items and can be used for efficiency calculation of any random packing including new ones. Along with an analysis of the proposed method, the paper also presents a thorough analysis... 

Platinum nanowires (PtNWs) were electrodeposited on the polycarbonate templates (PCTs) in aqueous solution of H2PtCl6 in triply distilled water. Nanowires with diameters of 50 and 100 nanometers were electrodeposited on the same condition. The kinetics of electrodeposition process was studied by electrochemical techniques such as voltammetry and chronoamperometry methods. Increasing the scan rate, the peaks shifted to more negative potentials and the current density also increased in each peak which was typical for a diffusion-control process. The potential range for the deposition of platinum nanowires was specified and consequently the potentiostatic i-t transients were utilized to produce... 

In an increasingly environmentally conscious world, the petroleum industry is faced with the requirements of sustainable development. Petroleum refining is a capital intensive industry consuming much energy that it's cost rises sharply due to high oil price recently. Furthermore, Because the primary source of carbon dioxide discharge is energy use, the regulation requires reduction of energy use. Heat exchanger network synthesis problems (HENs), as a standard problem in process design , have attracted significant research because of the large saving that can be achieved in energy costs. In this work, Heat exchanger network of distillation unit is used as a case study to reduce energy... 

A new small array of cherenkov detectors has been deployed in Tehran, 1200 m above sea level. This array contains of four tanks full of distilled water with diameter of 64 cm and height of 130 cm. The effective area of each tank is about 6.5 × 103cm2 . They are used to detect the air showers and to record the arrival time of the secondary particles. We have collected about 486643 EAS in 5270 h of observation time from Nov-2006 to May-2007. We find zenith and azimuth distribution of EAS with this array. A cosn θ distribution with n = 7.3±0.1 was obtained for zenith angle. Since this tank of distilled water is cheaper and more available than Scintillators it is preferable to use them instead... 

Regarding the energy and environment crisis in the current century and future that threatens human communities, necessity of study and use of supplement fuels is felt more than before. Consumption of natural gas has been increasing rapidly making it one of the most important energy resources in the world. During the last decade the consumption of natural gas increased by almost 25%. By 2020 natural gas is predicted to increase its world energy share to as much as 50% from the present of 22%. The scale of its reserves and its environmental advantage favor its use, (the lower carbon emissions compared to oil and coal along with other reduced emissions of nitrogen oxides and particulates) for... 

Supercritical fluid extraction (SFE) is a relatively new separation technique that has received much attention in recent years. This process is an alternative to distillation or liquid extraction. Its main advantage over the conventional ones is that the dissolved extract may be completely separated from the supercritical fluid simply by decreasing the pressure. In recent years considerable effort has been devoted to the measurement of equilibrium solubility data for solids in supercritical fluids. A coal tar distillate, anthracene oil, which contains 34.46 mass-% phenanthrene, 33.8 mass-% anthracene, 13.89 mass-% carbazole and other impurities, was used as the model mixture. In this study,... 

A brass vortextube is used to carry out a series of experiments. The main objective of the present research is to investigate the separation performances of a vortex tube (VT) for a hydrocarbon mixture. Examination is also applied to study the effects of nozzle intakes number and cold fraction on the gas species separation at specific inlet pressure 236.37 kPa in a VT with two gas mixtures (LPG as a hydrocarbon mixture and LPG-N2). A two-dimensional computational fluid dynamic (CFD) model simulation of a VT is presented. CFD code after validation is also applied to investigate the role of cold fraction and nozzle intakes number on the gas species separation. The highly rotating flow field... 

Abstract Inorganic NiTiO3 nano-pigments have received recent attentions as possible candidates for cool pigment materials to be used in building roofs and facades. In this paper, we have attempted to develop an innovative low temperature (50 °C) synthesis pathway for obtaining NiTiO3 nanocrystals based on an ultrasound-assisted wet chemical processing method. The crystallite size, average particle size and band gap are found to be 11 nm, in the range of 10-20 nm and 3.72 eV, respectively. Ultraviolet-visible (UV-vis) reflectance spectra show that NiTiO3 nanoparticles have a high reflection peak at ∼580 nm, which is associated with the brilliant yellow color... 

The present work investigated the outdoor performance of a basin type multi-stage solar still as well as the effect of collector over basin area (CBA) ratio on the distillate production. The effect of CBA was studied in outdoor experiments for the first time. The system consisted of a still coupled with one, two or three flat-plate solar collectors. In order to study the effect of CBA more accurately, the experiments were conducted in both winter and summer. In these experiments, the distilled water production of the multi-stage still was measured during the whole 24. h of a day on an hourly basis. The results revealed that in the winter, the basin coupled to one solar collector (CBA. =... 

This work offers an extensive framework for the techno-economic evaluation of the subsurface and surface components of low-grade geothermal (< 100 °C) desalination systems, that is based on validated hydrogeological, thermodynamic, and economic considerations. Additionally, this work incorporates a recently developed advanced multi-effect distillation (MED) process for an improved utilisation of the geothermal heat sources. The analysis focuses on a pre-feasibility study for Western Australia, the influence of the different cost drivers, especially the often overlooked geothermal well field parameters like permeability, so as to permit rational assessments of potential application sites. For... 

The aim of this study is to provide a solution for supplying distilled water used in indirect water bath heaters in the pressure reduction stations. A particular type of distilled water production system consists of a typical solar still and a heat pipe heat exchanger was constructed for recovering heat from the exhaust of an indirect gas heater. The system was tested under the climatic conditions of Semnan-Iran. Experimental results showed that in active type, the average daily production rate of distilled water would be 2.06 times higher than passive type. Also, in the proposed system, the average daily energy efficiency and the exergy efficiency would be 65.5% and 41% higher than the... 

Due to the increasing need for drinking water in the world, various membrane processes have been developing significantly over the past several years. The process of membrane distillation is one of the non-isothermal processes that cause steam to pass from the membrane due to the difference in temperature and the resulting difference in vapor pressure. Due to the lack of precision in the amount of flux and thermal efficiency in various operating conditions the membrane distillation process still needs development. This article attempted to examine the effects of flowrate, temperature, and module length on the performance of the membrane distillation process using computational fluid dynamics... 

The increased amount of multi-modal medical data has opened the opportunities to simultaneously process various modalities such as imaging and non-imaging data to gain a comprehensive insight into the disease prediction domain. Recent studies using Graph Convolutional Networks (GCNs) provide novel semi-supervised approaches for integrating heterogeneous modalities while investigating the patients’ associations for disease prediction. However, when the meta-data used for graph construction is not available at inference time (e.g., coming from a distinct population), the conventional methods exhibit poor performance. To address this issue, we propose a novel semi-supervised approach named GKD... 

A novel MED-based desalination system for low-grade heat sources with a temperature between 65 °C and 90 °C has been proposed. Low-grade heat-driven desalination systems are of the most important methods for increasing energy efficiency and assisting the environment along with alleviating the water scarcity problem. The new proposed system is known as cascade multi-effect distillation (CMED). It is designed based on multi-step heat extraction from the heat source fluid (HSF). Multi-step heat absorption helps to form two arrays of MED effects and to utilize two boosters to achieve better performance. The advantage of this system is less complexity (for example, lower vapor injection), and...