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... 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 Interests: Engineering, Mechanical Engineering, Chemical Engineering, Materials Science, Thermodynamics, and 13 moreWater, Heat Transfer, Temperature, Heat transfer coefficient, Heat Flux, Application, Interdisciplinary Engineering, Mist, Convective Heat Transfer, Critical Heat Flux, Heat Transfer Coefficients, Nucleate Boiling, and Film boiling
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... 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.
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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... 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.
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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.... 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.
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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... 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 Interests: Engineering, Design, Control Systems, Thermal, Satellite, and 2 moreThermal Analysis and Cubesat(Thermal Analysis and Cubesat)
(Thermal Analysis and Cubesat)
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... 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).
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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... 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.
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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... 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.
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Temperature constantly changing across space hence low and high temperature occurs on geostationary orbit (GEO) communication satellites by the impact of environmental heat loads. Thus, the thermal control analysis becomes very important... more
Temperature constantly changing across space hence low and high temperature occurs on geostationary orbit (GEO) communication satellites by the impact of environmental heat loads. Thus, the thermal control analysis becomes very important fact to protect GEO satellites from the space environmental effects throughout launch and lifetime. In this study, the numerical models will be shown by thermal analysis with respect to absorptivity values, emissivity values, view factor etc. within desired temperatures of the equipment. Solar flux effects have taken into account. Thermal uncertainty values are used to analyze the thermal control for the communication satellites. One of the important parameters for thermal control optimization is material selection. As a result of this study, a selection of materials of satellite thermal design will be emphasized how important and effective it is.
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A time dissemination system which distributes time signals over a geostationary satellite has been developed. The developed system utilizes IRIG-B format for time distribution and achieves accuracy figures better than 1 ms over Turkey.... more
A time dissemination system which distributes time signals over a geostationary satellite has been developed. The developed system utilizes IRIG-B format for time distribution and achieves accuracy figures better than 1 ms over Turkey. Time information in IRIG-B is inserted into the audio channel of digital TV. IRIG-B delay correction hardware is developed to correct the time difference between the time signal received from the satellite and the reference atomic clock on the ground. A standard DVB-S receiver and satellite antenna is sufficient to decode the time signal, omitting the use of any special equipment for the end user.
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When CubeSat projects are a useful means by which universities can engage their students in space-related activities. TURKSAT-3USAT is a three-unit amateur radio CubeSat jointly developed by the Space Systems Design and Test Laboratory... more
When CubeSat projects are a useful means by which universities can engage their students in space-related activities. TURKSAT-3USAT is a three-unit amateur radio CubeSat jointly developed by the Space Systems Design and Test Laboratory and the Radio Frequency Electronics Laboratory of Istanbul Technical University (ITU), in collaboration with TURKSAT, A.S. company as well as the Turkish Amateur Technology Organization. It was launched on April 26, 2013 as a secondary payload on a CZ-2D rocket from China’s Jiuquan Space Center to an altitude of approximately 680 km. The mission of the satellite has two primary goals: (1) to voice communication at Low Earth Orbit (LEO) and (2) to educate students by providing hands-on experience. TURKSAT-3USAT was designed to sustain a circular, near sun-synchronous LEO, and has dimensions of 10 x 10 x 34 cm3. Within the course of this paper, TURKSAT-3USAT’s thermal control will be addressed. TURKSAT-3USAT’s thermal control model was developed using T...
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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... 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.
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The travelling wave tube is a critical electronic equipment for satellite data transmission and one of the highest dissipative equipment in the satellite. The travelling wave tubes generate approximately 70% of payload waste heat at... more
The travelling wave tube is a critical electronic equipment for satellite data transmission and one of the highest dissipative equipment in the satellite. The travelling wave tubes generate approximately 70% of payload waste heat at geostationary earth orbit satellite. Therefore, thermal management of travelling wave tube is one of the key aspects for satellite applications. The demand for higher power travelling wave tubes and limitations in satellite thermal design led to choose between the conduction and/or radiation cooled travelling wave tube. The aim of this study is to make a selection of the conduction and/or radiation cooled travelling wave tube. INTRODUCTION Heat dissipation has become a significant challenge for satellite manufacturers. Therefore, managing waste heat generated from the satellite becomes one of the critical issues at the early stage of the satellite project. For geostationary orbit satellites, most of the waste is generated by the payload which includes in...
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This paper addresses design and analysis of 3U CubeSat satellite thermal control system. The main goal of this study is to ensure all the components will operate in their operating range of temperatures. A thermal control system of a 3U... more
This paper addresses design and analysis of 3U CubeSat satellite thermal control system. The main goal of this study is to ensure all the components will operate in their operating range of temperatures. A thermal control system of a 3U CubeSat at an altitude 600 km with an inclination of 98o is presented. 3U CubeSat is designed for a circular, near sun synchronous Low Earth Orbit. The dimensions of 3U CubeSat is 10cm x 10cm x 30cm and a weight of 4kg. The thermal model of CubeSat was built in ThermXL. The thermal control analysis of 3U CubeSat’s passive thermal control system has been conducted. A temperature distribution of the CubeSat was computed. Based on the results, the temperatures at hot case were within the range of operating but the temperatures at cold case were low. Therefore, the results show that temperatures are highly sensitive to surface coating of the CubeSat. Choosing the surface coating at the early stage of the design is recommended.
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Thermal management is a challenging engineering problem for CubeSats due to the limited available volumes restricting the thermal control applications. Therefore, performing thermal modeling and analyses of these small satellites is very... more
Thermal management is a challenging engineering problem for CubeSats due to the limited available volumes restricting the thermal control applications. Therefore, performing thermal modeling and analyses of these small satellites is very crucial for applying proper thermal control measures to maintain safe operating conditions in space. Despite the growing interest in this field, there are still a limited number of studies investigating the thermal behavior of CubeSats. In this paper, surface temperature profiles of 1U, 2U, 3U, 5U, 6U, and 12U sized CubeSats are simulated for varying low earth orbits. The effects of altitudes changing from 400 km to 2000 km and the beta angles changing from 0 to 75 deg are analytically investigated. Not only the coatings with different absorptance and emissivity values but also different amounts of internal heat dissipations are examined to reveal their impact on the thermal balance of satellites. Results demonstrate surface temperatures are highly ...
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Temperature constantly changing across space hence low and high temperature occurs on geostationary orbit (GEO) communication satellites by the impact of environmental heat loads. Thus, the thermal control analysis becomes very important... more
Temperature constantly changing across space hence low and high temperature occurs on geostationary orbit (GEO) communication satellites by the impact of environmental heat loads. Thus, the thermal control analysis becomes very important fact to protect GEO satellites from the space environmental effects throughout launch and lifetime. In this study, the numerical models will be shown by thermal analysis with respect to absorptivity values, emissivity values, view factor etc. within desired temperatures of the equipment. Solar flux effects have taken into account. Thermal uncertainty values are used to analyze the thermal control for the communication satellites. One of the important parameters for thermal control optimization is material selection. As a result of this study, a selection of materials of satellite thermal design will be emphasized how important and effective it is.
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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... 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.
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Models used for the design of thermal systems often lead to non-linear equations which can be converted to linear systems. In this paper, a new algorithm is described for the solution of linear equation systems which have normal or... more
Models used for the design of thermal systems often lead to non-linear equations which can be converted to linear systems. In this paper, a new algorithm is described for the solution of linear equation systems which have normal or ill-conditioned form A new algorithm and the Gauss-Seidel method were used for two-stage air compression with an inter-cooler. The solutions obtained by using two different methods are compared.
TUSAT is a prospective Turkish Communication Satellite designed for providing mainly data communication and broadcasting services through Ku-Band and C-Band channels. Thermal control is a vital issue in satellite design process.... more
TUSAT is a prospective Turkish Communication Satellite designed for providing mainly data communication and broadcasting services through Ku-Band and C-Band channels. Thermal control is a vital issue in satellite design process. Therefore, all satellite subsystems and equipments should be maintained in the desired temperature range from launch to end of maneuvering life. The main function of the thermal control is to keep the equipments and the satellite structures in a given temperature range for various phases and operating modes of spacecraft during its lifetime. This paper describes the thermal control design which uses passive and active thermal control concepts. The active thermal control is based on heaters regulated by software via thermistors. Alternatively passive thermal control composes of heat pipes, multilayer insulation (MLI) blankets, radiators, paints and surface finishes maintaining temperature level of the overall carrier components within an acceptable value. The...
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Aluminyum curuflari birincil ve ikincil aluminyum uretim sonucu olusan atiklardir. Bu atiklar beyaz ve siyah curuf olarak adlandirilir. Beyaz curuf daha fazla aluminyum metali ihtiva etmektedir. Icerdigi metal miktari %15-70 arasinda... more
Aluminyum curuflari birincil ve ikincil aluminyum uretim sonucu olusan atiklardir. Bu atiklar beyaz ve siyah curuf olarak adlandirilir. Beyaz curuf daha fazla aluminyum metali ihtiva etmektedir. Icerdigi metal miktari %15-70 arasinda degismektedir. Kara curuf ise %12 ila 18 arasinda aluminyum metali ve aluminyum oksit karisimi ihtiva etmektedir. Bu curufun icerisinde yuksek miktarda (%40’ dan daha fazla) tuz bulunmaktadir. Tehlikeli atik olan aluminyum curuflari icerisindeki tuzlar yikanmak suretiyle alinmaktadir. Curuf icindeki silisyum dioksit, karbon ve nem iceriginin TS 13644 uygun olmasi temin edilmektedir. Icerisindeki tuzlardan arindirilan curuf, aluminyum metali ve aluminyum oksit miktarlarina gore gruplandirilmaktadir. 10-100 mm boyutlarinda pelet veya 2-100 mm arasinda parcacik boyutlarinda flaks olarak uretilmektedir. Celik endustrisi icin deoksidasyon ve curuf cokturucu urun olan flaks elde edilirken, yikama sonucunda olusan kimyasal reaksiyon sonucunda gazlar aciga cikm...
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... of the particles exiting the generator was moni-tored using a TSI 3375 Process Aerosol Monitor. ... 3.1.3 PIV analysis A combination of numerical effects and image parameters influence the uncertainty ... were tested, such as the... more
... of the particles exiting the generator was moni-tored using a TSI 3375 Process Aerosol Monitor. ... 3.1.3 PIV analysis A combination of numerical effects and image parameters influence the uncertainty ... were tested, such as the standard kx model, the shear stress transport (SST) k ...
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The cooling of the turbine blades in different parts of the turbine is carried out using different cooling techniques. Approximately 20% of the air produced in compressors is used in cooling systems. The air is sent into the wing through... more
The cooling of the turbine blades in different parts of the turbine is carried out using different cooling techniques. Approximately 20% of the air produced in compressors is used in cooling systems. The air is sent into the wing through the internal channels. It travels through the outer profile of the wing and is vented through the far edge of the wing. The cooling process is then completed. Among the applied cooling techniques are internal cooling, surface air film forming, and jet impingement cooling techniques. Sometimes U-shaped cooling channels are utilized for internal cooling to take place in the wing. An attempt to increase the cooling performance has been made with the utilization of wings (rips) at various angles. The change in the Nu number and the heat transfer coefficient on the channel surface as well as the impact of positioning 90° and 45° blades on a U-shaped 180° smooth (straight) channel on the cooling performance for three different Reynolds numbers (22000, 275...
Increasing payload power over the years is essential. This creates more dissipation on the satellite. The size of the satellite increases with increased payload dissipation. Even though there are many launchers which are available on the... more
Increasing payload power over the years is essential. This creates more dissipation on the satellite. The size of the satellite increases with increased payload dissipation. Even though there are many launchers which are available on the market, selecting the launcher and choosing the right dimension of the satellite is important for preliminary design of the satellite. Therefore, A Practical Launcher Thermal Analysis Tool for 3-Axis Stabilized Spacecraft Type on the Geostationary Satellite was developed. The aim of this tool is to estimate satellite dimension with the launcher type according to given satellite payload dissipation based on 3-axis stabilized spacecraft type. In this tool, the satellite uses the north and south panel as radiative areas. The rest of the satellite is covered by the insulation. Solar array dimensions and antennas are also considered as main parameters. The Practical Launcher Thermal Analysis Tool for 3-Axis Stabilized Spacecraft Type on the Geostationary...