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Öğe Application of nanofluid flow in entropy generation and thermal performance analysis of parabolic trough solar collector: experimental and numerical study(Springer, 2023) Ekiciler, Recep; Arslan, Kamil; Turgut, OguzThis study investigates numerically and experimentally the flow and heat transfer characteristics of ZnO/EG-H2O nanofluid flow in a parabolic trough solar collector at different flow rates (between 20 lit h(-1) and 80 lit h(-1)) and nanoparticle volume fractions (phi = 1%, 2%, 3%, 4%). The effects of changes in parameters such as absorbed and heat loss parameters, collector efficiency, useful energy, and temperature differences between outlet and inlet have been investigated in the context of experimental results. To obtain meaningful results in the numerical study, a non-uniform heat flux distribution on the collector absorber has been generated by the Monte Carlo Ray Tracing method (MCRT) using the commercial code SOLTRACE. Friction factor, entropy generation, PEC number, Nusselt number, and Bejan number are the parameters studied. The ZnO/EG-H2O nanofluid significantly improves the efficiency of the collector, based on the findings obtained. The highest usable energy has been obtained at the flow rate of 80 lit h(-1) with 4% ZnO/EG-H2O nanofluid. The results suggest that the temperature differential rises when ZnO/H2O has been used compared to EG-H2O. Moreover, when ZnO/EG-H2O is used with the flow rate of 80 lit h(-1) and a volume fraction of 4% of nanoparticles, the Nusselt number increases by about 100% compared to EG-H2O as the working fluid. There is a negligible increase in the overall entropy production when ZnO/EG-H2O is utilized as opposed to the base fluid. Thus, the greatest possible nf may be suggested for parabolic trough solar collector. The goal of this study is to use the findings of ZnO/EG-H2O nanofluid research to parabolic trough solar collectors. The experimental data show that compared to traditional fluid, utilizing nanofluid results in significantly improved thermal performance. In this situation, it seems that nanofluid would be the best option.Öğe Convective Heat Transfer Investigation of a Confined Air Slot-Jet Impingement Cooling on Corrugated Surfaces With Different Wave Shapes(Asme, 2019) Ekiciler, Recep; Cetinkaya, Muhammet Samet Ali; Arslan, KamilIn this study, air jet impingement on flat, triangular-corrugated, and sinusoidal-corrugated surfaces was numerically investigated. Bottom surface was subjected to constant surface temperature. Air was the working fluid. The air exited from a rectangular shaped slot and impinged on the bottom surface. The Reynolds number was changed between 125 and 500. The continuity, momentum, and energy equations were solved using the finite volume method. The effect of the shape of bottom surface on heat and flow characteristics was investigated in detail. Average and local Nusselt number were calculated for each case. It was found out that Nusselt number increases by increasing the Reynolds number. The optimum conditions were established to get much more enhancement in terms of performance evaluation criterion (PEC). It was revealed that the shape of the cooling surface (bottom wall) influences the heat transfer substantially.Öğe CuO/WATER NANOFLUID FLOW OVER MICROSCALE BACKWARD-FACING STEP AND ANALYSIS OF HEAT TRANSFER PERFORMANCE(Begell House Inc, 2018) Ekiciler, Recep; Arslan, KamilThree-dimensional numerical simulation of steady-state laminar forced convection flow of a CuO/water nanofluid and heat transfer in a duct having a microscale backward-facing step (MBFS) are presented in this study. The study was conducted for determining the effects of nanoparticle volume fraction on the flow and heat transfer characteristics. The Reynolds number ranged from 100 to 1000. The step height and inlet height of the duct were 600 mu m and 400 mu m, respectively. The duct expansion ratio was 2.5. The downstream wall was subjected to a constant and uniform heat flux, whereas the other walls were insulated. The nanoparticle volume fraction varied from 1.0% to 4.0%. The Nusselt number and Darcy friction factor were obtained for each nanoparticle volume fraction. Plots of velocity streamlines were analyzed. It was found from the results of numerical simulation that the Nusselt number increases with increasing nanoparticle volume fraction and Reynolds number. The nanoparticle volume fraction does not exert any substantial effect on the Darcy friction factor and the length of the recirculation zone. Moreover, the performance evaluation criterion (PEC) was analyzed for nanoparticle volume fractions of 1.0%, 2.0%, 3.0%, and 4.0% of CuO. It was obtained that the volume fractions of 4.0% has the highest PEC in terms of heat transfer. It was obtained that while heat transfer for nanoparticle volume fraction of 30% and 4.0% the friction factor is superior for nanoparticle volume fraction of 1.0% and 2.0% due to the PEC number.Öğe Effect of hybrid nanofluid on heat transfer performance of parabolic trough solar collector receiver(Springer, 2021) Ekiciler, Recep; Arslan, Kamil; Turgut, Oguz; Kursun, BurakIn this study, three-dimensional heat transfer and flow characteristics of hybrid nanofluids under turbulent flow condition in a parabolic trough solar collector (PTC) receiver has been investigated. Ag-ZnO/Syltherm 800, Ag-TiO2/Syltherm 800, and Ag-MgO/Syltherm 800 hybrid nanofluids with 1.0%, 2.0%, 3.0%, and 4.0% nanoparticle volume fractions are used as working fluids. Reynolds number is between 10,000 and 80,000. The temperature of the fluid is taken as 500 K. The C++ homemade code has been written for the nonuniform heat flux boundary condition for the outer surface of the receiver. Variations of thermal efficiency, heat transfer coefficient, friction factor, PEC number, Nusselt number, and temperature distribution are presented for three different types of hybrid nanofluids and four different nanoparticle volume fractions with different Reynolds numbers. Also, the graphs of the average percent increase according to Syltherm 800 are given for the working parameters. According to the results of the study, all hybrid nanofluids are found to provide superiority over the base fluid (Syltherm 800) with respect to heat transfer and flow features. Heat transfer augments with the growth of Reynolds number and nanoparticle volume fraction. Thermal efficiency, which is one of the important parameters for PTC, decreases with increasing Reynolds number and increases with the increasing volume fraction of nanoparticle. It is obtained that the most efficient working fluid for the PTC receiver is the Ag-MgO/Syltherm 800 hybrid nanofluid with 4.0% nanoparticle volume fraction.Öğe Effect of shape of nanoparticle on heat transfer and entropy generation of nanofluid-jet impingement cooling(Taylor & Francis Inc, 2020) Ekiciler, Recep; Cetinkaya, Muhammet Samet Ali; Arslan, KamilAl2O3/water nanofluid has been numerically examined for the first time with different nanoparticle shapes including, cylindrical, blade, brick, platelet and spherical, on the flat and triangular-corrugated impinging surfaces. The volume fractions of 1.0%, 2.0% and 3.0% nanoparticles have been used. The Reynolds number is between 100-500 depending on the slot diameter. The finite volume method is utilized to determine the governing equations. The study is analyzed to determine how the flow features, heat transfer features and entropy production were affected by the diversity of nanoparticle shape, nanoparticle volume fraction, and shape of impinging surface. Darcy friction factor and Nusselt number are studied in detail for different conditions. The temperature contours are presented in the case of different nanoparticle volume fractions, nanoparticle shapes and both impinging surfaces. The results of the study suggest that the nanoparticle shape of the platelet shows the highest heat transfer development due to the thinner thermal boundary layer. Heat transfer augments with increasing volume fraction of nanoparticles. In addition, the study is consistent with the results of the literature on heat transfer and flow properties.Öğe EFFECT OF THE NANOFLUID FLOW AND EXTENDED SURFACES ON AN ABRUPT EXPANSION TUBE REGARDING THERMODYNAMIC IRREVERSIBILITY(Begell House Inc, 2024) Pazarlioglu, Hayati Kadir; Ekiciler, RecepNumerous scientists have examined circular dimpled surfaces, tubes, and other approaches for enhancing heat transfer. Moreover, the dimples' angle of attack has a substantial effect on the tube's flow and thermal features. This numerical study presents a novel approach to enhancing heat transfer rate in a tube subjected to constant heat flux by incorporating a surface dimpling strategy and evaluates three different tube layouts with elliptical dimpled fins for different working fluids such as DW and Al2O3/DW nanofluid (phi = 0.5-1.0%) by using ANSYS Fluent v2020R2 under laminar flow conditions. Under identical circumstances, the thermal performances of proposed designs are compared to those of a smooth tube, and the influence of the elliptical dimpled fin angle of attack on these parameters is determined for different Reynolds numbers (1000 <= Re <= 2000). When comparing the Nusselt number of a tube with/without elliptical dimpled fins, it is found that EDT 1 performed better. Lower Reynolds numbers are shown to result in a greater friction factor. Besides, elliptical dimpled fins promote flow mixing within the tube and the establishment of a thermal boundary layer. At a 135 degrees attack angle (EDT 1), the 1.0% Al2O3/DW nanofluid is found to be the best-performing nanofluid in the dimpled tube, improving Nu by up to 44.56%. Furthermore, ff presented an increase of 29.18% when comparing ST and EDT 1 flowing 1.0% Al2O3/DW at Re = 2000, while total S-gen is diminished by 37.75% in the same conditions.Öğe THE EFFECT OF VOLUME FRACTION OF SiO2 NANOPARTICLE ON FLOW AND HEAT TRANSFER CHARACTERISTICS IN A DUCT WITH CORRUGATED BACKWARD-FACING STEP(Vinca Inst Nuclear Sci, 2018) Ekiciler, Recep; Aydeniz, Emre; Arslan, KamilIn this paper, flow and heat transfer characteristics of SiO2-water nanofluid flow over a corrugated backward-facing step are numerically investigated. The numerical study is performed by solving governing equations (continuity, momentum, and energy) with finite volume method. The duct inlet and step heights are 4.8 mm. The expansion ratio is 2. The upstream wall, L-w and downstream wall, L-d, lengths are 48 cm and 96 cm, respectively. The downstream wall of the duct is subjected to a constant and uniform heat flux of 2000 W/m(2). The ranges of the volume fraction of nanoparticles and Reynolds number are 0%-3.0% and 135-240, respectively. The effects of the volume fraction of nanoparticles on the average Nusselt number, average Darcy friction factor, and velocity distribution are investigated under laminar forced convective nanofluid flow condition. It is revealed that the nanoparticle volume fraction substantially influences the heat transfer and flow characteristics. The volume fraction of 3.0% shows the highest heat transfer performance.Öğe EFFICIENCY DETERMINATION OF SOLAR CHIMNEY POWER PLANT RETROFITTED WITH NOVEL FINNED COLLECTOR UNDER REAL-TIME SOLAR IRRADIANCE(Begell House Inc, 2024) Hasan, Ibrahim Shikh; Pazarlioglu, Hayati Kadir; Arslan, Kamil; Ekiciler, RecepThis paper discusses the three-dimensional numerical study of a new finned collector integrated into the solar chimney power plant. Manzanares pilot's details, which are tower height 194.6 m, rooftop height 1.85 m, rooftop diameter 244 m, tower diameter 10.16 m, and pilot mean temperature 20 degrees C with air speed 15 m/s, are implemented in this work to check the suitability of the finned collector as a way of improvement. In order to assess the unique idea, a parametric study is done with different number of fins: 46, 33, and 25; different fin widths: 0.5, 0.25, and 0.1 m, and different fin heights: 1.2, 0.925, and 0.6 m. Therefore, optimal outputs could be obtained by the novel rooftop that is proposed in this study, where the efficient case is specified dimensionally by 46 fins, a fin width of 0.1 m, and a fin height of 1.2 m, which gives 1.674% as the station performance, 700.597 kW as the resulted power of the plant, 1790.3 as the Nusselt number, and 1.96E+14 as the Rayleigh number.Öğe Exergetic, Energetic, and entropy production evaluations of parabolic trough collector retrofitted with elliptical dimpled receiver tube filled with hybrid nanofluid(Pergamon-Elsevier Science Ltd, 2023) Pazarlioglu, Hayati Kadir; Ekiciler, Recep; Arslan, Kamil; Mohammed, Noor Adil MohammedIn this paper, a numerical study was performed on a parabolic trough collector receiver tube containing elliptical dimpled fins with different elliptical ratios (ER = 0.66-1.66) under turbulent flow regime. The C++ code was developed to perform a non-uniform heat flux on outside of the receiver tube to get approximation real working conditions. Different mono and hybrid nanofluids and their combinations with different nanoparticle volume fractions (2.0 %TiO2/Syltherm800, 2.0 %Al2O3/Syltherm800, 0.5 %TiO2-1.5 %Al2O3/Syltherm800, 1.0 %TiO2-1.0 %Al2O3/Syltherm800, and 1.5 %TiO2-0.5 %Al2O3/Syltherm800) were used as a working fluid. The study provides a detailed analysis of the hydro-thermal characteristics, exergetic, and entropy production of the parabolic trough collector. 1.5 %Al2O3-0.5 %TiO2/Syltherm800 hybrid nanofluid shows the best increase in results obtained in this study using elliptical ratio of a/b = 5/3. The use of the elliptical ratio of a/b = 5/3, the average Nusselt number increases with 38 % compared to the receiver tube without elliptical dimpled fin. Total entropy generation was reduced up to 16.82 % for the elliptical ratio of a/b = 5/3. With the inserting elliptical dimpled fins of a/b = 5/3, the Performance Evaluation Criterion was detected as 1.81 compared to while the thermal efficiency increases from 74 % to 80 % at the lowest Reynolds numbers.Öğe HEAT TRANSFER ENHANCEMENT IN AN EQUILATERAL TRIANGULAR DUCT BY USING AN Al2O3/WATER NANOFLUID: EFFECT OF NANOPARTICLE SHAPE AND VOLUME FRACTION(Begell House Inc, 2020) Ekiciler, Recep; Cetinkaya, Muhammet Samet Ali; Arslan, KamilForced convective heat transfer of an Al2O3/water nanofluid, having different shapes of nanoparticles including blade, brick, cylindrical, platelet, and spherical, flowing in a three-dimensional (3D) equilateral triangular duct has been studied numerically. The Al2O3 nanoparticle is dispersed with a ratio of 1.0%, 2.0%, and 3.0%. The Reynolds number is in the range of 100-500. A constant heat flux of 420 W/m(2) is delivered to the whole walls. The analysis is made for determining how the heat transfer and flow features are affected by different nanoparticle shapes and volume fractions. Convective heat transfer coefficient, Nusselt number, Darcy friction factor, pumping power, and performance evaluation criterion (PEC) in the duct are analyzed. The results of the study reveal that the nanoparticle shape of the platelet shows the greatest heat transfer enhancement. At the highest Reynolds number, the average Nusselt number enhances up to 25% by using platelet nanoparticle shape when compared to the pure water. Also, heat transfer in the duct increases by increasing the nanoparticle volume fraction. Also, the study is compatible with the outcomes of literature regarding heat transfer and flow features.Öğe Inclination Angles Effect on Heat Transfer and Turbulent Periodic Flow in a Duct-Mounted Flow-Inclined Baffles(Springer Heidelberg, 2023) Arslan, Kamil; Ekiciler, Recep; Onur, NevzatThis research uses computational methods to examine steady-state turbulent forced convection flow in a duct having rectangular cross-section equipped with flow-inclined baffles on the bottom wall. The aim of this study is to provide information about turbulent convective heat transfer in ducts with a roughened surface. Especially, it is intended to obtain the influence of newly designed baffles on convective heat transfer in detail. Between 1000 and 10,000, the Reynolds number is varied. The duct's hydraulic diameter is 75 mm. Air is used as the working fluid. Numerical calculations have been carried out using Ansys Fluent R18 commercial code. Governing equations have been solved iteratively. SST k-omega turbulence model has been used for solving turbulence equation. New engineering correlations have been gained from numerical calculations. In terms of the thermal enhancement factor, a number of different baffle inclination angles have been evaluated in comparison with both one another and a smooth duct. The results show that a steeper inclination angle of the baffle improves the heat transmission. Pressure drop also rises as the baffle inclination angles become steeper. In all situations, the greatest thermal augmentation factor is obtained at an inclination angle of beta = 0.41 rad, while the least is obtained at an inclination angle of beta = 0 rad.Öğe Numerical analysis of convective heat transfer and flow characteristics with nanofluids flowing over a microscale backward-facing step(Karabük Üniversitesi, 2016) Ekiciler, Recep; Arslan, KamilBu tezde, mikro boyutta geri basamak üzerinden ZnO/su, CuO/su, TiO2/su, SiO2/su ve Al2O3/su nanoakışkanlarının akışının zorlanmış taşınım ısı transfer ve akış karakteristikleri sayısal olarak incelenmiştir. Nanopartiküllerin çapı 45 nm ile 80 nm arasında değiştirilmiştir. Akışın, üç boyutlu, kararlı ve laminer şartlarda olduğu gözönüne alınmıştır (100?Re?1000). Kanalın basamaktan sonraki alt duvarına sabit ısı akısı uygulanmış ve diğer duvarları yalıtılmıştır. Kanalın basamaktan sonraki ve önceki uzunlukları sırasıyla 0.15 m ve 0.10 m olarak ele alınmıştır. Toplam kanal yüksekliği 1000 µm ve genişliği ise 1200 µm'dir. Sayısal analizler, her bir nanoakışkanın farklı nanopartikül hacimsel oranı (? = 1.0- 4.0%) ve farklı genişleme oranları (ER=1.25, 1.67 ve 2.50) için uygulanmıştır. Sayısal hesaplamalardan, Nusselt sayısı ve Darcy sürtünme faktörü değerleri elde edilmiştir. Bunlara ek olarak, hız ve sıcaklık profilleri analiz edilmiştir. Sonuç olarak, Nusselt sayısının artan nanopartikül hacimsel oranı ve Reynolds sayısı ile arttığı gözlenmiştir. Bütün genişleme oranlarında, %4.0 nanopartikül hacimsel oranına sahip Al2O3/su nanoakışkanın en yüksek Nusselt sayısına sahip olduğu tespit edilmiştir. Nusselt sayısının, azalan genişleme oranı ile birlikte arttığı görülmüştür. Darcy sürtünme faktörünün, artan genişleme oranı ile beraber düştüğü görülmüştür. Bununla birlikte, Darcy sürtünme faktörünün artan nanopartikül hacimsel oranından ve nanoakışkanların çeşidinden etkilenmediği anlaşılmıştır.Öğe NUMERICAL ANALYSIS OF EFFECT OF IMPINGING JET ON COOLING OF SOLAR AIR HEATER WITH LONGITUDINAL FINS(Begell House Inc, 2021) Pazarlioglu, Hayati Kadir; Ekiciler, Recep; Arslan, KamilIn this study, the effect of impinging jet cooling on solar air heater with and without longitudinal fins has been numerically investigated. The absorber plate surface of the solar air heater is modeled as a constant heat flux condition. Numerical analyses have been conducted on turbulent flow conditions (10,000 <= Re <= 50,000). The jet flow velocity has been taken constant. The effect of fin height and mass flow rate of working fluid on the thermal efficiency of the solar air heater has been analyzed in detail. Variation of the convection heat transfer coefficient as a function of Reynolds number has also been determined for finned and unfinned conditions. Temperature and local Nusselt number distributions on the absorber plate have been defined as contour graphs. It is found that the Nusselt number and thermal efficiency enhance by adding impingement jets and increasing the Reynolds number. Also, it is obtained from numerical analyses that the convection heat transfer coefficient increases with increasing the fins height. Finally, it is revealed that using impinging jets and fins enhances the efficiency and convection heat transfer up to 23.35% and 15%, respectively.Öğe PARABOLİK OLUK TİPİ GÜNEŞ KOLEKTÖRLERİNDE NANOAKIŞKAN KULLANIMININ ISIL PERFORMANSA ETKİSİNİN DENEYSEL VE SAYISAL İNCELENMESİ(2022-02) Ekiciler, RecepBu çalışmada, parabolik oluk tipi güneş kolektöründeki nanoakışkan akışının ısı ve akış karakteristikleri farklı hacimsel debilerde (20 lt/sa, 40 lt/sa, 60 lt/sa, 80 lt/sa) ve nanopartikül hacimsel oranlarında (%1, %2, %3, %4) deneysel ve sayısal olarak incelenmiştir. Deney sonuçları ışığında faydalı enerji, kolektör verimi, soğurulan ve atılan enerji parametresi, kolektör giriş-çıkış sıcaklık farkları, kaybolan enerji gibi değişimlerin kolektöre etkisi incelenmiştir. Sayısal çalışmada ise, deneysel çalışmada kullanılan akışkanlara (""EG-"" ""H"" _""2"" ""O "" ve ""ZnO/EG-"" ""H"" _""2"" ""O"" ) ilave olarak yeni nesil hibrit nanoakışkanlar ile sayısal çözümler gerçekleştirilmiştir. Bu bağlamda, üç farklı tip hibrit nanoakışkan (""Ag-ZnO/EG-"" ""H"" _""2"" ""O"" , ""Ag-Ti"" ""O"" _""2"" ""/EG-"" ""H"" _""2"" ""O"" ve ""Ag-MgO/EG-"" ""H"" _""2"" ""O"" ) kullanılmıştır. Ayrıca, kolektör performasını arttırmak amacıyla kolektör soğurucusuna akış yönünde iki adet kanatçık eklenerek, kanatçığın kolektör verimi üzerine etkisi incelenmiştir. Sayısal çalışmada gerçeğe yakın sonuçlar elde etmek için SOLTRACE paket programı kullanılarak Monte Carlo Işın İzleme Metodu (MCRT) ile kolektör soğurucusu üzerinde homojen olmayan ısı akısı dağılımı oluşturulmuştur. Nusselt sayısı, sürtünme faktörü, PEC sayısı, entropi üretimi ve Bejan sayısı bu kapsamda incelenen parametrelerdir. Deneysel çalışma sonuçlarına göre, ""ZnO/EG-"" ""H"" _""2"" ""O"" nanoakışkanının ısı transfer ve akış karakteristikleri bakımından baz akışkana (""EG-"" ""H"" _""2"" ""O"" ) göre üstünlük sağladığı tespit edilmiştir. Hacimsel debinin ve nanopartikül hacimsel oranın artmasıyla birlikte kolektörün ısı transferi performansının da arttığı saptanmıştır. Ayrıca, kolektör veriminin artan hacimsel debi ve nanopartikül hacimsel oranı ile birlikte yaklaşık %30’a kadar arttığı saptanmıştır. Sayısal analiz sonuçlarında ise, hibrit nanopartiküllü nanoakışkanların tek nanopartiküllü nanoakışkana oranla kolektör içerisindeki taşınımla ısı transferini daha fazla arttırdığı gözlenmiştir. Bunun yanında hibrit nanoakışkanların entropi üretiminin de tek nanoapartiküllü nanoakışkana göre daha düşük olduğu gözlemlenmiştir. Kolektörün ısı transfer performansının soğurucuya kanatçık eklenmesiyle birlikte çok daha yüksek seviyelere ulaştığı elde edilmiştir. Çalışma akışkanı olarak ""Ag-MgO/EG-"" ""H"" _""2"" ""O"" hibrit nanoakışkanının kullanıldığı durumda kanatçıklı soğurucu boru içerisindeki Nusselt sayısının kanatçıksız duruma göre %24’e, sürtünme katsayısının %19’a ve PEC sayısının ise %12’ye varan oranlarda daha yüksek çıktığı saptanmıştır. Kanatçıklı soğurucu boruya sahip olan kolektörde entropi üretiminin kanatçıksız duruma göre daha yüksek çıktığı gözlemlenmiştir. Kanatçıklı soğurucu boru geometrisine sahip kollektör içerisindeki %4 nanopartikül hacimsel oranlı ""Ag-MgO/EG-"" ""H"" _""2"" ""O"" hibrit nanoakışkanının 80 lt/sa debi değerindeki akış şartı parabolik oluk tipi güneş kolektöründe en yüksek ısıl performansın elde edilmesini sağlamıştır.
