Browsing by Author "Budakli, M."

Now showing 1 - 5 of 5

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An experimental and theoretical analysis of vapor-to-liquid phase change on microstructured surfaces
(Elsevier, 2020-09) Budakli, M.; Salem, T. K.; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet
In this work, an experimental and a theoretical study was carried out on condensation heat transfer on vertically aligned bare unstructured, micro V-grooved and square-grooved copper substrates. During the experiments, dropwise condensation and drop-film-wise condensation modes were achieved. The surface wettability was recorded by using a high-speed camera, while the overall thermal performance has been evaluated through determining heat flux and heat transfer coefficients. Experimental results show that although the condensation surface area increased by 50% utilizing micro-grooves, the thermal performance is approximately 30% lower than the unstructured surface. Additionally, experimentally measured data has been compared with two correlations for filmwise condensation and one correlation proposed for dropwise condensation as classical benchmarks found in open literature. The comparison for the unstructured surface on which dropwise condensation has been visually monitored reveals that the benchmark for dropwise condensation agrees well for the subcooling ranging between 7.5-10 K and 35-40 K. Beyond this range, the correlation either overestimates or underpredicts the heat flux values. Two other correlations show similar trend but exhibit weak agreement with the experimental data. In case of microstructured surfaces, predictions of correlations for filmwise condensation are found to be the best for square-grooved surface than for V-grooved surface. Furthermore, new correlations have been proposed for all three surfaces based on the experimental data obtained in the present study. The proposed correlations show rather a good agreement for the unstructured surface over the full range of sub-cooling, while for those developed for microstructured surfaces, accordance up to 93-95% has been reached.
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Impact of functional nanofluid coolant on radiator performance
(ASME, 2019-08) Salem, T. K.; Nazzal, I. T.; Arık, Mehmet; Budakli, M.; Mechanical Engineering; ARIK, Mehmet
While a number of liquids are preferred in many heating and cooling applications, their thermal capacity can be a limiting factor in many thermal systems. Therefore, a series of methods such as use of mixtures of two or more fluids, emulsions, phase change materials, and more recently nanoparticle enriched fluids have been proposed. The impact of adding aluminum and copper nanoparticles to water in a closed-loop radiator has been investigated analytically and numerically. Heat transfer performances of different working fluids are studied under the same boundary conditions. The analytical and numerical models including external and internal flow domains of the radiator have been developed, and free convection air cooling has been considered over external surfaces of a radiator. Both plain and nanoparticle added fluid cases are analyzed individually to differentiate the impact over heat transfer. The results indicate that the presence of nanoparticles effectively raised the convective heat transfer coefficient and thus the performance of the radiator system increased by 2.1% and 0.6%, respectively, in comparison to plain water operating condition. Furthermore, the radiator tube length has been shortened by 2.0% and 0.75% for both Al and Cu nanoparticle filled fluid, respectively, to obtain the same thermal performance at a single tube. The total required heat transfer surface area is also reduced by 2.0% and 1.15% for Al and Cu, respectively. Finally, a comparison between analytical and numerical models has been found to be in a good agreement of heat transfer coefficient and Nusselt number.
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Numerical and experimental analysis of a heat-pipe-embedded printed circuit board for solid state lighting applications
(Taylor & Francis, 2019-01-02) Salem, Thamer Khalif; Khosroshahi, F. S.; Arık, Mehmet; Hamdan, M. O.; Budakli, M.; Mechanical Engineering; ARIK, Mehmet; Salem, Thamer Khalif
Thermal management is one of the main issues for electronics cooling especially for tightly packaged PCBs that experience local heat generation. Thus, theoretical and experimental investigations have been conducted to predict thermal performance of a novel heat-pipe-embedded-PCB. First, plain heat-pipe is experimentally tested under various inclination angles and validated by theoretical and numerical calculations. Flattened heat-pipes have been embedded into PCB prototypes made of polymer and aluminum and have been tested for similar experimental parameters; they have shown a decrease in compared with conventional heat pipe. Accordingly, reduction of approximately 50% is achieved for both embedded PCB prototypes.
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Rapid heating and cooling chamber for a photonics junction measurement system
(IEEE, 2020) Tarçın, Hüseyin Gökberk; Saygın, Alper; Muslu, Ahmet Mete; Budakli, M.; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet; Tarçın, Hüseyin Gökberk; Saygın, Alper; Muslu, Ahmet Mete
Since many industrial applications require heat treatment processes or validation tests under certain ambient temperatures, thermal design is a key issue to be considered in order to ensure fast heating and cooling capabilities. Although most industrial furnaces provide the required isothermal conditions for various test applications or calibrations, a number of them does not provide rapid heating and cooling inside a closed system and the thermal equilibrium over different regions of the system are not satisfied as intended. This brings a number of challenges for the performance test of most electronics, which are affected by ambient temperatures, such as LEDs, lasers and transistors. Particularly, a test environment that can quickly and accurately adjust a uniformly distributed isothermal domain can be useful for many electronic components in order to test their performance at preselected ambient temperatures. In such systems, the design parameters have to be adjusted depending on the desired conditions. In fact, the design of those systems has to be planned in detail to achieve a system working fast and accurate, which shall contribute to reduction in operating time. Therefore, this study focuses on proposing a new approach to the development of a high-performance and high-resolution heating and cooling chamber used in a junction temperature measurement of light emitting diodes (LEDs). The major objective thereby is to achieve high heating and cooling rates of a controlled chamber that satisfies thermal conditions at a user defined temperature interval between 20°C and 80°C. Therefore, material properties and geometrical dimensions, power requirements and cooling performances of the chamber are analyzed as major design parameters. Numerical models are created for various design options, and simulations are performed for various working conditions under certain design constraints. The relationships between design parameters are determined. A final design is propos...
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Spreading behavior of droplets impacting over substrates with varying surface topographies
(Elsevier, 2020-12-05) Cetiner, A.; Evren, B.; Budakli, M.; Arık, Mehmet; Ozbek, A.; Mechanical Engineering; ARIK, Mehmet
Droplet interaction with solid surface plays an important role in a number of practical applications such as thermal management systems, steel production, painting, prevention of impurit deposition, and formation of corrosion. In this study, droplet impact on different surface topographies was experimentally investigated. A major part of this work was to devoted to developing supherhydrophobic surfaces using a combination of two conventional manufacturing techniques in order to study the droplet dynamics with the aim of preventing liquid attachement at the wall. Five surfaces were manufactured for which the methods such as mechanical polishing, Ylaser-ablation, anodization, superhydrophobic spray-coating, and combination of laser-ablation and anodization were applied. Deionized water was used as the working liquid. The effects of velocity and surface temperature on spreading dynamics were investigated by impacting single droplets for Weber numbers between 67 and 565. Experiments are performed at 25 degrees C ambient temperature with a constant droplet temperature of 25 degrees C, while the effect of surface temperature has been studied for 25 degrees C and 2 degrees C. Maximum spreading factor data was obtained and compared with theoretical models and experimental data found in the literature. Through the combination of laser-ablation and anodization methods, superhydrophobicty is obtained with static contact angles similar to that measured on the superhydrophobic coating. Experiments at 25 degrees C surface temperature show that the droplet impacting on the combined surface had greater maximum spreading factor values than only laser-ablated and anodized surfaces and lower than those determined at the cotaed surface. At low surface temperature, the smallest maximum spreading factor was measured at the substrate with its surface treated by the combined method. The mathematical models found in literature show a good agreement concerning the maximum spreading factor values determined at the polished, anodized and laser-ablated surfaces. However, the maximum spreading factor at both spray-coated and combined surfaces is larger than the model predictions.