Yazar "Calisir, Tamer" seçeneğine göre listele

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    Experimental and numerical investigation of flow field and heat transfer from electronic components in a rectangular channel with an impinging jet
    (E D P Sciences, 2015) Calisir, Tamer; Koseoglu, M. Fevzi; Kılıç, Mustafa; Başkaya, Şenol
    Thermal control of electronic components is a continuously emerging problem as power loads keep increasing. The present study is mainly focused on experimental and numerical investigation of impinging jet cooling of 18 (3 x 6 array) flash mounted electronic components under a constant heat flux condition inside a rectangular channel in which air, following impingement, is forced to exit in a single direction along the channel formed by the jet orifice plate and impingement plate. Copper blocks represent heat dissipating electronic components. Inlet flow velocities to the channel were measured by using a Laser Doppler Anemometer (LDA) system. Flow field observations were performed using a Particle Image Velocimetry (PIV) and thermocouples were used for temperature measurements. Experiments and simulations were conducted for Re 4000 8000 at fixed value of H 10 x D-h. Flow field results were presented and heat transfer results were interpreted using the flow measurement observations. Numerical results were validated with experimental data and it was observed that the results arc in agreement with the experiments.
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    EXPERIMENTAL AND NUMERICAL INVESTIGATION OF VORTEX PROMOTER EFFECTS ON HEAT TRANSFER FROM HEATED ELECTRONIC COMPONENTS IN A RECTANGULAR CHANNEL WITH AN IMPINGING JET
    (Begell House Inc, 2017) Kılıç, Mustafa; Calisir, Tamer; Başkaya, Şenol
    Thermal control of electronic components is a continuously emerging problem as power loads keep increasing. In this study effects of vortex promoter on cooling 18 flash-mounted electronic components, which have constant heat fluxes, inside a rectangular channel, consisting of one open and three blocked sides were investigated experimentally and numerically by using a single jet flow. Copper blocks were used as electronic components. Flow velocities at the inlet to the channel were measured by using a Laser Doppler Anemometer (LDA) system. Temperature measurements were performed by using thermocouples. In order to improve heat transfer from electronic components, effects of vortex promoter parameters ( length, location, number, and angular position) on heat transfer were investigated for a Reynolds number of Re = 8000, heat flux q = 1000 W/m(2), and the ratio of the jet-to-plate distance to hydraulic diameter of a nozzle H/D-h = 6. The local and mean Nu numbers were determined as a function of the ratio of distance between vortex promoter and jet inlet to hydraulic diameter of jet inlet (N/D-h) in the range 0.55-5.0, the ratio of vortex promoter's length to channel height (K/H) in the range 0.5-0.9, the ratio of the distance between two vortex promoters to channel height (W/H) in the range 0.5- 1.5, and the angle of vortex promoter. in the range (-5(o)-(+45(o)).The low-Reynolds number k- epsilon turbulence model was used in numerical investigations. The heat transfer rate for N/D-h = 0.7- 5.0 improved when the vortex promoter approached the jet entrance. It was observed that heat transfer is sensitive to the location, length, and angular position of the vortex promoter.
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    Experimental and numerical study of heat transfer from a heated flat plate in a rectangular channel with an impinging air jet
    (Springer Heidelberg, 2017) Kılıç, Mustafa; Calisir, Tamer; Başkaya, Şenol
    Thermal control of electronic components is a continuously emerging problem as power loads keep increasing. To solve these thermal problems impinging jets are generally used in engineering, science and industry for its good heat transfer performance. In this study; cooling of a flat plate under constant heat flux condition, inside a rectangular channel, consisting of one open and three blocked sides was experimentally and numerically investigated using a single air jet flow. The impingement surface was a copper plate of the same width as the jet nozzle. Inlet flow velocities were measured using a Laser Doppler Anemometer (LDA) system. Temperature measurements were performed using thermocouples. Local and mean Nu numbers were determined as a function of two parameters, (a) Jet-to-plate distance (H/D (h)) in the range of 4-10 and (b) Reynolds number based on the hydraulic diameter of the slot nozzle in the range of 4000-10,000 (corresponding to an exit jet velocity from 6.5 to 16.2 m/s). Numerical investigation was also performed. Low Re number k-epsilon turbulence model was used during investigations. The results are presented in the form of graphs showing the variation of the local Nusselt number as a function of these parameters. The effect of Re number on local Nu number was examined for qaEuro(3) = 1000 W/m(2) and H/D (h) = 6. In general, it was observed that heat transfer is sensitive to the Reynolds number and increases with increasing Re number. Average Nusselt number increases of 49.5 % from Re = 4000 to Re = 10000. Effect of H/D (h) on heat transfer under impinging air jets was examined with local Nusselt numbers. Local Nusselt number was less sensitive to H/D (h) in the range of H/D (h) = 4-10. Average Nusselt number decreases of 17.9 % from H/D (h) = 4 to H/D (h) = 10. The highest average Nu number was achieved for Re = 10,000 and H/D (h) = 4. The numerical results agreed well with the experimental data, including local and average Nusselt numbers. Correlations are proposed to predict the local Nusselt number as a function of Re number and H/D (h.).
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    Numerical investigation of enhancing mixed convection heat transfer by using semi- cylindrical obstacles in a vertical channel
    (Gazi Univ, Fac Engineering Architecture, 2023) Ozdemir, Sedat; Kılıç, Mustafa; Calisir, Tamer; Başkaya, Şenol
    Purpose:In this study, it was aimed to numerically investigate the effects of the location, number and geometry of obstacles in a vertical channel on mixed convection heat transfer and flow properties for water as working fluid under different Re and Gr numbers.Theory and Methods:The FloEFD CFD code has been employed in this study to investigate the effects of semi-cylindrical and rectangular obstacle's location, number and geometry in a vertical channel of height of H=1.8 m and width of W=0.05 m on the mixed convection heat transfer and fluid flow (Figure.A). The effect of two semi -cylindrical obstacles located one under the other, four semi-cylindrical obstacles located one under the other on opposite sides, four rectangular obstacles located one under the other on opposite sides, on heat transfer and flow properties were investigated numerically. Analysis have been made for different Re numbers, Ri numbers, blockage ratios (BR) and L/D values where water was used as working fluid. The fluid enters the channel with a constant temperature (To) and velocity (uo) from the top of the channel.Results:In the present study, it was obtained that Nu number increases with increasing distance between obstacle (L/D) and natural convection effects (Ri number). For both obstacle geometries (two semi-cylindrical and rectangular obstacles), increasing L/D ratio and Ri number causes similar effect on Nu number and enhances heat transfer. It was determined that Nu numbers obtained for semi-cylindrical obstacles are bigger than the Nu numbers of rectangular obstacles. The highest Nu number can be obtained for L/D=1 and Ri=300 for both obstacle geometries.Conclusion:The mixed convection in a vertical channel with obstacles has been investigated numerically. It was observed that Nu number increases with increasing distance between obstacle (L/D) and natural convection effects (Ri number). It can be concluded that, the study could be further continued, and the effects of new types of fluids on heat transfer and flow properties, different channel and obstacle geometries on heat transfer and flow properties could be examined.
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    Numerical investigation of flow field on ribbed surfaces using impinging jets
    (Gazi Univ, Fac Engineering Architecture, 2017) Calisir, Tamer; Caliskan, Sinan; Kılıç, Mustafa; Başkaya, Şenol
    This paper presents the numerical investigation of the flow field of triangular and square ribbed surfaces under a 7x3 rectangular array of circular impinging air jets. The effect of Re number, jet-to-plate distance (H/d) and rib geometry on fluid flow characteristics was examined. Firstly, the mathematical formulation and boundary conditions were presented and afterwards the numerical model was verified with experimental results from the literature. Velocity contours were shown and axial and radial velocity distributions were presented. Additionally, the turbulence kinetic energy distribution was shown. A separation of the jet flow occurs for square ribbed surfaces before impingement. For square ribbed surfaces the separation of the jet occurs at a higher location with increasing inlet velocity. Wall jets interact more effectively for the case of H/d=2. The velocity values of the wall jets for the case of triangular ribbed surface is therefore higher.
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    Numerical investigation of heat transfer using impinging jets on triangular and square ribbed roughened walls
    (Turkish Society for Thermal Science and Technology, 2017) Calisir, Tamer; Caliskan, Sinan; Kiliç, Mustafa; Başkaya, Şenol
    This paper presents a heat removal study on triangular and square ribbed surfaces under an array of impinging air jets. The investigation was carried out using nozzles with a 7x3 rectangular array of circular jets. The effect of Re number, jet-to-plate distance, and rib arrangement on heat transfer and fluid flow characteristics was examined numerically. Two arrangements have been studied. Arrangement A considers the situation when the cooling jets are directed towards the ribs, while arrangement B considers the situation when the jets are directed towards the centre line of the cavity between two ribs. Wall jets of neighboring jets have a stronger interaction with increasing Reynolds number. The lowest and highest local heat transfer for all rib geometries was obtained for H/d=8 and H/d=4-6, respectively. On triangular ribbed surfaces the stagnation point Nusselt number values for arrangement A are significantly higher than the stagnation point Nusselt numbers for arrangement B. © 2017 TIBTD Printed in Turkey.
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    NUMERICAL INVESTIGATION OF HEAT TRANSFER USING IMPINGING JETS ON TRIANGULAR AND SQUARE RIBBED ROUGHENED WALLS
    (Turkish Soc Thermal Sciences Technology, 2017) Calisir, Tamer; Caliskan, Sinan; Kılıç, Mustafa; Başkaya, Şenol
    This paper presents a heat removal study on triangular and square ribbed surfaces under an array of impinging air jets. The investigation was carried out using nozzles with a 7x3 rectangular array of circular jets. The effect of Re number, jet-to-plate distance, and rib arrangement on heat transfer and fluid flow characteristics was examined numerically. Two arrangements have been studied. Arrangement A considers the situation when the cooling jets are directed towards the ribs, while arrangement B considers the situation when the jets are directed towards the centre line of the cavity between two ribs. Wall jets of neighboring jets have a stronger interaction with increasing Reynolds number. The lowest and highest local heat transfer for all rib geometries was obtained for H/d=8 and H/d=4-6, respectively. On triangular ribbed surfaces the stagnation point Nusselt number values for arrangement A are significantly higher than the stagnation point Nusselt numbers for arrangement B.