Sharif Digital Repository

Using Aspen Hysys to simulate burners and furnaces has been the focus of several studies in recent years. According to the studies and investigations carried out in the field of optimal design of the furnace, heating the air is one of the possible tasks to improve the performance and increase the efficiency. According to the obtained results, by adding air preheat, the efficiency increases from 92% to 96%. Also, to validate the simulation, two furnaces from Sepahan Oil Refinery furnaces were simulated in the field of oil production, which were simulated with an error of less than 1% in duty calculation, and according to the general results obtained, adding air preheat can increase the... 

Smoke is the largest cause of fire related deaths. A smoke control system is an engineered system that modifies smoke movement for the protection of building occupants, firefighters and properties. Unfortunately, in case of fire, stairwells and elevators are frequently filled with smoke, preventing effective evacuation. Many smoke control systems use mechanical fans to control smoke by providing positive pressure at strategic locations. Pressure difference across a barrier can control smoke movement by preventing smoke on the low-pressure side of the barrier from migrating to the high-pressure side. Building designers use codes and rules of thumb to design their building against fire.... 

In this study different models of an aerodynamic particle sizer and aerodynamic focusing lens were introduced and governing equations for an aerodynamic focusing lens for flow fields and particle motions were discussed. An aerodynamic focusing lens was simulated for analyzing particle motions and flow fields. Two kinds of models are considered; One was Ahmadi`s model and the other one was Wang`s model and both models are axisymmetric. The results show that for small particles (sub 30 nanometers), Brownian motions were highly effective on transmission efficiency and producing particle beams. The two models are compared and the results show that Ahmadi`s model produce narrower particle beams... 

Insulin pump treatment is considered the most physiological way to imitate the healthy body's insulin profile in patients with diabetes. They provide a precisely controlled rate of insulin delivery to diabetic patients who would normally need multiple daily injections to regulate blood glucose levels. The firmware allows numerous modifications to the bolus dose and basal rate to enable patients to manage insulin levels in response to events such as eating, sleeping, and exercise.
In this Study, we have first investigated different models of insulin pumps on the market and chose the Spring ZoneTM insulin pump model for our study due to its innovative technology. This pump employs a... 

Aerosol measurement is used in different fields such as nanotechnology and materials science, environmental air pollution monitoring and air quality measurements, combustion and engine exhaust, inhalation toxicology and medical studies. One of the most prevalent methods for aerosol measurement uses electrical mobility. An electrical mobility spectrometer (EMS) is used to classify particles ranging from 10 – 1000 nanometers, under the influence of an electric field. There are two electrodes in EMS between which the aerosol and sheath air flow. Charged particles in the aerosol and sheath enter the device from one end and are subjected to an electric field. Passing through the annulus,... 

Particulate air pollution is one of the top environmental health risks. Industrial processes like power generation from fossil fuels and steel and cement manufacturing release a huge amount of particles into the atmosphere. Moreover, internal combustion engines produce a considerable amount of particulate matter in populated areas. The usual way to overcome this risk is using air-cleaning devices such as filters. Filters are designed for specific purposes like removing aerosol particles, aerosol sampling and collecting valuable particles. Because of its diverse applications, filtration has become an active area of research and many kinds of filters are currently available. One type of... 

Most of the current literature on the simulation of the electro-osmotic flow in micro-channels decompose electric potential to two components; internal and external potentials. They usually approximate the near wall changes in the ion concentration (called double layer) which is physically responsible for electro-osmotic force by a model (like Poisson equilibrium distribution or Debye-Huckel approximation). There are reports in the literature which show that the approximations lose their fidelity for more complex situations. In this thesis we solve the full system of Nernst-Planck and Navier-Stokes equations by resolving electric double layer. The proposed... 

Nowadays cell-based microfluidic devices have many applications. One of the applications is disease diagnosis according to number of cells. Cell counting has different methods, such as optical cell counting, flow cytometry, hemocytometry, coulter counters,and so on. One of the methods of cells counting is based on measurement of changes in impedance or conductivity of surrounding medium because ions are released from surface-immobilized cells inside a micr of luidic channel.The method of cell lysate impedance spectroscopy is sensitive enough and it was offered for detecting and enumerating CD4+ cells in HIV patients. In this study,... 

In recent decades, metal nanoparticles have been used in medicine for example in cancer treatment. There have always been debates on the nanoparticles specifications such as particle size, amount of surface charge and the particle material. Meanwhile, the study on selecting appropriate properties of nanoparticles for this purpose is very essential and expensive in medical science. In order to access the best efficiency and the least mortality of the patients in treatments, simulation studies can support the medical scientists. In this thesis, the goal is to study transferring nanoparticles as a drug or included drugs through created hypothetical micro-channels in cancerous cells membrane.... 

Cascade impactors are the instruments which are used to assess the particle size distribution and the cut off diameter. Cascade impactors are wildly used for hygiene purposes, environmental, and toxicological studies. However, to find out the accurate size distribution, the cut off diameter of each stage which is different for different types of impactors with different geometry specifications should be determined. In this study first the basis of the cascade impactor operation is described. Next, different types of cascade impactors are introduced, and the Andersen Cascade Impactor (ACI) is chosen to design. The design criteria are explained and the dimension of each stage, entrance cone,... 

Recent advances in micro-technology are finding important applications especially in chemical and biological processes. In these applications, mixing has a profound importance. Due to the inherent low Reynold’s number flow in micro systems, diffusion mixing is the dominant mixing mechanism at these scales. This is in contrary to the high Reynold’s number ordinary applications where turbulent mixing plays the major role. There are two major classes of micro-mixers: passive and active. Passive micro-mixers rely on geometric features to enhance mixing. Active micro-mixers on the other hand, use external excitation to promote and control the rate of mixing. In this work, using numerical tools,... 

The “Lab-on-a-Chip” is a micro-scale device which uses fluids as working medium and can handle number of functions such as sample preparation and transfer, separation, bio-sensing and detection. One of the important parts of these devices is micro-mixer, that should blend two fluid species in a short time with desirable mixing quality. Micro-mixers are classified as passive and active. By considering the micro-scale of mixers, turbulence phenomena cannot occur due to dominance of viscous forces, therefore the mixing only depends on molecular diffusion. This thesis consists of two main parts, in the first part algebraic multigrid has been studied and implemented in Rayan (in-house CFD code).... 

When classical Fourier law of heat conduction is not applicable due to finite speed of heat propagation in a medium, non-Fourier heat conduction is used. In non-Fourier heat conduction, heat transfer is studied considering finite speed of heat flux (thermal wave) or temperature gradient or both (dual phase lag). Biological tissues like skin are one of the materials which show non-Fourier behavior during usual heating processes. In this research heat transfer in human skin is modeled by Fourier, thermal wave and dual phase lag (DPL) models. The equations are solved using the finite difference method and the temperature distribution across the tissue is calculated. In thermal wave model,... 

This research investigates the hydrodynamic interaction of a squat submarine operating behind a ship in various wave and resistance experiments for towing and self-propelling arrangements. A one-tenth scaled captive model of a 0.625 m squat submarine is constructed along with a 1.5 m Fridsma ship to perform 116 unique experiments in a 4×6×400 m3 tank located in a towing tank center. The submarine is a new midget-submersible, of Apam-Napat SMSD type, with an L/D ratio below four. The cable is specified, regarding its weight per unit length, using a scaling method introduced in this research. Wave and resistance tests are performed for various 2D relative lengths and depths at short-distance... 

This research empirically examines the hydrodynamic performances of squat submarines under the resistance and wave tests, besides the numerical investigation of pressure drag reduction techniques. Submarines are limited for public use due to military classification issues and being expensive. This research introduces a new squat submarine in order to enable underwater exploration. This squat submarine has a 9- person capacity as a manned midget submersible using specific geometries of length-over-depth ratios (L/D) below four. The cause of such selection is to provide better visibility for the passengers to research and explore the sea. However, the geometrical features considerably change... 

Cleanrooms have a broad scope of applications from electronics, pharmacy, biotechnology to hospital industries, and are susceptible to fine and ultra-fine particles. In this work operating room in the category of hospital applications is chosen. Airborne particles in the operating room depends on many factors such as room geometry, inlet and outlet design, air displacement rate, obstacles, etc. Surgical light is one of the most critical obstacles in the operating room as it is upstream to the surgery zone. The study presented in this thesis aimed to numerically investigate the influence of radiation emitted from the medical lamps on the indoor airflow quality in operating room environment.... 

Amorphous SiBNC ceramics have been developed as new high temperature materials. They show a high resistance against crystallization, high mechanical properties, low density, and high oxidation stability. Three synthesis methods have been developed for synthesis of SiBNC ceramics namely, Reactive magnetron sputtering, Mechanical alloying plus sintering, and polymer-derived ceramics. In this research among polymeric methods one pot synthesis due to high ceramic yield and high mechanical properties have been chosen. Two major methods for nanofiber preparation are Meltspinning and Electrospinng. It is notable that all of researches for SiBNC Nanofiber preparation has been conducted on... 

Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of...