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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 BORU DEMETİ ISI DEĞİŞTİRİCİLERİNDE FARKLI BORU ÇAPI KULLANIMININ AKIŞ VE ISI TRANSFERİNİ İYİLEŞTİRMEYE ETKİSİ(2023) Kuru, Muhammet Nasif; Erdinç, Mehmet Tahir; Karasu, İlyas; Ünal, ŞabanBoru demeti ısı değiştiricilerinde, boruların içindeki akışkana çapraz yönde etrafından geçirilen başka bir akışkan ile ısı transferi gerçekleştirilir. Boru dışından çapraz yönde geçirilen akışkan çoğunlukla gaz akışkanlardır. Art arda yerleştirilen borularda, en fazla ısı transferi çoğu kez birinci boruda elde edilmektedir. Birinci borudan sonra ısı ve akış karakteristiği birbirine benzer hal almaktadır. Bu durumda, hız ve sıcaklık konturlarının tekrarlanması ile periyodik akış elde edilmiş olur. Ardışık olarak gelen borularda sınır tabakanın sürekli olarak yenilenmesini sağlamak, diğer borularda birinci borudaki gibi yüksek ısı transferi elde edilmesine imkân tanıyacaktır. Isı transferi iyileştirilirken en önemli sorun basınç düşümünün de artmasıdır. Bu çalışmada düzgün sıralı dizilişe sahip boru demetinde, art arda yerleştirilen dört farklı çaptaki borular kullanılarak, ısı transferinin arttırılması ve basınç düşümünün azaltılması amaçlarıyla sayısal optimizasyon yapılmıştır. Karşılaştırmalar, ısı transferi yüzey alanının sabit, borular arasındaki boyuna ve enine mesafelerin aynı olduğu varsayılarak yapılmıştır. Düzgün sıralı dizilişe sahip boru demetinde ardışık olarak yerleştirilen dört adet borunun çaplarının D_1=5 mm,D_2=15 mm,D_3=6 mm,D_4=14 mm olması durumunda ısı transferi %14.5 oranında artarken, basınç düşümü de %377 oranında artmıştır.Öğe Determination of the Optimum Operating Conditions and Geometrical Dimensions of the Plate Fin Heat Sinks Using Teaching-Learning-Based-Optimization Algorithm(Asme, 2023) Kuru, Muhammet NasifElectronic devices must be effectively cooled for long-term reliability and safe operation. It is essential to determine operating conditions and optimum dimensions of cooling devices in terms of device weight, space, cost, and sound limits. Plate fin heat sinks (PFHSs) are frequently used for cooling electronic devices. Optimum thermal designs of PFHSs are explored in this study using a teaching-learning-based-optimization (TLBO) algorithm where entropy generation ( S (gen) ) minimization, profit factor ( J ) maximization, base plate temperature excess ( ? (b) ) minimization, total mass ( mass ) minimization, and total volume ( volume ) minimization are the objective functions of the constrained single-objective optimization problems. For further investigations of the entropy generation minimization method, three different optimization problems are also studied: minimization of thermal resistance ( R (th) ), minimization of pressure drop ( ?P ), and minimization of pumping power ( W (pump) ). Each optimization problem is subjected to a constraint, namely, temperature excess of base plate temperature ( ? (b) ) should be lower than 10 K. Four optimization variables are considered which are the number of plate fins (N), freestream velocity ( V (f) ), the thickness of the fin ( t (fin) ), and height of the fin ( H (fin) ). Optimum configurations belonging to the different optimization problems are compared, and the effect of each optimization variable on the objective functions is discussed in detail. It is found that one can obtain optimum operating conditions and geometrical dimensions of the PFHSs according to the design objective, i.e., minimum mass requirement, space limitation, minimum base plate requirement, etc. As a result, the optimum designs of the studied cases are different which are superior to each other in terms of design targets.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 and fluid flow over curved trapezoidal winglet pair type vortex generators with one-row and three-row(Springer, 2023) Kuru, Muhammet NasifPassive heat transfer enhancement methods are frequently chosen to achieve higher thermo-hydraulic performances in engi-neering applications because they do not require external energy. One of the most popular passive methods for increasing heat transfer and improving the cooling effects of heat transfer surfaces is the use of vortex generators (VGs). However, the pressure drop generated by the usage of VGs must be controlled. This work is interested in the number (one, three) and geo-metric dimensions of VGs in the rectangular channel. Numerical optimization studies are carried out for heat and fluid flow over curved trapezoidal winglet pair (CTWP) type VGs for one-row and three-row to obtain optimum geometric dimensions of one-row and three-row of CTWP types VGs in the rectangular channel under incompressible and turbulent flow and con-jugate heat transfer assumptions. Heat transfer and pressure drop values are compared in terms of j/j(0) (the ratio of Colburn factor with CTWP to without it) and f/f0 (the ratio of friction factor with CTWP to without it), respectively. The optimiza-tion problems are solved with no constraints in the workflows. Multi-Objective Genetic Algorithm (MOGA) is used for the computations where the maximization of j/j0 and minimization of f /f0 are the two objective functions. Thermo-hydraulic performances ( R = (j/j(0))/(f/f(0))) of the studied cases are also compared. The optimization variables are inclination angle (alpha), attack angle (beta), width / length ratio (b / a), height of the VG (h), interval between VG pair's front edges ( S1 ) for both one-row and three-row cases, also longitudinal spacing between each VG pair (SL) is added as an optimization variable for three-row case. It is found that three-row of CTWP type VGs can increase j/j(0) also increase f/f0, i.e., heat transfer enhance-ment is obtained with a pressure drop increment disadvantage and it is possible to achieve 24.05% heat transfer enhancement with the penalty of 17.27% pressure drop increment as compared to one-row of CTWP type VGs. Furthermore, the fact that the pressure drop has the maximum value does not mean that the heat transfer value is the maximum.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 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.
