Yazar "Bulut, Murat" seçeneğine göre listele

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    Analytical Investigation of Surface Temperatures for Different Sized CubeSats at Varying Low Earth Orbits
    (Asme, 2023) Atar, Cihan; Aktas, Metin; Sozbir, Nedim; Bulut, Murat
    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 dependent on those variables. The amount of heat absorbed by satellite panels is affected by the different sizes of CubeSats, different coating properties of panels, and different orbital configurations. The outcomes of this research may be beneficial especially in the early design phase for designing small satellites and selecting proper orbital configurations.
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    Experimental study of heat transfer in a microchannel with pin fins and sintered coatings
    (Taylor and Francis Ltd., 2023) Bulut, Murat; Shukla, M.; Kandlikar, S.G.; Sözbir, N.
    Increasing processing capacity without modifying the size of electronic devices has made thermal management important in the electronic industry. Commercialized thermal management, such as in a conventional air cooling system, is insufficient for electronic devices with high heat flux dissipation. Pool boiling is a better method for heat transfer because it can dissipate a substantial amount of heat at low wall superheats. This study focused on heat transfer enhancement using passive approaches, including nanostructures and microporous sintered surfaces over open microchannel surfaces and microchannels with pin-fins. In the present work, seven structures were studied in pool boiling, wherein experiments elucidated the effects of microchannels, sintered, and pin fins (micropillar) on boiling heat transfer from a copper chip in a pool of degassed water. Boiling performance is ascertained via critical heat flux (CHF) and heat transfer coefficient (HTC). The best heat transfer performance showed a heat flux of 243.75W/cm2 at 15.46°C on the pin-fins chip, which was 1.9 times the heat flux of the plain chip. The highest HTC was 181.03 kW/(m2 oC) at a heat flux of 172.61 W/cm2 for the microchannel with single pin-fins. The HTC enhancement was 2.8 times greater than the plain surface. It was found experimentally that HTC and CHF improved on all modified surfaces compared to the plain copper chip baseline. © 2023 Taylor & Francis.
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    Modeling and Analysis of Battery Thermal Control in a Geostationary Satellite
    (2022) Bulut, Murat; Sözbir, Nedim
    Battery technology has been used for geostationary satellites since the first satellite sputnik-1 was launched in 1957. The majority of larger geostationary satellite’s 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 oC and 32.7 oC. The temperature during the battery module was not greater that its qualification temperature results.
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    A novel approach to estimating dimensions of three-axis stabilized communication satellites with optimal heat transfer
    (Springer, 2023) Bulut, Murat; Sözbir, Nedim
    One of the most challenging tasks at the early stage of satellite programs is fitting various stowed satellite configurations within different launcher envelopes to dissipate heat from the satellite. To overcome this thermal challenge, this paper proposes a practical launcher thermal analysis tool (PLTAT). The aim of this tool is to predict satellite dimension and the launcher type based on the heat dissipation requirement. The study focused on three-axis stabilized geostationary communications satellites, and north and south panels were used for heat dissipation by radiation. The remaining panels of the satellite were covered by a multilayer insulation. In the calculations, the solar arrays were placed at the north and south panels while antennas were placed at the east and west panels. The values obtained by the Excel-based VBA were compared with flying GEO satellites. Heat dissipation values calculated using PLTAT were compared with existing radiative area results. The minimum difference between the existing values and the PLTAT calculated values was 0.63%, whereas the maximum difference was 12.04%. The results from calculated PLTAT radiative areas were in agreement with existing radiative areas. Thus, PLTAT can be an alternative and useful approach when designing three-axis stabilized geostationary communications satellites.
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    Space Activities and the Simultaneous Development of the Economy in Türkiye
    (Duzce University, 2024) Sözbir, Nedim; Bulut, Murat; Gülgönül, Şenol; Kuzu, Lokman; Dur, Osman
    As space technologies have become an integral part of our daily lives, they have profoundly influenced the course of human civilization since 1957. These technologies have provided humanity with many remarkable insights. Therefore, they have an important role in modern society. Satellite technology is not only vital for military and defence but also for civil applications such as transportation, communication, disaster management, agriculture planning, land, and urban planning. These applications make the space sector an engine of economic growth having advanced and the state-of-the art technology. Technological advances in space continuously benefit the citizens of developed countries. The space economy is defined as all the actions and resources that produce value and benefit to people through exploration, research, knowledge, management, and utility of space. Through satellite communications, navigation systems, earth observation missions, space science and technology research, employment is created, economic growth is achieved, and many industries become more competitive in worldwide economic market. Spinoff companies are born from space activities. In 1994, the Türkiye had its first communication satellite TURKSAT 1B built by Aerospatiale; thus, Türkiye entered the space field being an operator in its region. After millennium, the Turkish space industry has ramped-up by developing its dedicated communication and observation satellites, and their subsystems and creating a launcher system for microsatellites. Türkiye is now developing space technology more comprehensively. This article describes recent developments of space activities and future work in Türkiye. In the article, the strategies in other countries in space technologies are also discussed and suggestions are made for space technology education, development of space economy and regulation of space activities for Türkiye.
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    The Emittance and Absorptance of External Surfaces Values Effect for Payload Panels on Geostationary Orbit Satellite: Thermal Analysis Studies
    (Ataturk University, 2024) Bulut, Murat; Sözbir, Nedim
    One of the most important parameters in the dimensioning stages of communication satellites is the calculation of the areas where the heat to be released into space is located. The satellite thermal control system calculates these areas. Thermal analyses are performed for the north and south panels where the payload equipment is located in three-axis geostationary satellites. It is important to calculate these areas where the heat to be released into space is located correctly. In this study, thermal analysis calculations were performed for a three-axis geostationary satellite with an area of 1 to 10 m2. In the calculations, the absorptance of external surfaces at the end of the satellite's life was calculated by considering 0.27. The radiator area temperature was taken as 30 oC in the calculations.
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    Türksat 3A Uydu Proje Kapsamında Türksat Teknoloji Transfer Programı
    (Düzce Üniversitesi, 2023) Bulut, Murat; Sözbir, Nedim
    Türkiye uydu işletmeci olma kararını 1989 yılında ilk defa haberleşme uydu satın almak için ihaleye çıkarak yapmıştır. 1994 yılında Türksat 1A uydusunun fırlatılmasından 2006 yılında Türksat 3A uydu üretimine kadar uydular satın alınmakla birlikte teknoloji transferi yapılmamıştır. Türksat 3A proje kapsamında ilk defa uydu teknoloji transferi programı TÜRKSAT ile Alcatel Alenia Space arasında anlaşma yapılarak başlamıştır. Türksat Teknoloji Transfer Programı (TTTP) çerçevesinde Fransa üretilen Türksat3A uydu üretim projesine 16 mühendis katılım sağlamıştır. TÜRKSAT 3A projesi kapsamında yerli haberleşme uydusu tasarım projesi olan TUSAT'a başlandı. TUSAT haberleşme uydusu tasarımı (Ön Tasarım İncelemesi (PDR düzeyi)) 2012 yılında tamamlanmıştır. Bu çalışmada, TTTP’da yapılan çalışmalar ve bu çalışmalar sonrası ülkemizde hali hazırda uydu teknolojileri konusundaki katkıları hakkında bilgiler verilecektir.