Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
13 results
Search Results
Now showing 1 - 10 of 13
Article Citation - WoS: 83Citation - Scopus: 93Airfoil Optimization for Noise Emission Problem and Aerodynamic Performance Criterion on Small Scale Wind Turbines(Elsevier Ltd., 2012) Göçmen, Tuhfe; Özerdem, BarışNoise emission is one of the major concerns in wind turbine industry and especially for small scale wind turbines, which are mostly erected to the urban areas; the concern is turning into a problem. This paper focuses on the optimization of six airfoils which are widely used on small scale wind turbines in terms of the noise emission and performance criteria and the numerical computations are performed for a typical 10 kW wind turbine. The main purpose of this optimization process is to decrease the noise emission levels while increasing the aerodynamic performance of a small scale wind turbine by adjusting the shape of the airfoil. The sources of the broadband noise emission are defined and their dominancy is investigated with respect to the operating conditions. While redesigning, together with the principals of reducing the airfoil self-noise, the aerodynamic prospects of increasing the performance have been taken into account. The codes which are based on aero-acoustic empirical models and a collection of well-known aerodynamic functions are used in this study. The results obtained from the numerical analysis of the optimization process have shown that, the considered commercial airfoils for small scale wind turbines are improved in terms of aero-acoustics and aerodynamics. The pressure sides of the baseline airfoils have been manipulated together with the trailing edge and redesigned airfoils have lower levels of noise emission and higher lift to drag ratios. © 2012 Elsevier Ltd.Article Citation - WoS: 11Citation - Scopus: 15Techno-Economic Evaluation of a Ventilation System Assisted With Exhaust Air Heat Recovery, Electrical Heater and Solar Energy(Elsevier Ltd., 2014) Özyoğurtçu, Gamze; Mobedi, Moghtada; Özerdem, BarışThe energy consumed to condition fresh air is considerable, particularly for the buildings such as cinema, theatre or gymnasium saloons. The aim of the present study is to design a ventilation system assisted with exhaust air heat recovery unit, electrical heater and stored solar energy, then to make an economical analysis based on life cycle cost (LCC) to find out its payback period. The system is able to recover thermal energy of exhaust air, store solar energy during the sunlight period and utilize it in the period between 17:00 and 24:00 h. The transient behaviour of the system is simulated by the TRNSYS 16 software for winter period from 1st of November to 31st of March for Izmir city of Turkey. The obtained results show that the suggested ventilation system reduces energy consumption by 86% compared to the conventional ventilation system in which an electrical heater is used. The payback period of the suggested system is found to be 5 years and 8 months which is a promising result in favour of the solar energy usage in building ventilation systems.Article Citation - WoS: 25Citation - Scopus: 25Economical Assessment of Different Hvac Systems for an Operating Room: Case Study for Different Turkish Climate Regions(Elsevier Ltd., 2011) Özyoğurtçu, Gamze; Mobedi, Moghtada; Özerdem, BarışIn this study, the annual energy consumptions of four different heating, ventilation and air conditioning (HVAC) systems serving to operation rooms (ORs) located at five different cities (Izmir, Antalya, Istanbul, Ankara and, Erzurum) in Turkey are analyzed. The study is performed for four different HVAC systems: (a) 100% fresh air system (System I), (b) 100% fresh air with half air volume rate at night period (System II), (c) 100% fresh air with half air volume rate at night period and heat recovery unit (System III), (d) 50% fresh air with half air volume rate at night period and with heat recovery and mixing units (System IV). Life cycle cost (LCC) for 20 years life span is calculated for the considered systems. It is found that System IV considerably reduces energy consumption and it is economically proper for the considered cities. The rate of energy consumption and LCC reductions are greater for the cities with extreme climate condition having relatively low specific humidity ratio. Using System IV instead of System I reduces OR energy consumption by 74% for the city of Erzurum which has a cold and dry climate.Article Citation - WoS: 103Citation - Scopus: 132Break-Even Analysis and Size Optimization of a Pv/Wind Hybrid Energy Conversion System With Battery Storage - a Case Study(Elsevier Ltd., 2009) Ekren, Orhan; Yetkin Ekren, Banu; Özerdem, BarışThis paper aims to show an optimum sizing procedure of autonomous PV/wind hybrid energy system with battery storage and a break-even analysis of this system and extension of transmission line. We use net present value (NPV) method for the comparison of autonomous hybrid energy system and extension of transmission line cases. The case study is completed for the satisfaction of the electricity consumption of global system for mobile communication base station (GSM) at Izmir Institute of Technology Campus Area, Urla, Izmir, Turkey. First, we optimize the PV/wind energy system using response surface methodology (RSM) which is a collection of statistical and mathematical methods relying on optimization of response surface with design parameters. As a result of RSM, the optimum PV area, wind turbine rotor swept area, and battery capacity are obtained as 3.95 m2, 29.4 m2, 31.92 kW h, respectively. These results led to $37,033.9 hybrid energy system cost. Second, break-even analysis is done to be able to decide the optimum distance where the hybrid energy system is more economical than the extension of the transmission line. The result shows that, if the distance between national electricity network and the GSM base station location where the hybrid energy system is assumed to be installed is at a distance more than 4817 m, the installation of hybrid energy system is more economical than the electricity network.Article Citation - WoS: 14Citation - Scopus: 19A Numerical Simulation Study for the Human Passive Thermal System(Elsevier Ltd., 2008) Yıldırım, Eda Didem; Özerdem, BarışThe objective of this study is to create a dynamic model representing a transient three-dimensional passive thermal model of the human body. The model is a multi-segmental, multi-layered representation of the human body with spatial subdivisions which simulates the heat transfer phenomena within the body and at its surface. In order to represent the mechanisms of heat transfer within the body, energy balance equations including conduction with adjacent tissue, heat storage, metabolic heat generation, and convective heat transfer due to the blood flow in the capillaries are taken into consideration for each tissue. The present model of the passive system accounts for the geometric and anatomic characteristics of the human body and considers the thermo-physical and the basal physiological properties of tissue materials. It is assumed that the body is exposed to combination of the convection, evaporation and radiation which are taken into account as boundary conditions when solving the passive thermal system equation. The model is capable of predicting human body temperature in any given environmental conditions. Finite difference solution scheme is used to find out the temperature distribution of human body. The results are compared with the experimental data of previous studies present in the literature. Consequently, the numerical results of present model show good agreement with the experimental data.Article Citation - WoS: 18Citation - Scopus: 25Air Leakage Measurement and Analysis in Duct Systems(Elsevier Ltd., 2006) Aydın, Çiğdem; Özerdem, BarışAir ducts and related equipments are used in a large number of buildings having thermal comfort. In this study, energy loss related with air leakage is studied. The leakage measurement setup was produced according to NEN-EN standards and the evaluation of data have been conducted by using power law model. The measurements were made on 300 and 1000 mm diameter single circular ducts, 300 mm × 250 mm and 1000 mm × 500 mm flanged joint rectangular ducts, 300 and 630 mm diameter circular beaded slip joint ducts, 300 mm × 200 mm and 500 mm × 300 mm rectangular flanged and drive slip joint ducts, and an branched air distribution system having different diameters for positive internal pressures. Test results have showed that the most of air leakage is from the joints. The seam contribution to air leakage is relatively lower than the joints. Using sealing gaskets help to improve the air leakage by about 50%.Article Citation - WoS: 39Citation - Scopus: 41Economic Assessment of Geothermal District Heating Systems: a Case Study of Balçova-Narlıdere, Turkey(Elsevier Ltd., 2006) Erdoğmuş, Berkan; Toksoy, Macit; Özerdem, Barış; Aksoy, NiyaziGeothermal energy is an important renewable energy resource in Turkey. The aim of this research is to evaluate the Balcova-Narlidere geothermal district heating system from an economic perspective. The system is the largest one in Turkey in terms of heating capacity and located in Izmir. Although there are some assessments regarding energy and exergy analysis for the Balcova-Narlidere geothermal district heating system, an economic assessment was not performed, previously. The profitability of the investment is investigated by using internal rate of return method. Seven hundred and eighty different scenarios are developed in this assessment. In order to estimate the potential cash flows in the remaining project life, operating cost in 2002 is decreased and increased, alternatively, between 5% and 30% by 5% in each step, while monthly energy utilization price is changed between US$ 17 and 72 in those scenarios. The energy utilization prices are suggested according to zero IRR value for all scenarios due to the consideration of social and environmental concerns in this investment. It is found that, the proper monthly energy utilization price for a 100 m2 household would be US$ 55.5 when the operating cost and heating capacity in 2002 were remained constant.Article Citation - WoS: 77Citation - Scopus: 89Feasibility Study of Wind Farms: a Case Study for Izmir, Turkey(Elsevier Ltd., 2006) Özerdem, Barış; Özer, Serra; Tosun, MahirWind is one of the world's fastest growing renewable energy sources. The rapid growth in wind power is a result of improvements accomplished in technology. This paper presents the technical and economical feasibility of wind farms. The method is applied to a potential wind farm site located in Izmir, Turkey. The site is considered on technical and economical parameters for the complete plant and its running costs. For technical consideration wind speed, prevailing wind direction, and temperature measurements are performed. For economical consideration, three different scenarios namely, autoproducer, autoproducer group, and independent power producer (IPP) cases, are investigated and compared with respect to net present value (NPV), internal rate of return (IRR), and pay back period (PBP) criteria. The study indicates the costs of generated energy by wind turbines with different characteristics as a function of the installed capacity. It is concluded that, the larger the installed capacity, the smaller the generating cost per kWh. The generating cost was calculated as low as 2.68 UScent/kWh for the IPP scenario. The profitability analysis also shows that, larger installed capacity with larger rated power wind turbines present higher IRR of the investment. The sensitivity analysis backs up the findings.Article Citation - WoS: 138Citation - Scopus: 181An Experimental Study on Performance and Emission Characteristics of a Hydrogen Fuelled Spark Ignition Engine(Elsevier Ltd., 2007) Kahraman, Erol; Özcanlı, Şevket Cihangir; Özerdem, BarışIn the present paper, the performance and emission characteristics of a conventional four cylinder spark ignition (SI) engine operated on hydrogen and gasoline are investigated experimentally. The compressed hydrogen at 20 MPa has been introduced to the engine adopted to operate on gaseous hydrogen by external mixing. Two regulators have been used to drop the pressure first to 300 kPa, then to atmospheric pressure. The variations of torque, power, brake thermal efficiency, brake mean effective pressure, exhaust gas temperature, and emissions of NOx, CO, CO2, HC, and O2 versus engine speed are compared for a carbureted SI engine operating on gasoline and hydrogen. Energy analysis also has studied for comparison purpose. The test results have been demonstrated that power loss occurs at low speed hydrogen operation whereas high speed characteristics compete well with gasoline operation. Fast burning characteristics of hydrogen have permitted high speed engine operation. Less heat loss has occurred for hydrogen than gasoline. NOx emission of hydrogen fuelled engine is about 10 times lower than gasoline fuelled engine. Finally, both first and second law efficiencies have improved with hydrogen fuelled engine compared to gasoline engine. It has been proved that hydrogen is a very good candidate as an engine fuel. The obtained data are also very useful for operational changes needed to optimize the hydrogen fueled SI engine design.Article Citation - WoS: 41Citation - Scopus: 48Wind Energy Potential Estimation and Micrositting on Izmir Institute of Technology Campus, Turkey(Elsevier Ltd., 2005) Türkeli, Hayri Murat; Özerdem, BarışThe aim of this study was to predict the wind energy content over the campus area of Izmir Institute of Technology. The wind data were collected at 10 and 30 m mast heights for a period of 16 months. Mean wind speeds were 7.03 and 8.14 m/s at 10 and 30 m mast heights, respectively. The 'WAsP' and 'WindPRO' softwares were used for the wind statistics and energy calculations. Suitable sites were selected according to the created wind power and energy maps. Wind turbines with nominal powers between 600 and 1500 kW were established for annual energy production calculations and best fitted ones were used for the micrositting.