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• Derleme MakaleYalnız künye2026/r/gumushane/13432
  A review study of recent advancements in polymer heat exchanger technology in the aspect of heat transfer

  Celen, Ali; Budak, Selahattin; Celen, Pınar; Dalkılıç, Ahmet Selim

  Many applications use metallic heat exchangers, but some operating conditions, such as desalination, exhibit wear and corrosion problems. Thus, it is important to develop and use alternative materials to metals for such conditions. Although polymers have low thermal conductivity, corrosion resistance, cost-effectiveness, and lightweight, polymer heat exchangers can be constructed to overcome this problem. They were introduced in the last decades; advancements in 3D printing technology help manufacture complex, novel, and thin heat transfer surfaces. Although review studies are limited, recent research has not explored heat transfer-based reviews of heat exchangers produced by additive manufacturing and polymer hollow fibre methods. In this study, polymer heat exchanger works were reviewed and classified according to tube diameter as polymer and polymeric hollow fibre heat exchangers as the most updated ones. Generally, the studies focused on the thermal performance of heat exchangers constructed with metal and polymer materials, and the results were compared to determine the usability of polymer-based ones. As a result, polymeric hollow fibre heat exchangers may compete with metallic ones due to low wall resistance and enhanced heat transfer surface area because of the development of manufacturing technology. Also, the cost and weight of polymeric hollow fibre exchangers are lower, and they can be operated under corrosive conditions. Finally, it is obvious that increased research is needed to enhance the properties of polymer materials to increase the performance of this type of heat exchanger.

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• MakaleAçık Erişim2026/r/gumushane/12155
  Carbon footprint assessment and reduction strategies of a university campus in Turkey

  Türle, İbrahim; Celen, Pınar

  As key institutions and significant energy consumers, universities have a critical responsibility to lead efforts in energy efficiency and renewable energy use to reduce their environmental impact. In this regard, the Gümüşhane University carbon probe has produced the first study that makes it possible to identify the sources of greenhouse gas emissions and provides the opportunity to track, measure, and suggest reduction strategies in the years to come. The carbon footprint of Gümüşhane University from 2017 to 2023 has been calculated and examined in this paper. The IPCC and DEFRA conversion factors served as the foundation for the computations. The results showed that the university's use of natural gas and electricity was responsible for almost all of its carbon emissions. According to the IPCC and DEFRA, the 2017 emissions were 4999.93 and 4667 tCO2e, respectively. Following a move to online instruction in 2020, emissions decreased to 3894 tCO2e under DEFRA and 4365.44 tCO2e under IPCC. However, as campus life resumed its pre-pandemic pace in 2022 and 2023, emissions rose again, surpassing 5252.04 tonnes of CO₂e by 2023 using the IPCC method and 4042 tonnes of CO₂e using the DEFRA method. These results suggest that universities need to focus on their energy consumption patterns in order to reduce their carbon emissions, for example by placing greater emphasis on renewable energy sources, energy efficiency, and balanced consumption. The outcomes of this research will act as a guideline not only for Gümüşhane University to help it reach its sustainability goals, but also for other university administrations when formulating effective carbon reduction strategies, and for institutions seeking to measure or benchmark their environmental performance.

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• MakaleAçık Erişim2024/r/gumushane/19985
  Thermal Power Plant Performance Analysis by Estimating Boiler Efficiency via Indirect Method: A Case Study

  Celen, Pinar; Erdem, Hasan Hüseyin

  In this paper, a coal (lignite) fired thermal power plant having capacity of 160 MW is taken into consideration and the impact of condenser pressure, moisture content of lignite, excess air coefficient, the efficiency of turbine pressure and heater numbers on power plant thermal efficiency is investigated. It is aimed to determine the performance losses of each equipment by means of thermodynamics and economic analysis. In this scope, it is expected that the power plant operator will be able to evaluate the reduction potential of equipment performance losses and ensure more effective use of the power plants by correctly planning the maintenance and rehabilitation needs and time. In the calculations, the boiler efficiency was determined with EN 12952-15 standard (indirect method) since this method has higher accuracy in coal-fired boilers. It is seen that the condenser pressure and excess air coefficient increments have no significant impact on power plant efficiency compared to moisture content of lignite, excess air coefficient, efficiency of turbine pressure and heater numbers. The significant effect is observed for fuel moisture content which rises from 22% to 47% and the power plant efficiency falls from 40% to 28%. The variation of the power plant thermal efficiency in case of failure of heaters is investigated and the power plant efficiency has decreased from 40.17% to 36.09% when the pre-heaters are no longer in to be in use because of any reason. In addition, revenue losses are estimated for each main equipment efficiency reduction for better use of power plant capacities and electricity lowering production costs.

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• MakaleAçık Erişim2022/r/gumushane/16799
  Energy and Exergy Analysis of Solar Collectors Having Different Tilt Angles: Case Study of Erzincan City

  Kaba, Muhammet Yasin; Kurnuc Seyhan, Aslihan; Celen, Pinar; Celen, Ali

  Solar collectors are frequently used in domestic water heating applications. In the design stage, the positioning of solar collector with suitable title angle is important in order to utilize from sun energy efficiently. In this study, the effect of tilt angle of a solar collector located to Erzincan city on monthly/daily average radiation values, water outlet temperature, energy and exergy efficiencies are theoretically investigated. It is seen that the maximum and minimum values of optimum tilt angles are 63 degrees ve 0 degrees for December and June, respectively. Tilt angles which are suggested for Erzincan (27.14 degrees) and calculated are compared for daily average hourly radiation values and it is seen that the maximum variation is 26% for January. In addition, energy and exergy efficiencies of solar collector are estimated and the maximum efficiencies are determined as 74.2% ve 9.7% for optimum tilt angles.

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• MakaleYalnız künye2022/r/gumushane/14919
  Evaluation of single particle drying characteristics using drying models and curve fitting

  Celen, Pinar; Erdem, Hasan H; Pusat, Saban

  In this study, Turkish lignite dried with hot air and superheated steam was experimentally investigated. Drying experiments were carried out at 120°C drying temperature and atmospheric pressure. Mass, center and surface temperature changes of lignite having a diameter of 30 mm were continuously measured. Hot air and superheated steam drying methods were compared, and it was found that, because of condensation in the initial stage of superheated steam, the moisture content of the lignite sample temporarily increased. On the contrary, the moisture content of the lignite sample dramatically reduced on drying with hot air. Six different thin-layer models describing the drying kinetics of lignite were fitted to the experimental data, with the Pusat model giving the best predictions with superheated steam drying and the Midilli model giving the best predictions with hot air drying of a single particle.

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• MakaleYalnız künye2021/r/gumushane/14617
  An experimental investigation of single lignite particle dried in superheated steam and hot air

  Celen, P.; Erdem, H.H.

  In lignite (low-rank coal)-fired thermal power plants, thermal efficiency can be improved by decreasing the lignite moisture. The lignite moisture can be removed by using superheated steam and hot air as drying fluids. In this study, Turkish (Afşin-Elbistan) lignite having a diameter of 30 mm was dried with superheated steam and hot air at temperatures of 117°C under atmospheric pressure. The changes in its weight and temperature with time were observed, and the drying characteristics were obtained during the drying process. In the first period of drying, which is called heating period, the drying rate of superheated steam is higher than hot air in contrary to during constant-rate period. Moreover, the experiments revealed that less time is required to heat lignite sample with superheated steam compared to hot air.

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• Derleme MakaleAçık Erişim2018/r/gumushane/10289
  A REVIEW OF FLOW BOILING IN MINI AND MICROCHANNEL FOR ENHANCED GEOMETRIES

  Çebi, Alican; Celen, Ali; Donmez, Aydin Haci; Karakoyun, Yakup; Celen, Pinar; Cellek, Mehmet Salih; Dalkiliç, Ahmet Selim; Taner, Tolga; Wongwises, Somchai

  Flow boiling researches in enhanced geometries practiced recently have been summarized in this review. Classical approximations in macroscale flows have not applied to the flows with small hydraulic diameters, so, this subject has been paid attention by the researchers. Application areas of these structures are increasing continuously due to cooling need in small confined spaces. The related studies have been reviewed in a chronological manner and their parameters have been given in a table in order for the researchers to observe the scientific duration regarding the progresses on this subject. Almost all papers on this subject have been produced after 2000, therefore, this subject is considered as an actual one to improve and worth to study in the literature. This study can not only be evaluated as the beginning argument for the researchers involved in flow boiling process in mini and microchannel, but it also consists of new works on the investigated subject.

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