Yazar "Kotcioğlu, İsak" seçeneğine göre listele

Listeleniyor 1 - 9 / 9
  • [ X ]
    Öğe
    An experimental investigation of heat transfer enhancement in a rectangular duct with plate fins
    (2009) Kotcioğlu, İsak; Çalışkan, Sinan; Ayhan, Teoman; Başkaya, Şenol
    In this study, using an ideal heat exchanger model, a detailed evaluation of performance parameters in the turbulent regime for the enhancement of heat transfer by using winglet-type vortex generators is carried out. The heat transfer, friction characteristics, and the second law analysis of the convective heat transfer for turbulent flow through a rectangular channel containing built-in wing-type vortex generator have been investigated experimentally in the range of Reynolds numbers between 3000 and 30,000. The installation of the wings is organized, in such a way that periodically interrupted enlarged and contracted channel flow domains are established. Wings were aligned at various angles of ? = 7?20° positively and negatively with the direction of main air flow direction. The highest heat transfer performance was found for a ? = 15° winglet angle. Each winglet pair induces longitudinal vortices behind it, and strong mixing effects occur in a buffer region between divergent and convergent channel arrangements. It was observed that the enhancement of heat transfer caused the increment of the friction coefficient. In addition, the relation of the entropy generation number to effectiveness has been studied under optimal design conditions for divergent and convergent channels on the basis of entropy generation minimization.
  • [ X ]
    Öğe
    Design analysis of impinging jet array heat transfer from a surface with V-shaped and convergent-divergent ribs by the taguchi method
    (Taylor and Francis Ltd., 2016) Çalışkan, Sinan; Nasiri Khalaji, Mansour; Başkaya, Şenol; Kotcioğlu, İsak
    In this work, the effects of the impingement plate geometry, Reynolds number, jet-plate distance-to-jet diameter ratio, and the jet diameter-to-rib height ratio on the impingement jets were investigated using the Taguchi experimental design method. The heat transfer measurements over a surface with V-shaped ribs (V-SR) and convergent-divergent shaped ribs (CD-SR) by a circular impinging jet array were investigated using a thermal infrared camera. Both V-SR and CD-SR configurations, with an angle of 45°, were considered. Both projected and total Nusselt numbers were considered as performance statistics. After the data on each quality characteristic were obtained from the orthogonal arrays, a main effect analysis and analysis of variance (ANOVA) were conducted to determine the parameters that had significant effects on these quality characteristics. The L32 (21 × 43) orthogonal array was selected as an experimental plan for the four parameters. The Taguchi method was applied with an optimization process to reach the maximum heat transfer. Experimental results validated the suitability of the proposed approach. The best heat transfer performance was obtained with the V-SR arrangements. Copyright © Taylor and Francis Group, LLC.
  • [ X ]
    Öğe
    Experimental investigation of a cross-flow heat exchanger with wing-type vortex generators
    (2008) Kotcioğlu, İsak; Çalışkan, Sinan
    In this study, heat and fluid flow in a plate-fin heat exchanger with wing-type convergent-divergent longitudinal vortex generators (CDLVGs) were studied experimentally. A cross-flow plate-type heat exchanger was designed and manufactured in the laboratory. Winglets were aligned with the angle of attack (? = 30°) positively and negatively to the main air flow direction, leading to eventually a better mixing phenomenon. Compared to the plate-fin geometry, the penalty of additional pressure drops of the other vortex generators was relatively insensitive to the change of the Reynolds number. The effects of the CDLVGs for various flow velocities on the cross-flow heat exchanger were investigated experimentally. Heat transfer experiments were performed under three different conditions. The highest heat transfer performance was found when the hot flow clack was half open and the cold flow clack was fully open in the second position. The correlations for the heat transfer coefficients and pressure drop characteristics were obtained as functions of the Reynolds number and the Prandtl number. The relationship between the effectiveness and the number of transfer units (?-NTU) of the cross-flow heat exchanger were determined.
  • [ X ]
    Öğe
    Experimental investigation of heat transfer from different pin fin in a rectangular channel
    (Taylor and Francis Ltd., 2018) Çalışkan, Sinan; Doğan, Ayla; Kotcioğlu, İsak
    In this study, the effect of both hexagonal pin fins (HPFs) and cylindrical pin fins (CPFs) into the rectangular channel on heat transfer augmentation, Nusselt number and friction factor were experimentally investigated. In planning of the experiments, different Reynolds number, pin fin array, pin fin geometry and the ratio of the distance between pin fin spacing (s) to the pin fin hydraulic diameter (s/Dh) were chosen as the design parameters. Air was used as the fluid. The Reynolds number, based on the channel hydraulic diameter of the rectangular channel, was varied from 3188 to 19531. In the experiments, the heating plate was made of stainless steel foil. The foil was electrically heated by means of a high current DC power supply to provide a constantly heated flux surface. The heat transfer results were obtained using the infrared thermal imaging technique. The heat transfer results of the hexagonal pin fins (HPFs) and cylindrical pin fins (CPFs) are compared with those of a smooth plate. Best heat transfer performance was obtained with the hexagonal pin fins. The maximum thermal performance factor ((?), was obtained as Re = 3188, staggered array, s/Dh = 0, ? = 2.28.
  • [ X ]
    Öğe
    Experimental study on the heat transfer and pressure drop of a cross-flow heat exchanger with different pin-fin arrays
    (2011) Kotcioğlu, İsak; Çalışkan, Sinan; Başkaya, Şenol
    In this study, convective heat transfer and pressure drop in a cross-flow heat exchanger with hexagonal, square and circular (HSC) pin-fin arrays were studied experimentally. The pin-fins were arranged in an in-line manner. For the applied conditions, the optimal spacing of the pin-fin in the span-wise and stream-wise directions has been determined. The variable parameters are the relative longitudinal pitch (SL /D = 2, 2.8, 3.5), and the relative transverse pitch was kept constant at ST /D = 2. The performances of all pin-fins were compared with each other. The experimental results showed that the use of hexagonal pin-fins, compared to the square and circular pin-fins, can lead to an advantage in terms of heat transfer enhancement. The optimal inter-fin pitches are provided based on the largest Nusselt number under the same pumping power, while the optimal inter-fin pitches of hexagonal pin-fins are ST /D = 2 and SL /D = 2.8. Empirical equations are derived to correlate the mean Nusselt number and friction coefficient as a function of the Reynolds number, pin-fin frontal surface area, total surface area, and total number. Consequently, the general empirical formula is given in the present form. NuD = a(ReD)b(N tAf/Atotal)c and f = a(Re D)b © 2011 Springer-Verlag.
  • Küçük Resim
    Öğe
    Farklı soğutucular kullanarak CPU'nun ısı boruları ile soğutulması
    (Türk Isı Bilimi Ve Tekniği Derneği, 2009) Kotcioğlu, İsak; Çalışkan, Sinan; Manay, Eyüphan
    Bu çalışma, bilgisayarların soğutulmasında ısı borularının etkin kullanılması ile ilgili yapılan teorik bir çalışmadır. Soğutucu akışkan ısı kaynağından (Central Processing Unit – CPU’dan) ısıyı absorbe eder. Evaporatörde buharlaşan akışkan kondensere doğru hareket eder ve kondenserde yoğuşarak çevrimi tamamlar. Bu çalışmada, tasarlanan ısı borulu soğutma sistemi CPU üzerine oturtulan bakır bir blok, blok içinde 6 adet dairesel kanal ve birbirinden bağımsız olarak çalışan ısı borularından oluşmaktadır. Soğutucu akışkan olarak $NH_3$, R–22 ve R-134a soğutucu akışkanları seçilmiştir. Her akışkan için beş farklı film sıcaklığı kullanılmıştır. CPU’nun soğutulmasında en etkin soğutucu akışkanın R–22 olduğu hesaplamalar sonucunda belirlenmiştir.
  • [ X ]
    Öğe
    Second law analysis and heat transfer in a cross-flow heat exchanger with a new winglet-type vortex generator
    (Elsevier Ltd, 2010) Kotcioğlu, İsak; Çalışkan, Sinan; Cansız, Ahmet; Başkaya, Şenol
    In this paper a second law analysis of a cross-flow heat exchanger (HX) is studied in the presence of a balance between the entropy generation due to heat transfer and fluid friction. The entropy generation in a cross-flow HX with a new winglet-type convergent-divergent longitudinal vortex generator (CDLVG) is investigated. Optimization of HX channel geometry and effect of design parameters regarding the overall system performance are presented. For the HX flow lengths and CDLVGs the optimization model was developed on the basis of the entropy generation minimization (EGM). It was found that increasing the cross-flow fluid velocity enhances the heat transfer rate and reduces the heat transfer irreversibility. The test results demonstrate that the CDLVGs are potential candidate procedure to improve the disorderly mixing in channel flows of the cross-flow type HX for large values of the Reynolds number. © 2010 Elsevier Ltd.
  • [ X ]
    Öğe
    Sizing problem for a cross flow heat exchanger with wing-type vortex generator
    (2009) Kotcioğlu, İsak; Çalışkan, Sinan; Özdemir, Veysel; Başkaya, Şenol
    In the present study, sizing of a single pass cross flow heat exchanger with unmixed fluid streams has been investigated. The heat exchanger is a cross flow heat exchanger. It has overall dimensions of 20 × 20 × 20 cm. Two the most common heat exchanger design problems are the rating and sizing problem. Sizing problems deal with designing an exchanger and determining its physical size to meet the specified heat duty, pressure drops and other considerations. It means the determination of the exchanger construction type, flow arrangement, heat transfer surface geometries and materials, and the physical sizes of an exchanger to meet specified heat transfer and pressure drop. In this study, the physical size (length, width, height, mass flow rates of both fluids and surface areas on each side of the exchanger) are determined. Inputs to the sizing problem are surface geometries, fluid mass flow rates, inlet and outlet fluid temperatures and pressure drop on each side. Dimensions of L a , L b , and L c for the selected surfaces were investigated such that the design meets the heat duty and pressure drops on both sides exactly. © 2009 Springer-Verlag.
  • [ X ]
    Öğe
    Transient turbulent flow and heat transfer phenomena in plate-fin type cross-flow heat exchanger
    (2011) Kotcioğlu, İsak; Cansız, Ahmet; Çalışkan, Sinan; Başkaya, Şenol
    In this article, a transient performance of a plate-fin cross-flow heat exchanger with convergent-divergent longitudinal vortex generators is investigated. The effect of flow geometry is taken into account to analyze the transient forced convection heat transfer in a designed heat exchanger. The time-dependent Nusselt number and dissipation energy criterion are experimentally measured in 4- and 8-kW heater powers for various Reynolds numbers between 42,000 and 60,000 for the hot and cold fluids. In order to present the quality of the heat exchanger, the general empirical equations of the time-dependent Nusselt number and friction factor were derived as a function of the Reynolds number corresponding to fin geometry parameters. Following this, the transient behavior of the heat exchanger according to the change in the inlet and outlet temperatures of the hot and cold fluids was analyzed. The results showed that the variations of the time-dependent dissipation energy criterion increase with the increase in the Reynolds number. The appropriate correlations are proposed to predict the heat transfer and friction characteristics of the transient performance for the presented configuration, which indicates the designed heat exchanger has good heat conduction. Copyright © Taylor and Francis Group, LLC.