Investigation of mixed convection heat transfer in a horizontal channel with discrete heat sources at the top and at the bottom

Doğan, Ayla; Sivrioğlu, Mecit; Baskaya, Senol

doi:10.1016/j.ijheatmasstransfer.2006.01.005

Cited by 43 publications

(19 citation statements)

References 29 publications

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“…İletim kayıplarının sisteme verilen toplam enerjinin yaklaşık olarak %14'ünü geçmediği görülmüştür. Test bölgesinde köpük ısı alıcılar olmadan, bakır plaka yüzeylerinden radyasyonla olan ısı kayıpları Doğan ve arkadaşlarının [11] yapmış olduğu detaylı çalışmadaki yöntemle hesaplanmıştır. Bu durumda, radyasyon kayıplarının sisteme verilen toplam ısının %5 ini geçmediği görülmüştür.…”

Section: Teori̇ (Theory)unclassified

“…Elde ettikleri sonuçlarda, köpük blok olmayan düz bir kanala göre, köpük bloklar yerleştirilmiş kanalda ısı transferinin %300 daha fazla olduğunu belirlemişlerdir. Doğan ve arkadaşları yapmış oldukları çalışmada yatay bir kanalın alt ve üst kısmına gömülü olarak yerleştirdikleri ayrık ısıtıcılardan karışık taşınımla gerçekleşen ısı transferini deneysel olarak incelemişlerdir [11]. Bae ve arkadaşları [12] içerisinde gözenekli bloklar olan bir kanalda karışık taşınım şartlarında ısı transferini sayısal olarak modellemişlerdir.…”

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Alüminyum Köpük Isı Alıcılardan Taşınımla Isı Transferinin Deneysel Olarak İncelenmesi

Doğan¹,

Öney²

2014

Gazi Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi

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ÖZETBu çalışmada, yüzeyleri 10 PPI (Inch Başına Gözenek) lık alüminyum köpük ısı alıcılarla genişletilmiş ısı kaynakları bulunan yatay bir kanalda taşınımla gerçekleşen ısı transferi deneysel olarak incelenmiştir. Çalışma akışkanı olarak hava kullanılmıştır. Elektronik eleman performansına etkilerini araştırmak için alüminyum köpük ısı alıcılar dikdörtgen kesitli kanal içerisinde bulunan bakır ısıtıcılar üzerine ayrık formda yerleştirilmiştir. Kanalın alt yüzeyine 8x2 diziliminde yerleştirilmiş alüminyum köpük ısı alıcılar sabit ısı akısına maruz bırakılmışlardır. Kanalın yan, alt ve üst duvarları yalıtılmıştır. Deneyler Reynolds sayısının 531≤Re Dh ≤4486 (laminer ve türbülanslı akış için), düzeltilmiş Grashof sayısının Gr * Dh =4,2x10ve Richardson sayısının Ri=0,008-1,5 aralığındaki değerleri için yapılmıştır. Deneylerden elde edilen ölçümlerden, Nusselt sayısı dağılımları farklı Reynolds ve farklı Grashof sayıları için elde edilmiştir. Düşük gözenek yoğunluğuna sahip olan alüminyum köpük ısı alıcılar, içerisinden yoğun hava geçirme özelliğinden dolayı ısı transferini önemli ölçüde artırmaktadır. Yapılan karşılaştırmalar sonucunda, kanal içerisinde 10 PPI alüminyum köpük ısı alıcıların kullanılması durumunda, köpük ısı alıcılar kullanılmadan elde edilen sonuçlara göre yaklaşık olarak %36 ila %70 daha fazla ısı transferi sağlanmıştır.Anahtar kelimeler: Alüminyum köpük ısı alıcıları, elektronik soğutma, kanal akışı EXPERIMENTAL INVESTIGATION OF CONVECTION HEAT TRANSFER FROM ALUMINUM FOAM HEAT SINKS ABSTRACTIn the present study, convection heat transfer from arrays of heat sources extended by 10 PPI (Pore Per Inch) opencell aluminum foam heat sinks inside a horizontal channel has been investigated experimentally. Air was used as the working fluid. Aluminum foams have been placed on discrete copper blocks in a rectangular channel in order to investigate the effect of aluminum foams on electronic equipments performance. The lower surface of the channel was equipped with 8x2 array of aluminum foam heat sinks subjected to uniform heat flux. Sidewalls, the lower and upper walls were insulated. The experimental study was made for Reynolds numbers 531≤Re Dh ≤4486 (for laminar and turbulent flow), modified Grashof numbers Gr and Richardson numbers Ri=0,008 to 1,5. From the experimental measurements, distributions of Nusselt number were calculated for different Reynolds and Grashof numbers. It is found that heat transfer rate is substantially increased by employing aluminum foam heat sinks with low pore density due to relatively intense air through the aluminum foam heat sinks. As a result of comparisons, using of 10 PPI aluminum foam heat sinks increases the heat transfer rate in the channel between approximately 36% and 70% compared to the rate obtained without the foam heat sinks in a channel.

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Section: Teori̇ (Theory)unclassified

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Alüminyum Köpük Isı Alıcılardan Taşınımla Isı Transferinin Deneysel Olarak İncelenmesi

Doğan¹,

Öney²

2014

Gazi Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi

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“…Use of discrete heater is also seemed to be of great interest to researchers now-a-days. Dogan et al [2] and Muftuoglu and Bilgen [3] used discrete heaters in their studies. However, Dogan et al [2] experimentally investigated mixed convection in a horizontal channel having arrays of discrete heater and also studied the effect of aspect ratio (AR=2, 4 and 10) at various Re and Gr.…”

Section: Introductionmentioning

confidence: 99%

“…Dogan et al [2] and Muftuoglu and Bilgen [3] used discrete heaters in their studies. However, Dogan et al [2] experimentally investigated mixed convection in a horizontal channel having arrays of discrete heater and also studied the effect of aspect ratio (AR=2, 4 and 10) at various Re and Gr. Muftuoglu and Bilgen [3] investigated the positions of discrete heaters where optimum heat transfer occurs and found that when the discrete heaters are placed closer to the bottom the best thermal performance is obtained.…”

Section: Introductionmentioning

confidence: 99%

A Computational Study on Mixed Convection Heat Transfer in an Inclined Rectangular Channel under Imposed Local Flow Modulation

et al. 2017

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Numerical investigation of mixed convection heat transfer in an inclined 2D rectangular channel provided with partially heated bottom wall and a constant low temperature upper wall has been performed. The heated section of the bottom wall i.e. the heaters are maintained with constant heat flux and separated from each other by adiabatic segments. A fully developed parabolic velocity profile at constant low temperature is induced at the inlet. To enhance the heat transfer from the heaters, local flow field in the channel is modulated by placing circular cylinders rotating in counterclockwise direction (aiding flow) above each heater along the channel centerline. The fluid and the thermal fields within the rectangular channel are governed by the two-dimensional Navier-Stokes and Energy equations that have been solved by adapting Galerkin finite element method. The governing parameters of the present problem such as Reynolds number (Re) and Grashof number (Gr) are varied in the range of 1 ≤ Re ≤ 100 and 10 3 ≤ Gr ≤ 10 5. Air has been considered as working fluid having a Prandtl number, Pr = 0.71. In addition to these governing parameters, the inclination angle of the channel (α) and the speed ratio (ξ) that is the ratio of peripheral speed of the rotating cylinder and the maximum inlet flow velocity is also varied in the range of 0° ≤ α ≤ 90° and 0.5 ≤ ξ ≤ 2.0 respectively. The thermal and the fluid fields are visualized via the isotherm and the streamline plots. The efficacy of local flow modulation with rotating cylinder for heat transfer enhancement has been estimated in terms of normalized average Nusselt number over the heaters as Nu/Nu nc , where Nu and Nu nc represents the average Nusselt number with and without flow modulation respectively. Results obtain in the present study reveals that, for very weak flow (Re = 1), flow modulation results in lower heat transfer particularly at lower values of Gr on the contrary for moderate and higher values of Re (10, 100), flow modulation has been found to result in higher heat transfer particularly at lower values of Gr. For example, at Re = 100 and α= 0°, about 32% to 55% enhancement in heat transfer has been obtained for 10 3 ≤ Gr ≤ 10 5 . Variation in heat transfer enhancement through flow modulation has also been noticed for different channel inclination angle (α) for various system configurations.

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“…In this kind of system, an important number of investigations have been performed experimentally [1][2][3] and numerically [4][5][6]. The literature review shows that the case when the blocks are heating with constant temperature (isothermal model) was considered in several studies including forced [3], natural [4] and mixed [6] convection.…”

Section: Introductionmentioning

confidence: 99%

The limits of isothermal model validity in the case of natural convection cooling of heating blocks in a horizontal channel

Mouhtadi

Amahmid

Hasnaoui

et al. 2012

MATEC Web of Conferences

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Abstract. Numerical simulations are conducted to study natural convection in a horizontal channel provided with heating blocks mounted on its lower wall. The blocks are submitted to a uniform heat generation and the channel upper surface is maintained at a cold constant temperature. The main objective of this study is to examine the validity of the model with isothermal blocks for the system under consideration. The controlling parameters of the present problem are the thermal conductivity ratio of the solid block and the fluid (0.1 ≤ * = ≤ 200) and the Rayleigh number (10 4 ≤ ≤ 10 7 ). The validity of the isothermal model is examined for various Ra by using different criteria based on local and mean heat transfer characteristics.

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Investigation of mixed convection heat transfer in a horizontal channel with discrete heat sources at the top and at the bottom

Cited by 43 publications

References 29 publications

Alüminyum Köpük Isı Alıcılardan Taşınımla Isı Transferinin Deneysel Olarak İncelenmesi

Alüminyum Köpük Isı Alıcılardan Taşınımla Isı Transferinin Deneysel Olarak İncelenmesi

A Computational Study on Mixed Convection Heat Transfer in an Inclined Rectangular Channel under Imposed Local Flow Modulation

The limits of isothermal model validity in the case of natural convection cooling of heating blocks in a horizontal channel

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