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In this present study, free convection from an in-line 5x1 array of aluminum foam heat sinks which were placed on the bottom wall of the inclined rectangular channel was investigated. Aluminum foam heat sinks were made of Al-6101 alloy. All heat sinks mounted on a bottom wall of the channel was discrete form and exposed to uniform heat flux. Aluminum foam materials with three different pore densities (10, 20 and 40 PPI) were used in experiments. Air was used as coolant fluid (Pr =0.7). The experiments were made for Rayleigh Number range from 2.03 x10 7 to 1.33 x10 8 and the channel inclination angles were varied from 0° to 90°. Moreover, the heat transfer results from the aluminum foam heat sinks were also compared to the results obtained for foam-free (without foam) surfaces. The results showed that both the channel inclination angle and the usage of foam heat sinks are significant influences on heat transfer results.Özet. Bu çalışmada, eğimli dikdörtgen bir kanalda, 5x1diziliminde alüminyumdan yapılmış köpük ısı alıcılarından doğal taşınımla ısı transferi incelenmiştir. Alüminyum köpük ısı alıcılar Al-6101 alaşımında yapılmıştır. Kanalın alt duvarına monte edilen bütün ısı alıcılar ayrık formda yerleştirilmiş ve sabit ısı akısına maruz bırakılmıştır. Deneylerde farklı gözenek yoğunluğuna sahip (10, 20 ve 40 PPI) metal köpük malzemeler kullanılmıştır. Soğutma akışkanı olarak hava (Pr =0.7) kullanılmıştır. Deneyler Rayleigh sayısının 2.03 x10 7 ila 1.33 x10 8 arasındaki değerleri ve kanal eğim açısı 0° ila 90° arasında değişen değerleri için yapılmıştır. Ayrıca, alüminyum köpük ısı alıcılardan elde edilen ısı transferi sonuçları düz yüzeyler (köpük olmayan) için elde edilen sonuçlarla karşılaştırılmıştır. Elde edilen sonuçlar, hem kanal eğim açısının ve hem de köpük ısı alıcıların kullanılmasının, ısı transfer sonuçları üzerinde önemli etkileri olduğunu göstermiştir.Anahtar Kelimeler: Serbest taşınım, köpük ısı alıcı, elektronik soğutma, eğimli kanal.

The thermal management of electronic devices has become a major problem in recent years. Therefore, there is a growing need for research on many new materials and innovative fluids due to the developing technology and increasing cooling need in electronic systems. In this paper, heat transfer from a plate fin and pin fin type heat sinks that were placed in a water block that are used in electronic systems was investigated. A base fluid (pure water) and 0.1% mass concentration Al2O3-H2O nanofluid were used as cooling fluids. The experiments were carried out for volumetric flow rates varying between 100 and 800 mL/min and heat flux values of 454.54 W/m2 and 1818.18 W/m2. The results demonstrated that the Al2O3-H2O nanofluid on the empty surface provided a maximum improvement of 10.5% in heat transfer compared to the base fluid. In the use of plate finned heat sink, the maximum amount of improvement in heat transfer compared to the empty surface was obtained approximately 64.25% for the base fluid and 82.8% for the nanofluid. A similar comparison was made for the pin-fin heat sink, a maximum thermal improvement of 56.4% in the base fluid and 70.27% in the use of nanofluid was determined.

With the developing technology, the dimensions of electronic systems are becoming smaller, and their performance and the amount of energy they need increases. This situation causes the electronic components to heat up more and the existing cooling systems to become inadequate. In this study, instead of the fins used in existing systems, 10 PPI and 40 PPI PHS were placed inside a water block, and the Al2O3-H2O nanofluid at a mass fraction of 0.1% was used as the cooling fluid. Experiments were carried out under constant heat flux of 454.54 W/m2 and 1818.18 W/m2, with volumetric flow rates varying between 100 mL/min and 800 mL/min. The heat transfer results were compared with the results obtained from the base fluid and the empty surface. The results showed that the nanofluid reduced the surface temperatures compared to the base fluid. Especially when PHSs were used together with the nanofluid, a significant increase in heat transfer occurred compared to the empty surface. The highest heat transfer was observed when both the nanofluid and 40 PPI PHS were used together. In addition, the highest thermal performance value was determined as 1.25 times compared to the empty surface when the nanofluid and 10 PPI PHS were used together.

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