Yazar "Erdinc, Mehmet Tahir" seçeneğine göre listele
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Öğe A study on the combination of crystallization-controllable phase change materials and solar-assisted heat pump for electricity demand shifting in space heating(Pergamon-Elsevier Science Ltd, 2025) Kutlu, Cagri; Erdinc, Mehmet Tahir; Dik, Abdullah; Chen, Ziwei; Lyu, Qinghua; Su, Yuehong; Riffat, SaffaSupercooled phase change materials offer a promising solution for space heating due to their ability to release latent heat upon crystallization initiation, even when stored at ambient temperatures. This unique property makes them ideal for solar-assisted space heating, where external activation enables on-demand heat release, addressing the critical need for energy-efficient heating solutions. In this study, a system promoting demand shifting is proposed, aiming to transfer energy consumption from morning and evening peak periods to daytime and high solar irradiance days, thereby enhancing the efficiency of solar heat pumps and reducing grid stress through the use of supercooled crystallization-controllable phase change materials. A model was developed, consisting of evacuated tube collectors, a buffer tank, heat storage tanks with crystallization-controllable phase change material, and a building heating demand model. The study introduces a novel system control methodology, focusing on an effective operation of tank shifting based on the heating requirement and solar energy availability. Real weather data were used to calculate system performance. With 50 m2 of collectors, a 1000-liter buffer tank, and a heat pump with a maximum output of 7 kW, the heat storage tanks are charged and discharged following the developed operational methodology. The system achieved a weekly coefficient of performance of 3.56 and successfully shifted electricity demand to solar hours, with only 28.5% of the total consumption occurring during domestic morning and evening peak times.Öğe An optimization study on thermo-hydraulic performance arrays of circular and diamond shaped cross-sections in periodic flow(Pergamon-Elsevier Science Ltd, 2021) Erdinc, Mehmet Tahir; Aktas, Arif Emre; Kuru, Muhammet Nasif; Bilgili, Mehmet; Aydin, OrhanIn this study, thermo-hydraulic characteristics of arrays of circular and diamond shaped cross-sections in periodic flow are investigated numerically. The main purpose of this study is to configure diamond shaped cross-sections in order to obtain better thermal performance compared to circular shaped cross-section. The optimization frameworks are constructed by using multi-objective genetic algorithm (MOGA) for both circular and diamond shaped cross-sections to obtain maximum heat transfer and minimum pressure drop while keeping the mass flow rate constant. The study can be divided into two parts: Firstly, an optimization study is carried out to achieve an optimum design for the circular type. Later, a new optimization scheme is constructed where the optimum design of circular type's heat transfer and pressure drop values are given as constraints. Thus, the optimization algorithm seeks better thermal performances with respect to the circular one. Moreover, optimum designs are illustrated graphically and given in the tabular form. Compared to circular geometries, it is found that the average Nusselt number of diamond shaped geometry can be increased by 10.11%, while pressure drop and volume of diamond shaped geometries are reduced by 11.90% and 52.76%, respectively.Öğe Comparative Analysis of Solar Photovoltaic/Thermal Assisted Heat Pump Systems Coupled with PCM Storage and EV Charging with Reference to the UK's National Carbon Intensity(Mdpi, 2025) Kutlu, Cagri; Dik, Abdullah; Erdinc, Mehmet Tahir; Su, Yuehong; Riffat, SaffaEmerging trends in heat pump (HP) and electric vehicle (EV) adoption within communities aim to reduce carbon emissions in the heating and transportation sectors. However, these technologies rely on grid electricity, whose carbon intensity varies over time. This study explores how the carbon-saving potential of these technologies can be further enhanced through demand-shifting operations and renewable energy integration. The research compares photovoltaic-thermal (PV/T) and hybrid solar heat pump systems that integrate EV charging and PCM-enhanced heat storage to improve space heating efficiency under low solar irradiance in the UK while reducing CO2 emissions. The study simulates solar collector configurations and sizes, combining PV modules and heat pumps to enhance system performance. Control systems synchronize operations with periods of low grid CO2 intensity, minimizing the environmental impact. The analysis evaluates PV/T systems, separate PV and thermal collectors, highlighting their energy efficiency and CO2 reduction potential. Control systems further optimize HP operation and EV charging during periods of high renewable energy availability, preventing uncontrolled use that could result in elevated emissions. Using real weather data and a detailed building model, the findings show that a solar-assisted HP with 100% thermal collectors achieves a daily COP of 3.49. Reducing thermal collectors to 60% lowers the COP to 2.57, but PV output compensates, maintaining similar emission levels. The system achieves the lowest emission with high-efficiency evacuated flat plate PV/T collectors.Öğe Computational thermal-hydraulic analysis and geometric optimization of elliptic and circular wavy fin and tube heat exchangers(Pergamon-Elsevier Science Ltd, 2023) Erdinc, Mehmet TahirThe three-dimensional (3D) fluid flow and heat transfer analysis and geometric optimization of two rows circular and elliptic wavy fin and tube heat exchanger (FTHE) are numerically examined for staggered arrangement. Numerical optimization studies are carried out with modeFRONTIER 2021R3 commercial software and computational fluid dynamics (CFD) analysis are conducted with help of the ANSYS Fluent R2021a which is based on the finite volume method under the assumptions of incompressible, steady and turbulent flows, and conjugate heat transfer. The circular wavy FTHE is validated with the experimental data that is conducted in the literature. In the present work, two optimization cases are solved: (1) unconstrained optimization of circular wavy FTHE (2) constrained optimization of elliptic wavy FTHE. The optimization problems have more objectives, so they are treated as multi-objective design problems. The objectives of unconstrained optimization of circular wavy FTHE case are to obtain maximum heat transfer, minimum pumping power and minimum volume. The objectives of constrained optimization of elliptic wavy FTHE case are the maximization of heat transfer and minimization of pumping power, where the constraints are given using the optimum design values of circular case to get better designs. The performance of the circular and elliptic wavy FTHE is compared in tabular and graphical forms in terms of Colburn factor j, friction factor f, heat transfer, pumping power, fin efficiency, volume, and thermal-hydraulic performance (THP) parameter. The pumping power is seen to be reduced when elliptic geometries are used in FTHEs. This is due to the streamlined shape of tubes, which causes delays in the separation point and reduction of vortices in the wake region. For the optimum design chosen from Pareto designs, elliptic wavy FTHE outperforms circular wavy FTHE in terms of THP and fin efficiency by 111.9% and 3.2%, respectively.Öğe Evaluate the validity of the empirical correlations of clearance and friction coefficients to improve a scroll expander semi-empirical model(Pergamon-Elsevier Science Ltd, 2020) Kutlu, Cagri; Erdinc, Mehmet Tahir; Li, Jing; Su, Yuehong; Pei, Gang; Gao, Guangtao; Riffat, SaffaThis study presents a scroll expander modelling methodology for small scale power generation systems by combining scroll geometry and semi-empirical model. Although the semi-empirical model is quite popular, its dependence on several experimentally-determined scroll geometrical and operational parameters makes this approach inflexible for different capacities and operating conditions. Some studies have sought to improve its flexibility in terms of using different working fluids and more accurate empirical parameters, however, those improved models still depend on a considerable number of experimentally-obtained scroll parameters. Therefore, in this study, a practical methodology for a simpler semi-empirical model combined with the operational flexibility of the scroll geometry is presented. Firstly, the flow rates of mainstream and leakage flows are analysed, where a correlation between scroll clearance and pressure ratio is determined. Secondly, a simpler approach to the semi-empirical model of scroll expander is proposed, whereby dependent parameters have been reduced to two parameters by using scroll geometrical calculations. The model is further improved to predict the rotational speed and electricity output by considering the overall friction coefficient of the coupled expander-generator unit. The findings are then compared with the results of an experimental study. The results show that the effective clearance values between scrolls vary according to pressure ratios, increasing from 20 mm to 34 mm. Mass flow rate can be predicted within 10% deviation from the experimental results for the same inlet conditions and rotational speed at a transient state. Additionally, considering steady state conditions, modelling results show that the rotational speed and electricity output can also be predicted within 8% and 7.5% of deviation, respectively. (C) 2020 Elsevier Ltd. All rights reserved.Öğe Investigations of flow structures and performances of heat transfer in semi-circular grooved ducts by applying field synergy principal analysis: An experimental and numerical study(Pergamon-Elsevier Science Ltd, 2023) Tokgoz, Nehir; Erdinc, Mehmet Tahir; Kaska, Onder; Sahin, BesirThe present study aimed at investigating the flow structure and heat transfer mechanism through the corrugated channel experimentally and numerically. Particle imaging velocimetry (PIV), which can give detailed information about the wake and shear flow regions, was used for the experiments. The experimental and numerical works were performed considering Reynolds numbers in the range of 6 x 103 <= Re <= 12 x 103 and 3 x 103 <= Re <= 2 x 104, respectively. In the numerical part, aspect ratios (R/hp) of examined grooves have been chosen as 0.1, 0.2, and 0.3, and for the experiment, only one aspect ratio was chosen which was 0.3. The experimental studies were conducted regarding different Reynolds numbers as well as the distributions of instantaneous and timeaveraged velocity contours, Turbulence Kinetic Energy, Reynolds shear stress, and vorticity. The standard SST k-omega turbulent method was employed for the case of numerical study to predict the thermal performance (eta) along with Nusselt numbers (Nu) the friction factors (f) and local field synergy angles (alpha, beta) were calculated. As a result, the Nusselt number (Nu) values of the corrugated channels were higher than the parallel plate, and the increment in the Nusselt number initially increased and later decreased with Reynolds numbers for all aspect ratios considered.Öğe Numerical investigation of flow and heat transfer in axially-finned in-line tube banks(Taylor & Francis Inc, 2025) Kuru, Muhammet Nasif; Yilmaz, Alper; Aktas, Arif Emre; Erdinc, Mehmet TahirNumerical analysis of heat and fluid flow over tube bank heat exchangers with axial fins is performed in this work. Finite volume method is used to solve the governing equations numerically. Simulations are carried out in the range of 400-1500 Reynolds number. To ensure the numerical model reliability, unfinned in-line tube bank is simulated and compared with results from the literature. It is shown that the results are in accordance with the experimental studies in the literature. Heat transfer and pressure loss computations are carried out for four different axial and transversal pitch ratios; namely, $$s_L<^>{\rm{*}} = 3$$sL & lowast;=3 and $$s_T<^>{\rm{*}} = 1.5$$sT & lowast;=1.5, $$s_L<^>{\rm{*}} = 3$$sL & lowast;=3 and $$s_T<^>{\rm{*}} = 2$$sT & lowast;=2, $$s_L<^>{\rm{*}} = 5$$sL & lowast;=5 and $$s_T<^>{\rm{*}} = 1.5$$sT & lowast;=1.5, $$s_L<^>{\rm{*}} = 5$$sL & lowast;=5 and $$s_T<^>{\rm{*}} = 2$$sT & lowast;=2. Air and water are used as working fluids for determined mass flow rates where Prandtl numbers are 0.7 and 7, respectively. Moreover, velocity streamlines and temperature contours along the flow field are given. Effects of axial ($$s_L<^>{\rm{*}}$$sL & lowast;) and transversal ($$s_T<^>{\rm{*}}$$sT & lowast;) pitch ratios and fin lengths on the average Nusselt number and friction factor are also presented in graphical forms. It is found that the maximum average Nusselt number is observed at Re = 1500 for the pitch ratios of $$s_L<^>{\rm{*}} = 5$$sL & lowast;=5 and $$s_T<^>{\rm{*}} = 1.5$$sT & lowast;=1.5 where fin length equals to 2D mm. Besides, adding axial-fins to in-line tube bank results in a decrement in friction factors.Öğe Optimization of Heat Transfer and Pressure Drop in Axially Finned Staggered Tube Banks(Taylor & Francis Inc, 2021) Nasif Kuru, Muhammet; Erdinc, Mehmet Tahir; Yilmaz, AlperNumerical optimization of heat and fluid flow over staggered tube banks are investigated for both unfinned and axially finned tube banks. Ansys Fluent software is utilized for numerical computations. To find maximum total heat transfer and minimum volume of tube bank for the given mass flow rate, allowable pressure drop and tube bank effectiveness; A Multi-objective Genetic Algorithm II is used. Optimum designs are given on tabular forms and variations of total heat transfer with total volume are presented. Moreover, effects of transversal and longitudinal pitches on objective functions are graphically demonstrated. In order to confirm reliability of the numerical studies, unfinned staggered tube bank configuration is compared with experimental studies in literature. As a result of optimization studies, axial fin usage results in 42.7% decrement in volume of staggered tube bank with respect to unfinned case, while heat transfer values are equal with maximum obtainable heat transfer rate for the given optimization problem.Öğe Optimizing the tube geometry to enhance thermohydraulic performance of tube bank heat exchanger(Elsevier France-Editions Scientifiques Medicales Elsevier, 2023) Aktas, Arif Emre; Kuru, Muhammet Nasif; Erdinc, Mehmet Tahir; Aydin, Orhan; Bilgili, MehmetIn this study, optimum design parameters of circular, diamond and enhanced shaped geometries for staggered tube banks are explored utilizing a multi-objective genetic algorithm (MOGA-II). For given three geometries, two step optimization studies are compared: (1) circular and diamond shaped geometries, (2) diamond and enhanced shaped geometries. Steady, incompressible, and turbulent flow around three-dimensional numerical models is solved using finite volume method. Initially, using literature experimental data numerical results are validated for circular and diamond geometries. In the optimization studies, maximization of heat transfer and minimization of required pumping power are preferred as objective functions. The results of optimization studies are demonstrated graphically. Furthermore, velocity and temperature distribution for the optimum cases are illustrated. The results of first step optimization studies exhibited that diamond shaped tube bank shows higher heat transfer rate than circular one for the same given volume (156%). Besides, as a result of second step optimization studies, optimal enhanced shaped geometry showed 0.59% higher heat transfer rate, 21.73% lower pumping power requirement and 9.65% lower total tube bank volume than optimal diamond shaped one.Öğe Performance simulation of expander-compressor boosted subcooling refrigeration system(Elsevier Sci Ltd, 2023) Erdinc, Mehmet TahirMany applications have made extensive use of refrigeration systems, which have a high energy requirement. Any improvement on the refrigeration systems can reduce the need for energy demand. A common method to improve the system performance is to subcool the condenser exit temperature and known as subcooling. An expander-compressor booster enhanced subcooling vapor compression cycle is proposed as an addition to the subcooling systems described in the literature. The refrigerant is split into two parts at the condenser exit: one portion expands in the expansion device to reach the necessary subcooling temperature, while the other part goes straight into a separate heat exchanger. Later, this additional refrigerant flows into the other expansion valve, the evaporator, and a booster expander-compressor to increase inlet pressure of compressor. As working fluids, six distinct refrigerants including low global warming potential (GWP) are used (namely R134a, R1234yf, R32, R290, R1270, and R600a) in simulations. The coefficient of performance (COP) and increment in COP values for each refrigerant are computed and graphically displayed for various evaporation temperatures between-10 degrees C and 5 degrees C. Furthermore, the heat exchanger analysis of subcooling heat exchanger is performed to compare heat transfer surface area and pressure drop for each refrigerant. Results indicate that R1234yf achieves the greatest performance with an increase in COP by 16.7, 19.1 and 21.8% depending on the mechanical efficiencies of the expander and compressors and as well as isentropic efficiency of the expander. By utilizing an expander -compressor with higher or lower mechanical and isentropic efficiencies, these enhancements can be raised or lowered. Heat exchanger analyses show that the pressure drop in the exchanger does not significantly affect the performance of the system.Öğe The role of nozzle position and channel aspect ratio in thermal management of electronic modules(Elsevier B.V., 2023) Albayrak, Melisa; Sarper, Bugra; Erdinc, Mehmet Tahir; Aydin, OrhanIn this paper, cooling of electronic modules by a series of impinging jets is studied numerically and experimentally. The study investigates the effects of nozzle position (sj/b = 0 − 0.25 − 0.5) and channel aspect ratio (H/Dj = 3 − 4 − 5) on surface temperatures, local and average heat transfer characteristics and flow dynamics. The numerical analyses are conducted using the ANSYS Fluent software, and the numerical results are verified using experimental measurements. The study's findings indicate that the displacement of the nozzles has a notable impact on the location and sizes of the vortex cells around the modules. This alteration influences the rate of convection heat transfer from the modules’ surfaces. It is concluded that increasing the channel aspect ratio leads to a reduction in convective heat transfer. The highest cooling performance is achieved in the scenario where the aspect ratio (H/Dj) is 3 and the dimensionless nozzle position (sj/b) is 0.5. However, in terms of temperature uniformity, this is H/Dj = 3 with sj/b = 0. © 2023 The AuthorsÖğe Thermal Management and Entropy Minimization of Plain and Modified Shaped Plate Fin Heat Sinks Using Multi-Objective Genetic Algorithm(Asme, 2024) Kuru, Muhammet Nasif; Unal, Saban; Efe, Metin; Duman, Necdet; Karasu, Ilyas; Erdinc, Mehmet Tahir; Aydin, OrhanIn this study, an optimization methodology is followed in order to explore better form of heat sinks which improve thermal performances. Optimum designs of plate fin heat sinks (PFHSs) and modified shaped plate fin heat sinks (MS-PFHSs) are numerically investigated. The objective functions are minimizations of base plate temperature, entropy generation and mass. For both PFHSs and MS-PFHSs, optimization variables include inlet velocity (V-in), fin height (H-fin), and number of fins (N-L). Plate fin form is adjusted for MS-PFHSs by adding two optimization variables: the rib height (H-rib) and the number of patterns in the flow direction (W-p). For the multi-objective optimization problems, the maximum base plate temperature limit (T-base<70 degrees C) is used. The multi-objective genetic algorithm (MOGA) is used to solve optimization problems, and three-dimensional parametric models for numerical optimization work are examined using the finite volume approach. The flow is steady, incompressible, and turbulent, and heat transfer in the heat sink is represented by conjugate heat transfer (CHT). It is shown that MS-PFHSs outperform in terms of the analyzed objective functions. For the optimum designs, T-base values of MS-PFHS and PFHS are 60.23 degrees C and 65.25 degrees C, respectively, while the mass values are same. The results also indicate that T-base obtained in the optimum design of MS-PFHS is 7.69% lower than that obtained in the optimum design of PFHS.Öğe Two-evaporator refrigeration system integrated with expander-compressor booster(Elsevier Sci Ltd, 2023) Erdinc, Mehmet TahirTwo-evaporator refrigeration systems are commonly used in many practical applications where two different temperatures are required. Improving the performance of these systems can contribute to energy efficiency. Expansion recovery has been extensively utilized in order to maintain higher performance and the most commonly used method is adopting an ejector instead of expansion valve. In this work, different from the previous studies, an expander-compressor booster is introduced to the system instead of an expansion device to improve coefficient of performance (COP) and second law efficiency of the two evaporator refrigeration system. Parametric studies are conducted for different mass flow rate ratios, condensing, evaporating, superheating temperatures on COP and relative increment in COP (COP*) values are plotted. An internal heat exchanger (IHX) is also added to evaluate whether it helps or worsens the system performance. Moreover, the impact of different refrigerants (R134a, R1234yf, R290, R717, R32 and R410A) on the results is discussed. The results for R1234yf showed that the expander-compressor booster increases the performance of the system and second law efficiency by 38% when mass flow rate ratios are identical. This increment can be increased at lower mass flow rate ratios. Addition of the IHX contributes the COP*. It has also been observed that the refrigerant type has a significant impact on the results.
