Prof. Dr. Emrah Özahi
Gaziantep University
Academic Experiences
Thesis
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Supervisor: Prof. Dr. Melda Ö. ÇARPINLIOĞLU
Co-Supervisor: Prof. Dr. M. Yaşar GÜNDOĞDU
October 2011
Abstract
The detection of transition to turbulence in sinusoidal pulsatile pipe flow and the flow dynamics at the onset of transition are analyzed in this study. The experimental study is conducted in the ranges of the time averaged and oscillating Reynolds numbers of 1019≤Reta≤4817 and 107≤Reos≤4261. The velocity amplitude ratio of 0.05≤A1≤0.96 and oscillation frequency of 0.1 Hz≤ f≤14 Hz corresponding to Womersley numbers of 2.72≤√ω´≤32.21 cover the so-called intermediate region of pulsatile flow. The generation and control of the pulsatile flow, the acquisition and processing of the measured data and the analyses of the flow dynamics are carried out by means of the devised program, TDFC.vi in LabView 2009-SP1 environment.
An original detection method is devised in TDFC.vi instead of the transition detection by visual observation in velocity waveforms, cited in the literature. Two dimensionless, dynamic turbulence detection parameters, , of R(dU(r,t)/dt)2 /(Utav ω2) for f ≤ 1 Hz and (dU(r,t)/dt)2/(Uta2ω2) for f >1 Hz are defined. Moreover, two dimensionless, dynamic threshold parameters, , of (1/√ω´)n (n=| f |) for f ≤ 1 Hz and (1/√ω´)4 for f > 1 Hz are defined as a function of √ω´. The detection is based on the comparison of the magnitudes of and .
It is concluded that there is a distinct difference in flow dynamics for √ω´≤8.61 and √ω´>8.61. Namely, at the onset of transition, despite of the noticeable influence of A1 on Reta for √ω´≤8.61, no effect of A1 is observed for √ω´>8.61. There is no effect of √ω´ on Reta for A1=0.10 and A1=0.20 although the significant effect of √ω´ on Reta is observed for A1>0.30 at the onset of transition.
Key Words: Pulsatile flow, laminar to turbulent transition, time averaged Reynolds number, oscillating Reynolds number, Womersley number, velocity amplitude ratio, oscillation frequency.
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Supervisor: Prof. Dr. Melda Ö. ÇARPINLIOĞLU
November 2006
Abstract
In this thesis, a systematic experimental study on flow dynamics through packed beds having different geometrical and physical properties is presented.
To determine the influence of geometrical packed bed properties, 16 different packed beds were used. The covered range of length to diameter ratio of bed L/D was 0.242≤L/D≤1.456. The range of diameter of bed to average diameter of packing material D/d was 5.72≤D/d≤17.16. The range of average diameter of packing material to length of bed d/L was 0.040035≤d/L≤0.722378 and the range of packed bed porosity ε was 0.36≤ε≤0.56.
The packing materials which were used in the experimental study are chickpea, two different sized zeolite, and glass bead. These packing materials were placed into the packed bed with a random loose packing method. The geometrical and physical properties of the packing materials were used as common variables including average diameter of packing material d in the range of 6 mm≤d≤18 mm, packing material density ρm in the range of 640 kg/m3≤ρm≤2675 kg/m3,and particle sphericity Φ in the range of 0.55 ≤Φ≤ 1.0.
In the covered 64 separate test cases, pressure drop across the bed and exit cross-sectional velocity distribution were measured, friction factor in each case was calculated over a flow Reynolds number range of 15000≤Re≤33000 and particle Reynolds number range of 708.2<Rep<7772.73. Measured pressure drops, ΔPBed, were compared with the well-known Ergun’s Equation. The range of ΔPBed/ ΔPErgun was 0.8≤ΔPBed/ΔPErgun≤1.25.
Experimental data were also presented in terms of non-dimensional parameters defined originally through a correlation study involving ΔP* and d/L, ΔP* and Rep(d/L), ΔP* and εRep(d/L), ΔPBed/ΔPEmpty and Rep(d/L) and finally between Rep and Reexit. These correlations are valid in the covered ranges of the experimental study regarding the variables of the packed bed and particularly Rep of providing ease in practice.
Key Words: Packed Bed, Ergun’s Equation, Flow Reynolds Number, Particle Reynolds Number, Exit Reynolds Number, Friction Factor, Bed Porosity, Sphericity, Packing Material Density, Packing Material Average Diameter.
Thesis Supervized
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Thesis Subject: An Investigation of Renewable Energy Potential of Municipal Biodegradable Solid Waste Plants in Frame of Thermodynamic, Thermoeconomic Analysis and Optimization and Developing Sustainable Models Using Zero Waste Approach
Start/Due Date: 2014/-Abstract
The main aim of this thesis is to be able to figure out a sustainable and environmentally friendly waste management policy which can be applied to all solid waste storage, biogas and cogeneration plants in Turkey, by determining the optimum energy recovery strategies that can be integrated to current facilities. In the scope of the proposed models, increasing the energy recovery potentials of current solid waste storage facilities and reducing the environmental emissions are aimed to contribute to health of both human and environment by means of a rational zero waste management strategy.
Zero waste approach is based on reassessment of wastes and in this way, minimization of damage of wastes on the environment by increasing energy recovery potential of current systems. The first step of zero waste management is to be able to figure out all waste constituents in waste elimination facility and also how to eliminate these wastes in order to perform an adequate environmental management. The second step is to integrate the appropriate proposed energy recovery models to current systems according to the present waste elimination techniques. At last step, recovered energy is provided for usage in waste storage plants and/or in energy dense sectors. Zero waste approach can be evaluated as a management style which provides a favorable cost gain with low payback period and increases the current operational efficiency of the facility in long term.
In accordance with the modeling, analyses and assessments to be performed in this study, the energy recovery potential from solid waste in Turkey are presented; the place and importance of energy from waste among other renewable energy sources are emphasized; and lastly, a rational strategy is developed by means of the proposed models in order to apply zero waste approach to current facilities.
In this thesis, first, thermodynamic and thermoeconomic analyses and optimization of Gaziantep Metropolitan Municipality Solid Waste Storage, Biogas and Cogeneration Plant are performed using its operational and economic data. Then, energy recovery models in the frame of zero waste approach are proposed using available waste heat sources of the current plant. After the detailed simulation studies of the proposed models, comparative thermodynamic and thermoeconomic analyses and optimization are done. Simulation and optimization studies to be performed in this thesis are done by using ASPEN One-Tech 8.4 Pro Program and Genetic Algorithm in Matlab.
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Thesis Subject: An experimental study on drying of food materials in a fluidized bed dryer
Start/Due Date: 2011/2013Abstract
The aim of the thesis is to design, product and automatically control of a fluidized bed dryer which operates under both atmospheric and vacuum pressures optionally. Therefore the drying performance and efficiency are investigated in terms of the experimental data such as air velocity, temperature, moisture content, drying time and rate.
The experimental data are used for prediction of minimum fluidization velocity, pressure drop, etc. by proposing the empirical correlations. The obtained experimental data are compared with some available data in the literature and also with the mathematical expressions.
In this thesis, a fluidized bed dryer system also under the vacuum pressure is utilized to eliminate above mentioned problems. The advantages and disadvantages of the fluidized bed dryer optionally operated under both atmospheric and vacuum pressures are researched by taking into consideration of their performances. As a result of the comprehensive literature survey, it can be deduced that there are still many gaps in the research study on fluidized bed dryer at both atmospheric and especially vacuum (reduced pressure) pressures.
Until now, many studies are related with the fluidized bed dryers operated under atmospheric pressures. However, there are many difficulties for the usage of this type of dryers especially in the food and pharmaceutical industries due to the need of high operating temperature. By means of investigation on the dryers operating under vacuum pressure, the positive contribution is satisfied to minimize these difficulties in the applications, and also minimizing the health problems. In this respect, the experimental study gives a contribution to the literature filling gap in this field. The aim is to reduce the energy consumption which is resulted in contribution to the economy. On the other hand, the thesis encourages the student, giving theoretical and industrial insights together.
The performances of both drying techniques are compared with each other in terms of the drying rate, moisture content, drying time air velocity and temperature. The data acquisition, control and flow generation are controlled automatically by means of LabView 2009SP1® environment. The study includes experimental working. In this study, batch fluidized bed dryer is used under both high and vacuum pressure ranges. Theoretical and experimental results are examined using with literature which is about fluidized bed drying systems. The calculations which depend on the air velocity, moisture content, drying time, drying rate are performed.
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Thesis Subject: Thermodynamic and economic analyses and assessment of HVAC applications in buildings for the optimization of energy consumption
Start/Due Date: 2012/2015Abstract
In this study, the optimization of energy consumption in a specified building is performed analyzing and optimizing the variable parameters thermodynamically and economically. Also, different heating and cooling systems are investigated for the same building. The optimum conditions and system are determined as a result of the study.
The optimization of energy consumption is a leading concept in the world due to its decreasing and scarce amount. The efforts for decreasing energy consumption turn into economic recovery. It also provides benefits for health of people and cleaner environment. The thermodynamic and economic analyses are applied for the case study. The variables are controlled for different working conditions. Therefore the optimization of HVAC system is performed. In the analyses, the statistical procedures and techniques are also used in the computer environment.
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Thesis Subject: Thermodynamic and economic analyses and assessment of a coal-fired power plant
Start/Due Date: 2017/OngoingAbstract
In this thesis, a coal-fired thermal power plant is analyzed thermodynamically and economically utilizing real operating data taken from the plant in order to give its updated portrait in terms of energetic and exergetic efficiencies. New models as an energy recovery system are proposed if the efficiencies are found to be less than the nominal expected values. The overall energetic and exergetic efficiencies of the power plant are examined considering all factors that influence the system. Suggestions and developments are outlined in order to increase the overall performances of the existing coal-fired power plants.
The existing coal-fired power plant is analyzed thermodynamically and economically. Therefore, new improvements in terms of energy recovery or waste-to-energy are developed. Besides, the economic analysis of such systems is so important as well as thermodynamic analyses in order to define its exergetic cost rate. Some developments are recommended for further studies. As another M.Sc. study, the thermoeconomic analysis is carried out. In this way, any faults that affect the system thermodynamically, maybe economically are realized and tolerated before constructing of other similar plants by assessing the most exergy destructive sub-components. This thesis also encourages the M.Sc. student to get an ability to analyze an existing system in a power plant thermodynamically and economically.
The energetic and exergetic analyses are performed during this thesis. The actual operating data are taken for different working conditions. EES (Energy Equation Solver) software program is used for these analyses. Therefore the optimization of the system is performed using genetic algorithm (GA) optimization method of MATLAB software.
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Thesis Subject: Aeroelastic Modeling and Analysis of Multi-Aileron Flexible Wings Aircraft
Start/Due Date: 2014/2016Abstract
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Thesis Subject: Lean Energy Approach on Energy Efficiency in a Learning Factory
Start/Due Date: 2020/Abstract
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Thesis Subject: Thermodynamic Analysis and Energy Optimization on a VRF System
Start/Due Date: 2020/Abstract