Nedim Sözbir - Academia.edu (original) (raw)

Papers by Nedim Sözbir

Research paper thumbnail of Investigation of external heats for cubesats at various low earth orbits

Pamukkale University Journal of Engineering Sciences, Dec 31, 2022

In this paper, radiative heat loads on structural panels of small satellites are simulated for va... more In this paper, radiative heat loads on structural panels of small satellites are simulated for various orbital configurations. Thermal management of small satellites are challenging because of their limited available volumes. Satellites in orbits experience not only extreme temperatures but also rapid temperature changes. In order to provide safe operating conditions, the thermal environment in space must be carefully analyzed. This paper presents a numerical investigation of thermal environment influenced the panels of satellites for various orbital parameters by using Systema Thermica v4.9.0 software with Monte Carlo Ray Tracing (MCRT) method. The results of this study can be useful in the design stage of small satellites operating in similar orbits. Bu çalışmada, küçük uyduların yapısal panellerine etki eden ışınımsal ısı yükleri çeşitli yörünge konfigürasyonları için simüle edilmiştir. Sınırlı kullanılabilir hacimlere sahip olmaları nedeniyle küçük uyduların termal yönetimleri oldukça zordur. Yörüngedeki uydular sadece ekstrem sıcaklıklara değil, aynı zamanda hızlı sıcaklık değişimlerine de maruz kalırlar. Güvenli çalışma koşullarının sağlanması için uzaydaki termal ortamın dikkatlice analiz edilmesi gerekmektedir. Bu makale, Monte Carlo Işın İzleme (MCRT) yöntemi ile Systema Thermica v4.9.0 programı kullanılarak çeşitli yörünge parametrelerinin uydu panellerine etki eden ısıl ortamın sayısal analizine yer vermektedir. Bu çalışmanın sonuçları, benzer yörüngelerde çalışan uyduların tasarım aşamasında yararlı olabilir.

Research paper thumbnail of Heat Transfer of Impacting Water Mist on High Temperature Metal Surfaces

Journal of heat transfer, Jan 29, 2003

Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist... more Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist on high temperature metal surfaces. Local heat transfer coefficients were measured in the film-boiling regime at various air velocities and liquid mass fluxes. The test conditions of water mist cover the variations of air velocity from 0 to 50.3 m/s, liquid mass flux from 0 to 7.67 kg/m2s, and surface temperature of stainless steel between 525°C and 500°C. Radial heat transfer distributions were measured at different liquid mass fluxes. The tests revealed that the radial variation of heat transfer coefficients of water mist has a similar trend to the air jet cooling. At the stagnation point, heat transfer coefficient increases with both the air velocity and the liquid mass flux. The convective air heat transfer is consistent with the published correlation in the literature. The heat transfer contribution due to the presence of water increases almost linearly with the liquid mass flux. The total heat transfer coefficient can be established as two separable effects, which is the summation of the heat transfer coefficient of air and of liquid mass flux, respectively. This study shows that with a small amount of water added in the impacting air jet, the heat transfer is dramatically increased. The Leidenfrost temperature under water mist cooling was also measured. The Leidenfrost temperature increased with both the air velocity and the liquid mass flux.

Research paper thumbnail of SlCAK YÜZEYLERiN SU SİSİYLE SOGUTULMASININ SAYISAL İNCELENMESİ

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Jun 1, 2009

Atmosferik kosullarda yuksek sicakliktaki yuzeylerin spreyle sogutulmasi icin bir sayisal model g... more Atmosferik kosullarda yuksek sicakliktaki yuzeylerin spreyle sogutulmasi icin bir sayisal model gelistirilmistir. Su damlaciklariru tasiyan hava hizi 0-50.29 mis, sivi kutle akisi 0-7.67 kglm2s ve paslanmaz celik yuzey sicakligi 500°C ile 525°C araliginda degismektedir. Degisik sivi kutle akilarinda radyal isi tasinun katsayilari sayisal olarak elde edildi ve literaturdeki sonuclarla karsilastirildi. Yapilan sayisal cozumde, isi tasinini katsayisinin radyal yonde hem ha spreyinde hem de su sisi spreyinde benzer bir egilim gosterdigi gorulmustur. Maksimum isi transferi, durgunlllk bolgesinde meydana gelmektedir. Bu calisma hava spreyi icerisine katilacak kucuk miktarda suyun isi tasinim katsayisini dikkate deger bir bicimde arttirdigini gostermektedir.

Research paper thumbnail of Experimental measurements and computational modeling for the spray cooling of a steel plate near the leidenfrost temperature

Isı Bilimi ve Tekniği Dergisi, 2011

Research paper thumbnail of Spray mist cooling heat transfer in glass tempering process

Heat and Mass Transfer, Oct 21, 2016

engineering processes [1, 2], such as the metallurgical industries for the cooling of high temper... more engineering processes [1, 2], such as the metallurgical industries for the cooling of high temperature metals at film boiling. Water mist cooling at film boiling condition can be also used in many other industrial applications because of its high heat transfer rate. Sprays are made of large drops, in the order of 100 µm or larger, and operated at high mass flux to give high heat transfer rates. However, the heat transfer distribution frequently is not uniform and water utilization efficiency is low. Recently, more and more industrial processes use water mist for cooling. Water mist contains small droplets, on the order of or less than 100 μm, and caries co-flowing air which are entrained or are used for atomization. The mass flux of water mist is low and therefore, the heat transfer rate is not as high as sprays; however, the water mist provides relatively uniform heat transfer and has high water usage efficiency. Furthermore, both water and air flow rates can be adjusted respectively to provide a wide range of heat transfer. Due to these advantages, water mists are used preferably for cooling of thin metal sheets and for tempering of glass at high temperature film boiling conditions. In the high temperature film boiling regime, the impacting droplets of water mist will contact the surface for a very short period of time; however, the resulting heat transfer is significant. The contact heat transfer mechanisms include the convection in the layer of vapor forming underneath the droplets and transient homogeneous nucleation at the point of droplet-surface contact. In addition to the droplet contact heat transfer, there is radiation from the surface and convection associated with bulk air blowing over the surface. Due to the droplets-to-surface contacts, material properties and roughness also influence the heat transfer [3-5]. Energy efficiency improvement opportunities exist within glass plants to improve energy efficiency while maintaining or enhancing productivity. Improving energy efficiency Abstract Energy saving is a very important issue in glass plants, especially in a glass tempering process, where very high velocity air jet impingement is applied during the cooling process of glass tempering. In fact, air compressor energy may be reduced by a spray cooling due to its high heat transfer capabilities. Presently, in this paper, both pure air and water mist spray cooling are investigated in the glass tempering process. The test results indicate that thin and low-cost tempered glass can be made by mist cooling without fracture. It is possible to find the optimal water flux and duration of mist application to achieve a desirable temperature distribution in the glass for deep penetration of the cooling front but without inducing cracking during the tempering. The use of mist cooling could give about 29 % air pressure reduction for 2-mm glass plate and 50 % reduction for both 3-and 4-mm glass plates.

Research paper thumbnail of Multiphase Spray Cooling of Steel Plates Near the Leidenfrost Temperature — Experimental Studies and Numerical Modeling

Atomization and Sprays, 2010

Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist... more Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist on high-temperature surfaces. A numerical model was developed to simulate, for atmospheric applications, air and water mist spray cooling of surfaces heated to temperatures ranging from nucleate to film boiling. Local heat transfer coefficients were measured in the film-boiling regime at various air velocities and liquid mass fluxes. The test conditions of water mist cover the variations of air velocity from 0 to 50.3 m/s, liquid mass flux from 0 to 7.67 kg/m 2 s, and surface temperature of stainless steel between 525 • C and 500 • C. Radial heat transfer distributions were measured at different liquid mass fluxes. The tests revealed that the radial variation of heat transfer coefficients of the water mist has a similar trend to that of air jet cooling. At the stagnation point, the heat transfer coefficient increases with both the air velocity and the liquid mass flux. The convective air heat transfer is consistent with the published correlation in the literature. The heat transfer contribution due to the presence of water increases almost linearly with the liquid mass flux. For dilute sprays, the total heat transfer coefficient can be established as two separable effects, which is the summation of the heat transfer coefficient of air and of liquid mass flux. This study shows that with a small amount of water added in the impacting air jet, the heat transfer is dramatically increased. The Leidenfrost temperature associated with the water mist cooling was also measured. The Leidenfrost temperature increased with both the air velocity and the liquid mass flux. The model simulation was compared against available test data at atmospheric conditions, and the simulation compared favorably well with the test data.

Research paper thumbnail of Prediction of the Solar Array Temperatures of Geostationary Earth Orbit Satellite by Using Analytical Methods

The temperature of the solar array is a very important parameter for the solar array efficiency a... more The temperature of the solar array is a very important parameter for the solar array efficiency and needs to be calculated. In this study, a three-axis stabilized type satellite was used to predict the solar array temperatures at geostationary orbit A one-dimensional analytical solution was presented. The results showed that analytical solution of one-dimensional thermal balance equation for the satellite solar array conditions resulted in a good approximation.

Research paper thumbnail of Dizel Motorlarda Marş Motoru Seçimi

Düzce Üniversitesi bilim ve teknoloji dergisi, Jul 31, 2023

Starter selection is a critical decision in diesel engine design. The starter performance curves ... more Starter selection is a critical decision in diesel engine design. The starter performance curves are generally accepted in the industry, with current on the horizontal axis and power, volts, speed and starter torque on the vertical axis. In this way, it is not possible to compare the starter performance curves with the engine friction force curve. In this study, a method has been developed for the selection of suitable starter for diesel engines. With the developed method, the starter performance curve is converted and the engine friction curve is shown on the same graph. With this method, it can be easily understood whether the starter is suitable for a diesel engine. In addition, possible problems that may be encountered during cold start-up can be foreseen. The developed method uses actual performance measurements given by the starter manufacturer. On the engine side, if there is an existing engine, engine friction test results are used. If the engine is in the design phase, the friction force results obtained by simulation are used.

Research paper thumbnail of Investigation of Cooling Performances at the Gas Turbine Blade Channel

DOAJ (DOAJ: Directory of Open Access Journals), Jul 1, 2014

Türbin kanatlarının soğutulması farklı bölgelerinde farklı soğutma teknikleri kullanarak yapılmak... more Türbin kanatlarının soğutulması farklı bölgelerinde farklı soğutma teknikleri kullanarak yapılmaktadır. Kompresörde üretilen havanın yaklaşık %20'si soğutma sistemlerinde kullanılmaktadır. Kanat içine gönderilen bu hava önce iç kanallardan daha sonrada kanat dış profili üzerinden ve kanat uç kısmından dışarıya atılarak soğutma gerçekleştirilir. Bu soğutma tekniklerinin iç soğutma ve yüzeyde hava filmi meydana getirme ve çarpmalı jetle soğutma teknikleri uygulanmaktadır. Kanatta iç soğutma yapılması için bazen U şeklinde soğutma kanalları kullanılmaktadır. Bu kanallarda çeşitli açılarda kanatçıklar (ripler) kullanılarak soğutma performansları arttırılmaya çalışılmaktadır. Bu çalışmada U şeklindeki 180° dönüşlü düz bir kanalın ve alt ve üst yüzeylerine 90° ve 45° yerleştirilen kanatçıkların yerleştirildiği kanallardaki soğutma performansına etkisi 3 farklı Reynolds sayısı (22000, 27500 ve 33000) için deneysel olarak sıvı kristal termografisi metoduyla kanal yüzeyindeki ısı geçiş katsayısı ve Nu sayısının değişimi araştırılmıştır. Elde edilen sonuçlar jet geometrisinin etkisi, Reynolds sayısının etkisi, kanal içindeki hız dağılımı ve ısı geçiş katsayısı dağılımları gösterilmiştir.

Research paper thumbnail of ECU Oriented Simplified Diesel Engine Model

Academic platform-Journal of engineering and science, May 28, 2021

Research paper thumbnail of Modeling and Analysis of Battery Thermal Control in a Geostationary Satellite

Sakarya University Journal of Science, Aug 31, 2022

Battery technology has been used for satellites since the first satellite sputnik-1 was launched ... more Battery technology has been used for satellites since the first satellite sputnik-1 was launched in 1957. The majority of larger satellite's (geostationary or communication satellites) lives range from 7 to 15 years. During the lifetime of satellites, the batteries used must complete 1000 to 33000 cycles without any problems or likelihood of maintenance. There are three battery technologies, Li-ion, Ni-H2 and Ni-Cd, that are well proven for Geostationary satellite applications. Energy density, lifetime, weight, ampere-hour capacity, depth of discharge, ruggedness and recharge-ability, battery management, thermal management, and self-discharge are main parameters that should be considered when comparing electrical and thermal performance of these three battery technologies. The purpose of this study is to compare the thermal control system for these three batteries for three-axis stabilized geostationary satellites. In particular, the thermal dissipation was compared, which is the temperature range required for battery operation. Thermal analysis was performed for Li-ion batteries using ThermXL software, and showed a temperature results variation ranging between 10.9 o C and 32.7 o C. The temperature during the battery module was not greater that its qualification temperature results.

Research paper thumbnail of Soğutma sistemleri ve ısı pompalarının dizaynı için bir yaklaşım

Isı Bilimi ve Tekniği Dergisi, 1996

Research paper thumbnail of Selection of Geostationary Satellite Launch Vehicle Using Expected Value Analysis

Sakarya University Journal of Science, Oct 1, 2018

Selection of launch vehicle for a geostationary satellite is an important decision for satellite ... more Selection of launch vehicle for a geostationary satellite is an important decision for satellite operators. Depending on only to the cost of the launcher may result unexpected consequences. Lifetime of the satellite is determined by the orbit parameters of the launcher. Success probability of the launcher can be deduced statistically by previous launches or using the insurance rate of the market for the selected launcher. Total cost of the satellite project includes insurance rate besides satellite and launcher costs. Design lifetime of a communication satellite is currently 15 years. Manufacturer warrants the operation of the satellite for 15 years via performance incentive or warranty payback mechanisms. But satellites continue to generate revenues during their maneuver lifetime which is more than 15 years. Expected value analysis is a powerful tool to include probabilistic nature of satellite projects. In this study a method proposed to select the best launcher for a given satellite program incuding satellite price, launch cost, insurance rate and lifetime parameters using expected value analysis.

Research paper thumbnail of Design and Analysis for Thermal Control System of Nanosatellite

It is desirable to be able to turn-around thermal analysis results in a couple of minutes early p... more It is desirable to be able to turn-around thermal analysis results in a couple of minutes early phases of a satellite thermal design. Therefore, ThermXL-spreadsheet-based Thermal Analysis Tool is one of the very flexible and easy-to-use tool that is suited to preliminary design of a nanosatellite. This paper focuses on the thermal design and the results of an initial analysis of the nanosatellite by using ThermXL. The goal of this study is to take suitable measures to ensure all the components will operate in their safe range of temperatures and also a proper heat rejection. The nanosatellite such as Cube Satellite (CubeSat) is a miniaturized satellite that has dimensions of 10cm × 10cm × 10cm and weights of 1kg. The thermal model of CubeSat was modelled and the thermal analysis was performed. The thermal control analysis on this CubeSat with passive thermal control has been conducted by the ThermXL program that provided by ITP Engines. Temperature distribution of solutions was computed with ThermXL. Temperature data met the need of the mission. The results of the temperatures show that the thermal design of nanosatellite is feasible.

Research paper thumbnail of Thermal Control Design of TUSAT

6th International Energy Conversion Engineering Conference (IECEC), Jun 15, 2008

TUSAT is Turkish Communication Satellite, providing mainly communication and TV services using C-... more TUSAT is Turkish Communication Satellite, providing mainly communication and TV services using C-band and Ku-band channels. This paper describes the thermal control design which uses passive and active concepts. The active thermal control is based on heaters regulated by software via thermistors. The passive thermal control composes of heat pipes, multi-layer insulation (MLI) blankets and radiators, paints, surface finishes to maintain temperature level of the overall carrier components within an acceptable value. The thermal control design is supported by thermal analysis using thermal mathematical models (TMM).

Research paper thumbnail of Battery Thermal Design Conception of Turkish Satellite

6th International Energy Conversion Engineering Conference (IECEC), Jun 15, 2008

This paper describes some general aspects of the thermal design of Turkish satellite and presents... more This paper describes some general aspects of the thermal design of Turkish satellite and presents a detailed analysis of the battery and its compartment. The battery compartment is analyzed, using mathematical modeling, to calculate the radiator area and heater power consumption. The battery internal temperature gradients are estimated, also using mathematical modeling, to verify the cells package design. The thermal package was used to create the thermal model where the temperature distributions are predicted by a thermal analyzer.

Research paper thumbnail of Numerical modeling of a ground source heat pump: The Bolu case

Renewable Energy, Nov 1, 2015

The purpose of this study is to present the numerical modeling techniques for a Ground Source Hea... more The purpose of this study is to present the numerical modeling techniques for a Ground Source Heat Pump (GSHP): The Bolu case. Numerical modeling of the GSHP system with horizontal ground heat exchangers operating in heating (1.4 kW) mode was carried out for a room, with 9.68 m 2 floor area, located in Bolu, Turkey. The GSHP simulation model is studied. The codes are written in the MATLAB program for solving the equations obtained from the model developed for the city of Bolu. In this program, additionally, state equations of cooling fluids, which calculate the thermodynamic properties of these fluids, are required. In literature, there are only state equations depending on many coefficients for R12, R22, and R502. So, state equations and table values of ASHRAE of R12, R22, and R502 are used in order to obtain the properties of R134a, R404a, and R410a by using the curve fitting method. The results show that COP values for R134a refrigerant are 3.33 and 3.28 for MATLAB program and Solkane Refrigerant Software program, respectively. The difference on COP was 0.05, i.e. approximately 1.52%. The results obtained from MATLAB program indicate that there was good agreement between Solkane Refrigerant Software program and MATLAB program.

Research paper thumbnail of A Review of Vapor Chambers

Heat Transfer Engineering, Jun 18, 2018

ABSTRACT Future developments in electronic industries will require efficient cooling systems to d... more ABSTRACT Future developments in electronic industries will require efficient cooling systems to dissipate large amount of heat produced over a small area. In recent years, interest has grown in extending the use of vapor chambers to high heat flux electronics cooling because of their low thermal resistance values and uniform temperature distribution abilities. A detailed overview of vapor chambers is presented in this paper including their principle of operation, types of performance characteristics, and various applications. Recent developments in improving the thermal performance of vapor chambers are also presented in this article.

Research paper thumbnail of Havacılıkta Kullanılan Elektronik Podun Isıl Kontrolü

Academic Perspective Procedia, Nov 22, 2019

Pod, havacılıkta farklı görevler için kullanılmak üzere içerisinde çeşitli faydalı yükler bulundu... more Pod, havacılıkta farklı görevler için kullanılmak üzere içerisinde çeşitli faydalı yükler bulunduran kutudur. Bu faydalı yükler elektronik ekipmanlardan oluşurken; keşif, arazi gözetleme, hedefleme, kızılötesi görüş, navigasyon gibi görevlerde kullanılmak üzere pod içerisine yerleştirilir. Pod; ön, orta ve arka olmak üzere üç ana bölümden oluşur.

Research paper thumbnail of Propellant Budget Calculation Of Geostationary Satellites

Academic Perspective Procedia, Nov 9, 2018

Propellant budget of the geostationary satellites has to be calculated during preliminary design ... more Propellant budget of the geostationary satellites has to be calculated during preliminary design phase to properly size propellant tanks, mass and dimensions of the satellite. Lifetime of the satellite depends on the propellant budget. A guideline for calculation of propellant budget of geostationary satellites is presented. Proposed method has enough accuracy for initial design phase of the satellite.

Research paper thumbnail of Investigation of external heats for cubesats at various low earth orbits

Pamukkale University Journal of Engineering Sciences, Dec 31, 2022

In this paper, radiative heat loads on structural panels of small satellites are simulated for va... more In this paper, radiative heat loads on structural panels of small satellites are simulated for various orbital configurations. Thermal management of small satellites are challenging because of their limited available volumes. Satellites in orbits experience not only extreme temperatures but also rapid temperature changes. In order to provide safe operating conditions, the thermal environment in space must be carefully analyzed. This paper presents a numerical investigation of thermal environment influenced the panels of satellites for various orbital parameters by using Systema Thermica v4.9.0 software with Monte Carlo Ray Tracing (MCRT) method. The results of this study can be useful in the design stage of small satellites operating in similar orbits. Bu çalışmada, küçük uyduların yapısal panellerine etki eden ışınımsal ısı yükleri çeşitli yörünge konfigürasyonları için simüle edilmiştir. Sınırlı kullanılabilir hacimlere sahip olmaları nedeniyle küçük uyduların termal yönetimleri oldukça zordur. Yörüngedeki uydular sadece ekstrem sıcaklıklara değil, aynı zamanda hızlı sıcaklık değişimlerine de maruz kalırlar. Güvenli çalışma koşullarının sağlanması için uzaydaki termal ortamın dikkatlice analiz edilmesi gerekmektedir. Bu makale, Monte Carlo Işın İzleme (MCRT) yöntemi ile Systema Thermica v4.9.0 programı kullanılarak çeşitli yörünge parametrelerinin uydu panellerine etki eden ısıl ortamın sayısal analizine yer vermektedir. Bu çalışmanın sonuçları, benzer yörüngelerde çalışan uyduların tasarım aşamasında yararlı olabilir.

Research paper thumbnail of Heat Transfer of Impacting Water Mist on High Temperature Metal Surfaces

Journal of heat transfer, Jan 29, 2003

Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist... more Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist on high temperature metal surfaces. Local heat transfer coefficients were measured in the film-boiling regime at various air velocities and liquid mass fluxes. The test conditions of water mist cover the variations of air velocity from 0 to 50.3 m/s, liquid mass flux from 0 to 7.67 kg/m2s, and surface temperature of stainless steel between 525°C and 500°C. Radial heat transfer distributions were measured at different liquid mass fluxes. The tests revealed that the radial variation of heat transfer coefficients of water mist has a similar trend to the air jet cooling. At the stagnation point, heat transfer coefficient increases with both the air velocity and the liquid mass flux. The convective air heat transfer is consistent with the published correlation in the literature. The heat transfer contribution due to the presence of water increases almost linearly with the liquid mass flux. The total heat transfer coefficient can be established as two separable effects, which is the summation of the heat transfer coefficient of air and of liquid mass flux, respectively. This study shows that with a small amount of water added in the impacting air jet, the heat transfer is dramatically increased. The Leidenfrost temperature under water mist cooling was also measured. The Leidenfrost temperature increased with both the air velocity and the liquid mass flux.

Research paper thumbnail of SlCAK YÜZEYLERiN SU SİSİYLE SOGUTULMASININ SAYISAL İNCELENMESİ

Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Jun 1, 2009

Atmosferik kosullarda yuksek sicakliktaki yuzeylerin spreyle sogutulmasi icin bir sayisal model g... more Atmosferik kosullarda yuksek sicakliktaki yuzeylerin spreyle sogutulmasi icin bir sayisal model gelistirilmistir. Su damlaciklariru tasiyan hava hizi 0-50.29 mis, sivi kutle akisi 0-7.67 kglm2s ve paslanmaz celik yuzey sicakligi 500°C ile 525°C araliginda degismektedir. Degisik sivi kutle akilarinda radyal isi tasinun katsayilari sayisal olarak elde edildi ve literaturdeki sonuclarla karsilastirildi. Yapilan sayisal cozumde, isi tasinini katsayisinin radyal yonde hem ha spreyinde hem de su sisi spreyinde benzer bir egilim gosterdigi gorulmustur. Maksimum isi transferi, durgunlllk bolgesinde meydana gelmektedir. Bu calisma hava spreyi icerisine katilacak kucuk miktarda suyun isi tasinim katsayisini dikkate deger bir bicimde arttirdigini gostermektedir.

Research paper thumbnail of Experimental measurements and computational modeling for the spray cooling of a steel plate near the leidenfrost temperature

Isı Bilimi ve Tekniği Dergisi, 2011

Research paper thumbnail of Spray mist cooling heat transfer in glass tempering process

Heat and Mass Transfer, Oct 21, 2016

engineering processes [1, 2], such as the metallurgical industries for the cooling of high temper... more engineering processes [1, 2], such as the metallurgical industries for the cooling of high temperature metals at film boiling. Water mist cooling at film boiling condition can be also used in many other industrial applications because of its high heat transfer rate. Sprays are made of large drops, in the order of 100 µm or larger, and operated at high mass flux to give high heat transfer rates. However, the heat transfer distribution frequently is not uniform and water utilization efficiency is low. Recently, more and more industrial processes use water mist for cooling. Water mist contains small droplets, on the order of or less than 100 μm, and caries co-flowing air which are entrained or are used for atomization. The mass flux of water mist is low and therefore, the heat transfer rate is not as high as sprays; however, the water mist provides relatively uniform heat transfer and has high water usage efficiency. Furthermore, both water and air flow rates can be adjusted respectively to provide a wide range of heat transfer. Due to these advantages, water mists are used preferably for cooling of thin metal sheets and for tempering of glass at high temperature film boiling conditions. In the high temperature film boiling regime, the impacting droplets of water mist will contact the surface for a very short period of time; however, the resulting heat transfer is significant. The contact heat transfer mechanisms include the convection in the layer of vapor forming underneath the droplets and transient homogeneous nucleation at the point of droplet-surface contact. In addition to the droplet contact heat transfer, there is radiation from the surface and convection associated with bulk air blowing over the surface. Due to the droplets-to-surface contacts, material properties and roughness also influence the heat transfer [3-5]. Energy efficiency improvement opportunities exist within glass plants to improve energy efficiency while maintaining or enhancing productivity. Improving energy efficiency Abstract Energy saving is a very important issue in glass plants, especially in a glass tempering process, where very high velocity air jet impingement is applied during the cooling process of glass tempering. In fact, air compressor energy may be reduced by a spray cooling due to its high heat transfer capabilities. Presently, in this paper, both pure air and water mist spray cooling are investigated in the glass tempering process. The test results indicate that thin and low-cost tempered glass can be made by mist cooling without fracture. It is possible to find the optimal water flux and duration of mist application to achieve a desirable temperature distribution in the glass for deep penetration of the cooling front but without inducing cracking during the tempering. The use of mist cooling could give about 29 % air pressure reduction for 2-mm glass plate and 50 % reduction for both 3-and 4-mm glass plates.

Research paper thumbnail of Multiphase Spray Cooling of Steel Plates Near the Leidenfrost Temperature — Experimental Studies and Numerical Modeling

Atomization and Sprays, 2010

Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist... more Experimental studies were conducted to reveal the heat transfer mechanism of impacting water mist on high-temperature surfaces. A numerical model was developed to simulate, for atmospheric applications, air and water mist spray cooling of surfaces heated to temperatures ranging from nucleate to film boiling. Local heat transfer coefficients were measured in the film-boiling regime at various air velocities and liquid mass fluxes. The test conditions of water mist cover the variations of air velocity from 0 to 50.3 m/s, liquid mass flux from 0 to 7.67 kg/m 2 s, and surface temperature of stainless steel between 525 • C and 500 • C. Radial heat transfer distributions were measured at different liquid mass fluxes. The tests revealed that the radial variation of heat transfer coefficients of the water mist has a similar trend to that of air jet cooling. At the stagnation point, the heat transfer coefficient increases with both the air velocity and the liquid mass flux. The convective air heat transfer is consistent with the published correlation in the literature. The heat transfer contribution due to the presence of water increases almost linearly with the liquid mass flux. For dilute sprays, the total heat transfer coefficient can be established as two separable effects, which is the summation of the heat transfer coefficient of air and of liquid mass flux. This study shows that with a small amount of water added in the impacting air jet, the heat transfer is dramatically increased. The Leidenfrost temperature associated with the water mist cooling was also measured. The Leidenfrost temperature increased with both the air velocity and the liquid mass flux. The model simulation was compared against available test data at atmospheric conditions, and the simulation compared favorably well with the test data.

Research paper thumbnail of Prediction of the Solar Array Temperatures of Geostationary Earth Orbit Satellite by Using Analytical Methods

The temperature of the solar array is a very important parameter for the solar array efficiency a... more The temperature of the solar array is a very important parameter for the solar array efficiency and needs to be calculated. In this study, a three-axis stabilized type satellite was used to predict the solar array temperatures at geostationary orbit A one-dimensional analytical solution was presented. The results showed that analytical solution of one-dimensional thermal balance equation for the satellite solar array conditions resulted in a good approximation.

Research paper thumbnail of Dizel Motorlarda Marş Motoru Seçimi

Düzce Üniversitesi bilim ve teknoloji dergisi, Jul 31, 2023

Starter selection is a critical decision in diesel engine design. The starter performance curves ... more Starter selection is a critical decision in diesel engine design. The starter performance curves are generally accepted in the industry, with current on the horizontal axis and power, volts, speed and starter torque on the vertical axis. In this way, it is not possible to compare the starter performance curves with the engine friction force curve. In this study, a method has been developed for the selection of suitable starter for diesel engines. With the developed method, the starter performance curve is converted and the engine friction curve is shown on the same graph. With this method, it can be easily understood whether the starter is suitable for a diesel engine. In addition, possible problems that may be encountered during cold start-up can be foreseen. The developed method uses actual performance measurements given by the starter manufacturer. On the engine side, if there is an existing engine, engine friction test results are used. If the engine is in the design phase, the friction force results obtained by simulation are used.

Research paper thumbnail of Investigation of Cooling Performances at the Gas Turbine Blade Channel

DOAJ (DOAJ: Directory of Open Access Journals), Jul 1, 2014

Türbin kanatlarının soğutulması farklı bölgelerinde farklı soğutma teknikleri kullanarak yapılmak... more Türbin kanatlarının soğutulması farklı bölgelerinde farklı soğutma teknikleri kullanarak yapılmaktadır. Kompresörde üretilen havanın yaklaşık %20'si soğutma sistemlerinde kullanılmaktadır. Kanat içine gönderilen bu hava önce iç kanallardan daha sonrada kanat dış profili üzerinden ve kanat uç kısmından dışarıya atılarak soğutma gerçekleştirilir. Bu soğutma tekniklerinin iç soğutma ve yüzeyde hava filmi meydana getirme ve çarpmalı jetle soğutma teknikleri uygulanmaktadır. Kanatta iç soğutma yapılması için bazen U şeklinde soğutma kanalları kullanılmaktadır. Bu kanallarda çeşitli açılarda kanatçıklar (ripler) kullanılarak soğutma performansları arttırılmaya çalışılmaktadır. Bu çalışmada U şeklindeki 180° dönüşlü düz bir kanalın ve alt ve üst yüzeylerine 90° ve 45° yerleştirilen kanatçıkların yerleştirildiği kanallardaki soğutma performansına etkisi 3 farklı Reynolds sayısı (22000, 27500 ve 33000) için deneysel olarak sıvı kristal termografisi metoduyla kanal yüzeyindeki ısı geçiş katsayısı ve Nu sayısının değişimi araştırılmıştır. Elde edilen sonuçlar jet geometrisinin etkisi, Reynolds sayısının etkisi, kanal içindeki hız dağılımı ve ısı geçiş katsayısı dağılımları gösterilmiştir.

Research paper thumbnail of ECU Oriented Simplified Diesel Engine Model

Academic platform-Journal of engineering and science, May 28, 2021

Research paper thumbnail of Modeling and Analysis of Battery Thermal Control in a Geostationary Satellite

Sakarya University Journal of Science, Aug 31, 2022

Battery technology has been used for satellites since the first satellite sputnik-1 was launched ... more Battery technology has been used for satellites since the first satellite sputnik-1 was launched in 1957. The majority of larger satellite's (geostationary or communication satellites) lives range from 7 to 15 years. During the lifetime of satellites, the batteries used must complete 1000 to 33000 cycles without any problems or likelihood of maintenance. There are three battery technologies, Li-ion, Ni-H2 and Ni-Cd, that are well proven for Geostationary satellite applications. Energy density, lifetime, weight, ampere-hour capacity, depth of discharge, ruggedness and recharge-ability, battery management, thermal management, and self-discharge are main parameters that should be considered when comparing electrical and thermal performance of these three battery technologies. The purpose of this study is to compare the thermal control system for these three batteries for three-axis stabilized geostationary satellites. In particular, the thermal dissipation was compared, which is the temperature range required for battery operation. Thermal analysis was performed for Li-ion batteries using ThermXL software, and showed a temperature results variation ranging between 10.9 o C and 32.7 o C. The temperature during the battery module was not greater that its qualification temperature results.

Research paper thumbnail of Soğutma sistemleri ve ısı pompalarının dizaynı için bir yaklaşım

Isı Bilimi ve Tekniği Dergisi, 1996

Research paper thumbnail of Selection of Geostationary Satellite Launch Vehicle Using Expected Value Analysis

Sakarya University Journal of Science, Oct 1, 2018

Selection of launch vehicle for a geostationary satellite is an important decision for satellite ... more Selection of launch vehicle for a geostationary satellite is an important decision for satellite operators. Depending on only to the cost of the launcher may result unexpected consequences. Lifetime of the satellite is determined by the orbit parameters of the launcher. Success probability of the launcher can be deduced statistically by previous launches or using the insurance rate of the market for the selected launcher. Total cost of the satellite project includes insurance rate besides satellite and launcher costs. Design lifetime of a communication satellite is currently 15 years. Manufacturer warrants the operation of the satellite for 15 years via performance incentive or warranty payback mechanisms. But satellites continue to generate revenues during their maneuver lifetime which is more than 15 years. Expected value analysis is a powerful tool to include probabilistic nature of satellite projects. In this study a method proposed to select the best launcher for a given satellite program incuding satellite price, launch cost, insurance rate and lifetime parameters using expected value analysis.

Research paper thumbnail of Design and Analysis for Thermal Control System of Nanosatellite

It is desirable to be able to turn-around thermal analysis results in a couple of minutes early p... more It is desirable to be able to turn-around thermal analysis results in a couple of minutes early phases of a satellite thermal design. Therefore, ThermXL-spreadsheet-based Thermal Analysis Tool is one of the very flexible and easy-to-use tool that is suited to preliminary design of a nanosatellite. This paper focuses on the thermal design and the results of an initial analysis of the nanosatellite by using ThermXL. The goal of this study is to take suitable measures to ensure all the components will operate in their safe range of temperatures and also a proper heat rejection. The nanosatellite such as Cube Satellite (CubeSat) is a miniaturized satellite that has dimensions of 10cm × 10cm × 10cm and weights of 1kg. The thermal model of CubeSat was modelled and the thermal analysis was performed. The thermal control analysis on this CubeSat with passive thermal control has been conducted by the ThermXL program that provided by ITP Engines. Temperature distribution of solutions was computed with ThermXL. Temperature data met the need of the mission. The results of the temperatures show that the thermal design of nanosatellite is feasible.

Research paper thumbnail of Thermal Control Design of TUSAT

6th International Energy Conversion Engineering Conference (IECEC), Jun 15, 2008

TUSAT is Turkish Communication Satellite, providing mainly communication and TV services using C-... more TUSAT is Turkish Communication Satellite, providing mainly communication and TV services using C-band and Ku-band channels. This paper describes the thermal control design which uses passive and active concepts. The active thermal control is based on heaters regulated by software via thermistors. The passive thermal control composes of heat pipes, multi-layer insulation (MLI) blankets and radiators, paints, surface finishes to maintain temperature level of the overall carrier components within an acceptable value. The thermal control design is supported by thermal analysis using thermal mathematical models (TMM).

Research paper thumbnail of Battery Thermal Design Conception of Turkish Satellite

6th International Energy Conversion Engineering Conference (IECEC), Jun 15, 2008

This paper describes some general aspects of the thermal design of Turkish satellite and presents... more This paper describes some general aspects of the thermal design of Turkish satellite and presents a detailed analysis of the battery and its compartment. The battery compartment is analyzed, using mathematical modeling, to calculate the radiator area and heater power consumption. The battery internal temperature gradients are estimated, also using mathematical modeling, to verify the cells package design. The thermal package was used to create the thermal model where the temperature distributions are predicted by a thermal analyzer.

Research paper thumbnail of Numerical modeling of a ground source heat pump: The Bolu case

Renewable Energy, Nov 1, 2015

The purpose of this study is to present the numerical modeling techniques for a Ground Source Hea... more The purpose of this study is to present the numerical modeling techniques for a Ground Source Heat Pump (GSHP): The Bolu case. Numerical modeling of the GSHP system with horizontal ground heat exchangers operating in heating (1.4 kW) mode was carried out for a room, with 9.68 m 2 floor area, located in Bolu, Turkey. The GSHP simulation model is studied. The codes are written in the MATLAB program for solving the equations obtained from the model developed for the city of Bolu. In this program, additionally, state equations of cooling fluids, which calculate the thermodynamic properties of these fluids, are required. In literature, there are only state equations depending on many coefficients for R12, R22, and R502. So, state equations and table values of ASHRAE of R12, R22, and R502 are used in order to obtain the properties of R134a, R404a, and R410a by using the curve fitting method. The results show that COP values for R134a refrigerant are 3.33 and 3.28 for MATLAB program and Solkane Refrigerant Software program, respectively. The difference on COP was 0.05, i.e. approximately 1.52%. The results obtained from MATLAB program indicate that there was good agreement between Solkane Refrigerant Software program and MATLAB program.

Research paper thumbnail of A Review of Vapor Chambers

Heat Transfer Engineering, Jun 18, 2018

ABSTRACT Future developments in electronic industries will require efficient cooling systems to d... more ABSTRACT Future developments in electronic industries will require efficient cooling systems to dissipate large amount of heat produced over a small area. In recent years, interest has grown in extending the use of vapor chambers to high heat flux electronics cooling because of their low thermal resistance values and uniform temperature distribution abilities. A detailed overview of vapor chambers is presented in this paper including their principle of operation, types of performance characteristics, and various applications. Recent developments in improving the thermal performance of vapor chambers are also presented in this article.

Research paper thumbnail of Havacılıkta Kullanılan Elektronik Podun Isıl Kontrolü

Academic Perspective Procedia, Nov 22, 2019

Pod, havacılıkta farklı görevler için kullanılmak üzere içerisinde çeşitli faydalı yükler bulundu... more Pod, havacılıkta farklı görevler için kullanılmak üzere içerisinde çeşitli faydalı yükler bulunduran kutudur. Bu faydalı yükler elektronik ekipmanlardan oluşurken; keşif, arazi gözetleme, hedefleme, kızılötesi görüş, navigasyon gibi görevlerde kullanılmak üzere pod içerisine yerleştirilir. Pod; ön, orta ve arka olmak üzere üç ana bölümden oluşur.

Research paper thumbnail of Propellant Budget Calculation Of Geostationary Satellites

Academic Perspective Procedia, Nov 9, 2018

Propellant budget of the geostationary satellites has to be calculated during preliminary design ... more Propellant budget of the geostationary satellites has to be calculated during preliminary design phase to properly size propellant tanks, mass and dimensions of the satellite. Lifetime of the satellite depends on the propellant budget. A guideline for calculation of propellant budget of geostationary satellites is presented. Proposed method has enough accuracy for initial design phase of the satellite.