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Öğe Exploring the impact of inner and middle channel geometries on the melting rate of PCM-metal foam composition in a triplex tube heat exchanger(Elsevier, 2024) Kursun, Burak; Balta, Mehmet; Karabulut, KorayTriplex tube heat exchangers (TTHXs) are devices suitable for storing thermal energy with PCM because they shorten the melting and solidification periods. Studies in literature have revealed that pipe geometries significantly affect the melting performance of PCM in thermal energy storage with TTHX. In the pipe designs carried out in these studies, convection in the heat transfer fluid (HTF) and the heat transfer surface areas of the pipes were considered. However, in addition to convection in the HTF, heat transfer by conduction and convection within the PCM also significantly affects the melting performance. The novelty of this study was to investigate the effects of inner and middle channel combinations with different geometries in TTHX on conduction and natural convection mechanisms in PCM combined with metal foam. Numerical analyses were carried out for nine inner-middle channel combinations with three different metal foam porosity values (epsilon = 0.85, 0.90 and 0.95). At porosity values of 0.85 and 0.90, the highest melting rate was achieved with the triangle-triangle inner-middle channel combination within a certain period, and the charging time was shortened by 16.67 % and 14.44 %, respectively, compared to the base case (circle-circle). For the porosity value of 0.95, it was observed that the most suitable channel combination for melting performance was circle-circle, as natural convection flow became more dominant in heat transfer in liquid PCM. At the porosity value of 0.95, the charging time with TTHX containing the circle-circle combination decreased by values ranging from 29.75 % to 59.86 % compared to other combinations.Öğe Farklı yapılara sahip binalardaki akış yapılarının sayısal olarak incelenmesi(Cumhuriyet Üniversitesi, 2016) Balta, Mehmet; Fertelli, AhmetBu çalışmada, farklı bina modelleri üzerindeki rüzgâr etkileri araştırılmıştır. Çalışmanın ilk bölümünde tekli bina modeli ile farklı ara mesafelerde ikili, üçlü ve dörtlü bina modelleri etrafındaki akış alanları incelenmiştir. Çalışmanın ikinci bölümünde ise tekli bina modeli için, farklı rüzgâr yönleri (15°, 30°, 45°) ve farklı çatı eğimlerinde (15°, 30°, 45°) bina üzerindeki rüzgâr etkileri incelenmiştir. Bina modelleri etrafındaki akış alanları üç boyutlu ve zamandan bağımsız olarak FLUENT paket programı ile hesaplanmıştır. Sayısal çözümlemede Sivas ili için atmosferik sınır tabaka hız profili oluşturulmuş ve RNG k-? türbülans modeli kullanılmıştır. Analizler sonucunda akım çizgileri, hız vektörleri, ortalama hız ve türbülans kinetik enerji dağılımları ile model yüzeylerinde ortalama basınç katsayısı dağılımları hesaplanmıştır. Çoklu binalarda binalar arası mesafenin akış alanı ve basınç katsayılarına etkisi, kritik rüzgâr açısı ve kritik çatı eğimleri tek bina için belirlenmiştir.Öğe INVESTIGATION INTO ENERGY SAVINGS IN THE RENEWAL OF THE LIGHTING SYSTEM IN UNIVERSITY CAMPUS BUILDINGS(UNIV ZAGREB FAC MECHANICAL ENGINEERING & NAVAL ARCHITECTURE, 2019) Fertelli, Ahmet; Balta, MehmetThis study shows the amount of energy savings to be achieved in electricity consumption if the current lighting system in the buildings of the Cumhuriyet University campus in Turkey is replaced with efficient lighting systems. In addition, environmental effects of energy savings are determined by calculating the amounts of CO2, SO2, NOx, CO emissions. The Life Cycle Cost (LCC) analysis is used to determine energy costs and payback periods. The calculations reveal that the use of three alternative lighting systems would lead to a substantial reduction in electricity consumption ranging between 16.5% and 40.5%, and that the payback periods of these alternative lighting systems vary between 1.9 and 5 years.Öğe Numerical Investigation of Flow Structures for Four Buildings at Different Distances(2020) Fertelli, Ahmet; Balta, MehmetIn the present study, it was aimed to compare the effects of the different distances between four buildingsplaced in a wind area on the surface pressure distributions and flow structures around the building. For thispurpose, ANSYS-FLUENT 14.0 package program was used and analyses were performed with the RNG k-?turbulence model by 3D-modelling the buildings. The distances between the buildings were initially chosen ashalf of the building height and then the same as the building height. The average wind velocity was determinedby taking the meteorological data for Sivas into consideration and the distributions of the flow line, velocityvector, turbulence kinetic energy and surface pressure coefficients were calculated for the medium height androof level of the buildings. It is observed from the results that the distances between the buildings significantlyaffected the flow structures and velocity distributions, positive pressures were effective for front surfaces in thefirst buildings and negative pressure areas were formed in the rear surfaces and roofs.
