An Experimental Investigation of Liquid Droplet Impingement on a Molten Phase Change Material as a Direct-Contact Solidification Method

, M.Sc. Thesis Sharif University of Technology Faghiri, Shahin (Author) ; Shafii, Mohammad Behshad (Supervisor)

Abstract

Improving the discharge process of phase-change materials (PCMs) is of great importance. In this study, the process of acetone drop impact on molten paraffin, as a direct-contact solidification method, is experimentally investigated. Four Weber numbers (corresponding to heights of 10, 20, 30, and 40 cm) for the acetone drop and six surface temperatures (66, 68, 70, 75, 80, and 90 °C) for the molten paraffin are considered. As the acetone drop impacts the molten paraffin, the drop absorbs heat from the melting paraffin and boils, solidifying a portion of the molten paraffin. Two important parameters that govern the acetone drop dynamics and the solidification of the molten paraffin are the...

Multi-objective optimization of acetone droplet impingement on phase change material in direct-contact discharge method

, Article Journal of Energy Storage ; Volume 46 , 2022 ; 2352152X (ISSN) Faghiri, S ; Aria, H. P ; Shafii, M. B ; Sharif University of Technology

Elsevier Ltd 2022

Abstract

Improving the discharge process of phase change materials (PCMs) is of great importance and can be effective for thermal energy storage (TES) systems. In this research, the direct-contact method for acetone droplet on molten paraffin is optimized to enhance the efficiency of the discharge process of PCMs and TES systems working with intermediate boiling fluid (IBF). In order to improve the storage rate and increase the freezing rate in the system, the NSGA-II algorithm is used. When the acetone droplet hits, owing to its low boiling point relative to the temperature of molten paraffin, the acetone evaporates, causing the creation of solidified paraffin area. The main goal of the current...

The impingement of liquid boiling droplet onto a molten phase change material as a direct-contact solidification method

, Article Thermal Science and Engineering Progress ; Volume 23 , 2021 ; 24519049 (ISSN) Faghiri, S ; Mohammadi, O ; Hosseininaveh, H ; Shafii, M. B ; Sharif University of Technology

Elsevier Ltd 2021

Abstract

The boiling of a fluid dripping on the surface of molten phase-change materials provides an efficient means for heat exchange or cooling of the melt. For the first time, in this study, the impact of acetone drops onto molten paraffin as a direct-contact solidification method is experimentally investigated to get a better insight into the interaction between the drop boiling and the heat extraction process from the phase change materials during impact. As the acetone drop impacts the molten paraffin surface, acetone starts to boil, and a portion of molten paraffin is solidified. Four impact Weber numbers (corresponding to heights of 10, 20, 30, and 40 cm) for the acetone drop and six surface...

A comprehensive study on the complete charging-discharging cycle of a phase change material using intermediate boiling fluid to control energy flow

, Article Journal of Energy Storage ; Volume 35 , 2021 ; 2352152X (ISSN) Hosseininaveh, H ; Mohammadi, O ; Faghiri, S ; Shafii, M. B ; Sharif University of Technology

Elsevier Ltd 2021

Abstract

The low melting and solidification rates of phase change materials (PCM), which traces back to their low thermal conductivity coefficient, has led the application of these materials to face limitations. This paper aims to explore the effectiveness of a novel method called intermediate boiling fluid (IBF) in speeding up the energy storage and transfer processes in PCMs during a complete charging-discharging cycle. Throughout this novel technique, paraffin and acetone are utilized as PCM and IBF, respectively. In the solidification process, there is no direct contact between the cold source and the molten paraffin, while acetone, as an intermediate fluid, is being boiled via absorbing...

Hydrothermal analysis of non-Newtonian fluid flow (blood) through the circular tube under prescribed non-uniform wall heat flux

, Article Theoretical and Applied Mechanics Letters ; Volume 12, Issue 4 , 2022 ; 20950349 (ISSN) Faghiri, S ; Akbari, S ; Shafii, M. B ; Hosseinzadeh, K ; Sharif University of Technology

Elsevier Ltd 2022

Abstract

The present article aims to investigate the Graetz-Nusselt problem for blood as a non-Newtonian fluid obeying the power-law constitutive equation and flowing inside the axisymmetric tube subjected to non-uniform surface heat flux. After the flow field is determined by solving the continuity and the momentum equations, the energy equation is handled by employing the separation of variables method. The resulting Eigen functions and Eigen values are numerically calculated using MATLAB built-in solver BVP4C. The analysis is first conducted for the situation of constant heat flux and subsequently generalized to apply to the case of sinusoidal variation of wall heat flux along the tube length,...

Multi-objective optimization of multiple droplet impacts on a molten PCM using NSGA-II optimizer and artificial neural network

, Article Scientific Reports ; Volume 13, Issue 1 , 2023 ; 20452322 (ISSN) Faghiri, S ; Poureslami, P ; Partovi Aria, H ; Shafii, M.B ; Sharif University of Technology

Nature Research 2023

Abstract

Embracing an interaction between the phase change material (PCM) and the droplets of a heat transfer fluid, the direct contact (DC) method suggests a cutting-edge solution for expediting the phase change rates of PCMs in thermal energy storage (TES) units. In the direct contact TES configuration, when impacting the molten PCM pool, droplets evaporate, provoking the formation of a solidified PCM area (A). Then, they reduce the created solid temperature, leading to a minimum temperature value (T min). As a novelty, this research intends to maximize A and minimize T min since augmenting A expedites the discharge rate, and by lowering T min, the generated solid is preserved longer, resulting in...

Optimization approach for MoS2-water ethylene glycol mixture nanofluid flow in a wavy enclosure

, Article International Journal of Thermofluids ; Volume 18 , 2023 ; 26662027 (ISSN) Hosseinzadeh, K ; Akbari, S ; Faghiri, S ; Shafii, M. B ; Sharif University of Technology

Elsevier B.V 2023

Abstract

The mixed convective heat transfer in a two-dimensional enclosure containing ethylene glycol-water mixture-based MoS2 nanofluid in the presence of magnetic field and thermal radiation is evaluated, adopting Galerkin standard finite element method. The Boussinesq approximation is applied to simulate natural convection. The partial differential governing equations with the appropriate boundary conditions are numerically handled using FlexPDE software. In order to validate the implemented numerical method, results were compared against outcomes obtained from the previous studies. Afterward, the influences of key indicators such as Hartmann number (Ha), Radiation parameter (Rd), Volume fraction...

Numerical analysis of latent thermal energy storage system under double spirally coiled tube configuration with two separated paths

, Article Thermal Science and Engineering Progress ; Volume 37 , 2023 ; 24519049 (ISSN) Faghiri, S ; Ahmadi, R ; Akbari, S ; Shafii, M. B ; Sharif University of Technology

Elsevier Ltd 2023

Abstract

The current research attempts to illustrate results of a reliable 3-D numerical simulation to scrutinize the charging process of paraffin as the phase change material (PCM) in an innovative heat exchanger called double spirally coiled tube heat exchanger (DSCTHE) with two separated paths. The water as a heat-transfer fluid (HTF) streams through the double spiral tubes embedded throughout the latent thermal energy storage (LTES) system. The PCM melting characteristics under three different geometries are investigated. After validating the proposed numerical simulation model, the impacts of operational and geometrical factors including inlet temperature of HTF and radius of the inner spiral...

Modeling the dual-fuel combustion of porous lycopodium particles and diesel using an analytical simulation framework

, Article Journal of Analytical and Applied Pyrolysis ; Volume 163 , 2022 ; 01652370 (ISSN) Tashakori, S ; Akbari, S ; Faghiri, S ; Sadeghi, S ; Xu, F ; Sharif University of Technology

Elsevier B.V 2022

Abstract

In this paper, a comprehensive analytical study is performed to assess the lycopodium-diesel dual-fuel combustion system in counter-flow premixed configuration. The system is modeled as multiple zones that are coupled together via proper boundary and jump conditions on interfaces. According to the respective reaction and transport phenomena in these zones, conservation equations of mass and energy are derived, non-dimensionalized, and solved by Matlab and Mathematica in an analytical way. The porosity of lycopodium particles and the thermal radiation from the reaction zone and the post-flame zones into the preheating zone are considered, in order to improve the realism and accuracy of the...

Functional Mapping of Regions Involved In Addiction Using Magnetic Resonance Imaging and Proposing a New Measure for Multivariate Methods

, M.Sc. Thesis Sharif University of Technology Faghiri, Ashkan (Author) ; Vosughi Vahdat, Bijan (Supervisor) ; Ekhtiari, Hamed (Co-Advisor)

Abstract

Methamphetamine (meth) abuse and addiction (MA), with its serious medical, psychiatric and social complications, is a growing national disaster in Iran. Response control deficit during exposure to drug related cues is one of the main neurocognitive cores in MA and results in continued drug use and treatment failure. There have been many studies focused on cue exposure, but most of their paradigms required subjects to passively view the cues; this aspect of these paradigms cause a wide gap between reality and experimental studies. Developing a functional and structural neuroimaging protocol to map realistic brain circuits that are involved in craving among meth users is of importance....

Hierarchical Optical Network-on-Chip Based on Hypercube Topology

, M.Sc. Thesis Sharif University of Technology Abdollahi, Meisam (Author) ; Hesabi, Shahin (Supervisor)

Abstract

According to prediction of ITRS, power consumption and bandwidth of processors' interconnection, will be the most major bottleneck of the System-on- Chips (SoCs) in the future. Therefore, in MultiProcessor System-on-Chip (MPSoC) architectures, the design constraints will be altered from "Computational Constraints" to "Communicational Constraints". There are three kinds of communications in the surface of the chip: Global, median and local. The main difference between global and local connections is that the length of latter one will be changed with technology. In other words, it is scalable like processor's elements while the length of global connections is practically constant. Even though...

Architecture of Reconfigurable Optical Network-on-Chip

, M.Sc. Thesis Sharif University of Technology Falahati, Hajar (Author) ; Hesabi, Shahin (Supervisor)

Abstract

According to power limitation on a chip and the need to simultaneously access high utilization and low power consumption, Multi-Processor System-on-Chip (MPSoC) architectures have been introduced. The major part of power consumption in a network on chip belongs to interconnects. One of the most important issues is to decrease power consumption while maintaining high utilization. The ability of optical interconnects in decreasing power consumption and increasing utilization has introduced a new architecture called optical network on chip. This architecture uses the benefits of optical signals and elements in order to transfer data. In this thesis, we introduce a new architecture with...

Analysis of Off-Critical Percolation Clusters by Schramm-Loewner Evolution

, M.Sc. Thesis Sharif University of Technology Jamali, Tayyeb (Author) ; Rouhani, Shahin (Supervisor)

Abstract

Recently, a new tool in the study of two-dimensional continuous phase transition was provided by Schramm-Loewner evolution. The main part of SLE is a conformal map which relates growth process of a two-dimensional simple curve to one-dimensional motion on the real axis (so-called Loewner driving function). Time evolution of this map and Loewner driving function is connected via the Loewner differential equation. It turns out that for a certain class of stochastic and conformally invariant curves in two dimensions, the driving function shows Brownian motion in one dimension. Strength point of SLE comes from this fact that all the geometrical properties of such curves is described through a...

The Watershed Model and Schramm-loewner Evolution

, Ph.D. Dissertation Sharif University of Technology Daryaei, Ebrahim (Author) ; Rouhani, Shahin (Supervisor)

Abstract

Schramm Loewner evolution (SLE) is a one-parameter family of random simple curves in the complex plane introduced by Schramm in 1999 which is believed to describe the scaling limit of a variety of domain interfaces at criticality. This thesis is concerned with statistical properties of watersheds dividing drainage basins. The fractal dimension of this model is 1.22 which is consistent with the known fractal dimension for several important models such as Invasion percolation and minimum spanning trees (MST). We present numerical evidences that in the scaling limit this model are SLE curves with =1.73, being the only known physical example of an
SLE with <2. This lies outside the...

Energy Efficient Concurrent Test of Switches and Links for Networks-On-Chip

, M.Sc. Thesis Sharif University of Technology Alamian, Sanaz (Author) ; Hessabi, Shahin (Supervisor)

Abstract

Nowadays by increasing the number of processing cores in system-on-chip, using networks-on-chip, as an optimized interconnection foundation for transferring data between processing cores is inevitable .Based on this, the necessity of designing and implementing an optimized structure for testing network-on-chip, considering various overheads such as power consumption, latency, bandwidth and area, becomes an important issue in designing network-on-chip. The purpose of this project is to design an optimized structure for testing routers and connecting links in network, which considers power consumption overhead, latency and area overhead on one hand, and fault coverage on the other hand....

High Speed CDMA Communication in Optical Network on Chip

, M.Sc. Thesis Sharif University of Technology Abdi, Mania (Author) ; Hesabi, Shahin (Supervisor)

Abstract

As the number of processing cores on a single chip continues to grow, the need for a high band width, low power communication structure, will be the most important requirements of next generation chip multiprocessors. Today, a major part of power consumption in multi core architectures belongs to interconnects. Due to these facts, reducing consuming power, as well as supporting high performance, is concerned in these architectures. The concept of “network-on-chip” emerged to improve the performance of CMPs. But now a day, considering the circumstances of power budges, it’s incapable of presenting new strategies to decrease consuming power and delay. However, optical interconnects have the...

Modified WK-Recursive Topology for an Optical Network-on-Chip

, M.Sc. Thesis Sharif University of Technology Mahdavian, Hojjat (Author) ; Hesabi, Shahin (Supervisor)

Abstract

Nowadays, a large proportion of the power consumption in high-performance multi-processor architectures on chip belongs to connections. Reducing power consumption while maintaining high efficiency in these architectures is one of the main concerns. Networks on Chip (NoC) originally were introduced to improve efficiency, but now, given the importance of power, we must provide some solutions to reduce power consumption, and delay in NOCs. Connections in chip can be divided into three categories: global, intermediate and local, while the length of global connections is almost constant in different scales, local connections are scalable. As a result improving efficiency of a small number of...

AdS3/CFT2 In The Presence of N=1 Supergravity

, M.Sc. Thesis Sharif University of Technology Fattahi, Mohammad (Author) ; Rouhani, Shahin (Supervisor)

Abstract

Brown and Henneaux showed that asymptotic symmetries of asymptotically form a conformal group in two dimensions [1]. Also they could derive classical central charge of theory. Fourteen years later, Maldacena, conjectured that this Holographic correspondence could be true for a specific theory a simplified chromodynamics in the boundary of ), this holographic theory attracted physicist communitee's attention. Many physicists tried to make this conjecture more precise. It is worth to say that, no example of holographic correspondence has been completely proven, till now, Because of the difficulty of the calculation. However these days we consider Madacena conjectrure in any arbitrary...

Design and Implementation of a 2x2 LTE Channel Simulator

, M.Sc. Thesis Sharif University of Technology Shahin, Keyvan (Author) ; Shabany, Mahdi (Supervisor)

Abstract

In this thesis, a hardware is designed and implemented for testing the perfoemance of MIMO communication systems in LTE standard using SCM channel model. This hardware can be used for measuring the BER of 2x2 wireless systems. This hardware is the first channel emulator, with hardware implementation which is using SCM channel model and implementation of a similar one has not been reported.In addition to the implementation of the mentioned channel emulator, a new approach is used for implementing a Gaussian variate generator (GVG) which is implemented on both FPGA and ASIC and shows better characteristics in comparison with the works done in the past. ASIC implementation of this part is done...

Hardware Trojan Detection: A Size-Aware Approach

, M.Sc. Thesis Sharif University of Technology Heydarshahi, Behnam (Author) ; Hesabi, Shahin (Supervisor)

Abstract

With constant increase in the rate of VLSI circuits manufactured in sites separate from the designers and computer architects, global concern regarding the possibility of integration of malware by the manufacturing foundries has arisen. Particularly, one main issue that affects reliability of the chips is modifications or additions with malicious intention,known as Hardware Trojans, which are easily applicable during design and manufacturing phase of chips. There has been an increasing fraud in chip-set manufacturing. Hardware Trojans may leak confidential information outside the chip, to the attacker, may alter the function of circuit, or completely fail a system. Hence search for new...