Sharif Digital Repository

This research study presents an experimental investigation on forced convection heat transfer of an aqueous ferrofluid flow passing through a circular copper tube in the presence of a magnetic field. Both constant magnetic field and alternating magnetic field was examined. Moreover magnetic field layout and strength and modes of alternating magnetic field was investigated. The flow passes through the tube under a uniform heat flux and laminar flow conditions. The primary objective was to intensify the particle migration and disturbance of the boundary layer by utilizing the magnetic field effect on the nanoparticles for more heat transfer enhancement. Complicated convection regimes caused by... 

The main purpose of this research is analyzing the energy stream of clean food production by using Iran's power plants sourced waste heat. In order to achieve this goal, at first, greenhouse heating demand model according to the type of crops and geographic location of greenhouse, heat transport from power plant to greenhouse model, and heat exchanger model is presented. Then, the potential of constructing clean greenhouse around power plants has been evaluated by using the concept of industrial symbiosis and by integrating greenhouse energy demand, waste heat transport, and heat exchanger models into industrial symbiosis concept framework and also by economical and geographical assessments.... 

This project related to gas purification according to difference in the deposition point in the fludized bed.The main reason for choosing fluidized bed is increasing overall heat transfer coefficient compare in to other heat exchangers. Separation process, by cooling the wall causes the self- deposition gas phase shifts to solid phase. Solid formed on the wall, act as an insulating layer and greatly reduces the heat transfer. To solve this problem, the fluidized bed system is offered because fluid particles in addition to remove the insulating layer, improving convection heat transfer coefficient . Laboratory tests show the feasibility of preventing the formation of insulating layer by... 

The use of nanofluids to improve the heat transfer has a special attention in the industry. researches focus on the efficiency of heat transfer nanofluids dates back to 1998. Ferrofluids are a particular type of nanofluids which their nanoparticles have magnetic effect and heat transfer can be increased by applying magnetic field to them. In this work, thermal and hydrodynamic performance of ferromagnetic fluid which flows through a copper tube in thermal entrance region has been studied. The flow in the tube is laminar and is affected by constant heat flux. Part of the tube contains a porous medium with paramagnetic properties and porosity of 0.46. Ferrofluid is composed of F e3O4 and water... 

The limitation of fossil fuel sources and environmental damage caused by use of these fuels have made researches on applications of renewable energy, especially solar energy, to be an important issue in recent years. An important issue that arises in the use of photovoltaic panels is the reduction of their efficiency with increasing their temperature. By increase of a degree of Celsius, the efficiency of the photovoltaic panel decreases by 0.45%. The aim of this project is to reduce the temperature of the photovoltaic panel by using porous medium and air. The porous medium used as fins under the panel.Experimental results have shown that by using the medium placed under the photovoltaic... 

Double channel and coreless induction furnaces are used extensively in many processing industries due mainly to their good heating efficiency, high production rate, clean working environments and relatively low operating costs. The study of heat transfer treatment and evaluation of the heat losses of these furnaces becomes an important issue in melting industries. In this dissertation, a heat transfer analysis will be performed for an induction furnace and heat losses by conduction, convection, Eddy-Current and Hysteresis in a furnace structure, and radiation from the body of a specific induction furnace will be modeled considering the symmetry of the furnace chamber. The models presented in... 

Shortage of energy sources in the new decade along with the increasing level of greenhouse gas emissions urges researchers in the field of energy to explore for the new source of energy as well as seeking for methods for usage of available energy resources more efficiently. Therefore, development of building with low level of energy usage may significantly reduce the need for grid energy. This can be met with new construction materials to reduce the energy consumption, using renewable energies sources such as solar and wind as well as design and development of materials with capability to store energy. The use of materials which can store energy and release it when needed has been considered... 

The lubricating oil is commonly used to cool down the moving parts of turbine gas systems. In many applications, this oil is cooled down using a recirculating water circuit. The water is then cooled down using an air-cooled heat exchanger. Any deficiency in aerothermodynamic design of such heat exchanger would result in high temperature of gas turbine moving parts such as bearings. Obviously, this mal-performance has adverse effect on the lifetime of these parts and their maintanence aspects. Since the good performance of air-cooled heat exchanger has numerous advantages for the performance of related gas turbine unit, it is mandatory to design these heat exchangers in minimum sizes and... 

The present article studies the isothermal and non-isothermal water injection into naturally fractured oil reservoirs by numerical simulation. The fractures in naturally fractured reservoirs can possess different characteristics. In addition. a remarkable number of naturally fractured reservoirs contain relatively heavy oils that could not be extracted economically; hence. the thermal recovery methods are extensively used for these reservoirs. Hot water injection is one of the thermal recovery methods that has not been explored enough compared to its alternatives. In this study. the effectiveness of the hot water injection over the cold (isothermal) water injection in oil production is... 

In the present work, the experiments were carried out for two types of PAM (3330 and 3630) with three distinct concentrations (25, 40 and 55 ppm) and TiO_2-water nanofluid for four concentrations (1.5, 2, 2.5 and 3 vol. %), and the Nusselt number and friction factor for each of them expressed separately. The Reynolds number was in the range from 11000 to 21000. The steady state turbulent convective heat transfer and friction factor of the combination of TiO_2-water nanofluid and polymer 3330 in the coiled tube were investigated. The effects of the Reynolds number for 2 vol. % nanoparticles which consists of 25 ppm PAM (3330) determined at the constant temperature of 24°C. It was observed... 

Lithium-ion batteries have the ability to store a significant amount of energy and work at high power, which has led to the wide spread of their use in various industries. In high-power applications, battery heat management increases lifespan, safety, and reduces battery power loss. In this study, the heat management of a very common and widely used 18650 battery using multi-layered phase change material has been investigated. The reason for using multiple layers is that each phase change material has its own weaknesses in addition to its advantages. It is expected that with the proper use of several phase change materials in the thermal management system, the materials will reduce the... 

In this Thesis ,the two-dimensional thermoelastic tractive rolling contact problem for an FGM coated half-plane under the plane strain deformation is investigated. A rigid cylinder rolls on the surface of an FGM coated half-plane with constant translational velocity, generating frictional heat in the slip zones of the contact area. Thermo-mechanical properties of the FGM vary exponentially along the thickness. It is assumed that the contact area consists of a central stick zone and two slip zones of the same sign. The transfer matrix method and Fourier integral transform technique are used to achieve a system of two Cauchy singular integral equations. The associated governing equations are... 

Simulation runs have been conducted to predict the evolution of sand drying in conical spouted beds with a non-porous draft tube. In the simulation runs, the moisture content of the solid phase was assumed to be 7 % (kg water/kg sand). The simulation results were validated against experimental results reported by Olazar et al. and good agreement was obtained.Influences of various physical and geometrical parameters such as superficial gas velocity, inlet temperature, length and diameter of draft tube and initial moisture content on the sand drying were investigated. Temperature and gas velocity are the most important parameters for improving the drying process and reduce the drying time of... 

In this research convective heat transfer coefficient enhancement of nanofluids prepared from high surface area graphene has been investigated in laminar flow in the developing region. The nanofluid has been prepared from nanoporous graphene with high surface area and with concentration of 0.025 to 0.1 %wt. Deionized water has been used as the base fluid and a type of Ter-Polymer has been utilized as the surfactant. The results indicate that thermal conductivity of nanofluid with concentration of 0.1 %wt remains quite constant, with only %3.8 enhancement, while convective heat transfer coefficient improves significantly, with 34% enhancement. The behavior of this enhancement related to the... 

In this thesis, we are focusing on the heat transport mechanism in one of the most applicable kinds of superconducting detectors called, YBa2Cu3O7-x (YBCO) transition-edge bolometer. The Time Domain Thermoreflectance (TDTR) method is described as a tool for investigating the thermal boundary conductance and thermal conductivity of the materials, and the measured thermal conductivity of our YBCO films is reported here. Although some recent papers have shown a dependence of the thermal conductivity of the YBCO films to their thickness, our results on many samples with different substrates didn’t show the reported thickness dependency and we have obtained the thermal conductivity of the YBCO... 

This dissertation argues that bi-conductive textured surfaces increase both Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) simultaneously. Surface modification is applied to stainless steel specimens by the anodizing method in an electrolyte containing Ammonium Fluoride and DI-Water and Ethylene Glycol as the based solvent. The process of oxidation was under constant DC voltage and constant temperature. The contact angle on self-aligned Nano-porous oxide layer fabricated on the substrate substantially decreases to about 5.7 degree which has a dramatic effect on CHF. Furthermore, the oxide layer augments the boiling efficiency by increasing the number of active sites and... 

In terms of thermodynamics and heat transfer, heat pipes such as closed two-phase thermosyphon are of great importance in saving energy. In this study, a computational fluid dynamics model for simulation of a thermosyphon heat pipe with two-phase flow including phase change heat transfer was developed. The study has mainly focused on the effects of volume concentrations of Nanoparticles and the operating temperature on the heat transfer performance of the thermosyphon. The analysis was performed to compare heat transfer performance between a solid copper tube and a thermosyphon heat pipe which contained deionized water and graphene oxide(GO)/water Nanofluid as its working fluids. Based on a... 

In this thesis, desublimation (deposition) of xenon gas has been studied. Through the past decades, desublimation, became one of the important methods of separation. High purity products and applicability when common methods of separation, as distillation, are not applicable, make desublimation more efficient. Heat transfer phenomenological study of direct phase change of gas to solid (desublimation), evaluation of variation of different parameters during the phase change and finally comparison of experimental results of desublimation and mathematical modeling data are the main considerations in present thesis. Because of low cost and accessibility and heat transfer phenomenological study... 

This study highlights an important distinction between heat transfer mechanism in dry and saturated soil. Soil temperature data recorded during model tests, soil thermal response predicted using finite difference and analytical methods are compared with finite element models. In recent years, due to the industrial development of human societies, the energy consumption has been increased worldwide. On the other hand, the most commonly used energy resources are non-renewable energies. Therefore, governments and industries aimed to develop a technology which provides economical use of renewable energy sources. One of the renewable energy sources is the geothermal energy of the Earth. In this...