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Öğe Artificial neural network approach for evaluation of temperature and density profiles of salt gradient solar pond(Elsevier Sci Ltd, 2007) Kurt, H.; Atik, K.; Ozkaymak, M.; Binark, A. K.The purpose of this study is to evaluate temperature and density profiles of an experimentally investigated salt gradient solar pond (SGSP) by using artificial neural network ( ANN). The input parameters of the ANN are solar pond depth, ambient temperature, radiation absorption coefficient of salty solution in the pond, initial density values of the pond and time of day. The output parameters of the ANN are temperature and density profiles in the pond. The experimental data set consists of 168 values. These divided into two groups, of which the 134 values were used for training/learning of the network and the rest of data ( 34 values) for testing/validation of the network performance. According to the ANN predicted results compared to the experimental results, the mean relative error (MRE) is 2.30% for temperature and 0.63% for density. The correlation coefficients (R-2) between the experimentally measured and the ANN predicted results are 0.9632 for temperature and 0.9855 for density in the test/validation data set. The calculated errors of proposed ANN model are in acceptable ranges. These results indicated that the ANN approach could be considered as an alternative and practical technique to evaluate the temperature and density profiles of a SGSP.Öğe CFD simulation of magnetohydrodynamic flow of a liquid- metal galinstan fluid in circular pipes(2013) Gedik, E.; Kurt, H.; Recebli, Z.In this paper, the steady, laminar, incompressible viscous flow of an electrically conducting liquid-metal fluid is investigated numerically in acircular non-conducting pipe. The considered work fluid is Galinstan (GaInSn, i.e. Gallium-Indium-Tin). Such a liquid metal is subjected to a constantpressure gradient along the axial direction and a uniform transverse magnetic field in the spanwise direction. Numerical simulations are performed by means of the Fluent commercial software (used to solve the governing three dimensional fluid dynamics and electromagnetic field partial differential equations iteratively). The magnetic field induction, B, takes values between 0 and 1.5 T with a 0.5 T step size. The fluid velocity is found to decrease with an increase in the intensity of the applied magnetic field. The results, plotted as a function of system parameters, are critically discussed with respect to potential industrial applications.©2013 Tech Science Press.Öğe CFD Simulation of Magnetohydrodynamic Flow of a Liquid-Metal Galinstan Fluid in Circular Pipes(Tech Science Press, 2013) Gedik, E.; Kurt, H.; Recebli, Z.In this paper, the steady, laminar, incompressible viscous flow of an electrically conducting liquid-metal fluid is investigated numerically in a circular non-conducting pipe. The considered work fluid is Galinstan (GaInSn, i.e. Gallium-Indium-Tin). Such a liquid metal is subjected to a constant pressure gradient along the axial direction and a uniform transverse magnetic field in the spanwise direction. Numerical simulations are performed by means of the Fluent commercial software (used to solve the governing three dimensional fluid dynamics and electromagnetic field partial differential equations iteratively). The magnetic field induction, B, takes values between 0 and 1.5 T with a 0.5 T step size. The fluid velocity is found to decrease with an increase in the intensity of the applied magnetic field. The results, plotted as a function of system parameters, are critically discussed with respect to potential industrial applications.Öğe CFD simulation of magnetohydrodynamic flow of liquid- metal in circular pipes(2012) GedIk, E.; Kurt, H.; ReceblI, Z.In this paper, the steady, laminar, incompressible viscous flow of electrically conducting liquid-metal fluid in circular non-conducting pipe is considered under the influence of a uniform transverse magnetic field with pressure gradient. GaInSn (Gallium-Indium-Tin) liquid metal fluid is used as operating fluid. A uniform transverse external magnetic field is applied perpendicular to the flow direction. The simulations are performed by means of Fluent MHD module based on solving the magnetic induction equation. Fluent 13.0, the finite element software is used to calculate the three dimensional fluid dynamics and electromagnetic field partial differential equations iteratively. The magnetic field induction, B, take values between 0 and 1.5 T with 0.5 T step size, have been applied for determine B effects on liquid-metal flow. Results, obtained from numerical study was plotted graphically and disgusted in the present paper. The velocity of fluid is found to decrease with the increasing of the magnetic field.Öğe Comparison of different cooling options for photovoltaic applications(Institute of Electrical and Electronics Engineers Inc., 2018) Ökkul, F.B.; Kayabasi, E.; Çelik, E.; Kurt, H.; Arcaklioglu, E.A temperature increase plays a negative role on photovoltaic (PV) panel conversion efficiency by increasing recombination rates. In this study, air- and water-cooling options were simulated to investigate the efficiency behavior of a specific PV panel made of heterojunction Silicon (Si) whilst PV panel was cooling in operation by using ANSYS-FLUENT. For air cooling, two different options were suggested: air cooling with four different flow speeds and air cooling with a heat sink addition with three different flow speeds. As for water-cooling three flowrates were considered. Temperature distributions of PV panels for the all cooling options were demonstrated as a function of flow velocity of air and flowrate of water for different cooling conditions and compared with each other. The influence of temperature difference on panel conversion efficiency were also discussed. As a result, heat sink with a proper flow arrangement cooling option showed the best performance in terms of minimum material, minimum cost and minimum complexity with the 42 °C, 38.4 °C, 35.9°C average surface temperatures and 20.9%, 21.3%, 21.5% panel efficiencies. © 2018 IEEE.Öğe Experimental investigation of thermal performance of hot box type solar cooker(Elsevier Sci Ltd, 2006) Kurt, H.A cylindrical shaped box type solar cooker was constructed and its thermal performance was tested under the prevailing weather conditions in Karabuk, Turkey. Experiments were conducted on a single glazed cooker with a plane reflector and one cooking pot during August 2004. The international test procedure was applied to the solar cooker and the stagnation temperature, and the sensible water heating tests were performed to predict the heating characteristic curves. The results obtained from the tests were used to calculate the two figures of merit, overall thermal efficiency, specific and characteristic boiling times as well as the cooking power. The first figure of merit obtained was greater than value suggested in the international standard test procedure. The second figure of merit was found to increase almost linearly with the quantity of water. These figures of merit are then used to predict the characteristic heating curves. Good agreement exists between the predicted heating curves and the experimental results. The solar cooker with 1 m(2) aperture area is able to boil 1 kg water in 13.6 min with 30.5% daily thermal efficiency.Öğe Investigating the effects of cooling options on photovoltaic panel efficiency: State of the art and future plan(Institute of Electrical and Electronics Engineers Inc., 2018) Özkul, F.B.; Kayabasi, E.; Çelik, E.; Kurt, H.; Arcaklioglu, E.Currently, cooling of photovoltaic (PV) panels, a significant issue due the negative effect on panel efficiency, is subjected to intensive researches. For this purpose, numerous researches on cooling methods are performed to keep the panel efficiencies around the design values. In this study, a comprehensive literature review was presented to give the status of the technological improvement in cooling options. In addition, strong and weak aspects of the studies were discussed, and advantageous methods were emphasized for the further application of PV panels. Finally, future perspective of PV panel cooling studies was explored with proper cooling options in lower operating temperatures for higher operation efficiencies. © 2018 IEEE.Öğe Laminar Forced Convection and Entropy Generation of ZnO-Ethylene Glycol Nanofluid Flow through Square Microchannel with using Two-Phase Eulerian-Eulerian Model(Isfahan Univ Technology, 2019) Uysal, C.; Arslan, K.; Kurt, H.In this paper, convective heat transfer and entropy generation of ZnO-EG nanofluid flow through a square microchannel are numerically investigated. Flow is modelled by using Eulerian-Eulerian two phase flow model. Nanoparticle volume fraction of ZnO-EG nanofluid ranged between %1.0 and %4.0. As a result, it is found that the convective heat transfer coefficient of flow increased from 9718.15 W/m(2) K to 23010.79 W/m(2) K when 4.0% ZnO nanoparticle addition to pure EG at Re=100. Total entropy generation of ZnO-EG nanofluid decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid. It is also observed that the Bejan number decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid.Öğe Laminar forced convection and entropy generation of ZnO-ethylene glycol nanofluid flow through square microchannel with using two-phase Eulerian-Eulerian model(Isfahan University of Technology, 2019) Uysal, C.; Arslan, K.; Kurt, H.In this paper, convective heat transfer and entropy generation of ZnO-EG nanofluid flow through a square microchannel are numerically investigated. Flow is modelled by using Eulerian-Eulerian two phase flow model. Nanoparticle volume fraction of ZnO-EG nanofluid ranged between %1.0 and %4.0. As a result, it is found that the convective heat transfer coefficient of flow increased from 9718.15 W/m2K to 23010.79 W/m2K when 4.0% ZnO nanoparticle addition to pure EG at Re = 100. Total entropy generation of ZnO-EG nanofluid decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid. It is also observed that the Bejan number decreases with increase in nanoparticle volume fraction of ZnO-EG nanofluid. © 2019 Isfahan University of Technology.Öğe Simulation of heat exchangers and heat exchanger networks with an economic aspect(Elsevier - Division Reed Elsevier India Pvt Ltd, 2018) Kayabasi, E.; Kurt, H.Relations between effectiveness (epsilon) and expense coefficients (zeta) were derived, and an economic simulation model was developed to simulate heat exchangers (HE) and HE networks (HEN) in all flow types for the first time. epsilon values of parallel flow, counter flow, cross flow and all HEs under the condition of C-r = 0 were derived in terms of zeta, NTU (Number of Transfer Unit) and minimum heat capacities (C-min). epsilon values obtained from economic calculations were used for developing economic simulation model of HEs. Vectors including outlet temperatures and inlet temperatures of flows were obtained from static simulation to utilize in economic simulation model. Then, case studies were performed with counter flow HE and epsilon values randomly determined in a sample HEN. Use (N), expense (P) and savings (E) of all HEs in a HEN were calculated easily by the way of linear equation systems without any complex processes, iterations, software and special hardware, in terms of both cold and hot flows properties by using economic simulation model. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.Öğe The theoretical and experimental investigation of temperature and salinity gradients in salt gradient solar ponds(2005) Kurt, H.; Özkaymak, M.; Korhan, Binark, V.A.In this study, both experimental and theoretical investigations were carried out in order to determine whether sodium carbonate salt which has not been used up to now for establishing salinity gradients is suitable for establishing salinity gradient in Salt Gradient Solar Pond (SGSP) or not. The heat storage ability of a solar pond was also examined. For this purpose, a small scale pond in the laboratory conditions was constructed for the experimental work and also one dimensional mathematical model for the SGSP's heat and mass transfer was developed. Differential equations obtained through by the developed model were solved numerically using finite difference method. The experimentally and theoretically obtained results showed that in order to establish temperature gradient in the sodium carbonate solution pond, a salinity gradient with salinity of about 12 % needs established.Öğe THERMOECONOMIC ANALYSIS OF A WATER TO WATER HEAT PUMP UNDER DIFFERENT CONDENSER AND EVAPORATOR CONDITIONS(Yildiz Technical Univ, 2019) Aksu, B.; Uysal, C.; Kurt, H.A thermoeconomic analysis of a water to water heat pump are performed under different condenser and evaporator conditions. Experiments are realized for different volumetric inlet temperatures of 14.4, 17 and 19 degrees C and different volumetric flow rates of 50, 100, 150 lt/h for condenser cooling water. Same inlet temperatures with condenser cooling water are used for evaporator water inlet, while constant volumetric flow rate of 100 lt/h is used for each case. Modified Productive Structure Analysis (MOPSA) is used for thermoeconomic analysis. It is found that increases in inlet temperature and in volumetric flow rate cause to decrease in both the unit cost of heat delivered (C-H) and the unit cost of entropy generation (C-S). As a result, in the case of T-in =14.4 degrees C and (for all) over dot = 50 lt/h, C-H and C-S values are obtained to be 0.0489 $/kWh and 0.0221 $/kWh, respectively, while C-H and C-S values are obtained to be 0.0385 $/kWh and 0.0175 $/kWh for T-in =19 degrees C and (for all) over dot = 150 lt/h, respectively.
