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    The artificial neural network model to estimate the photovoltaic modul efficiency for all regions of the Turkey
    (Elsevier Science Sa, 2014) Ceylan, Ilhan; Gedik, Engin; Erkaymaz, Okan; Gurel, Ali Etem
    Artificial neural network (ANN) is a useful tool that using estimates behavior of the most of engineering applications. In the present study, ANN model has been used to estimate the temperature, efficiency and power of the Photovoltaic module according to outlet air temperature and solar radiation. An experimental system consisted photovoltaic module, heating and cooling sub systems, proportional integral derivative (PID) control unit was designed and built. Tests were realized at the outdoors for the constant ambient air temperatures of photovoltaic module. To preserve ambient air temperature at the determined constant values as 10, 20, 30 and 40 degrees C, cooling and heating subsystems which connected PID control unit were used in the test apparatus. Ambient air temperature, solar radiation, back surface of the photovoltaic module temperature was measured in the experiments. Obtained data were used to estimate the photovoltaic module temperature, efficiency and power with using ANN approach for all 7 region of the Turkey. The study dealing with this paper not only will beneficial for the limited region but also in all region of Turkey which will be thought established of photovoltaic panels by the manufacturer, researchers and etc. (C) 2014 Elsevier B.V. All rights reserved.
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    Comparison of bi-directional multi-wave alternating magnetic field effect on ferromagnetic nanofluid flow in a circular pipe under laminar flow conditions
    (Pergamon-Elsevier Science Ltd, 2020) Tekir, Mutlu; Taskesen, Edip; Aksu, Bahri; Gedik, Engin; Arslan, Kamil
    Nanofluids have been attracting huge attention because of their heat transfer enhancement capabilities. Furthermore, magnetic field effect has been being researched recently. By reason of further heat transfer enhancement potential, constant and alternating magnetic fields have been utilized in the present work. Forced convection heat transfer of Fe3O4/water nanofluid flow in a straight pipe under constant and alternating magnetic field effect has been investigated experimentally. Experiments were performed under laminar flow regime (1122 < Re < 2124) and constant heat flux was applied externally on the pipe surface. It is aimed to study effect of different parameters such as Reynolds number, volume concentration of nanoparticle (0 <= phi <= 0.05), constant magnetic field (B = 0.3 T), alternating magnetic field with different wave types (sinus, square and triangle) and different frequencies (2, 5 and 15 Hz) of alternating magnetic field on the convective heat transfer. Experimental results showed that the constant magnetic field offers 13% convective heat transfer enhancement compared to the absence of a magnetic field. On the other hand, the alternating magnetic field increases the convective heat transfer in the pipe up to 35%. Furthermore, lower frequencies of the alternating magnetic field have been more effective in convective heat transfer enhancement. Square wave type alternating magnetic field steps forward in the aspect of convective heat transfer enhancement rate among the other wave types. The alternating magnetic field applications look promising in the future for increasing energy efficiency, and it can also be implemented in heat exchangers, solar collectors, emergency heat removal systems in nuclear power plants.
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    Determination of optimum insulation thickness of external walls with two different methods in cooling applications
    (Pergamon-Elsevier Science Ltd, 2013) Kayfeci, Muhammet; Kecebas, Ali; Gedik, Engin
    Thermal insulation is one of the most effective energy conservation for the cooling applications. For this reason, determination of the optimum thickness of insulation and its selection is the main subject of many engineering investigations. In this study, the optimum insulation thickness on the external walls in the cooling applications is analyzed based on two different methods used to determine annual energy consumption. One of the methods is the degree-hours method (Method 1) that is the simplest and most intuitive way of estimating the annual energy consumption of a building. The other is the method (Method 2) which using the annual equivalent full load cooling hours operation of system. In this paper, a Life Cycle Cost (LCC) analysis is used to evaluate accuracy of these methods, and the results are compared. The results show that the life cycle savings are overestimated by up to 44% in Method 2, while the optimum insulation thickness and payback period are respectively overestimated by up to 74% and 69% in Method 1. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
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    Effect of Al2O3-SiO2/Water Hybrid Nanofluid Filled in a Square Enclosure on the Natural Convective Heat Transfer Characteristics: A Numerical Study
    (Amer Scientific Publishers, 2022) Dagdeviren, Abdullah; Gedik, Engin; Kecebas, Ali; Pazarlioglu, Hayati Kadir; Arslan, Kamil; Alsabery, Ammar I.
    In this study, heat transfer enhancement by natural convection Al2O3/water mono and Al2O3-SiO2/water hybrid nanofluid in an enclosure cavity have been performed utilizing the finite element method. For numerical com-putations, the homogeneous nanofluid approach was considered. The cavity was heated from the left vertical wall and cooled from the right vertical wall while the top and bottom walls were taken as adiabatic. The effects of some related factors such as the Rayleigh number (10(3) <= Ra <= 10(6)) and nanoparticles' volume fraction IP: 182.75.148.10 On: Sat, 13 Aug 2022 10:11:41 (0 <= phi <= 0.05) on the heat transfer by natural convction were examined. To discuss fluid characteristics of mono Copyright: American Scientific Publishers and hybrid type nanofluid under natural convecton effect, the obtained results were presented as streamlines Delivered by Ingenta and isotherms. Also, variations of local and average Nusselt numbers were examined in detail. It was obtained that an increase in the nanoparticle volume fraction leads to the enhancement of convective heat transfer for all Rayleigh numbers. It was also indicated that the highest increment in heat transfer by convection occurs in the nanoparticle volume fraction of 2% for Al2O3/water and 4% for Al2O3-SiO2/water. The present study results are also consistent with the literature results.
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    Effect of constant magnetic field on Fe3O4-Cu/water hybrid nanofluid flow in a circular pipe
    (Springer, 2022) Tekir, Mutlu; Taskesen, Edip; Gedik, Engin; Arslan, Kamil; Aksu, Bahri
    The purpose of this study is to investigate experimentally the convective heat transfer of Fe3O4-Cu/water hybrid nanofluid flow and to obtain the optimum mixing ratio of the hybrid nanofluid in a straight pipe under the influence of a constant magnetic field, applied perpendicularly to the flow direction. An experimental test rig has been designed and built for this purpose followed by rigorous tests that were performed on it for various parameters such as flow rate (corresponding 994 < Re < 2337) and nanoparticle volume concentration (0 < phi < 0.02). The experimental data are consistent with the existing literature. Increasing flow rate has led to an increased Nu number. Furthermore, the addition of both Fe3O4 and Cu nanoparticles into the distilled water increases the convective heat transfer inside the pipe. A significant finding of the study is that the constant magnetic field enables up to 14% convective heat transfer enhancement as opposed to the absence of a magnetic field. Furthermore, 1.0 vol.% Fe3O4-1.0 vol.% Cu/Water hybrid nanofluid performs the best under the effect of the constant magnetic field. Accordingly, the constant magnetic field applied externally to the flow is a key factor to enhance the convective heat transfer.
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    Effect of magnetic field locations on thermo-magnetic convection performance of Fe3O4/H2O ferrofluid flowing in a novel dimpled tube: An experimental study
    (Pergamon-Elsevier Science Ltd, 2023) Gursoy, Emrehan; Gurdal, Mehmet; Pazarlioglu, Hayati Kadir; Dagdeviren, Abdullah; Tekir, Mutlu; Arslan, Kamil; Gedik, Engin
    The aim of this study is to examine the hydrothermal behavior of Fe3O4 Ferrofluid flowing under the effect of uniform magnetic field (0 T <= B <= 0.3 T). In addition, magnetic field locations were changed for each experiment to observe effect of the magnetic field locations (x/D = 20, 40, 60) on the hydrothermal behavior of the proposed system. Fe3O4 Ferrofluid was prepared in phi = 1.0% volume concentration in water and flows under the laminar regime (1131 <= Re <= 2102). Comparisons of the hydrothermal behavior of the novel proposed parameters were performed according to combinations of the different magnetic field locations and magnitudes. It is concluded that the highest Nusselt number was obtained using B = 0.3 T for the magnetic field location of x/D = 20 for both in smooth and dimpled tubes. Compared to B = 0 T, the Nusselt number enhancement was detected by 64.03% for smooth tube for the magnetic field location of x/D = 20 for B = 0.3 T whereas Nusselt number wasaugmented by 45.40% for dimpled tube for the same input parameters. Furthermore, no considerable changes in friction factor was determined under magnetic field effect when the application of magnetic field locations was changed. As a result of these findings, the highest increase in Performance Evaluation Criteria belonging dimpled tube was calculated by 33.54% at Re = 2102 for B = 0.16 T for the magnetic field location of x/D = 20. As a general conclusion, this study can shed light on investigating ferrofluids behavior under magnetic field applied in var-iable magnetic field locations.
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    The effect of MHD flow on hydrothermal characteristics of ferro-nano-fluid in circular pipe
    (Taylor & Francis Inc, 2023) Taskesen, Edip; Tekir, Mutlu; Pazarlioglu, Hayati Kadir; Gurdal, Mehmet; Gedik, Engin; Arslan, Kamil
    In this study, the effect of the constant magnetic field (MF) on the convective heat transfer characteristics of Fe3O4/H2O ferro-nano-fluid with different nano-fluid volumetric concentrations (1.0%, 2.0%, and 5.0%) flowing in a circular pipe has been studied experimentally. Experiments have been conducted under laminar flow regime (1000 <= Re <= 2300). Based on the experimental data, a good agreement has been found with the results and the well-known correlations in the literature. Also, it was obtained that increasing flow rate let to increase in Nusselt number. One of the most important results obtained is that the presence of MF offers up to 8.32% convective heat transfer enhancement compared with the absence of a MF. In addition, the constant MF applied externally to the flow is a key factor to control the convective heat transfer for such kind of geometry, which is widely used in thermal engineering systems.
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    EFFECT OF NANOPARTICLE SHAPE ON NANOFLUID FLOW IN CONICAL HELICAL TUBE
    (Begell House, Inc, 2022) Altunay, Fethi M.; Ali, Majdi A. M.; Gurdal, Mehmet; Pazarlioglu, Hayati Kadir; Arslan, Kamil; Gedik, Engin
    The nanofluid flow in a conical helical tube was numerically investigated. The study has been carried out in three-dimensional laminar flow (85.73 <= De <= 175.55) condition. Al2O3-water nanofluid with different nanoparticle volume fractions (1.0%, 2.0%, 3.0%) has been used as the working fluid in the numerical analyzes. In addition, studies were carried out for blade, platelet, and cylindrical nanoparticle shapes. The average Nusselt numbers and the average Darcy friction factors have been used to estimate the flow and heat transfer performance of nanofluid flow in the conical helical tubes. Numerical results of the study have been presented as the variation of average Nusselt number and average Darcy friction factor with Dean number, nanoparticle shape, and nanoparticle volume fraction. As a result, the highest convective heat transfer performance has been obtained for the cylindrical nanoparticle shape of the %3.0 Al2O3-water nanofluid.
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    EFFECT TO THE PERFORMANCE OF DIFFERENT TYPE ABSORBER PLATES ON THE SOLAR AIR COLLECTORS
    (Gazi Univ, Fac Engineering Architecture, 2008) Gedik, Engin; Kecebas, Ali; Oz, Etem Sait
    In this study, two different types of solar air collectors, zigzagged absorber surface type and flat absorber surface type called Model I and Model II respectively, have been constructed and examined experimentally. Experiments were made between 10.00-17.00 hours of August and September under Karabuk conditions and tests were carried out for five days. Energy and exergy performances have been computed using the experimental data. At the end of the study, it showed that energy and exergy performances of the Model II solar air collector were better than Model I solar air collector. While energy and exergy performances of the Model II solar air collector was %46,5 and %1,35, Model I solar air collector performance was %32,72 and %1,35.
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    Effects of two-phase nanofluid model and localized heat source/sink on natural convection in a square cavity with a solid circular cylinder
    (Elsevier Science Sa, 2019) Alsabery, Ammar, I; Gedik, Engin; Chamkha, Ali J.; Hashim, Ishak
    In the present study, natural convection heat transfer of Al2O3-water nanofluid inside a square cavity with a solid circular cylinder is investigated numerically. For numerical computations, the finite element method is used by taking into consideration Buongiorno's two-phase model. Parts of the vertical surfaces of cavity are kept at constant temperature (left wall T-h and right wall T-c) while the other walls (horizontal walls and the remaining of the vertical walls) are taken as adiabatic. The effects of some pertinent parameters such as the Rayleigh number (10(3) <= Ra <= 10(6)), nanoparticle volume fraction (0 <= phi <= 0.04), thermal conductivity of the solid cylinder (k(w) = 0.28, 0.76, 1.95, 7 and 16), radius of solid cylinder (0.1 <= R <= 0.4), heat source/sink length (0.2 <= D <= 0.8), and the heat source/sink position (0.2 <= B <= 0.8) on the fluid flow and heat transfer characteristics are investigated. The obtained numerical results are depicted graphically and discussed in detail from the point of view of the streamlines, isotherms, nanoparticle volume fractions and the local and average Nusselt number Nu. It is indicated that the heat transfer is enhanced with an increase in the nanoparticle volume fraction for all studied Rayleigh numbers. Furthermore, the thermal conductivity, solid circular cylinder size, D and B parameters are the key factors to control and optimize the heat transfer inside the cavity that is partially heated and cooled. The proposed method is found to be in good agreement between previously published experimental and numerical results. (C) 2018 Elsevier B.V. All rights reserved.
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    Effects of using nanofluid, applying a magnetic field, and placing turbulators in channels on the convective heat transfer: A comprehensive review
    (Pergamon-Elsevier Science Ltd, 2022) Gurdal, Mehmet; Arslan, Kamil; Gedik, Engin; Minea, Alina Adriana
    Recent studies in the field of thermal engineering revealed that employing nanofluid as a working fluid in a specific channel, considering both turbulators and magnetic field effect is scarce. Studies on the convective heat transfer performance of the thermal systems focus mostly on the effect of using either nanofluid as a new fluid, magnetic field, or turbulators. This review highlights the single and combined effects of these parameters on the heat transfer enhancement of such systems. Nanofluid type, its volume fraction, channel and turbulator geometry, magnetic field type, and flow regime were considered as the base parameters while the enhancement in heat transfer is evaluated. From a state-of-the-art review, it was noticed that most studies reveal that increasing the volume fraction of nanofluid, magnetic field strength, and Reynolds number can attain an upsurge in the heat transfer in a specific channel. Nevertheless, drawbacks are poorly discussed in the open literature. Regarding the turbulator geometry, which actually limits the magnetohydrodynamic and thermal boundary layer development, its complexity boosts also the convective heat transfer. The maximum heat transfer enhancement was noticed for higher nanoparticle volume fractions, higher magnetic field strengths, and complex geometries in channel flow. The highest heat transfer improvement was obtained for the MWCNT/H2O nanofluid (i.e., between 70% and 190%). With the effect of magnetic field intensity of Ha = 30 applied to the Cu/H2O nanofluid flow, a thermal recovery of 76% was achieved. Concluding, this comprehensive review can be beneficial to researchers working in the field of flow and heat transfer applications with the use of nanofluid, turbulator, and magnetic field together.
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    Electrical field effect on three-dimensional magnetohydrodynamic pipe flow: a CFD study
    (Inderscience Enterprises Ltd, 2016) Recebli, Ziyaddin; Gedik, Engin; Selimli, Selcuk
    Steady, laminar three-dimensional (3D) magnetohydrodynamic (MHD) flow of an electrically conducting fluid in a circular pipe under the both magnetic and electrical field are studied. External magnetic and electrical fields are applied perpendicular to the flow direction and each other while the fluid motion is subjected to constant pressure gradient along axial-direction in the present paper. Fluent 14.0, the finite element software based on the finite volume approach was used to calculate the 3D fluid dynamics and electromagnetic field partial differential equations iteratively. The originality of this work is that, in addition to magnetic field; the effect of electrical field on MHD flows is being examined with help of user defined function (UDF) code. The magnetic field leads to decrease in the velocity of flow, whereas the electrical field applied with magnetic field acted to increase and decrease the velocity of flow depending on the direction of applied external electrical field. The obtained results were depicted graphically and discussed.
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    Energy analysis of magnetite nanofluid flowing in newly designed sudden expansion tube retrofitted with dimpled fin
    (Pergamon-Elsevier Science Ltd, 2022) Guersoy, Emrehan; Pazarlioglu, Hayati Kadir; Dagdeviren, Abdullah; Guerdal, Mehmet; Gedik, Engin; Arslan, Kamil; Kurt, Hueseyin
    Sudden expansion geometry plays an important role in the design of many engineering applications such as heat exchangers to avoid thermal stress on welded joints. While the heat transfer in these geometries is maximized at the reattachment points, it decreases to a minimum in the recirculation regions created by the fluid. To prevent this situation and improve the performance of the expansion tubes, nanofluid, and expanded surfaces can be used. For this purpose, forced convection of magnetite nanofluid flow in various expansion ratios has been investigated numerically in this study. Analyses have been performed on Reynolds ( Re ) numbers ranging from 100 to 2000, constant and uniform heat flux at 600 W/m(2), and volume concentrations (1.0 <=phi <= 2.0 vol.%). The result showed that while the Nu number increases with increasing Re number , the most efficient case is Dimpled Tube ( DT ) 9, and the highest value of performance evaluation criteria (PEC) has been obtained at phi= 2.0 vol.%. Compared with the water, the highest Nu number value has been obtained as 3.34% increased at Re = 20 0 0 and phi= 2.0 vol.%. When compared to the DT9 and Smooth Tube ( ST ) 1 where water was used as the working fluid at Re = 20 0 0 and phi= 2.0 vol.%, the PEC value increased by 8.66% and 110.31%, respectively. In addition, the bottom wall of the DT9 case performs higher convective heat transfer rate than the top wall.(c) 2022 Elsevier Ltd. All rights reserved.
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    Entropy generation of ferronanofluid flow in industrially designed bended dimpled tube
    (Elsevier, 2023) Gürsoy, Emrehan; Pazarlioglu, Hayati Kadir; Gürdal, Mehmet; Gedik, Engin; Arslan, Kamil
    In this study, numerical analyses were conducted on bended tube with different bending radius and pitch ratios of dimpled fin under different Dean numbers from 9.1 to 301.2. The study examined in bended tube containing three dimple pitch ratios (P/d = 6.0-7.5-9.0) carried out under uniform heat flux of 600 W/m2 and different nanofluid volume fractions of Fe3O4/H2O (0.0 <= phi <= 2.0 %). The thermo-hydraulic performance and entropy generation of bended tubes were investigated. The results showed that Case 10 provided the highest Nu using H2O compared to Case 16, this enhancement was realized as 17.56 %. When nanofluid was used, the highest Nu was obtained at phi = 2.0 % volume fraction in Case 7 by 24.47 % in comparison with non-DT at Dn = 245.9. The highest PEC value of Case 7 using phi = 2.0 % was monitored as 1.11 at Dn = 245.9. Compared to the frictional and total EnGs of P/d = 6.0 and 9.0, the frictional and total EnGs of P/d = 6.0 show a decrease of 10.05 % and 9.60 %, respectively.
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    Evaluation of nanoparticle shape factor on a laminar forced convective heat transfer characteristics of various nanofluids flow in a tube using single-phase numerical model
    (Taylor & Francis Inc, 2024) Tastan, Gizem; Gursoy, Emrehan; Alakour, Abdullah; Gedik, Engin
    Nanotechnology is advantageous in improving thermophysical properties and enhancing heat transfer rate compared with conventional fluids due to their superior thermophysical properties. These properties vary with many parameters such as concentration and shape. In this study, the effect of nanoparticles shape is numerically explored on heat transfer performance under a laminar flow regime (Re=500 and 2000) through the smooth tube. Heat transfer enhancement capability of the nanoparticle shapes with targeted reference to average Nusselt number, average Darcy friction factor, pumping power, and performance evaluation criterion have been investigated. Three types of nanofluids (Fe3O4/water, Al2O3/water, and GO/water) with various nanoparticle shapes (brick, cylindrical, platelet, and spherical) and different nanoparticle volume fractions (phi=1.0, 2.0, 3.0, and 4.0%) have been used as heat transfer fluid in analyzes. Numerical results show that heat transfer performance was greatly influenced by changing nanoparticle shapes. The highest average Nusselt number was obtained for GO/water nanofluid with platelet nanoparticle shape and phi=4.0%. Compared to water, Fe3O4/water, and Al2O3/water, the average Nusselt number in GO/water increased by 64.34%, 54.02%, and 43.41%, respectively. The highest performance evaluaton criterionwas obtained for the GO-water nanofluid with platelet nanoparticle shape at Re=2000. On the other hand, it is found that the Fe3O4/water nanofluid with platelets nanoparticle shape causes the highest pumping power compared with other analyzed nanofluids.
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    An experimental and artificial neural network investigation on the laminar flow of magnetorheological fluids through circular pipes
    (Elsevier, 2022) Gedik, Engin; Kurt, Huseyin; Pala, Murat; Alakour, Abdulla
    Fluids can change their physical properties when they are exposed to magnetic fields. Magnetorheological (MR) fluids are classified as smart materials because their viscoelastic properties can increase by the application of the magnetic field. Accordingly, they are used in different engineering applications such as flow control and vibration damping. In this study, three different types of MR fluids flow in circular pipes with diameters of 10 and 15 mm and length of 300 mm were experimentally investigated with and without applying the magnetic field. An electromagnetic device was designed and manufactured in order to create a magnetic field induction for experiments. Throughout the experiments, the range of magnetic field induction value was B = 0-0.15 T, increased to 0.01 T. Based on the results obtained by the experimental study, it can be asserted that applying the magnetic field prompted an increase in the viscosity of MR fluids, leading to decreasing flow velocity. At B = 0.15 T, which is the highest value of the magnetic field, the flow velocity values dropped by 95%. Subsequently, the artificial neural networks algorithms are used in accordance with the obtained results to develop a correlation that clarifies the effect of the magnetic field on the flow velocity. The results show that the experimental and ANN models perform very similarly, and the ANN algorithm yields better results as a tool to predict the MR fluid flow behavior.
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    Experimental and numerical study on ferrohydrodynamic and magneto-convection of Fe3O4/water ferrofluid in a sudden expansion tube with dimpled fins
    (Elsevier, 2024) Guersoy, Emrehan; Gurdal, Mehmet; Gedik, Engin; Arslan, Kamil; Dagdeviren, Abdullah
    Background: This study experimentally and numerically addresses magnetohydrodynamic forced convection including dimpled fins, Fe3O4/water ferrofluid, and DC magnetic field. In this research, focusing on the thermohydraulic performance improvement of a sudden expansion tube. It has been used different inlet diameters, dimple sizes, ferro nanoparticle concentrations, and magnetic field strengths to examine the heat transfer and fluid dynamics characteristics of the system. Methods: The study consists of two parts, i) experimental and ii) numerical. Steady-state, incompressible, Newtonian flow were considered but chemical reaction, viscous dissipation, buoyancy, and radiative heat transfer were neglected in this study. On the other hand, numerical solutions were carried out for single-phase method. This study was first compared with the studies in the literature on the flow in a sudden expansion tube without dimpled fins and the error rate was found to be less than 10%. In the analysis, dimpled fins with d=3, 5, and 7 mm at each P=15 mm (P/d=5.0, 3.0, and 2.14) have been used. As working fluid, Fe3O4/water ferrofluid with volume concentration of phi=1.0 % and 2.0% have been analyzed. Additionally, DC magnetic fields, which strength of Ha=0.1, 0.3, 0.5, 1.1, 3.2, and 5.3 (B =0.01, 0.03, 0.05, 0.1, 0.3, and 0.5T), have been applied on the sudden expansion tube surface as external force. Significant findings: Dimpled fins enhance the heat transfer by disrupting the boundary layer and forming secondary flows, while the ferrofluid increases the thermal conductivity and viscosity of the base fluid. Based on these explanations, dimpled fins increased the convective heat transfer rate at the rate of 96.0% compared with smooth tube. In addition, Fe3O4/water ferrofluid with phi=2.0 % performed the highest performance and performance evaluation criteria increased by 8.5%. The magnetic field also contributes to the heat transfer enhancement by inducing Lorentz force and mixing the flow. Excessive increasing of magnetic field strength adversely affected the system performance, and the highest performance evaluation criterion is acquired at Ha=3.2 by increasing 3.9%. Compared with smooth tube, compound effect of dimpled fins, Fe3O4/water ferrofluid, and magnetic field improved the average Nusselt number and performance evaluation criterion at the rate of 279.8 % and 207.9%, respectively.
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    Experimental Investigation of a Household Refrigerator Performance Using Chimney-Type Condenser
    (Springer Heidelberg, 2016) Gedik, Engin; Kilicaslan, Erdogan; Acar, Bahadir; Ergun, Alper; Ozbas, Engin
    In this study, the condenser unit was investigated experimentally in order to search for the effect of using chimney on the performance of a household refrigerator charged with 139 g of R134a refrigerant. An experimental design based on chimney-type condenser has been developed, and three chimneys having different size were produced. A series of measurements were conducted over the climatic conditions of Karabuk/Turkey, and results show that the efficiency and energy consumption of the refrigerator vary with the chimney height. Results showed that the best performance observed was for the 170cm chimney height. Energy consumption of natural convection with chimney was found less than that of natural convection by 5 and 10% for the loaded and unloaded situations of the refrigerator.
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    EXPERIMENTAL INVESTIGATION OF COLLECTOR EFFICIENCIES ON SEPARATED AND CONNECTED HEAT PIPES
    (Gazi Univ, Fac Engineering Architecture, 2008) Acar, Bahadir; Oz, Etem Sait; Gedik, Engin
    The aim of study is to determine the effect of heat pipe systems to collector efficiency at solar collectors used in supplying hot water. For this purpose, two different collectors as the connected heat pipe and separated heat pipe have been produced. The experimental studies with the collectors have been conducted in Karabuk city environment. The experiments have been completed in six days. The collector efficiencies have been calculated by measuring temperature of water tanks, ambient temperature and solar radiation in both collectors. As a result, while average efficiency of the connected heat pipe collector is 57.6%, average efficiency of the separated heat pipe collector is 48.5%
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    Experimental Investigation of Module Temperature Effect on Photovoltaic Panels Efficiency
    (Gazi Univ, 2016) Gedik, Engin
    A Photovoltaic module efficiency is mainly depend on the ambient temperature, module temperature, incoming solar radiation intensity and photovoltaic material composition. In the present work, the effect of module temperature on the photovoltaic (PV) panel efficiency was investigated experimentally. Incoming solar radiation on the PV surface (I), ambient temperature of the panel (Ta), back surface temperature of the panel (Tp), voltage and current are the main parameters measured during the experiments. In the experimental system the area that PV module placed have been adjusted four different ambient air temperature as 10, 20, 30 and 40 degrees C. PV module efficiencies are calculated with using obtained experimental data. According to the computations the module efficiency was 12.07% for the 14.9 degrees C of Tp while it was found as 10.7% for the 51.3 degrees C of Tp. It was observed that increasing of PV module temperature decreases efficiency.