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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 helically-coiled solar water collector at various angular placements
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2023) Variyenli, Halil Ibrahim; Amini, Ali; Tuncer, Azim Dogus; Khanlari, Ataollah; Kolay, Sahin
    Solar water collectors are widely utilized for providing hot water to be used in different applications. In this work, a solar water collector with a helically coiled absorber has been designed, fabricated, and examined at different test conditions to specify its overall performance. One of the major goals of using a tube-type absorber is to upgrade the thermal efficiency of the collector by providing a perpendicular angle between the absorber and incident solar rays. Also, using a helically-coiled structure make it possible to increase the absorber surface in a relatively small volume in comparison to conventional solar water collectors. In the first step of this research, the designed helically-coiled solar collector has been simulated using a solar radiation model. In the next step, the manufactured helically-coiled solar collector has been experimentally tested at three different inclination angles and various water flow rates. According to the experimental results, mean thermal efficiencies of horizontal, vertical, and angular helically-coiled collectors were obtained in the ranges of 29.48-48.23%, 27.17-47.03%, and 32.50-52.71%, respectively. In addition, sustainability index values for horizontal, vertical and angular helically-coiled collectors were achieved between the ranges of 1.0041-1.0091, 1.0039-1.0087, and 1.0043-1.0102, respectively. Moreover, the maximum deviation between numerical and experimental findings was calculated as 14%.
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    Experimental Evaluation of Installation Cleaning in terms of Energy Efficiency in Individual Heating Systems -2
    (Gazi Univ, 2022) Yuruk, Muhammet; Variyenli, Halil Ibrahim; Martin, Kerim; Khanlari, Ataollah; Aytac, Ipek
    Various problems and pollution occur in heating systems over time, especially calcification. This contamination prevents the radiators from dissipating heat, causing the system to operate inefficiently and consume energy. In this study, an experimental research was carried out on the energy efficiency of installation cleaning. In the study, these two situations were compared with the measurements and calculations made before and after the installation cleaning. It has been observed that the cleaning of the installation homogenizes the temperature distribution in the radiator. As a result of the cleaning, an increase of approximately 5 degrees C was obtained in the radiator temperatures. In addition, while a 21.16% reduction was achieved in natural gas consumption, a 17.2% improvement was achieved in the convection heat transfer mechanism in the radiators. In addition, depending on the amount of natural gas used, reductions in the amount of harmful gases (NO, NOx, CO, CO2 and O-2) released to the environment have been achieved, varying between 3.2% and 25%.
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    Experimental Investigation of the Effect of Using Thermostatic Radiator Valve on Energy Efficiency in Buildings
    (Gazi Univ, 2022) Karacam, Tuncay; Variyenli, Halil Ibrahim; Martin, Kerim; Khanlari, Ataollah; Aytac, Ipek
    In this study, experiments were carried out in an apartment with a net area of 98.8 m(2) in order to observe the effects of using a thermostatic radiator valve (TRV) on energy efficiency. Experiments were performed with normal valves installed on the radiators, then the existing valves were replaced with thermostatic valves and the experiments were repeated. Thanks to the TRVs, the temperature of each room could be kept constant at the set value and it was observed that a comfortable heating was provided. The use of TRV homogenized the temperature distributions on the radiators and provided natural gas savings by preventing unnecessary heating of the radiator. According to the results obtained, it has been calculated that natural gas consumption can be reduced by 1.4 m(3) per day thanks to TRV. This value means a natural gas saving of 41.82 m(3) per month and 250.9 m(3) with a 6-month usage per year. Considering the current natural gas prices, there is an annual saving of 577.1(sic). A total of 7 thermostatic valves with a unit price of 150 (sic) were installed in the flat and the payback period was calculated as 1.67 years. In addition, it has been observed that a reduction of around 470 kg per year can be made in the amount of CO2 released to the environment due to the decrease in fuel consumption.
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    Improving the performance of a heat pipe evacuated solar water collector using a magnetic NiFe2O4/water nanofluid
    (Elsevier, 2023) Tuncer, Azim Dogus; Aytac, Ipek; Variyenli, Halil Ibrahim; Khanlari, Ataollah; Mantici, Sedat; Kararti, Alim
    In the recent years, heat pipe evacuated tube solar collectors (HP-ETSCs) are widely utilized due to their easy maintenance and high efficiency. However, increasing the performance of available systems is an important issue that investigated in many studies. The main goal of this study is improving the thermal performance of a HPETSC by replacing the working fluid of the system with magnetic nanofluid. In this context, magnetic type NiFe2O4/water nanofluid has been utilized as working fluid in a HP-ETSC to improve the overall performance of the system. Accordingly, NiFe2O4 nanoparticles has been mixed with distilled water at the ratio of 2 wt% in order to obtain magnetic nanofluid. The performance tests have been performed at various water flow rates (0.016 kg/ s, 0.033 kg/s, and 0.050 kg/s) using distilled water and NiFe2O4/water magnetic nanofluid. The general outcomes of this work indicated positive results of using NiFe2O4/water magnetic nanofluid on the efficiency of the HP-ETSC. Utilizing NiFe2O4/water nanofluid in the HP-ETSC as working fluid averagely increased the thermal performance as 37.72%, 39.59% and 44.96% at flow rates of 0.016 kg/s, 0.033 kg/s and 0.050 kg/s, respectively. In addition, using NiFe2O4/water magnetic nanofluid in the HP-ETSC averagely increased the exergy efficiency as 60.59%, 55.61%, 59.61% at flow rates of 0.016, 0.033 and 0.050 kg/s, respectively.
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    Investigating the effects of using MgO-CuO/water hybrid nanofluid in an evacuated solar water collector: A comprehensive survey
    (Elsevier, 2023) Aytac, Ipek; Tuncer, Azim Dogus; Khanlari, Ataollah; Variyenli, Halil Ibrahim; Mantici, Sedat; Gungor, Levent; Unvar, Sinan
    In thy. work, the effects of utilizing Mg0-CuO, water nanofluid on the energetic t nd exergetic performances of a heat pipe evacut ted ;olar water collector have been analyzed experimentally. In this regard, two identical heat pipe evacuated sola, water collectors have been installed. In the first system, deionized water has been utilized. In the second collector, newly prepared nanofluid have been used and both collectors have been tested under the same climatic conditions at three flow rates containing 0.016, 0.033 and 0.050 kg/s. According to the experi mentally obtained outcomes, mean theimal efficiencies of the system using deionized water were obtained between 49.62 and 56.18 %. Also, average [hernial efficiencies of the system with Mg0-010/water as working fluid were obtained between 69.89 and 77.21 %. Average sustainability index values were attained in the range of 1.0271-1.0676 for both investigated systems. moreover, utilizing hybrid nanofluid in the system reduced the payback period between 25.14 and 27.74 %. The yearly ..7.02 savings for the system with and without nanofluid were attained between 0.307-0.343 and 0.217-0.251 ton/year, respectively. General outcomes of this study exhibited notable effects of utilizing Mg0-CuO/water on improving the thermal performance of the heat pipe evacuated solar water collector.
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    INVESTIGATING THE IMPACT OF USING MAGNETIC-TYPE NANOFLUID ON THE THERMAL PERFORMANCE OF A SOLAR WATER COLLECTOR WITH HELICALLY COILED TUBE ABSORBER
    (Begell House Inc, 2024) Aytac, Ipek; Tuncer, Azim Dogus; Variyenli, Halil Ibrahim; Khanlari, Ataollah; Satay, Ebru
    In recent years, solar water collectors are commonly preferred for supplying heated water to be utilized in various processes. In the present study, a solar water collector equipped with a helically coiled absorbing surface has been manufactured and experimented under various working conditions to determine its general behavior. The main goal of using a helically coiled absorber is enhancing energy harvest in the collector by ensuring vertical angle between the absorbing area and incident radiation. In addition, for providing greater increase in thermal efficiency, magnetic type nanofluid has been used as a working fluid. In this context, NiFe(2)O(4 )nano-sized particles have been mixed with water at the ratio of 2% (wt./wt.). Accordingly, the performance of the collector has been empirically examined using both water and magnetic nanofluid at two different flow rates. The overall results of the present survey exhibited successful use of magnetic type nanofluid in a solar collector equipped with a helically coiled absorbing surface. Utilizing magnetic nanofluid in the collector as circulating fluid raised the thermal efficiency on an average of 20.29% and 23.59% at volumetric flow rates of 0.5 lpm, and 0.9 lpm, respectively. Moreover, utilizing NiFe2O4/water nanofluid in the water collector enhanced the exergy efficiency on an average of 44.53% and 40.04% at volumetric flow rates of 0.5 lpm and 0.9 lpm, respectively.
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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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    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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    Performance improvement of a heat pipe evacuated solar water collector using quartz/water nanofluid: A numerical and experimental study
    (Pergamon-Elsevier Science Ltd, 2024) Aytac, Ipek; Khanlari, Ataollah; Tuncer, Azim Dogus; Variyenli, Halil Ibrahim; Unvar, Sinan
    Solar water collectors (SWCs) are the major element of any solar power system. Evacuated tube solar water collectors (ESWCs) contain multiple evacuated tubes formed between the tubular absorber and the glass cover in each tube to reduce heat losses. In this survey, it is aimed to improve the thermal performance of a heat pipe evacuated tube water solar collectors (HP-ESWCs) by using quartz nanofluid as the working fluid and experimentally and numerically obtained results are explained in detail. The numerical simulation of the heat pipe part of the system aims to present a general view of energy gain by the heat pipe, evaporation of the working liquid inside the pipe and condensation of the vapor by releasing its energy in the condenser section. Also, the performance of the whole collector was experimentally examined utilizing four different working fluids. The outcomes indicate that the thermal efficiency of the HP-EWSC using deionized water varied between 29.63 and 55.78 %, 36.50-61.13 %, 40.73-64.35 % and 32.81-75.92 % at 0.008, 0.016, 0.033 and 0.050 kg/s flow rates, respectively. Also, the efficiency of HP-EWSC using quartz/water changed between the ranges of 43.87-71.95 %, 50.86-78.22 %, 46.37-79.66 % and 55.60-85.64 % at 0.008, 0.016, 0.033 and 0.050 kg/s flow rates, respectively. Average exergy efficiency enhancement by utilizing quartz/water nanofluid in the present work varied in the range of 34.23-99.97 %. General findings of this study clearly showed the positive impacts of using quartz/water as working fluid in the HP-ESWCs on the overall performance.
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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.