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    A detailed investigation of the temperature-controlled fluidized bed solar dryer: A numerical, experimental, and modeling study
    (Elsevier, 2022) Gurel, Ali Etem; Agbulut, Umit; Ergun, Alper; Ceylan, Ilhan; Sozen, Adnan; Tuncer, Azim Dogus; Khanlari, Ataollah
    Solar thermal systems are generally utilized for providing sustainable and environmentally friendly thermal energy that can be used in different applications. In the present study, a temperature-controlled fluidized bed solar drying system along with flat plate and plate with zigzag fins has been designed, manufactured, and experimentally tested. In the first step, the thermal behavior of designed solar air collectors has been numerically modeled. In the next step, the drying system's performance has been experimentally investigated. The overall efficiency of the system was found to be 64%. The maximum exergy efficiency of flat and zigzag plate solar air collectors was calculated as 7.2% and 11.6%, respectively. Then moisture content (MC) and moisture ratio (MR) values were modelled by response surface methodology (RSM), and the predicted results were compared with four metrics. It was found that the drying parameters were highly fitted with the mathematical models. MC metric was predicted with accurate values for performance criteria of R-2, R-RMSE, and MBE as 0.9995, 1.94%, and -0.0096, respectively. The general outcomes of numerical, experimental and modeling analyses of this research exhibited successfulness of the developed the fluidized bed solar drying system.
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    CFD analysis and experimental investigation to determine the flow characteristics around NACA 4412 airfoil blades at different wind speeds and blade angles
    (Sage Publications Ltd, 2023) Afshari, Faraz; Khanlari, Ataollah; Sozen, Adnan; Tuncer, Azim Dogus; Ates, Ibrahim; Sahin, Bayram
    An aerodynamically efficient blade is one of the prime necessities to extract the maximum mechanical power from a wind turbine. A number of researches are available in the literature studying blade design and configuration to improve aerodynamic characteristics of horizontal axis wind turbines. Less attention, however, has been devoted to wind turbines in terms of simultaneous optimization of blade and airfoil angles. The present study is important for the aerodynamic design and manufacturing of wind turbine blades. In this regard, various blade angles have been numerically simulated to determine the optimum blade angle. In addition to numerical analysis, experimental tests have been done to investigate NACA 4412 blade angle. As a result of this study, it was observed that blade angle in the range of 5 degrees-10 degrees showed the best performance among the tested various blade angles.
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    Energy and exergy analysis of a vertical solar air heater with nano-enhanced absorber coating and perforated baffles
    (Pergamon-Elsevier Science Ltd, 2022) Khanlari, Ataollah; Tuncer, Azim Dogus; Sozen, Adnan; Aytac, Ipek; Ciftci, Erdem; Variyenli, Halil Ibrahim
    In this work, the effect of applying nano-enhanced absorber coating on the energetic and exergetic performance of an unglazed vertical solar air heating system has been analyzed numerically and experimentally. In the first step of the research, various configurations of vertical solar air heaters including hollow, baffled and perforated baffled systems have been surveyed by using computational fluid dynamics. According to the numerically obtained findings, the system with perforated baffles gave the best performance metrics. In this regard, two heating systems with perforated baffles have been manufactured. One of the system was painted with a regular matt black paint while CuO nano-embedded black paint applied to the other solar heater. Fabricated heaters have been experimentally surveyed at three different flow rates. Thermal efficiency values for the heaters with and without nanoparticles were found between 58.10-76.22% and 54.96-72.05%, respectively. Applying nano-embedded coating increased the exergy efficiency in the range of 9.25-10.58%. In addition, maximum deviation of numerically and experimentally attained outlet temperature values was calculated as 4.74%. Moreover, general findings of this research showed the successful utilization of nano-enhanced absorber coating. (C) 2022 Elsevier Ltd. All rights reserved.
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    Experimental and numerical analysis of a grooved hybrid photovoltaic-thermal solar drying system
    (Pergamon-Elsevier Science Ltd, 2023) Tuncer, Azim Dogus; Khanlari, Ataollah; Afshari, Faraz; Sozen, Adnan; Ciftci, Erdem; Kusun, Baris; Sahinkesen, Istemihan
    Photovoltaic-thermal (PVT) systems are sustainable applications that allows to produce thermal and electrical energies simultaneously. In this work, a sustainable solar drying system that contains a modified PVT-air collector has been designed, numerically analyzed, manufactured and tested. In the first step of this study, four different PVT collector configurations have been numerically analyzed in order to develop a new hybrid PVT drying system. According to the numerically obtained results, outlet temperature of the PVT collector with grooved absorber, spherical turbulators and baffle configurations was higher than the outlet temperature of the unmodified collector as 15.77 %. This promising PVT collector was then fabricated and integrated with a drying chamber. The manufactured hybrid drying system has been tested under various air flow rates. The experimental findings illustrated that the average thermal efficiency and overall exergy efficiency of the PVT collector varied between 61.32 and 77.49 % and 10.65-11.17 %, respectively. In addition, mean exergy efficiency of the drying chamber was found in the range of 59.16-68.31 %. Average sustainability index values of the collector and the drying chamber was obtained between the ranges of 1.12-1.14 and 3.74-5.82, respectively. Moreover, payback period of the dryer varied between 2.98 and 3.51 years according to the economic analysis.
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    Experimental investigation of effect of refrigerant gases, compressor lubricant and operating conditions on performance of a heat pump
    (Journal Of Central South Univ, 2021) Afshari, Faraz; Sozen, Adnan; Khanlari, Ataollah; Tuncer, Azim Dogus; Ali, Hafiz Muhammad
    In the field of heat pumps, there are a number of parameters that affect the performance and efficiency of the apparatus, which have been the subject of studies by individual researchers in the literature. This study describes an experimental method in order to investigate the effects of some significant parameters on heat pump performance. In this regard, a laboratory heat pump setup has been utilized to operate in different working conditions for achieving an appropriate estimation to find out effects of mentioned parameters such as refrigerant type and charge amount, compressor oil viscosity, compressor cooling fan, secondary fluids temperature and flow rate. Different refrigerants have been selected and used as circulating fluid in the installed heat pump. Although this work has been devoted to a detailed attempt to recognize the effects of various parameters on the coefficient of performance (COP) value, an appropriate method has been carried out to survey the obtained results by using economic analysis. It was revealed that one of the main parameters is refrigerant charge amount which has a notable effect on COP. The temperature of the heat source was also tested and the performance of the system increased by more than 11% by employing mentioned modifications and various operating conditions. In addition, by selecting a low viscosity compressor oil, the system performance increased by 18%. This improvement is more than 6% for the case that cooling fan is installed to cool the compressor element.
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    Heat transfer enhancement of finned shell and tube heat exchanger using Fe2O3/water nanofluid
    (Journal Of Central South Univ, 2021) Afshari, Faraz; Sozen, Adnan; Khanlari, Ataollah; Tuncer, Azim Dogus
    Heat transfer mechanisms and their thermal performances need to be comprehensively studied in order to optimize efficiency and minimize energy losses. Different nanoparticles in the base fluid are investigated to upgrade the thermal performance of heat exchangers. In this numerical study, a finned shell and tube heat exchanger has been designed and different volume concentrations of nanofluid were tested to determine the effect of utilizing nanofluid on heat transfer. Fe2O3/water nanofluids with volume concentration of 1%, 1.5% and 2% were utilized as heat transfer fluid in the heat exchanger and the obtained results were compared with pure water. ANSYS Fluent software as a CFD method was employed in order to simulate the mentioned problem. Numerical simulation results indicated the successful utilization of nanofluid in the heat exchanger. Also, increasing the ratio of Fe2O3 nanoparticles caused more increment in thermal energy without important pressure drop. Moreover, it was revealed that the highest heat transfer rate enhancement of 19.1% can be obtained by using nanofluid Fe2O3/water with volume fraction of 2%.
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    Numerical and experimental investigation of a solar absorber extension tube with turbulators for upgrading the performance of a solar dryer
    (Emerald Group Publishing Ltd, 2022) Khanlari, Ataollah; Afshari, Faraz; Sozen, Adnan; Tuncer, Azim Dogus; Kusun, Baris
    Purpose During the past several years, research and studies in the field of solar energy have been continuously increased. One of the substantial applications of solar energy is related to industrial utilization for the drying process by efficient heat transfer methods. This study aims to upgrade the overall performance of an indirect solar dryer using a solar absorber extension tube (SET) equipped with ball-type turbulators. Design/methodology/approach In this work, three various SETs including hollow (SET Type 1), 6-balls (SET Type 2) and 10-balls (SET Type 3), have been simulated using Fluent software to evaluate heat transfer characteristics and flow structure along the air passage. Then, the modified solar drying system has been manufactured and tested at different configurations. Findings The findings indicated that adding a SET improved the performance notably. According to the results, using turbulators in the tube has a positive effect on heat transfer. The highest overall thermal efficiency was found in the range of 51.47%-64.71% for the system with SET Type 3. The maximum efficiency increment of the system was found as 19% with the use of SET. Also, the average specific moisture extraction rate, which is a significant factor to survey the effectiveness of the dehumidification system was found between 0.20 and 0.38 kg kWh(-1). Originality/value In the present study, a novel SET has been developed to upgrade the performance of the solar dehumidifier. This new approach makes it possible to improve both thermal and drying performances.
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    Numerical and experimental study on thermal performance of a novel shell and helically coiled tube heat exchanger design with integrated rings and discs
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2022) Gungor, Alper; Khanlari, Ataollah; Sozen, Adnan; Variyenli, Halil Ibrahim
    Shell and Helically Coiled Tube Heat Exchangers (SHCTHEXs) are utilized in energy conversion applications in industry and in various engineering systems. They are generally composed of a helically coiled tube and a shell covering it. This coiled structure of tubes, provides better heat transfer and takes less space. There is an ongoing interest in research on this type of heat exchangers. In this study, a new design was created modifying a simple type of conventional shell and helically coiled heat exchanger, by integrating discs and rings. These rings and discs were attached to the helically coiled tubes with the aim of performing as baffles restricting the shell side flow and creating turbulence. The thermal performance of a conventional heat exchanger was improved by this modification. The study was carried out both numerically and experimentally. At first step, two SHCTHEXs, one conventional; one modified, were designed with same overall geometric dimensions. Then created solid models were numerically simulated with same boundary conditions using ANSYS Fluent. Simulations were performed with various flow rates and the results were reported. According to the simulations, compared to the conventional one, with the modified heat exchanger 7.1% increase in average amount of heat transfer rate and around 20% increase in overall heat transfer coefficient were obtained. With the promising results taken by simulations, the modified heat exchanger was fabricated with the same dimensions and it was experimentally tested with same conditions in laboratory to verify the simulation results. Experimental results were in harmony with the simulations with little differences. The average differences between simulation and experimental values in terms of average amount of heat transfer rate were obtained as 2.4% for 3 l/min hot fluid flow rate and 3.5% for 4 l/ min hot fluid flow rate. Overall heat transfer coefficient of modified SHCTHEX with circular baffles achieved in the range of 1050-1400 W/m2K. General outcomes of this study exhibited successful design of baffled SHCTHEX.
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    NUMERICAL INVESTIGATION OF THERMAL PERFORMANCE ENHANCEMENT POTENTIAL OF USING Al2O3-TiO2/WATER HYBRID NANOFLUID IN SHELL AND HELICALLY COILED HEAT EXCHANGERS
    (Begell House Inc, 2022) Gungor, Alper; Sozen, Adnan; Khanlari, Ataollah
    Shell and helically coiled tube heat exchangers (SHCTHEXs) are a special type of shell-and-tube heat exchangers and they are widely used in industry in many processes. The tubes inside the shell are curved to form a helical coil which has a positive impact on heat transfer. The main purpose of this study is to investigate thermal performance enhancement potential of using a new type of hybrid nanofluid in SHCTHEXs. In this study, two types of SHCTHEXs - one vertically oriented and the other horizontally oriented - have been designed with the same geometrical dimensions. These designs have been simulated with two types of fluid on the shell side: water and Al2O3-TiO2/water hybrid-type nanofluid at various shell-side flow rates in order to reveal the heat transfer improvement potential of using this hybrid nanofluid in SHCTHEXs. The simulations indicated that utilizing Al2O3-TiO2/water hybrid-type nanofluid on the shell side resulted in 7.7% increase in the average heat transfer rate for vertically oriented SHCTHEX and 9% increase for the horizontally oriented SHCTHEX. Calculated heat transfer rate values ranged between 3337 and 5136 W. Among the simulated designs the best performing combination has been horizontally oriented SHCTHEX with Al2O3-TiO2/water hybrid-type nanofluid on the shell side. This combination provided 2.5 degrees C better cooling at the hot fluid outlet compared to poorest performing combination: vertically oriented SHCTHEX with water (both streams at 3 lpm). Using nanofluid increased the overall heat transfer coefficient parameter in horizontally and vertically oriented heat exchangers as 17.2% and 13.7%, respectively. The achieved outcomes of this work indicate that utilizing an Al2O3-TiO2/water hybrid nanofluid provides a notable amount of increase in heat transfer rate. In addition, overall results of the study showed that horizontally oriented SHCTHEX had better performance in comparison with vertically oriented one.
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    PASSIVE THERMAL MANAGEMENT OF PHOTOVOLTAIC PANEL BY USING PHASE CHANGE MATERIAL-FILLED ALUMINUM CANS: AN EXPERIMENTAL STUDY
    (Begell House Inc, 2022) Tuncer, Azim Dogus; Khanlari, Ataollah; Aytac, Ipek; Ciftci, Erdem; Sozen, Adnan; Variyenli, Halil Ibrahim
    In the recent years, researches are focused on improving the efficiency of photovoltaic (PV) panels by cooling panel surface utilizing different methods. In this work, paraffin wax-filled aluminum beverage cans have been utilized to improve the performance of photovoltaic panels. The main aims of this study are reutilizing waste materials in solar systems and increasing the performance of a PV panel by employing an unconventional approach. Modified and unmodified PV panels have been experimentally investigated simultaneously to observe and compare their performances. Experimentally attained outcomes showed that electrical efficiency was upgraded from 70.69% to 72.60%. Moreover, normalized power output efficiency was (round as 61.72% and 71.56%, respectively, for unmodified and modified PV systems. In addition to the electrical performance investigation, an exergy analysis has been performed and mean exergy efficiency values for conventional and modified PV panels were found as 2.26% and 5.73%, respectively. General outcomes of this study showed successful utilization of paraffin wax -filled aluminum cans as a thermal management and efficiency improvement technique in photovoltaic systems.
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    SEASONAL ENERGY-EXERGY ANALYSIS OF A NEW FOLDABLE PHOTOVOLTAIC-THERMAL AIR COLLECTOR: AN EXPERIMENTAL AND NUMERICAL STUDY
    (Begell House Inc, 2022) Tuncer, Azim Dogus; Khanlari, Ataollah; Sozen, Adnan
    Simultaneous generation of electricity and thermal energy can be done employing photovoltaic-thermal (PVT) systems. A significant issue in access to reliable and continuous energy is the power shortage in some regions in the world and the problems that arise accordingly. In this survey, yearly performance of a novel foldable PVT collector to be used in regions with limited access to energy has been experimentally and numerically investigated. In the first step of this survey, the CFD approach has been utilized to select the most efficient absorber design for the PVT air collector. In the next stage of the work, the PVT collector has been fabricated considering the numerical results and tested at different working condition in various seasons. Both numerical and experimental outcomes of the present work indicated the successful design of the foldable PVT system. The mean thermal ef iciency of the portable PVT collector was attained in the range of 51.11-67.05%. The overall exergetic ef iciency of the PVT system varied between 5.18 and 6.14%.
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    Upgrading the performance of shell and helically coiled heat exchangers with new flow path by using TiO2/water and CuO-TiO2/water nanofluids
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2023) Tuncer, Azim Dogus; Khanlari, Ataollah; Sozen, Adnan; Gurbuz, Emine Yagiz; Variyenli, Halil Ibrahim
    Along with the developing technologies, the need for energy has increased day by day and negative environ-mental effects of fossil energy based systems increased the importance of efficient energy systems. In the recent years, shell and helically coiled type heat exchangers (SHCHEs) are extensively used in various applications because of their superior specifications in comparison with other heat exchangers. In the present work, it is targeted to raise the thermal performance of recently developed shell and helically coiled heat exchangers using single and hybrid type nanofluids. The main aim of this research is specifying the impact of hybrid CuO-TiO2/ water nanofluid in comparison with single TiO2/water nanofluid. Also, the effect of adding fins as turbulators on performance enhancement of nanofluids was analyzed. In this regard, TiO2/water and CuO-TiO2/water nano -fluids with 1% (wt./wt.) concentration was prepared and circulated in the hot side of both heat exchangers. TiO2/water working nanofluid application in finless and finned SHCHEs averagely upgraded overall heat transfer coefficient as 7.5% and 8.6%, respectively. CuO-TiO2/water working nanofluid application in finless and finned SHCHEs averagely upgraded overall heat transfer coefficient as 10.8% and 12%, respectively. Generally, it was observed that utilizing TiO2/water and CuO-TiO2/water nanofluid in unmodified and modified SHCHEs importantly raised the thermal performance. However, utilization of hybrid type nanofluid presented better performance than single nanofluid in both SHCHEs. Moreover, the outcomes exhibited further positive impacts of integrating fins on performance enhancement of both single and hybrid nanofluids.