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    AN EXPERIMENTAL INVESTIGATION TO PREDICT OPTIMUM CHARGE OF A HEAT PUMP SYSTEM
    (Begell House Inc, 2023) Afshari, Faraz; Khanlari, Ataollah; Tuncer, Azim Dogus; Soezen, Adnan
    Working principles of heat pumps is an important matter from a thermodynamic point of view that has been researched from various aspects. In this study, undercharged, optimum charged, and overcharged conditions of a heat pump were investigated using R134a refrigerant. Variations in temperature, pressure, and the coefficient of performance have been evaluated and it was aimed to find out the optimum charge condition considering different parameters. According to the experimentally obtained findings, the coefficient of performance was increased by more than three times when the refrigerant amount increased from 2000 g to similar to 7300 g. The general outcomes of the present study indicated that optimum refrigerant charge amount can notably affect the performance of heat pump apparatus. It was shown that the P-h diagram of all heat pump systems depends on the working conditions and the refrigerant charge is a very important criterion that can make significant changes in the P-h diagram. It was found that, by increasing refrigerant charge, after the downtrend starts in the compressor inlet temperature, 20% refrigerant can be added to achieve the maximum COP value. Additionally, the critical point in expansion valve outlet temperature was used to find the optimum charge. It was revealed that if 140% refrigerant is added to the given refrigerant at critical point, the optimum COP value can be achieved.
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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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    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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    Utilization of recyclable aluminum cans as fins in a vertical solar air heating system: An experimental and numerical study
    (Elsevier, 2023) Khanlari, Ataollah; Tuncer, Azim Dogus; Afshari, Faraz; Sozen, Gulce
    Heating loads cover a large portion of the total energy consumption of buildings. Solar air heating is a sustainable and low-cost alternative for heating applications instead of employing fossil energy sources. In this work, vertical solar air collectors (VSACs) have been developed to be utilized in buildings. Moreover, aluminum beverage cans have been utilized as fins to improve the effectiveness of the collector system. In the initial stage of the study, various aluminum can configurations have been analyzed numerically. Numerical findings showed that symmetric placement of aluminum cans gave better results in comparison to the hollow VSAC and VSAC with asymmetric can placement. In this regard, symmetric can configuration has been applied to the VSACs with two plenum thicknesses including 100 mm and 150 mm for experimental investigation. Experiments have been performed at two flow rates and thermal efficiencies of the tested VSACs were found between the range of 55.16-76.22%. Also, average exergy efficiency values for VSACs with higher and lower plenum thicknesses were obtained between the ranges of 8.34-8.85% and 9.84-10.36%, respectively. The overall findings of the present research exhibited successful utilization of recyclable aluminum beverage can-integrated VSACs for air heating.